TNF and pulmonary arterial hypertension: Several reports on lung injury have shown that MSC-EVs reduced macrophage recruitment in lung tissue, reduced macrophage expression of proinflammatory cytokines associated with the development of PAH, such as IL-6, MIP-2, and TNF-α, limited alveolar injury in animal models of acute lung injury and attenuated PAH in animal models of bronchopulmonary dysplasia (134, 214).