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Embryo survival rates obtained after transfer of in vitro produced porcine blastocysts are very poor. This is probably related to poor quality of the embryos. The aim of the present study was to determine markers for good quality blastocysts. Therefore, we tried to link blastocyst morphology to several morphological and cell biological properties, and evaluated the survival of in vitro produced, morphologically classified, blastocysts following non-surgical transfer. In vitro and in vivo produced blastocysts were allocated to two groups (classes A and B) on the basis of morphological characteristics. The quality of their actin cytoskeleton, their total cell number, their ability to re-expand after cytochalasin-B treatment and the occurrence of numerical chromosome aberrations were studied and compared. In vivo produced blastocysts were used as a control. Our results indicate that the ability of blastocysts to re-expand after cytochalasin-B-induced actin depolymerization was positively correlated with the morphology of the blastocyst, and associated with the quality of the actin cytoskeleton. Chromosome analysis revealed that mosaicism is inherent to the in vitro production of porcine embryos, but also that in vivo produced blastocysts contained some non-diploid cells. In non-surgical embryo transfer experiments more recipients receiving class A blastocysts were pregnant on Day 20 than those receiving class B blastocysts. One recipient gave birth to six piglets from class A in vitro produced blastocysts, providing a verification of the enhanced viability of blastocysts that were scored as 'good' on the basis of their morphology.

Bone morphogenetic proteins (BMPs) have been implicated in the regulation of ovarian follicular development and are promising candidates to apply in IVM and IVF protocols. We investigated the expression of BMP2, BMP4 and BMP receptors in bovine ovaries and the effects of BMP2 and BMP4 during oocyte maturation on bovine IVM. Reverse transcription polymerase chain reaction studies with antral follicles showed the expression of BMPR-IA, BMPR-IB, ActR-IA, ActR-IIB, BMPR-II and BMP4 mRNA in all follicular compartments, while BMP2 mRNA was generally restricted to theca and cumulus tissue. Immunohistochemistry demonstrated the presence of BMPR-II in oocytes and granulosa cells of preantral follicles but only in oocytes of antral follicles. The immunostaining of BMP2 and BMP4 was limited to theca interna and approximately 25% of oocytes of antral follicles. Exogenously added BMP2 or BMP4 to IVM medium did not affect oocyte nuclear maturation, cumulus cell expansion, nor blastocyst formation following IVF. It is concluded that a BMP-signaling system, consisting of BMP2, BMP4, type II and I receptors, is present in bovine antral follicles and that this system plays a role in development and functioning of these follicles rather than in final oocyte maturation and cumulus expansion.