Heat stress effect on the transcript abundance of testicular tissue

Abstract

The testicular temperature should remain about 3° to 5° C below body temperature for normal spermatogenesis to occur in cattle. When this situation is lost, and the testicular temperature rises, spermatogenesis is compromised. A series of seminal changes are perceived, markedly characterized by increased abnormal sperm forms and decreased sperm motility and concentration. These seminal changes are consequences of the negative effect of the thermal stress on testicular and spermatogenic cells. Although known for a long time, little is known about the pathophysiology of this process. Initially, it was believed that testicular vascularization could not maintain oxygen intake to testicular tissue during heating episodes. However, recent results from our laboratories indicate no O2 deficit in testicular tissue and that the observed changes are related to the direct effect of heating on testicular cells, and that this process is mediated by a specific gene response little is known. Therefore, to study the effects of thermal stress on testicular tissue's gene response, two experiments will be carried out. In the first, to study the triggering of gene response, Bos taurus and Bos indicus bulls (n=6 per genetic group) will be submitted to testicular insulation for 48 hours. Testicular tissue samples will be collected, using a TRU-CUT 18G needle, immediately before and 3, 6, 12, 24, and 48 hours after the beginning of insulation. The samples will be used to perform qRT-PCR for genes involved in the testes' early responses to heat stress (Early genes and genes related to steroidogenesis, protein folding, apoptosis, and oxidative stress). In the second experiment, Bos taurus and Bos indicus bulls (n=25 per genetic group) will also be submitted to testicular insulation, in the same way already described, and selected to be castrated before the start of the insulation (control; n = 5), and 24 h (n = 5), 48 h (n = 5), 7 days (n=5) and 14 days (n=5) after the beginning of the insulation. The testicular tissue samples collected at these moments will be used to perform the seq RNA technique. Blocks will also be made to manufacture histological slides, which will be used to study, in the different cell types of the testicle (Leydig cells, Sertoli and spermatogenic), utilizing laser microdissection and RT-PCR, the expression of the main genes identified by the RNA seq. (AU)