Stem cell therapeutics: potential in the treatment of inflammatory bowel disease.

Abstract

Stem cell therapies may be valuable in treatment of inflammatory bowel disease (IBD). Here we focus on two very different types of stem cells - hematopoietic stem cells and mesenchymal stem cells. Myeloablation and hematopoietic stem cell transplantation alter host immune response by reconstituting the recipient's blood cell lines with donor cells. Autologous hematopoietic reconstitution may "reboot" mucosal immunity to a normal baseline state, but does not alter any underlying genetic predisposition to IBD. In contrast, allogeneic hematopoietic transplantation reconstitutes all blood lineages from a tissue-matched donor who presumably does not have a genetic predisposition to IBD. Compared with autologous hematopoietic transplantation, allogeneic hematopoietic transplantation carries a much greater risk of complications, including graft-versus-host disease. Mesenchymal stem cells can give rise to cartilage, bone and fat in vitro, but do not reconstitute hematopoiesis after transplantation. Systemically infused mesenchymal stem cells appear to favorably downregulate host immune responses through poorly understood mechanisms. In addition, mesenchymal stem cells may be applied topically to help close fistulas associated with Crohn's disease. For all of these stem cell therapy applications for IBD, only cases and small series have been reported. Larger clinical trials are planned or ongoing.

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Clinical and Experimental Gastroenterology 2010:3 1–10
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ES Swenson1
ND Theise2
1Department of internal Medicine,
Section of Digestive Diseases,
Yale University School of Medicine,
New Haven, CT, USA; 2Departments
of Pathology and Medicine (Division
of Digestive Diseases), Beth israel
Medical Center – Albert Einstein
College of Medicine, New York,
NY, USA
Correspondence: ND Theise
Beth israel Medical Center, Division
of Digestive Diseases, First Avenue at
16th Street, New York, NY 10003, USA
Email ntheise@chpnet.org
Abstract: Stem cell therapies may be valuable in treatment of inflammatory bowel disease
(IBD). Here we focus on two very different types of stem cells – hematopoietic stem cells
and mesenchymal stem cells. Myeloablation and hematopoietic stem cell transplantation
alter host immune response by reconstituting the recipient’s blood cell lines with donor cells.
Autologous hematopoietic reconstitution may “reboot” mucosal immunity to a normal baseline
state, but does not alter any underlying genetic predisposition to IBD. In contrast, allogeneic
hematopoietic transplantation reconstitutes all blood lineages from a tissue-matched donor
who presumably does not have a genetic predisposition to IBD. Compared with autologous
hematopoietic transplantation, allogeneic hematopoietic transplantation carries a much greater
risk of complications, including graft-versus-host disease. Mesenchymal stem cells can give rise
to cartilage, bone and fat in vitro, but do not reconstitute hematopoiesis after transplantation.
Systemically infused mesenchymal stem cells appear to favorably downregulate host immune
responses through poorly understood mechanisms. In addition, mesenchymal stem cells may
be applied topically to help close fistulas associated with Crohn’s disease. For all of these stem
cell therapy applications for IBD, only cases and small series have been reported. Larger clinical
trials are planned or ongoing.
Keywords: inflammatory bowel disease, Crohn’s disease, stem cell therapy, bone marrow
transplant, mesenchymal stem cell
Introduction
Stem cells are defined by asymmetric cell division, self-renewal, and multilineage
differentiation. Stem cell-based therapies hold great promise for many diseases.
Embryonic stem cells (ES) are pluripotent cells derived from the preimplantation
embryo, capable of forming tissues from all three germ layers in vitro and in vivo. The
ability of ES cells to expand in culture and differentiate to specific phenotypes under
various culture and growth factor conditions makes them an attractive source of cells
for therapy. Induced pluripotent stem cells (iPS) can be derived from adult somatic
cells forced to reprogram to an ES-like state in culture. Like ES cells, iPS cells can be
redirected toward other phenotypes under specific culture conditions. iPS cells are not
derived from embryos, avoiding ethical concerns regarding the use of human embryos.
iPS cells can also be made from any patient, allowing the production of patient-specific
and disease-specific cells for research and treatment. Undifferentiated ES and iPS
cells can both give rise to teratomas after transplantation, so complete eradication of
undifferentiated cells is a critical step toward the clinical use of cell therapy when ES
or iPS cells are used to produce differentiated cells for therapy.
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In contrast, adult stem cells are derived from mature
organs and are much more limited in differentiation potential
compared with ES or iPS. As such, adult stem cells might
be better considered as multipotent “progenitor” cells rather
than stem cells. However, the language of “adult stem cells”
is well established so we will follow this convention. The best
understood adult stem cells are hematopoietic stem cells,
which can be enriched from the bone marrow or collected
from peripheral blood. After transplantation into properly
conditioned recipients, hematopoietic stem cells reconstitute
and maintain all the mature blood lineages. Bone marrow
transplantation has become an accepted treatment for leuke-
mias, lymphomas, and other blood diseases. For patients fac-
ing otherwise incurable and fatal blood diseases, the potential
benefits of bone marrow transplantation outweigh the risks
of infection, hemorrhage and graft-vs-host disease.
Mesenchymal stem cells (MSC) are an entirely different
type of adult stem cell. MSC can be derived from bone mar-
row, fat, or other tissues. MSC are perhaps more restricted in
their differentiation potential to mesodermal tissues such as
fat, cartilage and bone. Transplanted MSC do not reconsti-
tute hematopoietic lineages, but can alter the host immune
response. In this review we will consider cell therapy based
on hematopoietic stem cell transplantation or MSC infusion
for the treatment of Crohn’s disease (CD) and ulcerative
colitis (UC). To date, there are no reports of therapeutic
interventions for inflammatory bowel disease (IBD) using
ES or iPS-derived cells.
In patients with IBD, mucosal ulceration and inflamma-
tion may cause abdominal pain, chronic diarrhea, anemia
and malnutrition. In UC, the inflammation is generally
limited to the mucosa of the colon. In contrast, the inflam-
mation in CD affects all layers of the bowel wall and is
not limited to the colon. The transmural inflammation
of CD may lead to bowel obstruction or fistula forma-
tion requiring surgical intervention. In both conditions,
chronic inflammation is associated with an increased
risk of intestinal malignancy. IBD may be considered an
autoimmune disease, resulting from inappropriate immune
reactivity against one’s own tissues in the digestive tract.
The mainstay of clinical treatment is a combination of
anti-inflammatory agents such as 5-aminosalicylates and
immunosuppressive medications, including corticoste-
roids and immunomodulators such as azathioprine. Newer
agents, including monoclonal antibodies directed against
tumor necrosis factor or alpha-4-integrin, are available for
patients who are unable to achieve remission with standard
immunosuppression. Despite treatment, the morbidity and
cost of IBD remain high. Corticosteroids are not effective
for maintaining remission of IBD and induce well-known
adverse side effects, including weight gain, diabetes and
osteoporosis. Immunosuppression carries significant risk
for infection by opportunistic pathogens. New treatment
approaches are needed.
Recent advances reveal a primary role of dysregula-
tion of the immune system in the pathogenesis of IBD.
Sophisticated genome-wide association studies implicate
maladaptive signaling of a number of cytokines and their
receptors.1 Examples include variants in genes encoding
NOD2/CARD15, IL23R, TNFSF152,3 and IL-10R.4 Mouse
models of IBD may be categorized as chemical, genetic,
immunologic, and spontaneous.5 Each approach offers
different strengths and limitations, but it is now clear that
the mucosal immune response to luminal antigens plays a
central role in the pathogenesis of IBD. Genetically suscep-
tible mice reared under germ-free conditions fail to develop
disease, demonstrating the essential role of luminal flora.
Classic experiments demonstrated that IBD-like illness can
be transmitted by adoptive transfer of pathogenic T cells in
mice.6 In a susceptible host, inappropriate and prolonged
immunologic response to mucosal flora results from failure
of regulatory T cells to restrict the activity of self-reactive
effector T cells.7–9 While bone marrow transplant from IL-10
knockout mice into wild-type recipients does not transfer
IBD, colitis can be markedly ameliorated in IL-10 knockout
mice after bone marrow transplantation with normal bone
marrow. The improvement of colitis after transplantation of
normal bone marrow into IL-10 deficient mice appears to be
due to engraftment of donor-derived subepithelial myofibro-
blasts.10 A possible human case of adoptive transfer of IBD
was reported in a patient undergoing allogeneic bone marrow
transplant (BMT) for Hodgkin’s disease. Though the patient
had no prior history of IBD, she developed acute fulminant
Crohn’s colitis 6 months after allogeneic BMT. While the stem
cell donor had no personal or family history of IBD, genomic
analysis showed that the donor, but not the recipient, carried
a CD-associated polymorphism in the NOD2/CARD15
gene. Donor and recipient also had numerous HLA class III
haplotype mismatches at the IBD3 locus.11
While immunosuppression can reduce and control inflam-
mation, it fails to fundamentally interrupt the underlying
disease process. Advances in bone marrow transplantation
now allow the ablation and replacement of the hematopoietic
system with autologous or allogeneic hematopoietic stem
cells. In some cases, this appears to effectively interrupt the
cycle of inflammation by “resetting” the immune system with

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naïve cells. Another novel treatment approach is the use of
mesenchymal stem cells (MSC), typically derived from bone
marrow or fat, as immunosuppressive agents to downregulate
mucosal immune reactivity.
There are many case reports and small retrospective
series of patients experiencing dramatic improvement in
chronic non-IBD autoimmune conditions following autolo-
gous or allogeneic hematopoietic stem cell transplantation
for unrelated malignancies. These unexpected successes led
to trials of hematopoietic stem cell transplantation (mostly
autologous) as a salvage therapy for autoimmune diseases
refractory to standard immunosuppressive therapy.12 Simi-
larly, unexpected remission of IBD in patients undergoing
BMT for other reasons inspired examination of BMT as a
therapy for IBD.
This review will focus on two “stem cell therapy”
approaches to treating IBD by fundamentally altering the
mucosal immune response: bone marrow hematopoietic
stem cell transplantation and mesenchymal stem cell
transplantation.13
Autologous bone marrow stem cell
transplantation for IBD
The first report of remission of IBD after autologous hema-
topoietic stem cell transplantation was that of a 41-year-old
woman with more than 20 years of fistulizing CD, who
subsequently developed non-Hodgkins’ lymphoma (NHL).
Her NHL was treated with chemotherapy and autologous
bone marrow stem cell rescue. Six months after BMT, the
lymphoma was in remission and she was free of CD symp-
toms for the first time in many years. The authors speculated
that the improvement in her CD resulted from the BMT, and
concluded that CD need not be an absolute contraindication
to autologous BMT.14 Several more anecdotal reports
of clinical remission of IBD in patients who underwent
chemotherapy and autologous hematopoietic stem cell rescue
for coincidental malignancies followed (Table 1).
Based in part on the successful treatment of patients with
CD and coincident malignancies using stem cell mobiliza-
tion, myeloablation, and autologous stem cell rescue, this
approach has been attempted as salvage therapy for IBD
in patients who did not have malignancies (Table 2). The
patients reported in those studies had active, refractory CD
with multiple complications. Oyama et al15 reported clinical
remission in 11 of 12 patients, while Cassinotti et al16 reported
remission in 3 of 4 patients. This approach effectively takes
immunosuppression to the extreme, completely ablating the
immune system and reconstituting it with hematopoietic
stem cells which give rise to naïve lymphoid and myeloid
cells. The effectiveness of this approach is consistent with the
model that dysregulation of T cell activity against mucosal
self antigens plays a major role in the pathogenesis of IBD.
The lack of recurrent disease after autologous BMT indicates
that interruption of the pro-inflammatory T cell response is
sufficient to break the maladaptive cycle of self-reactivity.
However, the number of patients reported is very small and
there were no controls. The success of this approach might
be overestimated by reporting bias, since therapeutic failures
and treatment-related adverse events may be less frequently
reported. One patient with remission of CD following autolo-
gous BMT for NHL experienced relapsed of her CD 8 years
later, indicating that long-term follow up is essential.17
Despite these limitations, the clinical improvements are
very impressive in a group of patients refractory to even the
best available standard treatment. While the risk of morbidity
and mortality from sepsis and hemorrhage during the interval
between myeloablation and autologous hematopoietic reconsti-
tution is significant, a carefully designed, prospective clinical
Table ? Case reports of iBD outcomes after myeloablation and autologous stem cell transplantation for coincidental malignancy
Disease (n)IndicationConditioningGraft IBD outcomeRef
CD (n = 1)
NHL Chemo
BMSC 3 × 10e8/kg
remission at 6 mos
Off immunosuppression
14
UC (n = 1)
CD (n = 1)
CD (n = 1)
Breast cancerChemo mPBSC ?dose
remission  2 yrs
67
Breast cancerChemo mPBSC ?dose
remission  2 yrs
67
T cell NHLChemo
mPBSC 9.8 × 10e8/kg
remission 7 yrs
Off immunosuppression
68
CD (n = 1)
Hodgkin’s
Chemo mPBSC ?dose
remission  3 yrs
Off immunosuppression
69
CD (n = 1)
AMLChemo TBi BMSC, mPBSC ?dose
remission  6 yrs
Off immunosuppression
70
Abbreviations: See list in text.

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trial is warranted for patients who have failed conventional
therapy and are willing to accept the risk of autologous
BMT. A multicenter, prospective, randomized Phase III trial,
“Autologous Stem Cell Transplantation in Crohn’s Disease
(ASTIC)” is underway in Europe. All patients enrolled in this
trial will undergo stem cell mobilization and leukapheresis.
Patients will then be randomized to undergo either immediate
or delayed (one year) immunoablation and autologous stem
cell transplantation. Patients in the delayed transplant group
will continue to receive optimal conventional care for CD.
This design allows all patients in the trial the opportunity to
undergo autologous BMT, with the delayed transplant group
serving as controls. The immediate transplant group will be
compared with the delayed transplant group in terms of disease
remission, defined as a CD activity index of 150 without
steroids or immunosuppressive drugs and no mucosal erosion
or ulceration at ileocolonoscopy, and no definite evidence of
small bowel Crohn’s Disease on barium studies. A total of
48 patients will be recruited. As of July, 2009, 14 patients had
been enrolled, 7 of whom have undergone autologous BMT.
Additional details are available at http://www.nottingham.
ac.uk/icr/astic/index.php. It is not clear whether autologous
BMT will benefit patients with germline polymorphisms
in CD-susceptibility genes, which will not be altered by
autologous BMT. This issue will need to be considered in the
outcome analysis of the clinical trials.
Allogeneic bone marrow stem cell
transplantation
There have been numerous reports of fortuitous resolution of
non-IBD autoimmune diseases such as rheumatoid arthritis
and psoriasis in patients who underwent allogeneic BMT
for leukemias.18–21 The first reported case of a patient with
UC undergoing allogeneic BMT was a 39-year-old woman
with a 12-year history of UC, who subsequently developed
AML. Following induction and consolidation treatment with
chemotherapy, she received an allogeneic BMT from her
HLA-matched brother. Four years later, her AML remained
in remission and her UC was clinically inactive.20 The first
reported case of a patient with CD undergoing allogeneic
BMT was a 35-year-old man with stricturing CD who sub-
sequently developed acute myelocytic leukemia (AML). The
AML was treated with multiagent chemotherapy and the
patient underwent allogeneic BMT from his HLA-matched
brother. His post-transplant course was complicated by mild
GVHD of the skin, which responded to corticosteroids. All
immunosuppression was tapered off over the next 7 months
and he remained in remission of both AML and CD for at
least 8 years.22
Two retrospective series of patients with both IBD
and leukemia who underwent allogeneic BMT reported
a substantial number of remissions from IBD (Table 3).
Lopez-Cubero23 reported 6 CD patients who underwent
allogeneic BMT for CML or AML. All were treated with
multiagent chemotherapy for leukemia. Transplant condi-
tioning regimens included cyclophosphamide and total body
irradiation. Allogeneic donor cells were HLA-matched in
all but one case and were not T cell-depleted. CD activity
could not be assessed in the patient with AML, who died
from sepsis 97 days after transplant. Of the five survivors,
four achieved symptomatic remission from CD over 4 to
15 years of follow-up. Both acute and chronic GVHD of the
Table ? Case reports and small series of inflammatory bowel disease outcomes after myeloablation and autologous stem cell
transplantation for Crohn’s disease
Disease (n) ConditioningGraft IBD outcomeRef
CD (n = 1)
CycT-cell depleted
CD34+ mPBSC
6.4 × 10e6/kg
T cell-depleted
CD34+ mPBSC
3.4 × 10e6/kg
T-cell depleted
CD34+ mPBSC
2 × 10e6/kg
remission for 9 mos
recurrent aphthous ulcers
Maint. corticosteroids and MTX
Symptomatic remission for 5 mos
Endoscopic and pathologic improvement, off
immunosuppression
remission in 11 of 12
7–37 mos follow-up
Corticosteroids tapered over 2–6 mos
71
CD (n = 1)
Cyc ATG72
CD (n = 12)
Cyc ATG 15
[*2 of these subjects were already reported by Burt et al in 2003]
CD (n = 1)
Not stated
CD (n = 1)
Not stated
CD (n = 4)
Cyc ATG
Not stated
Not stated
mPBSC ?dose
remission for 8 yrs followed by relapse
remission for 6 yrs
remission in 3 of 4 11–20 mos follow-up
Off immunosuppression
17
73
16
Abbreviations: See list in text.

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skin and/or liver were noted in the same four patients who
achieved remission from CD.
Ditschkowski and colleagues24 reported a retrospective
review of 7 CD patients and 4 UC patients who underwent
allogeneic BMT for AML, CML or myelofibrosis. Five of
the CD patients had a history of fistula or luminal stenosis.
Prior to BMT, five patients had inactive IBD, while six were
described as having mild or low activity based on symp-
toms, endoscopic findings, or histology. The chemotherapy,
myeloablative conditioning regimen and transplantation
protocols varied. One patient died within the first year after
transplant from pulmonary fungal infection. Of the 10 sur-
vivors, only 1 had mild CD after transplant, while the other
9 achieved remission from IBD during a median followup
period of 34 months (range 3 to 117 months). Eight patients
developed Grade I or II GVHD, which was managed success-
fully with steroids. None developed severe or chronic GVHD.
A very recent report identified loss-of-function mutations in
IL10-RA and IL-10RB in patients with early onset, severe
enterocolitis.4 One patient with a mutation in the IL1-10RB
gene suffered from severe anocutaneous fistula, refractory
to standard therapy. He underwent allogeneic BMT from
an HLA-matched sibling who did not carry the IL-10RB
mutation. He achieved full donor hematopoietic chimerism,
and his post-transplant course was marked by mild GVHD,
treated successfully with corticosteroids. More than 1 year
after transplantation, his IBD was fully in remission.4 In
the case where the genetic mutation underlying IBD could
be clearly identified, autologous transplantation would not
have been helpful. An HLA-matched sibling donor without
that mutation was available, so allogeneic transplantation
was both ethical and practical. To our knowledge, there are
no planned prospective clinical trials of allogeneic BMT in
IBD, presumably due to concerns for the greater incidence of
transplant-related complications in allogeneic BMT recipi-
ents compared with autologous BMT.
Immunomodulatory stem cell
therapy with MSC
MSC are a fibroblast-like cell population, first recognized as
a population of non-hematopoietic bone marrow cells which
adhere to plastic tissue culture dishes.25 MSC are a multi-
potent stem cell population, capable of differentiating into
osteocytes, chondrocytes and adipocytes under appropriate
culture conditions.26 In an attempt to standardize the definition
of MSC, minimal criteria were proposed (Table 4).27 MSC
have now been isolated from a wide variety of adult tissues,28
though most attention has focused on MSC derived from bone
marrow or fat. A great deal of interest has focused on poten-
tial therapeutic uses for MSC due to their reported ability to
suppress inflammation and promote tissue healing.29
Several potential mechanisms have been proposed for
the potential immunomodulatory effects of MSC, including
release of soluble factors (cytokines, chemokines, growth
factors), induction of cell cycle arrest in pro-inflammatory
Table ? Minimal criteria for defining multipotent mesenchymal
stem cells27
1. Adherent to plastic under standard culture conditions
2. Express CD105, CD73 and CD90
3. Lack expression of CD45, CD34, CD14 or CD11b, CD79a or CD19
and HLA-Dr
4. Differentiate to osteoblasts, adipocytes and chondroblasts in vitro
Abbreviations: See list in text.
Table ? Case reports and small series of inflammatory bowel disease outcomes after myeloablation and allogeneic stem cell
transplantation
Disease (n) IndicationConditioningGraft IBD outcome Ref
UC (n = 1)
CD (n = 1)
AML Not statedNot stated remission 4 yrs 20
AMLChemo AlloBMT CSA
for 7 mos
Steroids for 2 mos
remission 7 years off
immunosuppression
22
CD (n = 5)
CML Chemo TBiAlloBMT, variedremission in 4 of 5
patients followed for
4–15 yrs
23
(A sixth CD patient with AML died 97 days after alloBMT; recurrent CD could not be evaluated)
CD (n = 7)
UC (n = 4)
CD (n = 1)
AML, CML, MFvaried AlloBMT, varied remission in 9 of 10
survivors
24
iBD, iL-10rB mutation
Chemo Sibling AlloBMT remission 1 yr4
Abbreviations: See list in text.