Figure 7: Histological sections of busulphan treated mouse testes after two months of inter-tubular Sertoli cells transplantation. Note the presence of two distinct populations of seminiferous tubules (A,B) including small empty tubules which are possibly the ‘neo-formed tubules’ from the transplanted Sertoli cells [resemble mini-tubules described earlier by Shinohara et al (38) and Zhang et al (32)] and the bigger ‘old’ native tubules with focal spermatogenesis and presence of sperm. The sperms are however not arranged in a radial manner (C-G) as in normal testis (Fig 6A,B). The ‘neo-formed’ tubules are located in close vicinity of bigger tubules (D,E, arrows) and are probably a source of growth factors and cytokines which possibly stimulate the VSELs in the ‘old’ native tubules to undergo differentiation resulting in sperm production. Interestingly the Sertoli cells are very prominent in the ‘neo-formed tubules’ and hardly observed in the ‘old’ tubules. Absence of Sertoli cells in the tubules where spermatogenesis is restored may explain why spermatogenesis is not well organized, but rather remains focal in nature (G). Bar=20μm.