Use of a plant enzyme preparation (Coronase) instead of hyaluronidase for cumulus cell removal before intracytoplasmic sperm injection

The aim of this study was to compare the efficiency of a plant enzyme preparation (Coronase) with animal extracted hyaluronidase to remove cumulus cells before intracytoplasmic sperm injection (ICSI). The first part of the study was performed on mouse oocytes and embryos. Coronase displayed a similar efficiency to that of hyaluronidase for removing cumulus cells and the same percentage of activated oocytes was obtained with both techniques. However, prolonged incubation in Coronase, 120 min, led to a degeneration of oocytes. Incubation of 2-cell mouse embryos for 10 min with Coronase did not affect their subsequent in-vitro development to blastocyst. Coronase was then compared to hyaluronidase in the treatment of human oocytes prior to ICSI. The time required for total denudation was slightly longer using Coronase (98 s +/- 25 s versus 84 s +/- 24 s respectively for Coronase and hyaluronidase; P < 0.01). However, the two pronuclear (2PN) fertilization rate (70/103 versus 63/107 respectively for Coronase and hyaluronidase, not significant) and the percentage of embryos with a good morphology (39/74 versus 32/67 respectively for Coronase and hyaluronidase, not significant) were identical with both treatments. In conclusion, Coronase displays an efficiency close to that of hyaluronidase, without any adverse effect on oocytes, and may be preferable for human use.