Defining the role of mesenchymal stromal cells on the regulation of matrix metalloproteinases in skeletal muscle cells

Recent studies indicate that mesenchymal stromal cell (MSC) transplantation improves healing of injured and diseased skeletal muscle, although the mechanisms of benefit are poorly understood. In the present study, we investigated whether MSCs and/or their trophic factors were able to regulate matrix metalloproteinase (MMP) expression and activity in different cells of the muscle tissue. MSCs in co-culture with C2C12 cells or their conditioned medium (MSC-CM) up-regulated MMP-2 and MMP-9 expression and function in the myoblastic cells; these effects were concomitant with the down-regulation of the tissue inhibitor of metalloproteinases (TIMP)-1 and -2 and with increased cell motility. In the single muscle fiber experiments, MSC-CM administration increased MMP-2/9 expression in Pax-7⁺ satellite cells and stimulated their mobilization, differentiation and fusion. The anti-fibrotic properties of MSC-CM involved also the regulation of MMPs by skeletal fibroblasts and the inhibition of their differentiation into myofibroblasts. The treatment with SB-3CT, a potent MMP inhibitor, prevented in these cells, the decrease of α-smooth actin and type-I collagen expression induced by MSC-CM, suggesting that MSC-CM could attenuate the fibrogenic response through mechanisms mediated by MMPs. Our results indicate that growth factors and cytokines released by these cells may modulate the fibrotic response and improve the endogenous mechanisms of muscle repair/regeneration.     

LRP1 promotes synthetic phenotype of pulmonary artery smooth muscle cells in pulmonary hypertension

Pulmonary hypertension (PH) is characterized by a thickening of the distal pulmonary arteries caused by medial hypertrophy, intimal proliferation and vascular fibrosis. Low density lipoprotein receptor-related protein 1 (LRP1) maintains vascular homeostasis by mediating endocytosis of numerous ligands and by initiating and regulating signaling pathways.Here, we demonstrate the increased levels of LRP1 protein in the lungs of idiopathic pulmonary arterial hypertension (IPAH) patients, hypoxia-exposed mice, and monocrotaline-treated rats. Platelet-derived growth factor (PDGF)-BB upregulated LRP1 expression in pulmonary artery smooth muscle cells (PASMC). This effect was reversed by the PDGF-BB neutralizing antibody or the PDGF receptor antagonist. Depletion of LRP1 decreased proliferation of donor and IPAH PASMC in a β1-integrin-dependent manner. Furthermore, LRP1 silencing attenuated the expression of fibronectin and collagen I and increased the levels of α-smooth muscle actin and myocardin in donor, but not in IPAH, PASMC. In addition, smooth muscle cell (SMC)-specific LRP1 knockout augmented α-SMA expression in pulmonary vessels and reduced SMC proliferation in 3D ex vivo murine lung tissue cultures.In conclusion, our results indicate that LRP1 promotes the dedifferentiation of PASMC from a contractile to a synthetic phenotype thus suggesting its contribution to vascular remodeling in PH.     

Tanshinone IIA increases recruitment of bone marrow mesenchymal stem cells to infarct region via up-regulating stromal cell-derived factor-1/CXC chemokine receptor 4 axis in a myocardial ischemia model

Systemic administration with bone marrow mesenchymal stem cells (BMSCs) is a promising approach to cure myocardial ischemia (MI), while the efficacy of cell transplantation is limited by the low engraftment of BMSCs. Tanshinone IIA (Tan IIA) has been reported many times for the treatment of MI. Therefore, the present study was performed to investigate whether Tan IIA could increase the migration of BMSCs to ischemic region and its potential mechanisms. In our study, we found that combination treatment with Tan IIA and BMSCs significantly alleviated the infarct size when compared with control group (31.46 ± 3.00% vs. 46.95 ± 6.51%, p < 0.05). Results of real-time PCR showed that Tanshinone IIA (Tan IIA) did increase the migration of BMSCs to ischemic region in vivo, which was correlated with cardiac function recovery after MI. Furthermore, 2 μM Tan IIA could enhance the migration capability of BMSCs in vitro (3.69-fold of control), and this enhancement could be blocked by AMD3100 (a CXC chemokine receptor 4 blocker). CXCR4, together with its specific receptor, stromal cell-derived factor-1 (SDF-1) plays a critical role in the stem cell recruitment. Our experiment indicated that Tan IIA could promote SDF-1α expression in the infarct area and enhance the CXCR4 expression of BMSCs in vitro. Therefore, we postulated that Tan IIA could increase the BMSCs migration via up-regulating SDF1/CXCR4 axis.