Expression of connexin43 in mouse Leydig, Sertoli, and germinal cells at different stages of postnatal development

Connexin 43 (Cx43) is the most abundant and ubiquitously distributed gap ju nction protein in testicular cells. Lack of Cx43 expression results in male infertility. We investigated whether Cx43 is expressed and regulated in Le ydig, Sertoli and germinal cells at different stages of postnatal developme nt. Cx43 was detected using three different antibodies shown by immunoblott ing to be highly specific. At different postnatal ages Cx43 localization wa s compared in serial or double labeled testicular cryosections with immunoc ytochemical distribution of steroidogenic enzyme, 3 beta hidroxysteroid-deh ydrogenase (3 beta HSD), Mullerian inhibitory hormone (MIH), and germinal n uclear cell antigen (GNCA1), which are specific markers of interstitial Ley dig, Sertoli and germinal cells, respectively. In the interstitium, round c ell clumps (RCC) with lipid droplets positive for 3 beta HSD and Cx:43 were frequently found at intertubular areas at birth and Cx:43 was mainly local ized at cell membrane appositions. From day 3, the number and size of 3 bet a HSD-positive RCC started to decrease, and reached a minimum at 7-14 dpp; Cx43 expressed by them is progressively downregulated. From day 21 an incre ase in the size and number of RCC positive for Cx43 and 3 beta HSD was foun d that continued at 24, 26 and 28 days and reached a maximum at 35 and 60 d pp. Biphasic expression of interstitial Cx43 and 3 beta HSD was also found to be positively and temporally correlated with fluctuations in intratestic ular testosterone content at all ages studied. In the seminiferous cord (SQ , Cx43 was expressed at birth between adjacent Sertoli cells DMI positive) localized at the periphery, as well as in their cytoplasm projections that surround centrally localized gonocytes. From days 3 to 7, Cx43 labeling inc reased in Sertoli cells mainly at their apical border. At day 14, Cx43 dist ribution in Sertoli cells changed from apical to basal in parallel to migra tion of germinal (GNCA1-positive) cells from the periphery to the center of the SC. At all these ages, Cx43 was also localized at cell borders between Sertoli and germinal cells. In conclusion, this study demonstrates that Cx 43 in Leydig cells is regulated during postnatal development in an age and functional dependent manner. In the tubule, it is demonstrated that Cx43 is modulated in Sertoli cells during the neonatal and prepubertal period. We also provide evidence for the first time that Cx43-gap junctions communicat e between Sertoli and germinal cells before and during the first wave of sp ermatogenesis. Anat Rec 264:13-24, 2001. (C) 2001 Wiley-Liss, Inc.