Abstract
Corneal cryopreservation can partially solve the worldwide concern regarding donor cornea shortage for keratoplasties. In this study, human corneas were cryopreserved using two standard cryopreservation protocols that are employed in the Tissue Bank of the Teresa Herrera Hospital (Spain) to store corneas for tectonic keratoplasties (TK protocol) and aortic valves (AV protocol), and two vitrification protocols, VS55 and DP6. Endothelial viability and general corneal state were evaluated to determine the protocol that provides the best results. The potential corneal cryopreservation protocol was studied in detail taking into consideration some cryopreservation-related variables and the endothelial integrity and stroma arrangement of the resulting cryopreserved corneas. TK corneas showed mostly viable endothelial cells, while the others showed few (AV) or none (DP6 and VS55). The corneal structure was well maintained in TK and AV corneas. TK corneas showed endothelial acellular areas surrounded by injured cells and a normal-like stromal fiber arrangement. Cryoprotectant solutions of the TK protocol presented an increasing osmolality and a physiological pH value. Cooling temperature rate of TK protocol was of 1 °C/min to −40 °C and 3 °C/min to −120 °C, and almost all of dimethyl sulfoxide left the tissue after washing. Future studies should be done changing cryopreservation-related variables of the TK protocol to store corneas of optical grade.
Highlights
IntroductionThe current corneal storage methods for keratoplasty only guarantee one month of optimal tissue preservation
With respect to vitrification protocols, non-viable cells in the endothelia of VS55- and DP6-cryopreserved corneas were observed, stained nuclei revealed that cells remained attached to Descemet’s membrane (Figure 1C,D)
We evaluated four corneal cryopreservation protocols attending specifIn this study, we evaluated four corneal cryopreservation protocols attending to corneal endothelial state, as endothelium is the major responsible for corneal ically to corneal endothelial state, as endothelium is the major responsible for corneal transparency and the first indicator of a successful cryopreservation protocol [18]
Summary
The current corneal storage methods for keratoplasty only guarantee one month of optimal tissue preservation. Those are hypothermic and organ culture storage [1,2]. The storage time limitation and the increasing worldwide scarcity of donor corneas should encourage us to find a long-term alternative for viable corneal storage. This alternative would be provided by cryopreservation [2,3]. Many corneal cryopreservation protocols were tested, after the publication of the promising results of Capella et al [4] and O’Neill et al [5]
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