Hyaluronidase source and ICSI outcomes: a paired donor-oocyte study

Does the type of hyaluronidase used for oocyte denudation influence denudation efficiency, post-intracytoplasmic sperm injection (ICSI) degeneration, embryological development, morphokinetics and clinical outcomes in donor-derived sibling oocytes?

Prospective paired sibling-oocyte study including 44 oocyte donation cycles generating 88 ICSI recipient cycles. Within each donor cohort, oocytes were allocated to denudation with recombinant human hyaluronidase (Cumulase) or bovine-derived hyaluronidase (Hyase). Denudation time was recorded prospectively per cumulus-oocyte complex in a predefined subgroup of 15 donors. Embryological outcomes were analysed using generalized linear models accounting for donor pairing. Morphokinetic assessment was performed using KIDScore. Clinical outcomes included pregnancy, clinical pregnancy, miscarriage and live birth rates.

Overall, 795 metaphase II (MII) oocytes were injected: 379 after Cumulase denudation and 416 after Hyase denudation. Hyase reduced the denudation time significantly compared with Cumulase (mean ± SD 43.8 ± 4.0 versus 56.8 ± 5.8 s; P < 0.001), corresponding to a paired reduction of 22.9%. Post-ICSI degeneration was also lower with Hyase, with approximately half the odds of degeneration per injected oocyte compared with Cumulase (OR 0.49, 95% CI 0.27-0.88; P = 0.017). No significant differences were observed in fertilization, blastocyst formation, high-quality blastocyst rate, KIDScore, pregnancy, clinical pregnancy, miscarriage or live birth rates.

In donor-derived sibling oocytes, bovine-derived hyaluronidase was associated with a shorter denudation time and lower post-ICSI degeneration, without detectable differences in embryological, morphokinetic or available clinical outcomes. These findings should be interpreted as supporting further optimization of recombinant hyaluronidase denuding protocols, rather than as evidence of demonstrated clinical safety for bovine-derived products.