Normal Epidermal Keratinocytes Research Articles

Definition by specific antisense oligonucleotides of a role for protein kinase Cα in expression of differentiation markers in normal and neoplastic mouse epidermal keratinocytes

Epidermal keratinocyte differentiation is a tightly regulated, stepwise process that requires protein kinase C (PKC) activation. Studies using cultured mouse keratinocytes induced to differentiate with Ca2+ have indirectly implicated the alpha isoform of PKC in upregulation of "late" (granular cell) epidermal differentiation markers. Activation of this isoform is also implicated in the suppression of "early" differentiation markers keratin (K) 1 and 10 that characterizes the neoplastic phenotype produced by the v-Ha-ras oncogene. We used antisense oligonucleotides (AS) to directly address the role of PKC alpha in regulating expression of these markers in normal and v-Ha-ras-transduced primary keratinocytes and a keratinocyte cell line (SP-1) containing an activating mutation of the c-Ha-ras gene. Transfection of PKC alpha AS reduced the PKC alpha protein level in a dose-dependent manner, with a maximum effect at doses of 100 nM or higher. Immunoblot analysis with antibodies against PKC alpha, PKC delta, PKC epsilon, and PKC eta confirmed that PKC alpha AS selectively reduced the level of PKC alpha but not the other isoforms. In vitro kinase assays also revealed suppression of Ca(2+)-dependent PKC activity, which is the PKC alpha activity in this cell type, after transfection of PKC alpha AS. When PKC alpha AS-treated normal keratinocytes were stimulated to terminally differentiate with Ca2+, induction of the late differentiation markers loricrin, filaggrin, and SPR-1, as well as transglutaminase K mRNA, was suppressed when compared with their induction in scrambled AS-treated controls. In neoplastic v-Ha-ras-transduced keratinocytes and SP-1 cells, transfection of PKC alpha AS, but not the scrambled AS control, selectively downregulated PKC alpha and restored differentiation-specific expression of K1. These findings directly confirm that PKC alpha is an important component of the signaling pathway regulating terminal differentiation of normal keratinocytes and that activation of PKC alpha contributes to the altered differentiation program of neoplastic murine keratinocytes.

Definition by specific antisense oligonucleotides of a role for protein kinase Cα in expression of differentiation markers in normal and neoplastic mouse epidermal keratinocytes

Definition by specific antisense oligonucleotides of a role for protein kinase Cα in expression of differentiation markers in normal and neoplastic mouse epidermal keratinocytes

Definition by specific antisense oligonucleotides of a role for protein kinase Cα in expression of differentiation markers in normal and neoplastic mouse epidermal keratinocytes

Definition by specific antisense oligonucleotides of a role for protein kinase Cα in expression of differentiation markers in normal and neoplastic mouse epidermal keratinocytes

Functional thrombomodulin expression on epithelial skin tumours as a differentiation marker for suprabasal keratinocytes

In normal human skin,, immunoreactive thrombomodulin (TM) is expressed in a strict differentiation related pattern, solely in suprabasal spinous layer keratinocytes. To evaluate the potential application of TM as a differentiation marker for keratinocyte-derived skin tumours, we have studied immunohistopathological, biochemical and functional TM activities in various skin tumours. Immunoreactive, full sized and enzymatically active TM was expressed in keratinocyte-derived skin tumours (squamous cell carcinoma, seborrhoeic keratosis and partly Bowen's disease), as well as normal epidermal keratinocytes and endothelial cells. However, no TM was detected in basal cell carcinomas, senile keratosis or non-squamous epithelial tumours such as malignant melanoma, naevus pigmentosus and Paget's disease. Interestingly, decreased expression was observed in verruca vulgaris. These findings suggested that differentiation-dependent TM expression was restricted to epithelial skin tumours and undetectable on neural crest derived tumours. TM is a differentiation marker for spinous layer keratinocytes and is a useful tool in histopathological study of epithelial tumours.

Autoantibodies to Hair Follicles in Normal Individuals

Indirect evidence suggests that immune mechanisms may be involved in the pathogenesis of some hair disorders, eg, alopecia areata, 1 and in the regulation of normal hair growth. 2 However, no direct evidence of an immune-response selectively directed to hair follicle (HF) antigens, an essential requirement if these hypotheses are correct, has been reported hitherto. In this study, we report the presence of autoantibodies to HFs in normal individuals. Methods. Serum samples from 22 normal individuals (four autologous and 18 allogeneic) were tested by Western immunoblotting for antibodies to anagen HFs from four normal individuals. Anagen hair follicles were plucked from normal scalp, identified on the basis of their prominent outer root sheath and bulb, and collected. Control tissues included scalp epidermis and dermis obtained by surgical procedure and cultured normal epidermal keratinocytes. Proteins were extracted with 6 mol/L of urea and separated by sodium dodecyl sulfate-8% polyacrylamide gel electrophoresis,

Outer root sheath (ORS) cells organize into epidermoid cyst-like spheroids when cultured inside Matrigel: a light-microscopic and immunohistological comparison between human ORS cells and interfollicular keratinocytes

In organotypic cultures, outer root sheath (ORS) cells of the human hair follicle develop into a stratified epithelium largely reminiscent of the epidermis; this apparently reflects their importance during wound healing. In the present study, ORS cells were grown inside a three-dimensional network of extracellular matrix proteins (Matrigel), together with different mesenchymal cells, in an attempt to mimic their follicular environment. Thus, inside Matrigel, ORS cells formed spheroids differentiating toward the center and showing all the markers of epidermal keratinization. Under identical conditions, normal epidermal keratinocytes developed similar spheroids, but of a significantly smaller size. Human dermal fibroblasts and dermal papilla cells, cocultured in the matrix, had a positive influence on both the proliferation and differentiation within both types of spheroids. Epidermal differentiation markers, such as suprabasal keratins, involucrin, filaggrin, gp80 and pemphigoid antigen, were readily expressed in ORS spheroids, whereas hard (hair) keratins were not detectable by immunostaining. Cells positive for an epithelial membrane antigen, strongly expressed in sebaceous glands, were seen in numerous spheroids. In contrast to organotypic "surface" epithelia, the expression and location of different integrin chains was normalized in ORS spheroids, indicating an enhanced mesenchymal influence in this in vitro system.

Vellus Hair Follicle-Derived Keratinocyte Culture: A New Experimental Model in Human Hair Research

Biological and biochemical mechanisms of hair growth are difficult to study in vivo; therefore the development of in vitro models is of great interest. Today, we have of our disposal reliable techniques to cultivate cell populations and entire components of terminal hair follicles; however, in vitro culture models for cells derived from vellus hair follicles have not yet been established. In this study, we present a technique for cultivating vellus hair follicle-derived keratinocytes (VHK) and we present first findings on their characterization. Primary cultures of VHK were obtained as outgrowths of cultured intact vellus hair follicles prepared by microsurgical means after incubation of full-thickness human skin with dispase. (1) VHK cultures reached confluency after 16-20 days and 3-4 subcultures were possible. (2) VHK were characterized as epithelial cells by light and electron microscopy. (3) A multi-layered stratified epithelium with 8-10 cell layers was observed by electron microscopy presenting abundant keratinosomes in individual cells in contrast to outer root sheath keratinocytes. (4) Synthesis studies of two glycoproteins characteristic for undifferentiated (gp 38) and for differentiated (gp 80) keratinocytes revealed higher synthesis levels for gp 80 and lower levels for gp 38 in VHK as compared to normal epidermal keratinocytes in vitro. These findings suggest a distinct morphologic and differentiation pattern of VHK in culture. This experimental model provides a new tool to study mechanisms of hair growth regulation in vellus hair follicles and to compare them to those of terminal hair follicles.

Biosynthesis of 3,4-didehydroretinol from retinol by human skin keratinocytes in culture.

The uptake and metabolism of radiolabelled retinol was studied in cultivated human skin cells. Normal epidermal keratinocytes in primary culture were able to incorporate unbound [11,12-3H]all-trans-retinol from the growth medium and transform it into 3,4-didehydroretinol (dehydroretinol) in a dose- and time-dependent manner. A total of 23% of the radioactive label became cell-associated during a 48-h incubation period when added at 7 nM to differentiated keratinocytes submerged in serum-containing, high-calcium (1.56 mM) culture medium. At that time point, 25-30% of cell-bound radioactive retinol had been converted into dehydroretinol, with no labelled retinal, dehydroretinal, retinoic acid or dehydroretinoic acid being detected in cells or medium. Thus dehydroretinol, which occurs physiologically in mammalian skin tissue in vivo, was identified as the predominant neutral retinol metabolite in cultured keratinocytes using h.p.l.c. and anhydro-derivatization procedures. At least 94% of the product, along with its precursor, was present in the cells in esterified form, with no traces of the compound being secreted into the cell environment. The rate of formation of dehydroretinol from its precursor was significantly lower in keratinocytes grown in serum-free, low-calcium (0.09 mM) culture medium, and in medium pre-incubated with excess unlabelled substrate. Furthermore, the application of 13-cis-retinoic acid (isotretinoin), a therapeutic retinoid drug known to markedly reduce dehydroretinol levels in human skin, blocked the biosynthesis of this metabolite in cultured keratinocytes. The 3,4-dehydrogenation pathway observed in this study could not be shown to operate to any significant extent in cultures of human epidermal melanocytes or dermal fibroblasts, supporting the hypothesis that keratinocytes represent the principal cell type involved in dehydroretinol formation from retinol in human skin.

Protein Kinase C-Dependent Expression of Type I Transglutaminase mRNA in Ganglioside GQ 1b- and Calcium-Stimulated Human Keratinocytes

Ganglioside GQ 1b was found to induce terminal differentiation in normal epidermal keratinocytes (Yada et al. (1991) Biochem. J. 279, 665-670). In GQ 1b-stimulated human keratinocytes, the increase in mRNA expression of Type I TGase preceded the increases in the TGase activity. The enhancement of its mRNA expression was inhibited when protein kinase C (PKC) was suppressed by pretreatment with an inhibitor, H-7, or down-regulation by long-term preincubation with phorbol dibutyrate. These results indicate that PKC is involvedin the activation of TGase probably via gene expression of TGase mRNA in GQ 1b-induced human keratinocyte differentiation. Similar results were also obtained in Ca 2+-induced differentiation.

Interleukin-7 is a growth factor for Sézary lymphoma cells.

Sézary syndrome is a cutaneous T cell lymphoma characterized by infiltration of the skin by CD4+ cells. These cells generally respond poorly to mitogens and T cell activators. We have studied the action of IL1 to IL4, IL6, and IL7 on the proliferation of Sézary cells from 12 patients. With the exception of IL2 and IL7, the cytokines studied had no proliferative effect on these cells. Whereas IL2 had only a low proliferative capacity (two- to threefold increase) on peripheral blood mononuclear cells, recombinant IL7 constantly induced a very significant (3-40-fold increase) proliferative response, and was used successfully to generate cell lines in three out of eight cases. Growth of Sézary cell lines was shown to be strictly dependent on IL7, and after 2-5 wk of culture presented a switch to a homogeneous phenotype CD3+4+8-7- (except for one line that remained CD7+), with a typical morphology of Sézary cells. Their tumoral origin was demonstrated by the expression of the same T cell receptor-beta gene rearrangement as the patients' T cells. Importantly, cultured normal epidermal keratinocyte supernatants could support the growth of our Sézary lines. Furthermore, the proliferative activity contained in these supernatants was completely blocked by a monoclonal anti-IL7 antibody. These results suggest that IL7 may, therefore, represent an important cytokine in the physiopathology of cutaneous T cell lymphoma.

Aberrant in vitro expression of keratin K13 induced by Ca 2+ and vitamin A acid in mouse epidermal cell lines

Normally the expression of the murine type I keratin K13 is restricted to differentiating cells of internal squamous epithelia which line the oral cavity and the upper digestive tract. Recently, however, we were able to show that K13 is aberrantly but constitutively expressed without its normal type II partner K4 also in differentiating parts of 7,12-dimethylbenz(a)anthracene (DMBA/TPA) 12-O-tetradecanoylphorbol-13-acetate-induced squamous cell carcinomas of mouse back skin, whereas its likewise suprabasal expression in papillomas is variable (Nischt et al., Mol. Carcinogenesis 1, 96–108, 1988). In an attempt to reproduce the aberrant expression of K13 in a mouse in vitro system, we have investigated eight established murine epidermal cell lines for their putative ability to express K13. The cell lines differed distinctly in their derivation and comprised cell lines originating from DMBA/TPA induced papillomas (line SP1) or DMBA-treated adult mouse epidermis (line 308) as well as cell lines derived from DMBA or DMBA/TPA-treated primary epidermal keratinocytes (lines PDV and MCA 3D) and cell lines which arose spontaneously by long-term culture of normal epidermal keratinocytes (lines HEL 30 ° HEL 37 °, HELP I and HELP III). We show that, independent of their derivation, all cell lines possess the intrinsic property to aberrantly express K13. Invariably the K13 gene is not expressed when the lines are cultured under low Ca 2+ conditions (0.05 m M) and thus prevented from differentiation. Its expression can, however, be induced either by increasing the extracellular Ca 2+ concentration or by the addition of physiological concentrations of vitamin A acid to low Ca 2+ medium. Whereas in the latter case, K13 expression occurs without concomitant induction of morphological differentiation of the cells, Ca 2+ elevation in the culture medium induces squamous differentiation and K13 expression occurs only in differentiating cells, thus reflecting the situation observed in in vivo tumors. All cell lines exhibit a concentration optimum for the stimulatory agents; however, the degree of maximal K13 expression varies considerably among the individual cell lines and shows a striking correlation with the reported tumorigenicity of the lines after transplantation to animals. In contrast, a tentatively suggested correlation between the activation of the Ha-ras gene and the aberrant expression of K13 (Nischt et al., Mol. Carcinogenesis 1, 96–108, 1988) could not definitely be confirmed since we observed K13 expression also in three cell lines which did not carry a mutation in codon 61 of the Ha-ras gene. Pending a more detailed study on alternative mutations of the members of the ras gene family, this finding may indicate that aberrant K13 expression may also be a consequence of transformation processes which do not involve the activation of the ras gene.

Transforming growth factor‐β1 localization in normal and psoriatic epidermal keratinocytes in situ

Transforming growth factor-beta 1 (TGF beta 1) is a potent inhibitor of epithelial cell proliferation and its effects on growth and differentiation have been extensively characterized in cultured keratinocytes. We used two TGF beta 1-specific polyclonal antibodies (anti-LC and anti-CC) to determine the presence of TGF beta 1 peptide in keratinocytes in sections of normal human skin in situ and in both plaque and nonplaque skin from individuals with psoriasis. In contrast to the differentiation phenotype expressed by keratinocytes in normal epidermis, keratinocytes in the psoriatic plaque exhibit a hyperproliferative/regenerative differentiation phenotype. Anti-TGF beta 1 staining was observed primarily in the epidermis. Anti-LC TGF beta 1 antibody stained nonproliferating, differentiated suprabasal keratinocytes intracellularly in normal skin but did not stain psoriatic plaques from five of seven patients. In contrast, anti-CC TGF beta 1 antibody stained suprabasal keratinocytes extracellularly in psoriatic plaques, but did not stain normal skin. Both anti-LC and anti-CC stained suprabasal keratinocytes intracellularly in nonplaque psoriatic skin. Thus, the conformation or structure of TGF beta 1 and its localization vary in keratinocytes with distinct differentiation phenotypes suggesting that TGF beta 1 is a potential modulator of keratinocyte differentiation in vivo. Selective association of TGF beta 1 with nonproliferating keratinocytes in the suprabasal layers of the epidermis and its exclusion from the proliferating keratinocytes in the basal layer suggest that it may be a physiological regulator of keratinocyte proliferation. In addition, the intracellular localization of TGF beta 1 peptide in both normal and psoriatic keratinocytes suggests that it is constitutively synthesized by epidermal keratinocytes in vivo.

Regulation of growth and differentiation of normal and psoriatic epidermal keratinocytes

Regulation of growth and differentiation of normal and psoriatic epidermal keratinocytes

Identification of Parathyroid Hormone-related Protein in Canine Apocrine Adenocarcinoma of the Anal Sac

The presence of parathyroid hormone-related protein (PTHrP) in the apocrine adenocarcinoma tumor line (CAC-8) derived from a hypercalcemic dog was demonstrated by western and northern blot analyses. Western blots of CAC-8 tumor extracts revealed a major protein with a molecular weight of approximately 18,000 daltons that cross-reacted with antiserum to human PTHrP. Northern blots demonstrated multiple-sized messenger RNA transcripts in CAC-8 that hybridized to a full-length cDNA probe to human PTHrP. Adenocarcinomas derived from apocrine glands of the anal sac also were stained immunohistochemically for antigens that cross-react with antiserum to human PTHrP. The tumor line (CAC-8) maintained in nude mice stained positively for PTHrP in 13 of 24 tumors. Three of ten apocrine adenocarcinomas from dogs with hypercalcemia stained for PTHrP, whereas zero of ten tumors were positive from normocalcemic dogs. Normal canine epidermal keratinocytes and areas of squamous metaplasia in a perianal gland carcinoma also were positive for PTHrP. These data demonstrated that canine tissues contained a homologue to human PTHrP that likely is important in the pathogenesis of humoral hypercalcemia of malignancy.

Altered levels of endogenous retrovirus‐like sequence (VL30) RNA during mouse epidermal cell carcinogenesis

Gene expression during mouse keratinocyte carcinogenesis was examined in a clonal cell model. Tumor cells from three separate initiated cell lineages were compared with their nontumorigenic precursors and with the progenitor cell strain prior to treatment with 7,12-dimethylbenz[a]anthracene (DMBA). The steady-state levels of VL30 RNA in normal and papilloma cells were regulated by extracellular Ca2+ (which controls proliferation and differentiation in normal epidermal keratinocytes) and culture density. In contrast, steady-state levels of VL30 RNA were not regulated by these factors in the squamous cell carcinoma or the anaplastic carcinoma cells. VL30 expression was Ca2+ dependent in the initiated cell precursors within each tumor cell lineage, suggesting that the loss of response to extracellular Ca2+ was associated with the malignant conversion stage of carcinogenesis. No differences between normal and tumor cells were found in the cellular RNA levels of five additional proto-oncogenes. The mouse epidermal cell model should provide a means for direct assessment of a potential functional role of VL30 sequences in cancer development.

Resistance to 1,25-dihydroxyvitamin D3 of cultured psoriatic epidermal keratinocytes isolated from involved and uninvolved skin.

1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3], a hormonally active form of vitamin D3, has been reported to stimulate epidermal differentiation and to be an effective treatment of psoriatic lesions. We studied the responsiveness of psoriatic epidermal keratinocytes to 1,25-(OH)2D3 in explant-outgrowth cultures of involved and uninvolved skin from six patients with psoriasis. A feeder layer was required for outgrowth of psoriatic epidermal keratinocytes of involved skin, but not for that of cells of uninvolved skin. The growth of normal epidermal keratinocytes was inhibited by 1,25-(OH)2D3, and the number of DNA-synthesizing cells, determined in autoradiographs, was reduced to about 15% of that in control cultures by 1 nmol/L 1,25-(OH)2D3 (0.4 ng/mL). Epidermal keratinocytes isolated from both involved and uninvolved skin of patients with psoriasis were resistant, and 100-fold more 1,25-(OH)2D3 was required to inhibit their DNA synthesis. These results afford new insight into the etiology and therapy of psoriasis.

The effect of trifluoperazine, a calmodulin antagonist, on the growth of normal and malignant epidermal keratinocytes in culture

Calmodulin, a cytoplasmic calcium binding protein, is present in concentrations two- to four-fold higher in malignant cells compared to normal cells. In an effort to learn the significance of these elevated levels, we examined the effect of calmodulin blockage on the growth of normal and malignant keratinocytes in vitro. The level of calmodulin in SCC 12.B 2, a line of keratinocytes derived from an epidermal squamous cell carcinoma (SCC), was about 3.5 times greater than in normal, human newborn foreskin keratinocytes. When exposed to trifluoperazine (TFP), an inhibitor of calmodulin, cell growth was reduced primarily in the cultures of normal keratinocytes. This growth inhibition resulted from two changes in the replicating population of cells, namely an increase in cell cycle length and an increase in rate of cell cycle withdrawal. Cell cycle withdrawal is the irreversible arrest of the cell cycle and is an early event in keratinocyte terminal differentiation. There was no measurable effect on the cell cycle time or withdrawal rate in SCC 12.B 2. The increased resistance to growth arrest in SCC cells may be a consequence of the elevated level of calmodulin in these cells.

Identification of Differentiation‐Specific Antigens in Psoriatic Versus Normal Skin Using Monoclonal Antibodies

Human cell hybrids derived from fusions between carcinoma (HeLa) and normal epidermal keratinocytes can be used as immunogens to generate monoclonal antibodies against keratinocyte differentiation-specific antigens. We examined the immunofluorescent staining patterns of these monoclonals in normal human and psoriatic (lesional and uninvolved) skin tissue sections. The immunofluorescent staining patterns indicate that the monoclonal antibodies are recognizing a number of different keratinocyte antigens. Three monoclonals (HLK7, HLK3, and HLK20) displayed different immunofluorescent reactivity in these tissues. These new monoclonal antibodies will be useful tools to study the differentiation abnormalities in psoriasis and may serve as a marker of the psoriatic diathesis.

Thrombospondin-induced adhesion of human keratinocytes.

Human epidermal keratinocytes obtained from normal skin attached and spread on thrombospondin (TSP)-coated plastic dishes but failed to attach and spread on untreated plastic culture dishes or dishes coated with fibronectin or laminin. These cells produced minimal amounts of immunoreactive TSP. Keratinocytes established in culture on MCDB 153 medium and maintained for one to three passages in an undifferentiated state by continued cultivation in this low Ca2+-containing medium attached and spread on plastic dishes as well as on TSP-coated dishes. These cells also secreted significant amounts of TSP into the culture medium. When the keratinocytes were incubated for one day in MCDB 153 medium supplemented with high Ca2+ or in MEM (which also contains high Ca2+), there was decreased secretion of TSP into the culture medium concomitant with a reduction in attachment and spreading on plastic culture dishes. Proteolytic fragments of TSP were examined for stimulation of keratinocyte attachment and spreading. A 140-kd fragment produced by removal of the 25-kd heparin-binding domain had similar activity to the intact molecule while the 25-kd fragment was without effect. Further proteolytic treatment of the 140-kd fragment gave rise to a fragment consisting of 120 kd and 18-D moieties held together in disulphide linkage. This fragment did not support attachment or spreading. This study reveals that normal epidermal keratinocytes grown under conditions that maintain the undifferentiated state are able to produce TSP and utilize it as an attachment factor. When keratinocytes are grown under conditions that promote differentiation, ability to produce and utilize TSP is diminished. Since TSP is present at the dermal-epidermal junction and because TSP promotes keratinocyte attachment and spreading, this molecule may play an important role in maintaining normal growth of the basal cell layer and may also participate in reepithelialization during wound repair.

Adenylate cyclase system of human trichilemmoma cell line

The adenylate cyclase system of an established human trichilemmoma cell line was investigated. Stimulators of human epidermal adenylate cyclase system, epinephrine, histamine, adenosine, and prostaglandin E increased cyclic AMP levels of the trichilemmoma cells. The effects of epinephrine, histamine, and adenosine were inhibited by the addition of propranolol (a beta-adrenergic antagonist), cimetidine (histamine H2-antagonist), and theophylline (adenosine-receptor antagonist), respectively. The epinephrine, histamine, and prostaglandin E effects were augmented by the addition of cyclic AMP (cAMP) phosphodiesterase inhibitor, isobutylmethylxanthine (IBMX); the adenosine effect was augmented by another phosphodiesterase inhibitor, papaverine. Without the addition of these phosphodiesterase inhibitors, the maximal accumulations were observed at 3 min incubation. Following this, the cAMP content returned to the basal level, and the cells did not respond to repeated stimulations with the same initial stimulator. This fact indicates receptor-specific refractoriness. For example, epinephrine-pretreated cells did not respond to epinephrine, but retained their sensitivity to histamine. It has been known that normal epidermal keratinocytes are regulated in vitro by glucocorticoids, colchicine, and retinoids, resulting in the augmentation of their beta-adrenergic response. Only hydrocortisone treatment on the trichilemmoma cells resulted in the augmentation of the beta-adrenergic response. Although the established human trichilemmoma cell line has similar adenylate cyclase systems as normal epidermis, it apparently has lost some of the regulatory mechanism of the beta-adrenergic response.