Addition of lysophosphatidic acid to mouse oocyte maturation media can enhance fertilization and developmental competence

Study question: Does exposure to lysophosphatidic acid (LPA) during in vitro maturation (IVM) enhance the maturation and developmental competence of mouse oocytes?

Summary answer: Supplementation of IVM medium with 30 μM LPA enhanced the developmental competence of in vitro matured oocytes and so made them more comparable to in vivo matured control oocytes.

What is known already: LPA is a small phospholipid that acts as an extracellular signaling molecule by binding to and activating at least five G protein-coupled receptors. LPA has various biological actions, with both developmental and physiological effects.

Study design, size, duration: During IVM, LPA at six different doses (0, 1, 10, 30, 50 or 100 μM) was added into the TCM-199 medium. After maturation, the developmental competence and other parameters of the oocytes were assessed.

Participants/materials, setting, methods: Immature GV stage oocytes from 5- to 6-week-old female BDF-1 mice were incubated for 17-18 h in IVM medium containing 0, 1, 10 or 30 μM LPA and then either fertilized in vitro with epididymal sperm, or assessed for spindle morphology, mitochondrial membrane potential (ΔΨm) or the mRNA expression of a meiotic checkpoint gene (Mad2), a microtubule structure gene (Hook1), two maternally derived genes (Mater and Hsf1) and an apoptosis-related gene (Caspase6). The fertilized embryos were grown in vitro to assess blastocyst-formation rates, differential cell counts and apoptosis.

Main results and the role of chance: Rates of maturation, fertilization and blastocyst formation and hatching were significantly higher in the 30 μM LPA-supplemented group (94.3, 96.3, 79.1 and 51.3%, respectively) than in the unsupplemented control (0 μM) group (80.5, 87.5, 61.3 and 37.8%, respectively) and more comparable to that of the in vivo matured oocytes (100, 96.5, 95.3 and 92.9%, respectively). LPA did not adversely affect mitochondrial activity, spindle integrity, blastocyst cell number, caspase positivity or Mad2 expression. Oocytes matured in 30 μM LPA had reduced Caspase6 expression, but Hook1, Mater and Hsf1 were up-regulated in all of the LPA-supplemented groups.

Limitations, reasons for caution: Chromosomal aneuploidy in the resultant blastocysts and the production of normal pups were not assessed. Only mouse oocytes were assessed.

Wider implications of the findings: Supplementation of IVM medium with 30 μM LPA may enhance the developmental competence of mouse oocytes without affecting apoptosis, spindle normalcy or mitochondrial integrity.

Study funding/competing interest(s): This study was supported by a research grant (02-2012-021) from the Seoul National University Bundang Hospital. The authors declare that they have no competing interests.