Senescence of lung mesenchymal stem cells of preterm infants by cyclic stretch and hyperoxia via p21

Phenotype distortion of lung resident mesenchymal stem cells (MSC) in preterm infants is a hallmark event in the pathogenesis of bronchopulmonary dysplasia. Here, we evaluated the impact of cyclic mechanical stretch (CMS) and hyperoxia (HOX). The negative action of HOX on proliferation and cell death was more pronounced at 80% than at 40%. While the impact of CMS alone was modest, CMS plus HOX displayed the strongest effect sizes. Exposure to CMS and/or HOX induced the downregulation of PDGFRα and cellular senescence preceded by p21 accumulation. p21 interference interfered with cellular senescence and resulted in aggravated cell death arguing for a pro-survival mechanism. HOX 40% and limited exposure to HOX 80% prevailed a reversible phenotype with reuptake of proliferation while prolonged exposure to HOX 80% resulted in definite MSC growth arrest. Our mechanistic data explain how HOX and CMS induce the effects on MSC phenotype disruption. The results are congruent with the clinical observation that preterm infants requiring supplemental oxygen plus mechanical ventilation are at particular risk for BPD. While inhibiting p21 is not a feasible approach, limiting the duration and magnitude of the exposures is promising.