The use of stem cells for the repair of cardiac tissue in ischemic heart disease

DMPE-PEG scaffold binding with TGF-β1 receptor enhances cardiomyogenic differentiation of adipose-derived stem cells

Background

Heart failure has become a global health problem with increasing incidences worldwide. Traditional pharmacological treatments can delay but cannot reverse the underlying disease processes. The clinical application of myocardial tissue engineering represents a promising strategy because it features cell-based replacement therapies that replace partially or fully damaged cardiac tissues with in vitro-generated tissue equivalents. However, the effectiveness of this therapy is limited by poor viability and differentiation of the grafted cells. This limitation could be overcome by rapidly increasing the numbers of functional cardiomyocytes. In this study, we aimed to obtain functional myocardial tissue engineering seed cells with high proliferation and differentiation rates by combining 1,2-dimyristoyl-sn-glycero-3-phosphoethan-olamine-polyethylene glycol (DMPE-PEG) and recombinant transforming growth factor-β1 receptor I (rTGF-β1 RI), followed by binding to human adipose-derived stromal cells (hADSCs).

Methods

To induce higher expression level of TGF-β1 RI, DMPE-PEG was inoculated with rTGF-β1 RI to modify the surface of hADSCs. The differentiation ability and morphological characteristics of the modified hADSCs were examined in vitro and in vivo.

Results

The caridiomyocartic differentiation ability of TGF-β1 RI-modified hADSCs was significantly enhanced, as indicated by elevated expression levels of the cardiac markers cardiac troponin T (cTnT) and α-smooth muscle actin (SMA) via increased phosphorylation of the Smad signaling pathway-related proteins.

Conclusion

Our findings provide new insights into stem cell transplantation therapy in myocardial tissue engineering.

Differentiation of Bone Marrow Mesenchymal Stem Cells to Cardiomyocyte-Like Cells Is Regulated by the Combined Low Dose Treatment of Transforming Growth Factor-β1 and 5-Azacytidine

Bone marrow mesenchymal stem cells (BMMSCs) are used in cardiac tissue engineering for the regeneration of diseased hearts. We examined the differentiation of rat BMMSCs into cardiomyocyte-like cells when induced with a combined low dose treatment of transforming growth factor-β1 (TGF-β1) and 5-azacytidine (5-AZA). Results showed that cell proliferation in the combined low dose treatment group of TGF-β1 and 5-AZA was increased compared with the TGF-β1 group or the 5-AZA group. The cell apoptosis was relieved by combined TGF-β1 and 5-AZA treatment compared to 5-AZA treatment alone. The number of cells positive for myosin heavy chain, connexin-43, α-actin, and troponin I in the combined treatment group was higher than those observed in the TGF-β1 group or the 5-AZA group. Moreover, the combined low dose treatment group of TGF-β1 and 5-AZA reveals the strongest expression of troponin I, α-actin, and phosphorylated extracellular signal-regulated protein kinases 1 and 2 (p-ErK1/2) among the treatment groups. These results suggest that the combined low dose treatment of TGF-β1 and 5-AZA can improve the differentiation potential of rat BMMSCs into cardiomyocyte-like cells and alleviate cell damage effects in vitro. The mechanism that is involved in influencing differentiation may be associated with p-ErK1/2.

CX43 change in LPS preconditioning against apoptosis of mesenchymal stem cells induced by hypoxia and serum deprivation is associated with ERK signaling pathway

This study was designed to investigate the effect and mechanism of lipopolysaccharide (LPS) preconditioning on survival and connexin 43 (CX43) expression in rat bone marrow mesenchymal stem cells (bMSCs) under hypoxia and serum deprivation (Hypoxia/SD) conditions. Whole marrow cells were obtained from the femora and tibiae of SD rats, and bMSCs were isolated by density gradient centrifugation and attachment culture. Surface antigens were determined by FACS before the experiment using antibodies conjugated directly against anti-rat CD34, anti-CD45, anti-CD29, and anti-CD44. Passage 3 bMSCs were used for all experiments. The effect of LPS preconditioning on bMSCs apoptosis in response to Hypoxia/SD was investigated by an Annexin V-FITC/PI binding assay and a mitochondrial membrane potential (△Ψm) assay. Cyc-c released into the cytosol from mitochondria and CX43 in bMSCs was determined by Western blot before and after LPS preconditioning. Subsequently, extracellular signal-regulated kinase (ERK) was inhibited with PD98059 to analyze the role of ERK in modulating CX43 expression after LPS preconditioning. The bMSCs surface antigen profiles obtained by flow cytometry were positive for CD29 and CD44 and negative for CD34 and CD45. The Hypoxia/SD conditions induced significant apoptosis of bMSCs. Compared with the Hypoxia/SD group, cells treated with LPS prevented △Ψm from falling significantly. LPS inhibited Hypoxia/SD-induced Cyc-c release. These results were consistent with the total analysis of apoptosis of MSCs. Compared with the control group, the level of CX43 expression in the Hypoxia/SD group and LPS + Hypoxia/SD group decreased significantly at each time point. The level of CX43 expression in the Hypoxia/SD group was lower than that in the LPS + Hypoxia/SD group, while the difference was not significant between the PD98059 + LPS + Hypoxia/SD group and the PD98059 + Hypoxia/SD group (P > 0.05). Compared with the LPS + Hypoxia/SD group, CX43 level in the PD98059 + LPS + Hypoxia/SD group and PD98059 + Hypoxia/SD group decreased significantly (P < 0.05). These results demonstrated that Hypoxia/SD conditions could induce apoptosis of bMSCs markedly. Low-dose LPS preconditioning may preserve the mitochondrial function by maintaining the mitochondrial transmembrane potential and inhibiting Cyc-c release in Hypoxia/SD-induced bMSCs apoptosis. LPS preconditioning also had a stabilizing effect on the cell membrane by inhibiting the decrease of CX43, and this modulating mechanism may be related to the ERK signaling pathway.

AvidinOX&#x2122; for tissue targeted delivery of biotinylated cells

AvidinOX™, a product containing aldehyde groups, generated by ligand-assisted sugar oxidation of avidin by sodium periodate, maintains the capacity to bind biotin with very high affinity and exhibits the property to chemically link cellular and tissue proteins through Schiff's base formation thus residing in tissues for weeks. In recent studies, we have shown that AvidinOX exhibits much higher persistency in the skeletal muscle than native avidin. The aim of the present study is to evaluate whether AvidinOX-biotin interaction might be exploited to target biotinylated cells to an AvidinOX pre-treated muscle. To accomplish this we performed the following experiments: 1) The proliferation and differentiation properties of biotinylated C2C12 myoblasts were tested in vitro upon linkage to AvidinOX; 2) Bone marrow-derived cells (BMDC) were isolated from GFP positive transgenic mice [strain C57 BL/6-tg (UBC-GFP)] and after biotinylation (bBMDC) were intravenously administered to naive and MAVA+ (Mouse anti Avidin Antibody) C57/B6 mice previously injected with AvidinOX in a tibial muscle (TM). Localization efficiency of GFP+ bBMDC was evaluated on serial sections of the AvidinOX- and vehicle-treated (contra lateral limb) TM, 5 days after transplantation. Results show that biotinylated C2C12 cells, once linked to AvidinOX, maintain their proliferation and differentiation capacity, in vitro. Intravenous injection of biotinylated GFP+ bone marrow-derived cells leads to their specific and efficient localization in the AvidinOX-pre-treated, but not contra lateral muscle of both naive and MAVA+ mice. The present data suggest a potential use of AvidinOX to improve tissue targeted delivery of biotinylated cells.