9-cis-retinoic acid during in vitro maturation improves development of the bovine oocyte and increases midkine but not IGF-I expression in cumulus-granulosa cells

The isomer 9‐cis of retinoic acid (9‐cis‐RA) exerts a beneficial effect on bovine in vitro development when added to in vitro maturation (IVM) culture. In the present work, 9‐cis‐RA 5 nM was found to be stimulatory as opposed to 500 nM (toxic). Cumulus–oocyte complexes (COCs) were treated with the found physiological dose 9‐cis‐RA 5 nM, and the next determinations performed: (1) relative expression of midkine (MK) and IGF‐I, by reverse transcriptase‐polymerase chain reaction (RT‐PCR), in cumulus‐granulosa cells detached from oocytes; (2) cytoplasmic granular migration, by labeling of oocytes with fluoroscein isothiocyanate lectins; and (3) in vitro survival of blastocysts after vitrification and warming. Gene expression of MK was enhanced by 9‐cis‐RA, but not by 1% ethanol (vehicle). However, we did not detect IGF‐I expression, both in dependence on or in the absence of 9‐cis‐RA acting on cumulus‐granulosa cells. The ability of vitrified blastocysts to survive in vitro was not improved by 9‐cis‐RA. Nevertheless, since only blastocysts obtained from oocytes matured with serum survived, more factors should be considered when evaluating cryopreservation survival. The complete granular migration observed in oocytes matured with 9‐cis‐RA anticipates the gain in developmental competence of the oocyte, being MK probably involved in this beneficial effect. Mol. Reprod. Dev. 66: 247–255, 2003. © 2003 Wiley‐Liss, Inc.