Mechanisms of oligozoospermia: an oxidative stress perspective

Abstract

Infertile patients presenting with poor semen concentration, motility, and morphology have significantly higher levels of reactive oxygen species (ROS). In this cross-sectional study, our goal was to: 1) determine how semen parameters such as concentration, motility, morphology, as well as ROS are altered in oligozoospermic men alone and those in combination with poor sperm concentration, motility, morphology, and compare these with three control groups; unproven donors, donors with proven fertility <2 years, and proven donors with fertility established >2 years; 2) establish the cutoff, sensitivity, specificity for ROS, and see how it compared in the three donor groups compared to the patient groups, and 3) establish the reference range for the various semen parameters in these three donor groups compared to the oligozoospermic group by generating receiver operating characteristic (ROC) curves for each parameter. Fifty-six donors and 101 infertile men were included in this study. The patient group included: oligozoospermia: n = 16; oligoasthenozoospermia (OA): n = 12; oligoteratozoospermia (OT): n = 19; oligoasthenoteratozoospermia (OAT): n = 54. The patient group was compared with the three donor groups. Proven donors who had established a pregnancy in the past or recently (<2 years) had significantly improved semen motility and morphology compared to the OAT and OT groups (p < 0.001). In the OAT group, normal morphology was positively correlated with concentration and negatively with levels of ROS. Compared to the three donor groups, oligozoospermic patients in the OAT, OT, and OA groups had significantly elevated ROS levels. The cutoff for ROS in the proven donors < 2 years was significantly lower with a higher sensitivity and specificity compared to the unproven donors and donors who had not established a recent pregnancy. These results indicate a positive association between semen parameters and ROS suggesting a common underlying mechanism in these infertile patient groups.

Contemporary evidence on the physiological role of reactive oxygen species in human sperm function

“…Reactive oxygen species (ROS) have been extensively studied, and their detrimental effects on male fertility are well accepted. It has already been reported that pathological ROS levels have a deleterious effect on semen quality, including spermatozoa motility [3][4][5], viability, morphology and concentration [6,7].…”

Physiological and Pathological Roles of Free Radicals in Male Reproduction

“…• Supplementation of 60 mg/day of coenzyme Q10 for 103 days led to an increase in the fertilization rate but had no effect on motility, morphology or concentration in 17 patients with low fertilization rates due to male factor infertility [177] • 60 patients with idiopathic asthenozoospermia who received 200 mg/day of coenzyme Q10 demonstrated significant improvement in motility after 6 months of treatment [178] [11,12]. Nevertheless, significant set up costs have to be taken into consideration, and the data generated by chemiluminescence must be interpreted carefully because a variety of factors can affect the signals obtained [181].…”

“…Because high levels of ROS have been associated with a decreased male infertility, measuring ROS levels in semen is an important part of the initial evaluation as well as follow-up of men with reproductive dysfunction [10][11][12]. Chemiluminescence and flow cytometry are currently the most common techniques in clinical andrology to assess and study seminal OS.…”

“…epididymal) environment, resulting in defective spermatogenesis and altered sperm function [9]. As expected, approximately 25% of infertile patients exhibit higher ROS levels in semen as opposed to fertile men [7,[10][11][12].…”

“…Increased ROS levels have been repeatedly correlated with a decreased sperm motility [10][11][12]90], although the exact mechanism involved is still not completely understood. One hypothesis suggests that H 2 O 2 diffuses across the membranes into the cells and inhibits the activity of vital enzymes such as NADPH oxidase [6].…”