Investigating phototoxicity of optical coherence tomography imaging in porcine and human spermatozoa

Abstract

Research question: Does exposure to near-infra-red optical coherence tomography (OCT) laser radiation induce phototoxic effects in porcine and human spermatozoa?

Design: Computer-assisted sperm analysis (CASA) was used to determine whether OCT laser illumination at or above levels typically used for imaging alters sperm motility. Flow cytometry was used to determine the impact of irradiation on sperm acrosome reaction status, DNA fragmentation, and membrane integrity. Additionally, in-vitro time-lapse OCT imaging of a porcine cumulus-oocyte complex with irradiated spermatozoa was performed to determine whether irradiated spermatozoa interact with and penetrate the cumulus oophorus. Finally, human spermatozoa were irradiated and analysed using CASA and flow cytometric techniques.

Results: All irradiated samples showed no significant difference in sperm DNA damage or CASA sperm motility parameters, including average path velocity, straight line velocity or curvilinear velocity, compared with their matched manipulation control, suggesting that sample irradiation did not compromise sperm viability, even when using an optical power of more than one order of magnitude greater than that typically required to image embryos. Proof-of-concept OCT imaging suggested that motility of irradiated spermatozoa during cumulus interaction was not affected by radiation.

Conclusions: No significant effect on the kinetics of boar and human spermatozoa was observed following near-infra-red OCT laser radiation. Future work will investigate the fertilization process and embryo development following near-infra-red OCT laser radiation.

Keywords: Infra-red; Optical coherence tomography; Phototoxicity; Sperm DNA damage.