Achieving stable human stem cell engraftment and survival in the CNS: is the future of regenerative medicine immunodeficient?

Abstract

There is potential for a variety of stem cell populations to mediate repair in the diseased or injured CNS; in some cases, this theoretical possibility has already transitioned to clinical safety testing. However, careful consideration of preclinical animal models is essential to provide an appropriate assessment of stem cell safety and efficacy, as well as the basic biological mechanisms of stem cell action. This article examines the lessons learned from early tissue, organ and hematopoietic grafting, the early assumptions of the stem cell and CNS fields with regard to immunoprivilege, and the history of success in stem cell transplantation into the CNS. Finally, we discuss strategies in the selection of animal models to maximize the predictive validity of preclinical safety and efficacy studies.

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!"#$"%
ISSN 1746-075110.2217/RME.11.22 © 2011 Future Medicine Ltd
Regen. Med. (2011) 6(3), 367–406
Achieving stable human stem cell engraftment and
survival in the CNS: is the future of regenerative
medicine immunodeficient?
Stem cell treatments for neurological
disease and injury: animal models
The loss of cells of the CNS is a hallmark of
neurological disorders and traumatic neural
injury, such as Parkinson’s disease, Huntington’s
disease, Alzheimer’s disease, multiple sclerosis,
amyotropic lateral sclerosis, spinal cord injury
(SCI), traumatic brain injury and stroke.
Currently, there are very few therapeutic inter-
ventions to ameliorate these conditions in the
human patient population. However, stem cell
therapy has potential to provide methods of
repairing, regenerating or protecting the dam-
aged CNS. Successful efficacy using human stem
cells in animal models has already led to multiple
human clinical trials [1–3], which have been spon-
sored by several sources (Geron, StemCells, Inc.,
and Advanced Cell Technology).
A stem cell is a cell that possesses the abil-
ity to both self-renew and differentiate into
multiple cell types. Embryonic stem cells are
pluripotent, capable of differentiating into all
cell types of the body [4]. Recent advances in
the stem cell field have resulted in the develop-
ment of induced pluripotent stem cells repro-
grammed from somatic cells, which have been
shown to have a remarkably similar fate potential
to embryonic stem cells [5]. Proceeding down
the lineage tree of development, later stem cell
populations become more restricted to the tissue
from which the cells were derived. For example,
neural stem cells of the CNS have a restricted
fate potential and are capable of only differenti-
ating into neurons and glia [6]. For the purposes
of our review of the neurological disease and
injury literature (TABLES 1–11), we will focus on
human embryonic, fetal and adult-derived cells,
in particular highlighting the issues associated
with neurotransplantation of these populations.
Transplantation of stem cells into the dis-
eased or injured CNS allows a unique replace-
ment therapy not afforded by pharmacological
therapeutics. Stem cells can provide benefit by
differentiating and integrating into the host to
restore functional and behavioral deficits that
result from the loss of host CNS cells [2,7,8].
However, stem cells can also provide trophic
support or deficient factors to the host tissue,
reducing cell loss or potentially promoting host
regeneration/plasticity mechanisms to restore
function [9,10]. In some cases, the benefits of
stem cell transplantation may derive from the
short-term neurotrophic/neuroprotective effects
during the acute phase postinjury/transplanta-
tion. However, the risk:benefit ratio of a cellular
therapeutic that is neurotrophic/neuroprotective
in nature in a human clinical population may
not be advantageous due to increased risk fac-
tors to the patient deriving from this method of
delivery. These may include tumorigenesis and
graft rejection. This is especially true when alter-
natives that offer similar mechanistic recovery
are available, such as conditioned media, neu-
tralizing antibodies, or neuroprotective phar-
macological approaches. Thus, we focus here
on mechanisms of action in which long-term
stem cell engraftment and survival are of critical
importance to the regenerative medicine field.
There is potential for a variety of stem cell populations to mediate repair in the diseased or injured CNS;
in some cases, this theoretical possibility has already transitioned to clinical safety testing. However, careful
consideration of preclinical animal models is essential to provide an appropriate assessment of stem cell
safety and efficacy, as well as the basic biological mechanisms of stem cell action. This article examines
the lessons learned from early tissue, organ and hematopoietic grafting, the early assumptions of the
stem cell and CNS fields with regard to immunoprivilege, and the history of success in stem cell transplantation
into the CNS. Finally, we discuss strategies in the selection of animal models to maximize the predictive
validity of preclinical safety and efficacy studies.
KEYWORDS: clinical translation ? engraftment ? human stem cells ? immunodeficient
? immunosuppression ? neurological disease ? neurotrauma ? regenerative medicine
? stereology ? transplantation ? xenograft
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Anderson, Haus, Hooshmand, Perez, Sontag & Cummings
The goal of this review is to broadly look at
the role of the choice of animal models in test-
ing proof of concept and safety for the clinical
translation of stem cell transplantation strate-
gies, with a particular focus on the CNS. We
discuss the available animal model systems for
stem cell transplantation into the diseased or
injured CNS, identify and discuss key criteria
for engraftment and cell survival that should
be considered in the experimental setting in
the evaluation of efficacy and/or safety studies,
and review a brief history of the animal models
selected by different arms of the regenerative
medicine field. Finally, we review the existing
CNS stem cell transplantation literature in the
context of cell engraftment and survival criteria,
summarizing findings in the field of regenera-
tive medicine and addressing the critical need for
more refined criteria of success in animal models
utilizing xenotransplants.
Transplantation paradigm &
predictive preclinical models
The success of laboratory and clinical
transplantation is largely defined by the immu-
nological compatibility between donor and host
tissue/cells. Autografts are transplants where the
donor tissue comes from the recipient. A com-
mon example of an autograft is when skin or
bone is taken from one part of a patient’s body to
reconstruct another [11]. Syngeneic transplants, or
isografts, are those in which the donor and recipi-
ent are either genetically identical or sufficiently
identical to allow for complete immunological
compatibility. An example of syngeneic graft is
a kidney transplant between identical twins [12].
Allografts are transplants where the donor and
recipient are nongenetically identical members
of the same species. Differences in MHC anti-
gens, specifically HLA in humans, determine
the successful integration of the graft. In the
clinical setting this is a complicated issue, as
HLA/androgen-binding proteins match strin-
gency can be dependent on the organ/tissue
transplanted. However, it is known from organ
transplant research that MHC matches, or near
matches, reduce the likelihood of graft rejection
[13]. Regardless of the level of histo compatibility,
immunosuppression is required to overcome
the immune response against alloantigens.
Finally, a xenograft is a transplant in which the
donor and recipient are from different species.
Transplantation between closely related species,
such as mice and rats, is classified as a concordant
xenograft. Transplantation between distantly
related species, such as humans and rodents, is
Table 1. Analysis of 132 unique papers reporting xenotransplantation of human stem cells into the CNS.

Normal brain (n = 6 papers)
Acute/traumatic (n = 94 papers‡)
Chronic/atraumatic (n = 32 papers)
IC with IS
IC with no IS
ID model
IC with IS
IC with no IS
ID model
IC with IS
IC with no IS
ID model
Total number of papers
3
2
1
45
37
14
21
7
4
Number reporting animals
engrafted (%)
3
0
1
12
7
9
6
4
1
Number reporting cell survival (%)
2
1
1†
9
1
4
6
2
1
Number reporting engraftment
and survival
2
0
1
1
0
4
1
1
1
Number reporting neither
0
1
0
28
30
5
9
2
3
Average number of animals
engrafted (%)
78 (n = 3)
NR
100 (n = 1)
85 (n = 12)
71 (n = 7)
95 (n = 9)
81 (n = 6)
89 (n = 4)
87 (n = 1)
Average cell survival (%)
53 (n = 2)
8 (n = 1)
NA†
17 (n = 9)
35 (n = 1)
263 (n = 4)
83 (n = 6)
34 (n = 2)
NA§
†One immunodeficient paper reported a 10% cell survival via bioluminescence, but detection sensitivity is not comparable to histology.
‡94 unique papers, one of which includes IC animals with and without IS, and one includes IC animals in one group and ID animals in another group. These duplications are subtracted from the total.
Hence, 45 + 37 + 14 = 96 – 2 = 94.
§One paper quantified survival stereologically within a restricted region while cells had migrated beyond that region, hence total cell survival is unknown.
IC: Immunocompetent; ID: Immunodeficient; IS: Immunosuppression; NA: Not applicable; NR: Not reported.

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Achieving stable human stem cell engraftment & survival in the CNS !"#$"%
classified as a discordant xenograft. The level of
immune response, and hence the risk of an immu-
norejection response, increases in magnitude
when moving from an autologous transplant, to
a syngeneic transplant, to a matched allograft,
to a near-matched allograft, to an unmatched
allograft, to a concordant xenograft and finally
to a discordant xenograft (FIGURE 1). Therefore,
the type of transplantation paradigm is a crucial
factor in establishing a clinically relevant model
system for stem cell therapy.
Informative model systems that have good
predictive value of the human clinical trans-
plantation setting are necessary to increase the
chances of success in translating advances in
stem cell therapy of neurological diseases from
bench to bedside. From a stem cell transplan-
tation perspective, there are two major com-
ponents of a model system: the host species in
which the neurological disease is being studied
and the host species from which the stem cells
are derived. Clearly, from both an ethical and
regulatory standpoint, human subjects are not
an appropriate starting point for testing stem
cell therapies. However, there are a wealth of
animal models that closely mimic some of the
pathological and behavioral deficits associated
with different neurological disorders and types
of neurotrauma. While some groups have per-
formed experiments in larger animal models such
as nonhuman primates [14–16], the vast majority
of preclinical research using human stem cells
is conducted in rodent models due to the lower
cost, lack of nonhuman primate models of neuro-
logical disease and injury (versus the abundance
of transgenic/knockout mice), and difficulty of
achieving adequate immunosuppressive regi-
mens in nonhuman primates. In fact, the latter
may be such a significant barrier that, in many
cases, stem cell transplantation into nonhuman
primate models cannot practically be employed
to inform clinical translation. For the purposes
of this article, we will focus on rodent models of
neurological disease and trauma.
If we accept rodent models as the basis for the
study of neurological disease/trauma, what is the
most appropriate stem cell source: human stem
cells or animal stem cells? A large advantage to
using specifically rodent stem cells for pre liminary
proof-of-concept studies is that researchers can
perform syngeneic or allotransplants, which can
bypass many of the immunological hurdles of
xenografts and more closely mimic some aspects
of the clinical setting (i.e., matched human tis-
sue grafted into a human patient). However,
while nonhuman cells can provide preliminary
proof-of-concept data, the proposed population
of human cells should be tested in preclinical
studies for regulatory submission in optimal and
appropriate animal models. Furthermore, long-
term safety data must be established using the
clinical grade of stem cells in the target tissue
and in potentially both naive and disease/injury
conditions. Consequently, there is a need in the
regenerative medicine field for preclinical model
systems with good predictive value; this need
necessitates the use of human stem cells.
In the case of a discordant xenograft, such as
human stem cells into a mouse host, the main
hurdle is avoiding or sufficiently minimizing the
rejection response by the host immune system
in order to achieve successful engraftment and
survival of the transplanted human stem cells.
Moreover, the presence of an active immuno-
rejection response itself may significantly alter the
efficacy, and critically, the safety profile of the cell
therapy candidate. In this regard, a valid assess-
ment of the safety profile can be argued to be
particularly dependent on conditions that enable
or encourage maximal theoretical engraftment
and cell survival. In the absence of maximal theo-
retical engraftment conditions, a valid ana lysis of
the tumorigenic potential of a cell therapy can-
didate may not be possible. An example of this
would be the failure to develop teratomas after
embryonic stem cell transplantation into immu-
nocompetent versus immuno deficient hosts [17,18].
By employing animal models that recapitulate
the key elements of human pathogenesis, per-
mit sensitive evaluation of disease-modifying
activity and permit successful engraftment and
long-term survival of transplanted human stem
cells, researchers can improve the predictive
validity of preclinical safety and efficacy studies,
and the likelihood of success of translation to
clinical trials.
Table 2. Proportion of papers from TABLE 1 that use immunocompetent or
immunodeficient models.
Total immunocompetent
models with
immunsuppression (%)
69 (51)
Total immunocompetent
models without
immunosuppression (%)
46 (34)
Total immunodeficient
models (%)
19 (14)

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Lessons learned from tissue, organ
& hematopoietic grafting
Recognition of the difficulty of achieving sig-
nificant long-term engraftment and survival
after transplantation is not new; by contrast,
it is an issue grounded in the history of skin
and organ grafting, which provided the foun-
dations for our understanding of immuno-
logical tolerance, as well as the trial-and-error
history of hematopoietic cell transplantation
[19,20]. Although now regarded as a clinically-
acceptable therapy for leukemia, the evolu-
tion of hematopoietic cell transplantation
spans half a century and culminates in the
conclusion that addressing the multidimen-
sionality of the immune response is critical
in order to achieve successful cell engraftment
and survival.
Human hematopoietic cell transplanta-
tion originated from a number of prelimi-
nary animal experiments that demonstrated
the importance of histocompatibility between
donor and host. Murine studies have shown
that successful engraftment of allogeneic mar-
row cells could trigger an immune reaction
against the host [21] (reviewed in [22]), now
termed graft-versus-host disease and known
to be mediated by T cells derived from donor
tissue. Critically, the severity of the immune
reaction was regulated by genetic factors [23].
Successive animal experiments revealed the
importance of histocompatibility between
donor and host tissue [24–29]. These data sug-
gested that T-lymphocyte-mediated immune
responses could be triggered as a result of
MHC mismatch. Accordingly, subsequent
experiments employing methotrexate [26] and
cyclophosphamide [30], both of which attenu-
ate T-cell responses, achieved more favorable
outcomes in animal models of bone marrow
transplantation. However, the success rate
in translating these advancements for the
treatment of human leukemias via hemato-
poietic cell transplantation remained low [31].
Conversely, hematopoietic cell transplanta-
tion in cases where patients exhibited severe
combined immunological deficiency [32–34]
resulted in high levels of engraftment, and
in some cases, patient survival for more than
25 years [35]. With the discovery of a sponta-
neous mutation in mice leading to a similar
form of severe combined immuno deficiency
(SCID) [36], efforts were undertaken to reca-
pitulate the human findings in this new mouse
model. Approximately 5 years later, Mosier
and colleagues performed the first successful
Table 3. Normal CNS: immunocompetent animals with immunosuppression.
Author
(year)
Model Paradigm Cell type
Host
species/ sex
Time
post-
injury
Final
cell
dose
IS
Quantifi-
cation
method
Groups
Final
time
point
No.
animals explanted
No.
animals
with cells
Animals
engrafted
(%)
Cell
survival
(%)
Ref.
Fricker
et al.
(1999)
Normal
adult
brain
Brain
6–9-week
fetal hNPC
Female
Sprague–
Dawley
Rats
NA
100,000 CsA
Visualization
of BrdU+ cells

2 and 6
weeks
54
54
100
NR
[137]
Kishi
et al.
(2005)
Normal
young
brain
Brain
9-week
fetal
hNSCs
8–9 week old male
C57BL6
mice
tx cells
4 days after
control or
?-estradiol
pellet
20,000
CsA
hNuc not via
stereology
4 days after
control pellet
4
weeks
6
4
67
1.0
[138]
Kishi
et al.
(2005)








4 days after
estradiol
pellet
4
weeks
6
4
67
1.0
[138]
Englund et al.
(2002)
Normal
adult
brain
Brain
9-week
fetal hNPC
Female
Sprague–
Dawley
rats
NA
150,000 CsA
Stereology
(other)
Striatum
4
weeks
24
22
92
190.0
[139]
Englund et al.
(2002)








Hippo-
campus
4
weeks
18
13
72
20.0
[139]
Englund et al.
(2002)








Sub-
ventricular zone
4
weeks
20
14
70
NR
[139]
CsA: Cyclosporine A; BrdU: Bromodeoxyuridine; hNPC: Human neural progenitor cell; hNSC: Human neural stem cell; hNuc: Human nuclear antibody; IS: Immunosuppression; NA: Not applicable; NR: Not reported;
tx: Transplantation.

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Achieving stable human stem cell engraftment & survival in the CNS !"#$"%
hematopoietic stem cell xenograft using the
recently discovered immunodeficient SCID
mouse, in which the human hematopoietic stem
cell engrafted successfully and constituted long-
term repopulation of the mouse immune system
[37]. As a result of this and later experiments using
immunodeficient models developed to target
multiple components of immuno rejection (see
later), the use of immunodeficient animals in the
field of hematopoietic stem cell transplantation
permitted increased engraftment, cell survival
and rapid advancement of knowledge in this
area [38–40].
Mechanisms of allogeneic
& xenogeneic rejection
Based in large part on work in the hemato-
poietic cell transplantation field, the role of
T lymphocytes in immunorejection has become
much better understood over the past 50 years.
T-cell activation is dependent on the recogni-
tion of MHC class I and II antigens. MHC I is
expressed on almost all cells, while MHC II is
generally expressed in association with antigen-
presenting cells (APCs), including dendritic
cells, B cells and macrophages, as well as micro-
glia and astrocytes in the CNS. MHC class I is
principally associated with CD8 cytotoxic T-cell
activation, whereas MHC class II is principally
associated with CD4 T-cell activation; both
lymphocyte subtypes participate in immuno-
rejection responses. In addition to a require-
ment for the recognition of an MHC/antigen
complex displayed by an APC by the T-cell
receptor, T-lymphocyte activation also depends
on exposure to an array of costimulatory ligands
(e.g., B7). If T-cell receptor binding to an anti-
gen/MHC complex takes place in the absence
of a costimulatory activation signal, a T-cell can
be rendered unable to respond to that antigen
(anergic), a mechanism that has been suggested
as a means of achieving tolerance [41].
Increasing evidence suggests that other
aspects of the immune system contribute to
both allogeneic and xenogenic rejection, includ-
ing natural killer (NK) cells, the complement
cascade and the lymphatic system [42–44]. In
this regard, it is not only the expression, but
also the lack of expression, of MHC I that can
invoke an immune response by NK cells [45,46].
As the immunological barrier grows, the role of
these additional mechanisms of rejection may
increase, becoming greater for xenotransplanta-
tion than in the case of allotransplantation [47].
Immunorejection in the allograft setting is pre-
dominantly mediated by the adaptive immune
Table 4. Normal CNS: immunocompetent animals with no immunosuppression.
Author
(year)
No. Class
Cell type
Host species/
sex
IC or ID
Final cell
dose
Time
post-
injury
Final cell
dose
IS
Quantification
method
Final time
point
No. animals
explanted
No. animals
with cells
Ref.
Kallur
et al.
(2006)
3
Normal
6–9-week fetal hNSCs
P2–3 Sprague–
Dawley rats
IC
150,000
NA
150,000
No Stereology
(other)
4 months
22
NR
[140]
Kallur
et al.
(2008)
4
Normal
6–9-week fetal hNSCs (GFP and
GFP:Pax6)
P3–5 Sprague–
Dawley rats
IC
100,000
NA
100,000
No Stereology
(other)
1 month
13
NR
[141]
GFP: Green fluorescent protein; hNSC: Human neural stem cell; IC: Immunocompetent; ID: Immunodeficient; IS: Immunosuppression; NA: Not applicable; NR: Not reported.

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response via T cells and B cells. By contrast,
xenorejection in discordant species combina-
tions occurs at three relatively distinct phases.
Within minutes of transplantation, the humoral
immune response is activated during hyper-
acute rejection [48]. Within days, infiltration of
inflammatory mediators, such as host mononu-
clear cells and neutrophils, mediate acute rejec-
tion. Finally, in the delayed xenograft rejection
response, cellular mechanisms (both NK and
T cell-mediated) modulate xenograft rejection
[49]. Understanding these cellular mechanisms is
critical, because while T-cell expansion can be
controlled by conventional immunosuppressant
agents that target calcineurin signaling, such as
cyclosporin A [50] and FK506 (Prograf®/tacroli-
mus) [51], these agents do not affect NK cells or
other rejection mechanisms. In fact, transplan-
tation of human cells into immunosuppressed
rodents often results in eventual graft failure
within the first few weeks after injection [52–57],
suggesting that pharmacological immunosup-
pression is ineffective at preventing the delayed
xenograft rejection response. These data suggest
that immunorejection in the xenotransplanta-
tion setting is complex and requires multidi-
mensional intervention (i.e., the administration
of immunosuppressive agents targeting T-cell
expansion combined with anti-NK cell), and/or
anti-costimulation factor agents, to sufficiently
attenuate the immune response in order to obtain
long-term engraftment in immuno competent
animal models [58,59].
Achieving transplant engraftment
& survival across the xenobarrier
In accordance with the immunological bar-
rier presented by xenotransplantation, several
approaches have been utilized in an attempt
to achieve high levels of transplant engraft-
ment and cell survival in the organ and bone
marrow transplantation fields. First, high-dose
combinatorial treatment with multiple conven-
tional pharmacological immunosuppressant
drugs. High dose and combinatorial pharma-
cological immunosuppression has associated
toxicity concerns in human [60,61] and animal
models [62–64]. A key question to be considered
is whether there may be exogenous, alternative
and/or unanti cipated effects of conventional
immuno suppressant agents on transplanted cell
populations. In this regard, multiple studies have
also shown that immunosuppressive agents can
interact with, and influence, various cell popula-
tions, altering cell proliferation, fate, migration
and perhaps secretomes [65–67].
Second, humanized rodent models have been
developed to lower the xenotransplantation bar-
rier. Humanized mice or mouse–human chime-
ras are immunodeficient animals that are recon-
stituted with human-derived hematopoietic cells
or tissues to minimize HLA mismatches with
subsequent human-derived cell populations [68].
While in many ways this model may be consid-
ered the ultimate goal for regenerative medicine
research, its use is significantly confounded by
several major constraints, including the low
efficacy of immune reconstitution, the time
required for generation of animals, specialized
equipment and significant cost. Thus, human-
ized rodent models of cell transplantation are
rarely utilized.
Third, constitutively immunodeficient ani-
mal models, in which components of adaptive
and/or innate immunity are compromised or
deficient, can be utilized to improve the suc-
cess of xenotransplantation. Immunodeficient
animals provide an environment in which the
immune response is suppressed endogenously,
rather than via exogenous treatment, which
allows for direct hypothesis evaluation without
complications that may arise from the immuno-
suppressive treatments necessary to support suf-
ficient engraftment in immunocompetent ani-
mals. Historically, evidence for long-term (up to
6 months post-transplant) tolerance of cellular
xenografts in immunodeficient animal models
is supported by experiments demon strating
prolonged survival of human fetal tissue and
blood cells [37,69], and later, pig and human islet
cells in constitutively T-cell deficient mice and
rats [70,71], suggesting that a lack of functional
T cells at least partially circumvents the barriers
of chronic rejection. However, the survival of
at least mouse–mouse allografts of embryonic
stem cells transplanted into heart [72] or mus-
cle [73], and human–rat xenografts of neural
stem cells transplanted into the spinal cord [7]
has also been shown to be significantly greater
in immuno deficient models compared with
immuno suppressed models. While a wide vari-
ety of immunodeficient/immuno compromised
rodents are available for xenotransplantation
studies [74–76], not all constitutively immuno-
deficient animal models achieve equal levels of
immuno deficiency; identification of a model
that is ‘sufficiently immunodeficient’, mean-
ing that it achieves 100% engraftment and
long-term survival, is therefore essential.
Owing to a loss-of-function mutation in the
mouse PRKDC gene preventing full T- and
B-cell development [77], CB-17 SCID mice,
Table 5. Normal CNS: immunodeficient animals.
Author
(year)
Model Paradigm
Cell
type
Host species/
sex
Time
post-
injury
Final cell
dose
IS
Quantification
method
Groups Final
time
point
No.
animals explanted
No.
animals
with cells
Animals
engrafted
(%)
Cell
survival
(%)
Ref.
Ogawa
et al.
(2009)
Normal
young
brain
Brain
8-week
fetal
hNSC p25
Nonobese
diabetic/severe
combined
immunodeficiency
mice
NA
2,000,000 No
Biolumin

6
months
16
16
100
10.0
[142]
hNSC: Human neural stem cell; IS: Immunosuppression; NA: Not applicable.

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Achieving stable human stem cell engraftment & survival in the CNS !"#$"%
which were used in the original hemato poetic
stem cell xenografts performed by Mosier et al.
in 1988 [37], lack functional T- and B-cells [76].
However, SCID mice retain high levels of
innate (NK cell) immunity [76], which precludes
complete avoidance of immune rejection; the
increase in graft failure in initial hemopoi-
etic stem cell transplant studies highlights
this limitation [78]. To avoid the shortcomings
observed in these early SCID models, alterna-
tive immuno deficient animal strains have been
generated to further improve graft survival [79].
Nonobese diabetic (NOD)-SCID mice, which
in addition to the T- and B-cell deficiencies
of CB-17 SCID models, also display reduced
hemolytic complement levels, reduced dendritic
cell function and defective macrophage function
[76], as well as reduced NK cell activity [80], have
been used extensively in a multitude of differ-
ent stem cell and transplantation studies with
great success [74]. Additional SCID variants
include ?2 microglobulin-deficient (B2Mnull)
mice, which display limited amounts of MHC
class I (classical and nonclassical) on the cell
surface and therefore prevent CD8 T-cell devel-
opment [81], and recombinase activating gene 1-
and 2-deficient (Rag1null and Rag2null) mice,
which, similar to PRKDC mutant mice, do
not have the ability to generate fully mature
T- and B-cell lymphocytes due to failure of
DNA strand break V(D)J recombination
[82,83]. Furthermore, recent development [84,85]
of genetic variants with nearly complete ablation
of T-, B-, and NK cell activity offer even more
effective options in a xenograft transplantation
setting [75]. These include NOD-SCID IL2RG,
and Rag2null IL2RG mice, which include a
null mutation in the gene encoding the IL-2
receptor ? chain (IL2R?), which prevents cell
surface signaling to several interleukins as well
as NK cell differentiation [86]. Additionally,
larger rodent models lacking certain compo-
nents of the immune response also exist and
may be utilized in experiments where smaller
laboratory mice are not an appropriate choice;
the principle example is the athymic nude rat,
which lacks a normal thymus and functionally
mature T cells [87]. However, caution should be
exercised when considering nude rodent models,
as evidence suggests normal to increased levels
of NK cell activity [88], which may be sufficient
to induce graft rejection [87,89]. Accordingly,
selection of an immunodeficient mouse (or rat)
model should be considered based on the known
combination of deficits in the immune response
and resulting engraftment characteristics.
Stem cells & neurotransplantation:
the inordinate influence
of ‘immunoprivilege’
In contrast to the hematopoietic transplantation
field, in which constitutively immunodeficient
animal models rapidly gained widespread use
because they enabled the study of both normal
and malignant hematopoietic repopulation [90],
the neurotransplantation field has not followed
this path. In fact, neurotransplantation research
was heavily directed in its early foundations by
a small body of data suggesting that the CNS
is immunoprivileged, which led to the wide-
spread belief that achieving engraftment in
the CNS was a relatively easy task. Billingham
and Boswell first suggested the term ‘immuno-
logically privileged’ in 1953 [91], in a paper in
which they described evidence of longer tissue
graft survival in some sites (e.g., the cornea) in
comparison to others (e.g., skin). The concept
of the CNS as an ‘immunoprivileged’ site was
extended later based on similar tissue grafting
studies using brain tissue [92]. Several mecha-
nisms explaining the relative immunoprivilege of
the CNS were hypothesized, including the tight
nature of the blood–brain barrier, the absence of
professional APCs (which are required to mount
a T-cell-mediated adaptive immune rejection
response) in the CNS, the lack of MHC expres-
sion in the CNS, reports of high levels of factors
with immunomodulatory properties in the CNS
(e.g., TGF-?), and the absence of traditional lym-
phatic drainage in the brain as an organ [41,93].
Combined, these factors were thought to render
the immune system incapable of mounting an
effective rejection response within the CNS.
More recent data has made it clear that,
while the CNS may be ‘immunologically qui-
escent’ [93], it is not at all immunologically
incompetent. In fact, the ability of T cells to
conduct surveillance via migration across even
an intact blood–brain barrier is now recog-
nized as a normal part of immune system func-
tion [94]. Similarly, we now know that there
is breakdown of the blood–brain barrier and
evidence for MHC I/II upregulation in CNS
injury/disease, the capacity for microglia, infil-
trating macrophages/monocytes, and astrocytes
to express MHC II and function as APCs [95],
and lymphatic drainage from the CNS to the
cervical lymph nodes, which may serve as sites
for antigen-mediated activation of the adaptive
immune response [96].
It is not only the CNS itself that has been
assumed to possess an immunoprivileged status.
Like mesenchymal cells, embryonic stem cells and

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!"#$"%
Anderson, Haus, Hooshmand, Perez, Sontag & Cummings
Table 6. Acute/traumatic: immunocompetent animals with immunosuppression.
Author
(year)
Model Paradigm
Cell type
Host species/
sex
Time
post-
injury
Final cell
dose
IS
Quantifi-
cation
method
Groups Final
time
point
No.
animals explanted
No.
animals
with cells
Animals
engrafted
(%)
Cell
survival
(%)
Ref.
Al Nimer
et al.
(2004)
TBI
TBI via
weight-drop
model
7-week fetal hNSC neurospheres
(passage 10)
Male SD rats
10 min
210,000
CsA
Not
performed

6 weeks
16
16
100.0
NR
[143]
Alexanian
et al.
(2011)
SCI
NYU
Impactor
hNPCs as neurospheres or as a
monolayer
Adult female
SD rats
7 days
100,000
FK506
NR

8 weeks
20
NR
NR
NR
[144]
Cho et al.
(2010)
Stroke
MCAO
EPO gene
transduced
hMSCs
(EPO-hMSCs)
Male SD rats
14 days
600,000
CsA
NR

5 weeks
40
NR
NR
NR
[145]
Cloutier
et al.
(2006)
SCI
Contusion
(IH) 50 or
200 kD
hESC-OPCs
Adult female
SD rats
7 days
2,000,000
CsA
NR
50 kD
2
months
10
10
100.0
NR
[146]
Cloutier
et al.
(2006)








200 kD
2
months
7
7
100.0
NR
[146]
Daadi
et al.
(2008)
Stroke
MCAO
H9 line
hESC-derived hNSCs
(SD 56)
Adult male SD
rats
7 days
100,000
CsA
Stereology
(MBF)

9 weeks
10
NR
NR
37.0
[147]
Darsalia
et al.
(2007)
Stroke
MCAO
hNSC from
fetal striatal
and cortical
tissue
Male Wistar
rats
7–14 days
300,000
CsA
Stereology
(CAST-
Grid)

5–6
weeks
18
NR
NR
30.0
[148]
Darsalia
et al.
(2011)
Stroke
MCAO
hNSC from
fetal striatum
Male Wistar
rats
48 h or 6
weeks
300,000, 750,000 or 1,500,000
CsA
Stereology
(CAST-
Grid)
48 h post-
injury
52 h
to 11
weeks
52
NR
NR
58.0
[149]
Darsalia
et al.
(2011)








6 weeks post-
injury

52
NR
NR
27.0
[149]
Darsalia
et al.
(2011)








Intact
striatum

52
NR
NR
31.0
[149]
Mesenchymal stem cell and BM stromal cell populations have been referred to by the general term multipotent stomal cell.
bFGF: Basic FGF; BM: Bone marrow; CAST: Computer-assisted stereological toolbox (Olympus stereology); CsA: Cyclosporine; Dex: Dexamethasone; EE: Enriched environment; EPO: Erythropoietin; FP: Fluid percussion; hESC: Human embryonic stem cell; hMSC: Human multipotent stomal cell; hNPC: Human neural progenitor cell; hNSC: Human neural stem cell; hUCB: Human umbilical cord blood; IH: Infinite horizons; IS:
Immunosuppression; MASCIS: Multicenter Animal Spinal Cord Injury Study; MBF: MicroBrightField; MCAO: Middle cerebral artery occlusion; MNP: Motor neuron progenitor; NA: Not applicable; NPC: Neural progenitor
cell; NR: Not reported; NSC: Neural stem cell; NT2N: Ntera-2 neuron; NYU: New York University; OPC: Oligodendrocyte progenitor cell; Pred: Prednisone; SCI: Spinal cord injury; SD: Sprague–Dawley; SH: Spontaneously
hypertensive; ST: Standard cages; TBI: Traumatic brain injury; UC: Umbilical cord.

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375
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Achieving stable human stem cell engraftment & survival in the CNS !"#$"%
Table 6. Acute/traumatic: immunocompetent animals with immunosuppression (cont.).
Author
(year)
Model Paradigm
Cell type
Host species/
sex
Time
post-
injury
Final cell
dose
IS
Quantifi-
cation
method
Groups Final
time
point
No.
animals explanted
No.
animals
with cells
Animals
engrafted
(%)
Cell
survival
(%)
Ref.
Dasari
et al.
(2007)
SCI
NYU
Impactor
hUCB
Adult male
Lewis rats
7 days
3,000,000
CsA
NR

2 weeks
NR
NR
NR
NR
[150]
Dasari
et al.
(2008)
SCI
NYU
Impactor
hUCB
Adult male
Lewis rats
7 days
3,000,000
CsA or
none
NA

3 weeks
5
NR
NR
NR
[151]
Eaton et al.
(2007)
SCI
Excitotoxic
lesion
Human
neuronal cell
line (hNT2.17
derived)
Adult male
Wistar rats
14 days
1,000,000
CsA
Stereology
(MBF)

8 weeks
NR
3
NR
0.3
[152]
Gao et al.
(2006)
TBI
TBI via
parasagittal
FP
bFGF primed
K048 line of
hNSCs
(8-week
human fetus)
Male SD rats
1 day
100,000
CsA
Not
performed

2 weeks
9
3 out of 3
animals examined
100.0
NR
[153]
Erceg et al.
(2010)
SCI
Transection
hESC-OPCs
and/or
H9-GFP-MNP
5–7 week old
female rats
0 day
2,000,000
CsA
Three
sections
per block
hESC-
OPCs
4
months
14
14
100.0
<1
[154]
Erceg et al.
(2010)








H9-GFP-
MNP
4
months
14
NR
NR
<1
[154]
Erceg et al.
(2010)








OPCs +
MNPs
4
months
14
NR
NR
<1
[154]
Hatami
et al.
(2009)
SCI
Lateral
hemisection
hESC-NPCs
Adult male
Wistar rats
6 days
200,000–300,000
CsA
NA

5 weeks
15
NR
NR
NR
[155]
Hicks
et al.
(2009)
Stroke
MCAO
hESC-derived neural precursors
(hNPCs):
HS181
Male Wistar
rats
7 days
800,000
CsA
Stereology
(MBF)
hNPCs +
EE
67 days
10
5
50.0
1.0
[156]
Hicks
et al.
(2009)








hNPCs +
ST
67 days
10
5
50.0
0.3
[156]
Mesenchymal stem cell and BM stromal cell populations have been referred to by the general term multipotent stomal cell.
bFGF: Basic FGF; BM: Bone marrow; CAST: Computer-assisted stereological toolbox (Olympus stereology); CsA: Cyclosporine; Dex: Dexamethasone; EE: Enriched environment; EPO: Erythropoietin; FP: Fluid percussion; hESC: Human embryonic stem cell; hMSC: Human multipotent stomal cell; hNPC: Human neural progenitor cell; hNSC: Human neural stem cell; hUCB: Human umbilical cord blood; IH: Infinite horizons; IS:
Immunosuppression; MASCIS: Multicenter Animal Spinal Cord Injury Study; MBF: MicroBrightField; MCAO: Middle cerebral artery occlusion; MNP: Motor neuron progenitor; NA: Not applicable; NPC: Neural progenitor
cell; NR: Not reported; NSC: Neural stem cell; NT2N: Ntera-2 neuron; NYU: New York University; OPC: Oligodendrocyte progenitor cell; Pred: Prednisone; SCI: Spinal cord injury; SD: Sprague–Dawley; SH: Spontaneously
hypertensive; ST: Standard cages; TBI: Traumatic brain injury; UC: Umbilical cord.

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Anderson, Haus, Hooshmand, Perez, Sontag & Cummings
Table 6. Acute/traumatic: immunocompetent animals with immunosuppression (cont.).
Author
(year)
Model Paradigm
Cell type
Host species/
sex
Time
post-
injury
Final cell
dose
IS
Quantifi-
cation
method
Groups Final
time
point
No.
animals explanted
No.
animals
with cells
Animals
engrafted
(%)
Cell
survival
(%)
Ref.
Hicks
et al.
(2009)








Sham +
hNPCs
67 days
11
5
45.5
0.6
[156]
Himes
et al.
(2006)
SCI
MASCIS
Impactor
BM-derived hMSC
Adult female
SD rats
7 days
500,000
CsA
NR

11
weeks
15
NR
NR
NR
[157]
Honma
et al.
(2006)
Stroke
MCAO
Immortalized
hMSCs with human
telomerase
gene
(hTERT-
MSCs)
Adult male SD
rats
12 h
10,000– 1,000,000
Yes
NR

7 and 25 days
NR
NR
NR
NR
[158]
Horita
et al.
(2006)
Stroke
MCAO
hMSCs
transfected
with a GDNF
gene
Adult female
SD rats
3 h
1,000,000
CsA
NR

31 days
46
NR
NR
NR
[159]
Hwang
et al.
(2009)
SCI
NYU
Impactor
Fetal hNSCs
and Olig2
over-
expressing
fetal hNSCs
Adult female
SD rats
7 days
200,000
CsA
Stereology
(only two
sections/
1 mm
region)
Fetal
hNSCs
2 weeks
for
survival
12
4
33.3
?1
[160]
Hwang
et al.
(2009)








Olig2
fetal
hNSCs
2 weeks
for
survival
12
4
33.3
?4
[160]
Kamada
et al.
(2010)
SCI
NYU
Impactor
BM-derived hMSC and BM-derived hMSC-derived
Schwann
cells
9 week old
male Wistar
rats
7 days
2,000,000
CsA + Dex
NR

6
weeks
9
NR
NR
NR
[161]
Keirstead
et al.
(2005)
SCI
Contusion
(IH)
hESC-OPCs
Adult female
SD rats
7 days
and 10
months
2,000,000
CsA
Three
sections/
1 mm
tissue
block
7 days
2
months
8
8
100.0
NR
[162]
Mesenchymal stem cell and BM stromal cell populations have been referred to by the general term multipotent stomal cell.
bFGF: Basic FGF; BM: Bone marrow; CAST: Computer-assisted stereological toolbox (Olympus stereology); CsA: Cyclosporine; Dex: Dexamethasone; EE: Enriched environment; EPO: Erythropoietin; FP: Fluid percussion; hESC: Human embryonic stem cell; hMSC: Human multipotent stomal cell; hNPC: Human neural progenitor cell; hNSC: Human neural stem cell; hUCB: Human umbilical cord blood; IH: Infinite horizons; IS:
Immunosuppression; MASCIS: Multicenter Animal Spinal Cord Injury Study; MBF: MicroBrightField; MCAO: Middle cerebral artery occlusion; MNP: Motor neuron progenitor; NA: Not applicable; NPC: Neural progenitor
cell; NR: Not reported; NSC: Neural stem cell; NT2N: Ntera-2 neuron; NYU: New York University; OPC: Oligodendrocyte progenitor cell; Pred: Prednisone; SCI: Spinal cord injury; SD: Sprague–Dawley; SH: Spontaneously
hypertensive; ST: Standard cages; TBI: Traumatic brain injury; UC: Umbilical cord.

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Achieving stable human stem cell engraftment & survival in the CNS !"#$"%
Table 6. Acute/traumatic: immunocompetent animals with immunosuppression (cont.).
Author
(year)
Model Paradigm
Cell type
Host species/
sex
Time
post-
injury
Final cell
dose
IS
Quantifi-
cation
method
Groups Final
time
point
No.
animals explanted
No.
animals
with cells
Animals
engrafted
(%)
Cell
survival
(%)
Ref.
Keirstead
et al.
(2005)








10
months
post-
injury

6
6
100.0
NR
[162]
Kelly et al.
(2004)
Stroke
MCAO
Human CNS-derived
neurospheres
Adult male SD
rats
7 days
300,000
CsA
Stereology
(MBF)

5 weeks
13
NR
NR
33.4
[163]
Kerr et al.
(2010)
SCI
NYU
Impactor
hESC-OPCs
6–8 week old
female SD rats
3 and 24 h
800,000
CsA
Not clear

8 days
5
NR
NR
NR
[164]
Kim et al.
(2009)
SCI
Contusion
(IH)
Fetal hNSCs
(F3) and
VEGF-fetal
hNSCs
Adult female
SD rats
7 days
200,000
CsA
Stereology
(CAST-
Grid)
hNSC
6 weeks
NR
5
NR
9.1
[165]
Kim et al.
(2009)








hNSC +
VEGF

NR
5
NR
11.6
[165]
Koh et al.
(2008)
Stroke
MCAO
UC-derived
hMSCs
SD rats
(male/female?)
14 days
600,000
CsA
NR

5 weeks
18
NR
NR
NR
[166]
Kurozumi
et al.
(2004)
Stroke
MCAO
BM-derived hMSCs
transfected
with BDNF
Male Wistar
rats
24 h
500,000
CsA
NR

8 and 16 days
14
NR
NR
NR
[167]
Kurozumi
et al.
(2005)
Stroke
MCAO
BM-derived hMSCs
transfected
with GDNF
Male Wistar
rats
24 h
500,000
CsA
NR

15 and 16 days
27
NR
NR
NR
[168]
Longhi
et al.
(2004)
TBI
TBI via
controlled cortical
impact
NGF-NT2N or
untransduced
NT2N
C57BL/6 mice/
male
24 h
20,000
CsA
Not
performed

1 month
?20
NR
NR
NR
[169]
Omori
et al.
(2008)
Stroke
MCAO
BM-derived hMSCs
Adult female
SD rats
Multiple 1,000,000–
3,000,000
CsA
NR

2–3
weeks
54
NR
NR
NR
[170]
Park et al.
(2010)
SCI
MASCIS
Impactor
BM-derived hMSCs
Adult SD
female rats
9 days
NR
CsA
Total cells/
section

4 and 7 weeks
22
NR
NR
NR
[171]
Rossi et al.
(2010)
SCI
Contusion
(IH)
hESC-motor neuron progenitors
Adult SD
female rats
7 days
100,000 and 500,000
CsA
NR

12
weeks
15
15
100.0
NR
[172]
Mesenchymal stem cell and BM stromal cell populations have been referred to by the general term multipotent stomal cell.
bFGF: Basic FGF; BM: Bone marrow; CAST: Computer-assisted stereological toolbox (Olympus stereology); CsA: Cyclosporine; Dex: Dexamethasone; EE: Enriched environment; EPO: Erythropoietin; FP: Fluid percussion; hESC: Human embryonic stem cell; hMSC: Human multipotent stomal cell; hNPC: Human neural progenitor cell; hNSC: Human neural stem cell; hUCB: Human umbilical cord blood; IH: Infinite horizons; IS:
Immunosuppression; MASCIS: Multicenter Animal Spinal Cord Injury Study; MBF: MicroBrightField; MCAO: Middle cerebral artery occlusion; MNP: Motor neuron progenitor; NA: Not applicable; NPC: Neural progenitor
cell; NR: Not reported; NSC: Neural stem cell; NT2N: Ntera-2 neuron; NYU: New York University; OPC: Oligodendrocyte progenitor cell; Pred: Prednisone; SCI: Spinal cord injury; SD: Sprague–Dawley; SH: Spontaneously
hypertensive; ST: Standard cages; TBI: Traumatic brain injury; UC: Umbilical cord.

Page 12

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!"#$"%
Anderson, Haus, Hooshmand, Perez, Sontag & Cummings
Table 6. Acute/traumatic: immunocompetent animals with immunosuppression (cont.).
Author
(year)
Model Paradigm
Cell type
Host species/
sex
Time
post-
injury
Final cell
dose
IS
Quantifi-
cation
method
Groups Final
time
point
No.
animals explanted
No.
animals
with cells
Animals
engrafted
(%)
Cell
survival
(%)
Ref.
Samdani et al.
(2009)
SCI
Dorso-
lateral
funiculo- tomy
BM-derived hMSCs
Adult female
SD rats
0 days
150,000
CsA
Graft size
by
thres-
holding

3 weeks
6
NR
NR
NR
[173]
Saporta et al.
(2003)
SCI
Clip
compression
hUCB
Adult male SD
rats
1 and 5 days
1,000,000
CsA
NR

3–4
weeks
NR
NR
NR
NR
[174]
Sasaki et al.
(2009)
SCI
Transection
BM-derived hMSCs
Adult female
SD rats
0 days
120,000
CsA
Flow cytometry

5 weeks
6
NR
NR
NR
[175]
Sharp et al.
(2010)
SCI
Contusion
(IH)
hESC-OPCs
Adult female
SD rats
7 days
2,000,000
CsA
Three
sections/
1 mm
tissue
block

9 weeks
NR
All
100.0
NR
[176]
Skardelly et al.
(2010)
TBI
TBI via
controlled cortical
impact
Fetal hNPCs
(passage
8–12)
Adult male SD
rats
1 day
100,000
(locally)
500,000
(systemic)
CsA +
Pred
Not
performed

12
weeks
52
NR
NR
NR
[177]
Stroemer et al.
(2009)
Stroke
MCAO
Fetal hNSCs
(CTX0E03
line)
Male SD rats
1 month 4500,
45,000 or 450,000
CsA +
Pred
NR

16
weeks
30
NR
NR
NR
[178]
Tarasenko et al.
(2007)
SCI
Contusion
(IH)
Fetal hNSCs
Adult male SD
rats
0, 3 and 9 days
200,000
CsA
Stereology
(other)
hNSC in 9 days
3
months
25
NR
NR
0.5
[179]
Tarasenko et al.
(2007)








Primed
hNSC in 9 days
3
months
28
NR
NR
0.8
[179]
Watson
et al.
(2003)
TBI
TBI via
controlled cortical
impact
NGF-
expressing and
control-
untransduced
NT2N
neurons
Male C57BL/6
mice
1 day
15,000–20,000
CsA
Not
performed

1 month
12
NR
NR
NR
[180]
Mesenchymal stem cell and BM stromal cell populations have been referred to by the general term multipotent stomal cell.
bFGF: Basic FGF; BM: Bone marrow; CAST: Computer-assisted stereological toolbox (Olympus stereology); CsA: Cyclosporine; Dex: Dexamethasone; EE: Enriched environment; EPO: Erythropoietin; FP: Fluid percussion; hESC: Human embryonic stem cell; hMSC: Human multipotent stomal cell; hNPC: Human neural progenitor cell; hNSC: Human neural stem cell; hUCB: Human umbilical cord blood; IH: Infinite horizons; IS:
Immunosuppression; MASCIS: Multicenter Animal Spinal Cord Injury Study; MBF: MicroBrightField; MCAO: Middle cerebral artery occlusion; MNP: Motor neuron progenitor; NA: Not applicable; NPC: Neural progenitor
cell; NR: Not reported; NSC: Neural stem cell; NT2N: Ntera-2 neuron; NYU: New York University; OPC: Oligodendrocyte progenitor cell; Pred: Prednisone; SCI: Spinal cord injury; SD: Sprague–Dawley; SH: Spontaneously
hypertensive; ST: Standard cages; TBI: Traumatic brain injury; UC: Umbilical cord.

Page 13

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379
future science group
Achieving stable human stem cell engraftment & survival in the CNS !"#$"%
Table 6. Acute/traumatic: immunocompetent animals with immunosuppression (cont.).
Author
(year)
Model Paradigm
Cell type
Host species/
sex
Time
post-
injury
Final cell
dose
IS
Quantifi-
cation
method
Groups Final
time
point
No.
animals explanted
No.
animals
with cells
Animals
engrafted
(%)
Cell
survival
(%)
Ref.
Wenner-
sten et al.
(2004)
TBI
TBI via
weight-drop
model
10-week
fetal hNSC
(passage 13)
Male SD rats
0 days
200,000
CsA
Four
sequential sections spaced
400 µm
apart

2 and 6 weeks
12
12
100.0
NR
[181]
Wenner-
sten et al.
(2006)
TBI
TBI via
weight-drop
model
7-week fetal hNSC
(passage 10)
Male SD rats
0 days
210,000
CsA
Four
sequential sections spaced
400 µm
apart
CsA for
3 weeks
3 or 6
weeks,
or 6
months
19
19
100.0
0.2
[182]
Wenner-
sten et al.
(2006)








CsA for
6 weeks
6 weeks
11
11
100.0
0.2
[182]
Xiao et al.
(2005)
SCI
Dorso-
lateral
funiculo-tomy
Olfactory
neuro-
epithelium
derived neurosphere-
forming cells
Adult female
SD rats
7 days
200,000
CsA
Seven
sections
up to 2 mm
away from
injury

2 weeks
for
survival
6
6
100.0
0.3
[183]
Zhang et al.
(2005)
TBI
TBI via
lateral FP
NT2N
neurons
Male SD rats
4 weeks 66,000
CsA
Not
performed

4, 8 and 12
weeks
27
27
100.0
NR
[184]
Zhang et al.
(2009)
SCI
Transection
Human
Wharton’s
jelly cell NSCs
Adult female
SD rats
0 days
200,000
CsA
Not clear

8 weeks
15
NR
NR
NR
[185]
Zhao et al.
(2002)
Stroke
MCAO
BM-derived hMSCs
Adult male SH
rats
7 days
75,000
CsA
NR

7 weeks
15
NR
NR
NR
[186]
Zheng et al.
(2010)
Stroke
Global
cerebral
ischemia
(via cardiac
arrest)
BM-derived hMSCs
Male Wistar
rats
3 h
1,000,000
CsA
NR

5 h, and 1, 3, 7
and
9 days
9
NR
NR
NR
[187]
Mesenchymal stem cell and BM stromal cell populations have been referred to by the general term multipotent stomal cell.
bFGF: Basic FGF; BM: Bone marrow; CAST: Computer-assisted stereological toolbox (Olympus stereology); CsA: Cyclosporine; Dex: Dexamethasone; EE: Enriched environment; EPO: Erythropoietin; FP: Fluid percussion; hESC: Human embryonic stem cell; hMSC: Human multipotent stomal cell; hNPC: Human neural progenitor cell; hNSC: Human neural stem cell; hUCB: Human umbilical cord blood; IH: Infinite horizons; IS:
Immunosuppression; MASCIS: Multicenter Animal Spinal Cord Injury Study; MBF: MicroBrightField; MCAO: Middle cerebral artery occlusion; MNP: Motor neuron progenitor; NA: Not applicable; NPC: Neural progenitor
cell; NR: Not reported; NSC: Neural stem cell; NT2N: Ntera-2 neuron; NYU: New York University; OPC: Oligodendrocyte progenitor cell; Pred: Prednisone; SCI: Spinal cord injury; SD: Sprague–Dawley; SH: Spontaneously
hypertensive; ST: Standard cages; TBI: Traumatic brain injury; UC: Umbilical cord.

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Regen. Med. (2011) 6(3)
380
future science group
!"#$"%
Anderson, Haus, Hooshmand, Perez, Sontag & Cummings
Table 7. Acute/traumatic: immunocompetent animals with no immunosuppression.
Author
(year)
Model Paradigm Cell type
Host
species/ sex
Time
post-
injury
Final cell dose IS
Quantifi-
cation
method
Groups
Final
time
point
No.
animals explanted
No.
animals
with
cells
Animals
engrafted
(%)
Cell
survival
(%)
Ref.
Chen et al.
(2003)
Stroke
MCAO
BM-derived hMSCs
Adult
male
Wistar
rats
1 days
1,000,000
None
NR

15 days
12
NR
NR
NR
[188]
Chen et al.
(2009)
TBI
TBI via PBBI
Human
amnion-derived
AMP cells (2 or
fewer passages)
– Stemnion cells
Male SD
rats
0 days
2,000,000
None
Not
performed

1, 2, 3,
and
4 weeks
34
NR
NR
NR
[189]
Chen et al.
(2011)
TBI
TBI via PBBI
Collagen
scaffolds
(Millipore)
seeded with
human
amnion-derived
AMP cells (2 or
fewer passages)
Male SD
rats
0 days
2,000,000
None
Not
performed

2 weeks
20
NR
NR
NR
[190]
Deng et al.
(2006)
SCI
Hemi-
section
hOECs
Adult ATN rats
and adult SD
rats
0 days
Unclear
None
12–16
sections
per cord
SD rats
1 week
4
0
0.0
NR
[191]
Ding et al.
(2007)
Stroke
MCAO
Wharton’s Jelly/
umbilical
cord-derived
hMSCs
Adult
male SD
rats
7 days
1,000,000
None
NR

10, 14, 21 or 35 days
6
NR
NR
NR
[192]
Fang et al.
(2010)
SCI
Weight
drop
(NYU)
Immortalized
hMSCs ± PACP
Adult
female
SD rats
7 days
200,000
None
NR

31 days postinjury
NR
NR
NR
NR
[193]
Fatar et al.
(2008)
Stroke
ICH
Human
processed
lipoaspirate
hMSC
Adult
male
Wistar
rats
1 day
3,000,000
None
NR

29 days
14
NR
NR
NR
[194]
Hagan et al.
(2003)
TBI
TBI via
cortical contusion
7 week old fetal hNSC
(passage 11)
SD rats/
sex NR
0 days
210,000
None
Five 25
and 100×
fields per
subject

6 days
6
5
83.3
0.12–0.95
[195]
Mesenchymal stem cell and BM stromal cell populations have been referred to by the general term multipotent stomal cell.
AMP: Amnion-derived multipotent progenitor; ATN: Athymic nude rat; BM: Bone marrow; CAST: Computer-assisted stereological toolbox (Olympus stereology); FP: Fluid percussion; Gd: Gadolinium; GLP: Glucagon like
peptide; hMSC: Human multipotent stomal cell; hNSC: Human neural stem cell; hOEC: Human olfactory ensheathing cell; ic.: Intracutaneously; ICH: Intracerebral hemorrhage; IS: Immunosuppression; iv.: Intravenously;
MCAO: Middle cerebral artery occlusion; NP: Not performed; NR: Not reported; NS: Not specified; NT2N: Ntera-2 neuron; NYU: New York University; PACP: Pituitary adenyate cyclase-activating polypeptide;
PBBI: Penetrating ballistic-like brain injury; RFP: Red fluorescent protein; SCI: Spinal cord injury; SD: Sprague–Dawley; TBI: Traumatic brain injury; tx: Transplantation; UC: Umbilical cord.

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www.futuremedicine.com
381
future science group
Achieving stable human stem cell engraftment & survival in the CNS !"#$"%
Table 7. Acute/traumatic: immunocompetent animals with no immunosuppression (cont.).
Author
(year)
Model Paradigm Cell type
Host
species/ sex
Time
post-
injury
Final cell dose IS
Quantifi-
cation
method
Groups
Final
time
point
No.
animals explanted
No.
animals
with
cells
Animals
engrafted
(%)
Cell
survival
(%)
Ref.
Heile et al.
(2009)
TBI
TBI via
controlled cortical
impact
hTERT
immortalized
GLP-1
expressing, alginate encapsulated
BM-derived hMSCs
Male SD
rats
0 days
64,000
None
NP

2, 7 and 14 days
13
NR
NR
NR
[196]
Hu et al.
(2010)
SCI
Weight
drop
UC-derived
hMSCs
Female
SD rats
1 day
400,000
None
NR

8 weeks
12
NR
NR
NR
[197]
Hung et al.
(2010)
TBI
TBI via
dragonfly
FP device
Immortalized
hTERT/RFP cord blood-derived hMSC (with and
without RFP)
Male SD
rats
3 days
100,000
None
NP

2, 7, and 14 days
NR
NR
NR
NR
[198]
Jeong et al.
(2003)
Stroke
ICH
Fetal brain hNSC
(HB1.F3)
Male SD
rats
1 day
5,000,000
None
NR

8 weeks
12
NR
NR
NR
[199]
Kim et al.
(2010)
TBI
TBI via
controlled cortical
impact
BM-derived hMSCs (supplied by FCB
Pharmicell)
Male SD
rats
1 day
2,000,000
None
NP

1, 2, 8, 15, 22
and 29
days after
TBI
40
NR
NR
NR
[200]
Lee et al.
(2009)
Stroke
ICH
Fetal brain hNSC
(HB1.F3)
overexpressing
Akt1
F3.Akt1
mice
7 days
200,000
None
Stereo-
logy
(CAST-
Grid)
F3.Akt1,
2 weeks
9 weeks
9
NR
NR
53.9
[201]
Lee et al.
(2009)








F3.Akt1
and
8 weeks
9 weeks
9
NR
NR
32.4
[201]
Lee et al.
(2009)








F3 control,
2 weeks
9 weeks
9
NR
NR
39.2
[201]
Lee et al.
(2009)








F3 control,
8 weeks
9 weeks
9
NR
NR
16.3
[201]
Lee et al.
(2008)
Stroke
ICH
Fetal brain hNSC
H1 clone
Male SD
rats
2 or 24 h
1,000,000 ic. 5,000,000 iv.
None
NR

7 weeks
179
NR
NR
NR
[202]
Mesenchymal stem cell and BM stromal cell populations have been referred to by the general term multipotent stomal cell.
AMP: Amnion-derived multipotent progenitor; ATN: Athymic nude rat; BM: Bone marrow; CAST: Computer-assisted stereological toolbox (Olympus stereology); FP: Fluid percussion; Gd: Gadolinium; GLP: Glucagon like
peptide; hMSC: Human multipotent stomal cell; hNSC: Human neural stem cell; hOEC: Human olfactory ensheathing cell; ic.: Intracutaneously; ICH: Intracerebral hemorrhage; IS: Immunosuppression; iv.: Intravenously;
MCAO: Middle cerebral artery occlusion; NP: Not performed; NR: Not reported; NS: Not specified; NT2N: Ntera-2 neuron; NYU: New York University; PACP: Pituitary adenyate cyclase-activating polypeptide;
PBBI: Penetrating ballistic-like brain injury; RFP: Red fluorescent protein; SCI: Spinal cord injury; SD: Sprague–Dawley; TBI: Traumatic brain injury; tx: Transplantation; UC: Umbilical cord.