TESTICULAR INSULIN-LIKE GROWTH FACTOR BINDING PROTEINS

由于缺乏对精子发生的了解，对精子发生的理解受到限制 生精小管内的局部控制机制。的目标是 这项提议是为了解决理解上的差距，证明 胰岛素样生长因子-I(IGF-I)和IGF结合蛋白-3(IGFBP-3) 本地生产的精子发生的自分泌/旁分泌调节剂。 IGFBP-3是由大鼠和小鼠产生的主要IGF载体蛋白 支持细胞在培养中。FSH显著降低(IGFBP-3mRNA和蛋白 Sertoli细胞中的浓度，IGFBP-3是一种有效的抑制 胰岛素样生长因子-I对培养的支持细胞的作用。有初步证据表明 来自其他研究人员的说法是IGF-I刺激精原细胞 扩散。根据这些数据，主要假设是IGF-I IGFBP-3刺激精子发生，而IGFBP-3抑制IGF-I的这些作用。 检验这一假设的策略是使用两个模型系统；器官 离体生精管和转基因小鼠的培养 IGF-I和/或IGFBP-3的表达受监管机构的指导 支持细胞特异性雄激素结合蛋白基因的元件。 具体目标1建议研究IGF-I对精子发生的影响。 靶向过表达IGF-I的转基因小鼠及其分离株 将使用正常小鼠的生精小管。扩散将是 通过氚胸苷掺入、溴脱氧尿嘧啶核苷标记进行评估 和睾丸匀浆计数；分化将是 通过分析不同阶段的特定标记物进行评估 精子发生、组织学分期及乳酸和丙二醛测定 芳香酶活性。第二个具体目标是确定IGFBP- 3抑制IGF-I的作用。在具体目标中将使用相同的方法 1除了转基因小鼠将有针对性地过表达 IGFBP-3。最后，过度表达IGF-I和IGFBP-3的小鼠将是 以确定它们的影响是否可以中和。 这些研究应该确定IGFBP-3是否是一种生理性的 睾丸中IGF-I活性的自分泌/旁分泌调节剂。这些 这一结果将有助于理解不明原因的男性不育 并将对IGF及其BP如何产生一般影响 在身体的不同组织中发挥作用。

Understanding of spermatogenesis is limited by lack of knowledge about local control mechanisms within the seminiferous tubule. The objective of this proposal is to address this gap in understanding by demonstrating that insulin-like growth factor-I(IGF-I) and IGF binding protein-3 (IGFBP-3) are locally-produced autocrine/paracrine modulators of spermatogenesis. IGFBP-3 is the predominant IGF carrier protein produced by rat and mouse Sertoli cells in culture. FSH markedly lowers (IGFBP-3 mRNA and protein concentrations in the Sertoli cell and IGFBP-3 is a potent inhibitor of IGF-I actions on the cultured Sertoli cell. There is preliminary evidence from other investigators that IGF-I stimulates spermatogonial cell proliferation. Based on these data, the principal hypothesis is that IGF-I stimulates spermatogenesis and IGFBP-3 inhibits these actions of IGF-I. The strategy to test this hypothesis is to employ two model systems; organ culture of isolated seminiferous tubules and transgenic mice in which the expression IGF-I and/or IGFBP-3 is under the direction of the regulatory elements of the Sertoli cell-specific androgen binding protein gene. Specific aim 1 proposes to examine the effects of IGF-I on spermatogenesis. Transgenic mice with targeted overexpression of IGF-I and isolated seminiferous tubules from normal mice will be used. Proliferation will be assessed by tritiated thymidine incorporation, bromodeoxyuridine labelling and counting of the testicular homogenates; differentiation will be assessed by analysis of specific markers of the different stages of spermatogenesis, histological staging and measurement of lactate and aromatase activity. The second specific aim is to determine whether IGFBP- 3 inhibits IGF-I actions. The same methods will be used as in Specific Aim 1 except that the transgenic mice will have targeted overexpression of IGFBP-3. Finally, the mice overexpressing IGF-I and IGFBP-3 will be crossed to determine if their effects can be neutralized. These studies should establish whether IGFBP-3 is a physiological autocrine/paracrine modulator of IGF-I activity in the testis,. These results will contribute to an understanding of unexplained male infertility and will have general implications pertaining to how the IGFs and their BPs function with in different tissues of the body.