We hypothesized that inhibition of systemic CXCR4 through administration of AMD3100 will inhibit hypoxia-induced pulmonary hypertension and vascular remodeling in rats and that specific inhibition of the CXCR4 in bone marrow cells also will impact development of pulmonary hypertension and vascular remodeling induced by chronic hypoxia. Here, CXCR4 is linked to pulmonary arterial hypertension.