The Effect of Oviductal Epithelial or Granulosa Cells Monolayer Used during Maturation Culture on the In Vitro Maturation and Fertilization of Porcine Oocytes

Abstract

We evaluated the effect of two monolayers derived from reproductive cells on in vitro maturation and fertilization of porcine oocytes. Cumulus-oocyte complexes were cultured in medium alone or co-cultured for 48hr on the monolayer of porcine oviductal epithelial cells (pOEC) or granulosa cells (pGC). Assessment of nuclear maturation revealed that oocytes matured in pGC significantly reached metaphase of the second meiotic division compared to those in control (76% vs 55%; p<0.05) and did not differ from the pOEC (69%). Following 18hr of insemination, the proportion of penetrated oocytes in control (82%) was greater (p<0.01) compared with pGC (56%) but did not differ from the pOEC (68%). The proportion of oocytes that underwent polyspermy was lower (p<0.01) in pOEC (38%) and pGC (46%) compared to control (79%). More number of male pronuclei were formed in the oocytes matured on pOEC than pGC (37% vs 19%; p<0.05). There was no difference between pOEC and control (28%). In all groups, irrespective of immature or mature stage, some oocytes at germinal vesicle stage formed a male pronucleus within their cytoplasm. It was suggested that the monolayer of pGC or pOEC was effective for preventing oocytes from polyspermy and that the monolayers from pOEC were superior for promoting male pronuclear formation by increasing monospermy. That immature oocytes may also have an ability to form a male pronucleus in their cytoplasm was indicated.