Vascularized liver on-a-chip modeling cellular and humoral rejection of allografts

PROJECT SUMMARY Organ transplantation remains the best and most cost-effective clinical solution for end-stage organ failure; however, it comes with the burden of lifelong immunosuppression (IS). Although effective in preventing allograft rejection, immunosuppressive drugs have numerous side effects that negatively impact transplant recipients’ quality of life, including increased susceptibility to infections, increased cancer and heart disease incidence, and potential kidney damage. Therefore, several preclinical and clinical studies have tested methods designed to induce transplantation tolerance without lifelong IS. Still, the mechanisms of allograft tolerance are not fully elucidated. Despite significant advances in the induction of tolerogenesis in classical preclinical models, these models poorly recapitulate the immune responses in patients. Various innovative human organ-on-a-chip (OoC) models mimicking in vivo organ structures and functions have been developed, but they have never been used to model allograft rejection. Therefore, the overarching goal of this proposal is to develop a functional OoC platform for studying the mechanisms of immune tolerance by modeling allograft rejection. Liver transplants are more tolerated than transplantation of other solid organs and occasionally show spontaneous tolerance, suggesting that it would be the ideal in vitro model to study tolerance. Modeling liver allograft rejection on-a-chip requires a microfluidic device that mimics the physiological function of in vivo liver tissues, including a microvasculature. The endothelium is a crucial determinant in allograft rejection mechanisms because the donor’s endothelium is the first contact site with the recipient’s immune system. Despite recent OoC models including microvasculatures, no vascularized liver-on-a-chip (vLoC) platforms featuring perfusable organoids have been established to study T cell extravasation, migration, and infiltration into primary liver organoids. To bridge this gap, we propose to develop a functional vLoC platform that models T cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR). The purpose is to demonstrate that not all HLA mismatches (MM) and donor-specific HLA antibodies (DSA) are equally able to induce allograft rejection. First, we will develop a microfluidic-based device in which human liver organoids, blood-derived endothelial cells progenitors, and fibroblasts embedded in fibrin will be co-cultured to generate vascularized and perfusable liver organoids. Then, we will model allograft rejection by perfusing allogeneic T cells or anti-HLA antibodies through the vLoC model. TCMR and ABMR markers will be assessed and correlated with the different physicochemical characteristics of HLA MM and DSA. This novel platform can significantly impact transplant immunology research while accelerating the understanding of transplant tolerance and increasing the translation of novel tolerance induction protocols and regimens to the clinics.