Crosslinking de colágeno por extratos vegetais aquosos em córneas de suínos

Abstract

Keratoconus is a progressive disease that affects patients' quality of life, causing changes in corneal curvature, resulting in irregular astigmatism and deterioration of vision quality. Corneal collagen crosslinking, promoted by riboflavin stimulated by ultraviolet A light, increases the biomechanical strength and resistance of the cornea, being the current intervention that effectively blocks the progression of the disease. The limitations and side effects, primarily associated with anatomical unpredictability and exposure to radiation, are driving the search for new cross-linking agents. Therefore, the objective of this study was to evaluate the effectiveness of five aqueous vegetable extracts: açaí pulp (Euterpe oleracea); grape seeds (Vitis labrusca); cinnamon bark (Cinnamomum aromaticum); barbatimão bark (Stryphnodendron adstringens); and cocoa beans (Theobroma cacao), as crosslinking inducers in pig corneas, aiming at a possible alternative treatment for keratoconus. Considering that the increase in crosslinks among collagen fibrils leads to an increase in the temperature and enthalpy of denaturation of the materials, the effectiveness was tested using differential scanning calorimetry. For this study, porcine corneas were divided into seven groups: negative control, consisting of untreated cornea samples; positive control, where the corneas were treated with 0.1% riboflavin photostimulated with ultraviolet A radiation, according to the standard protocol; and five experimental, where the samples were subjected to treatment with the respective 4% aqueous extract for 2 hours. After being treated, the corneas from the seven groups were evaluated for their thermal denaturation profile and histological changes; and the extracts underwent chemical composition analysis It was verified that the denaturation temperature and enthalpy values of four crosslinked cornea groups significantly increased compared to the negative control, with the group treated with riboflavin, as well as those treated with aqueous extracts of barbatimão peel, grape seeds and cocoa beans. Furthermore, the groups of these three extracts presented temperatures equivalent to the corneas treated with the standard protocol and had higher levels of tannins in their composition analysis among the groups studied. None of the extracts caused significant histological changes, with a significant reduction in keratocyte counts only in the positive control group, a known side effect of standard crosslinking. Thus, it is concluded that the aqueous extracts of barbatimão peel, grape seeds and cocoa beans were effective in promoting collagen crosslinking in porcine corneas similarly to conventional treatment, which possibly relates to the tannins present in their composition. However, further studies are needed to identify the molecules present in these extracts that were responsible for this effect, being promising alternative treatment options for keratoconus.