Women are delaying starting a family and as a result the age of first time mothers has increased. The number of women >40yrs using IVF reproductive technologies has also increased. However, IVF is substantially less effective for women over 40 years of age. Recent data has established that mitochondrial function in eggs from older women is reduced and levels of reactive oxygen species (ROS) are increased. The aim of this study was to establish if the addition of an antioxidant which targets mitochondrial produced ROS, can improve embryo metabolism and development using an aged mouse model.
Zygotes were collected from 22 week old superovulated C57BL6 females and cultured at 37oC in 6%CO2:5%O2:89%N2 in either (i) control media (G1) or (ii) G1 + 100µM Manganese(III) tetrakis (4 benzoic acid) porphyrin (MnTBAP) which can traverse the inner mitochondrial membrane and neutralise superoxide anions. Embryos were transferred to G2 medium before assessment for on-time blastocyst development and glucose uptake (day 4- total of 74h culture) and cell number and differentiation (day 5- total of 91h culture) and ROS production (MitoSox).
Embryos cultured in the presence of MnTBAP were significantly more advanced on day 4 with higher levels of on-time blastocyst development (control 19.5%, MnTBAP 32.7%; P<0.05) which coincided with a 12% increase in glucose uptake (P<0.05) and a significant reduction in ROS production (-25.3%; P<0.01). There was a significant increase in cell number of the blastocysts cultured with MnTBAP (control 60.5±4.6, MnTBAP 73.1±3.7; P<0.05), which is usually indicative of increased viability. This increase was confined to the oxidative trophectoderm cells (control 43.4±3.7, MnTBAP 57.3±3.3; P<0.05).
This study indicates that embryo development of embryos from older mothers can be improved by the addition of a mitochondrial antioxidant. Assessment of pregnancy outcomes from these embryos is required to further validate these findings.