Fig. 7

Bicalutamide recipient mice lack of spermatocytes and spermatids, but possess hyper-proliferative SPCs. Bicalutamide recipient mice (n = 33) exhibited retarded body weight growth (a) and smaller testis size (b). Histology results demonstrated that spermatocytes and spermatids in seminiferous tubules of bicalutamide recipients (e) were significantly reduced compared to controls (f), bar = 20 μM. IHC staining displayed reduced number of AR⁺ cells (g) and increased number of PLZF⁺ cells (i) in bicalutamide recipients than in controls (h and j). A statistical result indicated a augmented population of PLZF⁺ cells (c) and a remarkable decline of AR⁺ cell population (d) in seminiferous tubules of bicalutamide recipients, data represent means ± SD (*p < 0.05). Accumulated spermatogonia formed two layers in bicalutamide recipient seminiferous tubules (green frame in k), while wild type seminiferous tubule possessed only one layer of spermatogonia (green frame in l). Most of spermatogonia in those two layers were β1-integrin⁺ (n), c-kit⁺ (o) PLZF⁻ (m). BrdU assay indicated they were mitosis active (p), as those in wild type (q). Spermatogonia layers were enclosed by red frames in m, n, o, p and q. Bicalutamide recipient testes displayed down-regulated expression of AR, SYCP3, Claudin-11, WT1, Nectin-2, and up-regulated expression of PLZF, GFRA1, GATA2, WT1 and β1-integrin, n = 4 (r). Androgen deprivation may block spermatogenesis at the step that β1-integrin⁺c-kit⁺ population transits to more differentiated germ cells, causing accumulation of undifferentiated spermatogonia (s). Androgen produced by Leydig cells interacts with AR in Sertoli cells to regulate down-stream target genes, and subsequently transfer differentiation signals to SPCs, and finally turns off the differentiation inhibitor gene Plzf via multiple steps. Gata2 was identified as a target of AR, and Wt1 was activated by GATA2 to regulate downstream gene β1-integrin in Sertoli cells. How β1-integrin on Sertoli cells influences SPCs’ fates via regulating Plzf is unknown (t)