Intravenously Delivered Mesenchymal Stem Cells: Systemic Anti-Inflammatory Effects Improve Left Ventricular Dysfunction in Acute Myocardial Infarction and Ischemic Cardiomyopathy.

RATIONALE: Virtually all mesenchymal stem cell (MSC) studies assume that therapeutic effects accrue from local myocardial effects of engrafted MSCs. Because few intravenously administered MSCs engraft in the myocardium, studies have mainly utilized direct myocardial delivery. We adopted a different paradigm. OBJECTIVE: To test whether intravenously administered MSCs reduce left ventricular (LV) dysfunction both post-acute myocardial infarction and in ischemic cardiomyopathy and that these effects are caused, at least partly, by systemic anti-inflammatory activities. METHODS AND RESULTS: Mice underwent 45 minutes of left anterior descending artery occlusion. Human MSCs, grown chronically at 5% O2, were administered intravenously. LV function was assessed by serial echocardiography, 2,3,5-triphenyltetrazolium chloride staining determined infarct size, and fluorescence-activated cell sorting assessed cell composition. Fluorescent and radiolabeled MSCs (1×106) were injected 24 hours post-myocardial infarction and homed to regions of myocardial injury; however, the myocardium contained only a small proportion of total MSCs. Mice received 2×106 MSCs or saline intravenously 24 hours post-myocardial infarction (n=16 per group). At day 21, we harvested blood and spleens for fluorescence-activated cell sorting and hearts for 2,3,5-triphenyltetrazolium chloride staining. Adverse LV remodeling and deteriorating LV ejection fraction occurred in control mice with large infarcts (≥25% LV). Intravenous MSCs eliminated the progressive deterioration in LV end-diastolic volume and LV end-systolic volume. MSCs significantly decreased natural killer cells in the heart and spleen and neutrophils in the heart. Specific natural killer cell depletion 24 hours pre-acute myocardial infarction significantly improved infarct size, LV ejection fraction, and adverse LV remodeling, changes associated with decreased neutrophils in the heart. In an ischemic cardiomyopathy model, mice 4 weeks post-myocardial infarction were randomized to tail-vein injection of 2×106 MSCs, with injection repeated at week 3 (n=16) versus PBS control (n=16). MSCs significantly increased LV ejection fraction and decreased LV end-systolic volume. CONCLUSIONS: Intravenously administered MSCs for acute myocardial infarction attenuate the progressive deterioration in LV function and adverse remodeling in mice with large infarcts, and in ischemic cardiomyopathy, they improve LV function, effects apparently modulated in part by systemic anti-inflammatory activities.

Rigidity of silicone substrates controls cell spreading and stem cell differentiation.

The dependences of spreading and differentiation of stem cells plated on hydrogel and silicone gel substrates on the rigidity and porosity of the substrates have recently been a subject of some controversy. In experiments on human mesenchymal stem cells plated on soft, medium rigidity, and hard silicone gels we show that harder gels are more osteogenic, softer gels are more adipogenic, and cell spreading areas increase with the silicone gel substrate rigidity. The results of our study indicate that substrate rigidity induces some universal cellular responses independently of the porosity or topography of the substrate.

High targeted migration of human mesenchymal stem cells grown in hypoxia is associated with enhanced activation of RhoA.

INTRODUCTION: A feature which makes stem cells promising candidates for cell therapy is their ability to migrate effectively into damaged or diseased tissues. Recent reports demonstrated the increased motility of human mesenchymal stem cells (hMSC) grown under hypoxic conditions compared to normoxic cells. However, the directional migration of hMSC cultured in hypoxia has not been investigated. In this study we examined the in vitro transmembrane migration of hMSC permanently cultured in hypoxia in response to various cytokines. We also studied the involvement of RhoA, a molecule believed to play an essential role in the migration of MSC via reorganization of the cytoskeleton. METHODS: We compared the directional migration of human hMSCs grown permanently under normal (21%, normoxic) and low O2 (5%, hypoxic) conditions until passage 4 using an in vitro transmembrane migration assay. A series of 17 cytokines was used to induce chemotaxis. We also compared the level of GTP-bound RhoA in the cell extracts of calpeptin-activated hypoxic and normoxic hMSC. RESULTS: We found that hMSC cultured in hypoxia demonstrate markedly higher targeted migration activity compared to normoxic cells, particularly towards wound healing cytokines, including those found in ischemic and myocardial infarction. We also demonstrated for the first time that hMSC are dramatically more sensitive to activation of RhoA. CONCLUSIONS: The results of this study indicate that high directional migration of hMSCs permanently grown in hypoxia is associated with the enhanced activation of RhoA. The enhanced migratory capacity of hypoxic hMSC would further suggest their potential advantages for clinical applications.

Comparative interface metrics for metal-free monolayer-based dye-sensitized solar cells.

The first quantitative comparison between self-assembled monolayers of homologous carboxylate- and phosphonate-terminated organic dyes that are of use in dye-sensitized solar cells (DSSCs) is reported. (Cyanovinyl)phosphonate-terminated oligothiophenes and (cyanovinyl)carboxylate-terminated oligothiophenes were synthesized on TiO(2) thin film electrodes. Structurally analogous organics were compared for the effect of the anchoring groups on photochemical properties in solution as measured by UV/vis spectroscopy and for reactivity with the electrode surface. Monolayers were grown on the TiO(2) electrodes either by "tethering by aggregation and growth" (T-BAG) or by solution dipping. Surface roughness and homogeneity, elemental composition, and thickness of the monolayers were evaluated by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and ellipsometry. Molecular loadings for each monolayer on TiO(2) were quantified by quartz crystal microgravimetry (QCM), and the stability of bonding between each class of dyes and the TiO(2) was evaluated by measuring desorption, also by QCM; the carboxylates underwent significant dissociation in aqueous media but the phosphonates did not. DSSCs were prepared from each congener and from simple oligothiophene phosphonates to determine the effect of the cyanovinyl group on device behavior; all DSSCs were studied under irradiation from a AM 1.5G solar light source; the effect of cyanovinyl group termination was comparable to that of adding a thiophene moiety, and the DSSC using a self-assembled monolayer of (sexithiophene)phosphonate (6TP) had total power conversion efficiency (η) of ca. 5%.