Bone marrow mesenchymal stem cells ameliorate hepatic ischemia/reperfusion injuries via inactivation of the MEK/ERK signaling pathway in rats.

BACKGROUND: Primary graft dysfunction or nonfunction after liver transplantation, which is usually caused by ischemia/reperfusion injury (IRI), is a serious clinical problem. Although bone marrow mesenchymal stem cells (MSCs) have shown great potential in cell therapy for IRI in several organs, the mechanism(s) by which MSCs offer protection is unclear. METHODS: In the present study, we injected MSCs systemically via the tail vein in the rat model of 70% hepatic IRI and measured the biochemical and pathologic alterations to evaluate the therapeutic effect of MSC transplantation. Concurrently, H(2)O(2) was used in vitro to mimic oxidative injury and to induce apoptosis in the human normal liver cell line LO2 to evaluate the protective effects of mesenchymal stem cell conditioned medium (MSC-CM) on LO2 cells. RESULTS: The systemic infusion of MSCs led to a significant prevention of liver enzyme release and an improvement in the histology of the acutely injured liver. In vitro assays demonstrated that MSC-CM promoted hepatocyte proliferation and had a direct inhibitory effect on hepatocyte apoptosis induced by H(2)O(2). In addition, we demonstrated that the prevention of MEK/ERK pathway activation played a pivotal role in the protection. CONCLUSIONS: These data suggest that MSC may represent a potential therapeutic strategy to alleviate hepatic ischemia/reperfusion injuries after liver transplantation via inactivation of the MEK/ERK signaling pathway.

RUNX3 plays an important role in As2O3­induced apoptosis and allows cells to overcome MSC­mediated drug resistance.

The interaction between bone marrow stromal cells and leukemia cells is critical for the persistence and progression of leukemia, and this interaction may account for residual disease. However, the link between leukemia cells and their environment is still poorly understood. In our study, runt­related transcription factor 3 (RUNX3) was identified as a novel target gene affected by As2O3 and involved in mesenchymal stem cell (MSC)­mediated protection of leukemia cells from As2O3­induced apoptosis. We observed induction of RUNX3 expression and the translocation of RUNX3 into the nucleus after As2O3 treatment in leukemia cells. In K562 chronic myeloid leukemia cells, downregulation of endogenous RUNX3 compromised As2O3­induced growth inhibition, cell cycle arrest, and apoptosis. In the presence of MSC, As2O3­induced expression of RUNX3 was reduced significantly and this reduction was modulated by CXCL12/CXCR4 signaling. Furthermore, overexpression of RUNX3 restored, at least in part, the sensitivity of leukemic cells to As2O3. We conclude that RUNX3 plays an important role in As2O3­induced cellular responses and allows cells to overcome MSC­mediated drug resistance. Therefore, RUNX3 is a promising target for therapeutic approaches to overcome MSC­mediated drug resistance.

RUNX3 is involved in caspase-3-dependent apoptosis induced by a combination of 5-aza-CdR and TSA in leukaemia cell lines.

PURPOSE: Epigenetic therapy has had a significant impact on the management of haematologic malignancies. The aim of this study was to assess whether 5-aza-CdR and TSA inhibit the growth of leukaemia cells and induce caspase-3-dependent apoptosis by upregulating RUNX3 expression. METHODS: K562 and Reh cells were treated with 5-aza-CdR, TSA or both compounds. RT-PCR and Western blot analyses were used to examine the expression of RUNX3 at the mRNA and protein levels, respectively. Immunofluorescence microscopy was used to detect the cellular location of RUNX3. Additionally, after K562 cells were transfected with RUNX3, apoptosis and proliferation were studied using Annexin V staining and MTT assays. RESULTS: The expression of RUNX3 in leukaemia cell lines was markedly less than that in the controls. Demethylating drug 5-aza-CdR could induce RUNX3 expression, but the combination of TSA and 5-aza-CdR had a greater effect than did treatment with a single compound. The combination of 5-aza-CdR and TSA induced the translocation of RUNX3 from the cytoplasm into the nucleus. TSA enhanced apoptosis induced by 5-aza-CdR, and Annexin V and Hoechst 33258 staining showed that the combination induced apoptosis but not necrosis. Furthermore, apoptosis was dependent on the caspase-3 pathway. RUNX3 overexpression in K562 cells led to growth inhibition and apoptosis and potentiated the effects of 5-aza-CdR induction. CONCLUSION: RUNX3 plays an important role in leukaemia cellular functions, and the induction of RUNX3-mediated effects may contribute to the therapeutic value of combination TSA and 5-aza-CdR treatment.