The two-step process of ovarian follicular growth and maturation in mammals can be compared to a fruit ripening where quality depends on the second step

In human IVF, the main uncertainty factor impacting on success is oocyte quality, which largely depends on the follicular status at the time of collection. Decades of debate ensued to find the perfect stimulation protocol demonstrated the complexity of the ovarian response to exogenous gonadotropins and the dynamic nature of late folliculogenesis. Although several follicular markers, proteins, RNA from granulosa cells or microRNA and follicular fluid metabolites have been associated with outcome, the possibility to influence them during stimulation remains elusive. The heterogeneity of the follicle’s maturity following control ovarian stimulation is also an important factor to explain average poor oocyte quality still observed today. In this review, the analogy between the apple ripening on the tree and follicular development is presented to focus the attention on a biphasic process: growth and differentiation. The molecular analysis of the progressive follicular differentiation indicates 2 competing phenomena: growth and differentiation where a delicate balance must operate from one to the other to ensure proper maturity at ovulation. As long as FSH stimulates growth, follicles remain green, and it is only when FSH is replaced by LH that the ripening process begins, and “apples” become red. Both fruits, follicles and apples, depend on a perfect timing of events to generate offspring.

ТРАНСВАГИНАЛЬНАЯ АСПИРАЦИЯ ФОЛЛИКУЛОВ И СПОСОБНОСТЬ OPU-ООЦИТОВ КОРОВ К ЭМБРИОНАЛЬНОМУ РАЗВИТИЮ В УСЛОВИЯХ IN VITRO

Представлены результаты трансвагинальной аспирации ооцитов коров, а также оценен их потенциал к эмбриональному развитию после оплодотворения в условиях in vitro. Донорами яйцеклеток являлись половозрелые телки симментальской породы в возрасте 1619 мес. Животныедоноры (n7) перед проведением процедуры Ovum Pickup (OPU) были гормонально обработаны с целью стимуляции роста фолликулов. Количество выделенных ооцитов от индивидуальных доноров составило в среднем 7,7 ооциткумулюсных комплексов (ОКК), что соответствовало степени извлечения 54,57,7. Доля ОКК хорошего качества, рассчитанная от общего числа извлеченных ОКК, между отдельными животными существенно не различалась (значения варьировали от 60,0 до 75,0) и в среднем составила 67,21,9. ОКК с признаками нормальной морфологии подвергали in vitro процедурам созревания, оплодотворения и последующего культивирования до стадии бластоцисты. Доля раздробившихся ооцитов и выход бластоцист после in vitro осеменения яйцеклеток коров равнялась 75,7 и 24,3, соответственно. В целом от одного донора за сессию OPU было получено 1,3 эмбриона на стадии бластоцисты, содержащих в среднем 89,8 ядра. Оцененный способ экстракорпорального оплодотворения OPUооцитов коров позволяет получать эмбрионы, пригодные для замораживания и трансплантации реципиентам и может быть использован в программах по воспроизводству желаемых генотипов у крупного рогатого скота.In the present work, we report the data on transvaginal aspiration of bovine ovarian follicles and estimation of in vitro embryo development competence of collected oocytes. The oocytes were collected by ovum pickup OPU from seven 1619 monthold Simmental heifers, previously hormonallytreated in order to stimulate ovarian follicular growth. In average, 7.7 oocytecumulus complexes (OCCs) per heifer per OPU session were collected that corresponded to 54.57.7 of recovery rate. Morphologically, 60.075.0 of OCCs were the good quality and this rate did not significantly differ between the animals. Good quality OCCs (total n37) were then subjected to in vitro maturation, in vitro fertilization and in vitro embryo development up to blastocyst stage. Cleavage and blastocyst rates were 75.7 и 24.3 , respectively. In total, 1.3 blastocysts were obtained per cow per OPU session in average these blastocysts contained 89.9 cells. In conclusion, we developed the methodology of in vitro fertilization of bovine OPUcollected oocytes that allowed obtaining the blastocysts potentially suitable for freezing and transplantation to recipients. This approach can be used to multiply desired genotypes in cattle reproduction.

Practical application of laparoscopic oviductal artificial insemination for the propagation of domestic cats and wild felids

AI was first reported in cats almost 50 years ago but, unlike AI in other domesticated animals (e.g. dogs, cattle, horses), has not been widely used for routine propagation by veterinarians or breeders. Anatomical and physiological challenges with cats have hindered the efficiency of AI using standardised transcervical approaches applied to other species. Development of laparoscopic oviductal AI (LO-AI) has helped overcome some of these barriers and, during the past 7 years, produced high pregnancy percentages (>70%) in domestic cats using both fresh collected and frozen–thawed semen and resulted in the birth of full-term offspring in three cat hereditary disease models and six wild cat species (ocelot, Pallas’s cat, fishing cat, sand cat, tiger, clouded leopard). The standard approach involves exogenous gonadotrophin treatment (typically equine chorionic gonadotrophin followed by porcine LH) to induce ovarian follicular growth and ovulation, with laparoscopic visualisation of the oviductal ostium for direct intraluminal insemination with low numbers of spermatozoa. Similar ovarian synchronisation and insemination approaches have been used with wild felids, but frequently must be refined on a species-by-species basis. From a practical perspective, LO-AI in domestic cats now has adequate efficiency for applied use as a reproductive service in veterinary practices that possess basic laparoscopy expertise.

CYTOMORPHOLOGICAL RESEARCH OTSYT-CUMULUS COMPLEXES RABBIT FROM WITH OVARIAN AT DIFFERENT STAGES OF THE ESTROUS CYCLE

The analysis of the research results revealed that the largest number (86.4%) of oocytes suitable for further development outside the body can be obtained with ovarian follicular phase of growth. It should be noted that statistically significant difference was observed between the groups OCC rabbit derived from ovaries at different phases of the estrous cycle by the number oocytes unsuitable for further cultivation. Thus, the phase of the ovarian follicular growth of gametes was obtained only 13.6% of ovarian and with signs of ovulation and the luteal phase, 35.4% and 31.4% respectively. When comparing the results of the analysis of cytogenetic preparations oocytes from ovaries removed rabbit at different stages of the estrous cycle, found that regardless of the phase of the estrous cycle Yachnik mostly larger number of oocytes were under dyploteny. The largest number of gametes with diffuse chromatin at the stage dyploteny (37.3%) received from the stage ovarian follicular growth. At the stage of fibrillar dyploteny increasing number of gametes was removed from ovarian luteal phase of the estrous cycle. In step dyploteny visible bivalent were more likely gametes obtained from stage ovarian follicular growth (18,1%, p <0,05). The highest percentage of oocytes degeneration chromatin was observed in the group removed from the ovaries to the rabbit lyutealniy phase (21.6%).