Induction of angiogenesis in triple co-cultures of ECs, pericytes and astrocytes. Primary cells were co-cultured at a ratio of one pericyte to five ECs and to five astrocytes. Cultures were exposed to hypoxia (10%) to induce angiogenesis (A). Tube formation in triple cultures involved crosstalk between astrocytes and pericytes. White arrows point to pericytes and black arrows point to astrocytes. Photograph was taken using phase contrast at 10×. In (B) we show a close up of an astrocyte making contact with both elongating EC and pericytes. The black arrows point to astrocyte contacts with an elongating EC (left) and one of the two contacts made with a pericyte (right). Pericytes have fewer projections and are more spread out than the astrocytes.