X-Message-Number: 29801
Date: Thu, 30 Aug 2007 10:12:59 -0700 (PDT)
From: 
Subject: propylene glycol use is not recommended for cryopreservation

Reprod Biomed Online. 2007 Jun;14(6):709-14.
Theoretical considerations for oocyte cryopreservation by freezing.
  Fahy GM. 21st Century Medicine, Inc., Rancho Cucamonga, California, USA.
Attempts to cryopreserve oocytes by freezing have, to date, been based
mostly on empirical approaches rather than on basic principles, and
perhaps in part for this reason have not been very successful. Theoretical
considerations suggest some fairly 'heretical' conclusions. The
concentrations of permeating cryoprotectants employed in past studies have
probably been inadequate, and the choice of propylene glycol (PG) as a
protective agent is questionable. The use of non-penetrating agents, such
as sucrose to preshrink oocytes prior to freezing and which, therefore,
exacerbate osmotic stress during freezing, may be inappropriate, yet may
protect in part by reducing the concentration of PG during freezing. The
methods used to add and remove cryoprotectant may be suboptimal, and may
be based on an inadequate understanding of the cryobiological constraints
for oocyte survival. Given these concerns, it is not surprising that fully
satisfactory results have been elusive, but there is every reason to
believe that greater success is possible using a more theoretically
appropriate approach.
PMID: 17579984

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