Cryopreservation of cornea: a low cooling rate improves functional survival of endothelium after freezing and thawing.
OBJECTIVE
To investigate the influence of low cooling rates on endothelial function and morphology of corneas frozen with propane-1,2-diol (PROH).


METHODS
Rabbit corneas, mounted on support rings, were exposed to 1.4mol/l (10% v/v) PROH, seeded to initiate freezing, and cooled at 0.2 or 1 degrees C/min to -80 degrees C. Corneas were frozen immersed in liquid or suspended in air. After being held overnight in liquid nitrogen, corneas were warmed at 1 or 20 degrees C/min. After stepwise removal of the cryoprotectant, the ability of the endothelium actively to control corneal hydration was monitored during normothermic perfusion. Morphology was assessed after staining with trypan blue and alizarin red S, and by specular microscopy during perfusion.


RESULTS
Functional survival was achieved only after slow cooling (0.2 degrees C/min) with the cornea immersed in the cryoprotectant medium, and rapid warming (20 degrees C/min). These conditions also gave the best morphology after freezing and thawing.


CONCLUSIONS
Cooling rates lower than those typically applied to cornea improved functional survival of the endothelium. This result is in accord with previous observations showing the benefit of low cooling rates for cell monolayers [CryoLetters 17 (1996) 213-218].
Routledge
Caroline
C
Division of Ophthalmology, University of Bristol, Bristol Eye Hospital, Lower Maudlin Street, Bristol BS1 2LX, UK.
Armitage
W John
WJ
D000818:Animals; D003315:Cornea; D015925:Cryopreservation / Q000379:methods; D003451:Cryoprotective Agents; D004728:Endothelium, Corneal / Q000166:cytology / Q000502:physiology; D011409:Propylene Glycols; D011817:Rabbits; D014022:Tissue Survival
D003451:Cryoprotective Agents; D011409:Propylene Glycols