Use of microfluidics to sort stallion sperm for intracytoplasmic sperm injection.

We determined if microfluidic sorting (MF) of frozen-thawed stallion sperm improves sperm population characteristics and results in embryo development after intracytoplasmic sperm injection (ICSI). The efficiency and efficacy of MF sperm separation was evaluated by comparing pre- and post-separation sperm population variables. Procedural comparisons were performed after sorting with MF, single-layer colloidal centrifugation (SLC) or swim-up (SU), and cleavage and embryo development were evaluated after ICSI using MF-sorted sperm. In Experiment 1, when compared to the original sperm sample, MF sorting resulted in a sperm subpopulation with greater motility, morphology, viability, and membrane as well as DNA integrity. After sorting by MF, SLC and SU in Experiment 2, motility, viability, and membrane integrity were similar for sperm sorted using MF and SLC; however, morphology and DNA integrity were greater in sperm sorted using MF when compared with SLC. Swim-up was the least effective sorting method. In Experiment 3, sperm were processed using MF and SLC prior to ICSI. Motility, morphology and DNA integrity were similar for sperm subpopulations sorted using either method; but viability was greater for sperm sorted using MF than SLC. Sorting did not improve sperm membrane integrity. Sorting with MF prior to ICSI resulted in similar cleavage and blastocyst development rates as SLC. We concluded that MF separation of stallion sperm resulted in a subpopulation with improved sperm population parameters, comparable or better than SLC and SU. Embryos were produced after ICSI using MF sperm sorting.