REGULATION OF LEYDIG CELL MITOSIS AND DIFFERENTIATION

成年男性产生睾丸素的能力是由 青春期间质细胞数量增加。间质细胞增多 在数量上是通过间质细胞逐渐发生的一系列事件 前体细胞最初增殖，然后降低其有丝分裂的比率 它们开始表达成年莱迪格特有的蛋白质。 细胞，最值得注意的是类固醇生成酶。精制莱迪格的研究 由PI和其他人管理的细胞有定义的离散阶段 在进行性间质细胞分化的连续体中：纺锤体 成形性、高增殖性间质细胞；未成熟间质细胞 细胞，虽然增殖能力较弱，但仍处于细胞周期中， 含有类固醇生成细胞器，合成类固醇，但分泌 5α减少的雄激素，而不是睾酮；成年间质细胞， 它们不会分裂，主要分泌睾丸激素。 促黄体生成素通过促黄体生成素调节间质细胞功能 大量存在于成体阶段的受体。 然而，间质细胞前体细胞的黄体生成素受体的数量可以忽略不计。 对这种荷尔蒙的反应相对较弱。这些考虑因素 这让我们假设间质细胞发育的开始是 受其他因素的调节，如类固醇生成因子-1(SF-1)。左撇子是 据报道，间质细胞数量增加，并已知增加水平 睾丸素的产生。此应用程序侧重于中的两个进程 哪种促黄体生成素不太可能是控制性刺激： 祖细胞向未成熟间质转化过程中的有丝分裂率 细胞；以及雄激素代谢酶5α-的刺激。 还原酶和3α-羟基类固醇脱氢酶，它们降低 祖细胞和未成熟间质细胞分泌睾酮。 穆勒抑制物质(MIS)将被研究，因为 靶向缺失的MIS基因会导致间质细胞增生， 这表明该因子通常是生长抑制因子。在……里面 为特定目标1计划的实验，我们将确定是否 祖细胞间质细胞有丝分裂减少，观察到 在大鼠产后第14天和第21天，由MI引起；确定 睾酮诱导的未成熟间质细胞有丝分裂增加 终末分化所必需的；调查参与 雌激素对间质细胞生长的抑制作用，因为 观察调节芳香酶，催化雌二醇的酶 综合。为特定目标II计划的实验将单独进行 评价睾酮生物合成和雄激素的调节 通过促黄体生成素、睾酮、SF-1和MIS代谢酶活性； 通过辅因子确定这些酶的控制程度 可获得性；并确定类固醇生成酶 活性由新的间质细胞亚型催化。

The capacity for testosterone production in the adult male results from increases in Leydig cell numbers during puberty. Leydig cells increase in number through a gradual sequence of events in which Leydig cell precursors initially proliferate, than lower their rate of mitosis as they begin to express proteins that are characteristic of adult Leydig cells, most notably, steroidogenic enzymes. Studies of purified Leydig cells conducted by the PI and others, have defined discrete stages within the continuum of progressive Leydig cell differentiation: spindle shaped, highly proliferative progenitor Leydig cells; immature Leydig cells, which, though less proliferative, remain in the cell cycle, contain steroidogenic organelles, synthesize steroids, but secrete 5alpha-reduced androgens rather than testosterone; adult Leydig cells, which do not divide and which secrete primarily testosterone. Luteinizing hormone (LH) controls Leydig cell function through LH receptors that are present in abundant numbers that the adult stage. However, Leydig cell progenitors have negligible numbers of LH receptors and are comparatively unresponsive to this hormone. These considerations led us to hypothesize that the beginning of Leydig cell development is regulated by other factors such as steroidogenic factor-1 (SF-1). LH is reported to increase Leydig cell numbers and is known to increase levels of testosterone production. This application focuses on two processes in which LH is unlikely to be the controlling stimulus: the decrease in mitotic rate during the transition from progenitor to immature Leydig cell; and stimulation of the androgen-metabolizing enzymes 5alpha- reductase and 3alpha-hydroxysteroid dehydrogenase, which lower testosterone secretion by progenitor and immature Leydig cells. Mullerian inhibiting substance (MIS) will be investigated because targeted deletion of the MIS gene causes Leydig cell hyperplasia, indicating that this factor is normally a growth inhibitor. In experiments planned for Specific Aim 1, we will determine if the reduction in progenitor Leydig cell mitosis, that is observed between days 14 and 21 postpartum in the rat, caused by MIS; establish whether testosterone-induced increases in mitosis of immature Leydig cells are required for terminal differentiation; investigate the involvement of estrogen in growth inhibition of the Leydig cells, because MIS is observed to regulate aromatase, the enzyme that catalyzes estradiol synthesis. The experiments planned for Specific Aim II will individually evaluate the regulation of testosterone biosynthetic and androgen- metabolizing enzyme activities by LH, testosterone, SF-1, and MIS; determine the extent of control of these enzymes by co-factor availability; and identify instances where steroidogenic enzyme activities are catalyzed by novel Leydig cell isoforms.