Fertilization and development of mouse oocytes cryopreserved using a theoretically optimized protocol

Jens O.M. Karlsson, Ali Eroglu, Thomas L. Toth, Ernest G. Cravalho, Mehmet Toner

Research output: Contribution to journalArticle

101 Scopus citations

Abstract

Rational design of a cryopreservation protocol was demonstrated by using theoretical models of the cryopreservation process to develop an optimal freezing protocol for mouse oocytes. A coupled mechanistic model of the processes of freeze-induced cell dehydration and intracellular ice formation was developed, and cryomicroscopical measurements of intracellular ice formation kinetics were used to determine biophysical parameters required by the model, and to test model predictions of the freezing behaviour of mouse oocytes. A simple phenomenological model for oocyte damage resulting from exposure to concentrated electrolyte and cryoprotectant solutions during cryopreservation was obtained by defining a cost function equal to the duration of the freezing protocol. A two-step freezing protocol was theoretically optimized by using a sequential simplex algorithm to minimize the cost function, subject to the constraint that the predicted probability of intracellular ice formation remain below 5%, yielding a putative optimum at the cooling rate B = 0.59°C/min, and plunge temperature T(p) = -67°C. By systematically varying B and T(p) about these values in experiments with mouse oocytes cryopreserved in 1.5 M dimethyl sulphoxide, the maximal recovery of intact oocytes with a normal morphology (82%) was obtained for B = 0.5°C/min and T(p) = -80°C. Further evaluation of the fertilizability and developmental capacity of oocytes cryopreserved using the optimized protocol yielded cleavage to the 2-cell stage in 65% of oocytes inseminated, and blastocyst formation in 50% of these 2-cell embryos.

Original languageEnglish (US)
Pages (from-to)1296-1305
Number of pages10
JournalHuman Reproduction
Volume11
Issue number6
DOIs
StatePublished - Jun 1996
Externally publishedYes

Keywords

  • Cryopreservation
  • Mouse oocytes
  • Optimization
  • Rational design
  • Theoretical modelling

ASJC Scopus subject areas

  • Reproductive Medicine
  • Obstetrics and Gynecology

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