Abstract
Purpose :
To evaluate wound healing in rabbit corneas that developed spontaneous persistent epithelial defects (PEDs) after photorefractive keratectomy (PRK).
Methods :
Forty-eight 10- to 15-week-old female New Zealand White rabbits weighing 2.5 to 3.0 kg underwent either -3 diopter (D) or -9DvPRK to generate a series of corneas to study wound healing after injury. During that series, seven corneas developed persistent epithelial defects (PEDs) detected with corneal examination with 0.5% fluorescein staining using a slit lamp that either did not have epithelial closure by one week after surgery, or subsequently had the closed epithelium break down to form PEDs two to three weeks after surgery. These corneas had slit lamp photography and were removed from the normal PRK series. Each PED cornea had triplex immunohistochemistry for keratocan (keratocyte marker), vimentin (mesenchymal cell marker), and alpha-smooth muscle actin (a-SMA, myofibroblast marker), as well as epithelial basement membrane components perlecan and collagen type IV.
Results :
All seven corneas that had PRK with PEDs (five -3D PRK and two -9D PRK), even the two evaluated at only one week after PRK, had a-SMA-positive myofibroblasts populating the anterior stroma within the PED, along with comingled a-SMA-negative cells that were likely corneal fibroblasts and possibly bone marrow-derived fibrocytes. In control PRK corneas, zero of four -3D PRKs and two of four -9D PRKs without epithelial defects had a-SMA-positive myofibroblasts in the anterior stroma. Both perlecan and collagen type IV accumulated in the anterior stroma of the epithelial defect without an epithelial basement membrane (EBM).
Conclusions :
PEDs that occurred spontaneously following PRK (a procedure that produces a transient neurotropic state in the cornea) all had myofibroblasts populating the superficial stroma within the epithelial defect as early as one week after the surgery. Five corneas with PEDs were -3D PRKs, which in previous studies rarely develop myofibroblasts after normal epithelial healing. Pharmacologic treatments that inhibit TGF beta signaling and thereby trigger myofibroblast apoptosis, including topical losartan, could decrease scarring in corneas with PEDs.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.