Vasculature is a key element of haematogenous metastatic progression. However, our current understanding of cell-cell interactions during the key steps of this process (intravasation, transit & extravasation) is underdeveloped. This is largely due to the technical difficulties associated with studying these dynamic processes in static disease models. In order to address this issue, we propose the development of a perfusable blood vessel network in vitro which can be co-cultured with cancer tissue ex vivo to facilitate study of these cell-cell interactions. Towards this goal, we have successfully developed human blood vessel organoids from human induced pluripotent stem cells.
Human induced pluripotent stem cells (iPSC) are aggregated into embryoid bodies in suspension culture. These embryoid bodies are exposed to an optimized chemical cocktail which promotes first mesoderm induction, and then vascular lineage commitment. These aggregates are then embedded in a gel matrix to facilitate sprouting of blood vessels from the aggregates into the gel. Fixed blood vessel networks undergo immunofluorescence staining and are imaged on a confocal fluorescence microscope.
Interference phase contrast microscopy of blood vessel networks show morphological features which are consistent with angiogenic tip cells. Confocal microscopy of blood vessel networks following immunofluorescence staining demonstrates the presence of differentiated CD31+ endothelial cells and PDGFR-β+ pericytes. These endothelial cells and pericytes have spontaneously assembled into tube-like structures in vitro. These results suggest successful differentiation of human induced pluripotent stem cells into mature blood vessel networks.