Rodler D, Sinowatz F
Department of Veterinary Sciences, Ludwig-Maximilian University of Munich, Munich, Germany.
Anat Histol Embryol. 2018 Apr;47(2):124-132. doi: 10.1111/ahe.12329. Epub 2017 Dec 4.
Angiogenesis, the formation of new blood vessels from pre-existing vasculature, plays a decisive role for the rapid growth of avian follicles. Compared to mammals, few data on the angiogenesis in the avian ovary are available. However, whereas several pro-angiogenic factors in the avian ovary have been recently studied in detail, little information is available on the localization of anti-angiogenic factors. The aim of this study was to determine the localization and possible function of the anti-angiogenic factor thrombospondin-1 (TSP-1) and its receptor CD36 in the ovary of the ostrich using immunohistochemistry and to correlate the results with ultrastructural data. Whereas the oocytes and granulosa cells of all follicular stages were negative for TSP-1, myofibroblasts of the theca externa and smooth muscle cells of blood vessels showed distinct reactions. A distinctly different staining pattern was observed for CD36. The oocytes were CD36 negative. No immunostaining for CD36 could be observed neither in the granulosa cells nor in the adjacent theca interna of vitellogenic follicles. In the theca externa, blood vessels protruding towards the oocyte showed CD36-positive endothelial cells. In conclusion, a fine balance between angiogenic and anti-angiogenic processes assures that a dense net of blood vessels develops during the rapid growth of a selected follicle. Anti-angiogenic molecules, such as TSP-1 and its receptor CD36 may, after the oocyte has reached its final size, inhibit further angiogenesis and limit the transport of yolk material to the mature oocyte. By this mechanism, the growth of the megalecithal oocyte during folliculogenesis may cease.
血管生成，即从已有的脉管系统形成新的血管，对禽类卵泡的快速生长起着决定性作用。与哺乳动物相比，关于禽类卵巢血管生成的数据较少。然而，尽管最近对禽类卵巢中的几种促血管生成因子进行了详细研究，但关于抗血管生成因子的定位信息却很少。本研究的目的是利用免疫组织化学确定抗血管生成因子血小板反应蛋白-1（TSP-1）及其受体CD36在鸵鸟卵巢中的定位和可能的功能，并将结果与超微结构数据相关联。所有卵泡阶段的卵母细胞和颗粒细胞对TSP-1均呈阴性，而卵泡膜外层的肌成纤维细胞和血管平滑肌细胞显示出明显的反应。CD36的染色模式明显不同。卵母细胞CD36阴性。在卵黄生成卵泡的颗粒细胞和相邻的卵泡膜内层均未观察到CD36免疫染色。在卵泡膜外层，向卵母细胞突出的血管显示CD36阳性内皮细胞。总之，血管生成和抗血管生成过程之间的精细平衡确保了在选定卵泡快速生长期间形成密集的血管网。抗血管生成分子，如TSP-1及其受体CD36，可能在卵母细胞达到最终大小后，抑制进一步的血管生成，并限制卵黄物质向成熟卵母细胞的运输。通过这种机制，卵泡发生过程中巨卵黄卵母细胞的生长可能会停止。
