Fig. 4

Testicular histology 3 months after transplantation. The significant increase of testis size (a) and testis-to-body weight ratio (b) was found in transplanted groups compared to controls (control vs. SSCT, P = 0.012; control vs. MS-SSCT, P = 0.004, and control vs. MSi-SSCT, P < 0.001). However, no difference was observed for the seminal vesicle-to-body weight ratio (c). Resumption of spermatogenesis was found to be significantly improved in all transplanted groups compared to controls (P < 0.001) (d, e); Tubular fertility index (TFI) did not differ between SSCT and MSi-SSCT groups (e). Donor-derived spermatogenesis was confirmed with immunohistochemistry for GFP (f). Donor-derived TFI was found to be significantly different between SSCT and MSi-SSCT (P < 0.001), MSCT and MSi-SSCT (P < 0.001), and MS-SSCT and MSi-SSCT (P < 0.001) (g). SSCT, spermatogonial stem cell transplantation; MSCT, mesenchymal stem cell transplantation; MS-SSCT, transplantation of mesenchymal stem cells together with spermatogonial stem cells; MSi-SSCT, transplantation of TGFß1-treated mesenchymal stem cells together with spermatogonial stem cells. a Scale bar = 2 mm