Ex vivo gene electrotransfer to the endothelium of organ cultured human corneas

To describe an innovative device that allows gene electrotransfer to human corneal endothelial cells (EC) during storage in organ culture.

Customized electrodes without endothelial contact were developed. Two plasmids containing the cytomegalovirus promoter and reporter genes [enhanced green fluorescent protein (eGFP) or beta-galactosidase (beta-gal)] were electroporated in 2 series of human corneas with eight 1-Hz 100-ms pulses of 125 mA square current. Controls were exposed to naked DNA without electric pulses. eGFP-transduced corneas were used to determine the transgene expression kinetics, whereas beta-gal measured transfection efficiency using image analysis tools. Overall, endothelial toxicity was determined by: (1) cytotoxicity tests using triple staining with Hoechst 33342, ethidium homodimer III, and calcein AM, 3 h and 3 and 14 days after electroporation on the series of 15 eGFP-transfected paired corneas; (2) anti-ZO-1 staining to assess tight junctions' integrity.

All electroporated corneas carried transfected ECs, whereas the controls carried none. eGFP expression was observed 3 h after electrotransfer, and was then present from days 1 to 28. Transfection efficiency determined on 63 corneas transfected with beta-gal ranged from 0.1 to 54% of the transfected ECs (mean +/- SD: 7 +/- 11%, median: 2.9%) with significant reproducibility for paired corneas from the same donor. Electroporation produced low early EC death. Anti ZO-1 staining revealed no dramatic change in EC mosaic continuity, neither 1 and 3 nor 28 days after electroporation.

Gene electrotransfer to the endothelium of organ-cultured human corneas with custom-designed electrodes allows rapid and easy EC transfection. However, further optimization is required to ensure reproducible results.