Laboratory of Teaching and Research in Pathology of Reproduction, Center of Biotechnology in Animal Reproduction, Department of Animal Reproduction, School of Veterinary Medicine and Animal Science, University of São Paulo (USP), Pirassununga, SP, Brazil.
Laboratory of Semen Biotechnology and Andrology, Center of Biotechnology in Animal Reproduction, Department of Animal Reproduction, School of Veterinary Medicine and Animal Science, University of São Paulo (USP), Pirassununga, SP, Brazil.
J Therm Biol. 2022 May;106:103237. doi: 10.1016/j.jtherbio.2022.103237. Epub 2022 Apr 7.
Heat stress (HS) affects spermatogenesis and sperm maturation, decreasing sperm quality. Yet sperm morpho-functional changes caused by HS in Nellore bulls are not fully elucidated. This study aimed to show the chronological effects on sperm quality of HS during spermatogenesis and sperm maturation until recovery of the seminiferous epithelium in Nellore bulls. Nine Nellore bulls were distributed into control and heat stress (HS-scrotal bags/96 h) groups. The study was divided into five Periods: 1. Control (14-7 days before HS); 2. Stored sperm (0-7 days after HS); 3. Sperm maturation and late spermatogenesis (14-42 days after HS); 4. Early spermatogenesis (49-63 days after HS), and 5. Recovery (70-77 days after HS). Semen was collected once a week and evaluated for sperm motility, morphology, plasma, acrosome, and mitochondrial membranes, lipid peroxidation, and DNA fragmentation. Sperm characteristics were similar between groups in Periods 1 (control). During Period 2, HS increased detached normal head defect and decreased mitochondrial membrane potential, denoting effects on the sperm stored at the epididymis cauda. In Period 3, HS decreased sperm motility, plasma membrane integrity, and mitochondrial membrane potential and increased abnormal sperm, lipid peroxidation, and DNA fragmentation; reflecting the effects on sperm that were in the epididymis body and head and late spermatogenesis (spermiogenesis and meiosis). In Period 4, HS maintained a reduction in the mitochondrial membrane potential and an increase in abnormal sperm; injuries that could occur during early spermatogenesis (mitosis). Finally, in Period 5, the groups were similar, confirming the recovery of the seminiferous epithelium after HS. This study provides insights on the effects of HS on the complete process of sperm maturation and spermatogenesis, until recovery in sperm from Nellore bulls.
热应激（HS）会影响精子发生和精子成熟，降低精子质量。然而，Nellore 公牛的 HS 引起的精子形态和功能变化尚未完全阐明。本研究旨在展示 HS 在Nellore 公牛精子发生和精子成熟过程中对精子质量的时间影响，直至生精上皮恢复。将 9 头 Nellore 公牛分为对照组和热应激（HS-阴囊袋/96 h）组。研究分为五个时期：1. 对照（HS 前 14-7 天）；2. 储存精子（HS 后 0-7 天）；3. 精子成熟和晚期精子发生（HS 后 14-42 天）；4. 早期精子发生（HS 后 49-63 天）和 5. 恢复（HS 后 70-77 天）。每周采集一次精液，评估精子运动、形态、血浆、顶体和线粒体膜、脂质过氧化和 DNA 碎片化。第 1 期（对照）两组的精子特征相似。第 2 期，HS 增加了脱落的正常头部缺陷，降低了线粒体膜电位，表明对附睾尾部储存的精子有影响。第 3 期，HS 降低了精子运动、质膜完整性和线粒体膜电位，增加了异常精子、脂质过氧化和 DNA 碎片化；反映了对附睾体和头部以及晚期精子发生（精子发生和减数分裂）中的精子的影响。第 4 期，HS 保持了线粒体膜电位的降低和异常精子的增加；这些损伤可能发生在早期精子发生（有丝分裂）期间。最后，在第 5 期，两组相似，证实了 HS 后生精上皮的恢复。本研究为 HS 对 Nellore 公牛精子成熟和精子发生全过程的影响提供了新的认识，直至精子恢复。
