Nandedkar Tarala, Dharma Shalmali, Modi Deepak, Dsouza Serena
National Institute for Research in Reproductive Health (ICMR), Parel, Mumbai 400 012, India.
Soc Reprod Fertil Suppl. 2007;63:57-67.
In the mammalian ovary, early follicular development is gonadotropin independent. Interaction between the oocyte and granulosa cells possibly plays an important role in transition of primordial to preantral stage. However, the molecular and cellular control of early follicular development and cell-cell interaction is complex and poorly understood. In the present study, we examined gene expression in primordial, primary and preantral follicle by cDNA arrays using Day 2, Day 4 and Day 6 neonatal mouse ovaries that contain the various developmental stages of these follicles, respectively. The results revealed that 30% of the genes were differentially expressed in Day 4 ovaries containing primary follicles as compared to D2 neonatal ovaries. The data were confirmed by the expression of Growth Differentiation Factor-9 in the oocytes of primary and preantral follicles. Also, Stem Cell Factor was localized in the granulosa cells of primary and preantral follicles. Electron microscopic studies of Day 6 ovaries showed projections from granulosa cells and microvilli from oocytes in the follicle during the transition from the primary to preantral stage. Further, initiation of gap junctions were observed at ultrastructure level and corroborated with the expression of specific gap junction protein, connexin 43 in preantral follicles of the ovaries. These results infer that primordial follicles are quiescent while the major activities of cell-cell communication and the production of local paracrine factors, are initiated in primary and preantral follicles of the mouse ovary. These preliminary observations may contribute to the elucidation of molecular and cellular pathways involved in follicle transition.
在哺乳动物卵巢中，早期卵泡发育不依赖促性腺激素。卵母细胞与颗粒细胞之间的相互作用可能在原始卵泡向窦前卵泡转变过程中发挥重要作用。然而，早期卵泡发育的分子和细胞调控以及细胞间相互作用复杂且了解甚少。在本研究中，我们使用分别含有这些卵泡不同发育阶段的出生后第2天、第4天和第6天的新生小鼠卵巢，通过cDNA阵列检测原始卵泡、初级卵泡和窦前卵泡中的基因表达。结果显示，与出生后第2天的新生小鼠卵巢相比，含有初级卵泡的出生后第4天卵巢中30%的基因表达存在差异。生长分化因子9在初级卵泡和窦前卵泡的卵母细胞中的表达证实了这些数据。此外，干细胞因子定位于初级卵泡和窦前卵泡的颗粒细胞中。对出生后第6天卵巢的电子显微镜研究显示，在从初级卵泡向窦前卵泡转变过程中，卵泡内颗粒细胞有突起，卵母细胞有微绒毛。此外，在超微结构水平观察到缝隙连接的起始，并与卵巢窦前卵泡中特定缝隙连接蛋白连接蛋白43的表达相佐证。这些结果表明，原始卵泡处于静止状态，而细胞间通讯和局部旁分泌因子产生的主要活动在小鼠卵巢的初级卵泡和窦前卵泡中启动。这些初步观察结果可能有助于阐明卵泡转变所涉及的分子和细胞途径。
