New insights in testicular and sperm impacts after testicular heat stress in ruminants

• Published in: Animal reproduction science Vol. 247; p. 107140
• Main Authors: Rizzoto, Guilherme, Rossi, Eduardo S., Pupulim, Antônio G.R., Codognoto, Viviane M., Carvalho, Jaqueline C., Teixeira, Marina B., Rattes, Paula Z., Thundathil, Jacob C., Kastelic, John P., Ferreira, João C.P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-12-2022
• ISSN: 0378-4320; 1873-2232
• DOI: 10.1016/j.anireprosci.2022.107140

We reported that activation of the P53-dependent apoptotic pathway in murine testes after heat stress (HS) decreased sperm quality and caused cell death, and we subsequently confirmed activation of this pathway in cattle (Bos indicus). As the latter study did not assess sperm quality or testes, the goal of the current study was to investigate the involvement of the P53-dependent apoptotic pathway on sperm and testes from ruminants. To induce testicular HS, 20 rams were subjected to testicular insulation from 24 to 48h (scrotum covered with disposable diapers and HS confirmed by infrared thermography at diaper removal) and castrated 24h, 48h, 7 d, or 14 d after the start of insulation (5 rams per group, plus 5 control rams that were castrated but not insulated). Epididymal sperm were recovered by retrograde flow (PBS at 37°C) and analyzed with CASA (Hamilton-Thorne Bioscience®). Sperm were fixed in formalin and morphology of 200 sperm/sample were assessed with phase-contrast microscopy (1200X). Repeated-measures ANOVA followed by Tukey’s test were used to analyze all data. Insulation increased scrotal surface temperature ~ 4.2°C. HS severely impaired (P<0.05) sperm kinetics, including total motility (35.1±1.7 vs 72.1±7.7%; mean+SEM, average of all 4 HS groups vs Control), progressive motility (7.2±0.8 vs 33.5±5.6%), VAP (67.5±8.1 vs 114.4±7.6), VSL (47.4±6.1 vs 93.55±8.8), STR (51.5±6 vs 74.2±3.6), and LIN (31±3.5 vs 46.7±3.6). There were 92.5±0.1% morphologically normal sperm in Controls, with successive reductions (P<0.05) at 24 or 48h and 14 d (55.6±10.2, 32.4±1.8, and 11.7±2.0, respectively). Lastly, paired testicular weight was higher in Control rams than those at 14 d post insulation (410±56.1 vs 257± 46.9g, P<0.05).
These data were consistent with activation of a P53-dependent apoptotic pathway in ruminant testes after testicular HS. Reductions in quality of sperm in the epididymis or testes at the time of HS and decreases in testicular weight were similar to those in mice, implying a conserved mammalian response. Financial support: CAPES (88887.571133/2020-00) FAPESP (2018/02007-6) and NSERC (RGPIN 2019-04823).