Study On The Functional Heterogenenity Of Adult Mouse Leydig's Cells

The main function of Leydig's cells is secreting testosterone that is an indispensable steroid hormone for both spermatogenesis and sex characteristic in male. The translocation of cholesterol from the out to the inner mitochondrial membrane is a rate-limiting step that requires steroidogenic acute regulator protein (StAR) synthesis de novo in steroidogenesis. Morphological and endocrinological evidences have indicated that population of Leydig's cells are not a homogeneity. Present work focus on whether or not the heterogeneity of Leydig cells has any relation with expression of StAR which is virtually important for understanding testis function.Firstly, a reverse hemolytic plaque assay (RHPA) was used to scale testosterone secretion of Leydig's cells in single cells level. Sequentially, StAR mRNA expression was detected with fluorescent in situ hybridization (FISH) at the same cells. The results show that a kind of Leydig's cells form hemolytic plaques obviously. The plaque area increases in response to LH stimuli in dose-dependent meaner and the signals of StAR mRNA and protein were only shown in Leydig cells with hemolytic plaque and intensity of the signals was in proportion to the plaque area (amount of testosterone); in other kind of Leydig's cells neither hemolytic plaque nor the fluorescent signal could be seen even after stimulation of LH. According to the testosterone secretion correspondent to LH stimuli, Leydig's cells could be divided, at least, into two populations: one can secrete testosterone incrementally after LH stimuli, in which StAR protein synthesis is necessary by the way so-called an acute regulatory pathway; in another testosterone secretion did not occur at all with or without LH stimuli, if any, it was beyond the sensitive of RHPA technically. So we can conclude that Leydig'cells are heterogeneous in testosterone secretion, one of them is regulated by LH through the acute regulation pathway, another may have some function in testis other than testosterone secretion regulated by LH. Unfortunately, LH receptor was not studied in present work. Whether lack of LHreceptor or lack of StAR expression in those cells is still unknown. Nevertheless, this work and further research provide a new way to learn the regulatory mechanism of Leydig's cell, and are very important to understand andrological question and clinical symptom of reproductive biology.