SummaryIn response to gonadotropins and androgens, testicular cells produce various molecules that control proper proliferation and differentiation of spermatogenic cells through their paracrine and autocrine actions. However, molecules functioning downstream of the hormonal stimulation are poorly understood. Leukaemia inhibitory factor (Lif) is known to maintain the pluripotency of stem cells including embryonic stem cells and primordial germ cells at least in vitro, but its actual roles in vivo remain to be elucidated. To clarify the function of Lif in teleost (medaka) testes, we examined the effects of Lif on spermatogenesis in a newly established cell culture system using a cell line (named Mtp1) derived from medaka testicular somatic cells as feeder cells. We found that addition of baculovirus-produced recombinant medaka Lif to the culture medium or co-culture with Lif-overexpressing Mtp1 cells increased the number of spermatogonia. In situ hybridization and immunohistochemical analyses of the medaka testes showed that mRNAs and proteins of Lif are expressed in spermatogonia and the surrounding Sertoli cells, with higher expression levels in type A (undifferentiated) spermatogonia than in type B (differentiated) spermatogonia. Our findings suggest that Lif regulates spermatogonial cell proliferation in the medaka.

中文翻译：

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白血病抑制因子在硬骨鱼精子发生中的作用

摘要响应促性腺激素和雄激素，睾丸细胞产生各种分子，这些分子通过其旁分泌和自分泌作用控制生精细胞的适当增殖和分化。然而，对激素刺激下游起作用的分子却知之甚少。已知白血病抑制因子 (Lif) 至少可以维持干细胞的多能性，包括胚胎干细胞和原始生殖细胞体外, 但它的实际作用体内仍有待阐明。为了阐明 Lif 在硬骨鱼（青鳉）睾丸中的功能，我们使用源自青鳉睾丸体细胞的细胞系（命名为 Mtp1）作为饲养细胞，在新建立的细胞培养系统中检查了 Lif 对精子发生的影响。我们发现将杆状病毒产生的重组青鳉 Lif 添加到培养基中或与过表达 Lif 的 Mtp1 细胞共培养会增加精原细胞的数量。原位青鳉睾丸的杂交和免疫组织化学分析表明，Lif 的 mRNA 和蛋白质在精原细胞和周围的支持细胞中表达，在 A 型（未分化）精原细胞中的表达水平高于 B 型（已分化）精原细胞。我们的研究结果表明，Lif 调节青鳉中的精原细胞增殖。