The Relationship between Extracellular Matrix Proteins and Germ Cells Apoptosis in Balb/C Mouse Testis following Experimental Hypothyroidism Running title: Hypothyroidism on ECM and germ cells apoptosis of testis

Objectives: Dysfunction of the thyroid gland has a negative effect on the male reproductive system. Studies also show that extracellular matrix (ECM) components play an essential role in testicular development and function. In Hypothyroidism, there is a significant disruption in the ECM structure of mammalian tissues. Also, notable changes have been reported in the germ cell population under hypothyroid state. This study aimed to investigate the relationship between ECM proteins and Apoptosis of testicular germ cells due to Hypothyroidism.Materials and Methods:In the present experimental study, ۲۰ male Balb/C mice were divided into control and hypothyroid groups. Hypothyroid group was received ۰.۰۵% ۶-n-propyl-۲-thiouracil (PTU) through drinking water for ۳۵ days. After confirmation of hypothyroidism, Real-Time PCR, immunohistochemistry, Periodic Acid-Schiff (PAS) staining, TUNEL assay, and biochemical measurements were performed.Results: Laminin α۵ and collagen IV mRNA levels were upregulated in the hypothyroid group compared to the controls (p<۰.۰۵). Also, a strong immunoreactivity of collagen IV and laminin α۵ was observed in the basement membrane (BM) of hypothyroid mice (p<۰.۰۵). By contrast, there was no significant difference in PAS staining between the case and control groups. The number of TUNEL-positive germ cells in hypothyroid mice increased significantly compared to control mice. Moreover, PTU administration reduced superoxide dismutase (SOD) activity, while it increased malondialdehyde (MDA) level (p<۰.۰۵). However, there was no significant difference in thiol content between the two groups.Conclusions: Based on the present study results, it can be said that Hypothyroidism can cause changes in BM components and increase the Apoptosis of germ cells by inducing lipid peroxidation (LPx) and reducing the activity of antioxidant defense molecules.

Keywords:

Hypothyroidism , Laminin α۵ , Collagen IV , Germ cell , Apoptosis