| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Short Communications |


From the Département danatomie et de biologie
cellulaire,*
Medical Research Council Group in Functional
Development and Physiopathology of the Digestive Tract; the
Département de pathologie,
and
the Département de chirurgie,
Faculté de médecine, Université de Sherbrooke,
Sherbrooke, Quebec, Canada
| Abstract |
|---|
|
|
|---|
1ß1
1) and
laminin-5 (
3ß3
2) are mainly expressed at the base of villus
cells, whereas laminin-2 (
2ß1
1) is restricted to the
bottom of the crypts. The expression of these molecules has not yet
been studied in Crohns disease (CD), but it could be
altered, in light of the important changes occurring in the
architecture of the crypt-villus axis under the active state of the
disease. To test this hypothesis, the expression of laminin
1,
2, and
3 subunits was analyzed in
control, inflamed, and corresponding uninflamed CD
small intestinal specimens by indirect immunofluorescence and reverse
transcriptase-polymerase chain reaction. Surprisingly,
1 and
3 remained strongly expressed by all villus cells, whereas
2, normally expressed in the bottom of the crypts in control
and uninflamed CD specimens, was lacking in inflamed CD
specimens. However, this loss of
2 expression was associated
with a significant up-regulation of both
1 and
3 expression in
the crypts of inflamed CD specimens. A significant up-regulation of the
1 subunit was also observed in the crypts of uninflamed CD
specimens. At the transcript levels,
1 was found
significantly higher in inflamed than uninflamed CD specimens. Taken
together, these observations identify important alterations in
laminin expression in the small intestine with CD and suggest that
compositional changes in the epithelial basement membrane may play a
role in this disease.
| Introduction |
|---|
|
|
|---|
The etiology of the disease remains incompletely understood but it is becoming more evident that interacting environmental and genetic factors are both of great importance.2,5 Another concept that has begun to receive considerable attention pertaining to intestinal inflammation is the involvement of essentially all cellular and acellular components of the mucosa, including immune cells and epithelial, mesenchymal, and endothelial cells, as well as the extracellular matrix (ECM), and that the dysfunction of any component of this intricate system may lead to a disruption in communication resulting in pathological inflammation.5
The importance of ECM molecules in the regulation of inflammation, including the recruitment and state of activation of leukocytes, has been clearly demonstrated in various systems.6-10 However, the information is still extremely limited for intestinal inflammation.11 Indeed, in contrast to the normal human intestine where the expression, location, and possible function of most ECM molecules, namely laminins, type IV collagens, fibronectins, and tenascin, as well as their receptors in the integrin family, have been determined,12,13 almost nothing is known about ECM composition and function in inflammatory bowel diseases.14
As a first step in investigating this question, we have chosen to focus
on laminins. Laminins represent a major component of all basement
membranes both quantitatively and functionally.15
The
members of this multigene family have been shown to mediate several
cellular activities, namely the promotion of adhesion, migration,
growth, and tissue-specific gene expression, depending on the laminin
and cell type studied.13,15,16
In the human small
intestine, three distinct laminins have been identified: laminin-1
(
1ß1
1) and laminin-5 (
3ß3
2), which are mainly expressed
at the base of villus cells, and laminin-2 (
2ß1
1), which is
restricted to the bottom of the crypts. In this study, the expression
and distribution of the three
chains specific to these laminins
have been analyzed in controls as well as in inflamed and uninflamed
mucosa from patients with Crohns disease, by indirect
immunofluorescence and reverse transcriptase (RT)-polymerase chain
reaction (PCR). Our observations identify major alterations in the
pattern of laminin expression in crypts of the small intestine with
Crohns disease and therefore support the hypothesis that ECM
molecules can participate in the chronic intestinal inflammation
cascade.
| Materials and Methods |
|---|
|
|
|---|
Eleven specimens of distal ileum with Crohns disease were available for the study. For each patient (five males and six females; ages 2240), samples from both inflamed and uninflamed (resection margin) areas were obtained, and the diagnosis was confirmed by a pathologist. Three of these patients received no treatment before surgery. Six control specimens obtained from the nondiseased part (at least 10 cm distant from lesions) of resected ileum for pathologies other than Crohns disease (bowel obstruction, primary lymphoma, or tumor) were also included in the study. All tissues were processed within 1 hour after surgery. The project was in accordance with a protocol approved by the Institutional Human Research Review Committee of the Université de Sherbrooke for the use of human material. The preparation and embedding of tissues for cryosectioning were performed as described previously.17,18
Indirect Immunofluorescence
Cryosections, 23 µm thick, were cut on a Jung Frigocut 2800N
cryostat (Leica Canada, Saint-Laurent, Canada) and fixed in methanol
(10 minutes, -20°C) for the detection of
1 (4C719
)
and
2 (5H2 and 2G919,20
) or in freshly prepared 2%
paraformaldehyde in phosphate-buffered saline (60 minutes, 4°C) for
the detection of
3 (BM221
). The secondary antibody was
Cy2-conjugated goat anti-mouse IgG (Amersham-Pharmacia, Baie dUrff,
Canada). Sections were stained with Evans blue (0.01% in
phosphate-buffered saline), mounted in glycerol:phosphate-buffered
saline (9:1) containing 0.1% paraphenylene diamine, and viewed with a
Reichert Polyvar 2 microscope (Leica Canada) equipped for
epifluorescence. In all cases, no immunofluorescent staining was
observed when primary antibodies were replaced by mouse nonimmune
serum.
RNA Extraction and RT-PCR
Total RNAs from the six available series of paired, inflamed and
uninflamed CD specimens were prepared by Clontechs Atlas Total RNA
Isolation protocol (Clontech, Palo Alto, CA) and stored in RNasecure
(Ambion, Austin, TX) at -80°C. First, strand complementary DNA
synthesis with Superscript II (Life Technologies, Inc., Burlington,
Canada) was performed on 5 µg total RNA by using
oligo(dT)12-18
(Amersham-Pharmacia) as primer. Conditions
for amplification of laminin
1 and
2 chains and S14, used as
endogenous control, have been described previously.22,23
For laminin
3 chain, we used the sense primer
5'-GGACCTCAACGTCGGTCA-3' and the antisense primer
5'-CAGGGATCCTCAGTGTCGTC-3', which amplified a 209-bp amplicon at
nucleotides 48145023 of laminin
3.24
Single-stranded
complementary DNA was amplified for 30 cycles of denaturation (1 minute
at 94°C) and annealing/extension (1 minute at 53°C and 1 minute at
72°C) in a thermal cycler (Perkin-Elmer DNA thermal cycler, Model
480, Foster City, CA) in the presence of 250 µmol/L
deoxyribonucleoside triphosphates and 2.5 U of Taq
polymerase (Qiagen, Mississauga, Canada).
| Results |
|---|
|
|
|---|
Chains along the Crypt-Villus Axis
The expression of the
1,
2, and
3 chains of laminin and
their distribution at the epithelial basement membrane along the
crypt-villus axis were determined by indirect immunofluorescence with
chain-specific monoclonal antibodies. In control specimens not affected
by CD, the
1 chain was uniformly detected in the villus, but it was
below the detection level in most crypts (Figure 1a)
as also noted for the
3 chain,
whereas the
2 chain was found to be confined to the lower half of
the crypts as previously observed.18,25
In uninflamed CD
specimens (resection margins), the normal histology of the ileal mucosa
was relatively well preserved (Figure 1, be)
, and the distribution of
the
2 and
3 chains was comparable to controls,
2 being
restricted to the bottom of the crypts (Figure 1d)
and
3 to the
villi (Figure 1e)
. However, in addition to its normal distribution in
the villus, the
1 chain was consistently found also in a large
proportion of the crypts, in most studied specimens (10 of 11),
according to a staining pattern ranging from the lower half of the
glands (Figure 1b)
to the entire gland (Figure 1c)
. In inflamed CD
specimens, the villi were short and wide, whereas the crypts were
irregular and generally exhibited a larger diameter (Figure 1, fh)
.
The
1 and
3 chains were found in the basement membrane of all
villi and also in a large proportion of crypts (Figure 1, f and h)
.
However, the
2 chain was not detected in these specimens (Figure 1g)
. As summarized in Figure 2, a
significant up-regulation of the
1 chain was observed in the crypts
of both uninflamed and inflamed CD specimens, whereas alterations in
the other laminin
chains were restricted to the crypts of inflamed
CD specimens, the
3 chain being significantly increased and the
2
chain being mostly undetectable (Figure 2)
.
|
|
Chain Transcripts in CD
Laminin
chain expression in CD was further investigated at the
transcript level by RT-PCR on 6 of the 11 specimens studied by indirect
immunofluorescence. As shown in Figure 3a
, the three laminin
chains were
found to be expressed in all CD specimens, including
2. Furthermore,
the relative amount of
1 mRNA was found to be significantly higher
in inflamed than uninflamed CD specimens, although the
2 and
3
transcript levels remained comparable, statistically (Figure 3b)
.
|
| Discussion |
|---|
|
|
|---|
chain expression. Indeed, the
1 and
1 chains,
which are shared by both laminin-1 and -2, have been found
constitutively expressed along the crypt-villus axis in the human small
intestine.18,26,27
A switch from laminin
2 to
1
chain expression would thus result in the expression of laminin-1
instead of laminin-2. Alternatively, because 4C7 (which is the only
antibody available for immunodetection of
1) may also recognize the
5 laminin chain,28
the expression of laminin-10
(
5ß1
1) in the human small intestine remains a possibility. The
expression of heterotrimeric
3ß3
2 laminin-5 in inflamed CD
crypts is supported by the extracellular deposition of the
3 chain
in the basement membrane (see Figure 1
2 chains (data not shown). However, because the
3 chain can
also complex with ß1, ß2, and
1, it cannot be excluded, at this
time, that a proportion of
3 is expressed as laminin-6
(
3ß1
1) and/or laminin-7 (
3ß2
1).29
The second particular feature observed in the small intestine of CD
patients is the expression of the laminin
1 chain in the crypts of
uninflamed segments, a phenomenon rarely observed in control specimens
from non-CD patients.18,26
It is interesting that, in most
of these specimens, the crypt staining for laminin-1 invariably
included the bottom of the glands (see Figure 1,b and c
), the site of
laminin-2 expression. This situation is reminiscent of that of the
fetus, in which laminin-1 and -2 are coexpressed in the developing
crypts.27
A third feature of potential pathological interest is the up-regulation
in the expression of the
1 transcript in the small-intestinal mucosa
of inflamed CD specimens. Increased production of ECM molecules in
inflammatory bowel diseases has been previously observed for type III
collagen30
and tenascin,31
a phenomenon that
seems to be related to an increased proliferation of various cellular
elements of the lamina propria, such as smooth muscle cells and
fibroblasts.4,11
The higher expression of the
1 chain
in the inflamed CD mucosa observed herein appears consistent with these
previous observations because
1, in contrast to
2 and
3, is
also expressed by nonepithelial cellular elements of the intestinal
mucosa, namely smooth muscle cells and blood vessels.18,25
Taken together, these observations raise two questions.
(a) What is the mechanism of alteration of laminin
expression in chronic inflammation? (b) What are the
functional consequences of laminin redistribution along the
crypt-villus axis? For the first question, cytokines and growth factors
are likely to play a central role. Indeed, as recently reviewed,
alteration in the profile of numerous cytokines, as well as growth
factors, is one of the hallmarks of intestinal
inflammation.11
As demonstrated with transforming growth
factor ß,32
these molecules can affect gene expression
in various cell types including epithelial cells and subepithelial
myofibroblasts, both responsible for various laminin chain
expression.23
The presence of elevated levels of matrix
metalloproteinases in regions of inflamed mucosa in Crohns disease
may also contribute to compositional changes in the basement
membrane.33
This latter possibility should be considered
for the laminin
2 chain, which disappears at the protein level as
shown by immunofluorescence, while its transcript remains normally
expressed. Cytokines could also be responsible for the higher
expression of laminin-1 in the crypts of histologically normal CD
mucosa, because the production of some, such as tumor necrosis
factor-
and interleukin-1ß and -6, also appears to be
abnormally elevated in uninvolved CD mucosal
biopsies.34
To the second question pertaining to the functional consequences of
alterations in laminin expression, it may be hypothesized that
replacement of laminin-2 by laminin-1 and -5 in crypts of inflamed CD
specimens, as well as coexpression of laminin-1 and -2 in the crypts of
uninflamed CD specimens, is of functional relevance, based on the
evidence that laminin-1 and -2 exhibit a distinct ability to modulate
intestinal cell-specific gene expression in
vitro.35
However, laminins mediate their effects
through membrane receptors, namely integrins. Many of the
laminin-binding integrins have been found to be expressed in the normal
small intestine, including
2ß1,
3ß1,
7Bß1, and
6ß4,17,22,36
which can bind differentially to
distinct laminins and mediate specific cell
functions.13,16
Further work will thus be required to
better delineate, at the cellular level, the functional implications of
laminin expression alteration.
| Acknowledgements |
|---|
| Footnotes |
|---|
Supported by Grants MT-11289 and GR-15186 from the Medical Research Council of Canada and grants from the Fonds pour la Formation des Chercheurs et lAide la Recherche.
Accepted for publication September 4, 1999.
| References |
|---|
|
|
|---|
7Bß1 expression in human intestinal cells and enterocytic differentiation. Gastroenterology 1997, 113:1510-1521[Medline]
3 chain of the adhesive ligand epiligrin: expression in wound repair. J Biol Chem 1994, 269:22779-22787
6-ß4 integrins subunits in the developing human and mouse intestine. Dev Dyn 1994, 201:71-85[Medline]
2,
3,
6, ß1 and ß4 subunits in the developing human small intestinal mucosa. Anat Rec 1995, 242:242-250[Medline]
5 chain and lack of laminin
1 chain during human muscle development and in muscular dystrophies. J Biol Chem 1997, 272:28590-28595
and ß in colonic mucosa in inflammatory bowel disease. Gastroenterology 1996, 110:975-984[Medline]
, interleukin-1ß, and interleukin-6 by morphologically normal intestinal biopsies from patients with Crohns disease. Gut 1996, 39:684-689This article has been cited by other articles:
![]() |
C. Francoeur, F. Escaffit, P. H. Vachon, and J.-F. Beaulieu Proinflammatory cytokines TNF-{alpha} and IFN-{gamma} alter laminin expression under an apoptosis-independent mechanism in human intestinal epithelial cells Am J Physiol Gastrointest Liver Physiol, September 1, 2004; 287(3): G592 - G598. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. A. Sanders and M. D. Basson Collagen IV regulates Caco-2 migration and ERK activation via {alpha}1{beta}1- and {alpha}2{beta}1-integrin-dependent Src kinase activation Am J Physiol Gastrointest Liver Physiol, April 1, 2004; 286(4): G547 - G557. [Abstract] [Full Text] [PDF] |
||||
![]() |
A C Y Li and R P H Thompson Basement membrane components J. Clin. Pathol., December 1, 2003; 56(12): 885 - 887. [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |