Two ways VEGF-A builds a vessel

On page 1163, Gerhardt et al. present a mechanism to explain the function of VEGF in angiogenesis. Their findings implicate a specialized cell at the tips of vessels in guiding the growth of new sprouts, with cell mass provided by the division of different cells that lie further back.

The authors examined angiogenesis in mice retina. Retinal vessels grow by circular expansion and are thus convenient for examining newly sprouting vessels. Past images have suggested that the ends of growing vessels harbor an unusual tip structure. In this article, the authors show that this highly polarized tip cell is specialized to respond uniquely to VEGF-A isoforms. Tip cells extended long filopodia that followed along tracks of astrocyte cells. The filopodia used the VEGFR2 receptor to sense a gradient of VEGF-A, which is secreted by the astrocytes...