Difference in Expression Profile of Compact and Expanded-Type Equine Cumulus-Oocyte-Complexes

Abstract

Background: Typically, 60% of oocytes recovered from equine follicles are with expanded cumuli, 30% are with compact cumuli, and 10% are degenerated. Studies have proved that equine oocytes with expanded cumuli (Ex COCs) and oocytes with compact cumuli (Cp COCs) are of different developmental competence and therefore, need different maturation time in vitro. To better understand the gap in developmental competence, we compared the expression of some growth factors and hormone-related genes in Ex COCs and Cp COCs. Methods: We tested the expression of some hormones and growth factors in Ex- and Cp-COCs by qPCR and immunofluorescence, and the influence of the growth factors and hormones on equine IVM. Results: As a result, we found that the expression patterns of FSHR, LHR,IGF1R, IGF2R, ESR1, ESR2, BMPR1, BMPR2, and ALK5 are different in two types of COCs and among BMP15, GDF9, Estrogen, and IGF2, the addition of Estrogen and IGF2 are beneficial to equine IVM. Conclusions: This study indicates that the differential expression pattern of growth factors and hormone-related genes might be responsible for the difference in developmental capacity of two types of COCs. This work provides clues for improving the equine IVM system.