Seminal exosome protection of frozen human spermatozoa: homologous versus heterologous treatment.

RESEARCH QUESTION: How do homologous and heterologous seminal exosome treatments influence the quality of post-thaw spermatozoa?

DESIGN

In this in-vitro experimental study, semen samples were collected from 50 normozoospermic (N) and 50 oligoasthenoteratozoospermic (OAT) men undergoing analysis at an academic infertility centre. After exosome isolation, samples were treated with either N-derived exosomes (n-EXO) or OAT-derived exosomes (o-EXO) or left untreated before cryopreservation. The groups were thus N-nEXO and O-oEXO (homologous), N-oEXO and O-nEXO (heterologous) and untreated N and O controls. Post-thaw sperm quality was evaluated using motility, sperm DNA fragmentation (SDF), total antioxidant capacity (TAC), total oxidative status, mitochondrial membrane potential (MMP), membrane integrity and apoptosis.

RESULTS

Homologous treatment significantly improved OAT spermatozoa (O versus O-oEXO) in terms of progressive motility (P = 0.04), SDF (P = 0.014), TAC (P = 0.0005) and membrane integrity (P = 0.04). In N samples, n-EXO also improved motility (P = 0.048) and SDF (P = 0.015). Heterologous treatment increased motility in OAT spermatozoa (O versus O-nEXO, P = 0.03) but reduced motility (P = 0.002) and MMP (P = 0.03) in N spermatozoa (N versus N-oEXO).

CONCLUSIONS

These findings support the beneficial role of n-EXO in enhancing cryopreservation outcomes for both N and OAT spermatozoa. Interestingly, o-EXO exerted adverse effects on N spermatozoa but demonstrated a protective effect on OAT spermatozoa, contrary to initial expectations. The observed improvements with homologous treatments highlight the potential of using seminal exosomes as an alternative approach to the traditional removal of seminal plasma, reinforcing the importance of preserving key components of the seminal environment during freezing. Consequently, seminal exosomes could potentially serve as cryoprotectant additives to optimize sperm cryopreservation procedures.