SMURF2 and pulmonary fibrosis: miR-15b targets the E3 ubiquitin ligase Smurf2, causing it to lose its function of ubiquitination degradation of HSP27, upregulating HSP27 expression and promoting cell migration, thus mediating the abnormally high migratory activity of fibroblasts in fibrotic lung tissues, which in turn promotes the onset and development of pulmonary fibrosis 174.