Proliferating cell nuclear antigen as a molecular biomarker for spermatogenesis in PTU-induced hypothyroidism of rats

The thyroid hormone has few serious effects on the testes except during the neonatal stage. There is little knowledge concerning the prolonged effect of thyroid hormone deficiency throughout the rat's life span and its effect on spermatogenesis. Proliferating cell nuclear antigen (PCNA) is a nuclear matrix protein, which is essential for multiple cell cycle pathways. Here we used PCNA immunohistochemistry as a marker to differentiate between the testes of control and hypothyroid rats. About 20 rats were equally divided into 2 groups; the first group was the control group, while the second group was the experimental group in which rats were fed 0.05% 6-n-propyl thiouracil (PTU) in drinking water for 6 weeks. Immunohistochemistry, using an antibody against PCNA, showed at least 3 differences in the pattern of PCNA immunoreactivity (PCNA-ir). First, PCNA-ir was not detected in Sertoli and Leydig cells in the testes of control rats and detected in some of the hypothyroid rats. Second, in the control group more than 96% of spermatogonia were PCNA-positive cells; however, hypothyroidism caused the reduction to approximately 25% PCNA staining in spermatogonia. The third difference was in the abnormal distribution of spermatogonia seen in the hypothyroid rat testis, not in the control one. These results suggest that prepubertal hypothyroidism affects the proliferation of spermatogenic cells leading to impaired spermatogenesis and that PCNA index is a useful marker for assessing germ cell kinetics and spermatogenesis in prepubertal hypothyroidism.