Optical imaging of the adoptive transfer of human endothelial cells in mice using anti-human CD31 monoclonal antibody

Purpose. The development of endothelium-specific imaging agents capable of specific binding to human cells under the conditions of flow for the needs of regenerative medicine and cancer research. The goal of the study was testing the feasibility of optical imaging of human endothelial cells implanted in mice. Methods. Mouse model of adoptive human endothelial cell transfer was obtained by implanting cells in Matrigel matrix in subcutaneous space (Kang, Torres, Wald, Weissleder, and Bogdanov, Jr., Targeted imaging of human endothelial-specific marker in a model of adoptive cell transfer. Lab. Invest. 86: 599609, 2006). Several endothelium-specific proteins were labeled with near-infrared fluorochrome (Cy5.5) and tested in vitro. Fluorescence imaging using anti-human CD31 antibody was performed in vivo. The obtained results were corroborated by using fluorescence microscopy of tissue sections. Results. We determined that monoclonal anti-human CD31 antibodies labeled with Cy5.5 were efficiently binding to human endothelial cells and were not subject to rapid endocytosis. We further demonstrated that specific near-infrared optical imaging signal was present only in Matrigel implants seeded with human endothelium cells and was absent from control Matrigel implants. Histology showed staining of cells lining vessels and revealed the formation of branched networks of CD31-positive cells. Conclusions. Anti-human CD31 antibodies tagged with near-infrared fluorochromes can be used for detection of perfused blood vessels harboring human endothelial cells in animal models of adoptive transfer.