Hoeben E, Swinnen J V, Heyns W, Verhoeven G
Laboratory for Experimental Medicine and Endocrinology, Onderwijs en Navorsing, Gasthuisberg, Catholic University of Leuven, Belgium.
Endocrinology. 1999 May;140(5):2216-23. doi: 10.1210/endo.140.5.6712.
Interactions between (mesenchymal) peritubular myoid cells and (epithelial) Sertoli cells play an important role in the control of Sertoli cell function and spermatogenesis. The factors involved, however, have only partially been identified. Heregulins or neu differentiation factors (NDFs) mediate mesenchymal-epithelial interactions in a variety of tissues, but their role in the testis has not been investigated. Here we demonstrate that recombinant human heregulin-alpha (Her-alpha) and Her-beta stimulate transferrin and androgen-binding protein production by cultured rat Sertoli cells up to 2.5-fold. These effects are more pronounced than those of previously identified growth factors active in this assay, such as insulin-like growth factor I and basic fibroblast growth factor. Combination with these factors results in additive effects and in marked morphological changes in the Sertoli cell cultures, including formation of tubule-like structures. Stimulation of androgen-binding protein secretion is paralleled by increased levels of the corresponding messenger RNA. This parallelism was less consistent for transferrin. Semiquantitative RT-PCR indicates that the expression of NDF-alpha and NDF-beta is more pronounced in peritubular cells than in Leydig or Sertoli cells. Conversely, the main receptors for heregulins/NDFs, HER-3 and HER-4, are predominantly expressed in Sertoli cells. A displacement assay confirms the presence of high-affinity binding sites for [125I]Her-beta on intact Sertoli cells and reveals parallel displacement curves for Her-beta, Her-alpha, and concentrated peritubular cell-conditioned medium (PTCM; estimated ED50 values: 1 ng/ml, 50 ng/ml, and 130 microg protein/ml, respectively), indicating that peritubular cells secrete one or more factors able to compete for heregulin receptors. It is concluded that heregulins/NDFs may play a role in mesenchymal-epithelial interactions in the testis. Estimates of the concentrations of heregulins in PTCM, however, make it unlikely that they contribute significantly to the effects observed with low concentrations of PTCM and ascribed to the putative mediator PModS (peritubular factor that modulates Sertoli cell function). Further investigations will be required to define the exact role of heregulins in the testis.
（间充质）肾小管周肌样细胞与（上皮）支持细胞之间的相互作用在支持细胞功能及精子发生的调控中发挥重要作用。然而，其中涉及的因子仅得到部分鉴定。Heregulins或神经分化因子（NDFs）介导多种组织中的间充质 - 上皮相互作用，但它们在睾丸中的作用尚未得到研究。在此我们证明，重组人heregulin - α（Her - α）和Her - β可使培养的大鼠支持细胞中转铁蛋白和雄激素结合蛋白的产生增加达2.5倍。这些效应比此前在该实验中鉴定出的活性生长因子，如胰岛素样生长因子I和碱性成纤维细胞生长因子更为显著。与这些因子联合使用会产生累加效应，并使支持细胞培养物出现明显的形态学变化，包括形成管状结构。雄激素结合蛋白分泌的增加与相应信使RNA水平的升高相平行。转铁蛋白的这种平行关系不太一致。半定量逆转录 - PCR表明，NDF - α和NDF - β在肾小管周细胞中的表达比在睾丸间质细胞或支持细胞中更明显。相反，heregulins / NDFs的主要受体HER - 3和HER - 4主要在支持细胞中表达。置换实验证实完整支持细胞上存在[125I]Her - β的高亲和力结合位点，并揭示了Her - β、Her - α和浓缩的肾小管周细胞条件培养基（PTCM；估计ED50值分别为：1 ng/ml、50 ng/ml和130 μg蛋白/ml）的平行置换曲线，表明肾小管周细胞分泌一种或多种能够竞争heregulin受体的因子。得出的结论是，heregulins / NDFs可能在睾丸的间充质 - 上皮相互作用中发挥作用。然而，对PTCM中heregulins浓度的估计表明，它们不太可能对低浓度PTCM所观察到的、归因于假定介质PModS（调节支持细胞功能的肾小管周因子）的效应有显著贡献。需要进一步研究来确定heregulins在睾丸中的确切作用。
