Fombonne Joanna, Charrier Céline, Goddard Isabelle, Moyse Emmanuel, Krantic Slavica
Institut de Neurobiologie de la Méditerranée, Institut National de la Santé et de la Recherche Médicale Unité 29, Parc Scientifique de Luminy-BP13, F-13273 Marseille, Cedex 09, France.
Endocrinology. 2007 May;148(5):2126-37. doi: 10.1210/en.2006-1218. Epub 2007 Feb 15.
The number of adult Leydig cells is one of the factors controlling testosterone secretion by sexually mature testis, and it depends on the proliferative capacity of prepubertal Leydig cells. We investigated here whether this capacity is controlled by leptin because this hormone regulates proliferation in other cell types and has a crucial role in male fertility. Our data show that prebupertal Leydig cells express the Ob/Rb form of leptin receptor and are thus direct targets of this hormone. The analysis of G1/S-phase cyclins by quantitative (real-time) RT-PCR and Western blot points to the leptin-induced decrease in cyclin A2 and subsequent increase in cyclin D1 expression that precedes a leptin-triggered decrease in the number of prepubertal Leydig cells. Quantitative assessments of DNA synthesis by bromodeoxyuridine incorporation and of cycling cell population by Ki67 immunocytochemistry indicate that leptin decreases the cell number by inhibiting cell division and increases mRNA levels of Leydig cell differentiation markers such as relaxin-like factor. Immunohistochemistry of cyclin D1 and relaxin-like factor pointed to the parallel increase of their expression coinciding with the onset of Leydig cell differentiation. Moreover, leptin-treated Leydig cells display increased expression of another differentiation marker (3beta-hydroxysteroid dehydrogenase) that is abolished by knocking down cyclin D1 with small interference RNA. Altogether, our data show that leptin inhibits division of prepubertal Leydig cells via a cyclin D-independent mechanism and suggest that cyclin D1 might be involved in leptin-induced differentiation of Leydig cells.
成年睾丸间质细胞的数量是控制性成熟睾丸睾酮分泌的因素之一，它取决于青春期前睾丸间质细胞的增殖能力。我们在此研究这种能力是否受瘦素控制，因为这种激素调节其他细胞类型的增殖，并且在男性生育中起关键作用。我们的数据表明，青春期前睾丸间质细胞表达瘦素受体的Ob/Rb形式，因此是这种激素的直接靶标。通过定量（实时）RT-PCR和蛋白质印迹对G1/S期细胞周期蛋白进行分析，结果表明瘦素诱导细胞周期蛋白A2减少，随后细胞周期蛋白D1表达增加，这发生在瘦素引发的青春期前睾丸间质细胞数量减少之前。通过溴脱氧尿苷掺入对DNA合成进行定量评估，以及通过Ki67免疫细胞化学对循环细胞群体进行定量评估，结果表明瘦素通过抑制细胞分裂减少细胞数量，并增加睾丸间质细胞分化标志物如松弛素样因子的mRNA水平。细胞周期蛋白D1和松弛素样因子的免疫组织化学表明，它们的表达平行增加，与睾丸间质细胞分化的开始相一致。此外，用小干扰RNA敲低细胞周期蛋白D1可消除瘦素处理的睾丸间质细胞中另一种分化标志物（3β-羟基类固醇脱氢酶）表达的增加。总之，我们的数据表明瘦素通过一种不依赖细胞周期蛋白D的机制抑制青春期前睾丸间质细胞的分裂，并表明细胞周期蛋白D1可能参与瘦素诱导的睾丸间质细胞分化。
