Destruction of the epithelial anchoring system in lichen planus

Role of Hemidesmosomes in Oral Carcinogenesis: A Systematic Review

BACKGROUND

Oral cancers have limited diagnostic tools to aid clinical management. Current evidence indicates that alterations in hemidesmosomes, the adhesion complexes primarily involved in epithelial attachment to the basement membrane, are correlated to cancer phenotype for multiple cancers. This systematic review aimed to assess the experimental evidence for hemidesmosomal alterations, specifically in relation to oral potentially malignant disorders and oral squamous cell carcinomas.

METHODS

We conducted a systemic review to summarise the available literature on hemidesmosomal components and their role in oral pre-cancer and cancer. Relevant studies were retrieved from a comprehensive search of Scopus, Ovid MEDLINE, Ovid Embase and Web of Science.

RESULTS

26 articles met the inclusion criteria, of which 19 were in vitro studies, 4 in vivo studies, 1 in vitro and in vivo study, and 2 in vitro and cohort studies. Among them, 15 studies discussed individual alpha-6 and/or beta-4 subunits, 12 studies discussed the alpha-6 beta-4 heterodimers, 6 studies discussed the entire hemidesmosome complex, 5 studies discussed bullous pemphigoid-180, 3 studies discussed plectin, 3 studies discussed bullous pemphigoid antigen-1 and 1 study discussed tetraspanin.

CONCLUSION

Heterogeneity in cell type, experimental models, and methods were observed. Alterations in hemidesmosomal components were shown to contribute to oral pre-cancer and cancer. We conclude that there is sufficient evidence for hemidesmosomes and their components to be potential biomarkers for evaluating oral carcinogenesis.

Diagnostic potential of Type VII Collagen during oral carcinogenesis

Type VII collagen (Col7) is a major component of anchoring fibrils. Col7 plays a role in tumor development and aggressiveness of cutaneous squamous cell carcinoma of recessive dystrophic epidermolysis bullosa. However, the role of Col7 in oral squamous cell carcinoma (OSCC) and oral leukoplakia (OL) remains largely unknown. To elucidate the role of Col7 and its diagnostic potential during oral carcinogenesis. Col7 expression was immunohistochemically studied in 254 samples, including normal oral mucosa (NM), OL without dysplasia, OL with dysplasia, and OSCC. The correlation between Col7 expression and clinicopathologic parameters of OSCC was also determined. Col7 was present as a linear deposit at the basement membrane of NM, OL without dysplasia and OL with dysplasia, and at the tumor-stromal junction around tumor islands in OSCC. Discontinuity of expression was frequently observed in OL with dysplasia and OSCC. OSCC had the significantly lowest Col7 expression (p<0.0001). Compared with OL without dysplasia, OL with dysplasia showed significantly reduced Col7 expression. Patients in clinical stage 4 with positive nodes had low Col7 expression compared with those in clinical stage 1 and negative nodes, respectively. Loss of Col7 is associated with tumorigenesis and aggressiveness in OSCC. A significantly reduced Col7 expression in OSCC implies that Col7 may be a useful marker for diagnosis and therapeutic targets.

Composition of hemidesmosomes in basal keratinocytes of normal buccal mucosa and oral lichen planus

Oral lichen planus (OLP) is a chronic inflammatory disease displaying ultrastructural disturbances in epithelial hemidesmosomes. The expression of several key hemidesmosomal components in OLP as well as in normal buccal mucosa is, however, unknown. The aim of the study was therefore to examine intracellular and extracellular components involved in hemidesmosomal attachment, in OLP (n = 20) and in normal buccal mucosa (n = 10), by immunofluorescence. In normal buccal mucosa, laminin-α3γ2, integrin-α6β4, CD151, collagen α-1(XVII) chain, and dystonin showed linear expression along the basal membrane, indicating the presence of type I hemidesmosomes. Plectin stained most epithelial cell membranes and remained unphosphorylated at S4642. In OLP, most hemidesmosomal molecules examined showed disturbed expression consisting of discontinuous increases, apicolateral location, and/or intracellular accumulation. Plectin showed S4642-phosphorylation at the basement membrane, and deposits of laminin-α3 and laminin-γ2 were found within the connective tissue. The disturbed expression of hemidesmosomal proteins in OLP indicates deficient attachment of the basal cell layer, which can contribute to detachment and cell death of basal keratinocytes seen in the disease.

A potential peptide pathway from viruses to oral lichen planus

Oral lichen planus is an idiopathic inflammatory disease of oral mucous membranes, characterized by an autoimmune epidermis attack by T cells. It remains unknown, however, how such aggressive T cells are activated in vivo to cause epidermal damage. This study analyzes the relationship at the peptide level between viruses and oral lichen planus disease. Four potentially immunogenic peptides (SSSSSSS, QEQLEKA, LLLLLLA, and MLSGNAG) are found to be shared between HCV, EBV, HHV-7, HSV-1, and CMV and three human proteins (namely pinin, desmoglein-3, and plectin). The described peptide sharing might be of help in deciphering the still unexplained immunopathogenic pathway that leads to oral lichen planus.

Immunohistochemistry of ultrastructural changes in scarring lupus erythematosus

BACKGROUND

The various clinical types of lupus erythematosus (LE) show an essentially similar histological picture, and the subsets of LE cannot easily be distinguished by histology alone. However, there is an important clinical difference: lesions of discoid LE (DLE) cause scarring, particularly on the scalp, whereas lesions of subacute and acute LE heal without scarring. The focal thickening of the basement membrane zone (BMZ) in DLE lesions represents an important histopathological finding, and there is little known about the nature of these alterations at the BMZ level.

AIM

To investigate BMZ alterations in the basement membrane zone (BMZ) in cutaneous LE (CLE) by immunohistochemistry.

METHODS

Skin biopsies from 30 patients with CLE [DLE and subacute CLE (SCLE)] and from 10 controls were studied using antibodies to cytokeratin 5, cytokeratin 14, bullous pemphigoid (BP)180, BP230, plectin, laminin 5, collagen IV and collagen VII. Results.  There was increased expression of components of the lamina lucida, lamina densa and anchoring fibrils in active DLE, whereas expression was normal in SCLE and control tissues, and in areas of scarring in DLE. In addition, higher expression of the hemidesmosome-associated antigens (BP230 and plectin) was found in active DLE. The expression of other antigens was similar in all tissues examined.

CONCLUSIONS

These alterations in the BMZ suggest that the BMZ may react in a different way in active DLE than in SCLE, and that the BMZ may remodel in different ways. These immunohistochemical differences may provide a new method of histological differentiation between the various LE subtypes.

Basement membrane changes in lichen planopilaris

BACKGROUND

Lichen planopilaris (LPP) is an inflammatory disease that affects the scalp and tends to produce cicatricial alopecia. The inflammatory process frequently results in the disruption of the basal cell of the external root sheath of the hair follicle.

OBJECTIVES

To investigate the alterations in the basement membrane zone (BMZ) in LPP by immunohistochemistry.

METHODS

Skin biopsies from six patients with LPP plus six normal controls were studied by immunohistochemistry with antibodies to the following BMZ components: cytokeratin 5, cytokeratin 14, BP230 (bullous pemphigoid), BP180, plectin, laminin 5, collagen IV and collagen VII.

RESULTS

The localization and staining of the hemidesmosome, laminin and collagen components were strikingly different in the inflamed follicular epithelium when compared to the uninvolved follicles or interfollicular epithelium in active LPP lesions. The hemidesmosome-associated complexes were weakly expressed and discontinuous in involved hair follicles. The expression of laminin-5, type IV collagen and type VII collagen was disrupted and not linear along the BMZ with finger-like projections of the staining protruding into the dermis. The expression of the intermediate filaments was normal.

CONCLUSION

These alterations in the BMZ in LPP may explain the abnormal healing at follicular level which leads to irreversible hair loss and scarring in this condition.

Expression of matrix metalloproteinases (MMP-2, MMP-3, and MMP-9) and fibronectin in lichen planus

BACKGROUND

Keratinocyte damage and lichenoid-interface reaction are the two major pathologic findings in lichen planus (LP). Matrix metalloproteinases (MMPs) are proteinases that participate in extracellular matrix (ECM) degradation and may play an important role in basal membrane (BM) damage in LP. Fibronectin (FN) mediates a variety of cellular interactions with ECM and plays important roles in cell adhesion, migration, growth and differentiation.

OBJECTIVE

To determine MMP-2, MMP-3, MMP-9 and FN expressions in LP and discuss the possible associations.

MATERIALS AND METHODS

Skin biopsy samples of 55 patients with LP and 11 normal skin were investigated. Five discoid lupus erythematosus (DLE) and 5 chronic dermatitis (CD) samples were also examined for comparison. Immunochemical stainings were performed for MMP-2, MMP-3, MMP-9 and fibronectin.

RESULTS

Weak or absent expressions of MMP-2 and MMP-3 in epidermis; and dense MMP-9 expression in dermal inflammatory infiltrate cells were detected in LP. FN expression was lost in epidermal basal layer and papillary dermis.

CONCLUSION

Loss of MMP-2, MMP-3 and FN in LP can be explained with the destruction of the epidermal basal layer. Similar expressions of MMP-2 and MMP-3 both in LP and DLE implied that these MMPs may be involved in the pathogenesis of interface dermatitis.

The basement membrane zone and dermal extracellular matrix in erosive lichen planus of the vulva: an immunohistochemical study demonstrating altered expression of hemidesmosome components and anchoring fibrils

Histopathology demonstrates disruption of the basal layer of the epidermis in lichen planus (LP) and altered expression of basement membrane zone (BMZ) components occurs in cutaneous and oral LP. This is the first study in erosive LP of the vulva to investigate the expression of components of the BMZ and extracellular matrix by indirect immunofluorescence. Six biopsies from lesional vulval erosive LP were compared with two biopsies from normal vulva and five biopsies from normal skin. In erosive vulval LP there was widespread disruption of several BMZ components compared to normal skin. The hemidesmosome antigens were disrupted and attenuated, or absent. Expression of lamina lucida proteins and anchoring filaments also showed some alteration. Lamina densa components were altered and in particular there was very marked thickening, streaking and fragmentation of the anchoring fibrils. Some dermal extracellular matrix proteins were increased. This study has demonstrated widespread damage to the BMZ in erosive LP of the vulva, in particular the hemidesmosomes (alpha6beta4 integrin, BP230, BP180) and anchoring fibrils (collagen VII). This suggests an alteration in antigenic expression in the BMZ that may lead to exposure of epitopes and thus make these proteins vulnerable to attack by autoantibodies.

Oral and serum IL-6 levels in oral lichen planus patients

OBJECTIVE

The purpose of this study was to compare IL-6 levels in oral exfoliated mucosal cell samples and in serum in subjects with oral lichen planus versus controls. Study design Ten patients with ulcerative OLP, 10 with reticular OLP, and 10 control subjects were recruited at a University Oral Medicine Clinic. Using smear tissue culture brushes, oral samples were collected from lesional sites for OLP patients and from buccal mucosa for controls into vials with 300 muL PBS. After centrifugation, the supernatants were aspirated for cytokine ELISA assay and protein assay. Venous blood was processed to serum for ELISA assay. Oral IL-6 was expressed as both pg/mL and pg/mug protein, and serum IL-6 was expressed as pg/mL.

RESULTS

The mean oral IL-6 levels were higher in the ulcerative OLP group (11.19 +/- 5.34 pg/mL) than in the reticular OLP (1.05 +/- 0.34 pg/mL) and control (0.52 +/- 0.29 pg/mL) groups. There were significant differences between ulcerative OLP and reticular OLP groups (P < .039), and between ulcerative OLP and control groups (P < .009). After the standardization of IL-6 concentration by protein, a significant difference in IL-6 concentration was shown only between the ulcerative OLP (0.0245 +/- 0.0121 pg/mug protein) and control (0.0023 +/- 0.0012 pg/mug protein) groups (P < .029). Similarly, the ulcerative OLP group showed a significantly higher serum IL-6 level than the control group (P < .021).

CONCLUSION

Both oral and serum IL-6 levels were higher in patients with ulcerative OLP. An oral exfoliated cell technique may be a useful and sensitive method to measure IL-6 in patients with OLP as it provided results consistent with those found in peripheral blood.

Oral lichen planus: causes, diagnosis and management

Oral lichen planus (OLP) is a chronic inflammatory disease of unknown etiology. In this paper we review the clinical and histological features of OLP, process of OLP diagnosis, causes of OLP, management of OLP patients and medical treatment of OLP lesions. Approximately 0.2 per cent OLP patients develop intra-oral carcinoma each year compared with approximately 0.005 per cent Australian adults. Possible mechanisms of increased oral cancer risk in OLP patients are presented. The aims of current OLP therapy are to eliminate mucosal erythema and ulceration, alleviate symptoms and reduce the risk of oral cancer. Patient education may improve the outcomes of OLP therapy and further reduce the risk of oral cancer in OLP patients. Although OLP may be diagnosed clinically, appropriate specialist referral is required for: (i) histological diagnosis; (ii) assessment of causative/exacerbating factors, associated diseases and oral cancer risk; (iii) patient education and management; (iv) medical treatment; and (v) long-term review and re-biopsy as required.

The pathogenesis of oral lichen planus

Both antigen-specific and non-specific mechanisms may be involved in the pathogenesis of oral lichen planus (OLP). Antigen-specific mechanisms in OLP include antigen presentation by basal keratinocytes and antigen-specific keratinocyte killing by CD8(+) cytotoxic T-cells. Non-specific mechanisms include mast cell degranulation and matrix metalloproteinase (MMP) activation in OLP lesions. These mechanisms may combine to cause T-cell accumulation in the superficial lamina propria, basement membrane disruption, intra-epithelial T-cell migration, and keratinocyte apoptosis in OLP. OLP chronicity may be due, in part, to deficient antigen-specific TGF-beta1-mediated immunosuppression. The normal oral mucosa may be an immune privileged site (similar to the eye, testis, and placenta), and breakdown of immune privilege could result in OLP and possibly other autoimmune oral mucosal diseases. Recent findings in mucocutaneous graft-versus-host disease, a clinical and histological correlate of lichen planus, suggest the involvement of TNF-alpha, CD40, Fas, MMPs, and mast cell degranulation in disease pathogenesis. Potential roles for oral Langerhans cells and the regional lymphatics in OLP lesion formation and chronicity are discussed. Carcinogenesis in OLP may be regulated by the integrated signal from various tumor inhibitors (TGF-beta 1, TNF-alpha, IFN-gamma, IL-12) and promoters (MIF, MMP-9). We present our recent data implicating antigen-specific and non-specific mechanisms in the pathogenesis of OLP and propose a unifying hypothesis suggesting that both may be involved in lesion development. The initial event in OLP lesion formation and the factors that determine OLP susceptibility are unknown.

Telomerase activity detected in oral lichen planus by RNA in situ hybridisation: not a marker for malignant transformation

BACKGROUND

Oral lichen planus (OLP) is a chronic inflammatory condition. Clinically, it is characterised by the presence of a white lace-like lesion on the buccal mucosa, tongue, and gingivae, with erosions and ulceration. The World Health Organisation considers OLP to be a premalignant condition.

AIMS

To investigate expression of the telomerase RNA component (hTR) in OLP compared with normal control buccal mucosa and to assess the possibility of using hTR expression as a marker for malignant transformation in OLP.

METHODS

hTR expression was analysed in 40 cases of OLP and 18 normal control buccal mucosa samples using an RNA in situ hybridisation approach.

RESULTS

Strong hTR RNA expression was seen in the basal, suprabasal, and to a lesser extent in the upper epithelial layers in 36 of the 40 OLP lesions examined. Infiltrating subepithelial lymphocytes in OLP were also shown to express hTR RNA. Weak hTR RNA expression was seen in seven of the 18 normal control buccal mucosa specimens, with expression confined exclusively to the basal layer of the epithelium and absent in the suprabasal and upper layers.

CONCLUSION

The telomerase RNA component hTR is found to be highly expressed in the epithelium of non-dysplastic OLP lesions. It is possible that this high expression is related to the increased cellular proliferation seen in OLP lesions rather than being an indicator of susceptibility to malignancy. Thus, hTR RNA expression may not be a suitable marker for predicting malignant transformation in OLP.

Matrix metalloproteinases and their inhibitors in oral lichen planus

BACKGROUND

Oral lichen planus (OLP) is characterized by a sub-epithelial lymphocytic infiltrate, basement membrane (BM) disruption, intra-epithelial T-cell migration and apoptosis of basal keratinocytes. BM damage and T-cell migration in OLP may be mediated by matrix metalloproteinases (MMPs).

METHODS

We examined the distribution, activation and cellular sources of MMPs and their inhibitors (TIMPs) in OLP using immunohistochemistry, ELISA, RT-PCR and zymography.

RESULTS

MMP-2 and -3 were present in the epithelium while MMP-9 was associated with the inflammatory infiltrate. MMP-9 and TIMP-1 secretion by OLP lesional T cells was greater than OLP patient (p < 0.01) and healthy control subject (p < 0.001) peripheral blood T cells. MMP-9 and TIMP-1 mRNA levels were greater in OLP lesional T cells compared with healthy control subject peripheral blood T cells p < 0.01). Tumor necrosis factor (TNF)-alpha upregulated OLP lesional T-cell MMP-9 (not TIMP-1) mRNA and secretion (p < 0.05). The in vitro activation rate of MMP-9 from OLP lesional T cells was greater than that from OLP peripheral blood T cells (p < 0.05).

CONCLUSION

T-cell-derived MMP-9 may be involved in the pathogenesis of OLP. Relative over-expression of MMP-9 (compared with TIMP-1) may cause BM disruption and facilitate intra-epithelial T-cell migration in OLP.

Expression of alpha(v)beta6 integrin in oral leukoplakia

The distribution of alpha(v)beta6 integrin was examined in oral leukoplakia, lichen planus and squamous cell carcinomas using immunohistochemistry. Controls included oral mucosal wounds, chronically inflamed and normal oral mucosa. Integrins beta1, beta3, beta4, beta5, fibronectin and tenascin were also studied. The integrin alpha(v)beta6 was highly expressed throughout the whole lesion of 90% of the squamous cell carcinomas but was not present in any of the normal specimens. alpha(v)beta6 integrin was also expressed in 41% of the leukoplakia specimens, and 85% of the lichen planus samples, but in none of the tissues with inflammatory hyperplasia or chronic inflammation. The expression of beta1 integrins was localized in the basal layer, and that of the beta4 at the cell surface facing the basement membrane of all specimens. The integrins beta3 and beta5 were absent from all normal and leukoplakia specimens. Fibronectin and tenascin were present in the connective tissue underneath the epithelium of all the sections, and their expression was similar in both alpha(v)beta6-positive and alpha(v)beta6-negative tissues. A group of 28 leukoplakia patients were followed 1-4 years after first diagnosis. In this group, initially alpha(v)beta6 integrin-positive leukoplakia specimens had high tendency for disease progression while alpha(v)beta6-negative specimens did not progress. These results suggest that the expression of alpha(v)beta6 integrin could be associated in the malignant transformation of oral leukoplakias.

Lichen planus

Lichen Planus is a relatively common inflammatory dermatosis of unknown origin. The present review summarizes the histological and clinical features of lichen planus and variants, including lichenoid drug reactions, are described. Possible mechanisms of pathogenesis of lichen planus are reviewed. The development of malignancy in association with lichen planus and the association with hepatitis are discussed. Treatment options for the more difficult manifestations of lichen planus are proposed.

Matrix metalloproteinases in skin

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases collectively capable of degrading essentially all extracellular matrix components. These enzymes can be produced by several different types of cells in skin such as fibroblasts, keratinocytes, macrophages, endothelial cells, mast cells, and eosinophils and their activity can be specifically inhibited by TIMPs (tissue inhibitors of metalloproteinases), which bind to active MMPs with 1:1 stoichiometry. In general, MMPs are not constitutively expressed in skin but are induced temporarily in response to exogenous signals such as various cytokines, growth factors, cell matrix interactions and altered cell-cell contacts. At present, more evidence is accumulating that MMPs play an important role in proteolytic remodeling of extracellular matrix in various physiologic situations, including developmental tissue morphogenesis, tissue repair, and angiogenesis. On the other hand, MMPs play an important pathogenetic role in excessive breakdown of connective tissue components, e.g. in rheumatoid arthritis, osteoarthritis, chronic ulcers, dermal photoageing, and periodontitis, as well as in tumor cell invasion and metastasis. In this review we discuss the role of MMPs and TIMPs in human skin based on new observations on the regulation of the expression of MMPs, on their substrate specificity, and MMP expression in physiologic and pathologic conditions of skin involving matrix remodeling. Furthermore, therapeutic modalities based on regulating MMP activity will be reviewed.

Distribution and synthesis of type VII collagen in oral squamous cell carcinoma

The distribution of the basement membrane anchoring fibril component type VII collagen was studied in oral squamous cell carcinoma by using in situ hybridization and immunohistochemical methods. The expression of type VII collagen in oral normal mucosa, lichen planus and epithelial dysplasias was also investigated. In squamous cell carcinomas, the signals for type VII collagen mRNA were located exclusively in malignant peripheral cells in tumour islands and in fibroblast-like cells among the stromal tissue. In normal buccal mucosa, type VII collagen mRNA expression was located in basal epithelial cells. In oral lichen planus and epithelial dysplasias, the signals for type VII collagen mRNA were also located in basal keratinocytes; however, the signal was especially strong in some epithelial cells. In oral squamous cell carcinomas, the linear immunohistochemical staining pattern of type VII collagen was noted surrounding partly squamous epithelial tumour cell islands, and a large number of tumour cells showed a cytoplasmic staining reaction using the type VII collagen antibody. Some fibroblast-like stromal cells also showed a positive immunostaining reaction. In conclusion, the results of this study indicate that a high synthesis level, but an impaired distribution of type VII collagen, are highly characteristic of squamous epithelial tumour cells.

Urokinase plasminogen activator is expressed by basal keratinocytes before interstitial collagenase, stromelysin-1, and laminin-5 in experimentally induced dermatitis herpetiformis lesions

We studied the temporal expression of interstitial collagenase, stromelysin-1 and -2, and urokinase plasminogen activator (uPA) mRNAs by in situ hybridization in eight patients with dermatitis herpetiformis. To induce blisters, 50% potassium iodide patch tests were performed, and serial biopsy specimens were taken at 4, 12, and 24 h. Additional samples were taken from occasional spontaneous blisters. Components of the basement membrane, laminin-5, laminin-1, and type VII collagen, were examined immunohistochemically in relation to matrix metalloproteinase expression. At 12 h, when no blisters were seen, uPA mRNA was present in basal keratinocytes in five of eight samples, whereas interstitial collagenase and stromelysin-1 mRNA were not detected. At this time, immunohistochemistry failed to show changes in the basement membrane. At 24 h, uPA, collagenase, and stromelysin-1 mRNAs were present in basal keratinocytes, suggesting an activation of latent forms of the two latter enzymes by the uPA-plasmin pathway. Signal for stromelysin-2 was not detected. Furthermore, disruptions of laminin-1 and type VII collagen were evident. The data suggest that stromelysin-1 and interstitial collagenase may contribute to the degradation of basement membrane in dermatitis herpetiformis. Intracellular staining for laminin-5 co-localized with collagenase mRNA in basal keratinocytes. Because laminin-5 is essential for adhesion of keratinocytes to basement membrane and for establishment of focal adhesions on migrating cells, its production may reflect a regenerative response after the destruction of basement membrane components.

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.

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.