Loss of connexin 43 in Sertoli cells provokes postnatal spermatogonial arrest,reduced germ cell numbers and impaired spermatogenesis

For the reason that adult Sertoli cell specific connexin 43 knockout (SCCx43KO) mice show arrested spermatogenesis at spermatogonial level or Sertoli cell only tubules and significantly reduced germ cell (GC) numbers, the aims of the present study were (1) to characterize the remaining GC population and (2) to elucidate possible mechanisms of their fading. Apoptosis was analyzed in both, KO and wild type (WT) male littermates during postnatal development and in adulthood using TUNEL. Although GC numbers were significantly reduced in KO at 2 and 8 days postpartum (dpp) when compared to WT, no differences were found concerning apoptotic incidence between genotypes. From 10 dpp, the substantial GC deficiency became more obvious. However, significantly higher apoptotic GC numbers were seen in WT during this period, possibly related to the first wave of spermatogenesis, a known phenomenon in normal pubertal testes associated with increased apoptosis. Characterization of residual spermatogonia in postnatal to adult KO and WT mice was performed by immunohistochemical reaction against VASA (marker of GCs in general), Lin28 and Fox01 (markers for undifferentiated spermatogonia) and Stra8 (marker for differentiating spermatogonia and early spermatocytes). During puberty, the GC component in SCCx43KO mice consisted likely of undifferentiated spermatogonia, few differentiating spermatogonia and very few early spermatocytes, which seemed to be rapidly cleared by apoptosis. In adult KOs, spermatogenesis was arrested at the level of undifferentiated spermatogonia. Overall, our data indicate that Cx43 gap junctions in SCs influence male GC development and differentiation rather than their survival.