| Transforming growth factor beta(TGF-β)super-family is an important local regulator of testicular activities. Smad(Sekclsky mothers against dpp)proteins are downstream intracellular signaling mediators for TGF-βsuper-family members. They can transduce signals from transmembrane serine/threonine kinase receptors to the nucleus and have effect of transcription activity. Smads expression in testis is developmental and stage-specific, which related to the cycling of seminiferous tubules. Electromagnetic pulse (EMP) is a kind of high energy and ultra wide band electromagnetic wave. After irradiation, the structure and function of spermatogenic cell, Sertoli cell and Leydig cell were damaged, and the expression of TGF-βs and their receptors altered. But little is know about the role of Smads and their pathways in the effect of electromagnetic pulse (EMP) irradiation on mice testes.Objectives and Methods: To investigate the influence of electromagnetic pulse (EMP) irradiation on mice testes and the role of Smads and TGF-β/Smads pathways in this effect, the expression and localization of Smads were observed after EMP whole-body irradiation by measurement of immunohistochemistry employing specific polyclonal antibodies, as well as the changes of mice cycle of seminiferous epithelium. To shed light on the relationship of Smad4 protein and apoptosis of spermatogenic cells, the apoptosis of spermatogenic cells in normal and irradiated mice testes was detected by means of TUNEL method and the Smad4 expression was observed with immunohistochemical staining method.Results:⒈In the seminiferous tubules, the localization of Smad4, Smad1 and Smad5 in the EMP group were significantly different from the control group. The expression densities of smad4, smad1 and smad5 changed significantly on 1, 7, 14, 21and 28 days after irradiation.In normal adult male testis, the immunolocalization showed that Smad4 was mainly localized in the cytoplasm of Leydig cells, and was faintly expressed in Sertoli cells. After irradiation, Smad4 expression was significantly decreased in Leydig cells, and was obvious in the cytoplasm of pachytene spermatocytes and late spermatids.In the testis of normal adult males, Smad1 expression initiates in the pachytene spermatocytes of stage V seminiferous tubules, peaks at stage X, then decrease as pachytene spermatocytes differentiate into secondary spermatocytes and then round spermatids. After irradiation of EMP, the expression of Smad1 was obvious in round and elongated spermatids, and decreased in spermatocytes.In normal adult males, Smad5 was predominant in the nucleus of early spermatocytes and round spermatids but weak in the nucleus of spermatogonium. After irradiation, Smad5 was only expressed in releasing and elongated spermatids.⒉Severe injuries were observed 1day after the radiation and seminiferous epithelium was mostly recovered 28d after the radiation. The localization of smad4 was significantly different in EMP group compared to the control group, and the expression densities of smad4 decreased significantly at 7, 14and 21d after irradiation (p<0.05). TUNEL assays demonstrated that there was a significant increase in the mean apoptotic index (AI) in irradiation groups than that of control groups (p<0.01).Conclusions: The expression of Smads in irradiation groups of mice indicates that Smad4, Smad1, Smad5 and BMPs/Smad signal pathway may play an important role in the process of impairment and repair of mouse testis irradiated by EMP.The TUNEL method results suggested that Smad4 and TGF-β/Smad signal pathway might play an important role in spermatogenic cells apoptosis induced by radiation of EMP.
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