Cytochrome C Oxidase 6B2 Reflects the Mitochondrial Status Through the Oxidative Phosphorylation

Background: Asthenozoospermia (astheno) is a common male infertility disorder associated with low sperm motility. The progressive movement of sperm is an important factor in the fertilization rate, and it requires a high level of adenosine triphosphate (ATP). Objectives: This experimental study aimed to identify the role of cytochrome c oxidase 6B2 (COX6B2) as an important functional subunit of Cytochrome-c Oxidase in sperm motility. Methods: According to the World Health Organization (WHO) criteria, Semen samples were collected from 14 asthenozoospermia and 16 normospermia individuals that were referring to the Infertility Research and Treatment Center of Khuzestan, Iran in October 2016-May 2017. The sperm from two groups was isolated via the Percoll density gradient centrifugation to prepare healthy, motile sperm for COX6B2 immunofluorescent staining and real-time polymerase chain reaction (PCR). In addition, apoptosis assessment was carried out simultaneously to compare apoptosis and the COX6B2 expression level. To analyze the data, descriptive statistics including frequency and mean and analytical statistics including Fisher's exact test and two independent samples were used. Results: COX6B2 was detected in midpiece of the sperm by immunofluorescence assays. In addition, the percentage of COX6B2 positive sperm in the astheno samples was almost half that of the normal group (49.0 +/- 15.8 to 28.7 +/- 14.1, P = 0.641). Real-time PCR definitely reconfirmed the immunofluorescent staining result. A decrease in apoptosis was shown in as the no samples compared with the normal group (19.1 +/- 0.4 to 9 +/- 0.2, P = 0.04). Conclusions: The expression of COX6B2 in the sperm midpiece represents the OXPHOS pathway and functionality of mitochondria in sperm. This study introduced COX6B2 staining as a potential functional test for the recognition of competent mitochondria in sperm and it could be assigned as a biomarker in male-factor patients.