The effect of allo-injury in an in vitro model of allograft microvasculature.

Endothelial cells are critical to the integrity of allograft vasculature and can be damaged by alloreactive T cells or soluble mediators of alloreactivity. The biochemical effects of T cell-mediated damage to the endothelial cells have been studied, but not the structural and morphological effects of allo-injury on endothelial cells in the allograft. We utilized an assay that reproduces microvasculature in vitro to study the effect of alloreactivity on endothelial cells. In this assay, endothelial cells are induced into capillary-like networks that simulate microvascular capillaries. We studied the effect of allogeneic T cells and of soluble mediators from both mixed lymphocyte cultures (MLCs) and rejected heart allograft tissue on the in vitro capillaries. We found that both allogeneic T cells and soluble mediators inhibit the formation of the in vitro endothelial capillaries, suggesting that they cause a mild-to-moderate dysfunction of the endothelial cells. The inhibitory effect of the soluble mediators seems to be mediated, at least partly, by IFN-gamma, since this effect was prevented by antibody to IFN-gamma. Furthermore, pre-incubation of the in vitro capillaries with IFN-gamma appeared to magnify the effect of allogeneic T cells, as shown by a complete breakdown of well-formed in vitro capillary networks. Our experiments suggest that the in vitro capillary-tube model reflects structural injury to allograft vasculature by alloreactive T cells and their soluble mediators.

Amelioration of cyclosporin A effect on microvasculature by endothelin inhibitor.

BACKGROUND: We have previously shown that endothelial injury by cyclosporin A (CyA) is associated with an increased endothelin-1 (ET-1) release. We now sought to determine, in an animal model of angiogenesis, if inhibiting the effect of ET-1 on endothelial cells (ECs) would reverse the CyA-mediated endothelial injury in an animal model of angiogenesis. METHODS: An angiogenic mixture of Matrigel (0.5 ml), fibroblast growth factor (1 ng/ml), vascular endothelial growth factor (100 ng/ml), and heparin (64 unit/ml) was injected as a subcutaneous plug in the flank of C3H mice (n = 5). In experimental groups CyA (20 mg/ml), CyA, and BQ 123 (ET-A receptor antagonist), CyA and PD 142893 (ET-A and ET-B receptor antagonist), or CyA and ET-1 antibody were added to the angiogenic mixture. Angiogenesis in the mixture was quantified by modified planimetric point counting method in skin/Matrigel cross-sections stained with factor VIII to highlight endothelial neocapillaries. Mean +/- SD of angiogenic area was analyzed with analysis of variance and Bonferroni test. The survival curves obtained by Kaplan-Meier analysis were compared between the groups, and the statistical significance of survival and mortality rates was computed by log rank's and Fisher's exact test, respectively. RESULTS: The mean +/- SD of angiogenic area in control animals (without CyA in the angiogenic mixture) was 56.76 +/- 4.2. CyA inhibited angiogenesis in the subcutaneous angiogenic plug. Adding CyA to the angiogenic mixture significantly reduced angiogenic area (5.33 +/- 1.4, P <.001) while vehicle for CyA had no such effect (56.33 +/- 3.8, P =.10). Polyclonal ET-1 antibody or PD 142893 ameliorated the effect of CyA, whereas BQ 123 did not. The mean angiogenic areas in animals with ET-1 antibody, PD 142893, or BQ 123 in the angiogenic mixture were 57.20 +/- 7.5 (P =.06), 46.00 +/- 11.5 (P = 1.0), 8.60 +/- 2.9 (P <.001), respectively. CONCLUSIONS: Our data show that blocking ET-B receptors specifically ameliorates the microvascular injury to the neocapillaries in angiogenesis caused by CyA. Antiendothelin-1 antibody and ETR antagonist (PD 142893) could, therefore, reduce the ill effects of CyA on microvascular endothelium.