Chronic Scrotal Heat Stress Causes Testicular Interstitial Inflammation and Fibrosis
Nguyen Thanh Tung1,2, Dang Van Phuoc1, Dang Ngoc Phuc3, Dang Cong Thuan4, Le Minh Tam5, Nguyen Vu Quoc Huy5, Kim Won6
1 Institute of Biomedicine, Hue University of Medicine and Pharmacy, Hue University.
2 Faculty of Basic Science, Hue University of Medicine and Pharmacy, Hue University.
3 Faculty of Medicine, Dong A University
4 Department of Histology, Embryology, Pathology and Forensic, Hue University of Medicine and Pharmacy, Hue University.
5 Department of Obstetrics and Gynecology, Hue University of Medicine and Pharmacy, Hue University.
6 Department of Internal Medicine, Jeonbuk National University, Korea
Background: Chronic heat stress induced testicular damage and function therefore adversely affect their reproduction. The damaged testicles respond to self-defense reactions, in which inflammation and fibrosis are two important processes. Inflammatory and fibrosis lesions correlates with testicular dysfunction and impaired spermatogenesis. The aim of the study was to determine the association of chronic scrotal heat stress with testicular interstitial inflammation and fibrosis.
Method: Thirty adult male mice with aged 10-12 weeks were distributed into three groups. Heat stress groups was submerged in a water bath for at 37 °C and 40 °C, respectively. Control group was treated within the same way in water bath maintained at 25 °C. All animals were sacrificed after completion of five consecutive week heat exposure. Characteristics of testicular interstitial inflammation and fibrosis were determined by H&E staining, Picro sirius red staining and immunohistochemistry straining.
Results: Chronic scrotal heat stress impairs spermatogenesis in the testicles with the absence of spermatogenesis cells in the lumen, reversing histological structure and decreasing Johnsen score. Ki-67 immunohistochemistry staining show that heat stress significantly induced an increased interstitial cells proliferation. Normal testicular tissues express low levels of intercellular adhesion molecule-1 (ICAM-1). Meanwhile, up-regulation of ICAM-1 expression was observed in heat stress induced testicular interstitial tissue. Macrophage migration was stimulated by chronic scrotal heat stress. The number of F4/80-positive macrophage in testicular interstitial tissue was significantly increased in heat exposed group compared to those in control group. Fibroblast-specific protein 1 (FSP-1), key mediators of fibrosis in many organs, was inducted by chronic scrotal heat stress. The number of FSP-1-positive fibroblasts in testicular interstitial was significantly increase in heat exposed group compared to those in control group. Moreover, extracellular matrix collagen accumulation following scrotal heat stress was strong detected in interstitial tissue. Histological visualization of excessive collagen deposition show that heat stress exposed was significantly induced collagen fibers accumulation in testicular interstitial compared to those in unexposed group.
Conclusions: Chronic scrotal heat stress adversely affects the testicles, causes inflammation and progress to testicular interstitial fibrosis.
Keywords: Heat stress, inflammation, fibrosis, testicular interstitial tissue, Johnsen score, spermatogenesis
* Corresponding author: Nguyen Thanh Tung, PhD; nttung@huemed-univ.edu.vn