Abstract
Purpose: :
To investigate wound healing and the regenerative potential of embryonic corneas.
Methods: :
We have developed a novel method of accessing and manipulating chick embryos at late stages of development. Using this method, we created a single wound traversing the epithelium and anterior stroma in the central cornea of one eye in each embryo at E7. Wounded and unwounded stage matched corneas were collected at E7- E18 and analyzed for various aspects of the wound healing cascade observed in adult corneas.
Results: :
Embryonic corneal wounds expand in size within the first 16 hours post-wounding (hpw), exhibit partial re-epithelialization by 5 days post-wounding (dpw), and fully regenerate the corneal epithelium by 11dpw. During the healing process, there was no apparent difference in levels of apoptosis, nor activated cell proliferation between wounded and stage matched non-wounded corneas. Transdifferentiation of repair myofibroblasts, identified by smooth muscle actin expression, occured briefly between 16hpw and 5dpw, and was absent in healed embryonic corneas. Extracellular matrix (ECM) molecules, such as fibronectin and tenascin were up-regulated, whereas collagen I expression was down-regulated at the wound site. The distribution of these ECM components returned to normal as the epithelium regenerated. Expression of KSPG and perlecan remained unchanged during the healing process. By 11dpw, wounded corneas were fully regenerated and showed no apparent signs of scarring or fibrosis, similar to unwounded stage matched corneas.
Conclusions: :
These data suggest that there is minimal inflammatory response and ECM reconstruction during tissue regeneration in wounded embryonic corneas, allowing for scar-free wound healing.
Keywords: wound healing • development • extracellular matrix