On developing a thesis for Reproductive Endocrinology and Infertility fellowship: a case study of ultra-low (2%) oxygen tension for extended culture of human embryos

Abstract

Fellows in Reproductive Endocrinology and Infertility training are expected to complete 18 months of clinical, basic, or epidemiological research. The goal of this research is not only to provide the basis for the thesis section of the oral board exam but also to spark interest in reproductive medicine research and to provide the next generation of physician-scientists with a foundational experience in research design and implementation. Incoming fellows often have varying degrees of training in research methodology and, likewise, different career goals. Ideally, selection of a thesis topic and mentor should be geared toward defining an Banswerableq uestion and building a practical skill set for future investigation. This contribution to the JARG Young Investigator's Forum revisits the steps of the scientific method through the lens of one recently graduated fellow and his project aimed to test the hypothesis that Bsequential oxygen exposure (5% from days 1 to 3, then 2% from days 3 to 5) improves blastocyst yield and quality compared to continuous exposure to 5% oxygen among human preimplantation embryos.K

Defining Physiological Normoxia for Improved Translation of Cell Physiology to Animal Models and Humans

“…One of the earliest adoptions of in vitro culture under physiological normoxia was in the field of in vitro fertilization, where the first successful culture of a human embryo to the blastocyst stage was achieved only under 5 kPa (557). Since then, working under a reduced ambient PO 2 (usually 5 kPa) has become reasonably common both in research and clinical IVF (45,186,285,314,418).…”

Reformatting the reproductive tract to accommodate the needs of human ARTs

“…The first of these, from Dan Kaser, fittingly sets the stage for what can be anticipated during REI fellowship with respect the sequence of events and challenges encountered during this training experience [9]. Well beyond this intent, his article delivers a spoton perspective for the subject of oxygen tension during embryo culture that is finally receiving the attention it deserves.…”

Using stem cell oxygen physiology to optimize blastocyst culture while minimizing hypoxic stress

“…This commentary is a response to the Fellows Forum on testing 2% O 2 for best culture of human blastocysts [1,2] prior to embryo transfer. It is a general analysis in support of the position that an understanding of stem cell physiology and responses to O 2 are necessary for optimization of blastocyst culture in IVF and enhance reproductive success in fertile women.…”

“…Since the beginning of IVF, ambient 20% O 2 use has evolved into the use of Blow^O 2 at 5%, which has been reviewed elsewhere [3,4]. In Fellows Forum recently in the Journal of Assisted Reproduction and Genetics, there were well-done expositions of how to navigate a fellow's trajectory in science and medicine and both fellows analyzed recent data on the roles of Bultra-low^O 2 in optimizing embryo culture [1,2]. The ultra-low O 2 is 2%, which is also known to be physiologic for stem cells [5,6] and similar to the uterine milieu of implanting mouse, human, and other mammalian embryos [7][8][9][10].…”

“…All of the studies analyzed [1,2,55,56] had the important hypothetical flaw of not providing lactic acid removal and nutrition addition at sufficiently high rates to provide blastocyst cell growth with the required optimized environment at 2% O 2 . Mouse TSC optimization of proliferation after 24 h at 2% O 2 requires changing media every 12 h to obviate the alternate outcome at 24 h of bright yellow media acidosis Fig.…”