Chronic scrotal heat stress causes testicular interstitial inflammation and fibrosis: An experimental study in mice

Chronic heat stress is a risk factor that adversely affects the reproduction system. Inflammation and fibrosis are 2 important response processes to damaged tissues.

This study investigates the association of chronic scrotal heat stress with testicular interstitial inflammation and fibrosis in mice.

For all experiments, 8-10 wk old male Swiss mice (Mus musculus) (20-23 gr) were divided into 3 groups (n = 10/each). The heat stress groups were submerged in a water bath at 37°C and 40°C, while the control group was treated at 25°C. The testicular tissues were performed hematoxylin and eosin staining, picro sirius red staining, and immunohistochemistry for intercellular adhesion molecule-1, fibroblast-specific protein 1, F4/80, collagen I, and Ki-67 staining to determine the testicular interstitial inflammation and fibrosis.

Chronic scrotal heat stress impairs spermatogenesis and reverses testicular histological structure. Heat stress significantly induced increased interstitial cell proliferation and upregulation of intercellular adhesion molecule-1 expression in the interstitial testicular tissue. In the interstitial testicular tissue, the number of F4/80-positive macrophages and the number of fibroblast-specific protein 1-positive fibroblasts were significantly increased in the heat-exposed groups compared to those in the control group. The heat exposed groups strongly increased extracellular matrix collagen accumulation in testicular interstitial tissues.

Heat stress adversely affects the testicular structure and spermatogenesis, causes inflammation, and progresses to testicular interstitial fibrosis.