The aim of the present study was to assess the effects of L-carnitine, an enhancer of lipid metabolism and mitochondrial activity, during in vitro maturation (IVM) on nuclear maturation and in vitro fertilisation of porcine follicular oocytes and subsequent embryo development. Mitochondrial functions, intracellular lipid content and reactive oxygen species (ROS) levels in oocytes were also investigated. L-carnitine supplementation in 0.6-5mgmL(-1) concentration during IVM significantly improved (P<0.05) the rates of metaphase-II (MII) stage oocytes compared with the control; however, fertilisation rates and monospermy were not improved. Although supplementation of IVM medium with L-carnitine significantly increased oocyte cleavage (P<0.05), further development to the blastocyst stage was not improved. The density of active mitochondria was significantly higher and the density of lipid droplets was significantly lower (P<0.05) in L-carnitine-treated oocytes compared with the control. Furthermore, the ROS levels in L-carnitine-treated oocytes were significantly lower than those in the control. In conclusion, enhancing mitochondrial functions by L-carnitine improved oocyte maturation and cleavage underlining the importance of lipid metabolism for nuclear and cytoplasmic maturation of porcine oocytes.

Abstract.The following selection markers for in vitro-produced porcine embryos were investigated: the timing, pattern and evenness of the first cleavage and the timing of the second cleavage. The embryos that cleaved by 30 h postinsemination (hpi) developed to blastocysts at a significantly higher rate (60.9%) and with a significantly higher cell number (33.6 cells) than those of embryos cleaved by 36 hpi (26.4% and 23.6 cells, respectively, P<0.05). Blastocyst proportions derived from 2-and 3-cell embryos cleaved by 30 hpi (68.2 and 65.3%, respectively) were significantly higher than those of 4-and >4-cell embryos (46.3 and 42.6%, respectively, P<0.05). The cell number per blastocyst generated from 2-cell embryos was significantly greater (37.3 cells) than those from 3-, 4-and >4-cell embryos (23.6-27.8 cells, P<0.05). Among embryos cleaved by 30 hpi, the blastocysts derived from evenly cleaved embryos (40.6 cells) were of significantly better quality than those derived from unevenly cleaved embryos (33.2 cells, P<0.05), although their blastocyst rates did not differ. The evenly cleaved embryos that underwent subsequent cleavage within 18 h had significantly higher blastocyst rates (72.7-81.0%) and quality (36.2-40.9 cells) than those without subsequent cleavage (48.3% and 22.5 cells, respectively, P<0.05) during the same period. In conclusion, the timing, pattern and evenness of the first cleavage and the timing of the second cleavage affected the developmental competence and quality of in vitroproduced porcine embryos. Key words: Cell division, Early stage, Embryo morphology, In vitro fertilization, Pig (J. Reprod. Dev. 56: [593][594][595][596][597][598][599][600] 2010) he developmental competence of porcine embryos produced in vitro after in vitro maturation (IVM), fertilization (IVF) and culture (IVC) for a short period has been confirmed [1,2]. Birth of piglets has been accomplished from IVM-IVF embryos after IVC to the 2-to 4-cell stages [3][4][5] or 8-cell to morula stage [6]. Although transfer of in vitro-produced (IVP) blastocysts has also led to pregnancies and live births [7][8][9], utilization of early IVP embryos for transfer remains preferable because the viability of IVP porcine embryos is decreased by IVC after IVF [10]. High oxygen tension, imperfect culture media and polyspermy are thought to reduce the developmental competence of IVP porcine embryos [11]. Thus, large numbers of early-stage IVP embryos should be transferred to recipients to ensure multiple pregnancies.For the success of embryo transfer (ET) programs, selection of high-quality embryos for ET and elimination of those with low developmental competence at early stages are key factors [12,13]. To achieve this goal, transfer of cleavage stage embryos chosen by an effective embryo selection system is necessary. The timing of the first cleavage and cleavage evenness are among the most frequently used morphological criteria for choosing good quality embryos for ET. Studies in cattle [14], humans [15], mice [16] and pigs [13,17] have...

The pig is considered to be a suitable source of cells and organs for xenotransplants, as well as a transgenic animal to produce specific proteins, given the biological similarities it shares with human beings. However, the in vitro embryo production system in pigs is inefficient compared with those in other mammals, such as cattle or mice. Although numerous modifications have been applied to improve the efficiency of in vitro embryo production systems in pigs, not much progress has been made to overcome the problem of polyspermy, and low developmental ability due to insufficient cytoplasmic abilities of in vitro matured oocytes and improper culture conditions for the in vitro produced embryos. Recent achievements, such as the establishment of chemically defined medium and utilization of 'zona hardening' technique, have gained some success. However, further research for the reduction of polyspermy and detrimental effects of the culture systems in pigs is still needed.