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 new- born 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 pas- sages and there was no evidence of malignant transformation. Because of their ease of growth and long-term survival these cells are useful for studying a variety of problems related to keratinization

Effect of Minoxidil on Cultured Keratinocytes

Minoxidil has been shown to stimulate hair growth and these studies were undertaken to determine whether the drug had a direct effect on keratinocytes. Cultures of human epidermal cells were treated with minoxidil and it was found that they survived longer than control cultures. In addition, minoxidil prolonged the time that cells could be passed after reaching confluence. The results suggest that minoxidil slows the senescence of keratinocytes, which is similar to what has been found with epidermal growth factor

Modification of Polypeptide Composition in Keratinocyte Fibrous Protein

The thick paw epidermis of the rat and the guinea pig showed a relatively increased amount of the heaviest fibrous polypeptide compared to the thinner epidermis of back and ear. The hyperplastic epidermis of mouse and rat induced by abrasion or painting with 12-0-tetradecanoyl-phorbal-13-acetate (TPA) also revealed an increase in the heaviest polypeptide. The fibrous polypeptides of epidermis from scarred skin lacked components present in normal epidermis. Cultured epidermal cells showed a different fibrous polypeptide composition than the parent tissue which was altered when the cells were transplanted to an animal or grown on a dermal substrate in culture. Thus multiple factors such as hyperplasia, the dermis and cellular environment may modify the polypeptides synthesized by the keratinocyte

The Occurrence of Profilaggrin and Its Processing in Cultured Keratinocytes

An affinity-purified antibody to rat filaggrin detects filaggrin and profilaggrin in extracts of newborn rat epidermis, and a monoclonal antibody to human filaggrin, HF-1, detects the two proteins in extracts of human epidermis. Immunohistologic studies show that HF-1 reacts with keratohyaline granules of human epidermis and those seen in cultured human keratinocytes. Immunoblotting studies have demonstrated that profilaggrin is synthesized in both cultured human keratinocytes and in a long-lived line of cultured rat keratinocytes, but only in the latter is the protein processed to a product of the molecular weight of filaggrin