ACTIVATION OF SPERMATOGENIC RECOVERY AFTER TOXIC INSULT

男性暴露于某些环境和医疗毒物导致长期无精子症。偶尔精子发生恢复，表明干（A型）精原细胞存活，但其分化是有限的。 经辐照或二溴氯丙烷（DBCP）处理的大鼠睾丸中含有A型精原细胞，这些精原细胞保留一年以上，但不能分化，可能是人类情况的模型。 在大鼠中，睾酮的短暂抑制导致精子发生的进展和生育力的恢复。 提出的假设是，在毒物处理的大鼠，更大的恢复生育能力，可以通过操纵各种类固醇激素和FSH，这是调节精原细胞发育的支持细胞和可能的另一个类固醇受体阳性体细胞的睾丸，以调节特定基因的表达。 最初，辐照将用于所有目标，但其他毒物的主要发现的一般性将使用DBCP诱导的性腺损伤进行检查。为了确定是否可以实现增强和延长的恢复，将在毒物暴露前后用GnRH拮抗剂、睾酮、雌激素或孕激素的不同组合对大鼠进行处理。 毒物剂量的影响，激素的时机，和特定的激素治疗恢复的持续时间将进一步阐明抑制机制，并建议程序恢复精子发生。 为了评价不同类固醇反应细胞（支持细胞、管周细胞、间质细胞、血管细胞）的作用，将使用三种方法。这些是体外培养的组织碎片，分离的小管，和小管组件;在体内消除Leydig细胞;并确定是否水肿（可能来自血管损伤）在毒物处理的睾丸与精原细胞发育的抑制相关。 将采取初步步骤来确定相关基因。 将来自仅受辐照和未受辐照处理的受辐照大鼠的靶细胞的纯化群体的RNA进行消减杂交，以获得差异表达克隆的文库。这项研究应该定义激素或其他因素，可能被用来作为干预，以提高恢复生育能力的男性以下某些类型的毒物暴露，癌症的免疫抑制治疗，衰老，和特发性不孕症，导致生殖细胞发育的障碍。

Exposure of men to certain environmental, and medical toxicants results in prolonged azoospermia. Occasionally spermatogenesis recovers, indicating that stem (type A) spermatogonia survived but their differentiation was limited. Testes of irradiated or dibromocholoropropane (DBCP) treated rats contain A spermatogonia that remain for over one year but fail to differentiate, and may be a model for the human situation. In the rat, transient suppression of testosterone results in progression of spermatogenesis and restoration of fertility. The hypothesis is proposed that, in toxicant-treated rats, greater restoration of fertility can be achieved by manipulating various steroid hormones and FSH, which are regulating spermatogonial development by acting on Sertoli cells and possibly another steroid-receptor positive somatic cell of the testis to modulate the expression of specific genes. Initially, irradiation will be used in all the Aims, but the generality of major findings to other toxicants will be checked using DBCP-induced gonadal damage. To determine whether enhanced and prolonged recovery can be achieved, rats will be treated both before and after toxicant exposure with different combinations of a GnRH antagonist, testosterone, estrogens, or progestins. The effects of toxicant dose, timing of hormones, and specific hormone treatment on the duration of recovery will further elucidate inhibitory mechanisms and suggest procedures for restoration of spermatogenesis. To evaluate the roles of different steroid-responsive cells (Sertoli, peritubular, Leydig, vascular), three approaches will be used. These are in vitro culture of tissue fragments, isolated tubules, and tubule components; in vivo elimination of Leydig cells; and determining whether the edema (likely from vascular damage) in toxicant-treated testes correlates with the inhibition of spermatogonial development. Initial steps will be taken to identify genes involved. RNA from purified populations of the target cell from irradiated-only and hormone-treated irradiated rats will be subjected to subtractive hybridization to obtain libraries of differentially expressed clones. This study should define hormones or other factors that might be used as intervention to enhance recovery of fertility in men following certain types of toxicant exposure, cancer of immunosuppressive therapy, aging, and idiopathic infertility that result in blocks in germ cell development.