CXCR4 and pulmonary arterial hypertension: Earlier studies showed that CXCL12 was elevated in plasma and CXCR4 was significantly upregulated in hypoxia-induced PAH rats, and the same trend was observed in clinical samples; pharmacological inhibition of CXCR4 reversed RV hypertrophy, pulmonary artery middle layer hypertrophy and pulmonary vascular remodeling in PAH rats (Xu et al., 2021).