A comparison of sperm parameters DNA fragmentation and telomere length in testicular versus ejaculated spermatozoa

While previous studies reported conflicting findings on DNA fragmentation in testicular versus ejaculated spermatozoa, this study aimed to perform a detailed analysis of testicular spermatozoa, evaluating sperm parameters and detailed morphology, DNA fragmentation, and relative telomere length across testicular and ejaculated spermatozoa. The study included 60 men in four groups: normozoospermic men (control), men with oligoasthenoteratozoospermia (OAT), men with a history of sperm presence in the semen who were candidates for conventional testicular sperm extraction (TESE), and non-obstructive azoospermia (NOA) patients undergoing microdissection testicular sperm extraction (M-TESE). Spermatozoa were evaluated for vitality (eosin staining), teratozoospermia Index (TZI) and detailed morphology (Diff-Quik staining), DNA fragmentation (sperm chromatin dispersion assay), and relative telomere length (q-PCR). The results demonstrated that sperm vitality was significantly lower in the OAT group. The control group showed markedly higher rate of normal morphology and lower TZI compared to the OAT, TESE, and M-TESE groups. The TESE and M-TESE groups showed higher rates of head-midpiece abnormalities and residual bodies compared to the control group (P < 0.0001, P < 0.0001, respectively). Sperm DNA fragmentation in the control group showed a significant decrease relative to all experimental groups (P < 0.0001). The control group demonstrated a significantly higher proportion of sperm with intact acrosomes than all experimental groups (P < 0.0001). Moreover, the relative sperm telomere length was markedly lower in the M-TESE group compared to the control (P = 0.0006), OAT, and TESE groups (P < 0.0001). Our results demonstrated that testicular sperm have significantly elevated DNA damage levels. Moreover, these spermatozoa exhibit increased frequencies of morphological abnormalities in the head and midpiece regions, reacted acrosomes, and residual bodies.