CXCL12 and pulmonary arterial hypertension: Proinflammatory cytokine, like hypoxia-induced IL-6, promotes the differentiation of Th17 cells, secreting of IL-17 and IL-21, macrophage skewing, and CXCL12 releasing to regulate the hypoxia-induced proliferation of PASMCs in the pathogenesis of PAH [43].