Short communication: Can proAKAP4 be used as a predictor of rabbit sperm freezability?

This study aimed to evaluate the suitability of proAKAP4 —a structural protein associated with flagellar integrity— as a potential biomarker for predicting sperm quality after thawing, in the context of establishing a gene bank for Slovak national rabbit breeds. A total of 48 samples from 8 males of the Chrabran rabbit breed were collected and analysed. ProAKAP4 concentration was measured using ELISA (Rabbit 4MID Kit) in fresh ejaculates prior to cryopreservation. Native and post-thaw sperm quality was assessed via computer-assisted sperm analysis, focusing on total (TM) and progressive (PM) motility, as well as secondary motility parameters. To support motility-based findings, flow cytometry was additionally applied, employing DRAQ7, YO-PRO-1, Caspase 3/7, and FITC-PNA to evaluate sperm viability, apoptotic activity and acrosomal integrity. ProAKAP4 concentration in fresh semen showed a moderate negative correlation with post-thaw motility traits (r=–0.67 for % TM after freezing and thawing (F/T); r=–0.59 for % PM F/T). These findings suggest that proAKAP4 may hold potential as a predictor of sperm freezability in rabbits, but its relationship to post-thaw quality appears to differ from that observed in other species. The recorded moderate negative correlation implies a species-specific mechanism, possibly linked to differences in sperm structure or response to cryostress. Further research is needed to clarify the functional role of proAKAP4 in rabbit sperm preservation.