Transcriptomic analysis of luteal tissue supports the earlier onset of luteolysis in heifers with diminished ovarian reserve

Abstract

Context Antral follicle count (AFC) is reflective of ovarian reserve and linked to reproductive performance in mammalian females. We previously demonstrated earlier upregulation of endometrial oxytocin receptor transcription in heifers with low AFC, indicating an earlier onset of luteolysis. Aims We aimed to support the earlier onset of luteolysis in non-pregnant heifers with a low number of antral ovarian follicles (Open Low AFC) and hypothesized a reduced abundance of luteinizing hormone/choriogonadotropin receptor (LH/CG-R) and increased abundance of thrombospondin-1 (THBS1) in luteal tissue of those heifers. We further investigated if classical interferon stimulated genes (ISGs) are already upregulated in response to conceptus-derived interferon tau. Methods For 4 years, 10 heifers with the highest (High AFC) and 10 heifers with the lowest AFC (Low AFC) of the population (n = 120/year) were selected, synchronized and inseminated. On day 15 or 16 after insemination, reproductive tracts were collected, and pregnancy status was determined. Corpora lutea were isolated, weighed and underwent transcriptomic analysis. Key results Transcript abundance of LH/CG-R was lower in Open Low AFC heifers compared to all other subgroups. Transcript abundance of THBS1 was upregulated in Open vs Pregnant heifers and showed greater abundance in Low vs High AFC heifers. Luteal weights and abundance of ISGs did not differ between heifers of differing AFC groups or pregnancy status. Conclusions The patterns of luteal LH/CG-R and THBS1 abundance support the concept of earlier onset of luteolysis in Open heifers with diminished AFC. Implications This may result in a shorter window for maternal recognition of pregnancy and contribute to inferior reproductive performance.