Date of Award

Summer 8-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program/Concentration

Reproductive Clinical Science - Embryology & Andrology (Ph.D.)

Committee Director

Mahmood Morshedi

Committee Member

Benjamin Wong (Co-Chair)

Committee Member

Jacob Mayer (Co-Chair)

Committee Member

Frank Lattanzio

Committee Member

Helena Russell

Committee Member

Jacob Thundathil

Committee Member

Marlene Angle (External)

Abstract

Objective: To determine the impact of < 5% O2 tension on the in vitro development of human pre-implantation embryos. It was hypothesized that the optimal O2 tension would differ from the commonly utilized 5%, as shown by beneficial effects after the implementation of a more physiological O2 tension such as 2% for either the partial or full duration of in vitro culture.

Aim: To conduct a randomized controlled study to determine the effect of O2 tension during in vitro human embryo culture on the production of reactive oxygen species (ROS), apoptosis, gene expression and embryo development.

Background: The development of an embryo culture system that most faithfully mimics the in vivo environment and supports the metabolic requirements of the embryo is an essential endeavor. O2 tension is one aspect of an embryo culture system that can be reliably controlled. It is possible that < 5% O2 tension for all or part of in vitro culture may be more physiologically appropriate than the standard 5% O2.

Methods: Human zygotes were thawed and randomized into three treatment groups: culture in 2%, sequential 5-2% (5% days 1-3 and 2% days 4-6) or 5% O2. Treatment groups were compared for outcomes related to embryo development, ROS production, apoptosis, and gene expression.

Results: The 2% and 5-2% groups showed significant improvements in various embryo development milestones and morphological grading compared to the 5% group. ROS production was not found to be different between treatment groups. Relative amounts of active caspase-3 were highest in the 2% group and not significantly different between the 5-2% and 5% groups. Apoptotic cell rate was decreased in the 5-2% group compared to the 2% group. Expression of BAX was increased in the 2% group compared to the 5% group and expression of PRDX1 was increased in the 5-2% group compared to the 5% group.

Conclusions: The 5-2% group showed significant improvements in embryo development compared to the 5% group, while not showing the significant increases in apoptosis related outcomes seen in the 2% group. Embryo culture in a sequential 5-2% O2 tension shows promise after evaluation in these in vitro endpoints and may represent culture more similar to the in vivo state than 5% O2. Further research is justified to determine if this culture method can improve outcomes in ART treatment.

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DOI

10.25777/9t98-kh06

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