219 SORTING OF EQUINE SPERM USING A MICROFLUIDIC DEVICE AS A METHOD OF SPERM SELECTION FOR IN VITRO FERTILIZATION AND INTRACYTOPLASMIC SPERM INJECTION

Abstract

Microfluidic technology can be used for sperm separation. Microfluidic devices generate a fluid flow to sort sperm from a media reservoir into a collection chamber. In the human and mouse, the use of microfluidic devices resulted in the selection of sperm with improved sperm motility, normal morphology, and DNA integrity for in vitro fertilization (IVF), intrauterine insemination (IUI), and intracytoplasmic sperm injection (ICSI). With the use of microfluidic sperm separation, centrifugation can be eliminated, diminishing the risk of reactive oxygen species exposure and DNA damage. We hypothesised that equine sperm can be separated using a microfluidic sorting device (Fertile Plus^TM Sperm Sorting Chip; DxNow, Worcester, MA, USA) to improve the quality of sperm for ICSI. The aim of our research was to evaluate sperm parameters, including motility, morphology, membrane integrity, and DNA integrity, in frozen-thawed samples of equine semen before and after sorting using the Fertile Plus Sperm Sorting Chip. Two experiments were performed. In Experiment 1, the microfluidic device was used to separate frozen-thawed semen samples (n = 10) from research stallions (n = 3) with good quality frozen semen; all semen was frozen by one method in our laboratory. In Experiment 2, clinical samples of frozen-thawed semen (n = 11) from 7 stallions were evaluated. The semen was of variable quality and frozen at different facilities. Sperm analyses included (1) motility, (2) morphology (Hancock stain, Animal Reproduction Systems, Chino, CA, USA), (3) live-dead sperm (Hancock stain), (4) membrane integrity (HOS, hypo-osmotic swelling test), and (5) DNA fragmentation (SCD, sperm chromatin dispersion). Two sample t-tests were used to compare sperm parameters. In Experiment 1, use of the Fertile Plus Sperm Sorting Chip improved sperm parameters between the original and sorted samples, respectively: sperm motility (37.2 ± 13.0% and 62.2 ± 15.6%; P = 0.002), normal morphology (60.1 ± 12.2% and 75.5 ± 9.7%; P = 0.006), percentage live sperm (55.8 ± 16.0% and 73.6 ± 12.9%; P = 0.03), HOS (33.7 ± 7.2% and 48 ± 9.7%; P = 0.001) and sperm DNA fragmentation (12.3 ± 4.4% and 5.6 ± 4.4%; P = 0.004). When the Fertile Plus Sperm Sorting Chip was used in Experiment 2 to separate frozen-thawed semen from various sources, improvements were noted between the original and sorted samples, respectively, with increased motility (22.0 ± 13.0% and 57.0 ± 11.6%; P = 0.0009), normal morphology (58.4 ± 9.6% and 74.0 ± 10.3%; P = 0.005), a higher percentage of live sperm (55.5 ± 11.2% and 68.3 ± 14.2%; P = 0.04), and decreased sperm DNA fragmentation (22.3 ± 14.7% and 8.2 ± 8.3%; P = 0.004); no effect was observed on HOS (21.2 ± 6.0% and 24.9 ± 11.5%; P = 0.19). Our results demonstrate that use of the Fertile Plus Sperm Sorting Chip resulted in a subpopulation of sperm with improved quality parameters. Separation of sperm using a microfluidic device has the potential to select sperm with desirable characteristics for equine assisted reproductive techniques.