Yadav Himanshu, Lal Bechan
Fish Endocrinology Laboratory, Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India.
Fish Endocrinology Laboratory, Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India.
Steroids. 2017 Sep;125:114-123. doi: 10.1016/j.steroids.2017.07.002. Epub 2017 Jul 13.
Considering the absence of information on testicular growth factors in fishes, present study was aimed to elucidate the existence of BMP15, an important member of TGF-β superfamily, in the testis of a seasonally breeding freshwater catfish, Clarias batrachus and its role in regulation of testicular activities. The study demonstrated the expression of BMP15 in the somatic cells (Sertoli and interstitial cells) in fish testis. The expression varied with changing testicular activity; the expression was very high in the quiescent and early recrudescing testis coinciding with the renewal of spermatogonial cells. Expression then declined gradually with progression of spermatogenesis and steroidogenesis. Expression of BMP15 showed positive correlation with seasonally changing testicular 17β-estradiol but negatively with testicular testosterone and 11-ketotestosterone. In vitro treatment of testis with recombinant human BMP15 enhanced the production of estradiol-17β but concurrently suppressed the production of testosterone and 11-ketotestosterone in testis. Though BMP15 did not alter the expression of StAR protein in the testis, it promoted the expression of 3β-hydroxysteroid dehydrogenase and aromatase in fish testis. Thus the present study for the first time demonstrates that fish testis is capable of producing BMP15 and is expressed by the somatic cells unlike mammals wherein it is produced exclusively by germ cells. Study also suggests that BMP15 may modulate the testicular steroidogenesis by altering the expression of steroidogenic enzymes. BMP15 also appears to play crucial role in renewal of spermatogial cells by augmenting the testicular production of 17β-estradiol.
鉴于鱼类睾丸生长因子方面的信息匮乏，本研究旨在阐明转化生长因子-β（TGF-β）超家族的重要成员骨形态发生蛋白15（BMP15）在季节性繁殖的淡水鲶鱼（胡子鲶）睾丸中的存在情况及其在调节睾丸活动中的作用。该研究证实了BMP15在鱼类睾丸的体细胞（支持细胞和间质细胞）中的表达。其表达随睾丸活动的变化而变化；在静止期和早期复壮期的睾丸中表达非常高，这与精原细胞的更新相吻合。随着精子发生和类固醇生成的进展，表达随后逐渐下降。BMP15的表达与季节性变化的睾丸17β-雌二醇呈正相关，但与睾丸睾酮和11-酮睾酮呈负相关。用重组人BMP15对睾丸进行体外处理可增强睾丸中雌二醇-17β的产生，但同时抑制睾丸中睾酮和11-酮睾酮的产生。虽然BMP15没有改变睾丸中类固醇生成急性调节蛋白（StAR）的表达，但它促进了鱼类睾丸中3β-羟基类固醇脱氢酶和芳香化酶的表达。因此，本研究首次证明鱼类睾丸能够产生BMP15，并且由体细胞表达，这与哺乳动物不同，在哺乳动物中BMP15仅由生殖细胞产生。研究还表明，BMP15可能通过改变类固醇生成酶的表达来调节睾丸类固醇生成。BMP15似乎还通过增加睾丸中17β-雌二醇的产生在精原细胞的更新中发挥关键作用。
