Neurotrophin‐3 (NT‐3) acts as an important growth factor to stimulate and control tissue development. The NT‐3 receptor, TRKC, is expressed in rat testis. Its function in regulation of stem Leydig cell development and its underlying mechanism remain unknown. Here, we reported the role of NT‐3 to regulate stem Leydig cell development in vivo and in vitro. Ethane dimethane sulphonate was used to kill all Leydig cells in adult testis, and NT‐3 (10 and 100 ng/testis) was injected intratesticularly from the 14th day after ethane dimethane sulphonate injection for 14 days. NT‐3 significantly reduced serum testosterone levels at doses of 10 and 100 ng/testis without affecting serum luteinizing hormone and follicle‐stimulating hormone levels. NT‐3 increased CYP11A1‐positive Leydig cell number at 100 ng/testis and lowered Leydig cell size and cytoplasmic size at doses of 10 and 100 ng/testis. After adjustment by the Leydig cell number, NT‐3 significantly down‐regulated the expression of Leydig cell genes (Lhcgr, Scarb1, Star, Cyp11a1, Hsd3b1, Cyp17a1, Hsd17b3, Hsd11b1, Insl3, Trkc and Nr5a1) and the proteins. NT‐3 increased the phosphorylation of AKT1 and mTOR, decreased the phosphorylation of 4EBP, thereby increasing ATP5O. In vitro study showed that NT‐3 dose‐dependently stimulated EdU incorporation into stem Leydig cells and inhibited stem Leydig cell differentiation into Leydig cells, thus leading to lower medium testosterone levels and lower expression of Lhcgr, Scarb1, Trkc and Nr5a1 and their protein levels. NT‐3 antagonist Celitinib can antagonize NT‐3 action in vitro. In conclusion, the present study demonstrates that NT‐3 stimulates stem Leydig cell proliferation but blocks the differentiation via TRKC receptor.

中文翻译：

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Neurotrophin-3 在大鼠再生过程中刺激干 Leydig 细胞增殖

Neurotrophin-3 (NT-3) 是刺激和控制组织发育的重要生长因子。NT-3 受体 TRKC 在大鼠睾丸中表达。它在调节干间质细胞发育中的作用及其潜在机制仍然未知。在这里，我们报道了 NT-3 在体内和体外调节干 Leydig 细胞发育的作用。乙烷二甲磺酸用于杀死成人睾丸中的所有 Leydig 细胞，并在乙烷二甲磺酸注射 14 天后的第 14 天开始睾丸内注射 NT-3（10 和 100 ng/睾丸）。NT-3 在 10 和 100 ng/睾丸的剂量下显着降低血清睾酮水平，而不影响血清促黄体激素和促卵泡激素水平。NT-3 在 100 ng/睾丸时增加 CYP11A1 阳性 Leydig 细胞数量，在 10 和 100 ng/睾丸剂量时降低 Leydig 细胞大小和细胞质大小。经间质细胞数量调整后，NT-3显着下调间质细胞基因的表达（Lhcgr、Scarb1、Star、Cyp11a1、Hsd3b1、Cyp17a1、Hsd17b3、Hsd11b1、Insl3、Trkc和Nr5a1）和蛋白质。NT-3增加了AKT1和mTOR的磷酸化，降低了4EBP的磷酸化，从而增加了ATP5O。体外研究表明，NT-3 剂量依赖性地刺激 EdU 掺入干 Leydig 细胞并抑制干 Leydig 细胞分化为 Leydig 细胞，从而导致培养基睾酮水平降低，Lhcgr、Scarb1、Trkc和Nr5a1及其蛋白水平的表达降低. NT-3 拮抗剂赛利替尼可在体外拮抗 NT-3 作用。总之，本研究表明 NT-3 刺激干 Leydig 细胞增殖，但通过 TRKC 受体阻断分化。