CELLULAR AND MOLECULAR MECHANISMS OF PULMONARY VASCULAR REMODELING

In many organs and tissues, the cellular response to injury is associa ted with a reiteration of specific developmental processes. Studies ha ve shown that, in response to injury, vascular wall cells in adult org anisms express genes or gene products characteristic of earlier develo pmental states. Other genes, expressed preferentially in adult cells i n vivo, are down-regulated following injurious stimuli. Complicating m atters, however, are recent observations demonstrating that the vascul ar wall is comprised of phenotypically heterogeneous subpopulations of endothelial cells, smooth muscle cells, and fibroblasts. It is unclea r how specific subsets of cells respond to injury and thus contribute to the vascular remodeling that characterizes chronic pulmonary hypert ension. This review discusses vascular development in the lung and the cellular responses occurring in pulmonary hypertension; special atten tion is given to heterogeneity of responses within cell populations an d reiteration of developmental processes.