Biodynamic Imaging: A Novel, Noninvasive Method for Assessing Embryo Viability
In vitro embryo production is the foundation of most assisted reproductive technologies, yet efficiency of these technologies is relatively low due to the lack of a reliable method for measuring embryo viability. Current methods to evaluate the viability of in vitro derived embryos are invasive or expensive to perform. In order to create a reliable system to assess the developmental potential of the embryo, a novel optical approach known as BioDynamic Imaging (BDI) has been proposed for application. BDI is able to measure dynamic processes inside an embryo encompassing a broad range of motions that relate directly to functional developmental events and has been validated for use in the drug treatment of tumor spheroids. Due to the morphological differences between tumors and embryos, use of the BDI to interpret the intracellular motion of embryos requires the identification of new parameters that relate to viability. The embryos were exposed to several stressors (low pH, high pH, ethanol) and evaluated using BDI to evaluate the intracellular motion induced by the specific stressors. This led to the identification of slope and nyquist floor as parameters which can distinguish viable embryos. Additionally, potentially fertilized oocytes were evaluated using BDI for twenty-four hours, allowing for the capture of the cellular dynamics of fertilization. Parameter analysis shows that the BDI has the capability to record intracellular motion associated with fertilization of the oocyte, resumption of meiosis and syngamy in a 1-cell embryo. Noninvasive techniques were utilized to identify molecular secretions in spent culture medium that are indicative of embryo quality. While proteomic analysis was not able to detect the protein leptin, metabolomic assays had some success finding amino acids leucine and glycine, yet detection levels were inadequate to consistently identify these and other amino acids. In addition, the morphology of each blastocyst was assessed and a morphological score was assigned to each embryo. They were then examined using BDI and a number of optical parameters were collected from the embryos during a 1-hour long measurement. A correlation matrix of the parameters identified a negative correlation between normalized standard deviation (NSD) and morphological score (corr= -0.58) and percent of apoptosis (corr= -0.21). Finally, an energetics assay was employed to compare the ATP concentration of healthy embryos with those that had oxidative catabolism inhibited and their ATP stores depleted. Preliminary results show that normalized standard deviation (NSD) and slope differ between the energetic groups. Successful completion of this project validates subcellular motion as a biomarker and several BDI parameters (NSD, slope, and nyquist floor) that can be utilized to predict developmental competence of embryos; this would guarantee the use of only the highest-quality embryos for transfer and lead to a significant improvement in the efficiency of assisted reproductive technologies.
Machaty, Purdue University.
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