Tung Nguyen-Thanh - Faculty of Basic Science, Hue University of Medicine and Pharmacy, Hue University, Hue, Vietnam. Institute of Biomedicine, Hue University of Medicine and Pharmacy, Hue University, Hue, Vietnam.
Phuoc Dang-Van - Forensic Medicine Center in Thua Thien Hue Province, Hue, Vietnam.
Phuc Dang-Ngoc - Faculty of Medicine, Dong A University, Da Nang, Vietnam.
Won Kim - Department of Internal Medicine, Jeonbuk National University Medical School, Jeonju, Republic of Korea.
Tam Le-Minh - Department of Obstetrics and Gynecology, Hue University of Medicine and Pharmacy, Hue University, Hue, Vietnam.
Quoc-Huy Nguyen-Vu - Department of Obstetrics and Gynecology, Hue University of Medicine and Pharmacy, Hue University, Hue, Vietnam.

Background: Chronic heat stress is a risk factor that adversely affects the reproduction system. Inflammation and fibrosis are ۲ important response processes to damaged tissues. Objective: This study investigates the association of chronic scrotal heat stress with testicular interstitial inflammation and fibrosis in mice. Materials and Methods: For all experiments, ۸-۱۰ wk old male Swiss mice (Mus musculus) (۲۰-۲۳ gr) were divided into ۳ groups (n = ۱۰/each). The heat stress groups were submerged in a water bath at ۳۷°C and ۴۰°C, while the control group was treated at ۲۵°C. The testicular tissues were performed hematoxylin and eosin staining, picro sirius red staining, and immunohistochemistry for intercellular adhesion molecule-۱, fibroblast-specific protein ۱, F۴/۸۰, collagen I, and Ki-۶۷ staining to determine the testicular interstitial inflammation and fibrosis. Results: 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-۱ expression in the interstitial testicular tissue. In the interstitial testicular tissue, the number of F۴/۸۰-positive macrophages and the number of fibroblast-specific protein ۱-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. Conclusion: Heat stress adversely affects the testicular structure and spermatogenesis, causes inflammation, and progresses to testicular interstitial fibrosis.

Heat stress, Testicular, Inflammation, Fibrosis.