The molecular mechanisms regulating undifferentiated spermatogonial cell proliferation and differentiation are still not fully understood. Irisin is an exercise-induced hormone, which is a cleaved and secreted fragment of the fibronectin type III repeat containing 5 (FNDC5) transmembrane protein. Recent studies have demonstrated the role of irisin in cell proliferation and differentiation in various tissues. However, testicular irisin expression and its potential action have not been analyzed. Here, we demonstrate expression of irisin in undifferentiated spermatogonia of primates and in the tree shrew, a bridging species between primates and insectivores. Rhesus monkeys are seasonal breeders with annual phases of high and low testicular activity and germ cell proliferation. Interestingly, expression of both FNDC5 mRNA and irisin is altered between breeding (high spermatogenesis) and nonbreeding seasons (low spermatogenesis). Organotypic testis culture in the presence of irisin increased the expression levels of the Sertoli cell (GDNF) and spermatogonial transcripts Kruppel-like factor 4 (KLF4), Inhibitor of differentiation 4 (ID4), Cluster of differentiation 117 (cKIT), and SALL4, compared to untreated controls, while irisin suppressed its own FNDC5 mRNA. Our data suggest that irisin is a novel endocrine factor involved in the regulation of spermatogonial activities in the testes of primates.

中文翻译：

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Irisin由未分化的精原细胞表达，并调节器官型灵长类动物睾丸培养物中的基因表达。

调节未分化的精原细胞增殖和分化的分子机制仍不完全清楚。Irisin是一种运动诱导的激素，是含有5（FNDC5）跨膜蛋白的III型纤连蛋白重复序列​​的裂解和分泌片段。最近的研究证明了虹膜素在各种组织中的细胞增殖和分化中的作用。但是，尚未分析睾丸虹膜素的表达及其潜在作用。在这里，我们证明了虹膜素在灵长类动物未分化的精原细胞和树sh（灵长类动物和食虫动物之间的桥梁物种）中的表达。恒河猴是季节性繁殖者，每年的睾丸活动度高和低，生殖细胞增殖。有趣的是，在繁殖（高精子发生）和非繁殖季节（低精子发生）之间，FNDC5 mRNA和虹膜素的表达都会改变。虹膜素存在下的器官型睾丸培养可增加支持细胞（GDNF）和精原转录本Kruppel样因子4（KLF4），分化抑制剂4（ID4），分化簇117（cKIT）和SALL4的表达水平，与未经处理的对照组相比，虹膜素抑制了自己的FNDC5 mRNA。我们的数据表明，虹膜素是一种新的内分泌因子，参与了灵长类动物睾丸精原活动的调节。虹膜素存在下的器官型睾丸培养可增加支持细胞（GDNF）和精原转录本Kruppel样因子4（KLF4），分化抑制剂4（ID4），分化簇117（cKIT）和SALL4的表达水平，与未经处理的对照组相比，虹膜素抑制了自己的FNDC5 mRNA。我们的数据表明，虹膜素是一种新的内分泌因子，参与了灵长类动物睾丸精原活动的调节。虹膜素存在下的器官型睾丸培养可增加支持细胞（GDNF）和精原转录本Kruppel样因子4（KLF4），分化抑制剂4（ID4），分化簇117（cKIT）和SALL4的表达水平，与未经处理的对照组相比，虹膜素抑制了自己的FNDC5 mRNA。我们的数据表明，虹膜素是一种新的内分泌因子，参与了灵长类动物睾丸精原活动的调节。