Vessel-widening by VEGF

A growth factor for blood vessels has also been touted as an inducer of lymph vessel growth. But Wirzenius et al. (page 1431) now find that, although the growth factor spurs the enlargement of existing lymph vessels, it does not induce the sprouting of new ones.

Lymph vessels are a follow-up act to blood vessels during embryogenesis. Vascular endothelial growth factor (VEGF) induces new blood vessel growth by binding to its receptor VEGFR-2 on vascular endothelial cells. VEGF-C and -D then kick off lymph vessel sprouting by binding to VEGFR-3 on lymphatic endothelial cells. But studies in mice that overexpress VEGF suggest that the two signaling pathways are not completely segregated. The abnormally large lymph vessels in these mice imply that VEGF somehow controls lymph vessel enlargement as well.

The...