Experimental approach to improve endothelial barrier function in myocardium

Abstract

Recently, we showed that activated factor XIII (FXIIIa) has a direct influence on permeability (P) of cultured endothelial monolayer. Clinical investigation on children operated on for congenital heart disease has demonstrated a distinct correlation between decrease of endothelial barrier function (edema formation) and reduced FXIII activity. Our experiments investigated whether significant effects of FXIII could also be shown in a full-organ model. The effect of FXIII on endothelial barrier function was studied by determining the passage of trypan blue-labeled albumin in a model of cultured monolayers of porcine aortic endothelial cells and changes in myocardial water content of saline-perfused rat hearts in a Langendorff-circuit. The plasma FXIIIa (1 U/ml) reduced albumin permeability of aortic endothelial monolayers within 20 minutes from a basal value of 5.9 ± 0.4 × 10⁻⁶ cm/second by 30 ± 7% whereas the nonactivated plasma FXIII had no effect on permeability. Reduction of permeability to the same extent (by 34 ± 9%) could also be obtained with a thrombin-activated recombinant factor XIII A subunit (rhu FXIII; 1 U/ml) in this culture model. The effect of factor XIII A* on permeability was dose dependent with maximum effect at 5 U/ml (52 ± 11% reduction of permeability compared with control), and existed even if cells had hyperpermeability stress (KCN/2-DG). Activated rhuFXIII prevented the increase in myocardial water content in anoxic-reperfused rat hearts (448 ± 24 vs 517 ± 29 ml/100g dry weight). The data of the present study show that FXIII has a stabilizing effect at the site of endothelial cells not only in cultured monolayers but also in a model of the anoxic perfused rat heart.