Packer A I, Besmer P, Bachvarova R F
Department of Cell Biology and Anatomy, Cornell University Medical College, New York, NY 10021, USA.
Mol Reprod Dev. 1995 Nov;42(3):303-10. doi: 10.1002/mrd.1080420307.
In the mouse testis, spontaneous death of spermatogonia has a large impact on the output of differentiating spermatids. The tyrosine kinase receptor c-kit is expressed in type A, intermediate, and B spermatogonia, and kit-ligand (KL) is expressed in Sertoli cells. Previous work indicated a depletion of type A spermatogonia after in vivo exposure to an antibody that blocks c-kit function. The present work was undertaken to determine whether blocking c-kit function results in apoptosis of spermatogonia or in an inability of spermatogonia to proliferate. Testes sections were stained by a method that detects apoptotic cells in situ. In testes of 8-day postnatal (P8) males, type A spermatogonia are the predominant germ cell type present. Stained sections from P8 males injected with the c-kit antagonistic antibody ACK2 showed a fivefold higher rate of cell death than uninjected controls. At least a twofold increase was observed in P12 and P30 injected males and in P30 SId/+ males as compared to uninjected controls. Determination of the stage of germ cell development that was affected in P30 males indicated that the frequency of gonial cell death was increased fourfold, but the frequency of death in spermatocytes around the time of the meiotic division was increased 15-fold. It is concluded that KL acts to prevent apoptosis in the testis in vivo, that the membrane bound form of KL may be more effective, and that survival of late meiotic and dividing spermatocytes is regulated by KL through an indirect mechanism probably mediated by Sertoli cells. Thus, KL is an important regulator of spermatid output.
在小鼠睾丸中，精原细胞的自然死亡对分化中的精子细胞的产出有很大影响。酪氨酸激酶受体c-kit在A型、中间型和B型精原细胞中表达，而c-kit配体（KL）在支持细胞中表达。先前的研究表明，体内暴露于阻断c-kit功能的抗体后，A型精原细胞会减少。本研究旨在确定阻断c-kit功能是否会导致精原细胞凋亡或精原细胞增殖能力丧失。睾丸切片采用检测原位凋亡细胞的方法进行染色。在出生后8天（P8）雄性小鼠的睾丸中，A型精原细胞是主要的生殖细胞类型。注射c-kit拮抗抗体ACK2的P8雄性小鼠的染色切片显示，细胞死亡率比未注射的对照组高五倍。与未注射的对照组相比，在P12和P30注射的雄性小鼠以及P30 SId/+雄性小鼠中观察到至少两倍的增加。对P30雄性小鼠中受影响的生殖细胞发育阶段的测定表明，生殖细胞死亡频率增加了四倍，但减数分裂期前后精母细胞的死亡频率增加了15倍。得出的结论是，KL在体内可防止睾丸细胞凋亡，KL的膜结合形式可能更有效，减数分裂后期和分裂中的精母细胞的存活可能通过可能由支持细胞介导的间接机制受KL调节。因此，KL是精子细胞产出的重要调节因子。
