Immunolocalizations of human gelatinase (type IV collagenase, MMP-9) and TIMP (tissue inhibitor of metalloproteinases) in normal epidermis and some epidermal tumors

MMP-2, -9 and TIMP-1, -2 assays in keratinocyte cultures

To determine the status of tissue metabolism in the epidermis, matrix metalloproteinase (MMP)-2 and -9 and tissue inhibitor of metalloproteinases (TIMP)-1 and -2 can be detected using keratinocytes in culture. In addition to Western blotting analysis, gelatin zymography for MMP-2 and -9 and the reverse zymography for TIMP-1 and -2 are useful methods for evaluating such protein expressions both qualitatively and quantitatively, because MMP-2 and MMP-9 are known as gelatinase. Moreover, real-time analysis for zymography can be performed using fluorescein isothiocyanate-labelled gelatin.

Suppression of matrix metalloproteinase-9 expression in undifferentiated, non-apoptotic keratinocytes is abrogated by the cleavage of poly(ADP-ribose) polymerase-1

Matrix metalloproteinase (MMP)-9, an enzyme that degrades the extracellular matrix, has been implicated as a key enzyme in the process of tissue remodeling. This study demonstrates the regulation of MMP-9 transcription through a gene regulatory element in its promoter (the KRE-M9 element). The KRE-M9-binding protein was purified and identified as poly(ADP-ribose) polymerase-1 (PARP-1), which inhibits the transcription of MMP-9 similar to involucrin. This regulation occurs in non-apoptotic keratinocytes using the distinctive culture conditions of high and low Ca(2+) levels. PARP cleavage, which occurs during apoptosis, results in de-repression of MMP-9 promoter activity. These data clarify a new role of PARP-1 and suggest a physiologically relevant connection between caspase activation and MMP-9 expression.

Expression of matrix metalloproteinase-1, -9, -13, and tissue inhibitor of metalloproteinases-1 in basal cell carcinomas of the eyelid

BACKGROUND

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) function in the remodelling of the extracellular matrix in morphogenesis, angiogenesis, tissue repair, and tumor invasion. Elevated levels of distinct MMPs in tumor tissue are related to worse prognosis. However, no overall consistent pattern of expression in human cancer has been identified. The aim of the present study was to evaluate the expression of MMP-1, -9, -13 and TIMP-1 in tumor epithelial cells and surrounding connective tissue in primary basal cell carcinomas (BCC) of the eyelid, and to assess their role as prognostic markers for tumor recurrence.

METHODS

Surgical specimens of 49 histologically proven primary BBCs of the eyelid of different histological subtypes were included. Immunohistological studies were performed using antibodies against MMP-1, MMP-9, MMP-13 and TIMP-1, and staining intensity was analyzed semi-quantitatively.

RESULTS

MMP-1, -9, -13, and TIMP-1 were expressed at various intensities in epithelial tumor cells and surrounding stromal cells including fibroblasts, inflammatory cells, and vascular endothelial cells in all tumor subtypes. Staining was especially prominent at the invading edge of the BCC. A statistically significant correlation was seen between increased TIMP-1 expression in tumor and/or stromal cells with the presence of MMP-13 (p = 0.007 and p < 0.0001 respectively). Moreover, TIMP-1 expression in tumor and/or stroma was significantly associated with relapse (p = 0.012 and p = 0.042 respectively).

CONCLUSION

MMP-9, MMP-13 and TIMP-1 expression may serve as a prognostic marker for early tumor invasiveness. Moreover, up-regulation of TIMP-1 in tumor and/or surrounding stromal cells may indicate an increased risk for BCC recurrence.

AGE-modified collagens I and III induce keratinocyte terminal differentiation through AGE receptor CD36: epidermal-dermal interaction in acquired perforating dermatosis

To clarify the molecular mechanism underlying the transepidermal extrusion of dermal collagen in acquired perforating dermatosis (APD) associated with diabetes mellitus and renal failure, we studied the interaction between advanced glycation end product (AGE)-modified extracellular matrix proteins and keratinocytes (KCs) in a cell culture system. The expression of involucrin (INV) and keratin 10 was significantly enhanced in normal human KCs grown on AGE-modified collagen I or III compared with cells grown on unmodified collagen I or III. Glycated collagens I and III preferentially induced the expression of AGE receptor CD36, but not of other AGE receptors. KCs induced to terminal differentiation demonstrated markedly elevated CD36 expression. Glycated collagen I- and III-induced INV expression was partially blocked by the anti-CD36 antibody (Ab). These substrates also induced epidermal matrix metalloproteinase 9 (MMP-9) expression. Lesional skin from APD patients reacted moderately or strongly with the anti-CD36 Ab as well as the anti-MMP-9 Ab in the epidermal cells surrounding the collagenous materials being eliminated. These results suggest that exposing KCs to AGE-modified interstitial collagen (types I and III) by scratching induces terminal differentiation of KCs via the AGE receptor (CD36), leading to the upward movement of KCs together with glycated collagen.

Missense polymorphisms in matrix metalloproteinase genes and skin cancer risk

Matrix metalloproteinases (MMP) degrade various components of the extracellular matrix, and their overexpression has been implicated in tumor progression. Nonsynonymous single nucleotide polymorphisms (SNPs) lead to amino acid substitutions that can alter the function of the encoded protein. We evaluated the associations of six nonsynonymous SNPs in the MMP3, MMP8, and MMP9 genes with skin cancer risk in a nested case-control study of Caucasians within the Nurses' Health Study among 218 melanoma cases, 285 squamous cell carcinoma (SCC) cases, 300 basal cell carcinoma (BCC) cases, and 870 normal controls. We observed that the MMP9 Arg668Gln polymorphism was significantly associated with a decreased risk of SCC. Compared with the Arg/Arg group, the multivariate odds ratio was 0.67 (95% confidence interval, 0.47-0.97) for the Arg/Gln group and 0.21 (95% confidence interval, 0.05-0.97) for the Gln/Gln group (P(trend) = 0.004). We did not observe any association of this SNP with the risks of melanoma and basal cell carcinoma. No associations were found for other SNPs with skin cancer risk. This study provides evidence for the contribution of the MMP9 Arg668Gln to SCC development.

The expression of metaloproteinases-2 and -9 is different according to the patterns of growth and invasion in squamous cell carcinoma of the penis

Squamous cell carcinoma (SCC) of the penis is characterized by different patterns of growth and local invasion. The matrix metalloproteinases (MMPs) is a family of proteolytic enzymes that are involved in the degradation of extracellular matrix to allow the migration of tumor cells. The present study examined whether the expression of MMP-2 and -9 is correlated with the patterns of tumor growth and invasion in penile SCC. The expression of MMP-2 and -9 was examined immunohistochemically in samples of 115 patients. The cases were divided in three groups according to the patterns of growth and invasion: group 1, exophytic growth and pushing pattern of invasion; group 2, endophytic growth and invasion in large sheets of cells; and group 3, endophytic growth and invasion in small group or isolated cells. Tumors with MMP-2 and -9 overexpression are deeply invasive and present an invasion pattern of small groups of cells. Also, expression of MMP-2 changed from membrane to cytoplasm in invasive tumors, maybe representing activation of MMP-2. These findings allow us to conclude that the less differentiated tumors, which are more invasive and with a pattern of invasion in small group of cells, are associated with the overexpression of MMPs.

Tissue-specific expression of Clec2g in mice

Estrogens regulate the proliferation and differentiation of mouse vaginal epithelial cells. We examined the temporal and spatial expression of DDV10, a novel C-type lectin during stratification and cornification of the vaginal epithelium. DDV10 was expressed in vagina but not uterus in ovariectomized mice treated with 17beta-estradiol (E2). In mouse stomach, the expression of DDV10 was detected in pars proventricularis but not in pars glandularis. Furthermore, the DDV10 gene was found to possess two transcripts, a long form (DDV10) and a short form (OCILrP1, osteoclast inhibitory lectin-related protein 1). DDV10 mRNA but not OCILrP1 mRNA was expressed in the stratified and cornified epithelial tissues. DDV10 mRNA was first detected between 12 and 18 h after E2 treatment in the vaginal epithelium, and was detected in the vagina of the neonatally diethylstilbestrol (DES)-treated mouse. Recently, a unified name was registered in GenBank (C-type lectin domain family 2, member g; Clec2 g). Taken together, these data suggest that DDV10 is the long form of Clec2 g (Clec2g-L), and DDV10/Clec2g-L may play a role in the stratification and/or cornification of epithelial cells during differentiation.

Leukocyte matrix metalloproteinase-9 is elevated and contributes to lymphocyte activation in type I diabetes

Degradation of extracellular matrix proteins by matrix metalloproteinases (MMPs) is integral to cell migration and tissue remodeling in diabetes mellitus and its complications. MMPs also regulate the function of leukocytes via proteolytic processing of cytokines/chemokines. In this study, we measured the production of MMP-9 and its natural tissue inhibitor (TIMP)-1 by leukocytes isolated from human type I diabetic patients. MMP-9 was also detected in serum and splenocytes from non-obese diabetic (NOD) and BALB/c mice. MMP-9 was markedly elevated in leukocytes from diabetics compared to non-diabetic controls. TIMP-1 production was also enhanced in leukocytes from diabetics, but substantially less than MMP-9, with the MMP-9/TIMP-1 ratio being 1.6-fold higher in neutrophils and 3-fold higher in monocytes than controls. Interleukin (IL)-2 or lipopolysaccharide (LPS) treatment increased MMP-9 production in leukocytes from both diabetics and normal controls, whereas insulin decreased MMP-9 expression. Recombinant MMP-9 stimulated the proliferation of mouse splenocytes from NOD or BALB/c and a MMP-9 inhibitor dose-dependently inhibited splenocyte proliferation. In conclusion, our results demonstrate firstly that MMP-9 expression is elevated in leukocytes from type I diabetic patients and NOD mice and secondly, that MMP-9 elevates proliferation of mouse splenocytes. These data suggest that elevated leukocyte MMP-9 may contribute to the pathogenesis of type I diabetes and its associated complications.

Leptomycin B Reduces Matrix Metalloproteinase-9 Expression and Suppresses Cutaneous Inflammation

Matrix metalloproteinase-9 (MMP-9), a type of gelatinase, plays many roles in tissue metabolism, especially in inflammation, and many regulatory elements have been reported in the promoter region of its encoding gene. Leptomycin B, which regulates the nucleo-cytoplasmic trafficking of proteins, including transcription-factor-related ones, has the potential to exert important biological effects. The addition of leptomycin B to keratinocytes in culture had no effect on matrix metalloproteinase-2 (another gelatinase) but caused the selective down-regulation of MMP-9 during the stimulation of differentiation with high Ca(2+) or transforming growth factor-beta, as well as during the stimulation of inflammation by tumor necrosis factor-alpha or interleukin-1alpha. This down-regulation depended on multiple regulatory elements in the promoter of MMP-9 including KRE-M9 (which we have recently identified), and a classical 12-o-tetradecanoyl-phorbol-13-acetate-responsive element. The topical application of leptomycin B to murine skin also effectively suppressed inflammation, including MMP-9 expression, after ultraviolet B irradiation. These results suggest that the application of leptomycin B and/or its derivatives could be useful for treating many inflammatory conditions.

Matrix Metalloproteinase 9 Expression is Coordinately Modulated by the KRE-M9 and 12-O-Tetradecanoyl-Phorbol-13-Acetate Responsive Elements

To investigate the pathophysiologic role of matrix metalloproteinase 9 (MMP-9), we analyzed the mechanism of its transcriptional regulation in keratinocytes and in HT1080 fibrosarcoma cells in culture. The KRE-M9 element, which is located between the 12-O-tetradecanoyl-phorbol-13-acetate responsive element (TRE) and the transcription initiation site in the MMP-9 promoter, is essential for MMP-9 transcription in the absence of the TRE. The KRE-M9 binding protein, however, is shown to be a repressor of transcription rather than an activator; we found several times higher transcriptional activity when the KRE-M9 element was mutated. In contrast, activator protein 1 proteins (AP-1) are shown to activate transcription of MMP-9 by binding to the TRE, which is located adjacent to the KRE-M9 element. Moreover, we found that the KRE-M9 binding protein could serve as a differentiation repressing factor 1 (DRF-1) as shown by the decrease in levels of this protein with differentiation. In addition, the TRE binding protein is able to bind to the KRE-M9 to some extent. These results indicate that the coordinated modulation of MMP-9 transcription via the TRE and the KRE-M9 elements is important in epidermal and mesenchymal tissues. Our findings could facilitate consideration of the molecular mechanism in a variety of pathophysiologic conditions with which MMP-9 is involved.

Matrix metalloproteinase 19 regulates insulin-like growth factor-mediated proliferation, migration, and adhesion in human keratinocytes through proteolysis of insulin-like growth factor binding protein-3

Unlike most other matrix metalloproteinases (MMPs) MMP-19 is expressed in undifferentiated basal keratinocytes of healthy human skin. The human keratinocyte cell line HaCaT, which like basal keratinocytes constitutively expresses MMP-19, down-regulated the expression of MMP-19 at high calcium concentrations. Calcium-regulation occurred through E-cadherin mediated cell-cell contacts because neutralizing anti-E-cadherin antibodies restored MMP-19 expression in high calcium. Overexpression of MMP-19 in HaCaT cells (HaCaT-WT) increased cellular proliferation, as well as migration and adhesion on type I collagen. This was due to proteolysis of the insulin-like growth factor (IGF) binding protein-3 by MMP-19, which augmented signaling through the IGF-I receptor, as evidenced by its increased autophosphorylation. Conversely, these effects were not observed in cells transfected with MMP-2 or a catalytically inactive MMP-19 mutant. As further proof that increased IGF-signaling promoted adhesion and migration in HaCaT-WT cells, we reproduced these effects by treating parental HaCaT with IGF-I. We observed dephosphorylation of the focal adhesion kinase in HaCaT-WT as well as IGF-I-treated HaCaT cells, suggesting that inactivating focal adhesion kinase is a mechanism by which IGF-I enhances adhesion. Furthermore, IGF-I-triggered motility on type I collagen was mediated by MMP activity, which, however, was distinct from MMP-19. Considering the coexpression of IGFBP-3 and MMP-19 in the skin, we conclude that MMP-19 is a likely candidate to be the major IGFBP-3 degrading MMP in the quiescent epidermis. This activity might have widespread consequences for the behavior of epidermal keratinocytes.

Induction of matrix metalloproteinase-9 secretion from human keratinocytes in culture by ultraviolet B irradiation

BACKGROUND

Matrix metalloproteinases (MMPs) are known as important enzymes involved in tissue metabolism. Among them, MMP-2 and MMP-9 are termed gelatinases, but their specific roles in vivo are still unknown, including their expression patterns following ultraviolet (UV) irradiation.

OBJECTIVE

To elucidate the effects of UV irradiation on the skin, we analyzed the expression of MMP-2 and MMP-9 by primary human keratinocytes in culture.

METHODS

We evaluated the enzymatic functions of MMP-2 and MMP-9 by gelatin-zymography, and of MMP-9 expression by immunofluorescence, using cultured keratinocytes after UV irradiation.

RESULTS

The secretion of MMP-2 (72 kDa) remained at low levels under all conditions examined. Although MMP-9 (92 kDa) secretion was not induced by UVA, it was stimulated by UVB irradiation in a dose-dependent manner. In addition, an enzyme-linked immunosorbent assay showed the tendency to increase for the involucrin expression following UVB exposure. Cell viability was decreased by UVB irradiation in contrast to the induction of MMP-9 and involucrin.

CONCLUSION

These results suggest that the induction of MMP-9 secretion is related to the inflammation including apoptosis of keratinocytes resulting from UVB irradiation.

UVA-mediated downregulation of MMP-2 and MMP-9 in human epidermal keratinocytes

While human dermal fibroblasts increase the expression and secretion of distinct matrix metalloproteinases (MMPs) in response to ultraviolet (UV) irradiation, much less is known about regulation of MMPs with regard to normal human epidermal keratinocytes (NHEK). In this in vitro study, the effect of ultraviolet A (UVA) irradiation on gelatinase expression and secretion by NHEK was investigated. Irradiation of NHEK with non-toxic doses of UVA resulted in a dose-dependent downregulation of MMP-2 (gelatinase A) and MMP-9 (gelatinase B). A single dose of 30JUVA/cm(2) lowered MMP-2 activity to 26% and MMP-9 activity to 33% compared with mock-irradiated cells at 24h after irradiation. Downregulation of MMP-2 and MMP-9 steady-state mRNA levels was observed at 4h after UVA irradiation. The inhibitory effect of UVA on gelatinases was mediated by UVA-generated singlet oxygen (1O(2)). These findings suggest an inverse response to UVA irradiation in NHEK than in fibroblasts.

Estrogen-independent expression of neuropsin, a serine protease in the vagina of mice exposed neonatally to diethylstilbestrol

Perinatal treatment of female mice with natural or synthetic estrogens including diethylstilbestrol (DES) results in estrogen-independent persistent proliferation and cornification of the vaginal epithelium. However, the molecular mechanisms of the estrogen-independent changes have not been elucidated. To analyze the mechanism of estrogen-independent cell proliferation and cornification of the vaginal epithelium, we used differential display and determined specific genes expressed in neonatally DES-treated vagina. A candidate clone that designated DDV5 was identical to the serine protease, neuropsin that is reportedly expressed in the mouse central nervous system. We then analyzed the expression pattern of DDV5/neuropsin using Northern blot analysis. We found: (1). DDV5/neuropsin mRNA is expressed in vaginae from neonatally DES-treated ovariectomized mice but not in vaginae from ovariectomized control mice, (2). its expression is not detected in uteri from neonatally DES-treated mice, (3). DDV5/neuropsin is expressed in vaginae from normal intact mice during estrus. Furthermore, we found that DDV5/neuropsin mRNA rapidly decreased in vaginae after ovariectomy. DDV5/neuropsin was detected in vaginae from ovariectomized mice 48 h after estrogen treatment. These results suggest that DDV5/neuropsin is expressed in estrogen-stimulated mouse vagina, and its gene expression is regulated by estrogen. Neonatal DES exposure affects transcriptional control of DDV5/neuropsin in the mouse vagina, which results in persistent expression of DDV5/neuropsin even after ovariectomy, thus, DDV5/neuropsin may play a role in estrogen-independent persistent proliferation and cornification of the vaginal epithelium. Using in situ hybridization method, we found DDV5/neuropsin mRNA localized in epithelial cells but not stromal cells in vaginae. This is the first report on the gene expression of a serine-protease neuropsin in the mouse vagina, and as a marker of the estrogen-independent persistent proliferation and cornification of the vaginal epithelium.

A novel mechanism of matrix metalloproteinase-9 gene expression implies a role for keratinization

To investigate the pathophysiological role of matrix metalloproteinase (MMP)-9 in the skin, we analyzed MMP-9 expression from human keratinocytes in culture. MMP-9 and the terminal differentiation marker involucrin were co-localized in the same keratinocytes with a high concentration of Ca(2+), a potent stimulator of differentiation. We identified the novel KRE-M9 element, further downstream to the previously reported TPA responsive element in the MMP-9 promoter, and both of these two elements were shown to be important for MMP-9 transcription and Ca(2+) induction. The concomitant upregulation of MMP-9 and involucrin transcripts was probably due to the very similar gene regulatory elements, KRE-M9 and KRE-4, in their respective promoters. These results indicate a novel mechanism of transcriptional regulation for MMP-9 in the process of keratinization, implying the probable association of apoptosis and differentiation of keratinocytes in epidermal skin tissue.

Systematic separation and purification of elastase, gelatinase (matrix metalloproteinase 9), and collagenase (matrix metalloproteinase 8) from polymorphonuclear leukocytes in dialyzers previously used by patients with renal failure

We developed a simple and effective method for the systematic separation and purification of human polymorphonuclear leukocyte (PMN) proteinases, elastase, gelatinase (matrix metalloproteinase 9, type IV collagenase), and collagenase (matrix metalloproteinase 8), derived from the extracts of hollow fiber dialyzers that had been utilized in the treatment of patients with renal failure. The fraction containing elastase was grossly separated from that containing gelatinase and collagenase by heparin-Sepharose chromatography and purified in an aprotinin column. The remaining two enzymes were then separated using the gelatin-Sepharose column after gel chromatography following ammonium sulfate precipitation. Gelatinase and collagenase were further purified by gelatin-Sepharose chromatography as a latent form and by collagen-Sepharose chromatography as an activated form. This novel method offers procedural advantages over existing methods that separate PMNs from the whole blood of volunteers for experimental research purposes.

Collagenolytic and gelatinolytic matrix metalloproteinases and their inhibitors in basal cell carcinoma of skin: comparison with normal skin

Tissue from 54 histologically-identified basal cell carcinomas of the skin was obtained at surgery and assayed using a combination of functional and immunochemical procedures for matrix metalloproteinases (MMPs) with collagenolytic activity and for MMPs with gelatinolytic activity. Collagenolytic enzymes included MMP-1 (interstitial collagenase), MMP-8 (neutrophil collagenase) and MMP-13 (collagenase-3). Gelatinolytic enzymes included MMP-2 (72-kDa gelatinase A/type IV collagenase) and MMP-9 (92-kDa gelatinase B/type IV collagenase). Inhibitors of MMP activity including tissue inhibitor of metalloproteinases-1 and -2 (TIMP-1 and TIMP-2) were also assessed. All three collagenases and both gelatinases were detected immunochemically. MMP-1 appeared to be responsible for most of the functional collagenolytic activity while gelatinolytic activity reflected both MMP-2 and MMP-9. MMP inhibitor activity was also present, and appeared, based on immunochemical procedures, to reflect the presence of TIMP-1 but not TIMP-2. As a group, tumours identified as having aggressive-growth histologic patterns were not distinguishable from basal cell carcinomas with less aggressive-growth histologic patterns. In normal skin, the same MMPs were detected by immunochemical means. However, only low to undetectable levels of collagenolytic and gelatinolytic activities were present. In contrast, MMP inhibitor activity was comparable to that seen in tumour tissue. In previous studies we have shown that exposure of normal skin to epidermal growth factor in organ culture induces MMP up-regulation and activation. This treatment concomitantly induces stromal invasion by the epithelium (Varani et al (1995) Am J Pathol 146: 210-217; Zeigler et al (1996b) Invasion Metastasis 16: 11-18). Taken together with these previous data, the present findings allow us to conclude that the same profile of MMP/MMP inhibitors that is associated with stromal invasion in the organ culture model is expressed endogenously in basal cell carcinomas of skin.

A case of angiokeratoma circumscriptum: immunolocalization of matrix metalloproteinase (MMP)-9

We report a case of angiokeratoma circumscriptum which we have followed for one year. The skin lesion initially showed erythema and then changed to a dark reddish, raised, keratotic nodule. The lesion histologically showed dilated capillaries and hyperkeratosis. Using immunohistochemistry, matrix metalloproteinase (MMP)-9 was localized in the epidermis just under the horny layer, particularly in the hyperkeratotic lesion. The expression of MMP-9 might be related to the hyperkeratotic changes in this lesion.

Human collagenase-3 is expressed in malignant squamous epithelium of the skin

Co-expression of several members of the matrix metalloproteinase (MMP) family is a characteristic of human carcinomas. To investigate the role of the recently cloned collagenase-3 (MMP-13) in epidermal tumors, we studied samples representing malignant (basal and squamous cell carcinoma, Paget's disease), pre-malignant (Bowen's disease, solar keratosis), and benign (keratoacanthoma, seborrheic keratosis, linear epidermal nevus) tumors. Basal cell carcinomas expressed collagenase-3 mRNA in focal areas of keratinized cells, the squamous differentiation of which was confirmed by positive immunostaining for involucrin. Apoptosis was observed in central parts of these foci. In squamous cell carcinomas, collagenase-3 expression was detected at the epithelial tumor front and less frequently in the surrounding stromal cells. Collagenase-3 mRNA co-localized with immunostaining for laminin-5, an adhesion molecule suggested to participate in the migration of tumor cells. The pre-malignant and benign tumors were mostly negative for collagenase-3. Stromelysin-1, a potential activator of latent collagenases, was frequently expressed by stromal cells surrounding the malignant tumors, and the two MMPs occasionally co-localized in keratotic foci. Our results demonstrate that in basal cell carcinomas, expression of collagenase-3 is associated with terminal differentiation of epithelial cells. Furthermore, the gene is activated during skin carcinogenesis, and we suggest a role for collagenase-3 in degradation of the extracellular matrix associated with malignant epithelial growth.

Secretion of different types of gelatinases from cultured human keratinocytes

We investigated gelatinolytic enzymes derived from cultured human keratinocytes. Using a zymograph, we detected 92 kDa and 72 kDa gelatinases as major components and 83 kDa as a minor component from a conditioned cultured medium (BSL-K110, Kyokutoseiyaku Co.) of keratinocytes. After several passages, the 72 kDa band disappeared, and the 83 kDa band became dominant in another conditioned culture medium (K-GM, Kurashikibouseki Co.); these keratinocytes had a relatively differentiated appearance. These results suggest that some mechanism may regulate the secretion of selected types of gelatinase from keratinocytes under different conditions.