Hypothermia attenuates radiation-induced testicular injury in mice

Ionizing radiation damages testicular tissue, impairing spermatogenesis and fertility. Therapeutic hypothermia confers cytoprotection; its ability to limit radiation-induced testicular injury is unclear. We tested whether hypothermia mitigates irradiation-induced testicular injury and explored underlying mechanisms. Mice were randomized to four groups: normothermia sham (NT + sham), hypothermia sham (HT + sham), normothermia with irradiation (NT + IR; 5 Gy whole-body X-ray), or hypothermia with irradiation (HT + IR). Temperatures were maintained at 37 ± 0.5 °C (normothermia) or 32 ± 0.5 °C (hypothermia) for 2 h before and after irradiation. Outcomes at 12 h and 30 d included histological evaluation, organ weight measurements, sperm analyses, TUNEL apoptosis, quantitative reverse transcription polymerase chain reaction and Western blot analyses for Bax/Bcl-2 expression, and Western blot analysis for p-Akt/Akt. At 30 d, irradiation reduced testicular and epididymal weights in the NT + IR group; hypothermia significantly attenuated epididymal weight loss and showed a nonsignificant trend toward higher testis weight in the HT + IR group (p = 0.1064). H&E morphometry indicated preserved seminiferous architecture, with greater germinal epithelial height and tubular diameter in HT + IR vs. NT + IR. Irradiation increased sperm abnormalities and decreased motility and counts in NT + IR. Although motility improved in HT + IR compared with NT + IR, hypothermia did not rescue spermatid number and showed a trend toward higher total sperm counts (p = 0.0560). At 12 h, irradiation increased TUNEL-positive nuclei and the Bax/Bcl-2 ratio, whereas hypothermia lowered both in irradiated testes. Hypothermia also increased p-Akt (p-Akt/Akt) only in irradiated animals, indicating early activation of pro-survival signaling. Collectively, hypothermia partially mitigated radiation-induced testicular injury, supporting its potential to preserve reproductive capacity during radiation therapy and after emergency exposures.