Nerve growth factor from seminal plasma origin (spβ-NGF) increases CL vascularization and level of mRNA expression of steroidogenic enzymes during the early stage of Corpus Luteum development in llamas

The objectives of the study were to determine the effect of seminal plasma β-NGF on Corpus Luteum morphology and function and level of mRNA expression of steroidogenic enzymes. Llamas were assigned (n = 12/per group) to receive an intramuscular dose of: (a) 1 ml phosphate buffered saline (PBS), (b) 5 μg gonadorelin acetate (GnRH), or (c) 1.0 mg of purified llama spβ-NGF. Ovaries were examined by transrectal B-mode ultrasonography from treatment to ovulation (Day 0 = treatment). B mode/Power Doppler ultrasonography and blood samples collection were performed at Days 4, 8 and 10 (n = 3 llamas per treatment group/per time point) to determine CL diameter, vascularization and plasma progesterone concentration respectively. Plasma progesterone concentration was analyzed in all llamas at Day 0. Then females were submitted to ovariectomy at Days 4, 8 and 10 (n = 3 llamas/treatment/time), CL was removed to determine vascular area, proportion of luteal cells and CYP11A1/P450scc and STAR expression by RT-PCR. Ovulation was similar between llamas treated with GnRH or spβ-NGF and CL diameter did not differ between GnRH or spβ-NGF groups by Day 4, 8 or 10. Vascularization area of the CL was higher (P < 0.01) in llamas from the spβ-NGF than GnRH-treated group by Day 4 and 8. Plasma progesterone concentration was higher (P < 0.05) in llamas from the spβ-NGF compared to females of GnRH group by Day 4 and 8. The proportion of small and large luteal cells did not differ between GnRH or spβ-NGF groups by Day 8. CYP11A1/P450scc was upregulated 3 folds at day 4 and 10 by spβ-NGF compared to GnRH. STAR transcription was 3 folds higher at day 4 in females treated with spβ-NGF. In conclusion, the luteotrophic effect of spβ-NGF could be related to an increase of vascularization and up regulation of CYP11A1/P450scc and STAR transcripts enhancing progesterone secretion.