Ovarian and Uterine Dynamics During the Estrous Cycle in Criollo Breed Mares.

After having been brought to America 400 years ago, the Criollo horse reproduced freely for centuries in the southern part of the American continent. Roughness, resistance, and endurance are typical characteristics of this breed of horses. Although the natural selection that occurred over the centuries may have positively influenced the fertility and longevity of this breed, information regarding ovarian function and other reproductive aspects of Criollo breed mares under natural or controlled management conditions is scarce. The objectives of the present study were to (1) characterize the follicular dynamics of Criollo breed mares, (2) characterize growth and regression of the corpus luteum, and (3) study the cervical and uterine tone and ultrasonographic echotexture changes during two consecutive estrous cycles. In this study, 26 interovulatory intervals (IOI) were evaluated in 13 mares. Spontaneous estrous cycles were characterized by the following: (1) the IOI length was 21 days; (2) dominant and subordinate follicles emerged together at day 5 (ovulation = day 0), and their growth rates were slower until the day of deviation; (3) the deviation in growth rates between the two largest follicles of the ovulatory wave occurred when the dominant and subordinate follicles reached 22 and 21 mm in diameter, respectively; (4) the mean diameter of the preovulatory follicle at the day before ovulation was 43 mm; (5) different combinations of follicular waves were observed in each interovulatory interval; (6) the corpus luteum reached its maximum diameter about 2 days after ovulation and decreased gradually afterward; (7) after ovulation, the cervical and uterine tones were positively correlated and remained elevated until the onset of the expected luteolysis (days 12-14); and (8) after the expected luteolysis, the endometrial echotexture started to increase and reached maximum values 5-3 days before ovulation, when it started to decrease. Moderate-to-strong positive correlations between IOIs revealed repeatability within animals for the diameter of the preovulatory follicle at maximum and at the day before ovulation, cervical and uterine tones, endometrial echotexture, and corpus luteum diameter. The findings herein presented are of fundamental importance for a better understanding of the reproductive physiological patterns of the estrous cycle in the Criollo breed mare.

Heterotopic autotransplantation of ovarian tissue in a large animal model: Effects of cooling and VEGF.

Heterotopic and orthotopic ovarian tissue autotransplantation techniques, currently used in humans, will become promising alternative methods for fertility preservation in domestic and wild animals. Thus, this study describes for the first time the efficiency of a heterotopic ovarian tissue autotransplantation technique in a large livestock species (i.e., horses) after ovarian fragments were exposed or not to a cooling process (4°C/24 h) and/or VEGF before grafting. Ovarian fragments were collected in vivo via an ultrasound-guided biopsy pick-up method and surgically autografted in a subcutaneous site in both sides of the neck in each mare. The blood flow perfusion at the transplantation site was monitored at days 2, 4, 6, and 7 post-grafting using color-Doppler ultrasonography. Ovarian grafts were recovered 7 days post-transplantation and subjected to histological analyses. The exposure of the ovarian fragments to VEGF before grafting was not beneficial to the quality of the tissue; however, the cooling process of the fragments reduced the acute hyperemia post-grafting. Cooled grafts compared with non-cooled grafts contained similar values for normal and developing preantral follicles, vessel density, and stromal cell apoptosis; lower collagen type III fibers and follicular density; and higher stromal cell density, AgNOR, and collagen type I fibers. In conclusion, VEGF exposure before autotransplantation did not improve the quality of grafted tissues. However, cooling ovarian tissue for at least 24 h before grafting can be beneficial because satisfactory rates of follicle survival and development, stromal cell survival and proliferation, as well as vessel density, were obtained.

Central Nervous System and Vertebrae Development in Horses: a Chronological Study with Differential Temporal Expression of Nestin and GFAP.

The neural system is one of the earliest systems to develop and the last to be fully developed after birth. This study presents a detailed description of organogenesis of the central nervous system (CNS) at equine embryonic/fetal development between 19 and 115 days of pregnancy. The expression of two important biomarkers in the main structure of the nervous system responsible for neurogenesis in the adult individual, and in the choroid plexus, was demonstrated by Nestin and glial fibrillary acid protein (GFAP) co-labeling. In the 29th day of pregnancy in the undifferentiated lateral ventricle wall, the presence of many cells expressing Nestin and few expressing GFAP was observed. After the differentiation of the lateral ventricle wall zones at 60 days of pregnancy, the subventricular zone, which initially had greater number of Nestin+ cells, began to show higher numbers of GFAP+ cells at 90 days of pregnancy. A similar pattern was observed for Nestin+ and GFAP+ cells during development of the choroid plexus. This study demonstrates, for the first time, detailed chronological aspects of the equine central nervous system organogenesis associated with downregulation of Nestin and upregulation of GFAP expression.