Label-free, high-throughput holographic imaging to evaluate mammalian gametes and embryos

Abstract

Assisted reproduction is one of the significant tools to treat human infertility. Morphological assessment is the primary method to determine sperm and embryo viability during IVF cycles. It has the advantage of being a quick, convenient, and inexpensive means of assessment. However, visual observation is of limited predictive value for early embryo morphology. It has led many to search for other imaging tools to assess the reproductive potential of a given embryo. The limitations of visual assessment apply to both humans and animals. One recent innovation in ART imaging is interferometric phase microscopy (IPM), also known as holographic microscopy. IPM/QPI is the next likely progression of analytical microscopes for the assisted reproduction laboratory. The IPM system analyzes waves produced by the light as it passes through the specimen observed. The microscope collects the light waves produced and uses the algorithm to create a hologram of the specimen. Recently, IPM has been combined with quantitative phase imaging (QPI), which joins phase contrast microscopy with holographic microscopy. These microscopes collect light waves produced and use the algorithm to create a hologram of the specimen. Unlike other systems, IPM can provide a quantitative digital image, and it can make 2-D and 3-D images of the samples. This review summarizes some newer and more promising QPI microscopy systems for evaluating gametes and embryos. Studies clearly show that QPI is superior to bright field microscopy-based evaluation methods when evaluating sperm and oocytes prior to IVF and embryos prior to transfer. However, further assessment of these systems for efficacy, reproducibility, cost-effectiveness, and embryo/gamete safety must take place before they are widely adopted.