Paracrine interaction in testicular somatic cells

Area of Science:

• Reproductive biology
• Cell biology
• Endocrinology

Background:

• Spermatogenesis initiation relies on signals from Sertoli and Leydig cells, targets of gonadotropins.
• Testes contain other cell types like peritubular cells, macrophages, and vascular components with partially understood paracrine functions.
• Peritubular and Sertoli cells form the germinal epithelium scaffold, maintaining intratubular pressure, sperm transport, and the blood-testis barrier.

Purpose of the Study:

• To investigate the ultrastructure and distribution of steroid hormone receptors, cytoskeletal, and extracellular matrix proteins in rat peritubular and Sertoli cells.
• To correlate morphological observations with in vitro gene expression of hormones and structural proteins during postnatal development.

Main Methods:

• Ex vivo and in vitro studies on rat testes across different postnatal developmental stages.
• Analysis of ultrastructure, steroid hormone receptor distribution, and protein expression.
• RT-PCR for gene expression analysis in cultured peritubular and Sertoli cells (alone and co-cultured).

Main Results:

• Peritubular cells consistently expressed fibronectin, entactin, laminin, and glucocorticoid, androgen, estrogen, and progesterone receptors during development.
• Sertoli cells lacked glucocorticoid receptor and entactin; glucocorticoid receptor was found in germ and peritubular cells, with Leydig cells showing peak expression in week 3.
• Androgen receptor was present in gonocytes, peritubular, and interstitial cells; estrogen receptor was absent in adult peritubular cells; progesterone receptor was in peritubular and Leydig cells.

Conclusions:

• Peritubular cells likely provide an androgen-dependent growth stimulus to seminiferous cords, possibly via Sertoli cells, supporting tubule development postnatally.
• In vitro studies confirmed androgen and glucocorticoid receptor expression in both cell types, with fibronectin secretion by peritubular cells.
• Co-culture of Sertoli and peritubular cells down-regulated fibronectin biosynthesis, highlighting the essential paracrine interplay for seminiferous tubule differentiation.