Respiration rates of individual bovine in vitro-produced embryos measured with a novel, non-invasive and highly sensitive microsensor system

Abstract

Oxygen consumption is a useful parameter for evaluating embryo quality, since it provides a valuable indication of overall metabolic activity. Over the years, several approaches have been used to measure the respiration rates of individual embryos, but a convincing method has not yet been reported. In this study, we introduce and have validated a novel high resolution microsensor technology to determine the respiration rates of individual embryos at different developmental stages. We have employed this technology to investigate the correlation between respiration rate and embryo morphology, diameter and sex. Following morphological evaluation, individual respiration rates of day 3 (n 5 18) and day 7 (n 5 60) bovine in vitro-produced embryos were determined. Of the measured embryos, 64 were lysed for sex diagnosis by PCR. Average respiration rates of day 7 embryos (1.30 6 0.064 nl/h) were 3.4-fold higher than day 3 embryos (0.38 6 0.011 nl/h). On day 7, the average respiration rate of quality 1 blastocysts was significantly higher than the respiration rates of the lower qualities. For both day 3 and day 7 embryos, respiration rates were directly influenced by embryo diameter but did not differ between sexes. These results have demonstrated that the novel microsensor technology can be used to accurately and rapidly (8 min) measure the respiration rates of individual embryos at different developmental stages. Respiration rates were only in partial agreement with embryo morphology, suggesting a slight discrepancy between these two methods in assessing embryo quality. It is likely that a combined assessment of embryo respiration and morphology would improve embryo classification and subsequent selection.

Oocyte developmental failure in response to elevated nonesterified fatty acid concentrations: mechanistic insights

“…Individual zygotes day 1 p.i. were loaded into a PCR Glass micropipette (Drummond, Broomal, PA, USA) and allowed to respire for 30 min to form an oxygen gradient, which was measured in real time using a nanorespirometer (Unisense, Aarhus, Denmark) and converted to oxygen consumption rate using SensorTrace Pro (Unisense) according to the previous studies (Lopes et al 2005, Van Hoeck et al 2011. In total, 54 zygotes, equally distributed along treatments, were analyzed on three independent occasions.…”

The invasive and new non-invasive methods of mammalian oocyte and embryo quality assessment: a review

“…Recently, an interesting assessment of embryo quality was presented by Lopes et al (2005Lopes et al ( , 2007. They introduced the nanorespirometer -a device for the evaluation of the oxygen usage by embryos.…”

“…Most of these methods had essential disadvantages: they were invasive, demanded technical resources, time to carry out measurements, application of UV light or radioactive reagents, and were dangerous for the life of the assessed embryos. In this aspect, the device introduced by Lopes et al (2005) seemed especially promising. The nanorespirometer is a modern microsensoric technology that provides accurate and quick assessment of single embryos breathing in various stages of development.…”

Mitochondrial Activity as a Biomarker of Gamete and Embryo Health

“…However, other methods suggested to indirectly report mitochondrial activity in oocytes and preimplantation stage embryos, such as quantitation of rates and levels of oxygen uptake from culture medium, have been used to assess oocyte and embryo competence in different species, including the human [ 13,[103][104][105][106] . Whether uptake fi ndings can be related to outcome and, therefore, serve as the primary criterion for noninvasive oocyte or embryo selection is still unclear in human IVF [ 107 ] ; reliable stage-speci fi c threshold levels of oxygen consumption below which developmental competence can be clearly and reproducibly shown to be compromised, based on fertilizability, embryo performance in vitro, and outcome after transfer, have yet to be determined or established de fi nitively.…”