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LONDON — A macromolecular sugar derived from aloe vera is a safe, cheap, nontoxic and potentially therapeutic agent for prevention of scarring and haze following corneal refractive surgery, according to one specialist speaking here.

At the meeting of the United Kingdom and Ireland Society of Cataract and Refractive Surgeons, held in conjunction with the European Society of Cataract and Refractive Surgeons meeting here, Romesh Angunawela, MD, spoke about the use of the aloe-vera-derived sugar, mannose-6-phosphate (M6P) in refractive surgery.

"Key to the scarring and haze formation following corneal injury is the transformation of passive keratocytes into fibroblasts and in particular myofibroblasts," said Dr. Angunawela, of St. Thomas's Hospital, London. "This process is typical of the human adult organism, while in the embryo healing occurs without scarring."

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The balance between scar-free regenerative healing and healing with scarring hinges on the mix of cytokines released during tissue injury, and in particular on the TGF-beta family of cytokines, he explained. A predominance of TGF-beta 3 during healing in the embryo results in scar-free regenerative healing, while a predominance of TGF-beta 1 and 2 leads to characteristic adult scar formation.

"TGF is an obvious target for the modulation of corneal wound healing," the surgeon said. "The M6P, which binds competitively to the same cell receptor as the TGF-beta family, competitively antagonizes its pro-scarring actions and therefore reduces or stops scarring in the skin."

The effects of M6P were investigated in cultured human corneal cells, exposing them to culture media containing TGF-beta 1 with or without M6P. Cells without TGF-beta and M6P were used as controls.

"M6P proved to significantly inhibit the effect of TGF-beta on corneal keratocytes, suppressing their differentiation to myofibroblasts. The difference between groups was statistically significant," Dr. Angunawela concluded.