Abstract
Purpose :
Though the role of Schwann cells in peripheral nerve repair has been extensively studied, little is known about the role of corneal Schwann cells (cSCs) in regeneration following corneal nerve injury. Opacity following corneal nerve injury due to trauma, corneal transplantation, or elective surgery is a feared complication that is poorly understood. We tested the hypothesis that, following corneal injury, cSCs initiate a genetic repair program which causes de-differentiation into a myofibroblast phenotype.
Methods :
Wild-type adult C57Bl/6 male and female mice were subjected to a penetrating stab injury under systemic and ocular anesthesia that produced a focal lesion through the epithelium, basement membrane and a significant part of the corneal stroma. Eyes were enucleated at 3, 7, or 14 days (n=3 for each time point) following injury and were processed for immunohistochemistry. Tissue cryosections were fixed and stained with antibodies against extracellular signal-regulated kinases-1, -2 (pERK1/2) (Santa Cruz, 1:200), glial fibrillary acidic protein (GFAP) (Abcam, 1:200), Sox10 (Abcam, 1:200), and α-smooth muscle actin (α-SMA) (Cell Signaling Technologies, 1:200). Stained tissues were examined by epifluorescence microscopy.
Results :
Immunohistochemical staining revealed that, at 3 days post-injury, increased expression of pERK1/2 occurs in stromal cells proximal to the lesion site with many pERK1/2-positive cells also co-staining for GFAP, a marker of Schwann cells (SCs). Cells co-staining for pERK1/2 and Sox10, an SC transcription modulator, are also present at the lesion. Many GFAP-positive cells at the lesion between 3 and 7 days post-injury also showed expression of α-SMA, indicating that cSC de-differentiation and subsequent conversion into the myofibroblastic phenotype had occurred. At day 14, there is continued co-expression of pERK1/2 with GFAP and α-SMA demonstrating a prolonged cSC response to injury.
Conclusions :
Our results are consistent with our hypothesis that cSCs de-differentiate into a myofibroblast repair phenotype following axonal injury. A temporal increase in pERK1/2 drives cSC reprogramming, followed by expression of fibrotic markers. Activation of the cSC repair phenotype is initiated as early as 3 days post injury and is maintained at 14 days post injury. This data presents new opportunities to study the potential regenerative as well as pathological roles of cSCs in corneal injury and disease.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.