Because electroporation of bone marrow cells with the CXCR4 shRNA only affected CXCR4 expression in bone marrow cells, this finding provided direct evidence that CXCR4 is involved in regulation of bone marrow cell migration during development of pulmonary hypertension and vascular remodeling induced by hypoxia. Here, CXCR4 is linked to pulmonary arterial hypertension.