Amniotic membrane patching promotes healing and inhibits proteinase activity on wound healing following acute corneal alkali burn

Amniotic membrane (AM) contains basement membrane components and various pr oteinase inhibitors. Furthermore, when used as a graft, the basement membra ne of AM could block inflammatory insults to a damaged corneal surface. Thu s, we evaluated whether amniotic membrane patching could promote the healin g process by inhibiting proteolytic damage. Alkali wounds were inflicted on the central corneas of rabbits by applying a round filter paper, 6.0 mm in diameter. soaked in 1 N NaOH for 30 sec. Amniotic membrane patching was pe rformed over the perilimbal sclera immediately after wounding. A total of 1 15 rabbits were divided into four groups: (1) immediately covered by AM wit h the amnion cell side down up to the perilimbal sclera (n = 26): (2) cover ed by AM with the stromal side down up to the perilimbal sclera (n = 19): ( 3) anchored to the fornix (n = 29); and (4) uncovered as a control (n = 41) . AM was removed 3 days postoperatively. During follow-ups, epithelial defe cts, corneal thickness and its opacity of each eye were measured. Some corn eas were removed for histopathologic studies and for proteinase activity ar :say and zymography. The epithelial healing was faster and the corneal thic kness was thicker in all three AM-covered groups than in the control (P < 0 .05). No significant difference was found between covered and anchored grou ps (P > 0.05). Corneal opacity was least in the amnion cell side down group , infiltration of polymorphonuclear leukocytes (PMNs) was much less in AM-c overed groups than in the control. Pathological results were associated wit h zymographic findings, which revealed much higher proteinase activity in u ncovered group than AM-covered groups. Immediate intervention for acute alk ali burns with AM as a temporary patch promotes wound healing by inhibiting proteinase activity and PMNs infiltration. (C) 2000 Academic Press.