We have previously reported the establishment of a culture system of hamster auricular sebocytes. Although their morphologic and biochemical properties are very similar to those of human sebocytes, the regulation of lipogenesis is not clear. Therefore, we investigated the effect of epidermal growth factor, all-trans retinoic acid, 1alpha,25-dihydroxyvitamin D3, and androgens such as testosterone and 5alpha-dihydrotestosterone on lipogenesis in cultured hamster sebocytes. Intracellular lipid droplets detected with Oil-Red-O staining were observed in 5 d cultures and increased in a time-dependent manner; 40.7% +/- 1.11% of 2 wk cultured cells tested lipid-positive by flow cytometric analysis. When the hamster sebocytes were cultured in the presence of epidermal growth factor, all-trans retinoic acid, or 1alpha,25-dihydroxyvitamin D3, the intracellular lipid droplets were diminished by all-trans retinoic acid and epidermal growth factor, and slightly by 1alpha,25-dihydroxyvitamin D3. The intracellular lipid droplets consisted mainly of triglycerides (71.8%) and, as minor components, cholesterol (18.0%), wax esters (3.6%), and free fatty acids (6.6%). Epidermal growth factor and all-trans retinoic acid decreased the intracellular accumulation of triglycerides (92.6% and 96.1% inhibition, respectively) and free fatty acids (54.3% and 62.6% inhibition, respectively) in the sebocytes. In addition, 1alpha,25-dihydroxyvitamin D3 decreased the triglyceride level (34.3% inhibition), but augmented the accumulation of wax esters (30% increase). There was no difference in the level of cholesterol as a result of these treatments, however. In contrast, 5alpha-dihydrotestosterone augmented the formation of intracellular lipid droplets along with an increase in the accumulation of triglycerides in hamster sebocytes. Our findings that regulation of lipogenesis by all-trans retinoic acid and androgen in hamster sebocytes is identical to regulation in humans suggest that hamster sebocytes are useful for the elucidation of sebaceous function at the cellular level. Furthermore, this is the first evidence that epidermal growth factor and 1alpha,25-dihydroxyvitamin D3 may act as suppressors in the regulation of lipogenesis in hamster sebocytes in vitro.

Background: The development of sebocytes and lipogenesis are known to be dependent on androgens. However, it is not fully understood whether growth factors are involved in the regulation of cell proliferation and lipid formation in sebaceous glands. Objective: This study was designed to evaluate the effect of growth factors such as epidermal growth factor (EGF), transforming growth factor α (TGF-α), basic fibroblast growth factor (bFGF) and keratinocyte growth factor (KGF) on cell proliferation and lipogenesis in cultured hamster sebocytes. Methods: Cell proliferation and intracellular lipid accumulation in these hamster sebocytes treated with growth factors were examined. Results: EGF, TGF-α and bFGF augmented the proliferation of hamster sebocytes for 8 days in a time- and dose-dependent manner. However, KGF had no effect on their proliferation. Moreover, the accumulation of intracellular lipids consisting mainly of triglycerides was suppressed in EGF-, TGF-α-, bFGF- and KGF-treated hamster sebocytes. Conclusion: EGF, TGF-α and bFGF, but not KGF, have mitogenic activity on hamster sebocytes, and all these growth factors act as antilipogenic factors. Moreover, it is likely that the formation of intracellular lipid droplets is independent of cell proliferation in hamster sebocytes.

Background: A human sebaceous gland culture system is very useful in studying the functions of the sebaceous glands at the cellular level. On the other hand, the success rates for culture systems and the experimental results from these human culture systems exhibit significant fluctuations, depending on the condition of the donor skin. Objective: The purpose of this study was to establish a stable culture system in order to investigate the functions of the sebaceous glands under uniform conditions. Methods: Sebaceous glands from the auricles of 5-week-old hamsters were isolated and seeded onto a 3T3 cell feeder layer. The proliferation, lipid production and response to androgens of these sebaceous-gland-derived cells (SGDC) were then examined. Results: The SGDC showed outgrowth, formed colonies and became confluent in a 35-mm dish culture after 14 days in primary culture. The amount of intracellular lipids significantly increased following the peak of the cell proliferation. The composition of the intracellular lipids from the hamster SGDC was identical to human SGDC, except that the hamster SGDC did not contain any squalene. Testosterone and 5α-dihydrotestosterone markedly stimulated the proliferation of these SGDC in a dose-dependent manner. Conclusion: This tissue culture system will be a useful tool for the study of sebaceous gland function at the cellular level.

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