We followed the oocyte vitrification and thawing procedure based on Zhang et al (2016) on inbred mouse oocytes. Unfortunately, after post-thawing, the oocytes remain lysed at 0.25 mol/L several times before they can be cultured in a human tubal fluid (HTF) medium at 37 °C in 5% CO2 of humidified air. Kindly advice. What could be the reason for the lysis condition? Thank you.