Myofibroblasts play a major role in scar formation during wound healing after myocardial infarction (MI). Their origin has been thought to be interstitial cardiac fibroblasts. However, the bone marrow (BM) can be a source of myofibroblasts in a number of organs after injury. We have studied the temporal, quantitative and functional role of BM-derived (BMD) myofibroblasts in myocardial scar formation. MI was induced by permanent coronary artery ligation in mice reconstituted with EGFP or pro-Col1A2 transgenic BM. In the latter, luciferase and beta-galactosidase transgene expression mirrors that of the endogenous pro-collagen 1A2 gene, which allows for functional assessment of the recruited cells. After MI, alpha-SMA-positive myofibroblasts and collagen I gradually increased in the infarct area until day 14 and remained constant afterwards. Numerous EGFP-positive BMD cells were present during the first week post-MI, and gradually decreased afterwards until day 28. Peak numbers of BMD myofibroblasts, co-expressing EGFP and alpha-SMA, were found on day 7 post-MI. An average of 21% of the BMD cells in the infarct area were myofibroblasts. These cells constituted up to 24% of all myofibroblasts present. By in vivo IVIS imaging, BMD myofibroblasts were found to be active for collagen I production and their presence was confined to the infarct area. These results show that BMD myofibroblasts participate actively in scar formation after MI.

Aims/hypothesisIndividuals with type 2 diabetes mellitus have increased rates of macrovascular disease (MVD). Endothelial progenitor cells (EPCs), circulating angiogenic cells (CACs) and smooth muscle progenitor cells (SMPCs) are suggested to play a role in the pathogenesis of MVD. The relationship between vasoregenerative EPCs or CACs and damaging SMPCs and the development of accelerated MVD in diabetes is still unknown. We tried to elucidate whether EPC, CAC and SMPC numbers and differentiation capacities in vitro differ in patients with and without diabetes or MVD.MethodsPeripheral blood was obtained from insdividuals with and without diabetes and MVD (coronary or peripheral artery disease). EPC and SMPC numbers were determined with flow cytometry. Furthermore, CAC and SMPC numbers were quantified after in vitro culture. Their in vitro differentiation capacity was investigated with real-time RT-PCR and quantitative immunofluorescence.ResultsIn diabetic patients both EPC and CAC levels were reduced (1.3-fold [p < 0.05] and 1.5-fold [p < 0.05], respectively). CAC outgrowth from diabetic patients with MVD was reduced 1.5-fold compared with diabetic patients without MVD (p < 0.05). SMPC levels were similar between diabetic patients and healthy controls. The CAC/SMPC ratio of in vitro cultured progenitor cells was reduced 2.3-fold in samples from diabetic patients (p < 0.001). The differentiation capacity of CACs and SMPCs in vitro remained similar independently of diabetes or MVD.Conclusions/interpretationThe ratio between EPCs or CACs and SMPCs is disturbed in type 2 diabetes in favour of SMPCs. This may translate into reduced vascular repair capacity, thereby promoting MVD in type 2 diabetes.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-012-2590-5) contains peer-reviewed but unedited supplementary material, which is available to authorised users.

Using several independent and validated methods, we conclude that full-length, membrane-bound Klotho is not expressed in healthy or uraemic human vascular tissue.

BackgroundDiabetes is associated with a high incidence of macrovascular disease (MVD), including peripheral and coronary artery disease. Circulating soluble-Klotho (sKlotho) is produced in the kidney and is a putative anti-aging and vasculoprotective hormone. Reduced Klotho levels may therefore increase cardiovascular risk in diabetes. We investigated if sKlotho levels are decreased in type 2 diabetes and associate with MVD in the absence of diabetic nephropathy, and whether hyperglycemia affects renal Klotho production in vitro and in vivo.MethodssKlotho levels were determined with ELISA in diabetic and non-diabetic patients with and without MVD, and healthy control subjects. Human renal tubular epithelial cells (TECs) were isolated and exposed to high glucose levels (15 and 30 mM) in vitro and Klotho levels were measured with qPCR and quantitative immunofluorescence. Klotho mRNA expression was quantified in kidneys obtained from long term (3 and 8 months) diabetic Ins2Akita mice and normoglycemic control mice.ResultsNo significant differences in sKlotho levels were observed between diabetic patients with and without MVD (527 (433–704) pg/mL, n = 35), non-diabetic MVD patients (517 (349–571) pg/mL, n = 27), and healthy control subjects (435 (346–663) pg/mL, n = 15). High glucose (15 and 30 mM) did not alter Klotho expression in TECs. Long-term hyperglycemia in diabetic Ins2Akita mice (characterized by increased HbA1c levels [12.9 ± 0.3% (3 months) and 11.3 ± 2.0% (8 months)], p < 0.05 vs. non-diabetic mice) did not affect renal Klotho mRNA expression.ConclusionsThese data indicate that sKlotho levels are not affected in type 2 diabetes patients with and without MVD. Furthermore, hyperglycemia per se does not affect renal Klotho production. As type 2 diabetes does not alter sKlotho levels, sKlotho does not seem to play a major role in the pathogenesis of MVD in type 2 diabetes.

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Percutaneous coronary intervention is widely adopted to treat patients with coronary artery disease. However, restenosis remains an unsolved clinical problem after vascular interventions. The role of the systemic and local immune response in the development of restenosis is not fully understood. Hence, the aim of the current study was to investigate the role of the human immune system on subsequent neointima formation elicited by vascular injury in a humanized mouse model. Immunodeficient NOD.Cg-PrkdcscidIL2rgtm1Wjl(NSG) mice were reconstituted with human (h)PBMCs immediately after both carotid wire and femoral cuff injury were induced in order to identify how differences in the severity of injury influenced endothelial regeneration, neointima formation, and homing of human inflammatory and progenitor cells. In contrast to non-reconstituted mice, hPBMC reconstitution reduced neointima formation after femoral cuff injury whereas hPBMCs promoted neointima formation after carotid wire injury 4 weeks after induction of injury. Neointimal endothelium and smooth muscle cells in the injured arteries were of mouse origin. Our results indicate that the immune system may differentially respond to arterial injury depending on the severity of injury, which may also be influenced by the intrinsic properties of the arteries themselves, resulting in either minimal or aggravated neointima formation.

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Background Individuals with type 2 diabetes mellitus (T2DM) have an increased risk for developing macrovascular disease (MVD) manifested by atherosclerosis. Phenotypically and functionally different monocyte subsets (classical; CD14++CD16−, non-classical; CD14+CD16++, and intermediate; CD14++CD16+) including pro-angiogenic monocytes expressing Tie2 (TEMs) can be identified. Here we investigated monocyte heterogeneity and its association with T2DM and MVD. Methods Individuals with (N = 51) and without (N = 56) T2DM were recruited and allocated to "non-MVD" or "with MVD" (i.e., peripheral or coronary artery disease) subgroups. Blood monocyte subsets were quantified based on CD14, CD16 and Tie2 expression levels. Plasma levels of Tie2-ligands angiopoietin-1 and angiopoietin-2 were determined using ELISA. Carotid endarterectomy samples from individuals with (N = 24) and without (N = 22) T2DM were stained for intraplaque CD68+ macrophages (inflammation) and CD34+ (angiogenesis), as plaque vulnerability markers. Results Monocyte counts were similar between individuals with T2DM and healthy controls (non-diabetic, non-MVD). Non-classical monocytes were reduced (p < 0.05) in T2DM, whereas the percentage of TEMs within the intermediate subset was increased (p < 0.05). T2DM was associated with increased angiopoietin-1 (p < 0.05) and angiopoietin-2 (p = 0.0001) levels. Angiopoietin-2 levels were higher in T2DM individuals with MVD compared with non-MVD (p < 0.01). Endarterectomized plaques showed no differences in macrophage influx and microvessel number between individuals with and without T2DM. Conclusions Monocyte subset distribution is altered in T2DM with reduced non-classical monocytes and increased TEM percentage in the intermediate monocyte subset. Increased angiopoietin-2 levels together with increased frequency of TEMs might promote plaque vulnerability in T2DM which could however not be confirmed at tissue level in advanced atherosclerotic lesions.