Cell migration is essential for sustained growth of keratinocyte colonies: the roles of transforming growth factor-alpha and epidermal growth factor

Induction of extracellular matrix gene expression in normal human keratinocytes by transforming growth factor beta is altered by cellular differentiation

Changes in epithelial substrate have been related to the cellular capacity for proliferation and to changes in cellular behavior. The effect of TGF beta 1 on the expression of the basement membrane genes, fibronectin, laminin B1, and collagen alpha 1 (IV), was examined. Northern analysis revealed that treatment of normal human epidermal keratinocytes with 100 pM TGF beta 1 increased the expression of each extracellular matrix (ECM) gene within 4 h of treatment. Maximal induction was reached within 24 h after treatment. The induction of ECM mRNA expression was dose dependent and was observed at doses as low as 1-3 pM TGF beta 1. Incremental doses of TGF beta 1 also increased cellular levels of fibronectin protein in undifferentiated keratinocytes and resulted in increased secretion of fibronectin. Squamous-differentiated cultures of keratinocytes expressed lower levels of the extracellular matrix RNAs than did undifferentiated cells. Treatment of these differentiated cells with TGF beta 1 induced the expression of fibronectin mRNA to levels seen in TGF beta-treated, undifferentiated keratinocytes but only marginally increased the expression of collagen alpha 1 (IV) and laminin B1 mRNA. The increased fibronectin mRNA expression in the differentiated keratinocytes was also reflected by increased accumulation of cellular and secreted fibronectin protein. The inclusion of cycloheximide in the protocol indicated that TGF beta induction of collagen alpha 1 (IV) mRNA was signaled by proteins already present in the cells but that TGF beta required the synthesis of a protein(s) to fully induce expression of fibronectin and laminin B1 mRNA. The differential regulation of these genes in differentiated cells may be important to TGF beta action in regulating reepithelialization.

Polarized expression of integrin receptors (alpha 6 beta 4, alpha 2 beta 1, alpha 3 beta 1, and alpha v beta 5) and their relationship with the cytoskeleton and basement membrane matrix in cultured human keratinocytes

In human keratinocytes cultured in conditions which allow differentiation and stratification and are suitable to reconstitute a fully functional epidermis, alpha 6 beta 4 and two members of the beta 1 integrin family (alpha 2 beta 1 and alpha 3 beta 1) were respectively polarized to the basal and lateral domains of the plasmamembrane both in growing colonies and in the reconstituted epidermis. Conversely, the alpha v integrin subunit, presumably in association with beta 5, was expressed at the basal surface in growing and migrating but not in stationary keratinocytes. The integrin alpha 6 beta 4: (a) was organized in typical patches which often showed a "leopard skin" pattern where spots corresponded to microfilament-free areas; (b) was not associated with focal contacts containing vinculin and talin but rather corresponded to relatively removed contact areas of the basal membrane as shown by interference reflection microscopy; and (c) was coherent to patches of laminin secreted and deposited underneath the ventral membrane of individual cells. The two beta 1 integrins (alpha 2 beta 1 and alpha 3 beta 1), both endowed with laminin receptor properties, were not associated with focal adhesions under experimental conditions allowing full epidermal maturation but matched the lateral position of vinculin (but not talin), cingulin, and desmoplakin, all makers of intercellular junctions. Often thin strips of laminin were observed in between the lateral aspects of individual basal keratinocytes. The integrin complex alpha v beta 5 had a topography similar to that of talin- and vinculin-containing focal adhesions mostly in the peripheral cells of expanding keratinocyte colonies and in coincidence with fibronectin strands. The discrete topography of beta 1 and beta 4 integrins has a functional role in the maintenance of the state of aggregation of cultured keratinocytes since lateral aggregation was impaired by antibodies to beta 1 whereas antibodies to beta 4 prevented cell-matrix adhesion (De Luca, M., R. N. Tamura, S. Kajiji, S. Bondanza, P. Rossino, R. Cancedda, P. C. Marchisio, and V. Quaranta. Proc. Natl. Acad. Sci. USA. 87:6888-6892). Moreover, the surface polarization of integrins followed attachment and depended both on the presence of Ca2+ in the medium and on the integrity of the cytoskeleton. We conclude that our in vitro functional tests and structural data suggest a correlation between the pattern of integrin expression on defined plasmamembrane domains and the mechanism of epidermal assembly.

Growth factor-independent proliferation of normal human neonatal keratinocytes: production of autocrine- and paracrine-acting mitogenic factors

When normal human foreskin keratinocytes were cultured in the absence of polypeptide growth factors at densities above 5 x 10(3)/cells cm2, the cells proliferated continuously and the addition of IGF-I, EGF, TGF alpha, bFGF, or aFGF did not significantly alter growth rate. Heparin sulfate, TGF beta, or suramin inhibited keratinocyte growth factor-independent proliferation. The addition of EGF, TGF alpha, or aFGF reversed heparin-induced growth inhibition, while bFGF partially negated this effect. RIA of keratinocyte-derived conditioned medium (CM) indicated the presence of TGF alpha peptide at a concentration of approximately 235 pg/ml. In contrast, clonal growth of keratinocytes required the addition of growth factors to the basal medium. Keratinocyte-derived CM replaced EGF in stimulating keratinocyte clonal growth, and an anti-EGF receptor mAb inhibited CM-induced keratinocyte clonal growth. In addition to its effect on keratinocytes, keratinocyte-derived CM stimulated the incorporation of [3H]thymidine by quiescent cultures of human foreskin fibroblasts, mouse AKR-2B cells, and EGF-receptorless mouse NR6 cells. CM-stimulated [3H]thymidine incorporation into quiescent normal human fibroblasts was partially reduced in the presence of anti-EGF receptor mAb. Heparin sulfate partially inhibited CM-induced keratinocyte clonal growth and [3H]thymidine incorporation into quiescent AKR-2B cells. We hypothesize from these data that autocrine and paracrine-acting factors produced by keratinocytes mediated their effect through the activation of both EGF receptor-dependent and EGF receptor-independent mitogenic pathways and that some of these factors appear to be sensitive to inhibition by heparin.

Transforming growth factor-alpha augments meiotic maturation of cumulus cell-enclosed mouse oocytes

Growth factors have been shown to play an important role in the regulation of ovarian function. In this study, we examined the effects of transforming growth factor-alpha (TGF-alpha) on the meiotic maturation of immature mouse oocytes in vitro. Cumulus cell-enclosed oocytes were exposed to TGF-alpha with or without the meiotic inhibitor hypoxanthine (HX), and oocyte maturation was assessed by germinal vesicle breakdown (GVBD). Likewise, mechanically denuded oocytes were examined for GVBD following exposure to HX and TGF-alpha. When cumulus cell-enclosed oocytes were exposed to TGF-alpha (1 microgram/ml) in the presence of HX (4 mM), an increase in GVBD was observed first after 5 hours of culture. Maximal stimulation was reached at 24 hours when 70% of the oocytes underwent maturation in the presence of TGF-alpha and HX as compared to 33% with HX only. Concentrations of TGF-alpha as low as 0.1 ng/ml produced a similar stimulatory response after 24 hours of culture. Spontaneous maturation in the presence of TGF-alpha, but without HX, was also enhanced. The stimulation of GVBD by TGF-alpha showed an increase over time both with and without HX. When denuded oocytes were exposed to TGF-alpha in the presence of HX, no effect was observed. Our results suggest that TGF-alpha is a potent stimulator of mouse oocyte maturation in vitro and that its effect is mediated by the surrounding cumulus cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of epidermal growth factor mRNA in the developing mouse mandibular process

Reverse transcription and cDNA amplification (polymerase chain reaction) of total RNA preparations were used to characterize the expression of EGF mRNA in the mandibular arch of day 9-17 mouse embryos. EGF mRNA was present in mandibles at day 9 and 10 but not at days 11-17. Separate RNA preparations from epithelium and mesenchyme at day 10 revealed EGF mRNA in both components.

Transforming growth factor (TGF)-alpha in human milk

Transforming growth factor (TGF)-alpha and epidermal growth factor (EGF) were measured in human milk by means of homologous radioimmunoassay. As previously reported, EGF concentration in the colostrum was approximately 200 ng/ml and decreased to 50 ng/ml by day 7 postpartum. The value of immunoreactive (IR)-TGF-alpha was 2.2-7.2 ng/ml, much lower than that of EGF. In contrast to EGF, the concentration of IR-TGF-alpha was fairly stable during the 7 postpartum days. There was no relationship between the concentrations of IR-TGF-alpha and IR-EGF, suggesting that the regulatory mechanism in the release of the two growth factors is different. On gel-chromatography using a Sephadex G-50 column, IR-EGF appeared in the fraction corresponding to that of authentic human EGF, while 70%-80% of the IR-TGF-alpha was eluted as a species with a molecular weight greater than that of authentic human TGF-alpha. Although the physiological role of TGF-alpha in milk is not known, it is possible that it is involved in the development of the mammary gland and/or the growth of newborn infants.

Alternative patterns of mitogenesis and cell scattering induced by acidic FGF as a function of cell density in a rat bladder carcinoma cell line

The dual function exerted by acidic fibroblast growth factor (aFGF) in a rat bladder carcinoma cell line has been explored under two different conditions of culture density. At low cell density, aFGF promotes the epithelium-to-mesenchyme transition of NBT-II cells characterized by cell dissociation, morphological changes toward a fibroblastic-like phenotype, and acquisition of cell motility. Under these conditions, NBT-II cells are unresponsive to the growth-promoting effect of aFGF. At high cell density, aFGF is a potent mitogenic factor, but its scattering activity is essentially abrogated. Slight modifications in the binding of aFGF to its specific receptors were observed at high cell density; these changes correlated with a downregulation of receptors with no apparent change in their molecular form. NBT-II cells located at the edge of artificial wounds mimicked the behavior of subconfluent cells, because they did not proliferate upon aFGF treatment. Furthermore, in large-sized NBT-II colonies, peripheral cells were the first to dissociate in response to aFGF. Altogether, our results suggest that the cellular response to multifunctional growth factors might depend on the localization within the responding cell population.

Expression of transfected transforming growth factor alpha induces a motile fibroblast-like phenotype with extracellular matrix-degrading potential in a rat bladder carcinoma cell line

Acquisition of cell motility is often correlated with the malignant progression of a transformed cell. To investigate some of the mechanisms involved in the development of a migratory state, we transfected the NBTII rat carcinoma cell line, which forms stationary epithelial clusters in culture, with the gene encoding human transforming growth factor alpha (TGF alpha). Expression of TGF alpha in NBTII cells resulted in cells of motile and vimentin-positive phenotype with internalized desmosomal components, analogous to the treatment of cells with exogenous TGF alpha. The clones expressed a 5.2-kb TGF alpha message and synthesized an 18-kDa form of TGF alpha. Supernatants of TGF alpha-producing clones induced the internalization of desmosomal components, the production of vimentin, and increased motility in untransfected epithelial NBTII cells, indicating that the factor produced by the clones was in a biologically active form. TGF alpha-producing clones secreted significant levels of a 95-kDa gelatinolytic metal-loproteinase, virtually absent in untransfected cell supernatants. In contrast, levels of inhibitors of metalloproteinases and of a plasminogen activator were similar in untransfected and TGF alpha-transfected NBTII cells. These results suggest that expression of TGF alpha in an epithelial tumor cell results in the development of a motile, fibroblast-like phenotype with matrix-degrading potential, which could result in a more aggressive tumor in vivo.

In situ distribution of transforming growth factor alpha in normal human tissues and in malignant tumours of the ovary

The distribution of transforming growth factor alpha (TGF-alpha) in human normal tissues from the uterus, Fallopian tube, ovary, small and large intestine, lung, spleen, kidney, and skin was studied by immunohistochemistry. TGF-alpha was found in epidermis, bronchial epithelium, intestinal mucosa, renal tubules, endo- as well as in exocervical and endometrial epithelium, and in the serous epithelium of the Fallopian tube. No TGF-alpha was detected in the stromal components of any of the tissues nor in any of the pre- and post-menopausal ovaries studied. Twenty-nine ovarian tumours including 23 ovarian carcinomas, one malignant mixed Mullerian tumour, two ovarian metastases of gastrointestinal carcinomas, one dysgerminoma, one sarcoma, and one fibroma were studied for TGF-alpha by the same immunohistochemical method. In 25 cases, specific cytoplasmic staining for TGF-alpha of epithelial tumour cells could be demonstrated. The pattern and intensity of the TGF-alpha immunostain varied among the TGF-alpha-positive tumours. No TGF-alpha was found by immunohistochemistry in the remaining four cases nor in the stromal tumour components of any of the lesions studied. Northern blot analysis for TGF-alpha mRNA was performed on 12 of the tumours. While the immunohistochemistry and blotting results correlated well in ten cases, discordant results were obtained in two lesions.

Treatment of leg ulcers with an allogeneic cultured-keratinocyte-collagen dressing

A living cellular allogeneic dressing made up of cultured keratinocytes adhering to a collagen film was used to treat 20 leg ulcers of various aetiologies in 16 patients. A reduction in pain was noted in 80% of cases, and promotion of granulation tissue in the ulcer bed in 70% of cases. In 10 patients, epithelialization of 71 +/- 29% of the ulcer was noted at Day 30.

Isolation of a GC-rich cDNA identifying mRNA present in human epidermis and modulated by calcium and retinoic acid in cultured keratinocytes. Homology with murine loricrin mRNA

Differential screening of a human epidermal cDNA library led to the isolation of cDNA clones homologous to mRNAs specifically expressed in epidermis but weakly or not expressed in the undifferentiated squamous carcinoma cell line TR146. One of these 'differentiation-specific' cDNA clones, A8, hybridized with a 1.7 kb transcript among RNAs isolated from normal human epidermis, but with several transcripts ranging from 1.4 to 2.1 kb when mRNAs were isolated from cultured keratinocytes. We examined the effects of modulators of epidermal differentiation such as calcium and retinoic acid on the production of these transcripts. Their amount was found to increase in the presence of high calcium concentration, but to decrease in the presence of retinoic acid. These results strongly suggest that A8 messages are up-regulated during epidermal differentiation. The sequence of the 1371 bp of A8 cDNA shows a very high GC content. Because of its homology with the murine loricrin mRNA, A8 is likely to correspond either to the human loricrin or to a related protein.

Transcription factor PEA3 participates in the induction of urokinase plasminogen activator transcription in murine keratinocytes stimulated with epidermal growth factor or phorbol-ester

Keratinocytes in culture represent cells which exhibit continued and controlled growth in the organism. We have investigated the synthesis of urokinase plasminogen activator mRNA in exponentially growing cultures of primary murine keratinocytes and the keratinocyte cell line BALB/MK. The tumor promotor 12-O-tetradecanoyl phorbol-13-acetate (TPA) and epidermal growth factor (EGF) induced urokinase mRNA synthesis. We made a series of progressive 5' deletions as well as internal deletions in the region upstream of the murine uPA gene. These were joined to the cat reporter gene, and used to map the TPA and EGF responsive regions of the promoter. We found both responsive sequences within a 90 base pair Hae III fragment, located 2.4 kb. upstream of the mRNA cap site. This DNA fragment conferred TPA inducibility on reporter gene expression independent of its distance and orientation to the transcription initiation site. Footprinting and gel retardation studies identified the responsible sequence to be a binding site for PEA3 juxtaposed to an octameric TRE-element. Transfections with point mutants showed that these target sequences were necessary for TPA and EGF induction of transcription.

Cultured keratinocyte sheets enhance spontaneous re-epithelialization in a dermal explant model of partial-thickness wound healing

An in vitro model for partial-thickness cutaneous wound healing is described in which the influence of variables present in vivo, such as blood-borne factors and inflammatory cells, is eliminated. Dermal sheets of porcine skin are maintained in culture at the air-liquid interface in serum-free medium, and re-epithelialization from the keratinocytes of the hair infundibula can be studied. Dermal sheets of different thicknesses harvested from various depths were first evaluated for viability and regenerative potential in serum-supplemented medium. Mid-dermal explants, 20/1000 inch thick, showed the greatest epithelial outgrowth from the appendigeal keratinocytes and the longest viability in vitro. Explants of this type were used in all subsequent experiments. The effects of growth factors on re-epithelialization of the explants were studied in a serum-free environment. Epidermal growth factor, cholera toxin, bombesin, and insulin-like growth factor alone and in various combinations were applied to the explant surface in aqueous solutions by micropipette. Outgrowth was assessed by computerized morphometric analysis (RS/1 program by BBN) at days four and eight. Among all factors tested, cholera toxin alone and in combination with insulin-like growth factor produced the greatest epithelial outgrowth. Nevertheless, topical applications of growth factors failed to induce complete re-epithelialization within the experimental time frame. In contrast, explants to which cultured human keratinocyte sheets were topically applied regenerated a confluent and regularly stratified epidermis within 6 d.

Interleukin 6 and expression of its receptor on epidermal keratinocytes

Interleukin 6 (IL 6) was detected in the culture supernatants of human epidermal keratinocytes and its production was enhanced by stimulation with cytokines. Production of IL 6 in keratinocytes was demonstrated directly by immunohistochemical staining of cultured cells with anti-IL 6 antibody. Keratinocyte-growth was increased by stimulation with recombinant IL 6 (as measured by either [3H] thymidine uptake or direct cell count). Moreover, expression of IL 6 receptor was demonstrated on monolayered cells, and the deeper cells of stratified keratinocytes in culture by immunohistochemistry. On the other hand, differentiated cells in the upper layers did not express IL 6 receptor on their surfaces, suggesting that the expression of IL 6 receptors may be confined to the proliferative cells. Thus, IL 6, which is produced by epidermal keratinocytes, may be involved in the regulation of normal keratinocyte growth.

Potential role of the epidermal growth factor receptor in human pancreatic cancer

The epidermal growth factor (EGF) receptor is a transmembrane protein that has tyrosine kinase activity. It is activated by both EGF and transforming growth factor-alpha (TGF-alpha). Human pancreatic cancer cells overexpress the EGF receptor and exhibit a parallel increase in EGF receptor mRNA without a detectable increase in the number of gene copies coding for the receptor. These cells also produce TGF-alpha and are capable of binding exogenous TGF-alpha. They often recycle EGF, but markedly and rapidly degrade TGF-alpha. However, TGF-alpha is 10-100-fold more potent than EGF in enhancing their anchorage-independent growth. Both growth factors induce EGF receptor down-regulation, but EGF is more efficient than TGF-alpha in this regard. The concomitant overexpression of the EGF receptor and production of TGF-alpha, the recycling of EGF, and the attenuated ability of TGF-alpha to down-regulate the EGF receptor may combine to provide a distinct growth advantage to human pancreatic cancer cells.

Localization of elevated transforming growth factor-alpha in psoriatic epidermis

Biopsies of involved and uninvolved skin from five patients with plaque psoriasis and normal skin from four healthy volunteers were investigated for steady-state quantities of TGF-alpha RNA and protein by in situ hybridization and immunohistochemistry. Increased levels of TGF-alpha RNA were found only in the high-level keratinocytes of involved psoriatic skin (p less than 0.001). Elevated levels of TGF-alpha protein were seen in both the high-level and basal layers of involved psoriatic skin compared to uninvolved psoriatic and normal control skin. Elevated TGF-alpha gene expression is thus implicated in the hyperproliferation of keratinocytes and possibly the altered maturation pattern seen in psoriasis.

Transforming growth factor-alpha messenger RNA localization in the developing adult rat and human mammary gland by in situ hybridization

Transforming growth factor-alpha (TGF alpha) has been implicated in the autocrine growth control of a number of different rodent and human tumor cells, including breast cancer cells. Although TGF alpha has been detected in a limited number of normal tissues, its distribution and physiological function in the mammary gland are relatively unknown. TGF alpha mRNA expression was detected by in situ hybridization with a labeled TGF alpha antisense RNA probe and quantitated by application of computer-assisted digital image processing in both the ductal and alveolar epithelial cells in the virgin rat and nulliparous and parous human mammary glands. During pregnancy and lactation, the level of TGF alpha mRNA expression in the ductal and alveolar epithelial cells increased two- to threefold, while a heterogeneous yet strong expression of TGF alpha mRNA could also be detected in approximately 10-15% of the surrounding stromal cells in the pregnant mammary gland.

Development of mammary hyperplasia and neoplasia in MMTV-TGF alpha transgenic mice

To study the role of transforming growth factor alpha (TGF alpha) in normal mammary development and mammary neoplasia in vivo, we have generated transgenic mice in which a human TGF alpha cDNA is expressed under the control of the MMTV enhancer/promoter. Overexpression of TGF alpha in the mammary epithelium, as confirmed by in situ hybridization and immunohistochemistry, is associated with hyperplasia of alveoli and terminal ducts in virgin female and pregnant transgenic mice. A range of morphologic abnormalities including lobular hyperplasia, cystic hyperplasia, adenoma, and adenocarcinoma is seen in mammary tissue of transgenic females. In contrast, no morphologic abnormalities are seen in transgenic males in spite of TGF alpha overexpression in salivary glands and reproductive organs. TGF alpha can therefore act as an oncogene in vivo and appears to predispose mammary epithelium to neoplasia and carcinoma.

Overexpression of TGF alpha in transgenic mice: induction of epithelial hyperplasia, pancreatic metaplasia, and carcinoma of the breast

Metallothionein-directed expression of TGF alpha in transgenic mice induced a spectrum of changes in the growth and differentiation of certain adult tissues. First, TGF alpha promoted a uniform epithelial hyperplasia of several organs without otherwise causing major alterations in tissue architecture. Second, in pancreas it promoted proliferation of both acinar cells and fibroblasts and focally altered acinar cell differentiation. The magnitude of this response was proportional to the level of local, tissue-specific TGF alpha expression and was reproduced when expression of TGF alpha was placed under the control of the elastase promoter, implying an autocrine or paracrine mechanism. Third, TGF alpha was oncogenic in vivo. It caused dramatic hyperplasia and dysplasia of the coagulation gland epithelium, which displayed evidence of carcinoma in situ, and in postlactational mammary gland it induced secretory mammary adenocarcinomas. Thus, TGF alpha displays characteristics of both a potent epithelial cell mitogen and an oncogenic protein in vivo.

Magnesium and phosphate enrichment of culture medium stimulates the proliferation of epidermal cells from newborn and adult mice

The proliferation and differentiation of mouse epidermal cells can be sequentially analyzed by modification of extracellular calcium. Newborn cells cultured in low calcium medium (less than 0.1 mM) proliferate as a monolayer and maintain a typical basal cell phenotype in culture but have a limited proliferative capacity and short lifespan. Elevation of the magnesium content of the culture medium from 1 to 5 mM stimulated the proliferation of newborn mouse (1-3 days old) keratinocytes. Maximal DNA synthesis rates, as determined on day 5 of culture, were up to 2-3-fold higher in the magnesium-enriched cultures. Exposure to high magnesium caused 3-4-fold increases in the DNA content of newborn keratinocyte cultures, and extended the confluent phase of epidermal cell growth to over 10 days. Other divalent cations (strontium, copper, zinc, nickel, beryllium, and barium) did not improve keratinocyte growth in culture. Keratinocytes from the tail skin of adult (3 months old) mice displayed an absolute requirement for high phosphate in the culture medium. The medium containing an optimal (10 mM) phosphate concentration prevented the cell detachment caused by the standard low (1 mM) phosphate medium, and in combination with an elevated magnesium content (10-15 mM) it markedly increased both DNA synthesis rates and DNA content of the adult cell cultures. Optimally growing, newborn or adult cultures contained less cells in the G1 phase of the cell cycle and more cells in S and G2 +M. The addition of phosphate and magnesium per se did not induce keratinocyte differentiation and did not interfere with the high calcium (1 mM)-induced differentiation.

Role of growth factors, cytokines, and their receptors in the pathogenesis of psoriasis

Psoriasis is characterized by epidermal hyperplasia, altered epidermal maturation, and local accumulation of acute and chronic inflammatory cells. Keratinocyte hyperplasia in psoriasis may be explained in part by overproduction of growth factors or cytokines which stimulate epidermal proliferation and by altered metabolism of growth-factor receptors in affected skin. Psoriatic epidermis displays overproduction of TGF-alpha and interleukin-6 (IL-6), factors produced by keratinocytes and other cell types in psoriatic skin. TGF-alpha and IL-6 are mitogens for normal human keratinocytes and act via specific receptors. The TGF-alpha receptor (EGF receptor) is overexpressed in psoriatic epithelium and its altered expression could be caused in part by gamma interferon which prevents normal receptor down-regulation in response to EGF binding. Several phenotypic features of the psoriatic keratinocyte, including growth activation and expression of HLA-DR, gamma-IP-10, ICAM-1, and other molecules, are best explained as resulting from the combined effects of TGF-alpha, IL-6, and gamma interferon (and possibly other cytokines) on epidermal keratinocytes. The multiple histologic features of psoriasis, including epidermal hyperplasia and accumulation of acute and chronic inflammatory cells, may be mediated by defined growth factors and cytokines that are produced in psoriatic skin and affect the function of diverse cell types.

Epidermal and dermal effects of epidermal growth factor during wound repair

Epidermal growth factor (EGF), a well-characterized peptide that stimulates in vitro cell proliferation, has now been shown to enhance in vivo resurfacing of porcine wounds. Topical formulations containing either recombinant EGF or placebo were applied daily to partial-thickness wounds along the dorsal surface of pigs. Following full-thickness removal of these wounds, tissues were sectioned and stained, and histologic sections were subjected to computerized morphometric analysis. A significant acceleration of epithelialization across the wound surface was noted following daily EGF treatments. EGF delivered in a variety of topical formulations also produced a marked increase in the cellularity and thickness in the neodermis. A dose-responsive increase in the thickness of the granulation tissue was also observed. In conclusion, topical application of EGF stimulates epithelialization of partial-thickness wounds and produces a positive impact on the underlying dermis during the early phases of wound repair.

Cytotoxicity testing of wound dressings using normal human keratinocytes in culture

Comparative cytotoxicity testing of 16 wound dressings of different composition show that normal human keratinocytes (NHK) growing on a fibroblastic feeder layer are as sensitive to toxic materials by direct contact as the confluent MRC5 fibroblasts used for standard cell culture cytotoxicity testing, and slightly more sensitive when extracts of the dressings were tested. After direct contact with each of the cell types, we found effects due to 12 dressing samples (75%), but the extracts of only 6 of them induced changes in cell shape or cell death on NHK, and 4 of them on MRC5 cells. In order to assess the compatibility of these dressings with a pure population of epidermal cells, the cell type responsible for reepidermization of healing wounds, we then tested the sensitivity, both to dressing samples and extracts, of normal human keratinocytes (NHK) grown in chemically defined medium and without a feeder layer: The results show epidermal cytocompatibility of 10 dressing extracts, while 6 others induced cytopathic effects. Three of these extracts specifically damaged epidermal cells and inhibited their proliferation. When comparing the sensitivities of NHK (in defined medium) and MRC5 cells, we observed complete correlation for 75% of the dressings by extract testing and in 94% of the cases after direct contact.

Interaction of urokinase A chain with the receptor of human keratinocytes stimulates release of urokinase-like plasminogen activator

On the basis of a fibrinolytic assay with 125I-fibrin, zymography, and immunoprobing with anti-human urokinase antibody, we have observed that the in vitro established NCTC human keratinocyte cell line releases into the culture medium a 54,000-Da plasminogen activator which is indistinguishable from human urokinase. Only the early release following the washing of keratinocyte monolayers is accounted for by secretion of preformed enzyme, while late secretory events require the de novo synthesis of urokinase. The released enzyme can interact by autocriny with its own receptor present on keratinocytes. The addition to the keratinocyte culture medium of the urokinase A chain can stimulate a concentration-dependent urokinase oversecretion, which is not paralleled by oversecretion of plasminogen activator inhibitor-1. Since stimulation of urokinase production can be obtained by an A chain concentration (5 ng/ml) which was previously shown to be efficient in inducing keratinocyte mobilization in an in vitro migration model system, we hypothesize that this mechanism may be important in vivo during the process of wound repair.

Cultured porcine epithelial grafts: an improved method

An improved method of in vitro cultivation of porcine keratinocytes by which keratinocyte sheets suitable for grafting can be generated rapidly is described. Epidermis from split-thickness porcine skin is enzymatically separated from dermis with 0.25% Dispase solution (37 degrees C) within 3 h, and trypsinized to a single cell suspension. Keratinocytes are grown in Dulbecco-Vogt modified Eagle medium supplemented with 20 ng/ml hydrocortisone, 100 micrograms/ml penicillin, 100 micrograms/ml streptomycin, and 20% (cells from six-month-old pigs) or 10% fetal calf serum (cells from two-month-old pigs). Freshly isolated keratinocytes are plated at a density of 1.25 X 10(6) cells/ml since their plating efficiency is about 15 times lower than that of human keratinocytes grown under comparable conditions. Primary keratinocytes plated on plastic grow to confluence faster than those plated on lethally irradiated 3T3-J2 feeder layer cells. Porcine keratinocytes grown on plastic reach senescence in the third passage but, when subsequently cultivated on a lethally irradiated 3T3-J2 feeder layer, can be passaged up to seven times. Nevertheless, plating efficiency of second-passage porcine keratinocytes is only about 5%-7%, whereas that of human newborn foreskin keratinocytes is 20%-30%. Confluent stratified primary cultures grown on plastic, or secondary cultures grown on feeder layers, are used for grafting. The sheets are detached with Dispase solution and stapled to vaseline gauze to facilitate handling. Epidermal regeneration from porcine grafts produced by this method has been demonstrated after transplantation to full-thickness wounds excised to muscle fascia in donor animals.

Epidermal growth factor and transforming growth factor-alpha induce differential processing of the epidermal growth factor receptor

The capacity of epidermal growth factor (EGF) or transforming growth factor-alpha (TGF-alpha) to induce internalization and degradation of the EGF receptor was compared in NIH-3T3 cells expressing the human EGF receptor. This study was initiated following the observation that TGF-alpha was much less efficient relative to EGF in generating a Mr = 125,000 amino-terminally truncated degradation product from the mature EGF receptor (EGF-dependent generation of this degradation product is described in S.J. Decker, J. Biol. Chem., 264:17641-17644). Pulse-chase experiments revealed that EGF generally stimulated EGF receptor degradation to a greater extent than TGF-alpha. Both ligands induced EGF receptor internalization to similar degrees. However, recovery of [125I]-EGF binding following incubation with EGF or TGF-alpha was much faster for TGF-alpha treated cells. Recovery of [125I]-EGF binding after TGF-alpha treatment did not appear to require protein synthesis. Tyrosine phosphorylation of EGF receptor from cells treated with TGF-alpha decreased more rapidly following removal of TGF-alpha compared to cells treated similarly with EGF. These data suggest that EGF routes the EGF receptor directly to a degradative pathway, whereas TGF-alpha allows receptor recycling prior to degradation, and that tyrosine phosphorylation could play a role in this differential receptor processing.

The effect of external stimuli on cultured rat middle ear epithelium. I. Extracellular calcium concentration

The effect of the extracellular calcium concentration on serially cultured rat middle ear epithelium was investigated with phase contrast microscopy, scanning electron microscopy, and transmission electron microscopy, as well as by a method to induce cornified envelope formation with a calcium ionophore. The results show that calcium concentration affects cell morphology and terminal differentiation. Furthermore, a role in the proliferation rate, secretory activity and migration seems likely. Since the extracellular calcium concentration may fluctuate locally during osteoresorption or osteodeposition, both of which occur during otitis media, this concentration might be an important factor in the pathogenesis of both acute and chronic otitis media.

Epidermal growth factor and the onset of epithelial epidermal wound healing

At 10 days in ovo the embryonic chick epidermis acquires the ability to spread as a cohesive epithelial sheet when wounded. A tissue culture system has been constructed that supports epidermal cell outgrowth consistent with epidermal behaviour in vivo and permits experimental manipulation of the isolated tissue with growth factors and other hormones. This culture system consists of embryonic chick epidermis isolated at days 8, 10, and 12 of development, serum-free, chemically-defined culture medium, and the inner surface of the vitelline membrane of the hen's egg as the culture substratum. At 8 days the cellular outgrowth is mesenchymal in the absence of exogenous EGF. The 8 day tissues responds to added EGF by exhibiting precocious epithelial outgrowth. The results suggest that sensitivity to EGF or EGF-like growth factors is part of the mechanism underlying the developmental onset of epidermal wound healing in skin. The epidermal origin of the outgrowth is determined by antibody staining for specific cytokeratins. The epithelial character of the outgrowth is determined by visualizing actin microfilament distribution. The normal epithelial outgrowth shows apical/basal polarization of the sheet except at the edge. From 10 days on, the isolated epidermis exhibits epithelial outgrowth from explants in culture in the absence of exogenous EGF, suggesting endogenous production of an EGF-like factor. Glucocorticoid and mineralocorticoid hormones both produce a reduced amount of epithelial outgrowth. This retardation of the early outgrowth by glucocorticoids and mineralocorticoids could result from a reduced ability of the cut edge of the epidermis to 'disorganize' and assume the unpolarized migratory form required for rapid epidermal wound healing.

Protein factors which regulate cell motility

Cell motility (i.e., movement) is an essential component of normal development, inflammation, tissue repair, angiogenesis, and tumor invasion. Various molecules can affect the motility and positioning of mammalian cells, including peptide growth factors, (e.g., EGF, PDGF, TGF-beta), substrate-adhesion molecules (e.g., fibronectin, laminin), cell adhesion molecules (CAMs), and metalloproteinases. Recent studies have demonstrated a group of motility-stimulating proteins which do not appear to fit into any of the above categories. Examples include: 1) scatter factor (SF), a mesenchymal cell-derived protein which causes contiguous sheets of epithelium to separate into individual cells and stimulates the migration of epithelial as well as vascular endothelial cells; 2) autocrine motility factor (AMF), a tumor cell-derived protein which stimulates migration of the producer cells; and 3) migration-stimulating factor (MSF), a protein produced by fetal and cancer patient fibroblasts which stimulates penetration of three-dimensional collagen gels by non-producing adult fibroblasts. SF, AMF, and MSF are soluble and heat labile proteins with Mr of 77, 55, and 70 kd by SDS-PAGE, respectively, and may be members of a new class of cell-specific regulators of motility. Their physiologic functions have not been established, but available data suggest that they may be involved in fetal development and/or tissue repair.

Multicentre experience in the treatment of burns with autologous and allogenic cultured epithelium, fresh or preserved in a frozen state

This report describes the clinical results obtained from a multicentre experience of the use of autologous and allogenic cultured human epidermal cells in the treatment of partial and full skin thickness burns. A laboratory has been organized to supply cultured epithelium to Burns Units in different cities. From May 1986 to December 1988, 58 patients with an age range of 1 to 59 years, and with burns covering between 7 and 95 per cent of the body surface area, have been treated. Graftable cultured epithelium can be frozen and remain viable if stored in a skin bank. Such grafts were used successfully to treat patients with partial and full skin thickness wounds.

Production of TGF-alpha and TGF-beta by cultured keratinocytes, skin and oral squamous cell carcinomas--potential autocrine regulation of normal and malignant epithelial cell proliferation

Transforming growth factors have a wide range of biological activities related to cell proliferation and differentiation. In general TGF-alpha promotes cell proliferation while TGF-beta may stimulate or inhibit proliferation depending on the cell type and growth factor environment. Cultured human keratinocytes, skin and oral squamous cell carcinomas were analysed for the presence of transcripts and protein for the transforming growth factors alpha & beta. Both growth factors were detected in cultured keratinocytes (which have receptors for and respond to both ligands), and in medium conditioned by these cells. Additionally transcripts for TGF-alpha were found preferentially in the basal, proliferative compartment of cultured keratinocytes. Similarly both growth factors were detected in oral squamous cell carcinomas and a highly significant inverse correlation was found between the levels of TGF-alpha and the epidermal growth factor receptor in these tumours. The data for TGF-alpha are consistent with the existence of an autocrine growth control loop influencing cell proliferation in both a normal cell type and malignant epithelial tissues, a process that in keratinocytes and responsive squamous cell carcinomas could be modulated by TGF-beta.

Rearrangements of desmosomal and cytoskeletal proteins during the transition from epithelial to fibroblastoid organization in cultured rat bladder carcinoma cells

Changes of cell morphology and the state of differentiation are known to play important roles in embryogenesis as well as in carcinogenesis. Examples of particularly profound changes are the conversions of epithelial to mesenchymal cells; i.e., the dissociation of some or all polygonal, polar epithelial cells and their transformation into elongate, fibroblastoid cells of high motility. As an in vitro model system for such changes in cell morphology, we have used cell cultures of the rat bladder carcinoma-derived cell line NBT-II which, on exposure to inducing medium containing a commercial serum substitute (Ultroser G), show an extensive change in their organization (epithelial-mesenchymal transition): the junctions between the epithelial cells are split, the epithelial cell organization is lost, and the resulting individual cells become motile and assume a spindle-like fibroblastoid appearance. Using immunofluorescence microscopy and biochemical protein characterization techniques, we show that this change is accompanied by a redistribution of desmosomal plaque proteins (desmoplakins, desmoglein, plakoglobin) and by a reorganization of the cytokeratin and the actin-fodrin filament systems. Moreover, intermediate-sized filaments of the vimentin type are formed in the fibroblastoid cells. We demonstrate that the modulation of desmosomal proteins, specifically an increase in soluble desmoplakins, is a relatively early event in cell dissociation and in epithelial-mesenchymal transition. In this process, a latent period of 5 h upon addition of inducing medium precedes the removal of these desmosomal components from the plasma membrane. The transition, which is reversible, is dependent on continued protein synthesis and phosphorylation but not on the presence of the inducing medium beyond the initial 2-h period. We discuss the value of this experimental system as a physiologically relevant approach for studying the regulation of the assembly and disassembly of desmosomes and other intercellular adhesion structures, and as a model of the conversion of cells from one state of differentiation into another.

Localization of transforming growth factor alpha and its receptor in gastric mucosal cells. Implications for a regulatory role in acid secretion and mucosal renewal

Transforming growth factor alpha (TGF alpha) shares with epidermal growth factor (EGF) structural homology (35%), a common cell-surface membrane receptor (TGF alpha/EGF receptor), and a nearly identical spectrum of biological activity, including inhibition of gastric acid secretion. Herein, we report expression of TGF alpha mRNA in normal gastric mucosa of the adult guinea pig, rat, and dog. TGF alpha mRNA was also detected in matched surgically resected gastric mucosa and adjacent gastric carcinoma from 10 patients, and in gastric mucosa adjacent to a benign ulcer from an additional patient. TGF alpha protein was quantitated by radioimmunoassay and was present in tumor and adjacent mucosa. TGF alpha/EGF receptor mRNA was also detected in gastric mucosa from all species studied. Localization of TGF alpha and TGF alpha/EGF receptor mRNA expression was examined in samples of unfractionated guinea pig gastric mucosa and from chief cell-enriched and parietal cell-enriched fractions. All samples exhibited TGF alpha and TGF alpha/EGF receptor expression. The TGF alpha signal was greatest in the parietal cell fraction (5.8-fold increase), but was also enhanced in the chief cell fraction (1.9-fold increase) relative to the unfractionated gastric mucosa. Like TGF alpha expression, TGF alpha/EGF receptor mRNA expression was most intense in the parietal cell-enriched fraction (7.8-fold increase), but was also increased in the chief cell-enriched fraction (2.7-fold increase) relative to the unfractionated guinea pig gastric mucosa. We conclude that TGF alpha and TGF alpha/EGF receptor genes are expressed in normal adult mammalian gastric mucosa. These findings, when interpreted in light of described actions of TGF alpha and EGF, provide evidence that local production of TGF alpha could play an important role in the regulation of acid secretion and mucosal renewal in the stomach.

Treatment of skin ulcers with cultured epidermal allografts

Thirty-six skin ulcers in 23 patients were treated with cultured allogeneic epidermal sheets derived from neonatal foreskin. In 73% of ulcers, there was complete healing within 8 weeks, with a mean healing time of 3.3 weeks. In the other 27%, there was reduction in ulcer size of 35% to 93% by 8 weeks after grafting. In 30 painful ulcers, pain was markedly relieved within 24 hours of grafting. The healing pattern suggested that the cultured epidermal sheets acted by stimulation of host keratinocytes to divide and migrate rather than by permanent acceptance of the allograft. Of the 26 ulcers that healed within 8 weeks, 23 (88.5%) remained healed for follow-up periods of 10 to 18 months (mean 13.7 months), with an overall mean duration of healing of 13 months.

Purification of scatter factor, a fibroblast-derived basic protein that modulates epithelial interactions and movement

Scatter factor is a fibroblast-derived protein that causes separation of contiguous epithelial cells and increased local mobility of unanchored cells. Highly purified scatter factor has been obtained by a combination of ion-exchange and reverse-phase chromatography from serum-free medium conditioned by a ras-transformed clone (D4) of mouse NIH 3T3 fibroblasts. Under nonreducing conditions scatter factor has a pI of approximately 9.5 and migrates in SDS/polyacrylamide gels as a single band at approximately 62 kDa from which epithelial scatter activity can be recovered. Treatment with reducing agents destroys biological activity and is associated with the appearance of two major bands at approximately 57 and approximately 30 kDa. Whether both the 57-kDa and 30-kDa polypeptides are required for biological activity remains to be established. All the activities observed in crude medium conditioned by cells producing scatter factor are retained by highly purified preparations of scatter factor. These include (i) increased local movement, modulation of morphology, and inhibition of junction formation by single epithelial cells and (ii) disruption of epithelial interactions and cell scattering from preformed epithelial sheets. These changes occur with picomolar concentrations of purified scatter factor and without an effect on cell growth.

Enhancement of wound healing by topical treatment with epidermal growth factor

Experimental studies in animals have demonstrated that the topical application of epidermal growth factor accelerates the rate of epidermal regeneration of partial-thickness wounds and second-degree burns. We conducted a prospective, randomized, double-blind clinical trial using skin-graft-donor sites to determine whether epidermal growth factor would accelerate the rate of epidermal regeneration in humans. Paired donor sites were created in 12 patients who required skin grafting for either burns or reconstructive surgery. One donor site from each patient was treated topically with silver sulfadiazine cream, and one was treated with silver sulfadiazine cream containing epidermal growth factor (10 micrograms per milliliter). The donor sites were photographed daily, and healing was measured with the use of planimetric analysis. The donor sites treated with silver sulfadiazine containing epidermal growth factor had an accelerated rate of epidermal regeneration in all 12 patients as compared with that in the paired donor sites treated with silver sulfadiazine alone. Treatment with epidermal growth factor significantly decreased the average length of time to 25 percent and 50 percent healing by approximately one day and that to 75 percent and 100 percent healing by approximately 1.5 days (P less than 0.02). Histologic evaluation of punch-biopsy specimens taken from the centers of donor sites three days after the onset of healing supported these results. We conclude that epidermal growth factor accelerates the rate of healing of partial-thickness skin wounds. Further studies are required to determine the clinical importance of this finding.

Transforming growth factor alpha: an aromatic side chain at position 38 is essential for biological activity

Site-directed mutagenesis has been performed in the human transforming growth factor alpha gene. When tyrosine 38 is mutated into phenylalanine or tryptophane, biological activity is retained. In contrast, other alterations between cysteine 34 and cysteine 43 and disruption of disulfide bonds 8 to 21 and 34 to 43 resulted in loss of activities. The presence of an aromatic side chain at position 38 of transforming growth factor alpha seems to be essential for its activity.

Transforming growth factor alpha stimulates prostacyclin production by cultured human vascular endothelial cells more potently than epidermal growth factor

Transforming growth factor alpha (TGF alpha) induces dose- and time-dependent stimulation of prostacyclin (PGI2) production by cultured human umbilical vein endothelial cells. The lowest stimulatory concentration of TGF alpha was 0.1 ng/ml and the maximal response, a 2.7-fold rise, was obtained with 10 ng/ml. The stimulation, which lasted at least 24 h, was blocked by cycloheximide and by indomethacin. TGF alpha induced PGI2 production at 10-100 times lower concentrations than did epidermal growth factor (EGF), although in stimulating endothelial cell growth the two factors were equipotent. This is the first demonstration that TGF alpha enhances PGI2 production by human cells. Moreover, this is the first evidence that it acts as both an agonist (growth) and a superagonist (PGI2 production) of EGF in the same cell type. I suggest that this phenomenon may be involved with the angiogenic activity of TGF alpha.

Transforming growth factor-alpha stimulates proto-oncogene c-jun expression and a mitogenic program in primary cultures of adult rat hepatocytes

Human transforming growth factor-alpha (TGF-alpha, MW 5547) initiates a mitogenic program in "quiescent" 11-to 13-day-old primary cultures of adult rat hepatocytes. Using validated growth reinitiation assays and chemically defined conditions (Koch and Leffert, 1979a) that simulate proto-oncogene expression in regenerating liver (Kruijer et al., 1986), we find that 5.4 nM TGF-alpha stimulates: (i) increases in rates of amiloride-sensitive 22Na+ uptake; (ii) a transient induction in steady-state mRNA levels of proto-oncogene c-jun; (iii) specific increases in hepatocyte nuclear [3H]dT labeling indices, augmented synergistically by insulin and glucagon; and (iv) increases in rates of S-phase entry. Comparative studies indicate that TGF-alpha is a more effective hepatocyte growth promoter than mouse epidermal growth factor. These observations, and published reports linking normal and cancerous liver as biosynthetic sources of TGF-alpha, suggest an autocrine or paracrine role for TGF-alpha in the control of hepatic growth, regeneration, and gene expression.

Regulation of human melanocyte growth, dendricity, and melanization by keratinocyte derived factors

Epidermal pigmentation involves the synthesis of melanin in melanocytes and its transfer to surrounding keratinocytes, where it functions in photoprotection. To investigate the possible role of the keratinocyte in regulating pigmentation, human keratinocytes were incubated for 24 h in a defined culture medium, which was then transferred to pure human melanocyte cultures. After 1 week, the conditioned medium produced a fourfold increase in melanocyte yield and a seven-fold increase in total melanin. Increased melanocyte dendricity was clearly visible within 24 h as well. Ultrafiltration of the keratinocyte-conditioned medium suggested approximately one-half of the growth promoting activity as well as most of the dendricity and melanization stimulating activities were of low molecular weight (less than 500 Da). High molecular weight fractions stimulated only melanocyte growth. Of the several known keratinocyte-derived factors tested, none could be implicated as a mediator of the observed effects. Basic fibroblast growth factor, known to stimulate melanocyte growth in some culture systems, failed to stimulate growth, dendricity, or melanin content when added to the complete non-conditioned medium. Interleukin-1 alpha, interleukin-1 beta, 12-hydroxyeicosatetraenoic acid, prostaglandin E2, leukotriene B4, and adenosine 3',5'-cyclic monophosphate analogues also had no effect. These studies demonstrate that keratinocytes in vitro release factors that modulate melanocyte behavior and expand our understanding of controls for human epidermal pigmentation.