Dynamic changes of the extracellular matrix during corneal wound healing

Abstract

The extracellular matrix (ECM) confers transparency to the cornea because of the precise organization of collagen fibrils and a wide variety of proteoglycans. We monitored the corneal wound healing process after alkali burns in rabbits. We analyzed the location and expression of collagens and proteoglycans, the clinical impact, and the recovery of optical transparency. After the animals received both general and ocular topical anesthesia, the central cornea of the left eye was burned by placing an 8-mm diameter filter paper soaked in 0.5 N NaOH for 60 s. The eyes were evaluated under a surgical microscope at 1, 3, and 6 months after burning. At each time point, the clinical conditions of the burned and control corneas were observed. The arrangement of collagen fibers in the corneal stroma was visualized by Picrosirius-red staining, Gomori's silver impregnation and transmission electronic microscopy. Corneal light transmittance was also measured. Myofibroblasts presence was analyzed by immunohistochemistry. mRNA expression levels of collagen types I and III, lumican, decorin, keratocan and alpha-smooth muscle actin were determined by quantitative real-time polymerase chain reaction. One month after alkali burn, the ECM was disorganized and filled with lacunae containing different types of cells and collagen type III fibers in the wound area. Corneal opacities were present with attendant loss of light transmittance. Collagen and proteoglycan mRNA expression levels were up-regulated. After three months, wound healing progress was indicated by reduced corneal opacity, increased light transmittance, reorganization of collagen fibers and only collagen type I expression levels were at control levels. After six months, the wound area ECM morphology was similar to controls, but transmittance values remained low, denoting incomplete restoration of the stromal architecture. This multidisciplinary study of the stromal wound healing process revealed changes in corneal transmittance, collagen organization, myofibroblasts presence and ECM composition at 1, 3, and 6 months after alkali burning. Documenting wound resolution during the six-month period provided reliable information that can be used to test new therapies.

Lumican promotes joint fibrosis through TGF‐β signaling

“…Lumican is a member of the class II small leucine‐rich repeat proteoglycans superfamily, which constitutes collagen fibrils in the extracellular matrix (ECM) [7]. Lumican is ubiquitously expressed in a variety of tissues, such as skin [8], liver [9], intervertebral discs [10], kidney [11], bone [12], cornea [7], heart [13], uterus, pancreas [14], intestine, placenta and articular cartilage [15]. Lumican plays a crucial role in the regulation of collagen fibrillogenesis [7] in several tissues, such as skin [8] and cornea [16].…”

USP10 Targeted Self-Deliverable siRNA to Prevent Scarring in the Cornea

“…To assess the protein expression of classic fibrotic markers, frozen sections were immunostained for collagen III, FN-EDA (also termed cellular FN), and a-SMA, all key markers of scarring. 52,53 For collagen III, compared to UnWnd, Wnd-NTC demonstrated a 276.2-fold increase in collagen III immunostaining (p < 0.01), which was reduced by 71.7% (p < 0.05) with Wnd-US09. The comparison between UnWnd and Wnd-US09 was not significant (Figures 3A and 3D).…”

Corneal Opacity: Cell Biological Determinants of the Transition From Transparency to Transient Haze to Scarring Fibrosis, and Resolution, After Injury

“…4 ). 28 , 29 Collagen type III production is upregulated in corneal fibroblasts by TGFβ, 30 , 31 and it is a major collagen upregulated in the corneal stroma after both fibrotic and non-fibrotic injuries. 28 , 32 Galiacy et al 33 showed that matrix metalloproteinase 14 overexpression in the cornea with a recombinant adeno-associated virus-based vector after injury reduced corneal opacity and expression of collagen type III.…”