Platelet-derived growth factor-AB promotes the generation of adult bone marrow-derived cardiac myocytes.
(25/4797)
The directed generation of cardiac myocytes from endogenous stem cells offers the potential for novel therapies for cardiovascular disease. To facilitate the development of such approaches, we sought to identify and exploit the pathways directing the generation of cardiac myocytes from adult rodent bone marrow cells (BMCs). In vitro cultures supporting the spontaneous generation of functional cardiac myocytes from murine BMCs demonstrated induced expression of platelet-derived growth factor (PDGF)-A and -B isoforms with alpha- and beta-myosin heavy chains as well as connexin43. Supplementation of PDGF-AB speeded the kinetics of myocyte development in culture by 2-fold. In a rat heart, myocardial infarction pretreatment model PDGF-AB also promoted the derivation of cardiac myocytes from BMCs, resulting in a significantly greater number of islands of cardiac myocyte bundles within the myocardial infarction scar compared with other treatment groups. However, gap junctions were detected only between the cardiac myocytes receiving BMCs alone, but not BMCs injected with PDGF-AB. Echocardiography and exercise testing revealed that the functional improvement of hearts treated with the combination of BMCs and PDGF-AB was no greater than with injections of BMCs or PDGF-AB alone. These studies demonstrated that PDGF-AB enhances the generation of BMC-derived cardiac myocytes in rodent hearts, but suggest that alterations in cellular patterning may limit the functional benefit from the combined injection of PDGF-AB and BMCs. Strategies based on the synergistic interactions of PDGF-AB and endogenous stem cells will need to maintain cellular patterning in order to promote the restoration of cardiac function after acute coronary occlusion. (+info)
Gene targeting in stem cells from individuals with osteogenesis imperfecta.
(26/4797)
Adult stem cells offer the potential to treat many diseases through a combination of ex vivo genetic manipulation and autologous transplantation. Mesenchymal stem cells (MSCs, also referred to as marrow stromal cells) are adult stem cells that can be isolated as proliferating, adherent cells from bones. MSCs can differentiate into multiple cell types present in several tissues, including bone, fat, cartilage, and muscle, making them ideal candidates for a variety of cell-based therapies. Here, we have used adeno-associated virus vectors to disrupt dominant-negative mutant COL1A1 collagen genes in MSCs from individuals with the brittle bone disorder osteogenesis imperfecta, demonstrating successful gene targeting in adult human stem cells. (+info)
Increase of circulating endothelial progenitor cells in patients with coronary artery disease after exercise-induced ischemia.
(27/4797)
OBJECTIVE: The concept of neovascularization in response to tissue ischemia has been extended by the finding of postnatal vasculogenesis initiated by endothelial progenitor cells (EPCs). The aim of this study was to analyze whether a maximal stress test in patients with coronary artery disease (CAD) increases the number of circulating EPCs. METHODS AND RESULTS: Blood concentration of EPCs was analyzed by FACS and cell culture assay in CAD patients with (n=16) or without (n=12) exercise-induced myocardial ischemia and in healthy subjects (n=11) for up to 144 hours after maximal stress test. Plasma concentrations of vascular endothelial growth factor (VEGF), basic fibroblast growth factor, tumor necrosis factor-alpha, and granulocyte macrophage-colony stimulating factor were determined by ELISA. EPCs increased significantly in ischemic patients, with a maximum after 24 to 48 hours (cell culture: 3.3+/-0.5-fold increase; FACS: 3.1+/-0.6-fold increase) and returned to baseline within 72 hour. In nonischemic patients and healthy subjects, no EPC increase was detectable. VEGF levels in ischemic patients increased significantly after 2 to 6 hours (maximum after 2 hours; 4.0+/-1.1-fold increase) and no change was observed in nonischemic patients and healthy subjects; DeltaVEGF and DeltaEPC correlated significantly (r=0.66). CONCLUSIONS: Patients with symptomatic CAD respond to a single episode of exercise-induced myocardial ischemia with a time-dependent increase in circulating EPCs. This increase may be related to and preceded by an increase in plasma VEGF. (+info)
Human mesenchymal stem cells as a gene delivery system to create cardiac pacemakers.
(28/4797)
We tested the ability of human mesenchymal stem cells (hMSCs) to deliver a biological pacemaker to the heart. hMSCs transfected with a cardiac pacemaker gene, mHCN2, by electroporation expressed high levels of Cs+-sensitive current (31.1+/-3.8 pA/pF at -150 mV) activating in the diastolic potential range with reversal potential of -37.5+/-1.0 mV, confirming the expressed current as I(f)-like. The expressed current responded to isoproterenol with an 11-mV positive shift in activation. Acetylcholine had no direct effect, but in the presence of isoproterenol, shifted activation 15 mV negative. Transfected hMSCs influenced beating rate in vitro when plated onto a localized region of a coverslip and overlaid with neonatal rat ventricular myocytes. The coculture beating rate was 93+/-16 bpm when hMSCs were transfected with control plasmid (expressing only EGFP) and 161+/-4 bpm when hMSCs were expressing both EGFP+mHCN2 (P<0.05). We next injected 10(6) hMSCs transfected with either control plasmid or mHCN2 gene construct subepicardially in the canine left ventricular wall in situ. During sinus arrest, all control (EGFP) hearts had spontaneous rhythms (45+/-1 bpm, 2 of right-sided origin and 2 of left). In the EGFP+mHCN2 group, 5 of 6 animals developed spontaneous rhythms of left-sided origin (rate=61+/-5 bpm; P<0.05). Moreover, immunostaining of the injected regions demonstrated the presence of hMSCs forming gap junctions with adjacent myocytes. These findings demonstrate that genetically modified hMSCs can express functional HCN2 channels in vitro and in vivo, mimicking overexpression of HCN2 genes in cardiac myocytes, and represent a novel delivery system for pacemaker genes into the heart or other electrical syncytia. (+info)
Rosiglitazone facilitates angiogenic progenitor cell differentiation toward endothelial lineage: a new paradigm in glitazone pleiotropy.
(29/4797)
BACKGROUND: Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists inhibit vascular smooth muscle proliferation and migration and improve endothelial function. It is unknown whether PPAR-gamma agonists favorably modulate bone marrow (BM)-derived angiogenic progenitor cells (APCs) to promote endothelial lineage differentiation and early reendothelialization after vascular intervention. METHODS AND RESULTS: C57/BL6 mice, treated with or without rosiglitazone (8 mg/kg per day), a PPAR-gamma agonist, underwent femoral angioplasty. Rosiglitazone treatment attenuated neointimal formation (intima/media ratio: 0.98+/-0.12 [rosiglitazone] versus 3.1+/-0.5 [control]; P<0.001; n=10 per group). Using a BM transplantation model, we identified that 58+/-12% of the cells within the neointima at 4 weeks were derived from the BM. Pure endothelial marker-positive, pure alpha-smooth muscle actin (alphaSMA)-positive, or double-positive APCs could be found both in mouse BM and in human peripheral blood after culture in conditional medium enriched with vascular endothelial growth factor. Rosiglitazone caused a 6-fold (P<0.001) increase in colony formation by human endothelial progenitor cells, promoted the differentiation of APCs toward the endothelial lineage in mouse BM in vivo (0.66+/-0.06% [control] to 0.95+/-0.08% [rosiglitazone]; P<0.05) and in human peripheral blood in vitro (13.2+/-1.5% [control] to 28.4+/-3.3% [rosiglitazone]; P<0.05), and inhibited the differentiation toward the smooth muscle cell lineage. Within the neointima, rosiglitazone also stimulated APCs to differentiate into mature endothelial cells and caused earlier reendothelialization compared with controls (31+/-5 versus 8+/-2 CD31-positive cells per millimeter of neointimal surface on day 14; P<0.01). CONCLUSIONS: Similar to embryonic stem cell-derived progenitors, the adult BM and peripheral blood harbor APCs that are at least bipotential and able to differentiate into endothelial and smooth muscle lineages. The PPAR-gamma agonist rosiglitazone promotes the differentiation of these APCs toward the endothelial lineage and attenuates restenosis after angioplasty. (+info)
Endothelial progenitor cells: more than an inflammatory response?
(30/4797)
The formation of new capillaries (angiogenesis) may be of clinical importance in facilitating reperfusion and regeneration of hibernating cardiac tissue after myocardial infarction and in microvascular ischemia. Evidence is accumulating that as part of the response to hypoxia, bone marrow-derived circulating endothelial progenitor cells (CEPs) are mobilized and subsequently differentiate into proper endothelial cells. There are also indications that such CEPs can facilitate endothelial repair and angiogenesis in vivo. It is not clear yet, however, whether these CEPs are essential for these adaptive processes or what the relative contribution of CEP is compared with that of other mononuclear inflammatory cells that are mobilized to areas of ischemia. Moreover, there are still many uncertainties about how cardiovascular risk factors alter CEP function. Particularly when therapeutically mobilizing CEPs, a further understanding of this issue is essential to assess the risk of potentially harmful side effects of altered CEP function. (+info)
Enumeration and phenotypic characterization of synovial fluid multipotential mesenchymal progenitor cells in inflammatory and degenerative arthritis.
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OBJECTIVE: To evaluate synovial fluid (SF) for the presence of mesenchymal progenitor cells (MPCs), to compare SF MPCs with bone marrow (BM) MPCs, and to enumerate these cells in both inflammatory arthritis and osteoarthritis (OA). METHODS: SF from 100 patients with arthritis (53 rheumatoid arthritis [RA], 20 OA, and 27 other arthropathies) was evaluated. To establish multipotentiality, polyclonal and single cell-derived cultures of SF fibroblasts were examined by standard and quantitative differentiation assays. Their phenotype before and after expansion was determined by multiparameter flow cytometry. A colony-forming unit-fibroblast assay was used for SF MPC enumeration. RESULTS: Regardless of the nature of the arthritis, both polyclonal and single cell-derived cultures of SF fibroblasts possessed trilineage mesenchymal differentiation potentials. The number of MPCs in a milliliter of SF was higher in OA (median 37) than in RA (median 2) (P < 0.00001). No significant differences in MPC numbers were found between early and established RA (median 3 and 2 cells/ml, respectively). Culture-expanded SF and BM MPCs had the same phenotype (negative for CD45 and positive for D7-FIB, CD13, CD105, CD55, and CD10). Rare, uncultured SF fibroblasts were CD45(low) and expressed low-affinity nerve growth factor receptor, similar to in vivo BM MPCs. CONCLUSION: Our findings prove the presence of rare tripotential MPCs, at the single-cell level, in the SF of patients with arthritis. SF MPCs are clonogenic and multipotential fibroblasts that, despite the pathologic environment within a diseased joint, have a phenotype similar to that of uncultured BM MPCs. The higher prevalence of MPCs in OA SF suggests their likely origin from disrupted joint structures. These findings could determine the role of MPCs in the pathogenesis of inflammatory arthritis, together with their role in attempted joint regeneration in degenerative arthritis, which has yet to be established. (+info)
Human mesenchymal stem cells form Purkinje fibers in fetal sheep heart.
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BACKGROUND: We have investigated the usefulness of a model of cardiac development in a large mammal, sheep, for studies of engraftment of human stem cells in the heart. METHODS AND RESULTS: Adult and fetal human mesenchymal stem cells were injected intraperitoneally into sheep fetuses in utero. Hearts at late fetal development were analyzed for engraftment of human cells. The majority of the engrafted cells of human origin formed segments of Purkinje fibers containing exclusively human cells. There were no differences in engraftment of human mesenchymal stem cells from adult bone marrow, fetal brain, and fetal liver. On average, 43.2% of the total Purkinje fibers in random areas (n=11) of both ventricles were of human origin. In contrast, approximately 0.01% of cardiomyocytes were of human origin. CONCLUSIONS: Human mesenchymal stem cells preferentially engraft at high levels in the ventricular conduction system during fetal development in sheep. These findings raise the possibility that stem cells contribute to normal development of the fetal heart. (+info)