Lacritin-mediated regeneration of the corneal epithelia by protein polymer nanoparticles

The avascular corneal epithelium plays an important role in maintaining normal vision and protecting the corneal interior from environmental infections. Delayed recovery of ocular wounds caused by trauma or refractive surgery strengthens the need to accelerate corneal wound healing and better restore the ocular surface. To address this need, we fused elastin-like polypeptide (ELP) based nanoparticles SI with a model mitogenic protein called lacritin. Lacritin fused at the N-terminus of the SI diblock copolymer is called LSI. This LSI fusion protein undergoes thermo-responsive assembly of nanoparticles at physiologically relevant temperatures. In comparison to ELP nanoparticles without lacritin, LSI showed potent signs of lacritin specific effects on a human corneal epithelial cell line (HCE-T), which included enhancement of cellular uptake, calcium-mediated signaling, and closure of a scratch. In vivo, the corneas of non-obese diabetic mice (NOD) were found to be highly responsive to LSI. Fluorescein imaging and corneal histology suggested that topical administration of LSI onto the ocular surface significantly promoted corneal wound healing and epithelial integrity compared to mice treated with or without plain ELP. Most interestingly, it appears that ELP-mediated assembly of LSI is essential to produce this potent activity. This was confirmed by comparison to a control lacritin ELP fusion called LS96, which does not undergo thermally-mediated assembly at relevant temperatures. In summary, fusion of a mitogenic protein to ELP nanoparticles appears to be a promising new strategy to bioengineer more potent biopharmaceuticals with potential applications in corneal wound healing.