Observations of high variability in DNA fragmentation of epididymal sperm in men

Men with obstructive azoospermia (OA) or infertility often require surgical sperm retrieval for assisted reproductive techniques. While sperm can be successfully obtained from either the testis or epididymis in these patients, sperm DNA integrity may differ between retrieval sites, which could influence reproductive outcomes. This study aimed to determine whether bilateral epididymal and/or testicular sperm extraction is necessary in men with OA or infertility and elevated DNA fragmentation index (DFI).

We retrospectively analyzed men who underwent bilateral testicular biopsy and/or microscopic epididymal sperm aspiration (MESA) by a single surgeon from 2020-2022. TUNEL assays were performed to assess DFI (normal ≤15%). The primary endpoint of the study was to evaluate the variability in DFI between the right and left testes/epididymis in men undergoing sperm extraction.

In total, 24 men met criteria to be included in this analysis who underwent sperm extraction with DFI analysis via MESA and/or testicular biopsy. Among patients with OA, testicular sperm demonstrated significantly lower DFI compared to epididymal sperm on both sides (right testis 9.52 vs. right epididymis 17.61, p = 0.01; left testis 9.22 vs. left epididymis 14.71, p = 0.04). For each individual patient with OA, the mean intra-patient difference in DFI between right and left epididymal sperm was significantly higher than the mean intra-patient difference in DFI between right and left testicular sperm (12.09% ± 6.58, compared to 2.27% ± 1.59, p < 0.001, respectively).

Bilateral epididymal sperm extraction may be warranted in men with OA given the observed intra-patient variability in DNA fragmentation between epididymides. Conversely, bilateral testicular extraction may be unnecessary, as no significant difference in DNA fragmentation variability was observed between sperm retrieved from either testicle.