Schulz Rüdiger W, Menting Sandra, Bogerd Jan, França Luiz R, Vilela Daniel A R, Godinho Hugo P
Department of Endocrinology, Faculty of Biology, University of Utrecht, 3584 CH Utrecht, The Netherlands.
Biol Reprod. 2005 Nov;73(5):891-8. doi: 10.1095/biolreprod.105.039891. Epub 2005 Jul 6.
Germ cell survival and development critically depend on the cells' contact with Sertoli cells in the vertebrate testis. Fish and amphibians are different from mammals in that they show a cystic type of spermatogenesis in which a single germ cell clone is enclosed by and accompanied through the different stages of spermatogenesis by an accompanying group of Sertoli cells. We show that in maturing and adult testes from African catfish and Nile tilapia, Sertoli cell proliferation occurs primarily during spermatogonial proliferation, allowing the cyst-forming Sertoli cells to provide the increasing space required by the growing germ cell clone. In this regard, coincident with a dramatic increase in cyst volume and number of germ cells per cyst, in Nile tilapia, the number of Sertoli cells per cyst was strikingly increased from primary spermatogonia to spermatocyte cysts. In both African catfish and Nile tilapia, Sertoli cell proliferation is strongly reduced when germ cells have proceeded into meiosis, and stops in postmeiotic cysts. We conclude that Sertoli cell proliferation is the primary factor responsible for the increase in testis size and sperm production observed in teleost fish. In mammals, Sertoli cell proliferation in the adult testis is not observed under natural conditions. However, on the level of the individual spermatogenic cyst--similar to mammals--Sertoli cell proliferation ceases when germ cells have entered meiosis and when tight junctions are established between Sertoli cells. This suggests that fish are valid vertebrate models for studying Sertoli cell physiology.
生殖细胞的存活和发育严重依赖于其与脊椎动物睾丸中支持细胞的接触。鱼类和两栖动物与哺乳动物不同，它们表现出一种囊状精子发生类型，其中单个生殖细胞克隆被一群伴随的支持细胞包围，并在精子发生的不同阶段伴随着支持细胞。我们发现，在非洲鲶鱼和尼罗罗非鱼成熟及成年睾丸中，支持细胞增殖主要发生在精原细胞增殖期间，使形成囊状的支持细胞能够为不断生长的生殖细胞克隆提供所需的增加空间。在这方面，尼罗罗非鱼中，随着囊体积和每个囊生殖细胞数量的急剧增加，每个囊支持细胞的数量从初级精原细胞到精母细胞囊显著增加。在非洲鲶鱼和尼罗罗非鱼中，当生殖细胞进入减数分裂时，支持细胞增殖强烈减少，并在减数分裂后囊肿中停止。我们得出结论，支持细胞增殖是硬骨鱼睾丸大小增加和精子产生增加的主要因素。在哺乳动物中，成年睾丸在自然条件下未观察到支持细胞增殖。然而，在单个生精囊肿水平上——与哺乳动物类似——当生殖细胞进入减数分裂且支持细胞之间建立紧密连接时，支持细胞增殖停止。这表明鱼类是研究支持细胞生理学的有效脊椎动物模型。
