Development of a new clinically applicable device for embryo evaluation which measures embryo oxygen consumption.
Does a new system-the chip-sensing embryo respiration monitoring system (CERMs)-enable evaluation of embryo viability for potential application in a clinical IVF setting?



The system enabled the oxygen consumption rate of spheroids, bovine embryos and frozen-thawed human embryos to be measured, and this rate corresponded to the developmental potential of embryos.



To date, no reliable and clinically suitable objective evaluation methods for embryos are available, which circumvent the differences in inter-observer subjective view. Existing systems such as the scanning electrochemical microscopy (SECM) technique, which enables the measurement of oxygen consumption rate in embryos, need improvement in usability before they can be applied to a clinical setting.



This is a prospective original research study. The feasibility of measuring the oxygen consumption rate was assessed using CERMs for 9 spheroids, 9 bovine embryos and 30 redundant frozen-thawed human embryos. The endpoints for the study were whether CERMs could detect a dissolved oxygen gradient with high sensitivity, had comparable accuracy to the SECM measuring system with improved usability, and could predict the development of an embryo to a blastocyst by measuring the oxygen consumption rate. The relationship between the oxygen consumption rate and standard morphological evaluation was also examined.



We developed a new CERMs, which enables the oxygen consumption rate to be measured automatically using an electrochemical method. The device was initially used for measuring a dissolved oxygen concentration gradient in order to calculate oxygen consumption rate using nine spheroids. Next, we evaluated data correlation between the CERMs and the SECM measuring systems using nine bovine embryos. Finally, the oxygen consumption rates of 30 human embryos, which were frozen-thawed on 2nd day after fertilization, were measured by CERMs at 6, 24, 48, 72 and 96 h after thawing with standard morphological evaluation. Furthermore, the developed blastocysts were scored using the blastocyst quality score (BQS), and the correlation with oxygen consumption rate was also assessed.



The device enabled the oxygen consumption rate of an embryo to be measured automatically within a minute. The oxygen concentration gradient profile showed excellent linearity in a distance-dependent change. A close correlation in the oxygen consumption rates of bovine embryos was observed between the SECM measuring system and CERMs, with a determination coefficient of 0.8203 (P = 0.0008). Oxygen consumption rates of human embryos that have reached the blastocyst stage were significantly higher than those of arrested embryos at 48, 72 and 96 h after thawing (P = 0.039, 0.004 and 0.049, respectively). Thus, in vitro development of frozen-thawed human embryos to the blastocyst stage would be predicted at 48 h after thawing (day 4) by measuring the oxygen consumption using CERMs. Although a positive linear relationship between BQS and the oxygen consumption rate was observed [the determination coefficient was R(2) = 0.6537 (P = 0.008)], two blastocysts exhibited low oxygen consumption rates considering their relatively high BQS. This suggests that morphology and metabolism in human embryos might not correlate consistently.



Transfer of the embryo and pregnancy evaluation was not performed. Thus, a correlation between oxygen consumption and the in vivo viability of embryos remains unknown. Clinical trials, including embryo transfer, would be desirable to determine a threshold value to elect clinically relevant, quality embryos for transfer. We utilized frozen-thawed human embryos in this study. The effect of these manipulations on the respiratory activity of the embryo is also unknown.



Selection of quality embryos, especially in a single embryo transfer cycle, by CERMs may have an impact on obtaining better clinical outcomes, albeit with clinical trials being required. Furthermore, the early determination of quality embryos by CERMs may enable the omission of long-term in vitro embryo culture to the blastocyst stage. CERMs is scalable technology that can be integrated into incubators and/or other embryo evaluation systems, such as the time-lapse systems, due to its chip-based architecture. Thus, CERMS would enable automatic measurement of oxygen consumption, under 5% CO2, in the near future, in order to reduce oxidative stress from exposure to atmospheric air.



This study was supported by grants from the Health and Labor Sciences Research Grant (H24-Hisaichiiki-Shitei-016). The authors have no conflicts of interest.



Not applicable.
Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
Hiroki
H
Kurosawa
Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
Hiroki
H
Utsunomiya
Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
Naomi
N
Shiga
Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
Aiko
A
Takahashi
Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
Motomasa
M
Ihara
Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
Masumi
M
Ishibashi
Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
Mitsuo
M
Nishimoto
Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
Zen
Z
Watanabe
Department of Biochemical Engineering, Yamagata University, Yamagata 992-8510, Japan.
Hiroyuki
H
Abe
Department of Obstetrics and Gynecology, Graduate School of Medicine, Akita University, Akita 010-8543, Japan.
Jin
J
Kumagai
Department of Obstetrics and Gynecology, Graduate School of Medicine, Akita University, Akita 010-8543, Japan.
Yukihiro
Y
Terada
Department of Obstetrics and Gynecology, Faculty of Medicine, Yamagata University, Yamagata 990-9585, Japan.
Hideki
H
Igarashi
Department of Obstetrics and Gynecology, Faculty of Medicine, Yamagata University, Yamagata 990-9585, Japan.
Toshifumi
T
Takahashi
Department of Obstetrics and Gynecology, Hirosaki University School of Medicine, Hirosaki 036-8562, Japan.
Atsushi
A
Fukui
Department of Obstetrics and Gynecology, Fukushima Medical University, Fukushima 960-1295, Japan.
Ryota
R
Suganuma
Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan masahito.tachibana.c1@tohoku.ac.jp.
Masahito
M
Tachibana
Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
Nobuo
N
Yaegashi
D000818:Animals; D001755:Blastocyst / Q000502:physiology*; D002417:Cattle; D046149:Embryo Culture Techniques; D004624:Embryo Transfer; D047108:Embryonic Development / Q000502:physiology*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D010101:Oxygen Consumption / Q000502:physiology*; D011247:Pregnancy
electrochemical method; embryo metabolism; embryo quality; embryo selection; human embryo; non-invasive sensor; oxygen consumption