Extracellular matrix interaction and apoptosis of the epididymal epithelium following hypothyroidism in Balb/C mouse

The role of the epididymis in post-testicular maturation of spermatozoa is to gain the potential to fertilize the ovum. It is well known that thyroid malfunction has a negative impact on the male reproductive system. Hypothyroidism (underactive thyroid gland) causes marked structural and functional changes in the epididymis, as well as being able to influence extracellular matrix (ECM) proteins secretion and cell death. This study was designed to characterize the effects of hypothyroidism on epididymis’ structure. Twenty Balb/C mice were randomly divided into control, and hypothyroid group which received 0.05% 6-n-propyl-2-thiouracil (PTU) for 35 days. At the end of the experiment, to confirm the hypothyroidism, T4 and thyroid-stimulating hormone (TSH) levels were measured using chemiluminescent immunoassay kit. Real-time PCR, immunohistochemistry, periodic acid-Schiff (PAS) staining, TUNEL assay, and biochemical measurements were carried out. Based on the results, T4 level was significantly lower in the hypothyroid group compared to the control group, whereas TSH level increased in hypothyroid group compared to the control group (p < 0.05). Laminin α5 and collagen IV mRNA levels were upregulated in the hypothyroid group compared to the control group (p < 0.05). However, no significant difference was observed in the immunoreactivity of laminin α5 and collagen IV proteins between the two groups. Also, in PAS staining, no significant differences were found in the basement membrane (BM) staining intensity between the two groups. Hypothyroidism markedly increased epididymal epithelium apoptosis (p < 0.05). Besides, hypothyroidism reduced superoxide dismutase (SOD) enzyme activity while increasing the malondialdehyde (MDA) level (p < 0.05). Collectively, data indicated a possible relationship between alterations in the BM components and biochemical factors and increased apoptosis in the epididymal cells. These results suggest a regulatory role of thyroid hormones on the BM and structure of epididymis.