Figure 1.

Stem cells survive chemotherapy and can restore spermatogenesis. (A) Stem cells biology of testicular VSELs and SSCs. VSELs are spherical cells of small size (3–5 µm) which give rise to SSCs (>5 µm) by asymmetric cell division (ACD). SSCs divide by symmetric cell division (SCD) and also undergo clonal expansion implying rapid division with incomplete cytokinesis. Spermatocytes then undergo meiosis to produce spermatids which undergo further spermiogenesis resulting in sperm. Similar ACD, SCD and clonal expansion was reported in testicular cell smears, for the first time by Patel and Bhartiya (22) on treating chemoablated mouse with follicle stimulating hormone (10 IU). (B₁) Cells separated from busulphan treated mouse testis show both ACD (broken circle) and SCD (arrow) after 24 h in culture whereas the Sertoli cells attach at the bottom as a feeder support to facilitate differentiation of stem cells. (B₂) Stem cells undergo clonal expansion by 3 days in culture to form clusters wherein cells retain cytoplasmic connectivity. (B₃) Large numbers of spermatids are observed in culture by 2 weeks. (C) H&E stained cells undergoing various stages of sperm differentiation from spermatids after 3 weeks culture. Various stages of spermiogenesis were evident. Round spermatocytes with protruding tail, spermatid, elongated spermatid with prominent tail, with residual cytoplasmic bodies, fully mature sperm with a long tail, hook shaped head and prominent mid-piece were observed. (C₈,C₉) At places sperm were observed in clusters with their heads embedded in residual cytoplasmic body. Bar =10 µm. This work has been published earlier by Anand et al. (12).