Expression Of P38 MAPK In Normal Mouse Testis During Postnatal Development And Experimental Cryptorchidism

Mammalian spermatogenesis is a unique and complex developmental process. Spermatogonia, the stem cell population undergo mitosis and differentiate into primary spermatocytes. These cells in turn undergo meiosis, and differentiate into secondary spermatocytes and spermatids. The round spermatids then transform into mature spermatozoons via metamorphosis. Germ cell apoptosis also occurs during the differentiation process. However, the molecular mechanisms underlying these processes are poorly understood.Mitogen-activated protein kinase (MAPK) pathway is an important cell signal transduction system and can mediate many cellular process including cell growth, division, development, apoptosis and function coordination between cells, etc. Four subfamilies of MAPK have been identified in mammalian cells; these are ERK, JNK/SAPK, ERK5/BMK1 and p38MAPK. Despite their relative independent function, there still is interaction betweenThis research was funded by the grants from National Natural ScienceFoundation of China (39870109)- 4 -different MAPK pathways. Among all four subfamilies, p38MAPK is involved in the regulation of stress, inflammation and cell proliferation. Recently, more studies on the function of p38 MAPK during spermatogenesis have been done. However, the expression of p38 MAPK and its change in testis during postnatal development is still unclear. To investigate, we conducted following experimrnts:Using Western blots and immunohistochemical SABC method, we detected the expression and cellular location of p38 MAPK in 1-to 7 -week-old mice testes. The percentage of immunohistochemical positive area at each development stage was measured by image analysis system and the data were analyzed by one-way ANOVA with SPSS 10.0 for Windows.We established mouse model with unilateral cryptorchidism. The expression of p38 MAPK in experimental cryptorchidism was detected by immunohistochemical SABC method at 5, 10, 15 and 20 days after the procedure respectively. The results of immunostaining were measured by image anslysis system and analyzed by one-way ANOVA with SPSS 10.0 for Windows.The results were as follows:The Western Blots showed that p38 MAPK was expressed from 2- to 7-week-old mice testis. The immunostaining of p38 MAPK occurred first in spermatogonium of 2-week-old mice's testes. Only a few seminiferous tubules were p38 MAPK positive in 3- to 5-week-old mice, whereas the expression of p38 MAPK was abundant in testes of 6- and 7-week-old mice. The immunostaining of- 5 -p38 MAPK was localized in the nucleus of spermatogonium and primary spermatocyte. In addition, the cytoplasm of some Leydig cells in the testes of 7-week-old mice was p38 MAPK positive.The expression of p38 MAPK did not differ between experimental cryptorchidism and normal testes at 5 days after the cryptorchidism procedure. Since 10 days after the procedure, the structure of seminiferous tubules in experimental cryptorchidism was destroyed, and the expression of p38 MAPK decreased obviously compared with normal testes. The result of image and statistical analysis showed that the expression of p38 MAPK in experimental cryptorchidism decreased gradually after the procedure.The above result suggests that p38 MAPK may play an important role in promoting testicular development and maintaining spermatogenesis, as well as in germ cell apoptosis. The expression of p38 MAPK in mouse testes during postnatal development and experimental cryptorchidism provides an insight into the regulatory mechanism of p38 MAPK in mouse spermatogenesis and testicular function, and has important significance for entirely understanding the action mechanism of p38 MAPK in reproduction and development.