Steroidogenic and morphogenic characteristics of human peritubular cells in culture

We have explored the morphogenic and functional characteristics of human peritubular cells originating from seminiferous tubule (ST) fragments isolated from the testes of two prepubertal patients with the androgen insensitivity syndrome. These ST were cultured in Dulbecco's Modified Eagle's Medium-Ham's F-12 supplemented with antibiotics, transferrin, hydrocortisone, vitamin E, and 3% fetal bovine serum. A centrifugal growth of elongated fibroblast-like cells peripheral to the ST explants was observed. Muscle-specific actin and 3 beta-hydroxysteroid dehydrogenase were evident in the peritubular area and in the elongated cells growing from the tubules. Histochemistry was negative in the tubules themselves, revealing the mixed nature of these cultures. The ST fragments were lost after subculturing, leaving a homogeneous monolayer of fibroblast-like cells. The steroidogenic potential of these cells was demonstrated by the secretion of testosterone (T) to the culture medium. T secretion was stimulated by hCG in a time-dependent fashion (patient 1: Day 11, 84% and Day 15, 200%; patient 2: Day 8, 73% and Day 11, 32% over basal). FSH also stimulated T secretion (patient 1: Day 5, 136% and Day 8, 89%; patient 2: Day 8, 117% and Day 11, 129% over basal). Furthermore, T secretion by these cultures was 100% higher than that observed in mesenchymal cells obtained from the testicular intertubular space in the same patient. Spontaneous T secretion and hormone responses declined progressively to cease by 25 days in culture. These results suggested the involvement of Sertoli cell (SC)-secreted factor(s) in the regulation of T secretion by peritubular cells. In order to further explore possible paracrine interactions between peritubular and Sertoli cells, we carried out heterologous cocultures with rat SC. After 72 h a striking redistribution of both cell types was observed with the formation of cord-like structures. Ultrastructural examination of these cords showed the formation of a basement membrane between epithelial (Sertoli) and mesenchymal cells of peritubular origin. No resumption of T secretion was observed, but an increase in androgen-binding protein (ABP) production by rat SC under basal (37%) and FSH-stimulated (52%) conditions was evident. Our results show that in the human peritubular compartment, cells exist that can alternatively express steroidogenic functions, associate with SC in a specific mesenchymal-epithelial interaction, and exert regulatory influences on ABP secretion by SC. In addition they indicate that communicating events in the testis are preserved throughout evolution.