Purpose:
To determine whether titanium backplates are superior, with respect to corneal cell toxicity and growth, to the standard PMMA backplates for the Boston Keratoprosthesis (KPro).
Methods:
Human corneal-limbal epithelial (HCLE) cells were plated at equivalent cell density in wells containing either titanium discs, PMMA discs or neither (controls). The discs were prepared per normal KPro backplate cleaning and manufacturing protocols. Cells were cultured for either 24, 48, 72, 96, 144 or 168 hrs. Experiments were done in triplicate and repeated for the 48 and 144 hr times. In total, 24 controls, 24 PMMA discs and 24 titanium discs were utilized. To determine if a soluble toxic factor is emitted from the backplate materials, a concurrent experiment was performed placing the discs in Transwell® Permeable Supports, 3.0 µm pore size (CoStar) with the HCLE cells plated beneath. The number of viable cells per well was quantified at each time-point using Cell Titer 96® AQueous One Solution Proliferation Assay (Promega). A Repeated Measures ANOVA, with SAS v9.1, was used to compare trends over time among the 3 groups: control, PMMA, and titanium. P<0.05 was considered statistically significant.
Results:
HCLE cell growth in wells with titanium and PMMA discs was delayed and less than that observed in control wells (see Figure 1). The difference between the 3 groups was statistically significant over time, p=0.0048. Cell proliferation in wells with titanium discs was greater than with PMMA discs up to 96hrs (p<0.01). At 144 hrs, this difference lost significance, p=0.5917. No statistical difference was found between any of the groups when using trans-wells (p=0.9836).
Conclusions:
The in vitro model using HCLE cells demonstrates a statistically significant difference in cellular growth when cells are in contact with titanium compared to PMMA. Moreover, it appears that delayed growth is not due to soluble factor(s). This may have important clinical implications for the Boston Keratoprosthesis, and may support the move towards titanium backplates.
Keywords: keratoprostheses • cornea: epithelium • cell survival