Nerve Growth Factor-Beta, purified from bull seminal plasma, enhances corpus luteum formation and conceptus development in Bos taurus cows

Abstract

The objective of the current study was to determine if Nerve Growth Factor-Beta (NGF), purified from bovine seminal plasma, would improve corpus luteum function and enhance conceptus development when administered to cows at artificial insemination. Angus cows (n = 60) were synchronized using a GnRH-prostaglandin and intravaginal progesterone protocol (7-day CO-Synch/CIDR) and randomly allocated to 1 of 2 treatment groups: (1) CONT- 12 mL PBS; or (2) NGF- 296 μg purified NGF in 12 mL PBS administered intramuscularly at insemination (day 0). Blood collections were performed to measure plasma concentrations of progesterone (days 0, 3, 7, 10, 14, 19) and pregnancy-specific protein B (day 24) using immunoassays. Expression of interferon-stimulated genes (ISG15, MX1, MX2, RTP4) were assessed in peripheral blood leukocytes on day 19. Transrectal ultrasound was performed for measuring corpus luteum size (days 0, 3, 7, 10, 14, 19) and pregnancy diagnosis (days 28, 45, 66). Statistical analysis was performed using analysis of variance with repeated measures (SAS 9.4, Cary NC). Corpus luteum volume and diameter increased over time (p < 0.001), but did not differ between treatment groups (p = 0.46). Cows treated with NGF had increased plasma progesterone over CONT cows from days 10-19 (p = 0.04). Pregnancy rates at day 28 were 75% in NGF cows versus 59% in CONT cows (p = 0.13). In pregnant cows, pregnancy-specific protein B concentrations at day 24 were greater in NGF than CONT cows (p < 0.05). Additionally, fold-change expression of ISG15 and MX2 at day 19 were greater in pregnant NGF cows than in pregnant CONT cows (p < 0.05), but no differences for MX1 and RTP4 were present. Here we demonstrate that NGF administration to cows at insemination improved corpus luteum function, which translated to improved early conceptus development as determined by upregulation of interferon-stimulated genes and increased pregnancy-specific protein B concentrations. These results suggest that seminal plasma NGF could play a role in conceptus development and may be important to improve fertility in cattle.

Keywords: Corpus luteum; Interferon-tau; NGF; Progesterone; Ruminants.