Genetic modification possibilities in treating corneal diseases

Treatment of genetic eye disease poses significant medical and surgical challenges. Two gene based therapies were assessed using an in-vivo firefly luciferase bioluminescence mouse model to target corneal epithelium. Short interfering RNA (siRNA) targeting selectively only the mutant allele was assessed for efficacy, through its ability to downregulate corneal epithelial luminescence in vivo using live animal imaging. This innovative animal model provides clear advantages enabling assessment of topical, subconjunctival and intrastromal delivery. Potent and sustained in vivo gene silencing >50% for up to 7 days was observed after intrastromal injection of siRNA and various topical formulations are further being assessed.

siRNA therapy provides transient effect, however, Type II Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated nuclease 9 (Cas9) holds great promise to provide ‘one off’ permanent gene editing. Gene-specific cleavage of the mutant allele was detected through this method. DNA repair resulted in frameshift mutations predicted to result in mutant allele knockout. This offers exciting potential for translation into clinical treatment of corneal genetic diseases.