Measurement of the Respiratory Activity of Single Human Embryos by Scanning Electrochemical Microscopy

Abstract

Respiration is useful parameter for evaluating embryo quality as it provides important information about metabolic activity. In the present study, we employed scanning electrochemical microscopy (SECM) to accurately determine the oxygen consumption of single, identical human embryos at different developmental stages. The oxygen consumption rates of single embryos were low at 2-8-cell stages (0.51 ±0.05 X 1014/mol • s-1, n=l8) but increased by the morula (0.61 ±0.11 X 1014 /mol· s-1, n=5) and early blastocyst(0.72±0.06 X 1014/mol • s-1, n=14) stages. Later blastocysts exhibited even higher oxygen consumption rates (1.00±0.19 X 1014/mol • s-1 n=4). Ultrastructural studies revealed that most mitochondria in embryos up to the 8-cell stage were immature and had a spherical or ovoid shape. However, by the morula stage, the mitochondria had elongated cristae, with the elongated morphology even more pronounced in mitochondria present in blastocysts. The maturation of mitochondria correlated with the increase of oxygen consumption rate during the development of embryos. The SECM technique may be a valuable tool for accurately assessing the mitochondrial function and quality of human embryos.