Reassessing the interpretation of oxidation-reduction potential in male infertility

Abstract

Male Infertility Oxidative System (MiOXSYS) has been proposed as a rapid and promising technology for the evaluation of sperm oxidative stress. In this case-control study, 134 men with normal sperm parameters (NSP) and 574 men with abnormal sperm parameters (ASP), according to the World Health Organization sperm assessment references values established in 2010, were enrolled. Conventional sperm parameters were evaluated in all patients. Sperm static oxido-reduction potential (sORP) was assessed using the MiOXSYS. Sperm DNA integrity was measured in 604 patients. To ensure that sperm concentration was not a confounding factor in the sORP index ratio, sperm and seminal fluid sORP from 57 randomly selected additional patients were also measured using the MiOXSYS. sORP index (mV/10⁶ sperm/mL) was higher in patients with ASP and seemed to correlate with conventional sperm parameters. Although receiver-operating characteristic analysis revealed that a sORP index cut-off of 0.79 could differentiate normal from ASP with 57.7% sensitivity and 73.1% specificity, these values are much lower than those found in the literature. These values also need to be higher to be applicable in a clinical setting. Furthermore, absolute sORP (mV) was not different in the presence or absence of spermatozoa. sORP index relationships with sperm parameters seem rather be due to sperm concentration, denominator of the sORP index ratio. The establishment of a reliable method using the absolute sORP value, independent of sperm concentration, needs to be addressed. Other oxidative stress biomarkers could be used to validate this method.

Lay summary: The World Health Organization (WHO) has recognized that oxidative stress may have a role in male infertility. Oxidative stress happens when there is an imbalance between the production of molecules containing oxygen and the antioxidants, molecules that neutralize the molecules containing oxygen. The molecules containing oxygen can cause damage to sperm DNA. This damage can be measured using a particular index and this study looked at whether the concentration of the sperm sample might have an impact on results and suggests this should be taken into consideration by clinicians and researchers.

Keywords: DNA integrity; male infertility; oxidoreduction potential; sperm.

Figure 1

sORP index (mV/106 sperm/mL) and absolute sORP (mV) according to sperm parameters. Mann–Whitney U tests were performed between the NSP group and all the other groups. NSP, normal sperm parameters (n = 143); ASP, abnormal sperm parameters (n = 565); O, oligozoospermia (n = 115), ASP patients with sperm concentration <15 × 106 sperm/mL; A, asthenozoospermia (n = 320), ASP patients with sperm concentration ≥15 × 106 sperm/mL and motility <40%; T, teratozoospermia (n = 212), ASP patients with sperm concentration ≥15 × 106 sperm/mL, motility ≥40% but normal morphology <4%; OAT, oligoasthenoteratozoospermia (n = 78), ASP patients with sperm concentration <15 × 106 sperm/mL, motility <40% and normal morphology <4%. Box plot extremities represent minimum and maximum values.

Figure 2

Differences of absolute sORP (mV) in sperm and seminal fluid alone. Sperm samples were centrifuged at high speed to obtain a sperm-free seminal fluid. sORP (mV) was measured in sperm and seminal fluid alone in each sperm sample. Mann–Whitney U test was performed between the two groups. n  = 57. Values are mean ± s.d.