KDR and isolated hemihyperplasia: We found that both HemSCs and HemECs respond, in a similar manner to the VEGF‐A isoforms, as normal endothelial cells, wherein VEGF‐A165a activates VEGFR2 as well as downstream signalling, which is important for IH cell proliferation, and that this could be blocked with VEGF‐A165b (Figure 5A, B; see also supplementary material, Figure S9).