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Mark Buckley, Manuel Alejandro Ramirez Garcia, Yousuf Khalifa; Vulnerability of Corneal Endothelial Cells to Mechanical Forces with Increasing Death to Preservation Time. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1208.
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Although no correlation has been found between 5-year graft failures and death to preservation time (DPT), the role of DPT in longer-term corneal graft outcomes is unknown. Furthermore, corneal surgeons continue to express personal preferences for DPT when selecting corneal tissues. This work investigates the effects of increasing DPT on the vulnerability of corneal endothelial cell (CEC) to cell death when subjected to compressive mechanical forces of the kind applied to the endothelium when handling a donor cornea with forceps.
Fresh porcine eyes were obtained from a local slaughterhouse and transported to the lab in a cooler, then stored at 4°C. Intact corneo-scleral rims were dissected, stained and tested either 12<t<24 hrs (n=6) or 24<t<48 hrs (n=5) after slaughter. At the time of testing, central corneal buttons 8 mm in diameter were trephinated and mounted in a custom device while immmered in a bath of BSS. Specimens were then indented against a 3 mm diameter stainless steel bead until a prescribed compressive force was measured. CEC viability was assessed via fluorescence imaging of indicators of live and dead cells before and after indentation. Numbers of injured cells per area were quantified as a function of applied pressures within the contact area.
The number of injured cells per area across the range of applied pressures was lower for corneas stored for 12 to 24 hours than for those stored for more than 24 hours (Fig. 1). At the lower DPT, the number of injured cells per area peaked at ~200 cells/mm2 away from the centroid of indentation (where the highest pressure was applied), compared to the higher DPT which peaked at ~300 cells/mm2 at the centroid. Furthermore, at the lowest pressure ranges for the lower DPT, the number of dead cells per area was roughly equivalent to the sham group (no indentation). In contrast, measurable cell death was observed at these pressures for the higher DPT.
Our data indicate that CECs are more susceptible to compressive forces at higher DPT than at lower DPT. Increased cell loss at locations away from the centroid of indentation hint that cell injury could be due to shear rather than compressive stress, since the shear stress imparted by a spherical indenter does not peak at the centroid. Overall, our results suggest that decreasing DPT increases CEC stability against compressive forces.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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