Maekawa M, Kamimura K, Nagano T
Department of Anatomy, Chiba University School of Medicine, Japan.
Arch Histol Cytol. 1996 Mar;59(1):1-13. doi: 10.1679/aohc.59.1.
Peritubular myoid cells, surrounding the seminiferous tubules in the testis, have been found in all mammalian species, but their organization in the peritubular interstitial tissue varies by species. In laboratory rodents, including rats, hamsters and mice, only one layer of myoid cells is seen in the testis. The cells in these animals are joined by junctional complexes as are epithelial cells. On the other hand, several cellular layers exist in the lamina propria of the seminiferous tubule in the human and some other animals. Myoid cells contain abundant actin filaments which are distributed in the cells in a species-specific manner. In the rat, the filaments within one myoid cell run both longitudinally and circularly to the long axis of the seminiferous tubule, exhibiting a lattice-work pattern. The arrangement of the actin filaments in the cells changes during postnatal development, and the disruption of spermatogenesis, such as cryptorchidism, seems to affect further the arrangement of the filaments. Other cytoskeletal proteins, including myosin, desmin/vimentin and alpha-actinin, are also found in the cells. Myoid cells have been shown to be contractile, involved in the transport of spermatozoa and testicular fluid in the tubule. Several substances (prostaglandins, oxytocin, TGF beta, NO/cGMP) have been suggested to affect the contraction of the cell, though the mechanisms of the contraction are still unknown. Recent in vitro studies have demonstrated that the cells secrete a number of substances including extracellular matrix components (fibronectin, type I and IV collagens, proteoglycans) and growth factors (PModS, TGF beta, IGF-I, activin-A). Some of these substances are known to affect the Sertoli cell function. Furthermore, it has been reported that myoid cells contain androgen receptors and are involved in retinol processing. Considering all this, it is evident that peritubular myoid cells not only provide structural integrity to the tubule but also take part in the regulation of spermatogenesis and the testicular function. Their precise roles, however, remain to be solved.
睾丸间质细胞围绕着睾丸中的生精小管，在所有哺乳动物物种中均有发现，但其在睾丸间质组织中的组织结构因物种而异。在包括大鼠、仓鼠和小鼠在内的实验啮齿动物中，睾丸中仅可见一层间质细胞。这些动物的细胞通过连接复合体相连，上皮细胞也是如此。另一方面，在人类和其他一些动物的生精小管固有层中存在几层细胞。间质细胞含有丰富的肌动蛋白丝，这些肌动蛋白丝以物种特异性的方式分布在细胞中。在大鼠中，一个间质细胞内的丝沿着生精小管的长轴纵向和环形排列，呈现出晶格状图案。细胞中肌动蛋白丝的排列在出生后发育过程中会发生变化，而生精障碍，如隐睾症，似乎会进一步影响丝的排列。细胞中还发现了其他细胞骨架蛋白，包括肌球蛋白、结蛋白/波形蛋白和α -辅肌动蛋白。间质细胞已被证明具有收缩性，参与精子和睾丸液在小管中的运输。尽管收缩机制尚不清楚，但有几种物质（前列腺素、催产素、转化生长因子β、一氧化氮/环磷酸鸟苷）已被认为会影响细胞的收缩。最近的体外研究表明，这些细胞会分泌多种物质，包括细胞外基质成分（纤连蛋白、I型和IV型胶原蛋白、蛋白聚糖）和生长因子（PModS、转化生长因子β、胰岛素样生长因子I、激活素A）。其中一些物质已知会影响支持细胞的功能。此外，据报道间质细胞含有雄激素受体并参与视黄醇的加工。综上所述，很明显睾丸间质细胞不仅为生精小管提供结构完整性，还参与精子发生和睾丸功能的调节。然而，它们的确切作用仍有待解决。
