Distinctive integrin expression in the newly forming epidermis during wound healing in humans

Novel roles for alpha3beta1 integrin as a regulator of cytoskeletal assembly and as a trans-dominant inhibitor of integrin receptor function in mouse keratinocytes

Previously we found that alpha3beta1 integrin-deficient neonatal mice develop micro-blisters at the epidermal-dermal junction. These micro-blisters were associated with poor basement membrane organization. In the present study we have investigated the effect of alpha3beta1-deficiency on other keratinocyte integrins, actin-associated proteins and F-actin organization. We show that the absence of alpha3beta1 results in an increase in stress fiber formation in keratinocytes grown in culture and at the basal face of the basal keratinocytes of alpha3-null epidermis. Moreover, we see a higher concentration of actin-associated proteins such as vinculin, talin, and alpha-actinin at focal contact sites in the alpha3-deficient keratinocytes. These changes in focal contact composition were not due to a change in steady-state levels of these proteins, but rather to reorganization due to alpha3beta1 deficiency. Apart from the loss of alpha3beta1 there is no change in expression of the other integrins expressed by the alpha3-null keratinocytes. However, in functional assays, alpha3beta1 deficiency allows an increase in fibronectin and collagen type IV receptor activities. Thus, our findings provide evidence for a role of alpha3beta1 in regulating stress fiber formation and as a trans-dominant inhibitor of the functions of the other integrins in mouse keratinocytes. These results have potential implications for the regulation of keratinocyte adhesion and migration during wound healing.

Ozone alters the distribution of beta1 integrins in cultured primate bronchial epithelial cells

The effects of 0.5 ppm ozone exposure for 6 h on the synthesis and distribution of beta1 integrins were examined in bronchial epithelial cells cultured at an air-cell interface. Ozone exposure damaged cilia and caused significant cell loss. Immunocytochemical localization and quantification of the beta1 subunit in the remaining attached cells using scanning laser cytometry demonstrated time-dependent changes in beta1 distribution in response to ozone. Although no changes were detected immediately after exposure, beta1 immunoreactivity increased 23 +/- 5% and 66 +/- 6% at 6 and 24 h, respectively. The increased immunostaining was localized at the apical surfaces and, to a lesser extent, at cell-cell contacts of cultured cells. Furthermore, integrin redistribution was not due to increased messenger RNA (mRNA) levels and protein synthesis because levels of beta1 mRNA and newly synthesized beta1 protein did not change after ozone exposure. However, immunoprecipitation analysis of beta1 integrins in lysates from equal numbers of cells showed that ozone-exposed cells contained 90 +/- 15% more total beta1 subunit at 24 h after exposure. In addition, our results demonstrated the presence of the alpha5beta1 integrin complex in bronchial epithelial cells and that the detergent-soluble amount of its associated beta1 subunit increased 60 +/- 10% in lysates of ozone-exposed cells. In conclusion, ozone altered cellular distribution of beta1 integrins in the remaining attached cells subsequent to cell injury and loss. The changes in beta1 distribution might be due to increased detergent extractibility of beta1 integrins rather than a real increase in the synthesis of beta1 integrins.

Demystified ... adhesion molecules

The cell adhesion molecules are ubiquitous recognition molecules that allow cells to communicate with one another and their environment. Through these molecules, complex alterations in the cytoplasmic messenger pathways and the microfilamentous cytoskeleton can lead to profound alterations in cell division, differentiation, behaviour, and function (fig 9). It is difficult to conceive of a group of molecules that could be more important to pathologists and to their understanding of disease processes.

In vitro engineering of human skin-like tissue

Coverage of large, full-thickness burns presents a challenge for the surgeon due to the lack of availability of the patient's own skin. Currently, tissue engineering offers the possibility of performing a suitable therapeutic wound coverage after early burn excision by using cultured keratinocyte sheets supported by a dermal layer. The aim of this study was to develop and characterize a skin substitute composed of both epidermal and dermal elements. For this purpose we grew keratinocytes and fibroblasts separately for 15 days within two different types of biomaterials. Cells then were co-cultured for an additional period of 15 days, after which samples were taken and processed with either classic or immunohistochemical stainings. Results showed that (1) human fibroblasts and keratinocytes can be cultured on hyaluronic acid-derived biomaterials and that (2) the pattern of expression of particular dermal-epidermal molecules is similar to that found in normal skin. The data from this study suggest that our skin equivalent might be useful in the treatment of both burns and chronic wounds.

Epidermal differentiation and basement membrane formation by HaCaT cells in surface transplants

The immortal human keratinocyte line HaCaT has been employed in many studies as paradigm for epidermal keratinocytes. In order to demonstrate its potential to form stable epidermal structures in response to connective tissue, this was challenged in surface transplants on nude mice, where normal keratinocytes rebuild a typical epidermis within two weeks. During the initial regeneration phase (day 1-4) multilayered but poorly organized epithelia formed with proliferating cells in all layers in analogy to normal keratinocytes. Similarly, with tissue consolidation (around day 7) proliferation was reduced and restricted to cells in basal position marked by keratin K14 and beta1-integrin immunostaining. The strong suprabasal reaction for K1 and K10, the appearance of the late markers K2e, filaggrin and loricrin as well as the polarized distribution of alpha2beta1 and alpha3beta1 indicated advancing tissue normalization (day 14). Keratinization further improved at around three weeks switching from the initial parakeratotic to the regular orthokeratotic type which was prominent at six weeks. Accordingly, most ultrastructural features typical for epidermis or normal keratinocyte grafts were detectable including a complete basement membrane (BM) with regular attachment structures. Matrix- and BM-components appeared sequentially with marked linear deposition of laminin-5 (day 4) followed by accumulation of collagen-IV and 'classical' BM-laminin between one and two weeks. With the general codistribution of integrin alpha6beta4 and BM-molecules (day 14) collagen-VII lining of BM became prominent, while epithelium and host connective tissue were still separated by the collagen matrix. In accordance with the delayed orthokeratinization, wound-matrix molecules (fibronectin, tenascin) persisted longer than in normal keratinocyte transplants. Finally, grafts of long-term passaged (no. 310) cells demonstrated a remarkable stability in the expression of epidermal markers. Thus, the immortalized HaCaT cells reveal a generally high competence to realize an epidermal phenotype in a natural environment and appear therefore qualified for in vitro studies on structural and regulatory aspects of keratinocyte physiology and pathology.

Expression of tetra-spans transmembrane family (CD9, CD37, CD53, CD63, CD81 and CD82) in normal and neoplastic human keratinocytes: an association of CD9 with alpha 3 beta 1 integrin

Tetra-spans transmembrane family (TSTF) members (CD9, CD37, CD53, CD63, CD81 and CD82) have potent effects on cell growth, motility and adhesion in various cells. However, little is known about their expression in human skin. Using immunohistological techniques, we have studied the localization of all six members of TSTF in normal and carcinomatous human keratinocytes. CD9, CD81 and CD82 were expressed in the entire living layers of the epidermis. Their staining pattern was quite similar, and was mainly intercellular with occasional intracellular immunoreactivity. CD53 expression was confined to the intercellular spaces of the upper spinous or granular layer in the normal epidermis. No clear-cut expression of CD63 could be detected in the epidermis. CD37 was not detected at all. Cultured human keratinocytes also expressed CD9, CD81 and CD82 at the surface membrane of cell-cell boundaries. Expression of CD37 and CD53 was negative in cultured keratinocytes, while CD63 was clearly localized in the cytoplasmic lysosomes. An immunoprecipitation assay revealed that alpha 3 beta 1 integrin is molecularly associated with CD9. The expression of CD9, CD81 and CD82 was markedly down-regulated in basal cell carcinoma but not in Bowen's disease. The abundant and differential expression of TSTF molecules and the selective association of CD9 with alpha 3 beta 1 integrin suggest that the TSTF molecules may be involved in the regulation of epidermal differentiation and integrity in vivo.

Integrins and oral cancer

Integrins are a family of heterodimeric, cation-dependent cell membrane adhesion molecules which mediate cell-cell and cell-matrix interactions. They play a fundamental role in the maintenance of tissue integrity and in the regulation of cell proliferation, growth, differentiation and migration. It is not surprising, therefore, that integrins have been implicated in neoplasia and tumour progression and metastasis. Integrin expression and function are altered in malignant cells, although no specific integrin has been implicated in transformation to the malignant phenotype and changes in integrin expression vary both between and within different tumour types. In oral squamous cell carcinomas there is variable loss or reduced expression of beta 1 integrins and of alpha 6 beta 4, which correlates to loss of basement membrane proteins and is most extensive in poorly differentiated lesions. There are also changes in the repertoire of alpha v integrin expression with de novo expression of alpha v beta 6 which may be important in tumour cell migration. Conversely there is reduced expression of alpha v beta 5. In vitro studies suggest that this integrin may be important in oral neoplasia since alpha v-negative cell lines show a malignant phenotype which can be reversed by transfection of the missing integrin. Because alterations in integrin expression in oral cancers are so variable, it seems unlikely that they will be useful as prognostic markers. However, studies of integrin expression and function are increasing our understanding of cell interactions in oral cancer and may pave the way for novel therapeutic interventions to arrest the progression of individual tumours.

Correlation between hyperproliferation and suprabasal integrin expression in human epidermis reconstituted in culture

In normal epidermis integrin expression is largely confined to the basal layer. However, during wound healing and in psoriatic lesions suprabasal expression is observed. Although the potential importance of suprabasal integrin expression in the pathogenesis of psoriasis has been established, the cause of suprabasal expression is unknown. We now describe changes in integrin expression that occur with time when normal human keratinocytes are grown on two types of dermal equivalent, de-epidermized dermis and collagen gels containing fibroblasts. We show that suprabasal integrin expression is correlated with suprabasal expression of the EGF receptor, but not with expression of keratin 10 or keratin 16. By quantitating the proportion of basal keratinocytes expressing the proliferation marker Ki-67 we could show that suprabasal integrin expression is correlated with high proliferative activity within the basal layer. Taken together with our earlier work, these results suggest that suprabasal integrin expression is linked to hyperproliferation and not to abnormal terminal differentiation or to inflammation; they also establish dermal equivalent cultures as useful experimental models with which to manipulate keratinocyte integrin expression.

Induction and repression of collagenase-1 by keratinocytes is controlled by distinct components of different extracellular matrix compartments

In all forms of cutaneous wounds, collagenase-1 (matrix metalloproteinase-1 (MMP-1)) is invariably expressed by basal keratinocytes migrating over the dermal matrix. We report that native type I collagen mediates induction of MMP-1 by primary human keratinocytes. Collagen-mediated induction of MMP-1 was rapid, being detected 2 h after plating, and was transcriptionally regulated. As demonstrated by in situ hybridization, only migrating keratinocytes expressed MMP-1, suggesting that contact with collagen is not sufficient to induce MMP-1 expression in keratinocytes; the cells must also be migrating. Upon denaturation, type I collagen lost its ability to induce MMP-1 expression but still supported cell adhesion. Other dermal or wound matrix proteins, such as type III collagen, fibrin, and fibronectin, and a mixture of basement membrane proteins did not induce MMP-1 production. In the presence of collagen, laminin-1 inhibited induction of MMP-1 but laminin-5 did not. Taken together, these observations suggest that as basal keratinocytes migrate from the basal lamina onto the dermal matrix contact with native type I collagen induces MMP-1 expression. In addition, our findings suggest that re-establishment of the basement membrane and, in particular, contact with laminin-1 provides a potent signal to down-regulate MMP-1 production as the epithelium is repaired.

Topography and biological role of integrins in human skin

We report the topography of integrins in the human epidermis and in cultured human keratinocytes. Both in situ and in vitro beta 1 integrins are exposed at the cell-cell adhesion interface while beta 4 is located on the basal membrane in contact with the basal lamina. Such defined sorting identifies discrete cell membrane domains that may be involved in defining, building up, and maintaining epithelial cell polarity. The distribution of integrins is deeply altered in hyperproliferative states like those occurring in several experimental conditions and in epidermal diseases.

Towards a molecular definition of keratinocyte activation after acute injury to stratified epithelia

While in recent years we have come to increasingly appreciate the multifaceted role of skin, probably none of these novel contributions is as vital as its barrier function, inferred centuries ago. In human skin this function is fulfilled nearly entirely by the epidermis, a thin stratified squamous epithelium made up primarily of keratinocytes and located at the skin surface. Disruption of the integrity of epidermis triggers a homeostatic response involving blood-derived elements and resident skin cell types that is designed to rapidly restore a functional epithelial lining over the wound site. This article is focused on the process of recruitment of keratinocytes from intact skin tissue at the proximal wound edges to participate in re-epithelialization.

The activity of collagenase-1 is required for keratinocyte migration on a type I collagen matrix

We have shown in a variety of human wounds that collagenase-1 (MMP-1), a matrix metalloproteinase that cleaves fibrillar type I collagen, is invariably expressed by basal keratinocytes migrating across the dermal matrix. Furthermore, we have demonstrated that MMP-1 expression is induced in primary keratinocytes by contact with native type I collagen and not by basement membrane proteins or by other components of the dermal or provisional (wound) matrix. Based on these observations, we hypothesized that the catalytic activity of MMP-1 is necessary for keratinocyte migration on type I collagen. To test this idea, we assessed keratinocyte motility on type I collagen using colony dispersion and colloidal gold migration assays. In both assays, primary human keratinocytes migrated efficiently on collagen. The specificity of MMP-1 in promoting cell movement was demonstrated in four distinct experiments. One, keratinocyte migration was completely blocked by peptide hydroxymates, which are potent inhibitors of the catalytic activity of MMPs. Two, HaCaTs, a line of human keratinocytes that do not express MMP-1 in response to collagen, did not migrate on a type I collagen matrix but moved efficiently on denatured type I collagen (gelatin). EGF, which induces MMP-I production by HaCaT cells, resulted in the ability of these cells to migrate across a type I collagen matrix. Three, keratinocytes did not migrate on mutant type I collagen lacking the collagenase cleavage site, even though this substrate induced MMP-1 expression. Four, cell migration on collagen was completely blocked by recombinant tissue inhibitor of metalloproteinase-1 (TIMP-1) and by affinity-purified anti-MMP-1 antiserum. In addition, the collagen-mediated induction of collagenase-1 and migration of primary keratinocytes on collagen was blocked by antibodies against the alpha2 integrin subunit but not by antibodies against the alpha1 or alpha3 subunits. We propose that interaction of the alpha2beta1 integrin with dermal collagen mediates induction of collagenase-1 in keratinocytes at the onset of healing and that the activity of collagenase-1 is needed to initiate cell movement. Furthermore, we propose that cleavage of dermal collagen provides keratinocytes with a mechanism to maintain their directionality during reepithelialization.

alpha3beta1 Integrin is required for normal development of the epidermal basement membrane

Integrins alpha3beta1 and alpha6beta4 are abundant receptors on keratinocytes for laminin-5, a major component of the basement membrane between the epidermis and the dermis in skin. These integrins are recruited to distinct adhesion structures within keratinocytes; alpha6beta4 is present in hemidesmosomes, while alpha3beta1 is recruited into focal contacts in cultured cells. To determine whether differences in localization reflect distinct functions of these integrins in the epidermis, we studied skin development in alpha3beta1-deficient mice. Examination of extracellular matrix by immunofluorescence microscopy and electron microscopy revealed regions of disorganized basement membrane in alpha3beta1-deficient skin. Disorganized matrix was first detected by day 15.5 of embryonic development and became progressively more extensive as development proceeded. In neonatal skin, matrix disorganization was frequently accompanied by blistering at the dermal-epidermal junction. Laminin-5 and other matrix proteins remained associated with both the dermal and epidermal sides of blisters, suggesting rupture of the basement membrane itself, rather than detachment of the epidermis from the basement membrane as occurs in some blistering disorders such as epidermolysis bullosa. Consistent with this notion, primary keratinocytes from alpha3beta1-deficient skin adhered to laminin-5 through alpha6 integrins. However, alpha3beta1-deficient keratinocytes spread poorly compared with wild-type cells on laminin-5, demonstrating a postattachment requirement for alpha3beta1 and indicating distinct roles for alpha3beta1 and alpha6beta4. Our findings support a novel role for alpha3beta1 in establishment and/or maintenance of basement membrane integrity, while alpha6beta4 is required for stable adhesion of the epidermis to the basement membrane through hemidesmosomes.

Adhesion molecule expression in normal skin and melanocytic lesions. Role of UV-irradiation and architectural characteristics in nevi

Cell adhesion between surfaces of cells and to extracellular matrices represents a fundamental mechanism in tissue organization and influences the biological behaviour and the architecture of tumors. We investigated the expression of various adhesion molecules in normal skin (n=5), nevi (n=29), and malignant melanoma (n=10) by immunohistochemistry. Special attention was paid to the correlation between adhesion molecule expression and the respective architectural features, e.g. UV-induced morphological changes, and the arrangement of melanocytes in congenital nevi. In nevi, a single erythemagenic dose of UV-light did not influence the integrin expression of melanocytes, but results in an upregulation of alpha3 beta1- and alpha6 beta1-integrin within the suprabasal layers of the epidermis. This suprabasal labelling was associated with an increased number of suprabasal melanocytes in UV-irradiated nevi which were detected with HMB-45 antibody. Nine of 10 congenital nevi demonstrated a labelling of alpha4 beta1-integrin only in melanocytes of the deeper dermis. This integrin previously has been associated with high tumor thickness and the clinical outcome in melanomas. The integrin profile observed in melanomas differed in part from that seen in nevi with expression of beta2- and beta3-integrins in some cases. The results may indicate a correlation between adhesion molecule expression and histopathological findings in melanocytic lesions.

Wound healing--aiming for perfect skin regeneration

The healing of an adult skin wound is a complex process requiring the collaborative efforts of many different tissues and cell lineages. The behavior of each of the contributing cell types during the phases of proliferation, migration, matrix synthesis, and contraction, as well as the growth factor and matrix signals present at a wound site, are now roughly understood. Details of how these signals control wound cell activities are beginning to emerge, and studies of healing in embryos have begun to show how the normal adult repair process might be readjusted to make it less like patching up and more like regeneration.

Upregulation of alpha 9 integrin and tenascin during epithelial regeneration after debridement in the cornea

Stratified epithelia are exposed to abrasive forces and are required to respond rapidly to injury to minimize fluid loss and the risk for microbial infection. Healing involves a cell migratory phase to reestablish barrier function and cell proliferation to restratify the epithelium. Cell migration during re-epithelialization involves cell sliding, termed sheet movement, during which cells retain their cell-cell junctions while dynamically altering their shape and cell-substrate interactions to permit movement across the exposed wound bed. Proteins of the integrin family of receptor molecules modulate cell shape, cell migration, and signal transduction in many cell types. In epithelial cells, integrins of the beta 1 family have been implicated in regulating cell proliferation and differentiation, alpha 9 beta b1 is one of the newer members of the integrin beta family and has been recently shown to function as a tenascin receptor. Although little is known about its function in vivo, studies in developing mouse cornea and eyelid suggest that it may play a role in epithelial differentiation. Using a debridement wound model in the mouse cornea, we show in this study that (a) in response to small debridement wounds that close without cell proliferation, alpha 9 integrin protein and mRNA are not induced during migration but are induced during restratification, (b) larger debridement wounds that require cell proliferation to generate the cells necessary for sheet movement result in a dramatic induction of alpha 9 protein and its mRNA during both migration and restratification, and (c) tenascin, an alpha 9 beta 1 ligand, accumulates beneath epithelial cells during restratification but not during cell migration. Therefore, alpha 9 integrin protein production and tenascin accumulation are dynamically regulated in response to corneal epithelial injury.

Integrin and basement membrane normalization in mouse grafts of human keratinocytes--implications for epidermal homeostasis

Integrin patterns and formation of basement membrane (BM) were investigated in correlation to epidermal growth and differentiation during skin regeneration in human keratinocyte transplants on nude mice. Immuno-fluorescence and transmission electron microscopy (TEM) showed that different stages of tissue reconstruction were characterized by a sequence of coordinated events. Features of the initial tissue activation, with rapid keratinocyte proliferation around day 4, including cells in a suprabasal position, were: (1) a marked increase in and extended distribution of the integrin chains alpha 2, alpha 3, beta 1 and alpha 6, while beta 4 already showed a preferential basal location; (2) de novo expression of alpha 5 and alpha v; and (3) marked deposition of laminin-5 and nidogen but low levels of other BM components. Tissue normalization during the 2nd week, initiated by a drastic decrease in the number of proliferating cells after day 4, now strictly in basal position, was signified: by (1) orthotopic staining for basal-type keratins (K5, K14) together with a regular pericellular alpha 2 beta 1 and alpha 3 beta 1 distribution, (2) linear, balanced deposition of BM components (e.g. laminin-1, type IV collagen) and (3) colocalization of integrin alpha 6 beta 4 and bullous pemphigoid antigen. Simultaneously at 7 days hemidesmosomes and a defined BM had developed (TEM), becoming continuous at 14 days. This coincided with the regular distribution of suprabasal keratins (K1, K10) as well as intermediate (involucrin) and late differentiation markers (filaggrin, loricrin). Type-VII collagen deposition, still irregular at 14 days, became continuous at 22 days together with developing BM-anchoring fibrils indicating final tissue consolidation. This model mimics principal stages of epidermal wound healing in human skin and implies a linkage between BM assembly, integrin distribution and the compartment of proliferation competent cells, which in turn determines the onset of differentiation. Thus, apart from the balance of diffusible growth regulators, this positional control of keratinocytes, largely accomplished by integrin-matrix interactions, seems to be prerequisite to establishment and maintenance of tissue homeostasis.

Immune system-neuroendocrine dysregulation in spinal cord injury

Multiple communicative pathways among the nervous, endocrine and immune systems facilitate physiological immunoregulation. Spinal cord injury (SCI) patients have decreased natural (NK cell) and adaptive (T cell) immune function and reduced blood levels of cellular adhesion molecules (CAMs) that participate in immune function and wound healing. We found decreased LFA-1 and VLA-4 on peripheral blood leukocytes in SCI patients and lower levels of CAMs in SCI patients with pressure ulcers than in those without them. SCI might affect immune cells and immune responsiveness by: (1) disrupting the outflow of signals from the sympathetic nervous system to lymphoid tissues and their blood vessels as well as the returning afferent signals from these tissues to the brain; (2) immunosuppression caused by the stressors affecting SCI patients; (3) interrupting returning signals to the CNS from the periphery thereby reducing facilitation of immunoregulatory CNS neurons and decreasing their activity; or a combination of all three. SCI patients may develop dysregulation of the sympathetic nervous system that is intimately involved in immune function. Chronic stress mediates immunosuppression by corticosteroids, catecholamines, endorphins and met-enkephalin. The hypothalamus coordinates the response to stress through the release of soluble products from the sympathetic nervous system and hypothalamic-pituitary-adrenal axis. Whereas the nervous and endocrine systems are not concerned with immunological specificity, they do influence the intensity, kinetics and localization of immune responses. Products of an activated immune system may generate feedback circuits capable of inhibiting, enhancing or regulating neuronal input. Immune system cells can produce neurologically active peptides including ACTH, CRF, growth hormone, thyrotropin, prolactin, human chorionic gonadotropin, endorphin, enkephalins, substance P, somatostatin and VIP. Cytokines are likely important mediators of the HPA response to immune stimuli.

Interaction between the insulin-like growth factor family and the integrin receptor family in tissue repair processes. Evidence in a rabbit ear dermal ulcer model

We have determined previously that IGF-I is dependent on the presence of IGF binding protein-1 (IGFBP-1) to act as a wound healing agent. We sought to determine the mechanism whereby IGFBP-1 is able to enhance IGF-I bioactivity. As IGFBP-1 binds both the alpha5beta1 integrin as well as IGF-I in vitro, we asked which of the following interactions were important: (a) the ability of IGFBP-1 to interact with an integrin receptor, and/or (b) the binding of IGF-I by IGFBP-1. We used an IGF-1 analogue (des(1-3)IGF-I) with a > 100-fold reduction in affinity for IGFBP-1 as well as an IGFBP-1 mutant (WGD-IGFBP-1) which does not associate with the alpha5beta1 integrin to selectively abrogate each of these interactions. We also tested the ability of IGFBP-2, a related binding protein which has an arginine-glycine-aspartate sequence but does not associate with integrin family members, to enhance IGF-I bioactivity. Full-thickness dermal wounds were created on rabbit ears; various combinations of native IGF-I, native IGFBP-1, native IGFBP-2, and their respective analogues/mutants were applied to each wound. Wounds were harvested 7 d later for analysis. Only native IGF-I in combination with native IGFBP-1 was effective as a wound healing agent, enhancing reepithelialization and granulation tissue deposition by 64+/-5 and 83+/-12% over controls (P = 0.008 and 0.016, respectively). The same doses of IGF-I/WGD-IGFBP-1, des(1-3)IGF-I/IGFBP-1, and IGF-I/IGFBP-2 were ineffective. We propose that IGF-I physically interacts with IGFBP-1 and that IGFBP-1 also binds to an integrin receptor, most likely the alpha5beta1 integrin. This interaction is unique to IGFBP-1 as the closely related IGFBP-2 had no effect, a finding consistent with its inability to bind to integrin receptors. Our results suggest that activation of both the IGF-I receptor and the alpha5beta1 integrin is required for IGF-I to stimulate wound healing.

Altered interface adhesion molecules in oral lichen planus

OBJECTIVE

To evaluate expression of key epithelial-connective tissue interface adhesion molecules (basal keratinocyte integrins and extracellular matrix receptors) in oral lichen planus (LP).

DESIGN

Integrins alpha 3, alpha 6, beta 1, beta 4 and basement membrane proteins laminin 1, laminin 5, collagen IV, and collagen VII were immunohistochemically identified in frozen biopsy specimens (14 oral LP and II matched controls) using a standard avidin-biotin-peroxidase technique.

RESULTS

An increased staining intensity of all antigens in LP was shown, as compared to controls. Integrin expression by LP keratinocytes was generally more intense and appeared on more upper level cells. Staining for basement membrane-associated extracellular matrix proteins was also generally more intense, although fragmentation and gaps were typically seen. Reactions for alpha 6, beta 4, laminin 5, and collagen VII stains were particularly intense along the basement membrane. In LP, strands of laminin 5, collagen IV, and collagen VII appeared in the submucosa approximating or duplicating the basement membrane.

CONCLUSIONS

The apparent increased expression of the interface-associated adhesion molecules may be reflective of a keratinocyte compensatory response (due to lymphocyte-mediated damage) that would functionally help resist epithelial separation (ulceration). Expression of alpha 3 beta 1 and alpha 6 beta 4 would also assist in epithelial migration associated with wound repair. We interpret the submucosal extensions and deposits of basement membrane proteins as representing remnants of basement membrane, indicating recent remodeling or atrophy of epithelial rete ridges.

Rapid normalization of epidermal integrin expression after allografting of human keratinocytes

Allogeneic keratinocyte grafts have beneficial effects on skin wounds, but the underlying interactions between graft and woundbed remain to be explored in detail. The epidermal integrins play a pivotal role in mediating cell-to-cell and cell-to-matrix interactions. In unwounded epidermis, alpha 2 beta 1-, alpha 3 beta 1-, alpha 6 beta 4-, alpha 5 beta 1-, and alpha v beta 5-integrins are confined to basal cells. During healing of incisional wounds, these integrins are also expressed in suprabasal cells, where they remain detectable even after epidermal integrity is fully reestablished. We examined the integrin subunits alpha 2, alpha 3, alpha 6, alpha 5, and alpha v in partial thickness burn wounds grafted with allogeneic keratinocytes and asked whether the effect of allogeneic keratinocyte grafts, i.e., fast reepithelialization, is reflected by an accelerated reversion to a normal integrin pattern. Biopsies were taken after wound debridement before grafting and 10 d after transplantation. After 10 d, a stratified epidermis had developed in all cases and integrins were mainly restricted to the basal cell layer of the neo-epidermis. alpha 2-, alpha 3-, alpha 6-, and alpha v-subunits were present at basal and/or lateral cell borders, duplicating the integrin pattern in normal epidermis. The findings indicate that grafting accelerates the shift of the epidermis from an inflammatory to a regenerative state, as reflected by the reversion of the integrin pattern from a "spread-and-migrate" to the "steady-state" phenotype.

Expression of laminin 5, fibronectin, and epithelium-associated integrins in recurrent aphthous ulcers

Recurrent aphthous ulceration (RAU) is characterized by an ulcerated lesion that persists longer than traumatic ulcers of similar size. This delayed healing phase of the lesion was investigated for extracellular matrix components and matrix receptors (integrins). The hypothesis tested was that aphthous ulcers may lack key extracellular matrix components, or their receptors, that are necessary for the migration of marginal keratinocytes from the ulcer edge. We immunocytochemically stained biopsy specimens of RAUs and non-involved mucosal specimens from HIV+ and non-infected individuals to investigate the presence and distribution of molecules reported to be associated with reepithelialization of mucosal and cutaneous wounds. Fibronectin, laminin type 5 (kalinin), and integrin subunits beta 1, beta 4, alpha 6, and alpha v were consistently found at the margins of RAU, as they are in traumatic ulcers. The alpha 5 and beta 6 subunits were not always present. We also found alpha v in the intact stratified squamous epithelium adjacent to ulcers. Immunohistochemical stains showed distruption in the deposition of laminin 5 and an apparent lack of fibronectin at the edges of some ulcers. Although these tissue results do not determine which integrin subunits are paired with each other, they do show some alterations in their expression in RAU. Absence of one or more of these molecules at the migrating front may contribute to delayed epithelial regeneration. It is likely that the absence or inappropriate expression of keratinocyte integrins or their extracellular matrix receptors occurs after the causative factors (currently unknown) of the lesion are gone. The reason for the altered expression of these molecules may be related to the secretory products (including lymphokines and proteinases) of the lymphocytic infiltrate.

Keratinocyte integrins in wound healing and chronic inflammation of the human periodontium

Periodontal epithelium plays a critical role in protection, destruction and repair of human periodontium. During optimal repair, epithelium migrates and covers the wound surface to prevent infection and damage of the vulnerable underlying connective tissue. During periodontal destruction, junctional epithelium undergoes transformation to pocket epithelium that has quite different characteristics from junctional epithelium. In the course of periodontal disease the epithelial attachment to the tooth surface is lost and the epithelium proliferates and extends pseudo-rete ridges deep into the inflamed connective tissue. Both scenarios, repair and destruction, involve active epithelial migration either in the wound provisional matrix or in the inflamed connective tissue matrix, respectively. This review covers recent research data on cellular receptors, integrins, that mediate epithelial cell migration during wound healing and destruction of human periodontium.

Keratinocytes in human wounds express alpha v beta 6 integrin

Cell adhesion receptors of the integrin family play a major role during re-epithelialization of human wounds. We have previously documented that the expression of alpha v family integrins is induced in keratinocytes of mucosal wounds [1]. In the present investigation, we extended these studies to determine whether alpha v beta 6 integrin is expressed during wound healing in humans. Mucosal and epidermal wound sections from 1- to 7-day-old wounds were used for immunolocalization of integrins and their putative ligands. In addition, freshly isolated epidermal keratinocytes were used to study integrin expression in vitro. Expression of alpha v beta 6 integrin appeared relatively late during mucosal and dermal wound healing. Maximal expression was seen in 7-day-old wounds in which epithelial sheets had fused and granulation tissue was present. Fibronectin and tenascin, both possible ligands for alpha v beta 6 integrin, were found concentrated underneath the basal epithelial cells expressing this receptor, and the maximal expression of tenascin coincided with that of alpha v beta 6 integrin. Freshly isolated epidermal keratinocytes did not stain for alpha v beta 6 integrin but began to express this integrin after subculturing. Our results suggest that the expression of alpha v beta 6 integrin, a putative binding integrin for fibronectin and tenascin, is induced in keratinocytes when epithelial sheets fuse during wound healing.

Studies in vitro on the role of alpha v and beta 1 integrins in the adhesion of human dermal fibroblasts to provisional matrix proteins fibronectin, vitronectin, and fibrinogen

Fibroblasts that migrate into a wound during the early stages of repair use cell surface integrins to interact with extracellular molecules as they move away from the interstitial matrix of normal tissue and into the provisional matrix of the wound. Therefore, to understand a critical phase of wound healing, it is necessary to understand the details of integrin involvement. Normal adult human dermal fibroblasts in culture express many receptors for the provisional matrix proteins fibronectin, vitronectin, and fibrinogen, including the integrins alpha 3 beta 1, alpha 4 beta 1, alpha 5 beta 1, alpha v beta 1, alpha v beta 3, and alpha v beta 5. We used quantitative flow cytometry to estimate the relative numbers of these receptors and immunoprecipitation to confirm the expression of alpha v beta 1. Adult human dermal fibroblasts primarily use beta 1 integrins, alpha 4 beta 1, alpha 5 beta 1, and possibly alpha v beta 1, for attachment to fibronectin. alpha v beta 3 and perhaps other integrins containing the alpha v subunit serve fibroblasts as secondary or auxiliary receptors for fibronectin. In contrast, these cells use alpha v integrins but probably not beta 1 integrins for attachment to vitronectin. alpha v beta 3 and alpha v beta 5 apparently act in concert to mediate attachment to vitronectin, and these two integrins may perform different functions during wound repair. Fibroblast adhesion to certain preparations of fibrinogen occurs, at least partially, through the small amount of fibronectin present in the preparations. Fibroblast attachment to fibrinogen purified free of fibronectin also occurs, and that was demonstrated with a sensitive new assay called electrical cell-substrate impedance sensing. Fibroblast attachment to pure fibrinogen can be inhibited by RGD peptide, suggesting that integrins are involved.

The integrin alpha 6 beta 4 and the biology of carcinoma

The integrin family of adhesion receptors plays a major role in epithelial organization and function. Moreover, the altered expression and function of specific integrins most likely contributes significantly to carcinoma progression. The integrin alpha 6 beta 4, the focus of this review, is a receptor for several members of the laminin family and is preferentially expressed at the basal surface of most epithelia, where it contributes to basement membrane interactions. Mounting evidence suggests that the alpha 6 beta 4 integrin plays a key role in carcinoma cell biology. Several histopathological studies have established a correlation between alpha 6 beta 4 integrin expression and tumor progression. The importance of alpha 6 beta 4 expression in tumors in underscored by the findings that invading fronts of several carcinomas are enriched in the expression of alpha 6 beta 4 integrin ligands, such as laminin-1 and laminin-5. The participation of the alpha 6 beta 4 integrin in invasion is supported further by in vitro functional studies using carcinoma cells that have been transfected with the beta 4 cDNA. The mechanisms by which alpha 6 beta 4 contributes to tumor progression are probably related to its mechanical and signaling properties and are currently under intense study.

Integrin receptors and their relationship to cellular proliferation and differentiation of oral squamous cell carcinoma. A quantitative immunohistochemical study

The expression of extracellular matrix (ECM) proteins (fibronectin, laminin, collagen IV) and ECM receptors of integrin type (alpha 2 beta 1, collagen receptor; alpha 6 chain of the fibronectin receptor; alpha 6 chain of the laminin receptor) were examined in normal oral squamous epithelium and in invasive areas of squamous cell carcinomas with various differentiation and proliferation activities (Ki-67 antigen labelling), evaluating the presence, quantity (using an image analysis system) and distribution of the integrin subunits. In the mucosa, there was uniform immunostaining for alpha 2 beta 1 and alpha 6 concentrated at the cell membrane in the basal/supra basal cell zone, whereas, alpha 5 showed a discontinuous staining of the basal cell-basement membrane interface. alpha 2 and alpha 6 could be visualized in all carcinomas. alpha 5 showed low expression preferentially in less differentiated carcinomas. In contrast to normal mucosa, there was an increase in alpha 6 staining in well-differentiated carcinomas. Dedifferentiation of oral carcinomas was accompanied by an increase in cellular proliferation and with a decrease in alpha 2 beta 1 and alpha 6 staining. This reduction of alpha 6 staining was shown to be statistically significant, suggesting that this integrin may be a valuable grading parameter for oral squamous cell carcinoma.

Orientated mats of fibronectin as a conduit material for use in peripheral nerve repair

This study introduces a new nerve conduit material consisting of orientated strands of the cell adhesive fibronectin. Axonal regeneration, Schwann cell behaviour and the degree of inflammation were quantified using immunohistochemical techniques and computerized image analysis. The results when fibronectin was used to bridge a 1 cm defect in rat sciatic nerve were compared to those with autologous nerve grafts and freeze-thawed muscle grafts used as controls. The nerve grafts supported the highest rate and amount of axonal regeneration in the first 10 days; however, the fibronectin supported a significantly faster rate of growth (P = 0.0008) and amount (P = 0.0001) of axons than the freeze-thawed muscle grafts. From day 15 onwards, the fibronectin and nerve grafts had comparable amounts of regenerating axons and Schwann cells. We conclude that the orientated form of fibronectin is a suitable material for successful nerve repair and has potential clinical use.

Transplantation of keratinocytes in the treatment of wounds

BACKGROUND

Keratinocyte grafting can be used to treat acute traumatic and chronic non-healing wounds. The keratinocyte sheets are fragile and clinical "take" is difficult to assess, especially as activated keratinocytes secrete many growth factors, which have effects on wound healing apart from take. We have developed animal models of grafting that allow us to examine factors influencing autologous keratinocyte graft take. Results show clearly that pretreatment of the wound bed with viable dermis greatly increases the take of keratinocyte grafts.

DATA SOURCES

International literature.

CONCLUSIONS

As a greater understanding of the complex interactions of cell and matrix evolve, so will potential therapeutic maneuvers, not just in the field of cultured keratinocyte grafts, but clearly in that of benign tumors, for example, keloids, and that of oncology. There is now overwhelming evidence of the requirement for a dermal substitute for cultured keratinocyte autografts, and the sheet complexity of the situation demands that this should approximate live human dermis as closely as possible. The stumbling blocks relate to avoiding the risks of viral transmission, tissue matching of host and donor, providing early epithelial cover, and improving delivery systems for fragile keratinocyte grafts.

A novel role for alpha 3 beta 1 integrins in extracellular matrix assembly

To study the biological role of alpha 3 beta 1 integrins in cell adhesion, migration, and in the deposition of extracellular matrix, we stably expressed the human alpha 3 integrin subunit in the alpha 4, alpha 5 integrin deficient CHO cell line B2. The expression of alpha 3 beta 1 integrins enhanced cell adhesion on entactin (also known as nidogen), but not on fibronectin. Using recombinant GST-fusion proteins that span the entire length of the entactin molecule, we located cell adhesive activity to the G2 domain of entactin. These results suggest that the alpha 3 beta 1 integrin functions as an adhesion receptor interacting with the G2 domain of entactin. On the other hand, the expression of alpha 3 beta 1 integrins did not confer the ability to migrate on entactin. Strikingly, the expression of alpha 3 beta 1 dramatically increased the deposition of entactin and fibronectin into the pericellular matrix. This was accompanied by increased binding activity of the 29 kDa amino-terminal domain of fibronectin. Thus, similar to alpha 5 beta 1 integrins, alpha 3 beta 1 integrins can play an important role in modulating the assembly of pericellular matrices. However, unlike fibronectin deposition supported by alpha 5 beta 1, alpha 3 beta 1 supported fibronectin deposition into pericellular matrix was not inhibited by antibodies binding to the RGD containing cell adhesion domain of fibronectin, demonstrating that the two processes are mechanistically distinct. The role of alpha 3 beta 1 in pericellular matrix assembly potentially implicates this receptor in the assembly and/or recognition of entactin-containing pericellular matrices, an observation consistent with its apparent role in the renal glomerulus of the mammalian kidney.

Transforming growth factor-beta 1 modulates beta 1 and beta 5 integrin receptors and induces the de novo expression of the alpha v beta 6 heterodimer in normal human keratinocytes: implications for wound healing

The molecular mechanism underlying the promotion of wound healing by TGF-beta 1 is incompletely understood. We report that TGF-beta 1 regulates the regenerative/migratory phenotype of normal human keratinocytes by modulating their integrin receptor repertoire. In growing keratinocyte colonies but not in fully stratified cultured epidermis, TGF-beta 1: (a) strongly upregulates the expression of the fibronectin receptor alpha 5 beta 1, the vitronectin receptor alpha v beta 5, and the collagen receptor alpha 2 beta 1 by differentially modulating the synthesis of their alpha and beta subunits; (b) downregulates the multifunctional alpha 3 beta 1 heterodimer; (c) induces the de novo expression and surface exposure of the alpha v beta 6 fibronectin receptor; (d) stimulates keratinocyte migration toward fibronectin and vitronectin; (e) induces a marked perturbation of the general mechanism of polarized domain sorting of both beta 1 and beta 4 dimers; and (f) causes a pericellular redistribution of alpha v beta 5. These data suggest that alpha 5 beta 1, alpha v beta 6, and alpha v beta 5, not routinely used by keratinocytes resting on an intact basement membrane, act as "emergency" receptors, and uncover at least one of the molecular mechanisms responsible for the peculiar integrin expression in healing human wounds. Indeed, TGF-beta 1 reproduces the integrin expression pattern of keratinocytes located at the injury site, particularly of cells in the migrating epithelial tongue at the leading edge of the wound. Since these keratinocytes are inhibited in their proliferative capacity, these data might account for the apparent paradox of a TGF-beta 1-dependent stimulation of epidermal wound healing associated with a growth inhibitory effect on epithelial cells.

Changes in the concentrations of extracellular Mg++ and Ca++ down-regulate E-cadherin and up-regulate alpha 2 beta 1 integrin function, activating keratinocyte migration on type I collagen

We have demonstrated recently that shifts in the concentrations of extracellular Mg++ and Ca++ occur during cutaneous injury in vivo. These shifts correlate well with the timing of migration of various cell types involved in wound healing, including keratinocytes. In the present study, we examined the potential of such cation shifts to activate the keratinocyte migratory phenotype. In modified Boyden chamber migration assays, alpha 2 beta 1 integrin-mediated migration of human keratinocytes (HaCaT) on type I collagen was supported by Mg++ but not by Ca++ alone. Migration could be increased up to twofold, however, by using both cations in combination, as long as the Mg++ concentration was in the optimal range for migration in Mg++ only (1-3 mM) and Ca++ was present at concentrations of approximately 0.1-1 mM. Further examination of this divalent-cation-induced migratory keratinocyte phenotype demonstrated that, as Mg++ is elevated and Ca++ is reduced, mature E-cadherin and cell-cell contacts are reduced and the alpha 2 beta 1 integrin is redistributed from cell-cell contacts to the periphery. These in vitro observations corroborate what occurs in vivo at the keratinocyte migrating front during wound healing. Together these data suggest that changes in the concentrations of extracellular Mg++ and Ca++ can regulate the competitive interplay between Ca(++)-dependent E-cadherin-mediated and Mg(++)-dependent alpha 2 beta 1-integrin-mediated adhesion, promoting the development of an activated keratinocyte phenotype.

Expression of integrin receptors and ICAM-1 on keratinocytes in vivo and in an in vitro reconstructed epidermis: effect of sodium dodecyl sulphate

Several integrin heterodimers such as alpha 2 beta 1, alpha 6 beta 4 and alpha v beta 5 are expressed on basal keratinocytes of the epidermis. Because overexpression of these integrins as well as induction of the intercellular adhesion molecule-1 (ICAM-1) have been found in inflammatory dermatoses, we sought to determine whether these modulations could be used as markers of skin irritation. In normal epidermis, topical application of 1% sodium dodecyl sulphate (SDS) for 24 h caused an upregulation of alpha 3, beta 1, alpha 6, beta 4, alpha v, beta 5 and to a lesser extent alpha 2 integrin chains as well as an induction of ICAM-1. To investigate whether these parameters could also be used for evaluation of skin irritancy in vitro, SDS was applied for 24 h to reconstructed epidermis on de-epidermized dermis (RE-DED). In RE-DED, integrin overexpression and aberrant alpha 5 expression was seen under normal in vitro culture conditions and topical application of SDS caused only marginal additional upregulation. We could not detect any ICAM-1 reactivity on either normal or irritated RE-DED. Our results demonstrate that the modulation of integrin and ICAM-1 expression can be used as markers of irritation of the epidermis in vivo, but not in vitro.

Integrin and phosphotyrosine expression in normal and migrating newt keratinocytes

BACKGROUND

Cells interact with the extracellular matrix through a family of cell surface receptors known as integrins. Ligand specificity of a given integrin is determined in part by the type of alpha and the type of beta subunit comprising it. Accumulating evidence suggests that integrin-ligand binding in some systems influences cell behavior through tyrosine phosphorylation of intracellular proteins.

METHODS

In this study, we utilized immunohistochemistry to examine the expression of beta 1 and beta 4 integrin subunits as well as tyrosine phosphorylation in normal keratinocytes and in keratinocytes migrating to form a wound epithelium. An adhesion assay was used to determine if freshly isolated keratinocytes could interact with fibronectin and collagen. Polyacrylamide gel electrophoresis followed by immunoblotting was employed to compare beta 1 integrins in migrating and nonmigrating keratinocytes.

RESULTS

In normal epidermis, beta 1 and beta 4 localized primarily to basal cells, where both subunits were generally distributed over all parts of the cell periphery. Except for a modest presence in suprabasal cells and a minimal presence adjacent to the epidermal basement membrane, phosphotyrosine (ptyr) had a similar distribution. In migrating keratinocytes, beta 1, beta 4, and ptyr localized most heavily at the interface between the forming wound epithelium and the wound bed. Adhesion assays using keratinocytes from normal epidermis revealed a population of cells that could specifically adhere and spread on fibronectin and type I collagen. Immunoblots of beta 1 subunits from normal and migrating keratinocytes showed no increase in amount of beta 1, nor did the apparent size of beta 1 change in migrating compared to normal cells.

CONCLUSIONS

The heavy accumulation of beta 1 and beta 4 at the wound bed interface in migrating cells suggests that these subunits may be involved in attachments of migrating cells to extracellular matrix proteins in the wound. The accumulation of ptyr in the same region further suggests that integrin-ligand interaction in keratinocytes modulates cell behavior through phosphorylated proteins. The fact that freshly isolated newt keratinocytes could adhere and spread on fibronectin or collagen shows that these cells are constitutively activated. This view is supported by the absence of any evidence that the beta 1 in migrating keratinocytes is larger and therefore more mature than beta 1 in normal keratinocytes. By comparison, beta 1 integrins on human keratinocytes are not constitutively activated (Takashima and Grinnell, 1985; Toda et al., 1987; Guo et al., 1990, 1991), a difference that may explain why epidermal wound healing is faster in newts than in humans.

Role of integrins in cell adhesion and polarity in normal keratinocytes and human skin pathologies

In vitro, normal human keratinocytes reconstitute a differentiated stratified epidermis, maintaining the same gene expression pattern as its in vivo counterpart and are suitable for permanent grafting onto patients. Keratinocyte adhesion to basal lamina and lateral interactions among basal epidermal cells are also mediated by integrin receptors that are sorted to defined plasma membrane domains. The hemidesmosome-associated integrin alpha 6 beta 4 is sharply localized at the basal surface of basal cells and codistributes with laminin and nicein/kalinin; the alpha 2 beta 1 and alpha 3 beta 1 integrins are enriched laterally and play crucial roles in cell-cell interaction and proper colony morphology. During wound healing, proliferating and migrating keratinocytes express on their plasma membrane alpha v beta 5 and alpha 5 beta 1, which allow keratinocyte attachment and migration over the provisional matrix present in the wound. TGF beta, which is an autocrine and paracrine mediator in wound healing, specifically increases the synthesis and expression of alpha v beta 5 and alpha 5 beta 1, induces the de novo expression of alpha v beta 6, and determines the loss of integrin polarization. In hyperproliferative skin diseases, such as skin cancer or psoriasis vulgaris, and in normal keratinocytes forced into more frequent cell cycles, the polarized expression of integrins is lost, and alpha 5 beta 1 becomes costitutively expressed on the plasma membrane. In addition, the alpha 6 beta 4 integrin becomes associated with focal contacts. Nerve growth factor (NGF) is a potent autocrine stimulator of keratinocyte growth and induces melanocyte migration toward the leading edge of a healing wound.(ABSTRACT TRUNCATED AT 250 WORDS)

Wound repair in the context of extracellular matrix

Wound repair requires a continually evolving network of interactions among cells, cytokines and the extracellular matrix. Cell-surface integrins provide a mechanical connection between matrix components and the cytoskeleton, and integrins can transduce an astonishing variety of signals along pathways that may intercept the pathways triggered by cytokine receptors.

TGF-beta 1 stimulates expression of keratinocyte integrins during re-epithelialization of cutaneous wounds

Epidermal keratinocytes migrate over a provisional matrix during the re-epithelialization of cutaneous wounds. We have investigated the expression of integrins and of transforming growth factor-beta 1 (TGF-beta 1) during re-epithelialization in a porcine model. Tissue specimens were collected at different times after injury and stained with antibodies against subunits of the fibronectin receptor, integrin alpha 5 beta 1, and the vitronectin receptor, integrin alpha v beta 5. Intense staining was observed in the migrating keratinocytes of 5-d wounds; basal and suprabasal cells were stained around the entire cell periphery. Staining returned toward normal levels in 14-d wounds. The appearance of the extracellular form of TGF-beta 1 seemed to be coordinated with the increased expression of integrin subunits: it was detected in migrating keratinocytes and in the adjacent epidermis of early wounds at 5 and 7 d. We also investigated the effect of TGF-beta 1 on cultured epidermal cells. Treating human keratinocytes with TGF-beta 1 increased the levels of mRNA for the integrin subunits alpha 5, alpha v, and beta 5, but had little effect on beta 1. The corresponding cell-surface expression of alpha 5 and alpha v was also increased after treatment. Thus, during wound repair, TGF-beta 1 may induce epidermal keratinocytes to express integrins that facilitate the migratory component of re-epithelialization.

Integrin expression in middle ear cholesteatoma

Cholesteatoma is lined by a squamous keratinizing epithelium exhibiting most of the features of normal epidermis. In this study, we investigated by immunohistochemistry the expression of integrin adhesion molecules in primary acquired and recurrent cholesteatomas, and compared it with common epidermal cysts and normal human skin. The results showed that cholesteatoma epithelium exhibited a markedly augmented expression of alpha v integrin subunit and a corresponding increased deposition of vitronectin (alpha v ligand) in the surrounding stroma as compared to epidermal cyst and normal human skin. In contrast, the expression pattern of alpha 2 beta 1, alpha 3 beta 1, and alpha 6 beta 4 integrins as well as the distribution of laminin, collagen IV and fibronectin were similar in cholesteatomas, epidermal cysts and normal human skin. Similar staining pattern was observed in primary acquired and recurrent cholesteatoma.