Noninvasive two-photon imaging of pancreatic islet graft rejection in the eye

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DESCRIPTION (provided by applicant): Islet cell survival after transplantation to cure type 1 diabetes is limited primarily by immune-mediated rejection. Therefore, in situ monitoring of graft rejection in real time is critical for proper intervention. Current imaging modalities lack spatial and temporal resolution and consequently immune attack of the islets is only be detected once macroscopic graft damage has occurred. The long-term goal of this application is to establish a high resolution imaging approach where immune-mediated rejection of graft tissue in live recipients can be monitored noninvasively and studied in situ. This project aims to establish pancreatic islet transplantation into the murine anterior chamber of the eye as a model for two-photon fluorescence imaging of immune rejection of transplanted allogeneic islets. The anterior chamber of the eye provides a natural body window that allows noninvasive monitoring of the very same islets longitudinally. The hypothesis is that immune-mediated intraocular rejection of islet allografts occurs despite immune privilege and can be readily imaged noninvasively in real time. For the first time, this project will enable studying in vivo early rejection in real time. It will enable the study of cellular motility and dynamics during islet allograft rejection. Pilot data provided by the applicant revealed rejection of allogeneic islets and demonstrated the strength and feasibility of imaging intraocular islet function and rejection. These data showed for the first time in vivo recruitment of individual immune cells to the graft site and active infiltration of the islet grafts. The applicant proposes the following specific aims: (1) Establish intraocular transplantation as a rejection model for transplanted pancreatic islets. The working hypothesis is that islet rejection is mediated by early and persistent inflammation and ultimately by effector T lymphocytes; and (2) Identify the cellular mechanisms of intraocular rejection of islet allografts. The working hypothesis is that the rejection process requires the close association of inflammatory cells with allospecific effector T cells in the islet grafts. It is predicted that islet cell death occurs near these cell complexes. These studies will reveal the kinetics and dynamics of immunemediated intraocular rejection of islet allografts and will provide a platform to test and refine novel and existing therapeutic regimens aimed at enhancing islet survival and long-term acceptance of grafts. Being able to monitor the fate of islet grafts in real time would enable early intervention and will address the major limitation to pancreatic islet transplantation as a therapy to cure type 1 diabetes. This proposed project allows the early detection and study of rejection providing a better understanding of the process and the ability for a timely intervention to improve islet cell survival and long-term graft acceptance.