Growth of human keratinocytes in a defined medium supplemented with growth factor of serum

The impact of skin viability on drug metabolism and permeation—BSA toxicity on primary keratinocytes

For testing cutaneous absorption of drugs, ingredients of cosmetics and also for risk assessment of industrial compounds predictable in vitro test protocols are under investigation using excised skin or reconstructed human epidermis. Since the metabolizing enzymes expressed by viable skin can influence the absorption behaviour of substances by changing their structure and thereby their physicochemical characteristics, the metabolic capacity should be considered in the design of the test protocols of compounds susceptible to metabolism. Then data, generated using viable reconstructed epidermis may reflect the in vivo situation. Interestingly, bovine serum albumin (BSA) commonly used in receptor media in permeation studies to facilitate solubility of highly lipophilic substances strongly inhibited the metabolism of topically applied prednicarbate in reconstructed epidermis. Here, we show that 5% BSA is toxic to reconstructed epidermis and keratinocytes which was consistent with the earlier findings. While media toxicity (deficiency media) was at least partly the cause of both apoptotic and necrotic processes in keratinocytes, BSA only slightly increased the rate of necrotic cells. Moreover, caspase inhibitors did not reduce BSA toxicity. Yet, the results show that BSA toxicity on keratinocytes has to be carefully considered if this protein is used in permeation studies with reconstructed epidermis.

Expression of basement membrane components in skin equivalents--influence of dermal fibroblasts

We have made a skin equivalent constructed of fibroblasts embedded in a type I collagen, with an overlying stratified keratinocyte epithelium to examine formation of the basement membrane. We assessed the influence of the existence and species of fibroblasts in the collagen gel. Cultured human keratinocytes were well attached to the dermal equivalent. Plating efficiency was not clearly different among several types of gel. On the control and mouse fibroblast gel, sheet formation was delayed and epithelial stratification on the human fibroblast gel was more remarkable than on the control gel. On the human fibroblast gel, we observed the expression of basement membrane components (bulbous phemphigoid antigen, laminin, type IV collagen and fibronectin) between the sheet of cultured keratinocytes and the human fibroblast gel earlier than those on the control gel and mouse fibroblast gel. Type VIII collagen was not observed in any of the models at 4 weeks.

Organization and disorganization of actin filaments in human epidermal keratinocytes: heat-shock treatment and recovery process

We investigated alterations of actin organization due to heat shock and recovery from the collapse in human epidermal keratinocytes. Exposure of keratinocytes to elevated temperature caused the rapid disintegration of actin filaments. With a heat-shock treatment at 45 degrees C for 10 min, actin filaments disappeared and granular actin was distributed diffusely in the cytoplasm. After return to 37 degrees C, recovery of actin organization was observed. Completely disintegrated granular actin assembled to form actin dots, which tended to group. The grouping actin dots often took a circular, semicircular or arched form. Filamentous actin then extended out from the actin dots. Fine short bundles of actin filaments had a rippled appearance or were polygonal in structure, with actin filaments converged at many points. On the seventh day after heat-shock treatment, actin organization had almost returned to the pre-heat-shock condition, with diffusely distributed actin filaments. In previous studies, we observed such aberrant structures in human malignant keratinocytes and human epidermal keratinocytes treated with 12-O-tetradecanoylphorbol-13-acetate. The observations presented here indicate that those structures are not specific to malignancy or to the process of malignant transformation, but represent less mature and aberrant organizations of actin.