PTGS2 and chronic obstructive pulmonary disease: Thus, our current study was performed to investigate the following hypotheses: (1) MSC treatment ameliorates inflammation through the suppression of the COX-2/PGE2 pathway in COPD; (2) MSC treatment regulates COX-2 expression through the MAPK pathway in macrophages; and (3) a cell-to-cell mechanism exists in addition to the paracrine mechanism in MSC treatment in COPD.