Tissue Engineering The Vasculature of an Allograft Into a Functional Autograft.

Abstract

Background-Chronic systemic immunosuppression remains the backbone of clinical transplantation. The intima of the vasculature is the site of recruitment of immune cells and antibody deposition. The antigenicity of vascular endothelial cells (VEC) is related to the surface expression of antigen systems such as the MHC and ABO blood group antigens. Reducing VEC antigenicity represents a targeted approach to ameliorating allo-responsiveness to engraftment. We investigated if it is feasible to tissue engineer the most immunogenic component of an allograft. Method-Human renal allografts (n=4) procured but later rejected for clinical transplantation were transitioned from hypothermic preservation to nearnormothermic, acellular ex vivo perfusion. The VEC were first treated with a bioengineered interface consisting of a nano-barrier membrane (NB-LVF4) during 3 hours of an acellular warm perfusion. Following placement of the membrane, 1.0x108 fluorescently labeled VEC were introduced into the perfusion via the arterial line. Following 12 hours of perfusion, the majority of the VEC left the circulation (<2.0X106 remaining). Results-Frozen sections made from each kidney were evaluated by fluorescent microscopy. The labeled VEC were found exclusively along the vascular lumens. Therefore the native VEC, immunocloaked by NB-LVF4, was coated with labeled VEC resulting in the tissue engineering of an allograft into an autograft. When mononuclear cells isolated from the donor of the seeded VEC were stimulated by the tissue engineered blood vessel, there was no proliferative response. However, when the same mononuclear cells where stimulated with the native allogenic VEC of non-treated blood vessels, a strong proliferative response was observed.Figure: No Caption available.Conclusions-These results demonstrate that tissue engineering the most immunogenic component of an allograft is feasible. Rather than whole organ decellularization, it may be more feasible to tissue engineer a targeted component. In addition, the tissue engineered construct provided a non-immunogenic surface that prevented a normal allogeneic response.