Growth and differentiation of an established rat keratinocyte line in serial culture

Isolation and propagation of keratinocytes derived from Cashmere goat fetus

The study was conducted to isolate epidermal keratinocytes from Cashmere goat fetus with the aim to develop suitable conditions for keratinocyte cultivation and propagation. The methods developed for keratinocyte culture include (i) use of a feeder-layer of mitotically inactivated fibroblasts obtained from goat and mouse fetal skin, (ii) use of a substrate such as collagen IV, or (iii) without use of any substrate. Epidermal cell removal was established by enzymatically separating keratinocytes from 12 to 16 weeks aged fetal skin tissues treated with 0.125% trypsin solution overnight at 4 degrees C. The cells were maintained in all culture conditions with serum containing medium. Keratinocyte multiplication and proliferation were comparable in different culture conditions and the improved cellular attachment and growth have been obtained in cultures on feeder layers. Colony forming keratinocytes on feeder layer were heterogeneous in their growth potential. In feeder free conditions, high cellular density was required at plating for sub-cultivation as their poor attachment in culture dishes. This study reports the comparative efficacy of different culture conditions for keratinocyte isolation and in vitro propagation originating from Cashmere goat fetus.

Streptococci and Actinomyces induce antibodies which cross react with epithelial antigens in periodontitis

Perturbation of epithelial structure is a prominent but poorly understood feature of the immunopathological response to bacterial antigens which characterizes the destructive lesion of periodontitis. Western analysis of sera from 22 patients with periodontitis detected multiple antigens in extracts of epithelial cells whereas sera from 12 periodontally healthy subjects displayed only trace reaction with epithelial antigens. To investigate a possible relationship between the bacterial flora adjacent to diseased sites and the presence of antibodies reactive with epithelium, subgingival plaque samples were taken from deep periodontal pockets and cultured anaerobically. Gram positive bacteria containing antigens cross-reactive with epithelial cells were reproducibly isolated by probing membrane colony-lifts with affinity-isolated (epithelium-specific) antibodies and identified by 16S rDNA sequence homology as streptococci (S. mitis, S. constellatus and two S. intermedius strains) and Actinomyces (A. georgiae, and A. sp. oral clone). Conversely, when serum from patients with periodontitis was absorbed with the captured bacterial species the number of epithelial antigens recognized was specifically reduced. It was concluded that development of cross-reactive antibodies related to these organisms may contribute to perturbation of the epithelial attachment to the tooth and the progression of periodontitis. These autoreactive antibodies could also be a contributing factor in other diseases affecting epithelia.

Synthesis of proteoglycans in rat mucosal keratinocytes

The synthesis of hyaluronic acid and proteoglycans by rat mucosal keratinocytes of an established cell line (CCL-10) has been investigated. Proliferating cultures at or near confluency were grown in the presence of [35S] sulfate or D-[1-3H] glucosamine for 24 h, and the glycosaminoglycan composition of cells and medium was determined. Characterization of the 35S-labelled glycosaminoglycans showed that heparan sulfate was the major component (approximately 90%) and that small amounts (approximately 10%) of galactosaminoglycans had also been synthesized. Analysis of cultures labelled with D-[1-3H] glucosamine demonstrated that hyaluronic acid was also present, most prominently in the medium where approximately one third of the radioactivity in the glycosaminoglycan pool was found in the hyaluronic acid fraction. [35S]-labelled proteoglycans extracted from the cell layer in the presence of protease inhibitors showed substantial heterogeneity upon chromatography on Sepharose CL-6B. In contrast, the proteoglycans in the medium gave a major peak which was eluted at a Kav of 0.28. Gel chromatography of the glycosaminoglycan chains in the latter, isolated after proteolytic digestion, indicated a molecular weight of 17,000.

Growth requirements and characterization of rat cervical epithelial cells in culture

The extended culture of rat cervical epithelial cells can be achieved in the absence of a fibroblast feeder layer by utilizing collagen gels and a complex growth medium. The medium contains a 1:1 mixture of RPMI-1640 and Ham's F12 supplemented with 7.5% porcine serum and epidermal growth factor, cholera toxin, transferrin, insulin, and hydrocortisone. Under these culture conditions the cells show rapid log-phase growth and high saturation densities while retaining the ultrastructural characteristics of immature squamous metaplastic cells of the rat uterine cervix even after extended passage. In a manner similar to epithelial cells from a variety of sources, rat cervical epithelial cells form hemicysts at confluence in vitro when cultured on impermeable substrates. The development of these methods for culturing cervical epithelial cells provides an experimental system for the study of factors important in regulating the growth and differentiation of metaplastic squamous epithelial cells.

Retinoic acid stimulates degradation of interstitial collagen fibrils by rat mucosal keratinocytes in vitro

A large body of evidence suggests that retinoids modulate the phenotypic expression of epithelial cells of skin and mucous membranes. The purpose of this study was to investigate the effect of retinoic acid on keratinocyte-mediated collagen breakdown. Keratinocytes derived from the ventral surfaces of the tongues of 4-6 week-old male Wistar rats were established in culture under conditions which are restrictive to growth of fibroblasts, and they were eventually cloned by limiting dilution. The cells were seeded (100,000 cells/cm2) in dishes coated with 3H-labeled, reconstituted type I collagen fibrils and incubated in serum-free medium over a 3-5 day period. Dissolution of the collagen fibrils was monitored by the release of radioactivity to the culture medium. Unstimulated cells metabolized the collagen rather slowly, but addition of retinoic acid in concentrations from 10(-6)M to 10(-8)M resulted in marked acceleration of the degradative process, with complete solubilization of the collagen fibrils in four or five days. The effect of 10(-6)M retinoic acid was of the same order of magnitude as that obtained by addition of a proteolytic activating system either in the form of plasmin or of plasminogen, which is converted to catalytic plasmin by endogenous activators. The effects of retinoic acid and plasminogen/plasmin, however, were not additive. Keratinocytes rendered vitamin A-deficient by cultivation in sera from deficient rats were clearly less effective in degrading the collagen substrate than were "sufficient" cells. Addition of retinoic acid (10(-7)M) enhanced collagen breakdown in both sets of cultures and partially restored the collagenolytic activity of the deficient cells.

Rat esophageal and epidermal keratinocytes: intrinsic differences in culture and derivation of continuous lines

Serially cultivated with 3T3 feeder layer support as colonies of stratified squamous epithelium, rat epidermal and esophageal epithelial cells were readily distinguishable by three criteria. First, the epidermal colonies, exhibiting extensive piling up of squames in the centers, were more stratified than esophageal colonies. Second, in sparse culture 70 to 90% of the esophageal cells but as few as 1 to 5% of the epidermal cells were competent in cross-linked envelope formation upon treatment with the ionophore X537A. After reaching confluence, up to 90% of the cells of both types formed envelopes upon ionophore treatment. Third, epidermal cells in suspension culture reached maximal levels of spontaneously cross-linked envelopes in 1 day or less, while esophageal cells required about 4 days in suspension to reach maximal levels. A reproducible finding with both cell types was that initial colony-forming efficiencies of less than 1% increased to about 40% upon serial passage with consequent derivation of continuous lines. Sparse cultures of esophageal cells with high colony-forming ability retained a high degree of envelope competence (70 to 90%), indicating these two properties are not mutually exclusive. The derived lines exhibited reduced dependence upon feeder layer support at clonal density, but in suspension culture the cells did not grow and lost colony-forming ability with a half-time of several hours. We conclude that cells from these keratinized rat epithelia exhibit intrinsic differences in culture and become continuous lines expressing characteristic regulation of envelope competence and loss of germinative capability in suspension.

Production of three plasminogen activators and an inhibitor in keratinocyte cultures

Keratinocyte function in extracellular proteolysis was investigated. Keratinocytes derived from rat tongue ventral epithelium were maintained and serially propagated under conditions which support continuous expansion of epithelial colonies but are restrictive to fibroblast proliferation (30-32 degrees C and pH 6.8-7.0). These cultures, and cultures of an established, terminally differentiating keratinocyte line, also derived from the ventral epithelium of the rat tongue, released substantial plasminogen activator activity as visualized by the fibrin-agar overlay technique. In addition, keratinocytes grown directly on 3H-labeled fibrin lysed this substrate in a plasmin-assisted process. The presence of serum modulated the kinetics of the reaction in a manner which suggests that a constant inhibitor tonus serves to contain the proteolytic reaction in the tissues and to prevent a chain reaction. Electrophoretic resolution of keratinocyte secretory proteins and of cell lysates revealed three distinct activators migrating at molecular weights of 48 000, 66 000 and 95 000. The keratinocytes also manufactured inhibitor(s) of the fibrinolytic reaction mainly directed against the activation step. The inhibitory activity was present in serum-free culture harvest media in quantities sufficient to completely annihilate the endogenous activators.

The growth and differentiation of cultured newborn rat keratinocytes

Keratinocytes were cultured from adult and newborn rat epidermis using the 3T3 feeder cell technique. By modifying culture conditions a long-lived line of newborn rat keratinocytes was developed which showed a plating efficiency of 40% and a doubling time of 16 h. The cells produced stratified colonies with tonofilaments, desmosomes, cell envelopes, and keratohyaline granules. When the cells were grown on a collagen gel they formed a thick stratum corneum and many keratohyaline granules. The fibrous proteins synthesized by the newborn rat cultured keratinocytes were different than those of newborn rat epidermis but similar to those of adult rat cultured keratinocytes. A histidine-rich basic protein was identified by immunologic techniques but it appeared to be more heterogeneous than that of newborn rat epidermis. A cell envelope precursor protein was identified by dansyl cadaverine incorporation studies and was identical to a major envelope precursor of newborn rat epidermis. The growth characteristics, colony morphology, and biochemical markers did not change for up to 40 passages and there was no evidence of malignant transformation. Because of their case of growth and long-term survival these cells are useful for studying a variety of problems related to keratinization.

Multiple collagen gene expression with type III predominance in rat mucosal keratinocytes

Collagen synthesis in serially propagated cultures of rat mucosal keratinocytes (line RTK-I) was investigated. Analysis of biosynthetically labeled cell and media proteins retrieved after limited pepsin digestion revealed seven or eight collagen chains originating from four distinct collagens (types I, III, IV, V). Type III collagen was identified as the predominant species based on its electrophoretic and chromatographic behavior in the reduced and unreduced states, on the peptide pattern generated by limited cleavage with CNBr and with trypsin, and on the immunofluorescent detection of intracellular, collagen type III-reactive material. Evidence for the synthesis of two type IV collagen chains (155 k and 160 k after limited pepsin digestion) was provided by immunofluorescent and electrophoretic studies. Type V collagen was revealed by immunofluorescence, and two, possibly three, component chains were resolved in native type V collagen isolated from the harvest medium. Type I collagen, identified by comigration with authentic carriers, was a constant but quantitatively variable synthetic product. This study provides evidence that keratinocytes produce collagens normally found in mesenchymal matrices (type I and III) in addition to collagens characteristic of basement membranes (type IV) and of pericellular structures (type V). These findings reveal a hitherto unrecognized complexity and heterogeneity of the collagens synthesized by a highly differentiated epithelial cell type.