Supplementation with cumulus cell masses improves the in vitro meiotic competence of porcine cumulus–oocytes complexes derived from small follicles

Abstract

The present study was conducted to examine the supplemented effect of cumulus cell masses (CCMs) derived from middle follicle (MF; 3-6 mm diameter) on the morphology and the meiotic or developmental competence of oocytes from small follicles (SF; 1-2 mm diameter). The number of cumulus cells surrounding oocytes just after collection was also lower in cumulus-oocyte complexes (COCs) from SF than MF. The ooplasmic diameter of oocytes was significantly smaller in SF-derived oocytes than MF-derived ones before and after in vitro maturation (IVM), whereas the diameter significantly increased during the culture. Co-culture of SF-derived COCs with MF-derived CCMs during IVM significantly improved the meiotic competence of the oocytes to the metaphase-II stage. Furthermore, the ooplasmic diameter of SF-derived COCs during IVM was increased to the similar size of MF-derived those in the presence of MF-derived CCMs. The abilities of oocytes to be penetrated, to form male pronuclear formation and to cleave or develop to the blastocyst stage were not affected by the co-culture with CCMs. Electrophoretic analysis of CCM secretions clearly showed the presence of more protein(s) approximately 27.6 kDa in the conditioned medium when supplemented with MF-derived CCMs. In conclusion, we demonstrate that supplementation with MF-derived CCMs improves the ooplasmic diameter and meiotic competence of SF-derived oocytes.

The autophagic inducer and inhibitor display different activities on the meiotic and developmental competencies of porcine oocytes derived from small and medium follicles

“…The meiotic and developmental competencies of oocytes are acquired gradually through communication between oocytes and surrounding somatic cells [26]. Factors secreted from oocytes, such as bone morphogenetic protein 15 and growth and differentiation factor 9 [26,27,28], and surrounding cumulus cells, such as vascular endothelial growth factor [6, 29], have been known to promote the meiotic and developmental competencies. Since the presence of rapamycin during IVM culture improved the developmental competence of MF-derived oocytes surrounded by poor cumulus cells [30], the ability of oocytes to regulate autophagic activity through mTOR signaling pathway would readily reflect the competence.…”

“…However, the number of MF on the surface of porcine ovaries is significantly lower than that of small-sized antral follicles with a diameter of less than 2 mm (small follicles; SF) [4]. In addition, the diameter of oocytes [5], as well as the number of surrounding cumulus cells [6], is significantly smaller in SF-derived oocytes than in MF-derived oocytes. Furthermore, it is well known that the meiotic and developmental competencies are lower in oocytes derived from SF than MF [7,8,9], whereas the in vitro ability of sperm to penetrate MF- and SF-derived oocytes to form male and female pronuclei were similar when mature oocytes with the first polar body were inseminated following in vitro maturation (IVM) [9].…”

Removal of cumulus cells around 20 h after the start of <i>in vitro</i> maturation improves the meiotic competence of porcine oocytes via reduction in cAMP and cGMP levels

“…The developmental competence of oocytes appears to be acquired during the final process of follicular development through an interaction with their companion somatic cells [20]. We have shown that the number of cumulus cells surrounding an SF-derived oocyte was significantly lower than a MF-derived oocytes and that supplementation of the IVM media with a cumulus cell mass significantly improved both the ooplasmic diameter and the meiotic competence of the oocytes to reach the metaphase-II stage following IVM [21]. We have also suggested that differences in the levels of vascular endothelial growth factor secreted from cumulus cells reflects the meiotic and developmental competences of SF-derived porcine oocytes and supplementation of IVM medium with vascular endothelial growth factor improves their competence [19].…”