Abstract
Purpose: :
Despite increasing evidence of the regenerative potential of embryonic tissue, very little is known about wound healing in embryonic cornea. In this study we examine the inflammatory response and regeneration of the corneal extracellular matrix in wounded embryonic corneas.
Methods: :
We have developed a novel method of accessing and manipulating chick embryos at late stages of development enabling us to wound corneas and observe the healing process over time. A single wound traversing the epithelium and anterior stroma was created in the central cornea of one eye in each embryo at embryonic day (E7). Wounded and control corneas were collected between E7-E18 and analyzed for various aspects of the wound healing cascade observed in adult corneas.
Results: :
We observed widening of the epithelial wound within 16 hours post-wounding. There was no significant difference in cellular responses to inflammatory signals such as cytokine-induced apoptosis and activated cell proliferation between wounded and control corneas. Transdifferentiation of repair fibroblasts specified by smooth muscle actin, was observed briefly between E8-E10, and are absent in healed embryonic corneas. Surprisingly, regeneration of the cornea epithelium was not complete until E16. Extracellular matrix molecules such as fibronectin was up-regulated whereas collagen 1 expression was down-regulated in the stroma at the wound site, but returned to normal as the epithelium regenerated. Expression of keratan sulfate proteoglycan remained the unchanged during the healing process. By E18, majority of the wounded corneas were fully regenerated and were similar in transparency as unwounded controls.
Conclusions: :
These data suggest that there is a reduced inflammatory response and minimal ECM reconstruction during tissue regeneration in wounded embryonic corneas, allowing for scar-free wound healing.
Keywords: wound healing • extracellular matrix • microscopy: light/fluorescence/immunohistochemistry