Spermatogonial stem cells alone are not sufficient to re‐initiate spermatogenesis in the rat testis following adjudin‐induced infertility

Summary The blood–testis barrier (BTB) is a unique ultrastructure in the testis, which creates a specialized microenvironment in the seminiferous epithelium known as the apical (or adluminal) compartment for post‐meiotic germ‐cell development and for maintenance of an immunological barrier. In this study, we have demonstrated unequivocally that a functional and intact BTB is crucial for the initiation of spermatogenesis, in particular, the differentiation of spermatogonial stem cells (SSCs). It was shown that adult rats (∼300 g body weight, b.w.) treated with adjudin at 50 (low‐dose) or 250 (high‐dose) mg/kg b.w. by gavage led to germ‐cell depletion from the seminiferous tubules and that >98% of the tubules were devoid of germ cells by ∼2 week and rats became infertile in both groups after the sperm reserve in the epididymis was exhausted. While the population of SSC/spermatogonia in the seminiferous tubules from both groups was similar to that of normal rats, only rats from the low‐dose group were capable of re‐initiating spermatogenesis; and by 20 weeks, greater than 75% of the tubules displayed normal spermatogenesis and the fertility of these rats rebounded. Detailed analysis by dual‐labelled immunofluorescence analysis and a functional BTB integrity assay revealed that in both treatment groups, the BTB was disrupted from week 6 to week 12. However, the disrupted BTB ‘resealed’ in the low‐dose group, but not in the high‐dose group. Our findings illustrate that SSC/spermatogonia failed to differentiate into spermatocytes beyond A aligned spermatogonia in the high‐dose group with a disrupted BTB. In short, these findings illustrate the critical significance of the BTB for re‐initiation of spermatogenesis besides SSC and spermatogonia.