X-Message-Number: 23642
Date: Mon, 15 Mar 2004 23:24:56 -0800 (PST)
From: Doug Skrecky <>
Subject: Improved vitrification solutions

  For years cryoprotectants with a high glass forming ability have been
given preference for inclusion in vitrification mixtures. Now Fahy has
stood this long standing preference on its head, with the provocative
finding that such solutions have a reduced toxicity when cryoprotectants
with low glass forming ability are substituted in vitrification mixtures.
Specifically substitution with 2.71 M ethylene glycol for the strong
glass former 2.21 M propylene 1,2-glycol significantly reduces toxicity.
  [I suspect the further substitution of propylene 1,3-glycol for the
strong glass former DMSO, would further reduce toxicity.
  In one test propylene 1,3-glycol turned out to be the only
concentrated cryoprotectant for which no evidence of toxicity was
detected. (1980 Journals of Reproduction & Fertility).]

---------- Forwarded message ----------
Cryobiology. 2004 Feb;48(1):22-35.
Improved vitrification solutions based on the predictability of
vitrification solution toxicity.

Fahy GM, Wowk B, Wu J, Paynter S.
21st Century Medicine, Inc., 10844 Edison Court, Rancho Cucamonga,
CA 91730, USA.

	Long-term preservation of complex engineered tissues and organs
at cryogenic temperatures in the absence of ice has been prevented to
date by the difficulty of discovering combinations of cryoprotectants
that are both sufficiently non-toxic and sufficiently stable to allow
viability to be maintained and ice formation to be avoided during slow
cooling to the glass transition temperature and subsequent slow
rewarming. A new theory of the origin of non-specific cryoprotectant
toxicity was shown to account, in a rabbit renal cortical slice model,
for the toxicities of 20 vitrification solutions and to permit the design
of new solutions that are dramatically less toxic than previously known
solutions for diverse biological systems. Unfertilized mouse ova
vitrified with one of the new solutions were successfully fertilized and
regained 80% of the absolute control (untreated) rate of development to
blastocysts, whereas ova vitrified in VSDP, the best previous solution,
developed to blastocysts at a rate only 30% of that of controls. Whole
rabbit kidneys perfused at -3 degrees C with another new solution at a
concentration of cryoprotectant (8.4M) that was previously 100%
lethal at this temperature exhibited no damage after transplantation and
immediate contralateral nephrectomy. It appears that cryoprotectant
solutions that are composed to be at the minimum concentrations needed
for vitrification at moderate cooling rates are toxic in direct
proportion to the average strength of water hydrogen bonding by the polar
groups on the permeating cryoprotectants in the solution. Vitrification
solutions that are based on minimal perturbation of intracellular water
appear to be superior and provide new hope that the successful
vitrification of natural organs as well as tissue engineered or clonally
produced organ and tissue replacements can be achieved.

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