Fibronectin as a new biomarker for human sperm selection in assisted reproductive technology

Fibronectin (FN) is a multifunctional diametric glycoprotein on the surface of the sperm that plays an important role in the sperm-oocyte interaction and fertilization process. The aim of the present study was to assess the FN levels as a sperm surface biomarker for sperm selection in assisted reproductive technology.

Polyclonal antibody against human FN was produced in rabbit. Its quality, purity, and immune reactivity were assessed by SDS-PAGE and western blot. In addition, the presence of FN on the sperm surface was assessed through immunocytochemistry and flow cytometry. The amount of FN and the sperm quality were assessed in normozoospermia (N) (42 men) and asthenoteratozoospermia (AT) (72 men) groups through sperm chromatin dispersion (SCD), sperm chromatin structure assay (SCSA), and chromatin maturation index (CMI).

The results showed the distribution of FN protein on the equatorial region of the human sperm surface. In addition, the FN levels were found to have a significant difference between the two groups with 24.64±9.08% in N and 16.90±7.27% in AT (p≤0.0001). In addition, FN level negatively correlated with SCD (p≤0.0001), SCSA (p≤0.0001), and CMI (p≤0.001). Threshold values of FN level and DNA fragmentation index (DFI) percentage were 16 and 30 and were identified as cut-off values to determine the N group with a specificity of 83.3% and 81.0% and a sensitivity of 16.8% and 19.0%, respectively. The specificity and sensitivity of FN-DFI were 91.2% and 8.8%, respectively.

It appears that FN can be used for the selection of sperm with suitable quality, although future studies are recommended.