Dep. Animal Reproduction, INIA-CSIC, 28040 Madrid, Spain.
Dep. Animal Reproduction, INIA-CSIC, 28040 Madrid, Spain.
Animal. 2023 May;17 Suppl 1:100741. doi: 10.1016/j.animal.2023.100741.
Reproductive technologies can help to protect wild ruminant species from becoming extinct. In addition, the decline in some wild game species has also raised interest in reproductive technologies to increase the number of animals that can be produced. Most biobanking efforts have focused on developing effective protocols for preserving sperm, oocytes, and embryos. Cryopreservation of sperm remains the least invasive method and the cheapest procedure for germplasm storage. Over the last few years, several reproductive biotechnologies have been developed beyond the conventional freezing of spermatozoa. These include ultra-rapid freezing techniques. Nevertheless, fertility results after artificial insemination using frozen-thawed spermatozoa are not always acceptable in wild small ruminants. Moreover, these technological efforts have met variable success related to the sample's origin (epididymal retrieved postmortem or ejaculated) and the season of sperm sample collection and storage. Epididymal sperm shows higher cryoresistance than ejaculated sperm. Changes in sperm proteome between epididymal and ejaculated sperm seem to contribute to this different cryotolerance. The role of endocrine status has been studied in some wild species to better understand the underlying mechanism of the annual variation in ruminant sperm cryoresistance. Seasonal changes in testosterone and prolactin are involved in sperm cryoresistance; sperm recovery and cryopreservation are recommended around the end of the rutting season, when good quality sperm samples can still be obtained, testosterone levels have already decreased, and prolactin concentrations remain low. The mechanisms of hormone action on sperm freezability are not well known. Still, it has been suggested that testosterone affects cell proliferation in the testis, during spermatogenesis, and membrane properties of sperm cells during their transit through the reproductive tract, which might influence their cryotolerance. Recent studies have revealed that the expression of aquaporins in the sperm cells of small wild ruminants could also be involved in the androgen-related seasonal variation of sperm cryoresistance. Along with epididymal and ejaculated spermatozoa, the cryopreservation of testicular tissue may provide a suitable source of male gametes, becoming an alternative for establishing germplasm banks when semen cannot be collected for whatever reason.
生殖技术可以帮助保护野生反刍动物物种免于灭绝。此外，一些野生猎物物种的减少也引起了人们对生殖技术的兴趣，以增加可以生产的动物数量。大多数生物库工作都集中在开发有效的精子、卵母细胞和胚胎保存方案上。精子的冷冻保存仍然是最具侵袭性的方法，也是最便宜的种质储存程序。在过去的几年中，除了常规的精子冷冻之外，还开发了几种生殖生物技术。这些技术包括超速冷冻技术。然而，在野生小反刍动物中，使用冷冻解冻精子进行人工授精的生育结果并不总是令人满意。此外，这些技术努力在与样本来源（死后从附睾中取出或射出的）和精子样本采集和储存的季节有关的方面取得了不同程度的成功。附睾精子比射出的精子具有更高的抗冷冻性。附睾和射出精子之间的精子蛋白质组变化似乎导致了这种不同的抗冷冻性。已经在一些野生物种中研究了内分泌状态的作用，以更好地了解反刍动物精子抗冷冻性的年度变化的潜在机制。睾酮和催乳素的季节性变化与精子抗冷冻性有关；建议在发情季节末期进行精子回收和冷冻保存，此时仍可以获得高质量的精子样本，睾酮水平已经下降，催乳素浓度仍然较低。激素对精子可冻性的作用机制尚不清楚。尽管如此，据推测，睾酮会影响精子发生过程中睾丸中的细胞增殖以及精子细胞通过生殖道时的膜特性，这可能会影响它们的抗冷冻性。最近的研究表明，小反刍动物精子细胞中的水通道蛋白的表达也可能与与雄激素相关的精子抗冷冻性季节性变化有关。除了附睾和射出的精子之外，睾丸组织的冷冻保存也可以为雄性配子提供合适的来源，当由于任何原因无法收集精液时，这可以成为建立种质库的替代方法。
