Calanni-Pileri Michela, Weitzel Joachim M, Langhammer Martina, Michaelis Marten
Institute of Reproductive Biology, Research Institute for Farm Animal Biology (FBN), Dummerstorf, Germany.
Institute of Genetics and Biometry, Service Group Lab Animal Facility, Research Institute for Farm Animal Biology (FBN), Dummerstorf, Germany.
Reprod Domest Anim. 2022 Oct;57(10):1198-1207. doi: 10.1111/rda.14194. Epub 2022 Jul 5.
Dummerstorf fertility lines FL1 and FL2 represent two models of enhanced fertility characterized by the doubling of the litter size compared with an unselected control population (ctrl line, Dummerstorf FztDU). Both biodiverse FLs managed to reach this goal by increasing the ovulation rate per cycle, even showing decreased pregnancy rate and irregular oestrous cycle and metabolic hormone levels, compared with ctrl. The aim of the present study was to analyse oocytes in terms of quality and quantity by comparing the entire pool of oocytes per ovary, with those from the antral follicles within the same animal. We performed Brilliant Cresyl Blue staining as a non-invasive marker of oocyte quality in combination with an analysis of additional morphological indicators, e.g. cytoplasm clarity, cumulus cell layers, nuclear anatomy, size and shape. We compared our fertility lines with the unselected control population and with another independent line selected from the same founder population, showing lower litter size (DU6P). Our results suggest that fertility lines show decreased number of oocytes per ovary compared with DU6P but increased number of high-quality oocytes before ovulation. Hence, the raise in the ovulation rate and litter size of those super fertile mouse lines are not associated with an increased number of oocytes per ovary but rather with an increased number of higher quality fertilizable oocytes per cycle. In addition, the most conspicuous method to acquire oocytes with the highest quality in our lines is to assess their morphology, rather than their status after staining. All these discoveries together may be of fundamental importance for further studies in livestock farm animals showing some similar characteristics, e.g. irregular cycle or hormonal misbalances, to improve production while lowering costs, and in humans to increase the possibilities of successful pregnancies for couples undergoing in vitro fertilization (IVF).
达姆施托夫生育系FL1和FL2代表了两种生育能力增强的模型，其特征是与未选择的对照群体（对照系，达姆施托夫FztDU）相比，窝产仔数增加了一倍。与对照相比，这两个生物多样性的FL系均通过提高每个周期的排卵率实现了这一目标，甚至出现了妊娠率降低、发情周期不规律以及代谢激素水平下降的情况。本研究的目的是通过比较每个卵巢的全部卵母细胞与同一动物窦卵泡中的卵母细胞，从质量和数量方面分析卵母细胞。我们进行了灿烂甲酚蓝染色，作为卵母细胞质量的非侵入性标记，并结合对其他形态学指标的分析，例如细胞质清晰度、卵丘细胞层数、核结构、大小和形状。我们将我们的生育系与未选择的对照群体以及从同一创始群体中选出的另一个窝产仔数较低的独立系（DU6P）进行了比较。我们的结果表明，与DU6P相比，生育系每个卵巢的卵母细胞数量减少，但排卵前高质量卵母细胞数量增加。因此，那些超高生育力小鼠系的排卵率和窝产仔数的提高与每个卵巢卵母细胞数量的增加无关，而是与每个周期中可受精的高质量卵母细胞数量的增加有关。此外，在我们的品系中获取最高质量卵母细胞最显著的方法是评估其形态，而不是染色后的状态。所有这些发现对于进一步研究具有一些相似特征（例如周期不规律或激素失衡）的家畜农场动物可能至关重要，以便在降低成本的同时提高产量，对于人类而言，则有助于增加接受体外受精（IVF）的夫妇成功怀孕的可能性。
