Tanemura K, Kanai Y, Kanai-Azuma M, Kurohmaru M, Kuramoto K, Yazaki K, Hayashi Y
Department of Veterinary Anatomy, Faculty of Agriculture, University of Tokyo, Japan.
Biol Reprod. 1996 Dec;55(6):1237-42. doi: 10.1095/biolreprod55.6.1237.
The seminiferous epithelia of old mice (33 mo of age) are composed of spermatogonia and Sertoli cells. Histochemical examination using the anti-c-kit monoclonal antibody demonstrated that the number of differentiating type A spermatogonia decreases with age. To elucidate the differential activity of old mouse spermatogonia, we transplanted extremely thin seminiferous epithelia of old BDF, mice into W/Wv mouse testes and examined whether or not they could reinitiate differentiation. Artificially cryptorchid mice were used as the control. At 2 wk after transplantation, spermatocytes and round spermatids were detected in transplanted seminiferous tubules of the control, whereas the most advanced spermatogenic cells in those of old mice were spermatocytes. At 4 wk after transplantation, although elongated spermatids were detected in transplanted tubules of the control, haploid cells (spermatids) were still undetectable in those derived from old mice. Thus, meiosis was never restored, although spermatogonia of old mice can reinitiate differentiation into spermatocytes under suitable testicular conditions. Since it has been reported in several mammalian species that age-related changes in the testicular microenvironment lead to the gerontal cessation of spermatogenesis, the present results suggest that both a defective extratubular environment and a defective intratubular environment may cause the cessation of spermatogenesis in old BDF, mice.
老年小鼠（33月龄）的生精上皮由精原细胞和支持细胞组成。使用抗c-kit单克隆抗体进行的组织化学检查表明，分化型A精原细胞的数量随年龄增长而减少。为了阐明老年小鼠精原细胞的差异活性，我们将老年BDF1小鼠的超薄生精上皮移植到W/Wv小鼠睾丸中，并检查它们是否能够重新启动分化。人工隐睾小鼠用作对照。移植后2周，在对照的移植生精小管中检测到精母细胞和圆形精子细胞，而老年小鼠的生精小管中最先进的生精细胞是精母细胞。移植后4周，虽然在对照的移植小管中检测到了伸长的精子细胞，但在老年小鼠来源的小管中仍未检测到单倍体细胞（精子细胞）。因此，虽然老年小鼠的精原细胞在合适的睾丸条件下可以重新启动分化为精母细胞，但减数分裂从未恢复。由于在几种哺乳动物物种中都报道过，睾丸微环境中与年龄相关的变化会导致老年期精子发生停止，目前的结果表明，管外环境缺陷和管内环境缺陷都可能导致老年BDF1小鼠精子发生停止。
