Non-muscle myosin II knockdown improves survival and therapeutic effects of implanted bone marrow-derived mesenchymal stem cells in lipopolysaccharide-induced acute lung injury

BACKGROUND: Bone marrow-derived mesenchymal stem cells (BMSCs) have been shown to have some beneficial effects in acute lung injury (ALI), but the therapeutic effects are limited due to apoptosis or necrosis after transplantation into injured lungs. Here, we aim to explore whether Non-muscle myosin II (NM-II) knockdown could enhance BMSCs survival and improve therapeutic effects in ALI. METHODS: MSCs, isolated from rat bone marrow, were transfected with the small interfering RNA (siRNA) targeted to NM-II mRNA by a lentivirus vector. Rats were equally randomized to four groups: the control group was given normal saline via tail vein; the other three groups underwent intratracheal lipopolysaccharide (LPS) instillation followed by administration with either normal saline, BMSCs transduced with lentivirus-enhanced green fluorescent protein (eGFP) empty vector, or BMSCs transduced with lentivirus-eGFP NM-II siRNA. Hematoxylin and eosin staining was used to evaluate lung histopathologic changes and Masson trichrome staining was used to assess lung fibrosis. The myeloperoxidase activity was also tested in lung tissues. The mRNA expression of inflammatory cytokines in lung tissues was determined via quantitative reverse transcription PCR. Sex-determining region of the Y chromosome gene expression was measured by fluorescence in situ hybridization (FISH) assay. The expression of self-renewal activity and apoptosis-associated proteins were measured by Western blot. RESULTS: Transplantation of NM-II siRNA-modified BMSCs could improve histopathological morphology, decrease inflammatory infiltrates, down-regulate the expression levels of inflammatory cytokines, and reduce pulmonary interstitial edema. NM-II siRNA-modified BMSCs showed antifibrotic properties and alleviated the degrees of pulmonary fibrosis induced by endotoxin. In addition, NM-II knockdown BMSCs showed slightly better therapeutic effect on lung inflammation when compared with control BMSCs. The beneficial effects of NM-II siRNA-modified BMSCs may be attributed to enhanced self-renewal activity and decreased apoptosis. CONCLUSIONS: NM-II knockdown could inhibit the apoptosis of implanted BMSCs in lung tissues and improve its self-renewal activity. NM-II siRNA-modified BMSCs have a slightly enhanced ability to attenuate lung injury after LPS challenge.