Invasive depth of extravillous trophoblast correlates with cellular phenotype: a comparison of intra- and extrauterine implantation sites

During intrauterine human placentation, extravillous trophoblast invades uterine tissues starting with proliferating stem cells at the basement membrane of anchoring villi. Transition to the postproliferative invasive phenotype takes place several cell layers distant. Here we show that in intrauterine pregnancies invasive trophoblast comprises three cellular phenotypes: a. Small spindle-shaped trophoblast cells are found along the whole invasive pathway throughout pregnancy. They are embedded in little heterogeneous extracellular matrix but expose only fibronectin receptors (integrins alpha5beta1, alphavbeta3/5), resulting in a partial integrin-matrix mismatch. b. Large polygonal trophoblast cells are rare in early pregnancy but increase in number towards term. They secrete ample heterogeneous extracellular matrix and expose integrins specifically matching the opposing matrix molecules (integrins alpha6beta4, alpha5beta1). c. Multinucleated giant cells in all stages of pregnancy form a kind of peripheral shell of trophoblast. In contrast to intrauterine pregnancies, in viable tubal pregnancies, Mib-1 expression indicating proliferation, extends deeply into the invasive pathway. Trophoblast cells of the invasive pathway mostly belong to the small spindle-shaped phenotype and secrete little extracellular matrix, mainly fibronectins. At the transition to the second cellular layer of cell columns expression of integrin alpha6beta4 switches to expression of alpha5beta1 and alphavbeta3/5. Viable tubal pregnancies are characterised by a broad overlap of proliferative with invasive phenotype as well as a general integrin-matrix mismatch. The differences in proliferation patterns, cellular phenotype and matrix-integrin co-localisation may well explain the increase of invasiveness of normal extravillous trophoblast from term intrauterine via early intrauterine to viable tubal pregnancies.

TNF-alpha disruption of lung endothelial integrity: reduced integrin mediated adhesion to fibronectin

Tumor necrosis factor-alpha (TNF-alpha) causes an increase in transendothelial protein permeability of confluent monolayers of calf pulmonary artery endothelial (CPAE) cells, and the addition of plasma fibronectin (pFn) to the culture medium can attenuate this increase in permeability. We determined if reduced integrin function had a role in decreased endothelial cell adhesion to immobilized Fn after exposure of the endothelial monolayers to TNF-alpha. TNF-alpha also causes a reorganization of the subendothelial Fn rich matrix and a significant loss in RGD-dependent adhesion of TNF-alpha treated CPAE cells to pFn coated surfaces. However, flow cytometry revealed no decrease in alpha(5)beta(1) or total beta(1) integrin expression on the surface of the CPAE cells after TNF-alpha. Reduced CPAE adhesion to immobilized Fn was, in part, due to a loss of beta(1)-integrin function since the beta(1)-integrin blocking antibody mAb 13 significantly (P < 0.05) prevented the adhesion of normal control CPAE cells but did not further reduce the adhesion of TNF-alpha-treated cells. In addition, antibodies which activate beta(1) integrins restored (P < 0.05) adhesion of TNF-alpha-treated cells to immobilized pFn but did not alter the adhesion of control cells. Despite reduced ability to adhere to immobilized Fn, TNF-alpha-treated CPAE monolayers demonstrated increased binding and incorporation of fluid-phase pFn into the subendothelial extracellular matrix (ECM) as measured by the analysis of the deoxycholate (DOC) detergent insoluble pool of (125)I-Fn in the cell layer. In contrast to the RGD-mediated adhesion of CPAE cells to matrix Fn, the increased binding of soluble pFn after TNF-alpha was not inhibited by RGD peptides or mAb 13. Thus reduced integrin-dependent adhesion of the CPAE cells to matrix Fn as well as disruption of the Fn matrix may contribute to the increased protein permeability of previously confluent endothelial monolayer after TNF-alpha. In addition, increased ability for the monolayer to incorporate fluid-phase Fn into the ECM after TNF-alpha via a non-beta(1)- integrin dependent mechanism may be a compensatory response to stabilize the Fn matrix and the endothelial barrier.

Adhesion of a chondrocytic cell line (USAC) to fibronectin and its regulation by proteoglycan

BACKGROUND

Chondrocytes produce various extracellular matrices during chondrogenesis. Fibronectin and proteoglycan are major extracellular matrix proteins in cartilage tissue, but the interactions between them are not clear.

METHODS

Recently, we succeeded in establishing a cell line (USAC) with phenotypes of chondrocytes from a human osteogenic sarcoma of the mandible. Using this cell line, cell adhesion to fibronectin, the effect of proteoglycan on the cell adhesion and expression of integrin alpha5beta1 were investigated.

RESULTS

Cells immediately adhered to fibronectin and then spread. Proteoglycan inhibited cell adhesion to fibronectin dose-dependently, whereas collagen did not. The expression of both mRNAs of alpha5 and beta1 subunits was detected 12 h after treatment with proteoglycan, but the expression of beta1 subunit mRNA had diminished by 24 h after treatment.

CONCLUSIONS

These findings suggest that proteoglycan might modulate signal transduction from fibronectin by decreasing the expression of alpha5beta1 integrin.

Effects of growth factors and extracellular matrix on survival of human airway smooth muscle cells

Airway remodeling complicates longstanding asthma. It is characterized by an increase in the number of airway smooth muscle cells (SMCs) as well as an increase in and alteration of the type of extra-cellular matrix (ECM) in the airways. Although the number of SMCs in the airways depends on the balance of cell proliferation and cell death, studies to date have concentrated on factors affecting SMC proliferation. Here we report the first study on airway SMC survival factors: these cells receive a strong survival signal, which is not dependent on the known growth factor mitogens. We identified the ECM factors fibronectin, laminin, and collagens I and IV as important anti-apoptotic elements, and characterized the expression of the ECM receptors (integrins) on cultured SMC. Functionally blocking antibody and peptide studies revealed the alpha(5)beta(1) integrin to be an important transducer of the ECM-derived survival signal in these cells. Confocal microscopy confirmed the striking effects that discrete ECM factors have on SMC phenotype, notably the cytoskeleton. In summary, our data improves the understanding of the mechanisms underlying airway remodeling by outlining the key survival factors for airway SMC and by highlighting the impact of the cell-matrix interactions on cell death and phenotype.

Expression of the alphavbeta6 integrin promotes migration and invasion in squamous carcinoma cells

The integrin alphavbeta6 is a fibronectin receptor whose expression is not detectable on normal oral epithelium but is increased significantly in healing and in oral epithelial dysplasia and oral squamous cell carcinoma, suggesting it may promote changes associated with tumor development. To study whether alphavbeta6 may drive invasive behavior we have used transfection and retroviral infection to create a panel of epithelial cell lines expressing various levels of alphavbeta6. We report that increased expression of alphavbeta6 in malignant keratinocytes promotes invasion and leads to an increased capacity for migration towards fibronectin. alphavbeta6 expression may have a significant role in contributing to the malignant behavior of epithelial cells.

Integrin expression, enterocyte maturation, and bacterial internalization

BACKGROUND

Little is known about the molecular mechanisms involved in the translocation of enteric bacteria. Adhesion molecules mediate interactions between some enteric pathogens and mammalian cells, but no such interactions have been identified for enterocytes and normal enteric bacteria. Using enteric pathogens, adhesion molecule expression has been linked to bacterial internalization and to enterocyte differentiation. Therefore, experiments were designed to study enterocyte integrin expression and differentiation, as well as enterocyte internalization of Salmonella typhimurium, Proteus mirabilis, and Escherichia coli.

MATERIALS AND METHODS

Relative expression of the alpha2, alpha3, and beta1 integrin subunits on Caco-2 and HT-29 enterocytes (mature and immature) was measured by ELISA. Bacteria-enterocyte surface interactions were observed by light and scanning electron microscopy. Bacterial internalization by enterocytes was quantified using the gentamicin protection assay.

RESULTS

Expression of the alpha2, alpha3, and beta1 integrin subunits was consistently increased in immature compared to mature Caco-2 enterocytes; however, compared to mature enterocytes, immature HT-29 enterocytes had similar expression of alpha3 and beta1 but decreased alpha2. Compared to untreated mature enterocytes, bacterial internalization was increased in immature enterocytes as well as mature enterocytes with lateral membranes artifactually exposed. However, there was no difference in bacterial internalization between immature enterocytes and mature enterocytes treated to expose the lateral membrane.

CONCLUSIONS

Bacterial internalization by enterocytes appeared to be due to factors other than integrin expression or enterocyte differentiation. Exposure of the lateral enterocyte membrane may play an important role in facilitating bacterial internalization by enterocytes.

In multiple myeloma, only a single stage of neoplastic plasma cell differentiation can be identified by VLA-5 and CD45 expression

The nature of the proliferating fraction in myeloma is still not known and understanding the characteristics of this fraction is central to the development of effective novel therapies. However, myeloma plasma cells typically show a very low rate of proliferation and this complicates accurate analysis. Although the level of CD45 and/or VLA-5 has been reported to identify proliferating 'precursor' plasma cells, there are discrepancies between these studies. We have therefore used a rigorous sequential gating strategy to simultaneously analyse cycle status and immunophenotype with respect to CD45, VLA-5 and a range of other integrin molecules. In 11 presentation myeloma patients, the proliferative fraction was distributed evenly between CD45+ and CD45- cells, however, cycling plasma cells were consistently VLA-5-. There was close correlation between the expression of VLA-5 and a range of other integrin molecules (CD11a, CD11c, CD103), as well as the immunoglobulin-associated molecules CD79a/b (Spearman, n = 10, P < 0.0001). In short-term culture, cells that were initially VLA-5-showed increasing VLA-5 expression with time. However, simultaneous analysis of the DNA-binding dye 7-amino-actinomycin D demonstrated that this was not as a result of differentiation, as VLA-5+ plasma cells were all non-viable. This was confirmed in freshly explanted plasma cells from nine patients. Discrete stages of plasma cell differentiation could not be distinguished by the level of CD45 or VLA-5 expression. The results indicate that there is a single stage of plasma cell differentiation, with the phenotype CD38+CD138+VLA-5-. These findings support the hypothesis that neoplastic bone marrow plasma cells represent an independent, self-replenishing population.

Effect of lipopolysaccharide on the morphology and integrin immunoreactivity of ramified microglia in the mouse brain and in cell culture

Microglial cells form the first line of defense in brain infection. They are related to monocytes and macrophages and can be readily activated by cell wall components of bacteria such as lipopolysaccharides (LPS). In the present study, we explored the effect of this endotoxin in mouse on the morphology of microglia and their immunoreactivity for the integrin family of cell adhesion molecules in vitro and in vivo. Subcutaneous injection of LPS led to a dose-dependent activation of alpha M beta 2-positive microglia, with a saturating effect at 1 microg LPS in the blood-brain barrier deficient area postrema, at 10 microg in the directly adjacent tissue, and at 100 microg throughout the brainstem and cerebellum. Morphologically, this activation was characterized by the swelling of the microglial cell body, a thickening of the proximal processes, and a reduction in distal ramification. Microglial immunoreactivity for the integrins alpha 4 beta 1, alpha 5 beta 1, alpha 6 beta 1, and alpha M beta 2 was strongly increased. In vitro, ramified microglia were obtained using a coculture on top of a confluent astrocyte monolayer. Two days exposure to LPS resulted in a morphological activation of the cultured cells with an increase of the integrin immunoreactivity for alpha 5 (5.7-fold), alpha 4 (3.1-fold), beta 1 (2.3-fold), and alpha M (1.5-fold), and a decrease in the alpha 6-staining intensity by 39%. Even a sublethal dose of LPS (3 mg in vivo and 500 microg/ml in vitro, respectively) did not induce the phagocyte-associated integrin alpha X beta 2 (CD11c/CD18, p150,95) and did not lead to a morphological transformation of the ramified microglia into phagocytes.

[Presence of alpha 5 beta 1 integrin and fibronectin in the anterior subcapsular cataract]

PURPOSE

We investigated whether alpha 5 beta 1 integrin and fibronectin were present in myofibroblast-like lens epithelial cells in anterior subcapsular cataract (ASC).

METHODS

Nine anterior capsule specimens were obtained from the patients during cataract surgery and frozen for cryostat sections. Six specimens were anterior capsule obtained from cataract with ASC. As a control, three specimens were obtained from cataract without ASC. Alpha-smooth muscle actin (alpha-SMA), alpha 5 beta 1 integrin, and fibronectin were detected by immunohistochemical observation.

RESULTS

In all 6 specimens from patients with ASC, the lens epithelial cells around fibrosis tissue included myofibroblast-like lens epithelial cells which were positive for alpha-SMA. alpha 5 beta 1 integrin was detected in these lens epithelial cells. Fibronectin was also detected around these myofibroblast-like lens epithelial cells. Three control specimens showed no immunoreactivity against alpha-SMA, alpha 5 beta 1 integrin, or fibronectin.

CONCLUSIONS

Alpha 5 beta 1 integrin and fibronectin may play an important role in myodifferentiation of lens epithelial cells.

The interleukin-6 receptor alpha-chain (CD126) is expressed by neoplastic but not normal plasma cells

Interleukin-6 (IL-6) is reported to be central to the pathogenesis of myeloma, inducing proliferation and inhibiting apoptosis in neoplastic plasma cells. Therefore, abrogating IL-6 signaling is of therapeutic interest, particularly with the development of humanized anti-IL-6 receptor (IL-6R) antibodies. The use of such antibodies clinically requires an understanding of IL-6R expression on neoplastic cells, particularly in the cycling fraction. IL-6R expression levels were determined on plasma cells from patients with myeloma (n = 93) and with monoclonal gammopathy of undetermined significance (MGUS) or plasmacytoma (n = 66) and compared with the levels found on normal plasma cells (n = 11). In addition, 4-color flow cytometry was used to assess the differential expression by stage of differentiation and cell cycle status of the neoplastic plasma cells. IL-6R alpha chain (CD126) was not detectable in normal plasma cells, but was expressed in approximately 90% of patients with myeloma. In all groups, the expression levels showed a normal distribution. In patients with MGUS or plasmacytoma, neoplastic plasma cells expressed significantly higher levels of CD126 compared with phenotypically normal plasma cells from the same marrow. VLA-5(-) "immature" plasma cells showed the highest levels of CD126 expression, but "mature" VLA-5(+) myeloma plasma cells also overexpressed CD126 when compared with normal subjects. This study demonstrates that CD126 expression is restricted to neoplastic plasma cells, with little or no detectable expression by normal cells. Stromal cells in the bone marrow microenvironment do not induce the overexpression because neoplastic cells express higher levels of CD126 than normal plasma cells from the same bone marrow in individuals with MGUS. (Blood. 2000;96:3880-3886)

Immunofluorescent microscopic investigation of the distal arrector pili: a demonstration of the spatial relationship between alpha5beta1 integrin and fibronectin

Currently there is limited knowledge regarding the anatomy of the distal arrector pili (AP) muscle. A previous study implicated fibronectin and alpha5beta1 integrin binding as the anchor between the AP and the extracellular matrix (ECM). The purpose of this study was to strengthen this hypothesis. Serial frozen sections of human scalp skin were double-labeled via immunofluorescent staining for alpha5beta1 with fluorescein and fibronectin with rhodamine, followed by fluorescent microscopy. Granular staining for alpha5beta1 with fluorescein and smooth staining for fibronectin with rhodamine were seen at the periphery of the AP muscle bundles and along the distal fibers. Precise co-localization of alpha5beta1 and fibronectin was observed at the AP-ECM interface by means of a dual filter. Analysis of variance was used on the relative density of staining for each epitope. Staining for both epitopes was significantly brighter at the distal fibers than at the middle or proximal portions of the muscle. A computerized three-dimensional reconstruction provides a detailed picture of the microanatomy of the distal AP, which allows mathematical evaluation of the forces of contraction. The anatomic co-localization between alpha5beta1 and fibronectin strengthens our hypothesis that interaction of these epitopes mediates the attachment of the distal AP to the ECM.

Integrin expression in oral hairy leukoplakia and normal tongue epithelium

OBJECTIVE

To describe the expression of integrins in the epithelium of oral hairy leukoplakia (HL) and compare to that of normal lateral tongue epithelium.

MATERIALS AND METHODS

Immunohistochemistry to identify integrins (alpha 2, alpha 3, alpha 5, alpha 6, alpha v, beta 1) was performed, using a standard biotin-streptavidin-peroxidase technique on five clinically and histologically confirmed frozen biopsy specimens of HL and five normal lateral tongue control tissues.

RESULTS

Expression of integrins alpha 2, alpha 3, alpha 6, alpha v, beta 1 was seen both in HL epithelium and in normal control tissue. alpha 5 expression was not seen in HL or in control tissue epithelium. alpha 2 and alpha 3 were expressed mainly in the basal and suprabasal layers; alpha 6 expression was most intense on the basal surface of the basal cells, alpha v was expressed in the basal and suprabasal layers with more expression seen in the higher differentiated cell layers than the other integrins. beta 1 expression was seen in the basal and suprabasal layers only. No apparent difference between HL and normal oral mucosa was noted in the staining pattern of the various integrins.

CONCLUSION

Integrins alpha 2, alpha 3, alpha 6, alpha v, beta 1 are expressed in HL and the expression pattern is not different from that of normal oral mucosa. alpha 5 is not expressed in HL or in normal oral epithelium.

Cytomegalovirus-infected neuroblastoma cells exhibit augmented invasiveness mediated by beta1alpha5 integrin (VLA-5)

Previously, experimental in vivo results showed that the productively and persistently human cytomegalovirus (HCMV)-infected neuroblastoma cell line UKF-NB-4AD169 exhibits a more malignant phenotype than the non-infected variant UKF-NB-4. To prove the assumption that enhanced malignancy may be due to enhanced invasive potential of the infected cells we studied interactions of both lines with monolayers of cultured endothelial cells. UKF-NB-4AD169 cells adhered to and transmigrated through endothelial monolayer to a significantly higher extent compared with UKF-NB4. Furthermore, the adhesion of UKF-NB-4AD169 but not of UKF-NB4 resulted in focal disruption of the monolayer integrity which facilitates tumor cell transmigration. Blocking antibodies directed against the beta1 integrin chain as well as beta1alpha5 on the tumor cells specifically inhibited adhesion in a concentration-dependent manner. When UKF-NB-4 were pretreated with a beta1 integrin activating antibody, focal disruption of the endothelial integrity also occurred. These findings lead us to suggest that HCMV infection activates beta1alpha5 in the host neuroblastoma cell which in turn enables these cells to tightly adhere to endothelial cells. In the presence of the protease inhibitor phenantroline, beta1alpha5-mediated adhesion was not impaired whereas UKF-NB4AD169-mediated endothelial monolayer permeabilization was dose dependently inhibited. We conclude that human cytomegalovirus infection contributes to augmented neuroblastoma invasiveness via adhesion of activated beta1alpha5 and subsequent matrix digestion by proteases.

Expression of fibronectin receptor, integrin alpha 5 beta 1 of hepatic stellate cells in rat liver fibrosis

OBJECTIVE

To investigate the role of fibronectin (FN) receptor alpha 5 beta 1 in liver fibrosis.

METHODS

Northern blot analysis and immunohistochemical techniques were used to observe changes in the expression of FN and FN receptor alpha 5 beta 1 on hepatic stellate cells (HSCs) in vivo and in vitro of rat liver fibrosis induced by CCl4.

RESULTS

(1) alpha 5 beta 1 was mainly detected in the endothelia and some of the desmin(DM) positive cells of the sinusoids in normal rat liver. The expression of alpha 5 beta 1 of DM positive cells detected by immunohistochemistry reached its peak at the 10th week of the experiment. The changes in FN expression were similar to that of alpha 5 beta 1. (2) The expression of FN, alpha 5 and beta 1 mRNAs in the experimental group was remarkably increased especially at the 6th week, compared to that of normal liver specimens. The expression of the three mRNAs of HSCs in vitro isolated from the experimental group (6 weeks) was higher than those from normal liver. (3) The expression of FN, alpha 5 and beta 1 mRNAs increased in normal rat HSCs after treatment with transforming growth factor-beta 1 (TGF-beta 1) for 2 hours. After 4 hours of treatment, the expression of the three mRNAs fell to levels similar to the control group. Immunocytochemistry revealed that the expression of alpha 5 beta 1 of HSCs reached its peak after 4 hours of treatment with TGF-beta 1 and dropped to normal 2 hours later.

CONCLUSION

These data suggest that HSCs normally express FN receptor alpha 5 beta 1. The activation of HSCs during liver fibrogenesis leads to an increase of FN, alpha 5 and beta 1 mRNA expression. The expression of FN and alpha 5 beta 1 of HSCs in vitro is up-regulated by TFG-alpha 5 beta 1. The detection of gene transcription of FN and its receptor by Northern blot analysis suggests the activation and proliferation of HSCs and thereby provides a sensitive signal of liver fibrosis.

The microanatomy of the distal arrector pili: possible role for alpha1beta1 and alpha5beta1 integrins in mediating cell-cell adhesion and anchorage to the extracellular matrix

The arrector pili (AP) muscle is a small band of smooth muscle that attaches proximally to the bulge area of the pilosebaceous apparatus in the reticular dermis and extends up toward the epidermis. The distal anatomy of the AP and the anchorage mechanism allowing hair erection have not been previously described. Integrins are likely candidates mediating this attachment. Immunohistochemical techniques were used to determine the distribution of the following integrins: alpha1, alpha2, alpha3, alpha4, alpha5, alpha6 and beta1 as well as fibronectin. Frozen human scalp tissue was sectioned in traditional planes, obliquely and horizontally to visualize microanatomy in three dimensions. Histological examination revealed that the distal portions of smooth muscle fibers splay extensively between collagen bundles of the upper dermis. Integrin subunits alpha1, alpha5 and beta1 were expressed by the AP muscle. Analysis of the relative density of immunoreactivity in digitized sections revealed increased alpha5 subunit expression at the extracellular matrix (ECM)-muscle interface. These data suggest that anchorage of the AP muscle to the ECM is via alpha5beta1 integrin and alpha1beta1 integrin functions in muscle cell-cell adhesion. Extensive splaying of smooth muscle fibers may allow increased surface area contact between the ECM and smooth muscle cells expressing peripherally situated alpha5 integrin.

Immunocytochemical localization of a cell adhesion molecule, integrin alpha5beta1, in nerve growth cones

It is well-known that nerve growth cones, the growing tips of nerves, play a central role in determining the direction taken by regenerating peripheral nerves though neurotropism and contact guidance. In order to identify the molecules expressed on growth cones that are responsible for contact guidance, we investigated the possible involvement of integrins as sensors for the extracellular matrix. In cultured rat PC-12i cells and chick dorsal root ganglion cells, we found that integrin alpha5beta1 was concentrated in the filopodia and central regions of the growth cones. These integrin alpha5beta1-rich regions corresponded well with the sites where the growth cones came into contact with and adhered to the extracellular matrix. Integrin alpha5beta1 has been reported to bind with fibronectin in the extracellular matrix. When examined by triple staining and confocal laser scanning microscopy, we found that the distribution of integrin alpha5beta1 in the growth cones was very similar to that of actin filaments. Integrin alpha5beta1 was also expressed by Schwann cells. On immuno-electron microscopy, integrin alpha5beta1 was also identified in regenerating axons in vivo. These results suggest that integrin alpha5beta1 expressed on growth cones may function as a sensor for the extracellular matrix and Schwann cells, and thus mediate functionally important interactions in the development and regeneration of peripheral nerves.

Oxidative stress affects cytoskeletal structure and cell-matrix interactions in cells from an ocular tissue: the trabecular meshwork

The trabecular meshwork (TM) is a specialized eye tissue that regulates the aqueous humor outflow and controls intraocular pressure. Cells in this tissue are essential for maintenance of the outflow system. Disturbance of the TM cell status by insults such as oxidative stress may lead to elevation of the intraocular pressure and development of glaucoma. In the present study, we investigated the effect of oxidative stress on the adhesion of human TM cells to extracellular matrix (ECM) proteins. Treatment with 1 mM of H2O2 for 10 or 30 min did not affect cell viability, whereas the adhesion of TM cells to fibronectin, laminin, and collagen types I and IV was significantly reduced. Phalloidin and immunostaining also revealed reorganization of actin and vimentin structures. The level of integrins alpha5beta1, alphavbeta3, and beta1 was not altered, although the distribution of paxillin and focal adhesion kinase in focal contacts was reduced. Concomitantly, the level of transcription factor NF-kappaB was enhanced by the H2O2 treatment. Nuclear extracts of the treated cells also contained a heightened NF-kappaB binding activity. These changes persisted for up to 6 h after the H2O2 treatment but were partially recovered by 24 h. We concluded that under sublethal oxidative stress conditions, the TM cell adhesion to the ECM was impaired. The short-term loss of cell-matrix adhesiveness may be related to the rearrangement of cytoskeletal structures. Extensive and repeated oxidative stress in vivo may result in reduced TM cell adhesion, leading to cell loss, compromised TM integrity, and pathologic consequences.

Overexpression of alpha1-6 fucosyltransferase in hepatoma cells suppresses intrahepatic metastasis after splenic injection in athymic mice

Changes in oligosaccharide structures alter the biological functions of cancer cells. Alpha1-6 fucosyltransferase (alpha1-6FucT) catalyzes the transfer of fucose to the innermost GlcNAc in N-glycans. Although alpha1-6FucT is barely detected in normal liver, it is enhanced during rat hepatocarcinogenesis and in human hepatoma. To understand the biological meaning of the alpha1-6FucT in hepatoma, especially in terms of metastasis, we established human hepatoma cell lines, which express high levels of alpha1-6FucT by transfection of the alpha1-6FucT gene and investigated intrahepatic metastasis after splenic injection to athymic mice. Tumor formation in the liver was dramatically suppressed in the alpha1-6FucT transfectants (1 of 9 and 1 of 10 in alpha1-6FucT transfectants versus 6 of 9 and 6 of 9 in controls). Although there were no differences in terms of cell invasiveness to a Matrigel or in terms of cytotoxicity to interleukin 2-treated lymphocytes between alpha1-6FucT transfectants and control cells, cell adhesion to mice hepatocytes and nonparenchymal liver cells in culture was significantly inhibited in alpha1-6FucT transfectants, compared to the controls. Attachment of alpha1-6FucT transfectants to a fibronectin-coated dish was decreased compared to controls because alpha5beta1 integrin was more strongly alpha1-6 fucosylated in the alpha1-6FucT transfectants. Two-dimensional electrophoresis followed by lectin blot showed that certain glycoproteins (Mr 50,000-150,000, pI 4.8-5.5) were alpha1-6 fucosylated and might be linked to suppression of intrahepatic metastasis. This is the first demonstration of the biological significance of alpha1-6 fucosylation on N-glycans in hepatoma cells under in vivo conditions.

Expression of VLA-integrins and their related basement membrane ligands in gingiva from patients of various periodontitis categories

Periodontitis is characterized by destruction of dento-gingival fibers and apical migration of the junctional epithelium. Tissue destruction may be associated with altered interactions between epithelium and connective tissue mediated by integrins localized in the basement membrane zone. We examined the expression of alpha2beta1, alpha3beta1, alpha4/alpha5/beta1, alpha6beta4 and their related extracellular matrix (ECM) ligands: laminin-1, laminin-5, and collagen type IV in untreated periodontitis sites of various categories. The expression and location of ECM proteins along the basement membrane were found to be similar between clinically healthy and periodontitis affected tissues. However, ECM proteins were more diffusely distributed in connective tissue (CT) of periodontitis tissues as streak-like/ fibrillar/granular stainings, particularly beneath the pocket epithelium (PE) and around the blood vessels. This may reflect an increase in inflammatory cell migration. The more widespread distribution of integrins alpha2beta1, alpha3beta1 in PE of periodontitis specimens may be related to disease activity and increased rate of keratinocyte proliferation and migration. Moreover, the weaker expression of alpha6beta4 in junctional epithelium (JE) of periodontitis affected tissues may be related to the epithelial detachment from the tooth surface. Clarification of expressions of integrins and their ligands in relation to known clinical disease susceptibility factors may provide information on the onset and progression mechanisms of periodontal disease destruction.

Characteristic matrix and tubular basement membrane abnormalities in the CBA/Ca-kdkd mouse model of hereditary tubulointerstitial disease

CBA/CaH-kdkd mice develop hereditary tubulointerstitial disease with mononuclear cell infiltration and cyst formation, possibly representing a model of human nephronophthisis. The purpose of the present investigation was to examine the components of the fibrotic changes which typically develop in the kidneys of these mice. By conventional histology, kdkd mice displayed progressive interstitial fibroblast and matrix accumulation. Immunohistological analysis of kdkd kidneys showed marked deposition of fibronectin in the tubulointerstitial space and revealed prominent irregularities for laminin and collagen type IV in the tubular basement membrane (TBM), including thickening, widening and folding. Electron microscopy confirmed the TBM abnormalities and showed marked undulation and thickening in areas of proximal tubular (PT) degeneration. Immunofluorescence staining analysis for the fibronectin receptors VLA-4 and VLA-5 showed no expression on injured proximal tubules, whereas the expression of the laminin receptor VLA-6 was increased and irregular on altered PT. Analysis of RNA derived from kdkd kidneys revealed marked upregulation of steady-state mRNA levels for the fibrogenic growth factor TGF-beta. We conclude that TBM alterations, matrix accumulation and changes in integrin expression together with enhanced TGF-beta production are typical features of kdkd tubulointerstitial disease and suggest that characteristic TBM or matrix alterations could contribute to the pathogenesis of the disease in these mice.

[The role of beta1 integrins in renal failure accompanied by multiple myeloma]

Clinical features of multiple myeloma are linked with immunological phenotype of myeloma cells. The interactions between malignant plasma cells and proteins of ECM (extracellular matrix) or different cells results from the influence of adhesion molecules. In our study the expression of CD49b, CD49d, CD49e, CD49f on the myeloma cells has been estimated. These cells were obtained from bone marrow of 33 just diagnosed patients. Immunophenotyping was performed with flow cytometry method. Malignant plasma cells were identified by monoclonal antibody anti-CD138 (B-B4) directed against Syndecan-1. We have observed that in patients with high expression of laminin receptors CD49b, CD49f and lack of fibronectin receptors CD49d, CD49e more often renal failure has been confirmed.

Polarity, integrin, and extracellular matrix dynamics in the postischemic rat kidney

Acute renal failure (ARF) as a consequence of ischemic injury is a common disease affecting 5% of the hospitalized population. Despite the fact that mortality from ARF is high, there has been little improvement in survival rates over the last 40 years. The pathogenesis of ARF may be related to substantial changes in cell-cell and cell-extracellular matrix interactions mediated by beta1-integrins. On the basis of in vitro and in vivo studies, reorganization of beta1-integrins from basal to apical surfaces of injured tubular epithelia has been suggested to facilitate epithelial detachment, contributing to tubular obstruction and backleak of glomerular filtrate. In this study, we examine integrin and extracellular matrix dynamics during epithelial injury and repair using an in vivo rat model of unilateral ischemia. We find that, soon after reperfusion, beta1-integrins newly appear on lateral borders in epithelial cells of the S3 segment but are not on the apical surface. At later times, as further injury and regeneration coordinately occur, epithelia adherent to the basement membrane localize beta1 predominantly to basal surfaces even while the polarity of other marker proteins is lost. At the same time, amorphous material consisting of depolarized exfoliated cells fills the luminal space. Notably, beta1-integrins are not detected on exfoliated cells. A novel finding is the presence of fibronectin, a glycoprotein of plasma and the renal interstitium, in tubular spaces of the distal nephron and to a lesser extent S3 segments. These results indicate that beta1-integrins dramatically change their distribution during ischemic injury and epithelial repair, possibly contributing to cell exfoliation initially and to epithelial regeneration at later stages. Together with the appearance of large amounts of fibronectin in tubular lumens, these alterations may play a significant role in the pathophysiology of ARF.

The response of periodontal ligament cells to fibronectin

Fibronectin (fn) is an extracellular matrix (ECM) molecule important in cell adhesion and migration and in wound healing. It is also likely important in periodontal ligament (PDL) cell-ECM interactions, and thus in regenerating periodontal tissues. In this study we characterized PDL cells and their interactions with FN, testing different PDL cell isolates taken from healthy and diseased conditions. PDL cells were characterized by their morphology, integrin profile, motility, and bone nodule formation. Cells were then assayed for adhesion, proliferation, and chemotaxis in response to FN or FN fragments. Cell isolates were morphologically heterogeneous and fibroblastic, had a normal-appearing actin cytoskeleton and a wide range of migration potentials, and formed bone-like nodules in vitro. They expressed alpha5, beta1, alpha v, and alpha4 integrin subunits, known receptors for FN, and in fact they bound FN preferentially at 5 and 10 microg/ml. Intact FN induced greater PDL cell proliferation and chemotaxis than did FN fragments (120-kDa cell-binding, 60-kDa heparin-binding, and 45-kDa collagen-binding). PDL cells harvested from diseased and healthy conditions were no different on the basis of these assays. These data demonstrate that PDL cells are a mixed population of fibroblastic cells, capable of forming a mineralized matrix. They also suggest that maximal proliferation and chemotaxis require specific FN domains that are present on the intact molecule but not its fragments.

Adhesion of mature polyploid megakaryocytes to fibronectin is mediated by beta 1 integrins and leads to cell damage

Human CD34+ bone marrow cells were committed to the megakaryocytic lineage in serum-free liquid cultures by the following cytokines: thrombopoietin, erythropoietin, and IL-6. Megakaryocyte maturation has been described as being regulated by the extracellular matrix. These cells express receptors for laminin, collagen, and vitronectin, but they selectively adhere to and spread on fibronectin, a major component of the bone marrow environment. Function-perturbing antibodies against beta 1 integrins totally abolished the adhesion of megakaryocytes on fibronectin, whereas antibodies to beta 3 did not, suggesting that beta 1 integrins were responsible for the adhesive phenotype of these polyploid cells. beta 1-positive clusters were visualized in close contact with the extremities of stress fibers at the cell surface. In the course of cell spreading, we observed morphological modifications such as the disorganization of the compact nuclei structure and the appearance of holes in the cytoplasm leading to the release of alpha IIb beta 3-positive cellular fragments. This process appeared to be a specific feature of megakaryocytes and is correlated neither to apoptosis nor to integrin signaling.

Integrin alpha5beta1: a potent inhibitor of experimental lung metastasis

The integrin alpha5beta1 seems to be the most relevant receptor of tumor cells for binding to fibronectin. Although numerous studies suggest a role of tumor cell fibronectin interaction in tumor metastasis, differential integrin expression on tumor cells has, however, not been correlated with metastatic capabilities. We addressed this question by transfection of the integrin alpha5beta1 cDNA into HT-29 human colon carcinoma cells which led to de novo expression of functional integrin alpha5beta1. Similar to other reports, expression of the integrin alpha5beta1 in HT-29 tumor cells exerted an inhibitory action on cell proliferation as indicated in our study by formation of fewer colonies in soft agar. The tumor growth inhibitory property of the integrin alpha5beta1 was also shown by reduction of subcutaneous xenograft growth in nude mice to approximately 50% of that of control transfectants. For the first time, we found that several clones of integrin alpha5 subunit transfectants displayed dramatically reduced formation of lung colonies and cutaneous metastasis after intravenous injection into nude mice. While most animals inoculated with control transfectant cells formed macroscopically visible lung colonies ranging from 12.6 +/- 2.6 to 22.0 +/- 6.6 (mean colony number +/- SEM), mice inoculated with HT-29 cell clones expressing the integrin alpha5beta1 were almost completely free of lung colonies (ranging from 0.0 +/- 0 to 0.2 +/- 0.1). Our results imply that integrin alpha5beta1 expression inhibits circulating tumor cells in pursuing late steps of the metastatic process as represented by the artificial metastasis (lung colonisation) model.

Entamoeba histolytica contains a beta 1 integrin-like molecule similar to fibronectin receptors from eukaryotic cells

Entamoeba histolytica trophozoites do interact with extracellular matrix components in order to invade and finally destroy tissue. An important step in this interaction involves the binding of a 140-kDa membrane protein that binds to fibronectin. The similarity of this amoebic receptor to fibronectin receptors from higher eukaryotic cells was defined by indirect immunofluorescence, western blot and immunohistochemistry, using polyclonal monospecific antibodies raised against the amoebic protein. These results suggest that lower eukaryotic cells have and use a beta 1 integrin-like molecule as well as mechanisms similar to those present in higher eukaryotic cells during interaction with extracellular matrix components.

Inhibition of vascular smooth muscle cell growth by inhibition of fibronectin matrix assembly

The regulation of vascular smooth muscle cell (VSMC) proliferation by the fibronectin matrix was tested by treating human umbilical artery smooth muscle cells (HUASMCs) with a recombinant fragment of fibronectin (protein III1-C) that has previously been shown to modulate fibronectin matrix assembly. III1-C inhibited HUASMC proliferation by 75% to 90%. The inhibition of growth was time dependent; III1-C had no effect on DNA synthesis after 0 to 5 hours of treatment but did have an effect at 24 hours and beyond. III1-C did not stimulate apoptosis in these cells, indicating that the inhibition of proliferation was not due to an induction of programmed cell death. The effects of III1-C on cell growth were only specific for normal diploid smooth muscle cells. III1-C had no effect on the proliferation of IMR-90 fibroblasts, endothelial cells, NIH 3T3 cells, or the rat aortic smooth muscle cell line A7r5. However, III1-C did inhibit proliferation by primary rat aortic smooth muscle cells. An analysis of HUASMC fibronectin receptor (integrin alpha5beta1) distribution revealed that III1-C did not inhibit alpha5beta1 localization to focal contacts. Moreover, III1-C had no effect on the relative expression levels of seven different integrin subunits on HUASMCs. However, III1-C did inhibit fibronectin matrix assembly by rat aortic smooth muscle cells, HUASMCs, A7r5 cells, IMR-90 cells, and endothelial cells. An analysis of fibronectin synthesis indicated that the inhibition of fibronectin matrix assembly by III1-C was not due solely to a decrease in fibronectin synthesis. Finally, treatment of HUASMCs with anti-fibronectin monoclonal antibody L8 (which is known to inhibit fibronectin matrix assembly) also decreased the rate of HUASMC DNA synthesis. These results demonstrate that III1-C inhibits VSMC proliferation and suggest that this effect may be mediated by the inhibition of fibronectin matrix assembly.

Expression of beta 1 integrins (very late antigens-4 and -5) on myeloma cells and clinical correlates in patients with multiple myeloma

beta 1 Integrins are considered to be essential for the differentiation of bone-marrow B cells through an interaction with fibronectin-expressed bone-marrow stromal cells. The expression of very late antigens-4 (VLA-4) and -5 (VLA-5) by CD38bright bone-marrow cells in patients with multiple myeloma was measured by flow cytometry using specific monoclonal antibodies. The percentage of CD38bright bone-marrow cells appeared to correlated with that of bone-marrow plasma cells as judged by examination of bone-marrow smears (r = 0.911, P < 0.0001). Expression of VLA-4 and VLA-5 by CD38bright cells varied between patients, but the expression of VLA-4 was always equal to or greater than that of VLA-5. The ratio of VLA-4 to VLA-5 expression (VLA-4:VLA-5 ratio) was calculated and compared with the clinical features of the myeloma patients. A high VLA-4:VLA-5 ratio (> 2.0) was associated with the presence of plasmacytomas and urinary Bence-Jones protein was more common in this group. No other correlations between the clinical features of the disease and the expression of beta 1 integrins were found.

Different expression of adhesion molecules on myeloid and B-lymphoid CD34+ progenitors in normal bone marrow

The expression of adhesion molecules was studied on B lymphoid and myeloid CD34+ precursors in normal bone marrow. Bone marrow aspirates were labelled in a double fluorescence procedure with the CD34 monoclonal antibody 43A1 and with antibodies directed against maturation and differentiation antigens and adhesion molecules. Three clusters of CD34+ cells could be distinguished by their light scatter characteristics in flow cytometry. The population with the lowest forward scatter contained B-lymphoid precursors while the two others showed phenotypic characteristics of, respectively, early and late myeloid precursors. Nearly all CD34+ cells in the 3 subpopulations expressed VLA-4, VLA-5, LFA-3 and H-CAM. B-lymphoid progenitors showed a higher density of VLA-4 and VLA-5 than the myeloid progenitors. Myeloid precursors, and particularly the late subset, expressed more HCAM than the B-lymphoid progenitors. The majority of the CD34+ cells also expressed LFA-1 and L-selectin. Higher numbers of positive cells were found in the myeloid subset. The early myeloid subset showed the highest positivity for L-selectin. We conclude that B lymphoid and early and late myeloid CD34+ precursors in normal bone marrow show a different profile of adhesion molecules. These profiles could reflect a higher tendency of the myeloid CD34+ precursors to circulate.

Integrin adhesion molecules in the endometrial glandular epithelium in patients with endometriosis or adenomyosis

OBJECTIVE

To assess the role of beta 1-integrin and E-cadherin molecules in the eutopic glandular epithelium in patients with endometriosis or adenomyosis.

STUDY DESIGN

Twenty-four patients with endometriosis, and 22 patients with adenomyosis diagnosed histologically were selected as subjects. The controls consisted of 29 fertile women. Eutopic endometria were obtained by curettage or immediately after the operation. The samples were immunohistochemically examined for the expression of very late activation antigen-2 (VLA-2), VLA-3, VLA-4, VLA-5, VLA-6, and E-cadherin.

RESULTS

The expression of each VLA molecule and E-cadherin except VLA-4, VLA-5, and VLA-6 was significantly increased throughout the menstrual cycle in endometria in both the endometriosis and adenomyosis groups. In contrast, the expression of VLA-4 in the adenomyosis group was significantly reduced in the secretory phase.

CONCLUSION

Altered expression of beta 1-integrins and E-cadherin was observed throughout the menstrual cycle in patients with endometriosis and adenomyosis, suggesting the defective microenvironment of the endometrium.

Inhibition of smooth muscle cell migration by the p21 cyclin-dependent kinase inhibitor (Cip1)

In vascular smooth muscle cells (SMCs), proliferation and migration contribute to lesion formation after arterial injury. In the cell cycle, several cyclin-dependent kinases (cdks) inhibitors are implicated in the regulating of cyclin-cdk activity such as p21Cip1, p16Ink4 and p27Kip1. Although Cip1 inhibits SMC proliferation, its effects on SMC migration are unknown. To test the hypothesis that Cip1 inhibits SMCs migration and proliferation, we transfected the Cip1 gene into a strain of rabbit aortic SMCs (SM3 cells). Both the spreading and the attachment of Cip1-transfected SM3 cells to extracellular matrices (ECMs) were inhibited compared to that of vector-transfected cells. In the modified Boyden's chamber assay the effect of fibronectin on the migratory activity of Cip1-transfected SM3 cells was significantly less than that of vector transfected cells in response to PDGF-BB. These data suggested that Cip1 inhibited both the migration and proliferation of SMC.

Analysis of extracellular matrix proteins in malignant chicken cell lines

The adherent chicken cell line, MDCC-MSB1-41C, was highly transplantable and metastatic in vivo, compared with the parental non-adherent cell line MDCC-MSB1 from Marek's disease (MD) lymphoblastoid tumor. For clarification of differences in extracellular matrix proteins in MSB1-41C and MSB1 cells, examination was made of various components of extracellular matrix proteins. A detachment experiment indicated the protein(s) recognizing the Arg-Gly-Asp (RGD) sequence, the minimum structure required for recognition by the cell-surface receptors, is essential for the adherent character. Immunoblot assay using antibodies showed increased expression of fibronectin, fibronectin receptors, and vinculin on MSB1-41C cell lines. RGD-directed integrins mediate important cell-cell adhesive interaction and these interactions with extracellular matrix proteins may thus possibly be requisite for migration, proliferation and metastatic dissemination of MDCC-MSB1-41C cells. The RGD-containing peptide in the culture medium could cause detachment of cultured adhesive lymphoid leukosis LSCC-1104X5 cells from the dish too.

Endometrial integrin expression is independent of estrogen or progestin treatment in vitro

OBJECTIVE

To examine the regulation of endometrial integrin expression by estrogens and progestins in vitro.

DESIGN

Immunocytochemical study.

SETTING

Academic research unit.

PATIENT(S)

Twenty-five regularly cycling women without endometrial pathology, of whom seven had endometriosis.

INTERVENTION(S)

Endometrial cells obtained by aspiration curettage were treated with diethylstilbestrol, promegestone, and antiprogestin. Immunocytochemistry was performed with antibodies directed against integrins alpha 1 beta 1, alpha 2 beta 1, alpha 4 beta 1, alpha 5 beta 1, alpha v beta 3, and beta 3 integrin subunit.

MAIN OUTCOME MEASURE(S)

Semiquantitative staining score.

RESULT(S)

Endometrial cells express several integrins in vitro in a consistent and cell specific pattern. Neither differences between treated and untreated cells nor an effect of treatment duration or dosage were observed. Cells from patients with and without endometriosis showed similar patterns.

CONCLUSION(S)

The cellular distribution of integrin expression was similar to that described in vivo. In contrast, a steroid regulated expression could not be detected in vitro. Rather, a derepression by a factor not included in our model could be responsible for the cyclic appearance of some integrins. In endometriosis, no fundamental difference of integrin expression was detected.

Decrease in fibronectin occurs coincident with the increased expression of its integrin receptor alpha5beta1 in stress-deprived ligaments

Stress deprivation secondary to immobilization leads to atrophic changes in periarticular soft tissues. The changes in ligaments include a disorganization of collagen and cellular ultrastructure with varied biochemical alterations resulting in a functionally weaker tissue. This study tests the hypothesis that alterations in fibronectin (Fn) and the expression of its integrin receptor alpha5beta1 in ligament fibroblasts accompany the extracellular matrix remodeling which occurs in stress-deprived knee ligaments. The left knees of eighteen New Zealand white rabbits were surgically immobilized in acute flexion. Fibroblasts within three nine week and three twelve week stress-deprived anterior cruciate ligaments (ACLs) and medial collateral ligaments (MCLs) demonstrated markedly increased immunostaining for the beta1 and alpha5 integrin subunits, as compared to fibroblasts in the contralateral unoperated control ligaments. The effects of stress deprivation on the concentration of Fn was measured by competitive ELISA on the remaining twelve rabbits. Decreases in Fn of 54.0 percent and 63.7 percent occurred in the ACL after nine and twelve weeks of stress deprivation when compared to contralateral controls. The MCL had less of a decrease, losing 37.7 percent and 41.7 percent at nine and twelve weeks, respectively. These results suggest an important role for the Fn-specific integrin receptor alpha5beta1 in remodeling stress-deprived periarticular ligamentous tissue, and the importance of maintaining normal stresses on periarticular ligaments to prevent the degradation of extracellular matrix components such as Fn.

Insulin-like growth factor-I and alpha 2-macroglobulin in seminal plasma correlate with semen quality

Insulin-like growth factor-I (IGF-I) and alpha 2-macroglobulin (alpha 2-M) are believed to be involved in the development of germ cells. IGF-I is mainly controlled by concentrations of human growth hormone (HGH), influences cell proliferation and differentiation and its action is mediated by insulin-like growth factor-binding proteins (IGFBP), placental protein 14 (PP14) and prostate-specific antigen (PSA). alpha 2-M acts as a broad spectrum proteinase inhibitor and a binding protein for many cytokines and hormones, e.g. inhibin and activin. This study was designed to identify concentrations of these molecules in seminal plasma in normal semen samples of healthy men, correlations with semen quality, the relationship of IGF-I and alpha 2-M with factors affecting male fertility, and whether vasectomy influences the concentrations of these molecules. Concentrations of IGF-I and alpha 2-M in human seminal plasma were related to semen quality, basal concentrations of HGH, testosterone, IGFBP-3, soluble fibronectin receptor (sFNR), PSA and PP14 in seminal plasma and to serum concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH). Commercially available assays were used to analyse 69 semen samples of various quality and 11 post-vasectomy samples. IGF-I concentrations in seminal plasma were significantly correlated with the percentage of morphologically normal spermatozoa (r = 0.748, P = 0.00001) and sperm concentration (r = 0.301, P = 0.011), but negatively correlated with serum FSH (r = -0.506, P = 0.00006) and PSA in seminal plasma (r = -0.388, P = 0.00009). Total alpha 2-M was significantly correlated with sperm count (r = 0.423, P = 0.0005), percentage of progressively motile spermatozoa (r = 0.444, P = 0.00019), quality of motility (sperm motile efficiency, r = 802, P = 0.00001) and straight line velocity (r = 0.411, P = 0.0013). Correlation between the sperm concentration and HGH in seminal plasma was weak (r = 0.287, P = 0.015). Vasectomy reduced the concentration of total alpha 2-M (P = 0.00008) and HGH (P = 0.0068) in the seminal plasma; IGF-I was also reduced after vasectomy when the total ejaculate amount was considered. Thus IGF-I and alpha 2-M are significant for the germ cell development: IGF-I in the maturation of spermatozoa and alpha 2-M in progressive motility.

Differential regulation of airway epithelial integrins by growth factors

The pattern of integrin expression on human airway epithelium changes significantly in injury or inflammation. In particular, two integrins, the fibronectin receptor, alpha 5 beta 1 and the fibronectin/tenascin receptor alpha v beta 6, are expressed at low or undetectable levels in normal airways in vivo but are induced in response to airway epithelial injury. We investigated the effects of various growth factors known to be present in the airways on the expression of constitutively expressed and inducible airway epithelial integrins using flow cytometry. In primary cultures of human airway epithelial cells, transforming growth factor-beta 1 (TGF beta 1) dramatically increased expression of alpha v beta 6 and essentially did not affect the expression of any other integrin, including alpha 5 beta 1. In contrast, epidermal growth factor (EGF) upregulated surface levels of both alpha v beta 6 and alpha 5 beta 1. Together, TGF beta 1 and EGF had an additive effect on alpha v beta 6 and alpha 5 beta 1 expression while increasing levels of alpha 2 beta 1 and decreasing expression of alpha 3 beta 1- and alpha 6-containing integrins. In contrast, the transformed airway epithelial cell line, BEAS-2B, expressed a markedly different repertoire of integrins. Integrin expression on BEAS-2B cells was not affected by any of the growth factors tested in this study. These results demonstrate that, in primary cultures of human airway epithelial cells, the pattern of integrin expression can be dramatically altered by growth factors. The inducible integrins, alpha v beta 6, and alpha 5 beta 1 are most subject to regulation by growth factors and expression of each of these can be differentially regulated. The differential regulation of the two principal fibronectin receptors on airway epithelial cells suggests that they may mediate different cellular responses to fibronectin.

Fibronectin receptor functions in embryonic cells deficient in alpha 5 beta 1 integrin can be replaced by alpha V integrins

alpha 5 beta 1 integrin mediates cell adhesion to extracellular matrix by interacting with fibronectin (FN). Mouse lines carrying null mutations in genes encoding either the alpha 5 integrin subunit or FN have been generated previously. Both mutations are embryonic lethal with overlapping defects, but the defects of alpha 5-null embryos are less severe. Primary embryonic cells lacking alpha 5 beta 1 are able to adhere to FN, form focal contacts, migrate on FN, and assemble FN matrix. These results suggest the involvement of (an)other FN receptors(s). In this study, we examined functions of alpha 4 beta 1 and alpha V integrins in embryonic cells lacking alpha 5 beta 1. Our analysis of cells lacking both alpha 4 beta 1 and alpha 5 beta 1 showed that alpha 4 beta 1 is also not required for these FN-dependent functions. Using alpha V-specific blocking reagents, we showed that alpha V integrins are required for alpha 5-null cells, but not wild-type cells, to adhere and spread on FN. Our data also showed that, although the expression levels of alpha V integrins on the wild-type and alpha 5-null cells are similar, there is an increase in recruitment of alpha V integrins into focal contacts in alpha 5-null cells plated on FN, indicating that alpha V integrins can compensate functionally for the loss of alpha 5 beta 1 in focal contacts of alpha 5-null cells. Finally, our data suggested possible roles for alpha V integrins in replacing the role of alpha 5 beta 1 in FN matrix assembly in vitro and in FN-dependent embryonic functions in vivo.

Fibronectin and its alpha 5 beta 1-integrin receptor are involved in the wound-repair process of airway epithelium

The cell migration that occurs during wound repair is dependent on modifications of the cell-matrix interaction in which extracellular matrix proteins and their receptors, the integrins, are involved. To study the interactions between airway epithelial cells and the extracellular matrix during the process of wound repair, we developed an in vitro wound model of human epithelial cells. Surface epithelial cells were dissociated from human nasal polyps and cultured on a type I collagen matrix. At confluency, a wound was made by the addition of 2 microliters of NaOH (1 N) to the cell culture. After the cell culture was washed, the wound area was recorded every 12 h for 96 h by a videomicroscopic technique. We calculated the wound-repair index that represents the decrease in the wound area per hour. Using immunofluorescence techniques, we first examined the localization, during wound repair, of fibronectin and of the beta 1-, alpha v-, alpha 2-, alpha 3-, and alpha 5-integrin subunits. Secondly, we carried out a series of wound-repair blocking experiments with the use of anti-integrin or anti-fibronectin antibodies diluted in the culture medium. We observed that fibronectin and the alpha 5- integrin subunit were exclusively expressed by the migratory cells in the wounded area. No difference in the localization of the alpha v-, alpha 2-, and alpha 3-integrin subunits was observed between the nonrepairing and repairing cells. The blocking experiments showed a significant decrease in the wound-repair index in the presence of either the anti-beta 1, -alpha 3, alpha 5, or the anti-fibronectin antibodies. Furthermore, the addition of fibronectin to the culture medium induced a significant increase in the wound repair index. These results suggest that fibronectin and the corresponding alpha 5 beta 1-integrin play an important role in the process of airway epithelium wound repair.

Expression of adhesion molecules on myeloma cells

We investigated the expression of adhesion molecules including LFA-1 alpha (CD11a), Mac-1 (CD11b), LFA-1 beta (CD18), VLA-beta 1 (CD29), H-CAM (CD44), VLA-4 (CD49d), VLA-5 (CD49e), ICAM-1 (CD54), N-CAM (CD56), LFA-3 (CD58), VNR-beta (CD61), and LECAM-1 (CD62L) on fresh myeloma cells and human myeloma cell lines. By two-color flow cytometric analysis with anti-CD38 antibody, we demonstrated that myeloma cells were located in the strongly CD38-positive (CD38++) fractions. Fresh myeloma cells were obtained from 28 patients with multiple myeloma (MM) and 3 patients with plasma cell leukemia (PCL). All myeloma cells expressed VLA-4 on their surface. Most of the myeloma cells also expressed VLA-5, ICAM-1, and LFA-3, H-CAM was strongly expressed in 3 cases of PCL and 2 cases of aggressive myeloma, and moderately expressed in other MMs. N-CAM was expressed in 68% of MMs, but none of the 3 PCLs. LFA-1 was expressed in two cases of aggressive myeloma, but not expressed in other non-aggressive myelomas. Most of the myeloma cells did not express Mac-1, VNR-beta, or LECAM-1. These results suggest that VLA-4, VLA-5, ICAM-1, LFA-3, and H-CAM are involved in cellular interaction and migration in MM, and that the expression of N-CAM and LFA-1 varies with disease activity in MM.

Very late antigen (VLA) expression by normal and neoplastic human plasma cells; including an assessment of antibodies submitted to the Vth International Workshop on Leucocyte Differentiation Antigens using human myeloma cell lines

The biology of normal plasma cells and the pathophysiology of human multiple myeloma remain poorly understood. Functional assays are scarce and at present cell phenotyping is providing the most information about how human plasma cells may behave. Three different types of human plasma cells: normal, fresh neoplastic myeloma cells and plasma cell lines, have been studied for their reactivity with antibodies to the beta-1 integrins (Very Late Antigens; VLAs), including a panel obtained from the Vth International Workshop on Leucocyte Differentiation Antigens. Most plasma cell targets express VLA-4 (CD49d positive) and the common beta chain recognized by CD29. CD49e (VLA-5) was occasionally positive. Other VLAs were not usually expressed. These data suggest the wide use by plasma cells of VLA-4, possibly as a ligand with fibronectin and high endothelial venules (HEV). Of other adhesion structures expressed by plasma cells, only CD44 is seen as frequently, and this is also a HEV ligand.

A novel role for the integrin-binding III-10 module in fibronectin matrix assembly

Fibronectin matrix assembly is a cell-dependent process which is upregulated in tissues at various times during development and wound repair to support the functions of cell adhesion, migration, and differentiation. Previous studies have demonstrated that the alpha 5 beta 1 integrin and fibronectin's amino terminus and III-1 module are important in fibronectin polymerization. We have recently shown that fibronectin's III-1 module contains a conformationally sensitive binding site for fibronectin's amino terminus (Hocking, D.C., J. Sottile, and P.J. McKeown-Longo. 1994. J. Biol. Chem. 269: 19183-19191). The present study was undertaken to define the relationship between the alpha 5 beta 1 integrin and fibronectin polymerization. Solid phase binding assays using recombinant III-10 and III-1 modules of human plasma fibronectin indicated that the III-10 module contains a conformation-dependent binding site for the III-1 module of fibronectin. Unfolded III-10 could support the formation of a ternary complex containing both III-1 and the amino-terminal 70-kD fragment, suggesting that the III-1 module can support the simultaneous binding of III-10 and 70 kD. Both unfolded III-10 and unfolded III-1 could support fibronectin binding, but only III-10 could promote the formation of disulfide-bonded multimers of fibronectin in the absence of cells. III-10-dependent multimer formation was inhibited by both the anti-III-1 monoclonal antibody, 9D2, and amino-terminal fragments of fibronectin. A fragment of III-10, termed III-10/A, was able to block matrix assembly in fibroblast monolayers. Similar results were obtained using the III-10A/RGE fragment, in which the RGD site had been mutated to RGE, indicating that III-I0/A was blocking matrix assembly by a mechanism distinct from disruption of integrin binding. Texas red-conjugated recombinant III-1,2 localized to beta 1-containing sites of focal adhesions on cells plated on fibronectin or the III-9,10 modules of fibronectin. Monoclonal antibodies against the III-1 or the III-9,10 modules of fibronectin blocked binding of III-1,2 to cells without disrupting focal adhesions. These data suggest that a role of the alpha 5 beta 1 integrin in matrix assembly is to regulate a series of sequential self-interactions which result in the polymerization of fibronectin.

Identification of receptors binding fibronectin and laminin on fetal rat lung cells

Fibronectin and laminin have been implicated in regulating lung morphogenesis. In the present study, the cell surface receptors involved in fetal lung cell binding to laminin and fibronectin were identified. Messages for alpha5- and beta1-integrin subunits were detected in both fetal lung epithelial cells and fibroblasts. The presence of alpha5 beta1 -integrin on both cell types was demonstrated by immunocytochemistry and confirmed by cell adhesion experiments with fibronectin and RGD-containing peptides. Epithelial cells adhered more readily to laminin than fibroblasts. The alpha4 beta1-integrin, and RGD-independent fibronectin receptor, was weakly expressed on either cell type. Both cell types expressed alpha6-integrin subunit mRNA and stained immunopositive for the alpha6-subunit. Although either cell type expressed nonintegrin 67-kDa laminin-elastin receptor mRNA, no positive immunoreactivity for this laminin-elastin binding protein was detected. None of these findings explain the enhanced attachment of distal fetal lung epithelial cells to laminin compared with fibroblasts. Previously, we have reported that epithelial cells were enriched in alpha3-integrin subunit mRNA and protein expression. Herein, we found that epithelial cell attachment to laminin was nearly completely inhibited by alpha3- but only partially by alpha6 -monoclonal antibodies. A peptide near the globular region at the long arm of the laminin A-chain, which contained the IKVAV sequence, and the laminin A-chain amino acid sequence representing the alpha3 beta1 -integrin binding site, inhibited the adherence of epithelial cells to laminin. Fetal lung epithelial cells attached to substrata coated with the alpha3 beta1-integrin binding site peptide and the peptide containing the IKVAV sequence. These data suggest that both fetal lung cell types bind to fibronectin via the fibronectin receptor, alpha5 beta1, and fetal lung epithelial cells interact with laminin via alpha3 beta1 and proteins that recognize the IKVAV-containing sequence on the laminin A-chain.

Immunohistochemical localization of very late activation integrins in healthy and diseased human gingiva

The beta 1-integrins (VLA family) are cellular adhesion molecules (CAM) that play a major role in cell-cell and cell-matrix interactions. The expression pattern of CAM was studied in 5 clinically normal volunteers with healthy gingiva and in 18 patients with clinically different stages of periodontitis. In healthy human gingiva alpha 2, alpha 3 and alpha 6 integrin chains were found in a characteristic distribution, showing a broad continuous expression on the junctional and sulcular epithelium sites. The expression of these integrins was demonstrated primarily on the basal cell layers and in some cells of the stratum spinosum. Inflammatory stages of periodontitis revealed further upregulation of alpha 2, alpha 3 and alpha 6 integrins into the junctional and sulcular epithelial cells, which correlated with the stage of the periodontitis and the extent of the cellular infiltration. alpha 4 and alpha 6 were found to be the predominant beta 1 integrin chains on inflammatory cells. The amount of alpha 4 and alpha 6 positive infiltrative cells increased with the number of inflammatory cells. VCAM-1, the corresponding cell-cell ligand of VLA-4 (alpha 4) was present on the majority of subepithelial vessels in all stages of gingivitis and periodontitis. The alpha 5 subunit was expressed on both endothelium and gingival connective tissue cells. Samples from advanced periodontitis cases showed a higher number of alpha 5 positive mononuclear cells. In comparison to normal epidermis, human gingival epithelial cells express higher levels of integrins. This expression is further upregulated in advanced stages of periodontitis, indicating changes of the beta 1 integrin organization.

Adhesion of lymphoma cells to fibronectin: differential use of alpha 4 beta 1 and alpha 5 beta 1 integrins and stimulation by the 9EG7 mAb against the murine beta 1 integrin subunit

Murine ESb and MDAY-D2 lymphoma cells are highly metastatic, in particular to the liver, and are highly invasive in hepatocyte cultures. This may involve adhesion to hepatocyte surface-associated fibronectin (Kemperman et al., 1994, Cell Adh. and Communic. 2:45). Both ESb and MDAY-D2 cells express the fibronectin receptor alpha 4 beta 1, and MDAY-D2 cells in addition also alpha 5 beta 1. Yet, adhesion of ESb cells to fibronectin was low, and MDAY-D2 cells did not adhere at all, but adhesion of both cells was stimulated by phorbol myristate acetate (PMA) and Mn2+. In ESb cells, this adhesion was mediated by alpha 4 beta 1. In MDAY-D2 cells, however, only alpha 5 beta 1 was involved, despite alpha 4 beta 1 levels similar to ESb cells. The alpha 4 beta 1 integrin was functional since it mediated adhesion of MDAY-D2 cells to VCAM-1. An alpha 5 beta 1-negative variant of MDAY-D2 adhered to fibronectin and this was mediated by alpha 4 beta 1. These results indicate that alpha 4 beta 1 function in these cells is suppressed in the presence of alpha 5 beta 1. Adhesion of ESb cells to hepatocytes was inhibited by anti-alpha 4 antibody, but only by 30%, and fibronectin adhesion was found to have no role in the interaction of MDAY-D2 cells with hepatocytes. This suggests that alpha 4 beta 1 and alpha 5 beta 1 function is not activated during this interaction. The 9EG7 antibody against mouse beta 1 integrin was described to inhibit beta 1 integrins (Lenter et al., 1993, Proc. Natl. Acad. Sci. USA, 90, 9051). In contrast, we observed that 9EG7 stimulated beta 1-integrin function: Adhesion of ESb and MDAY-D2 cells not only to fibronectin, but also to laminin was induced or enhanced.

Integrin-extracellular matrix interactions in connective tissue remodeling and osteoblast differentiation

The differentiaton of bone cells is a complex multistep process. Bone is somewhat unusual in that it is very actively and continually remodeled in the adult and that maintenance of its mass in the mature organism is exquisitely sensitive to mechanical as well as chemical signals. Bone is also unique because it consists of a very large amount of extracellular matrix (ECM) that is mineralized. The integrin family of ECM receptors has been shown to play an important role in tissue morphogenesis in several systems. Our studies on the regulation of matrix remodeling enzymes by integrins in rabbit synovial fibroblasts show that two b1 integrin fibronectin (FN) receptor complexes (alpha 5 beta 1 and alpha 4 beta 1) cooperate in detecting subtle changes in the composition of the ECM. As a result of signal transduction by these integrins, the levels of mRNA and protein for several members of the metalloproteinase family are regulated in these cells. We have also used antibody and RGD peptide perturbation studies to determine the significance of cell/ECM interactions to normal osteogenesis. We found that interactions between the cell binding domain of FN and integrins are required for both normal morphogenesis and gene expression in cultured osteoblasts that differentiate to form bone-like tissue in culture. These data lead us to propose that beta 1 integrins play an important role in osteoblast differentiation as well as in bone remodeling.

Fibronectin receptors in preimplantation development: cloning, expression, and localization of the alpha 5 and beta 1 integrin subunits in bovine trophoblast

The fibronectin receptor, alpha 5 beta 1, may be involved in many aspects of early development, including migration of endodermal and mesodermal cells during formation of the placenta, trophoblastic outgrowth in culture, and development of an invasive phenotype by fetal cytotrophoblasts. In contrast to the human blastocyst, the bovine blastocyst elongates in the uterine lumen for several days until it begins attachment, and the fetal trophoblast limits its invasion to the maternal epithelium. Fibronectin receptor expression was characterized in bovine embryos before and after their attachment to the uterus. Initially, the polymerase chain reaction (PCR) was conducted with degenerate oligonucleotide primers to isolate bovine cDNAs for the alpha 5 and beta 1 subunits. Bovine-specific primers were then constructed to assay for alpha 5 and beta 1 mRNA expression in embryo RNA during the morula through the attachment stages using reverse-transcriptase PCR. Northern blot analysis was used to quantify mRNA levels from Days 15 to 21. Integrin and fibronectin protein expression was assessed by immunohistochemical examination of embryo sections. Both alpha 5 and beta 1 subunit mRNAs were expressed throughout the stages examined. Expression of both subunit proteins was found in the endoderm at Day 14 but not at Day 18 or later. Fibronectin reactivity was not present at any of the stages examined. Between Days 18 and 21, beta 1-reactivity appeared on the lateral surfaces of the trophoblast cells. Day 24 trophoblast binucleate cells showed intense staining with the beta 1 antibody, suggesting that a beta 1-integrin is involved in binucleate cell migration.

Co-ordinate expression of alpha 5 beta 1 integrin and fibronectin in Dupuytren's disease

The expression of alpha 5 beta 1 (alpha 5 beta 1) integrin and its extracellular ligand fibronectin was studied immunohistochemically in 23 cases of Dupuytren's disease using an immunoperoxidase method for light microscopic visualization. All cases consisted of multiple nodules showing a variable degree of cellularity and fibrosis. Depending on the histological appearance of these nodules, each case was assigned to the three following phases: proliferative, involutional and residual. Alpha 5 beta 1 integrin was detected in the highly cellular areas of both proliferative and involutional phases where fibronectin was simultaneously expressed in the extracellular matrix (ECM). Diversely alpha 5 beta 1 and fibronectin disappeared from the hypocellular areas of involutional phase, undergoing fibrotic transformation, and from the fibrotic connective tissue of residual phases. These findings indicate that the expression pattern of alpha 5 beta 1 integrin correlates with the presence in the ECM of the corresponding ligand fibronectin during the different phases of Dupuytren's disease. We suggest that alpha 5 beta 1 integrin, linking fibronectin to stromal cells of both proliferative and involutional phases, may be involved in the contractile processes occurring in Dupuytren's disease.

[Association between expression of integrin (VLA-3, VLA-5) and malignancy in human colon-cancer]

The expression of the VLA-integrins beta 1, -2, -3, -5, -6 and alpha v beta 3 was studied immunohistochemically in the tissue sample from human colon-cancer. Furthermore, histological stage-grouping of the colon-cancer (I-V), additional vascular invasion such as lymphatic and blood-vessel invasion, was made to express the malignancy of the carcinoma, for making a comparison with the expression of the integrins. Immunohistologically, beta 1, VLA-2, and alpha v beta 3 were mildly expressed in the carcinoma cells and VLA-6, markedly expressed. These findings were not correlated with the malignant stage-grouping. For VLA-3, the carcinoma showed mild to marked expression with a diffuse distribution on the cell surface in the peripheral area of the carcinoma, nearly correlating with the histological stage of malignancy. While, the expression of VLA-5 was almost absent in the carcinoma. These results suggest that the enhanced expression of VLA-3 with suppressed expression of VLA-5 is functionally important for the carcinoma cell invasion and also for the metastasis.

A new phenotypic classification of bone marrow plasmacytosis

Here, we propose a new phenotypic classification of bone marrow plasmacytosis. By 2-color phenotypic analysis with FITC anti-CD38 and PE anti-CD19, -CD56, -VLA-5 or MPC-1 antibody, plasma cells are easily identified on the histogram, even though no more than 1% of plasma cells are found in the bone marrow. Hence, plasma cells are phenotypically classified into polyclonal (reactive) (CD19+CD56-) or monoclonal (neoplastic) plasma cells (mostly CD19-CD56+), and furthermore immature (VLA-5-MPC-1-), intermediate (VLA-5-MPC-1+) and mature plasma cells (VLA-5+MPC-1+). According to these findings, plasmacytosis in the bone marrow can be classified into polyclonal marrow plasmacytosis (POMP) and monoclonal marrow plasmacytosis (MOMP) states. The MOMP state is further subclassified into MOMP-1 and MOMP-2, MOMP-3 and MOMP-4; MOMP-1 is defined by co-existence of monoclonal plasma cells and polyclonal plasma cells, and MOMP-2 to MOMP-4 are dependent on increased proportions of VLA-5-MPC-1- immature myeloma (plasma) cells. We found that the cases of benign monoclonal gammopathy (BMG) according to the conventional classification were in the MOMP-1 state, and myelomas could be classified into the MOMP-2 to MOMP-4 state. Subclassification of the MOMP state may be useful in determining the prognosis of myelomas, where an increase in immature myeloma cells is reported to correlate well with their aggravation during the clinical courses. Therefore, this new phenotypic classification of bone marrow plasmacytosis (POMP and MOMP-1 to MOMP-4) will contribute to differential diagnosis and understanding of therapeutic responses and prognosis in myelomas.