Expression of fibronectin isoforms bearing the alternatively spliced EIIIA, EIIIB, and V segments in corneal alkali burn and keratectomy wound models in the rat.
OBJECTIVE
To better understand the healing process in the wounded cornea, fibronectin (FN) isoforms bearing the alternatively spliced EIIIA, EIIIB, and V segments (EIIIA+, EIIIB+, and V+ FNs) were evaluated in alkali burn and keratectomy wound models in the rat.


METHODS
Alkali burn or keratectomy wounds (both 2 mm) were created, and corneas were harvested at various time points and analyzed by indirect immunofluorescence using antibodies specific for the EIIIA, EIIIB, and V segments as well as for the total pool of FN (total FN).


RESULTS
There was minimal staining for any variety of FN in the epithelium or basement membrane zone (BMZ) in normal cornea, but each antibody produced granular staining in the stroma. Bright staining for V+ and total FNs was evident at the denuded stromal surface 1 day following keratectomy. In contrast, staining for EIIIA+ and EIIIB+ FNs was negligible at 24 hours but appeared on the wound surface under the migrating unstained epithelium by the second day. BMZ staining for FN then gradually subsided, such that there was little or no staining by 6 weeks. In contrast, alkali burn wounds exhibited very little BMZ staining throughout the time course. Although there was preferential staining of the anterior aspect of Descemet membrane by anti-EIIIA and anti-EIIIB antibodies under normal conditions, the staining intensity of the anterior and posterior aspects became similar following corneal wounding.


CONCLUSIONS
Deposition of EIIIA+ and EIIIB+ FNs in the BMZ of the keratectomy wound occurs more slowly than deposition of V+ and total FNs. EIIIA+ FN is expressed in a distribution that overlaps with that previously described for the alpha 9 integrin subunit following corneal debridement, suggesting that EIIIA-alpha 9 interactions could occur during corneal wound healing. In contrast, the relative lack of FN deposition in alkali burn wounds suggests that proteolytic degradation of FN may occur; and this, along with impairment of new FN synthesis because of cellular damage, could play a role in the high prevalence of recurrent epithelial erosions in alkali-wounded corneas.
Havrlikova
Katerina
K
Hilles Immunology Laboratory, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA 02114, USA.
Mellott
Mei
M
Kaufman
Adam H
AH
Loredo
Grace A
GA
Peters
John H
JH
Colvin
Robert B
RB
Foster
C Stephen
CS
D017398:Alternative Splicing; D000818:Animals; D002057:Burns, Chemical / Q000378:metabolism*; D003315:Cornea / Q000187:drug effects / Q000378:metabolism*; D065306:Corneal Injuries; D004195:Disease Models, Animal; D005126:Eye Burns / Q000139:chemically induced*; D005131:Eye Injuries / Q000378:metabolism*; D005260:Female; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D012972:Sodium Hydroxide
D005353:Fibronectins; D020033:Protein Isoforms; D012972:Sodium Hydroxide