Optical coherence microscopy as a label-free tool for imaging live oocytes and embryos

Confocal laser microscopy and other fluorescence imaging methods applied in biology allow for detailed structural and dynamic studies of a single cell, but require fluorescent markers to visualize cellular architecture and may cause short- and long-term photo-damage. Bright field microscopy, although non-destructive, does not provide detailed structural information. Optical coherence microscopy (OCM) is a promising alternative, as it does not require sample pre-processing or labelling and is capable of providing 3D images of intracellular structures.

Here we show that images obtained by OCM provide information useful for oocyte and embryo quality assessment. We applied OCM to image chromatin arrangement in prophase I (GV) oocytes, allowing to distinguish transcriptionally active (NSN) and inactive (SN) oocytes. We have also shown that OCM is capable of visualizing the nuclei in compact morulas, allowing for cell count. These parameters correlate with the oocytes’ and embryos’ quality. The OCM scanning protocols were verified to be safe for oocytes and preimplantation embryos. Our results suggest that OCM may be a valuable addition to the imaging toolkit used in assisted reproduction procedures.