Effect of Kallikrein-related Peptidase KLK1 on Ameliorating Spermatogenesis Regeneration in Busulfan-induced Azoospermic Mice and Promoting Mouse Spermatogonial Stem Cell Proliferation In Vitro

Abstract

To investigate the effect of kallikrein-related peptidase KLK1 on azoospermic mice induced by busulfan and mouse spermatogonial stem cell. Mice were treated with a single intraperitoneal injection of busulfan, and 4 weeks later, they received a daily intraperitoneal injection of KLK1 at different doses for another 4 weeks. Eight weeks after the busulfan treatment, all mice were sacrificed and their testes were collected for histological evaluation, immunostaining and protein extraction. In vitro, immortalized mouse spermatogonial stem cells, namely C18-4 cells, were treated with KLK1 for proliferation assays. Histological evaluation of testes, epididymis and epididymal fluid showed that KLK1-treated mice had better spermatogenesis than the control group. Immunostaining showed that tissue samples from testes of KLK1-treated mice had more PLZF- and SCP3-positive cells per seminiferous tubule as well as more PNA-positive cells in the seminiferous tubules. Western blots revealed higher expression levels of PCNA in KLK1-treated mice than in control mice. C18-4 cells treated with KLK1 had a higher proliferation rate and higher expression levels of PCNA, Cyclin A and Cyclin E, and the level of phosphorylated ERK2 were increased after KLK1 treatment. Collectively, KLK1 can improve spermatogenesis in azoospermic mice, and KLK1 can promote the proliferation of mouse spermatogonial stem cells via activating ERK1/2 and cell cycle proteins Cyclin A and Cyclin E. This study could offer novel approach and provide new targets for the treatment of azoospermia.