Biochemical analyses of proteoglycans in rabbit corneal scars

Macromolecules from normal rabbit cornea and cornea containing a 2-mm diameter button of scar tissue were biosynthetically labeled with 35S-sulfate and 3H-glucosamine in vivo and in organ culture. Labeled macromolecules, including proteoglycans (PGs) extracted from the normal cornea, scar tissue, and corneal tissue adjacent to the scar with guanidine hydrochloride were chromatographed on DEAE-Sepharose CL-6B columns and eluted with increasing concentrations of NaCl. The elution pattern of corneal macromolecules synthesized in vitro was remarkably similar to that in vivo. In another experiment, corneas having 2-, 4-, and 8-week-old scars were labeled in organ culture and also extracted. Scars synthesized PGs with lower sulfation than those of adjacent corneal tissue. Although PG synthesis in scar decreased with wound age, the synthesis in adjacent cornea remained the same. In a third experiment, PGs extracted from pools of unlabeled 2- and 4-week-old scars, adjacent corneal tissue, and normal corneas were chromatographed on ion-exchange columns and analyzed chemically. The quantity of PGs in scar and adjacent cornea increased with healing time. The ratios of keratan sulfate PG to dermatan sulfate PG in normal cornea, scar, and adjacent cornea was 2.3, 0.6, and 1.5, respectively. The PGs from adjacent corneal tissue had a higher charge density than those from scar. The predominant adjacent-cornea dermatan sulfate PG had a higher charge density than that in normal cornea. The authors conclude that cornea adjacent to the healing wound synthesized PGs measurably different fro those in scar and normal cornea.