Pathogenesis of and resistance to testicular heat stress based on differentiation of spermatocytes and spermatids

Spermatogenesis includes meiosis and a complex series of steps to transform a round spermatocyte to a highly differentiated, elongated sperm. Testes must be cooler than body temperature; testicular heat stress (HS) results in sperm with abnormal shape, although some appear morphologically normal. Using a testicular HS model in mice, our objectives are to: 1) Determine expression of key molecules involved in sperm formation and their associations with histological changes during spermatogenesis; 2) Characterize the molecular profiles of spermatocytes and early spermatids that withstand HS; and 3) Evaluate progression of meiosis after HS. Mice will be anesthetized and the distal half of their abdomen put in 40 0C water for 20 min (9). Mice will be euthanized at 4, 12 and 24 h, and then every 4.3 d (half seminiferous epithelium cycle) after HS, until completion of a full cycle of spermatogenesis (43 d). A control group will be submerged in 33 0C water (thermoneutral). Genes of interest will be screened by RT-qPCR or differential gene expression, with immunohistochemistry and/or in situ hybridization to localize targeted molecules of interest and spatial sequencing on formalin-fixed testicular tissue. Data collection is underway and data will be presented at the time of the meeting.