APOA2 and varicocele: Proteins associated with the sperm–oocyte interaction, such as T-complex protein 1 subunit alpha isoform a (TCP1), T-complex protein 1 subunit delta isoform a (CCT4) and T-complex protein 1 subunit theta isoform 1 (CCT8); protein folding, such as HSPA2 and lipid peroxidation and DNA fragmentation, such as apolipoprotein A2 (APOA2), were absent or underexpressed in varicocele patients [126].