Spatial distribution of preantral follicles in the equine ovary

Abstract

Comprehensive studies on spatial distribution of preantral follicles in the ovary are scarce. Considering that preantral follicles represent the main ovarian reserve, harvesting of these follicles is crucial for the development/use of assisted reproductive techniques. Therefore, knowledge on follicle spatial distribution can be helpful for targeting areas with richer number of preantral follicles through biopsy procedures. The aim of this study was to assess the distribution and localization of equine preantral follicles according to: (i) age, (ii) ovarian portion (lateral and intermediary) and region (dorsal and ventral), (iii) distance from the geometric center, and (iv) follicular class. Ovaries from young and old mares (n = 8) were harvested in a slaughterhouse and submitted to histological processing for further evaluation. For data analyses, a novel methodology was developed according to the geometric center of each histological section for a precise determination of preantral follicle distribution. Results indicated that (i) equine preantral follicles are clustered and located near to the ovarian geometric center, and that aging induced their dispersion through the ovarian cortex; (ii) the distance from the geometric center was shorter for developing follicles than primordial; and (iii) secondary follicles were more distant from the geometric center but closer to the ovulation fossa. In conclusion, the spatial distribution of preantral follicles was successfully determined in the equine ovary and was affected by age, region, and portion.

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

“…The use of heterotopic autotransplantation and xenotransplantation in livestock may become a powerful tool for (1) treatment of infertility caused by ovarian abnormalities (e.g., benign tumors and adhesions) and oviductal and uterine disorders, and (2) making easier the recovery of immature or mature oocytes from females of high genetic value that need preservation. In the area of preantral follicle research in horses, several studies have been conducted recently on ovarian tissue storage and cryopreservation [12][13][14], in vitro follicle culture [15,16], and preantral follicle population, addressing aspects related to aging effect [17], follicular dynamics [11], and spatial follicle distribution [18].…”

Preantral follicle population and distribution in the horse ovary

“…(F, G, I, and J) Scale bars = 100 µm, magnification = ×200; and (H and K) scale bars = 50 µm, magnification = ×400. (A–E) Diagrams adapted from Alves et al (2018) . …”

“…The preparation of slides for determination of the spatial distribution for preantral follicles in the ovarian portions and regions was performed as previously described ( Alves et al 2018 ):…”

“…2011 ; cow: Silva-Santos et al 2011 ; ewe: Fransolet et al 2014 ; doe: Brandão et al 2018 ; deer: Gastal et al 2017 b ; mouse: Dath et al 2010 , Malki et al 2015 ). This follicular heterogeneity and variation can be explained by the dynamic ovarian plasticity that has been suggested to occur in women and mares ( Woodruff & Shea 2011 , Alves et al . 2018 ).…”

“…2018 ). In fact, Alves et al (2018) evaluated ovarian portions (lateral and intermediary) and regions (dorsal and ventral) in detail, considering the spatial distribution of preantral follicles according to mare age and follicle class. However, the morphology of preantral follicles across the whole ovary in different regions and portions according to mare age has not been evaluated.…”