Download Intrahepatic expression of the hepatic stellate cell marker ®broblast

Liver 2002: 22: 93±101
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Copyright ß Blackwell Munksgaard 2002
Liver
ISSN 0106-9543
Intrahepatic expression of the hepatic
stellate cell marker ®broblast activation
protein correlates with the degree of ®brosis
in hepatitis C virus infection
Levy MT, McCaughan GW, Marinos G, Gorrell MD. Intrahepatic expression of the hepatic stellate cell marker ®broblast activation protein correlates
with the degree of ®brosis in hepatitis C virus infection.
Liver 2002: 22: 93±101. ß Blackwell Munksgaard, 2002
Abstract: Background: Activated hepatic stellate cells (HSCs), recognised by
their a smooth muscle actin immunoreactivity, are primarily responsible for
liver ®brosis. However, the presence of a smooth muscle actin positive HSCs
is not always associated with the development of liver ®brosis. Recently,
other markers of human HSCs including the gelatinase ®broblast activation
protein (FAP) and glial ®brillary acidic protein have been identi®ed. Aims:
We examined the relationship between the expression of these HSC markers
and the severity of liver injury in patients with chronic hepatitis C virus
infection. Methods: Liver tissue from 27 patients was examined using immunohistochemistry. Linear correlation analysis was used to compare
staining scores with the stage and grade of liver injury. Results±Conclusions:
FAP expression, seen at the tissue-remodelling interface, was strongly and
signi®cantly correlated with the severity of liver ®brosis. A weaker correlation was seen between glial ®brillary acidic protein expression and ®brosis
stage. This contrasted with the absence of a relationship between a smooth
muscle actin and the ®brotic score. A correlation was also observed between
FAP expression and necroin¯ammatory score. In summary, FAP expression
identi®es a HSC subpopulation at the tissue-remodelling interface that is
related to the severity of liver ®brosis.
The hepatic stellate cell (HSC) has an important
role in the pathogenesis of cirrhosis (1±7). In the
normal liver HSCs are quiescent, long-lived cells
that store vitamin A (4,8). Following liver injury,
HSCs undergo activation and transdifferentiation
to myo®broblast-like cells (4). Signi®cant functional changes accompany this phenotypic change
including alterations in extracellular matrix production and degradation. Unlike quiescent HSCs,
activated HSCs show intense cytoplasmic a
smooth muscle actin (SMA) immunoreactivity.
Abbreviations: HSC, hepatic stellate cell; HCV, hepatitis C virus;
FAP, ®broblast activation protein; SMA, smooth muscle actin;
GFAP, glial ®brillary acidic protein; PSC, perisinusoidal cell;
N-CAM, neural cell adhesion molecule.
Levy MT1, McCaughan GW1,
Marinos G2 and Gorrell MD1
1
A.W. Morrow Gastroenterology and Liver
Centre, Royal Prince Alfred Hospital, Centenary
Institute of Cancer Medicine and Cell Biology
and the University of Sydney, Sydney,
Australia; 2 Department of Gastroenterology,
Prince of Wales Hospital, Sydney, Australia
Key words: hepatic stellate cell ^ cirrhosis ^
hepatitis C ^ fibroblast activation protein ^
alpha smooth muscle actin ^ glial fibrillary
acidic protein
Dr Miriam Levy, Centenary Institute of Cancer
Medicine and Cell Biology, Locked Bag No. 6,
Newtown, NSW, 2042, Australia.
Tel: 61 2 9565 6156. Fax: 61 2 9565 6101.
e-mail: miriam-levy @ hotmail.com
Received 5 December 2000,
accepted 10 July 2001
This SMA expression has been used to identify
activated HSCs (9,10).
Transdifferentiation of the HSC to an SMApositive phenotype is not suf®cient to result in
®brosis. Activated SMA-positive HSCs are observed in liver diseases not associated with the
development of ®brosis, such as paracetamolinduced injury (11), hepatic ischaemia (12) and
acute liver rejection (9). This may be explained
by HSC apoptosis, which occurs in acute liver
injury after the injurious stimulus is withdrawn
(13). Thus, in acute liver injury, SMA-positive
HSCs may not persist for long enough to cause
®brosis. However, the length of time the SMApositive cells are present in the tissue may not be
the only relevant factor. In chronic liver diseases
such as chronic HCV infection, the majority of
patients have considerable numbers of activated
93
Levy et al.
SMA-positive HSCs, although only a minority
will develop cirrhosis (9,14).
Other markers of human HSCs have been identi®ed that may identify phenotypic subsets more
closely associated with the presence of ®brosis.
Recently, we reported ®broblast activation protein (FAP) expression on a subset of activated
human HSCs at the tissue-remodelling interface
of cirrhotic liver (15). FAP is a plasma membrane±bound atypical serine protease (16±19)
with both dipeptidyl-peptidase and gelatinase
catalytic activities (15,20). FAP is not expressed
in normal human tissue. FAP expression occurs in
circumstances of tissue remodelling such as the
granulation tissue of healing wounds, embryogenesis (18,21) and in the stroma of certain epithelial
cancers (21). In cirrhosis, FAP and SMA are both
markers of the activated HSC phenotype but are
not always coexpressed by the same cell. Signi®cant subsets of HSCs are either FAP single-positive or SMA single-positive (15).
This paper further examines the expression of
the FAP-positive HSC subset in chronic liver disease. We determined whether FAP-positive cells
were present in earlier stages of liver injury, where
there may be in¯ammation but not necessarily
®brosis. There appears to be no clear-cut relationship between the presence of SMA-positive HSCs
and hepatic ®brosis. We sought to con®rm these
data and determine whether FAP expression by
HSC correlates with the histological severity of
liver disease. To further characterise the HSC subpopulations, we also studied the expression of glial
®brillary acidic protein (GFAP), a recently described HSC marker (3), and whether GFAP
expression correlates with FAP or SMA expression or the severity of histological injury. We also
compared the expression of SMA, FAP and
GFAP with the nature of the in¯ammatory in®ltrate using T cell and macrophage markers.
Patients and methods
Liver tissue source
Portions of liver biopsies from patients with
chronic hepatitis C virus (HCV) infection were
frozen at 70 C for immunohistochemistry. Separate portions of these liver biopsies were formalin®xed and paraf®n-embedded for routine staining
with haematoxylin and eosin or Masson's trichrome. Additional samples were obtained from
three transplant donors and four HCV-positive
liver transplant recipient livers. Tissues were used
following the conclusion of routine diagnostic
procedures. The diagnosis of HCV was made
serologically using a second-generation enzymelinked immunosorbent assay for antibody to
94
HCV (22). Samples from 27 patients, 24 males
and 3 females, were analysed. The mean patient
age was 40.1 years + SD 8.3.
Immunohistochemistry
The anti-human FAP mAb (clone F19) (17), polyclonal rabbit anti-cow GFAP (DAKO, Santa Barbara, CA), mouse mAb to human aSMA (Sigma,
St Louis, MO) were used in the experiments.
Frozen sections were ®xed and stained as described previously, except that anti-Ig-horseradish
peroxidase (DAKO, Santa Barbara, CA) replaced
the biotin/streptavidin method (15). Samples from
27 patients were immunostained for FAP and
SMA, 18 were stained for CD3 and CD68 and 25
were stained for GFAP. The mouse mAb were
diluted follows: anti-human FAP at 1 : 5 (15),
anti-SMA at 1 : 50, anti-CD68 and anti-OKT3
(DAKO, Santa Barbara, CA) at 1 : 200. The rabbit
anti-bovine GFAP was used at 1 : 150. Horseradish peroxidase-conjugated rabbit anti-mouse Ig
and sheep anti-rabbit Ig were used at 1 : 50 dilutions. Appropriate negative control antibodies
were used.
Scoring hepatic necroinflammatory activity and fibrosis in
chronic hepatitis C
Independent pathologists reported the liver histopathology as part of the routine clinical investigation of the patients. Necroin¯ammatory activity
for the portal/periportal and lobular area and the
degree of ®brosis was scored as described by
Scheuer et al. (23) and outlined in Table 1.
Scoring hepatic immunoreactivity
Estimation of the number of immunoreactive
perisinusoidal cells (PSCs) was performed
according to the method of Schmitt-Graff et al.
(9). Hepatic parenchymal PSC numbers were analysed separately in the periportal, intermediate
and perivenular zones. Immunoreactivity was categorised by visual assessment as follows: 0 ˆ no
positivity; 1 ˆ staining of some PSCs occupying
approximately less than 1%; 2 ˆ staining of PSCs
occupying approximately 1±10%; 3 ˆ staining of
Table 1. Distribution of Scheuer scores in the 27 patients studied
Fibrosis stage
Portal/periportal
necroinflammatory
activity (grade)
Lobular activity
(grade)
0
1
2
3
4
2
1
10
10
7
14
3
2
5
0
2
9
16
0
0
Fibroblast activation protein expression and liver fibrosis
PSCs occupying approximately 10±30%; and 4 ˆ
staining of PSCs occupying more than 30% of
the sinusoidal region. Mesenchymal (®brous
septa and portal tract) cell numbers were categorised by visual assessment using the following
score: 0 ˆ no positivity; 1 ˆ positivity of less than
10% of mesenchymal cells; 2 ˆ positivity of
10±20% of mesenchymal cells; 3 ˆ positivity
of 30±50% of mesenchymal cells; 4 ˆ positivity
of greater than 50% of mesenchymal cells. The
SMA-positive vascular smooth muscle cells were
excluded from the scoring. For CD68 and CD3
positive cells, the total score was assessed by combining the parenchymal and the mesenchymal
scores, obtained as described for PSCs above.
Estimations of immunoreactive PSC numbers
were veri®ed independently by a second researcher. The investigators were blinded to the
results of the Scheuer score. Data were analysed
by linear correlation analysis using GraphPad
Prismt software (San Diego, CA). Analysis with
this method assumes that the variables re¯ect a
grouping of continuous variables. Results presented are the calculated r2 value (the fraction of
the y value that can be explained by the x value)
and the p value.
Results
Immunohistochemical localisation of FAP and SMA
FAP protein was detected in the hepatic parenchyma in 11 of 27 patients with chronic HCV
infection. The immunoreactivity was localised to
the portal/periportal interface and the ®brous
septa, particularly at areas of necroin¯ammation.
At higher magni®cation FAP staining was localised to individual HSCs. Staining in four patients
with stages 1±4 of ®brosis is shown in Fig. 1 as
representative examples. Endothelial and smooth
muscle cells in the walls of blood vessels were FAP
negative.
SMA protein was detected in the hepatic parenchyma in 20 of 27 patients with HCV infection.
SMA immunoreactivity was observed in HSCs
diffusely throughout the liver lobule. Unlike FAP
staining, there was no concentration of SMA
immunoreactivity in periportal regions. SMA
staining in four patients with stages 1±4 of ®brosis
is shown in Fig. 2. SMA-positive cells, but no FAP
positive cells, were noted around areas of steatosis
in some patients (Figs 3b and c). Parenchymal
tissue of the three normal livers was SMA negative
(Fig. 3a).
(a)
(b)
(c)
(d)
Fig. 1. Immunoperoxidase staining of FAP in four patients with stages 1 (A), 2 (B), 3 (C) and 4 (D) ®brosis. FAP positive cells were
observed in the perisinusoidal space and in the portal ®brous septa in patients with ®brosis stages 3 and 4 (C and D). The FAP
immunoreactivity scores of the periportal region were 0 in A and B and 4 in C and D. Immunoperoxidase staining is seen in brown with
blue Mayer's haematoxylin nuclear counterstaining. Original magni®cation 400.
95
Levy et al.
a
b
c
d
Fig. 2. Immunoperoxidase staining of SMA in four patients with stages 1 (A), 2 (B), 3 (C) and 4 (D) ®brosis (the same specimens as
presented in Fig. 1). SMA-positive cells were seen in the perisinusoidal space (A and D), in the walls of blood vessels (B) and within the
portal ®brous septa (C and D). The SMA immunoreactivity scores of the periportal region were 3, 0, 2 and 4 in sections A, B, C and D.
Immunoperoxidase staining is seen in brown with blue Mayer's haematoxylin nuclear counterstaining. Original magni®cation 400.
FAP was detected in the mesenchymal area
(the portal tracts and ®brous septa) in 19 of 27
patients. In this region SMA-positive cells were
detected in all 27 patients. The cells positive for
FAP or SMA had spindle-shaped cell bodies with
long processes consistent with the morphology of
myo®broblasts. In normal livers, some weakly
SMA-positive cells of ®brotic morphology were
seen in the portal tract (Fig. 3a).
Lack of correlation between FAP and SMA
immunoreactivities
As FAP and SMA are both HSC activation
markers, the relationship between the presence
of each antigen on HSCs was examined. Linear
correlation analysis of the periportal (r2 ˆ 0.05),
total parenchymal (r2 ˆ 0.01) and mesenchymal
(r2 ˆ 0.08) scores for FAP and SMA found no
signi®cant association between these two HSC
activation markers (Fig. 4).
Correlation of FAP and lack of correlation of SMA
immunoreactivities with the stage of hepatic fibrosis
The Scheuer (23) scores are listed in Table 1. Periportal FAP immunoreactivity was detected in 0/2,
96
1/10, 2/7, 3/3 and 5/5 patients with stage 0±4 liver
®brosis, respectively (Fig. 1). Linear correlation
analysis indicates that periportal FAP immunoreactivity was strongly correlated with the stage of
liver ®brosis (r2 ˆ 0.77, p < 0.0001) (Fig. 5). In
contrast, SMA staining was present in some
cases and not others, independent of the degree
of ®brosis. Linear correlation analysis indicates
that periportal SMA staining was detected in 1/2,
8/10, 5/7, 3/3 and 3/5 with stage 0±4 liver ®brosis,
respectively (Fig. 2). There was no relationship
between periportal SMA expression and the
stage of liver ®brosis (r2 ˆ 0.001) (Fig. 5). Correlation coef®cients comparing the total parenchymal scores or the mesenchymal scores with the
degree of liver ®brosis were similarly signi®cant
for FAP and non-signi®cant for SMA, respectively (Table 2).
Correlation of FAP and lack of correlation of SMA
immunoreactivities with the necroinflammatory score and
patterns of CD3 and CD68 expression
We considered it possible that HSC activation,
using FAP or SMA as a marker, correlates with
the degree of necroin¯ammatory activity or the
extent of CD3 (T cell) or CD68 positive (macro-
Fibroblast activation protein expression and liver fibrosis
4
(a)
FAP score
3
2
1
0
0
1
2
3
4
SMA score
(b)
Fig. 4. Correlation of the FAP and SMA scores. Column scatter
plots showing the periportal SMA immunoreactivity score (xaxis) and the periportal FAP score (y-axis) for each patient.
FAP score
(a) 4
3
2
1
(c)
0
0
1
2
3
4
Fibrosis score
SMA score
(b)
4
3
2
1
Fig. 3. Immunoperoxidase staining of SMA in normal liver (A)
and of SMA (B) and FAP (C) in a patient with marked steatosis
associated with chronic HCV infection (stage 1, grade 1). In
normal liver, SMA immunoreactivity was seen in the walls of
blood vessels only. A patient with chronic HCV infection and
marked steatosis had SMA-positive HSCs around the regions of
steatosis, whereas FAP was not expressed in this region.
Immunoperoxidase staining and Mayer's haematoxylin counterstaining. Original magni®cation 400.
Fig. 5. Correlation of FAP and SMA expression with the stage of
hepatic ®brosis. Column scatter plots showing the periportal
FAP (A) and SMA (B) immunoreactivity scores for each patient
grouped according to the stage of liver ®brosis.
phage/Kupffer cell) cell in®ltrates. Periportal FAP
immunoreactivity was detected in 0/1, 2/10, 7/14
and 2/2 patients with portal±periportal necroin¯ammatory activity, grades 0±3, respectively.
Linear correlation analysis showed that FAP immunoreactivity was positively correlated with the
grade of necroin¯ammatory activity (r2 ˆ 0.23,
p ˆ 0.011). In contrast, SMA staining was
observed in the majority of patients with HCV
infection. Periportal SMA staining was detected
in 0/1, 8/10, 10/14 and 2/2 patients with grades 0±3
portal±periportal necroin¯ammatory activities,
respectively. There was no relationship between
the level of periportal SMA expression and the
grade of necroin¯ammatory activity (r2 ˆ 0.04).
Similar correlation coef®cients were obtained
comparing whole FAP and SMA scores with
grade of necroin¯ammatory activity. Eighteen
0
0
1
2
3
4
Fibrosis score
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Levy et al.
Table 2. Correlation coefficients and their statistical significance
FAP
SMA
GFAP
Stage of fibrosis
Grade of necroinflammation
Macrophage infiltrate
T cell infiltrate
r2
p
r2
p
r2
p
r2
p
Periportal/periseptal
parenchymal score
Total parenchymal score
Total mesenchymal score
0.77
< 0.0001
0.23
0.011
0.03
0.49
0.03
0.52
0.54
0.58
< 0.0001
< 0.0001
0.08
0.12
0.14
0.07
0.006
0.06
0.75
0.34
0.09
0.04
0.23
0.42
Periportal/periseptal
parenchymal score
Total parenchymal score
Total mesenchymal score
0.001
0.83
0.04
0.36
0.03
0.48
0.03
0.49
0.04
0.002
0.34
0.79
0.008
0.009
0.65
0.62
0.02
0.03
0.60
0.46
0.02
0.003
0.60
0.43
0.18
0.03
0.002
0.81
0.004
0.8
0.06
0.32
0.03
0.11
0.42
0.13
0.00
0.14
0.96
0.097
0.06
0.10
0.32
0.81
0.004
0.003
0.8
0.90
Periportal/periseptal
parenchymal score
Total parenchymal score
Total mesenchymal score
p < 0.05 is considered significant (significant values highlighted in bold).
liver biopsies were immunostained for CD3 and
CD68. CD3 positive T cells were seen within the
portal and periportal areas. CD68 positive cells
were seen in the portal tracts and throughout
the liver parenchyma. There were no associations
between the levels of FAP or SMA staining and
the proportion of CD3 or CD68 positive cells
(Table 2).
GFAP immunoreactivity and comparisons with FAP
immunoreactivity, SMA immunoreactivity and the stage of
fibrosis
Parenchymal GFAP immunoreactivity was observed in 10 of 25 patients studied. Positive cells
were within the mesenchymal areas and in the
periportal perisinusoidal space. GFAP positive
cells were only rarely noted within the liver lobule
beyond the periportal rim. Periportal GFAP immunoreactivity was detected in 1/2, 0/10, 3/7, 2/3
4/5 with stage 0±4 liver ®brosis, respectively. Mesenchymal GFAP immunoreactivity was more
common than periportal GFAP immunoreactivity
and was seen in 22 of the 25 patients studied.
GFAP positive cell staining was usually present
in up to 30% of the cells of the portal tract or
®brous septa. There was a weak but signi®cant
correlation between the immunoreactivity of
GFAP and the immunoreactivity of FAP
(r2 ˆ 0.29, p ˆ 0.005) and the ®brosis score
(r2 ˆ 0.18, p ˆ 0.03) but not the immunoreactivity
of SMA (Table 2).
Discussion
The HSC has a central effector role in the
pathogenesis of liver ®brosis and cirrhosis. Recent
discoveries of the expression by HSC of neuronal
98
and glial cell markers are intriguing and suggest a
possible neural crest origin of HSC (15,24±27).
FAP is one such marker, being found on glial
and other cell lines (28). FAP expression coincides
with tissue remodelling in humans in cirrhosis
(15), healing wounds (18), embryogenesis (29),
and tumour stroma (29) and in tadpole tail resorption (30). FAP is a cell surface, proline-speci®c
dipeptidyl peptidase and gelatinase (15,19,20,31)
located at the tissue-remodelling interface in cirrhotic human liver (15). These properties suggest a
functional role for FAP in the pathogenesis of
liver disease. The present study strengthens this
argument by showing a strong correlation between the severity of ®brosis and the extent of
FAP expression in hepatitis C. In addition, in the
portal±periportal region, FAP expression correlated with necroin¯ammatory activity. In contrast
to FAP, the correlation of GFAP expression with
®brosis severity was weak. Furthermore, there was
no correlation between ®brosis severity and the
HSC antigen SMA.
There is evidence of a distinct cell population
associated with ®brosis at the tissue-remodelling
interface. Collagen mRNA in situ studies in patients with primary biliary cirrhosis demonstrate
that most collagen mRNA production occurs in
cells having a similar portal/periportal location as
the FAP positive cells we observed (32). In that
study the SMA-positive, collagen mRNA-positive
cells were considered to be portal ®broblast in
origin, based solely on their morphology.
Interpretation of SMA expression by immunohistochemical analysis is hampered by differences
in localising SMA expression by different investigators. This probably relates to variation in assay
sensitivity between laboratories. In general, when
Fibroblast activation protein expression and liver fibrosis
SMA is not detected in normal liver, HSCs of the
cirrhotic liver have low or no detectable expression
in the lobule and high-level expression in the
®brous septa (9,15,33). In contrast, when SMA is
detected in normal liver HSCs, the expression in
HSCs of cirrhotic liver is much more extensive
(34,35). In the present study, SMA was not
detected in HSCs of normal liver. In contrast to
SMA expression in normal liver and in contrast to
FAP expression in chronic HCV infection, signi®cant numbers of SMA-positive HSCs were
detected throughout the liver in the majority of
patients with chronic HCV infection. Their prevalence was not associated with ®brosis severity.
Concordant with our study, previous studies
found that most patients have large numbers of
SMA-positive HSCs in chronic HCV infection
(9,14). Furthermore, cross-sectional analysis in
orthotopic liver transplant recipients with chronic
HCV re-infection showed no relationship between
numbers of SMA-positive HSCs and the presence
of cirrhosis (36). However, in that study, patients
with the greatest numbers of periportal SMApositive HSCs early post-transplant were more
likely to have developed cirrhosis at follow-up
(36). SMA-positive cell numbers have been positively correlated with the extent of ®brosis in patients with HCV infection in just one study (33).
The mechanism of HSC activation to a SMApositive phenotype remote from the site of injury
may be via soluble factors such as cytokines (36) or
submicroscopic injurious events perhaps induced
by the hepatitis C virus itself.
Other studies of HSC phenotypes in experimental and human chronic liver diseases also suggest a
distinct HSC phenotype in the vicinity of the developing ®brous septa. Neural cell adhesion molecule (N-CAM) is not detected in the hepatic
parenchyma of normal rat liver, but in chronic
liver disease is expressed by a subpopulation of
activated HSCs at the scar±parenchyma interface
(26). Similarly, nestin is expressed by a subpopulation of HSCs in a similar location in a rat model of
®brosis (37). Like HSCs, the expression levels of
the antigens FAP, N-CAM, GFAP and nestin by
neuroglial cells vary depending upon the state of
cellular differentiation or activation (38±43). In
contrast, synaptophysin expression is constitutive
in neural cells (44), and expression is used to measure synaptic density. Synaptophysin positive HSC
numbers are increased in pathological conditions
compared to normal livers although the degree of
difference was not described (25). Further investigation is required to determine whether synaptophysin is a useful marker of total HSC numbers
(25,44).
FAP positive cells were topographically located
near the regions of portal/periportal necroin¯ammatory activity and these two parameters correlated,
suggesting
that
stimulators
of
necroin¯ammatory change might also induce
FAP expression by HSCs. However, there was
no association between FAP expression and the
proportion of CD3 positive or CD68 positive cells,
probably because the necroin¯ammatory score
largely measures the degree of interface hepatitis
and not the in¯ammatory in®ltrate (23). In addition, variations in the nature of host immune
responses, which may be re¯ected in cytokine pro®les rather than absolute numbers of in¯ammatory cells, probably regulate both FAP expression
and ®brotic responses to chronic HCV infection
(45). Alternatively, other stimuli associated with
the interface hepatitis may regulate FAP expression, such as lipid peroxidation by-products (46)
released by necrosing hepatocytes (47). Variations
between portal tracts in chronic HCV infection
suggest that using serial sections in follow-up
studies would be helpful. Examination of other
non-®brotic liver disease controls would help to
con®rm that the expression of FAP is a marker of
®brogenesis and not in¯ammation.
The role of FAP expression on HSCs is currently
unknown. The dipeptidyl peptidase function of
FAP, like DPP IV, may regulate the biological
activities of certain chemokines and hormones
(16,19,48±50). The gelatinase activity (15,20) may
contribute to the damage±repair cycle that characterises ongoing ®brosis, by degrading normal
basement membrane/extracellular matrix in the
sinusoidal space, resulting in further HSC activation. Alternatively, FAP may be upregulated
in response to the deposited collagen for the purpose of clearance of the ®brotic scar. This question
requires further investigation using the FAP de®cient mouse (51) and speci®c enzyme inhibitors.
We anticipate that a speci®c FAP enzyme inhibitor would be antagonistic of the ®brotic process.
This paper establishes a strong relationship between the expression of FAP and the severity of
hepatic ®brosis in chronic HCV infection. Along
with biochemical studies of FAP function, these
data add weight to the assertion that FAP has a
role in the pathogenesis of chronic liver disease.
Acknowledgements
We are grateful for the provision of liver sections by Charles
Harvey and Tony Freeman, and to Dr Wolfgang Rettig of
Boehringer Ingelheim Pharma KG for the antibody to FAP.
The National Health and Medical Research Council of
Australia provided a scholarship to MTL and grant number
142606 to GWM and MDG.
99
Levy et al.
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