Silencing P38 MAPK reduces cellular senescence in human fetal chorion trophoblast cells.

PROBLEM: Amniochorion senescence generates mechanistic signals to initiate parturition. Activation of p38 mitogen-activated kinase (MAPK) in fetal amnion cells is a key mediator of senescence as well as epithelial-mesenchymal transition (EMT) of amnion cells. However, the impact of p38 MAPK in chorion trophoblast cells (CTCs) is unclear. We tested if eliminating p38 will reduce oxidative stress (OS) induced cell fates like cellular senescence, EMT, and inflammation induced by these processes in CTCs. METHODS: p38MAPK in CTCs was silenced using CRISPR/Cas9. OS was evoked by cigarette smoke extract (CSE) exposure. EMT was evoked by transforming growth factor (TGF)-ß treatment. Cell cycle, senescence, EMT, and inflammation were analyzed. RESULTS: CSE-induced changes in the cell cycle were not seen in p38KO CTCs compared to WT cells. OS induced by CSE evoked senescence and senescence-associated secretory phenotype (SASP as indicated by IL-6 and IL-8 increase) in WT but not in p38MAPK KO CTCs. No changes were noted in HLA-G expression regardless of the status of p38MAPK. Neither CSE nor TGF-ß evoked EMT in either WT or p38 KO CTCs. CONCLUSION: Senescence and senescence-associated inflammation in human fetal CTCs are mediated by p38MAPK. Compared to amnion epithelial cells, CTCs are resistant to EMT. This refractoriness may help them to maintain the barrier functions at the choriodecidual interface.

Stress signaler p38 mitogen-activated kinase activation: a cause for concern?

Oxidative stress (OS) induced activation of p38 mitogen-activated kinase (MAPK) and cell fate from p38 signaling was tested using the human fetal membrane's amnion epithelial cells (AEC). We created p38 KO AEC using the CRISPR/Cas9 approach and tested cell fate in response to OS on an AEC-free fetal membrane extracellular matrix (ECM). Screening using image CyTOF indicated OS causing epithelial-mesenchymal transition (EMT). Further testing revealed p38 deficiency prevented AEC senescence, EMT, cell migration, and inflammation. To functionally validate in vitro findings, fetal membrane-specific conditional KO (cKO) mice were developed by injecting Cre-recombinase encoded exosomes intra-amniotically into p38αloxP/loxP mice. Amnion membranes from p38 cKO mice had reduced senescence, EMT, and increased anti-inflammatory IL-10 compared with WT animals. Our study suggested that overwhelming activation of p38 in response to OS inducing risk exposures can have an adverse impact on cells, cause cell invasion, inflammation, and ECM degradation detrimental to tissue homeostasis.