CXCR4 and pulmonary arterial hypertension: We found that hypoxia-induced pulmonary hypertension was significantly decreased in the rats transplanted with CXCR4 shRNA bone marrow cells, showing decreased mean pulmonary artery pressure (Figure 3A) and decreased ratio of RV/(LV+S) (Figure 3B) as compared with the rats receiving scrambled shRNA in bone marrow cells or the rats injected with bone marrow cells without shRNA.