Age-related changes in the immunohistochemical localization pattern of α-smooth muscle actin and vimentin in rat testis

Introduction:The characteristic expression pattern of α-smooth muscle actin (α-SMA) and vimentin during postnatal development of the testis was examined thoroughly. However, little is known about its distributional changes during aging. Aim of the work: The present study was carried out to clarify the age-related changes in the expression of α-SMA and vimentin in rat testis. Materials and methods:This study was carried out on 48 male albino rats of different ages (groups I, II, III, and IV included 6-, 12-, 24-, 30-month-old rats, respectively). The testes were excised and processed for immunohistochemical staining for α-SMA and vimentin. Results:Group I testes showed a positive α-SMA reaction in the cytoplasm of the peritubular myoid cells (PMCs) surrounding the seminiferous tubules (STs) as well as in both the endothelium and the smooth muscle cells (SMCs) in the wall of blood vessels. A positive vimentin reaction was observed in the cytoplasm of Sertoli cells and Leydig cells, and in the endothelium and SMCs of the blood vessels. Group I I testes showed positive α-SMA in the thickened PMCs and a decreased reaction in some PMCs with a vacuolated cytoplasm. In addition, the STs showed variable grades of positive vimentin in the Sertoli cells. Group I II testes showed a significant decrease (P 0.05) in both the α-SMA and the vimentin reaction in some PMCs as well as in the Sertoli and Leydig cells, respectively. The atrophic STs showed a disorganized arrangement of the vacuolated Sertoli cells. The wall of the blood vessels appeared thick, with a significant decrease (P 0.05) in both α-SMA and vimentin reactions in the vacuolated cytoplasm of the SMCs. Group IV testes showed a significant decrease (P 0.05) in α-SMA in the STs and a redundant PMCs layer. A few thick PMCs were also observed around the atrophic and the disrupted STs. The majority of the atrophic STs showed either a disorganized or an add-luminal arrangement of the detached Sertoli cells, with a significant decrease (P 0.05) in the vimentin reaction. The thickened vessels showed significantly decreased (P 0.05) α-SMA and vimentin in the vacuolated cytoplasm of the endothelium and the SMCs. Conclusion: These age-related alterations in α-SMA and vimentin expression as well as changes in the vascular wall in rat testis may play a role in or may be responsible for senile testicular atrophy.