Fenofibrate Loaded Microemulsion for Improving Diabetic Corneal Wound Healing

Purpose : Diabetic keratopathy (DK) is a common corneal complication of diabetes, with persistent epithelial defects. We previously reported that delayed corneal wound healing in DK is associated with PPARα downregulation and mitochondrial dysfunction. Fenofibrate (Feno), a PPARα agonist approved for dyslipidemia, is a promising topical therapy but is poorly soluble in water, limiting ocular delivery. This study aims to optimize a Feno microemulsion (ME) eyedrop and evaluate its efficacy in vitro and in vivo.

Methods : The Feno ME eyedrop was characterized for rheology, Cryo-TEM, droplet size/ polydispersity index (PDI), zeta potential, osmolarity, drug content, and 12-month stability. Primary human corneal epithelial cells (HCEC) were used in scratch assays to optimize and assess safety of individual ME components (oil, polymers/surfactants, co-surfactants). A linear scratch was created and cell migration over 24 h was quantified as wound closure based on the residual acellular area. The wound healing efficacy of Feno ME was assessed in HCEC exposed to diabetic stressors (high glucose and 4-HNE). Mitochondrial respiration under high glucose was measured using Agilent Seahorse Analyzer. In vivo, streptozotocin-induced diabetic C57BL/6J (STZ-DM) and db/db mice with corneal abrasions received topical Feno ME, saline, or placebo-ME (10 µL, 3×/day), and wound closure was monitored every 24 h.

Results : The optimized 0.5% Feno ME eyedrop (35±1 nm droplet size, PDI<0.3, zeta potential -1.3±0.6 mV, 768±25 mOsmol/kg, 97±2% drug loading efficiency) remained stable for 12 months with no significant changes in droplet size, PDI, zeta potential, or drug content. The optimized formulation showed no cytotoxicity and did not impair HCEC migration. Under diabetic stress, Feno ME significantly (P<0.01) promoted HCEC migration compared with placebo. In HCEC exposed to high glucose, Feno ME restored mitochondrial respiration relative to placebo. In vivo, topical Feno ME promoted cornealwound healing in STZ-DM and db/db mice (n=10-16 eyes) compared to untreated and placebo ME groups. Theformulation demonstrated shear-thinning behavior with acceptable blink tolerance comparable to marketed eyedrops.

Conclusions : This Feno ME eyedrop may provide a safe, well-tolerated, and patient-friendly treatment for diabetic corneal wounds, with strong potential for clinical translation.