ARTHRITIS & RHEUMATISM
Vol. 60, No. 9, September 2009, pp 2822–2829
© 2009, American College of Rheumatology
Loss of Peroxisome Proliferator–Activated Receptor ? in
Mouse Fibroblasts Results in Increased Susceptibility to
Bleomycin-Induced Skin Fibrosis
Mohit Kapoor,1Matthew McCann,1Shangxi Liu,1Kun Huh,1Christopher P. Denton,2
David J. Abraham,2and Andrew Leask1
Objective. There is increasing evidence that the
transcription factor peroxisome proliferator–activated
receptor ? (PPAR?) plays an important role in control-
ling cell differentiation, and that PPAR? ligands can
modify inflammatory and fibrotic responses. The aim of
the present study was to examine the role of PPAR? in
a mouse model of skin scleroderma, in which mice
bearing a fibroblast-specific deletion of PPAR? were
Methods. Cutaneous sclerosis was induced by
subcutaneous injection of bleomycin, while untreated
control groups were injected with phosphate buffered
saline. Mice bearing a fibroblast-specific deletion of
PPAR? were investigated for changes in dermal thick-
ness, inflammation, collagen content, and the number of
?-smooth muscle actin–positive cells. The quantity of
the collagen-specific amino acid hydroxyproline was
also measured. In addition, the effect of PPAR? deletion
on transforming growth factor ?1 (TGF?1) signaling in
the fibroblasts was investigated.
Results. Bleomycin treatment induced marked
cutaneous thickening and fibrosis in all treated mice.
Deletion of PPAR? resulted in enhanced susceptibility
to bleomycin-induced skin fibrosis, as indicated by
increases in all measures of skin fibrosis and enhanced
sensitivity of fibroblasts to TGF?1 in PPAR-deficient
Conclusion. These results indicate that PPAR?
suppresses fibrogenesis. Specific agonists of PPAR?
may therefore alleviate the extent of the development of
Normal tissue repair involves the reconstitution
of epithelia barrier and connective tissue (1). Specialized
fibroblasts, the myofibroblasts, generate the adhesive
and tensile forces required for closure of the wound.
Whereas myofibroblasts disappear from the wound in
normal tissue repair, persistence of myofibroblasts is
evident in fibroproliferative diseases such as sclero-
derma (systemic sclerosis [SSc]) (2,3). Controlling the
excessive adhesive and tensile forces mediated by myo-
fibroblasts resident within scars in SSc is therefore
essential for developing rational antifibrotic strategies.
The nuclear receptor peroxisome proliferator–
activated receptor ? (PPAR?) can heterodimerize with
the retinoid X receptor and recognizes PPAR response
elements in promoters (4). PPAR? agonists have anti-
fibrotic properties, characterized by inhibition of pulmo-
nary myofibroblast differentiation and collagen produc-
tion (5). However, it is now recognized that PPAR?
agonists also act through mechanisms other than direct
targeting of PPAR? (6). Thus, it remains unclear
Supported by grants from the Canadian Foundation for
Innovation, the Canadian Institutes of Health Research, the Ontario
Thoracic Society, the Arthritis Research Campaign, and the Raynaud’s
and Scleroderma Association. Dr. Kapoor is recipient of postdoctoral
fellowships from the Canadian Arthritis Network and the Ontario
Ministry of Innovation. Dr. Leask is a New Investigator of the Arthritis
Society (Scleroderma Society of Ontario), recipient of an Early
Researcher Award from the Ontario Ministry of Research and Inno-
vation, and a member of the Canadian Scleroderma Research Group
New Emerging Team.
1Mohit Kapoor, PhD, Matthew McCann, BSc, Shangxi Liu,
PhD, Kun Huh, Andrew Leask, PhD: University of Western Ontario,
London, Ontario, Canada;
David J. Abraham, PhD: University College London (Royal Free
Campus), London, UK.
Address correspondence and reprint requests to Andrew
Leask, PhD, CIHR Group in Skeletal Development and Remodeling,
Department of Physiology and Pharmacology, Schulich School of
Medicine and Dentistry, Dental Sciences Building, University of West-
ern Ontario, London, Ontario N6A 5C1, Canada. E-mail: Andrew.
Submitted for publication November 20, 2008; accepted in
revised form May 26, 2009.
2Christopher P. Denton, PhD, FRCP,
whether PPAR? specifically modulates fibrogenic re-
sponses in vivo. Investigation of the contribution of
PPAR? in vivo requires the generation of knockout
(KO) mouse models. Because mouse embryos deficient
in PPAR? die at embryogenesis (7), the creation of
PPAR? mice with conditional knockdown (deletion)
of the gene of interest is essential for studying the effect
of PPAR? in more differentiated cell types.
Although no animal model has been described as
being able to reproduce all of the manifestations of SSc
precisely, one model in which cutaneous sclerosis occurs
is the bleomycin-induced model (8). Bleomycin, an
antibiotic obtained from Streptomyces venticillus, sup-
presses tumors and is frequently used to treat cancers
(9). Since fibrosis is a well-known side effect of bleomy-
cin treatment, bleomycin has been used to induce exper-
imental fibrosis in rodents (10). Moreover, SSc has been
reported to develop in patients with cancer after they
received bleomycin therapy, and local injection of bleo-
mycin was shown to cause skin fibrosis (11). Thus, in this
study, we investigated the contribution of PPAR? to
dermal sclerosis in a model using mice with a skin-
specific deletion of PPAR?.
MATERIALS AND METHODS
Generation of PPAR?-KO mice. Mice that carry a
tamoxifen-inducible Cre-recombinase under the control of a
fibroblast-specific regulatory sequence from the pro?2(I) col-
lagen gene (12) were crossed with mice that are homozygous
for the PPAR? target allele (The Jackson Laboratory, Bar
Harbor, ME), which generated Cre/PPAR?-heterozygote
mice. The second cross resulted in Cre/PPAR?-homozygote
mice. Animals used for these experiments were genotyped by
polymerase chain reaction (PCR) to detect PPAR? and Cre, as
described on The Jackson Laboratory Web site (http://
www.jax.org) and as previously described (12).
To delete PPAR?, a stock solution of tamoxifen (4-
hydroxitamoxifen; Sigma, St. Louis, MO) in ethanol (100
mg/ml) was diluted in corn oil to 10 mg/ml. Adult mice (at 3
weeks of age) were given intraperitoneal injections of tamox-
ifen (0.1 ml of 10 mg/ml) over 5 days. Deletion of PPAR? was
verified by PCR genotyping using primers recommended by
the supplier (The Jackson Laboratory), and immunofluores-
cence staining and Western blotting were performed with an
anti-PPAR? antibody (Cell Signaling Technology, Beverly,
MA). All animal protocols were approved by the regulatory
authority of the appropriate experimental animal care and use
Bleomycin treatment. Three weeks after generation of
the PPAR?-KO mice, as well as mice without conditional
deletion of the PPAR? gene as controls (hereafter referred to
as PPAR?-conditional control mice), the animals were pre-
pared for bleomycin treatment. Bleomycin (Sigma), diluted to
0.1 units/ml with phosphate buffered saline (PBS), was steril-
ized with filtration. One hundred microliters of bleomycin, or
PBS as control, was injected subcutaneously into a single
location on the shaved back of PPAR?-conditional control and
PPAR?-KO mice, once daily for 2, 4, and 6 weeks (the time
course of bleomycin treatment). Mice were then killed by CO2
inhalation at each respective time point, and skin samples were
collected for histology, immunohistochemistry, and hy-
Cell culture, immunofluorescence, and Western blot
analysis. Dermal fibroblasts were isolated from the explants
derived from 4–6-week-old animals in a manner as previously
described (3). Cells were subjected to analysis by indirect
immunofluorescence as previously described (3), followed by
analysis with an appropriate secondary antibody (Jackson
ImmunoResearch, Avondale, PA). Photography was carried
out using a digital camera (Empix Imaging Institute, Missis-
sauga, Ontario, Canada) and images were viewed with a Zeiss
Axiphot microscope (Carl Zeiss Instruments, Thornwood,
NY). For some assays, cells were lysed in 2% sodium dodecyl
sulfate, and proteins were quantified (Pierce, Rockford, IL)
and subjected to Western blot analysis as previously described
(4). The antibodies used were as follows: anti–?-smooth mus-
cle actin (anti–?-SMA) (1:5,000; Sigma), anti–?-actin (1:5,000;
Sigma), anti–phosphorylated Smad3 (1:500; Cell Signaling
Technology), and anti-PPAR? (1:500; Cell Signaling Tech-
Histologic assessment of inflammation. Sections
(0.5 ?m) were cut using a microtome (Leica Instruments,
Nussloch, Germany) and collected on Superfrost Plus slides
(Fisher Scientific, Fair Lawn, NJ). Sections were then dewaxed
in xylene and rehydrated by successive immersion in descend-
ing concentrations of alcohol. To assess the effect of PPAR?
deletion on inflammation, sections were stained with hematox-
ylin and eosin (H&E) (Fisher Scientific). Staining with H&E
was performed according to the manufacturer’s recommenda-
tions. The effects of PPAR? deletion on inflammation were
graded by 3 separate blinded observers (MM, SL, and KH) on
a scale of 0–3, in which 0 signifies no inflammatory cells, 1
signifies presence of a few inflammatory cells, 2 signifies
moderate influx of inflammatory cells, and 3 signifies extensive
influx of inflammatory cells.
Histologic assessment of collagen content. To assess
the effects of PPAR? deletion on collagen synthesis, trichrome
collagen stain was utilized. The collagen content in each
section was assessed by 3 blinded observers (MM, SL, and KH)
using the following assessment criteria: 0 signifies no collagen
fibers, 1 signifies a few collagen fibers, 2 signifies a moderate
amount of collagen fibers, and 3 signifies an excessive amount
of collagen fibers.
?mmunohistochemical analysis of ?-SMA. Sections
were cut and processed for immunohistochemistry in the same
manner as described above. Immunolabeling of ?-SMA was
performed using the DakoCytomation LSAB? System-HRP
kit (Dako, Carpinteria, CA). Immunohistochemical proce-
dures were carried out in accordance with the manufacturer’s
recommendations. Briefly, endogenous peroxidase was
blocked using 0.5% H2O2in methanol for 5 minutes. Nonspe-
cific IgG binding was blocked by incubating sections with
SUPPRESSION OF FIBROSIS BY PPAR?
bovine serum albumin (0.1%) in PBS for 1 hour and then
incubating with a primary antibody for ?-SMA (1:1,000) in a
humidified chamber; the cultures were then left overnight at
4°C. Next, sections were incubated with biotinylated link for 30
minutes, followed by incubation with streptavidin for 30 min-
utes. The chromogen diaminobenzidine tetrahydrochloride
was then added until color development was deemed suffi-
cient, and sections were counterstained with Harris’ hematoxy-
Hydroxyproline assay. An hydroxyproline assay was
performed as a marker of collagen content in wound tissues,
using a method as previously described (13). Skin tissues were
homogenized in saline and hydrolyzed with 2N NaOH for 30
minutes at 120°C, followed by the determination of hy-
droxyproline content using a technique that was a modification
of the Neumann and Logan reaction, in which chloramine T
and Ehrlich’s reagent were used; results were compared
against a hydroxyproline standard curve, determined at
550 nm. Results of the hydroxyproline assay were expressed as
?g of hydroxyproline per mg of protein.
Real-time PCR. Real-time PCR to detect the expres-
sion of ?-SMA and type I collagen was performed essentially
as described previously (14,15). Dermal fibroblasts isolated
from explants of tissue from PPAR?-conditional control and
PPAR?-KO mice were cultured until reaching 80% conflu-
ence, and were serum starved for 24 hours. Cells were then
treated in the presence or absence of transforming growth
factor ?1 (TGF?1) (4 ng/ml) for 24 hours, and total RNA was
isolated (RNeasy; Qiagen, Chatsworth, CA). The integrity of
the RNA was verified by gel electrophoresis or Agilent bio-
analyzer (Agilent, Palo Alto, CA). Total RNA (25 ng) was
reverse transcribed and amplified using TaqMan Assays-on-
Demand (Applied Biosystems, Foster City, CA) in a 15-?l
reaction volume containing 2 unlabeled primers and
6-carboxyfluorescein–labeled TaqMan minor groove binder
probe. Samples were combined with One-Step MasterMix
(Eurogentec, Luik, Belgium). Amplified sequences were de-
tected using the ABI Prism 7900 HT sequence detector
(Applied Biosystems) according to the manufacturer’s instruc-
tions. Triplicate samples were run, and expression values for
?-SMA and type I collagen were standardized to the values
obtained with control 28S RNA primers, as determined using
the ??Ctmethod (16). Statistical analysis was performed using
Student’s paired t-test.
Effects of the PPAR? deletion on susceptibility to
bleomycin-induced skin thickness and collagen produc-
tion. To generate mice with deletion of PPAR? in
fibroblasts, we crossed mice harboring a PPAR? allele
bordered by loxP sites with mice containing a Cre-
Figure 1. Effects of conditional knockdown of peroxisome proliferator–activated receptor ? (PPAR?) in mouse fibroblasts. Mice homozygous for
loxP-PPAR? and heterozygous for a transgene driving a tamoxifen-dependent Cre-recombinase under the control of a fibroblast-specific type I
collagen promoter were injected with corn oil or tamoxifen. A, Tail DNA was genotyped by polymerase chain reaction to detect the Cre allele
(Cre[ER]T band), the wild-type floxed allele (PPAR? F/F band), or the allele containing deletion of PPAR? (PPAR? conditional knockout band)
after injection of corn oil or tamoxifen. B, Dermal fibroblasts isolated from mice with the PPAR? gene (PPAR? C) or from PPAR?-deficient mice
(PPAR? CKO) were tested for the presence of the PPAR? gene by indirect immunofluorescence analysis of cells using an anti-PPAR? antibody
(red). Cells were counterstained with 4?,6-diamidino-2-phenylindole (blue) to detect nuclei (original magnification ?40). C, Western blot analysis
of PPAR? in dermal fibroblasts from each group was performed with an anti-PPAR? antibody; ?-actin was used as the control. Cells from 4 different
mice per genotype were analyzed. Color figure can be viewed in the online issue, which is available at http://www.arthritisrheum.org.
2824KAPOOR ET AL
recombinase gene located downstream of a type I col-
lagen promoter/enhancer that confers fibroblast-specific
gene expression (12,17). The expression of Cre is depen-
dent on the presence of tamoxifen (12). Littermate mice
homozygous for the loxP-PPAR? that were heterozy-
gous for type I collagen–Cre were generated, and these
mice were treated with or without tamoxifen, as de-
scribed in Materials and Methods. As a result, mice with
the PPAR? deletion (PPAR?-KO mice) and control
mice that were otherwise genetically identical (PPAR?-
conditional control mice) were generated. Deletion of
the PPAR? gene was verified using PCR analysis of tail
DNA (Figure 1A), and was also verified using an
anti-PPAR? antibody in indirect immunofluorescence
and Western blot analyses of dermal fibroblasts cultured
from mouse tissue explants (Figures 1B and C).
To investigate the effect of the PPAR? deletion
on skin fibrosis, we injected PPAR?-conditional control
and PPAR?-KO mice with bleomycin for 2 weeks, 4
weeks, and 6 weeks to determine the degree of fibrosis
during the time course of bleomycin treatment. We
investigated histologically, using trichrome and H&E
staining, whether loss of PPAR? in the dermis altered
bleomycin-induced skin fibrosis. We found that
PPAR?-KO mice were more susceptible to bleomycin-
induced skin fibrosis compared with PPAR?-conditional
control mice throughout the time course of bleomycin
treatment (results at 4 weeks are shown in Figure 2;
additional results from 2 and 6 weeks are available from
the corresponding author upon request). We did not
observe any significant difference in the extent of fibro-
sis between PBS-treated PPAR?-conditional control
mice and PBS-treated PPAR?-KO mice during the
complete time course of treatment, indicating that
PPAR? does not appreciably affect normal skin.
PPAR?-KO mice exhibited enhanced dermal
thickness compared with PPAR?-conditional control
mice at weeks 2, 4, and 6 of bleomycin treatment (Figure
3A). Blinded histologic analysis of trichrome-stained
sections showed higher scores for collagen content in
Figure 2. Susceptibility of peroxisome proliferator–activated receptor ? (PPAR?)–deficient mice to bleomycin-
induced skin fibrosis. Mice without or with the PPAR? deletion (C and CKO, respectively) were treated with
bleomycin for 2, 4, and 6 weeks (results from week 4 are shown); phosphate buffered saline (PBS) was used as
the control. Trichrome staining was used to assess collagen content and dermal thickness. Representative results
from 4 separate animals/group are shown. (Original magnification ? 10.) Color figure can be viewed in the online
issue, which is available at http://www.arthritisrheum.org.
SUPPRESSION OF FIBROSIS BY PPAR?
bleomycin-treated PPAR?-KO mice compared with
PPAR?-conditional control mice throughout the time
course of bleomycin treatment (Figure 3B). Assessment
of collagen content using the hydroxyproline assay fur-
ther confirmed that animals deficient in PPAR? pos-
sessed elevated collagen levels when treated with bleo-
mycin over the entire time course of treatment (Figure
4). H&E-stained skin sections further showed increased
inflammation in PPAR?-KO mice compared with
PPAR?–conditional control mice in response to bleo-
mycin treatment (Figures 5A and B). Collectively, these
results indicate that loss of PPAR? in fibroblasts pro-
motes fibrogenic responses in the skin.
Figure 4. Enhanced collagen content in response to bleomycin-
induced skin fibrosis as shown by hydroxyproline levels in PPAR?-
deficient mice. Mice without or with the PPAR? deletion (control and
CKO, respectively) were treated with PBS or bleomycin for 2, 4, and 6
weeks. The hydroxyproline assay confirmed enhanced collagen content
in response to bleomycin treatment in PPAR?-deficient mice com-
pared with PBS- and bleomycin-treated control mice. ? ? P ? 0.05
versus PBS-treated control and PBS-treated PPAR?-deficient mice; ?
? P ? 0.05 versus bleomycin-treated control mice. Representative
data from 4 separate animals/group are shown. Bars show the mean ?
SD. See Figure 2 for definitions.
Figure 3. Enhanced dermal thickness and collagen content in re-
sponse to bleomycin-induced skin fibrosis in PPAR?-deficient mice.
Mice without or with the PPAR? deletion (control and CKO, respec-
tively) were treated with PBS or bleomycin for 2, 4, and 6 weeks.
A, PPAR?-deficient mice exhibited greater dermal thickness in re-
sponse to bleomycin treatment on weeks 2, 4, and 6 compared with
both PBS- and bleomycin-treated control mice. B, Blinded histologic
analysis of trichrome-stained sections was used to assess collagen
content in both groups of mice. Bleomycin-treated PPAR?-deficient
mice exhibited greater collagen content compared with both PBS- and
bleomycin-treated control mice. ? ? P ? 0.05 versus PBS-treated
control and PBS-treated PPAR?-deficient mice; ? ? P ? 0.05 versus
bleomycin-treated control mice. Representative data from 4 separate
animals/group are shown. Bars show the mean ? SD. See Figure 2 for
2826 KAPOOR ET AL
Association of loss of PPAR? with enhanced
?-SMA expression, Smad3 phosphorylation in response
to bleomycin, and sensitivity to TGF?1. Given that our
previous analyses had uncovered findings to show that
loss of PPAR? results in enhanced bleomycin-induced
cutaneous fibrosis, as was visualized by increased skin
thickness and collagen production in PPAR?-deficient
mice, we sought to ascertain whether loss of PPAR? also
promotes the ability of bleomycin to induce ?-SMA
expression and myofibroblast formation. Immunohisto-
chemical analysis showed greater expression of ?-SMA
in PPAR?-KO mice compared with PPAR?-conditional
control mice (Figure 6A). Western blot analysis of
protein samples prepared from bleomycin-treated ani-
mals, compared with PBS-treated animals, further con-
firmed that ?-SMA production was elevated in the
presence of bleomycin in PPAR?-deficient mice com-
pared with that in the respective control mice (Figure
6B). Moreover, elevated Smad3 phosphorylation was
observed in PPAR?-deficient animals in response to
bleomycin, indicating a potentiation of the profibrotic
TGF?1/Smad signaling pathway in the absence of
PPAR? (Figure 6B).
To investigate the effect of PPAR? deficiency on
TGF?1 signaling in fibroblasts, we stimulated dermal
fibroblasts isolated from PPAR?-conditional control
and PPAR?-deficient mice with TGF?1, and deter-
mined the expression levels of ?-SMA and type I
collagen. The TGF?1-mediated increase in expression
of ?-SMA and type I collagen was further potentiated in
PPAR?-deficient fibroblasts, indicating that the re-
sponse to TGF?1 in the absence of PPAR? in fibroblasts
is increased in this mouse model of cutaneous fibrosis
(Figures 6C and D).
In this study, we tested the effect of loss of
PPAR? in fibroblasts on the fibrotic responses in vivo.
We used mice homozygous for a PPAR? gene flanked
Figure 5. Enhanced inflammation in response to bleomycin treatment in PPAR?-deficient mice. A, Hematoxylin and eosin staining was used to
assess inflammation in response to bleomycin treatment, as compared with PBS treatment, in mice without or with the PPAR? deletion (C and CKO,
respectively) at 2, 4, and 6 weeks (results from week 4 are shown) (original magnification ? 10). B, Inflammation was scored on a scale of 0–3 as
described in Materials and Methods. Bars show the mean ? SD. PPAR?-deficient mice showed greater inflammation in response to bleomycin
treatment compared with PBS- and bleomycin-treated control mice. ? ? P ? 0.05 versus PBS-treated control and PBS-treated PPAR?-deficient
mice; ? ? P ? 0.05 versus bleomycin-treated control mice. Representative data from 4 separate animals/group are shown. See Figure 2 for
definitions. Color figure can be viewed in the online issue, which is available at http://www.arthritisrheum.org.
SUPPRESSION OF FIBROSIS BY PPAR?
by loxP sites and heterozygous for a transgene encoding
a tamoxifen-dependent Cre-recombinase driven by a
fibroblast-specific type I collagen promoter/enhancer
(12). The tissue specificity of this promoter/enhancer
construct has been confirmed in vivo (14). PPAR?-
deficient mice showed enhanced responsiveness to
bleomycin-induced fibrosis, as visualized by greater der-
mal thickness, increased collagen production, the ap-
pearance of ?-SMA–expressing myofibroblasts, and en-
hanced Smad3 phosphorylation. PPAR?-deficient
fibroblasts showed enhanced sensitivity to the TGF?1-
mediated increase in expression of ?-SMA and type I
collagen. A recent study also showed that loss of PPAR?
results in enhanced sensitivity to TGF?1 and increased
transcription of type I collagen (18). Collectively, our
results suggest that PPAR? normally suppresses fibro-
genesis in vivo.
Fibrotic diseases are characterized by the failure
to terminate normal tissue repair and the persistence of
myofibroblasts within lesions (4,9). Myofibroblasts can
form through mechanisms of cooperation among several
extracellular signaling molecules, including TGF?1,
ET-1, and CCN2, all of which act, at least in part,
through adhesive mechanisms (4,9). In this report, we
show that PPAR? normally suppresses fibrogenesis in
vivo, since loss of PPAR? in fibroblasts resulted in
enhanced fibrotic responses to bleomycin.
PPAR? agonists have been considered to be
viable therapies for treating a variety of diseases such as
diabetes (5,6). Our results showing that PPAR? is a
suppressor of myofibroblast fibrogenesis are a useful
step in identifying the fundamental processes underlying
normal tissue repair and fibrogenesis. Although it is
beyond the scope of our current study, our results
suggest that PPAR? agonists might also be considered
for use as a therapy to control the extent of the fibrosis
observed in SSc.
Our studies examining the involvement of
Figure 6. Enhanced myofibroblast formation and transforming growth factor ?1 (TGF?1) signaling in PPAR?-deficient mice. A, Immunohisto-
chemical analysis using anti–?-smooth muscle actin (anti–?-SMA) antibody showed a greater number of ?-SMA–expressing myofibroblasts
(arrows) in response to bleomycin treatment in PPAR?-deficient mice (CKO) compared with control mice without the PPAR? deletion (C) (results
from week 4 are shown; PBS was used as the control) (original magnification ? 40). B, Western blotting of protein extracts from paw tissue after
4 weeks of bleomycin treatment showed greater ?-SMA expression and phosphorylation of Smad3 in PPAR?-deficient mice treated with bleomycin
compared with untreated control mice. C and D, Dermal fibroblasts isolated from PPAR?-deficient mice (solid bars) and control mice (open bars)
were stimulated with TGF?1, and gene expression of ?-SMA and type I collagen (Col) was assessed by real-time polymerase chain reaction. The
TGF?1-mediated increase in ?-SMA and type I collagen expression was further potentiated in PPAR?-deficient mouse fibroblasts. Representative
data from 4 separate animals/group are shown. Bars show the mean ? SD. ? ? P ? 0.05 versus unstimulated control and unstimulated
PPAR?-deficient mice; ? ? P ? 0.05 versus TGF?1-stimulated control mice. See Figure 2 for other definitions.
2828 KAPOOR ET AL
PPAR? in dermal function may have profound implica- Download full-text
tions for understanding the pathologic processes in
cutaneous fibrosis, by contributing to our understanding
of the basic mechanisms of fibrogenesis. As a conse-
quence, our results could have future therapeutic impli-
cations in the treatment of fibroproliferative diseases
such as SSc.
All authors were involved in drafting the article or revising it
critically for important intellectual content, and all authors approved
the final version to be published. Dr. Leask had full access to all of the
data in the study and takes responsibility for the integrity of the data
and the accuracy of the data analysis.
Study conception and design. Kapoor, McCann, Liu, Denton,
Acquisition of data. Kapoor, McCann, Liu, Huh, Abraham.
Analysis and interpretation of data. Kapoor, McCann, Liu, Denton,
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SUPPRESSION OF FIBROSIS BY PPAR?