ANDROGEN RECEPTOR EXPRESSION IN THE PREPUTIAL GLAND AND ITS SEBOCYTES

As in other sebaceous glands, preputial gland sebocytes are stimulated to proliferate and produce lipid by androgen. As a necessary step in understanding the role of androgen in sebaceous gland growth and development, we have undertaken studies to determine the relationship between androgen receptor gene expression and sebocyte differentiation. Sebocytes throughout the preputial gland, with the exception of some basal sebocytes, stain intensely for androgen receptor. Quantitative assessment of androgen receptor mRNA by RNase protection assay confirms that androgen receptor mRNA abundance is similar in sebaceous and prostate epithelial cells, but is tenfold less in epidermal cells. When sebocytes were separated according to their state of differentiation by gradient density centrifugation, sebocytes in the 1.080 density fraction contrasted with the more buoyant fractions in that they immunostained weakly for androgen receptors. The 1.080 fraction consists of approximately 50% immature (undifferentiated and early differentiated) sebocytes, whereas more mature sebocytes predominate in the other fractions. Androgen receptor mRNA quantity was found by RNase protection assay to be half as great in the 1.080 density fraction as in the fractions in which more mature sebocytes predominate. In primary monolayer culture androgen receptor mRNA content was significantly higher in sebaceous epithelial cells than in epidermal cells and similar to that in the 1.080 fraction of freshly dispersed sebocytes. These results suggest that there is little if any androgen receptor gene expression in undifferentiated preputial sebocytes and that androgen receptor gene expression increases as sebocytes begin to differentiate. Because androgen receptor expression seems to approach its maximum as sebocytes attain mid-differentiation, the stage at which sebocytes switch from a proliferative mode to commence their specialized holocrine function, androgen is postulated to play a direct role in regulating these aspects of sebocyte development.