Vascular remodeling in the circulations of the lung.

The lung is unique in its double sources of perfusion from the pulmonary and systemic circulations. One striking difference between the two circulations is the capacity for angiogenesis. The bronchial circulation has a capacity that seems quite similar to all systemic arteries, whereas the pulmonary circulation seems relatively inert in this regard. Extra-alveolar pulmonary arteries can grow somewhat in length, and septal capillaries seem to have the capability of reforming, but these processes do not seem to occur with nearly the same intensity associated with the bronchial arteries. In this review, we emphasize these differences between the two circulations of the lung, anticipating that future research will allow more focused probing into the molecular signaling that regulates the novel mechanistic and pathological pathways of each.