FOLLICULAR MORPHOGENESIS DURING PERINATAL DEVELOPMENT

调节卵泡形态发生的机制尚不清楚，但颗粒细胞与多能体细胞的分化及其与卵母细胞的相互作用似乎是必不可少的早期步骤。与大鼠和小鼠相比，新生叙利亚仓鼠的卵巢在第一次减数分裂前期含有卵母细胞和未分化的体细胞。因此，我们有一个理想的动物模型来研究第一批卵泡产生的机制。初步研究表明：内源性卵泡刺激素的[1]免疫失活导致原始卵泡形成几乎完全抑制，这可以通过马绒毛膜促性腺激素（eCG）逆转，这是一种卵泡刺激素活性不受高度特异性抗卵泡刺激素血清影响的激素；b[2]卵泡形成的失败与表皮生长因子（EGF）受体基因转录和翻译的明显减少有关，这与我们早期的发现一致，即FSH通过EGF及其受体起作用；新生儿卵巢在体内或体外暴露于eCG时，[3]上调与颗粒细胞和卵泡加速分化相关的EGF、EGF受体和tgf - β受体的表达，[4]增加FSH受体mRNA的表达与FSH功能增加相关。我们假设FSH通过EGF和tgf - β受体与其适当配体的时空相互作用机制，在卵泡形态发生的第一阶段控制多能体细胞向颗粒细胞的分化。这将在体内使用抗卵泡刺激素抗血清进行测试，并在体外使用暴露于卵泡刺激素和/或生长因子的胎儿和产后早期仓鼠卵巢进行测试。测量参数包括卵泡形成的[1]形态计量定量；Western免疫印迹法定量评价颗粒细胞分化过程中EGF、tgf - β配体和受体表达的意义；免疫荧光法检测其细胞特异性细微表达；[3]通过RT-PCR定量测定EGF和tgf - β受体mRNA的变化与促性腺激素调节的分化和[4]测定卵巢类固醇生成活性的相关性，以确定体外激素和/或生长因子操纵后卵泡发育的功能意义。结果将大大有助于我们了解卵泡发生的初始步骤，即原始卵泡的形成机制，这将证明对改善人类不孕症的治疗和管理有价值。

The mechanisms regulating the onset of follicular morphogenesis remain unresolved, but the differentiation of granulosa cells from pluripotential somatic cells and their interaction with oocytes appears to be an essential early step. In contrast to rats and mice, ovaries of newborn Syrian hamsters contain oocytes in the 1st meiotic prophase, and undifferentiated somatic cells. Therefore, we have an ideal animal model for studying the mechanism involved in producing the first cohort of follicles. Preliminary studies have shown that: [1] immunoinactivation of endogenous FSH results in nearly complete inhibition of primordial follicle formation and this can be reversed by equine chorionic gonadotropin (eCG), a hormone with FSH activity unaffected by the highly specific anti-FSH serum; [2] the failure of follicular formation is correlated with an appreciable reduction in the transcription and translation of the epidermal growth factor (EGF) receptor gene consistent with our earlier findings that FSH functions via EGF and its receptor; [3] exposure of neonatal ovaries in vivo or in vitro to eCG upregulates the expression of EGF, EGF-receptor and TGF-beta receptor associated with accelerated granulosa cell and follicle differentiation and [4] increased expression of FSH-receptor mRNA correlates with increased FSH function. We hypothesize that FSH controls the differentiation of pluripotential somatic cells into granulosa cells during the first phases of follicular morphogenesis by mechanisms that involve the spatio-temporal interaction of EGF and TGF-beta receptors with their appropriate ligands. This will be tested in vivo using anti-FSH antiserum and in vitro using fetal and early postnatal hamster ovaries exposed to FSH and/or growth factors. Measured parameters include [1] morphometric quantitation of follicle formation; [2] quantitative evaluation by Western immunoblotting, of the significance of EGF and TGF-beta ligand and receptor expression during granulosa cell differentiation; their cell- specific subtle expression will be identified by immunofluorescence; [3] correlation of changes in EGF and TGF-beta receptor mRNA, determined by RT-PCR quantitation, with gonadotropin-regulated differentiation and [4] measurement of ovarian steroidogenic activity to determine the functional significance of follicular development following in vitro hormone and/or growth factor manipulation. Results will contribute substantially to our understanding of the mechanisms involved in the initial steps of folliculogenesis, i.e., the formation of primordial follicles, which will prove valuable for improving the treatment and management of human infertility.