UC San Diego

Reproductive success is dependent on the ability of spermatozoa to reach and fertilize the oocyte. Although there are numerous assisted reproductive technologies that were developed for human use, not all are as effective in animals due to large variations in reproductive biology. The use of drugs and excessive handling on nondomestic animals may induce additional stress. Thus, there is a need for novel noninvasive, drug-free fertility treatments that are applicable across a range of species. Sperm swimming speed and swimming force are two measures of sperm quality; improvement of these qualities may increase the chances of successful reproduction. It is believed that red light irradiation stimulates cytochrome c oxidase in the mitochondria to increase ATP production. However, stimulation of the electron transport chain has been shown to increase reactive oxygen species, which may have negative effects on sperm DNA. In this thesis, the efficacy of red light irradiation for improving sperm swimming speed and swimming force and its effect on DNA are assessed. Human spermatozoa were irradiated with a monochromatic, coherent 633 nm laser for 30 minutes. Swimming speed was measured using a wavelet-based tracking algorithm implemented in LabVIEW. Swimming force was measured using optical trapping and position tracking. Oxidative DNA damage was assessed using single-cell imaging following immunofluorescent staining for double-strand breaks and an enzyme-linked immunosorbent assay for oxidized guanine. Both sperm swimming speed and swimming force increased after irradiation without significant DNA damage.