Occurrence and characteristics of residual follicles formed after transvaginal ultrasound-guided follicle aspiration in cattle

Abstract

Ultrasound-guided transvaginal follicle aspiration is used to recover cumulus-oocyte complexes (for IVF) and to synchronize follicular wave emergence (ablation of dominant follicle). Although aspirated follicles are generally supposed to undergo immediate atresia, there are indications that they may remain active. The objective was to evaluate the occurrence and characteristics of residual follicles (RF) after transvaginal follicle aspiration in cattle. Ovarian follicular wave emergence was synchronized in Holstein cows (N = 13) in the presence (groups 1 and 3) or absence (groups 2 and 4) of norgestomet implants. The largest follicle was aspirated at a diameter of 8 mm (groups 1 and 2) or 12 mm (groups 3 and 4). Ovarian follicles were visualized (transrectal ultrasonography) every 12 h after wave emergence. Follicular fluid samples were collected from the largest follicle and from the ensuing RF and concentrations of estradiol and progesterone were determined. After aspiration, 73.2% (52/71) of the follicles refilled with fluid, and a new antrum was detected 12 to 24 h later. Norgestomet did not affect (P > 0.05) RF occurrence or diameter, but in RF from group 4, concentrations of estradiol decreased (-530.7 ± 133.9 ng/mL; P < 0.01) whereas progesterone increased (+429.6 ± 171.7 ng/mL; P < 0.05) relative to preaspiration. In RF, there were three steroidogenesis patterns: (1) high estradiol concentration and high estradiol:progesterone ratio (estradiol-active RF); (2) low estradiol, but high progesterone concentrations (luteinized RF); and (3) low estradiol and low progesterone concentrations (inactive RF). Estradiol-active RF were more likely (P < 0.05) from follicles with high estradiol concentrations (regardless of diameter). In conclusion, fluid-filled structures (RF) with variable steroid production patterns are frequently formed after ultrasound-guided follicle aspiration. The occurrence and features of these RF depended on the diameter and status of these follicles before aspiration.

In vivo collection of follicular fluid and granulosa cells from individual follicles of different diameters in cattle by an adapted ovum pick-up system

“…The intrafollicular concentrations of estradiol and progesterone were determined by solid-phase I 125 radioimmunoassay (RIA), using commercial RIA kits (TKE22 Coat-A-Count Estradiol and TKPG5 Coat-A-Count Progesterone, Siemens Healthcare Diagnostics Inc., Tarrytown, NY, USA), as described previously [30]. …”

Characterization of blood flow and the effects of exogenous estradiol benzoate on residual follicles formed after ultrasound-guided transvaginal follicle aspiration in cattle

“…Intrafollicular concentrations of E2 and P4 in the FF and in the content of RF were determined by solid-phase I 125 RIA, using commercial RIA kits (TKE22 Coat-A-Count Estradiol and TKPG5 Coat-A-Count Progesterone, Siemens Healthcare Diagnostics Inc., Tarrytown, NY, USA) at the Endocrinology Laboratory of the College of Veterinary Medicine and Animal Sciences, São Paulo State University (UNESP), Botucatu, SP, Brazil, following procedures described previously [ 13 ]. If necessary, samples were diluted 1:1 to 1:1,000 to fit the standard curves.…”

“…These strategies are based on the assumption that aspirated follicles will undergo atresia after removal of the fluidic content and collapse. However, previous studies from our and other groups reported that the follicle wall may remain functional after being aspirated, forming a fluid-filled antrum which eventually persist as a steroidogenically-active structure [ 12 , 13 ]. These were referred to as residual follicles (RF) and their occurrence is more frequent after aspiration of large follicles, i.e., follicles likely to have greater intrafollicular estradiol (E 2 ) concentrations [ 13 ].…”

“…However, previous studies from our and other groups reported that the follicle wall may remain functional after being aspirated, forming a fluid-filled antrum which eventually persist as a steroidogenically-active structure [ 12 , 13 ]. These were referred to as residual follicles (RF) and their occurrence is more frequent after aspiration of large follicles, i.e., follicles likely to have greater intrafollicular estradiol (E 2 ) concentrations [ 13 ]. Thus, the presence of RF may disturb the expected results of any procedures performed after follicle ablation by TVFA, such as follicular wave synchronization and/or superovulation.…”

Biomedical Applications of Ovarian Transvaginal Ultrasonography in Cattle

“…Although application of OTU for the aspiration of ovarian follicles can induce changes in reproductive hormone profiles (88)(89)(90)(91), follicular growth (92), and alter the length of the estrous cycle (93), the reproductive performance after termination of follicular aspirations is usually unaffected (3,76,94,95). Nevertheless, there is evidence indicating the formation of ''residual follicles'' (i.e., follicles that refilled with fluid after follicular aspiration) following OPU, which could result in the formation of follicular cysts or impaired follicular growth (96).…”