Biomedical subjects

Mihail Hristov

Publications and source records attributed to Mihail Hristov.

9 recordsLinked to original sources

PubMed2006

Reduced numbers of circulating endothelial progenitor cells in patients with coronary artery disease associated with long-term statin treatment.

While statin treatment may transiently mobilize endothelial progenitor cells (EPCs), the dose-dependent effects of a continuous statin therapy on EPCs in patients with chronic coronary artery disease (CAD) have not been analyzed. In 209 patients with angiographically documented CAD, 144 of which received 10-40 mg/day of statins for >8 weeks, the EPC number was determined by flow cytometry directly (CD34(+)/KDR(+), n=58) and after in vitro-culture (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine-labeled Ac-LDL (DiI-Ac-LDL(+))/lectin(+), n=209). EPC function was assessed by the formation of colony forming units (CFUs). Univariate analysis revealed that the dose of continuous statin therapy inversely correlated with the EPC number. Treatment with 40 mg/day significantly reduced EPC counts. Multivariate analysis unveiled the statin dose and extent of CAD as independent predictors of reduced EPC numbers. Conversely, obesity predicted increased counts, while CFU development was not detectable in all patients and augmented in females and smokers but not in statin-treated patients. Compared with matched controls, statin-treated patients showed significantly reduced absolute and relative EPC counts. In a prospective analysis, initiation of statin therapy significantly diminished the number of circulating and isolated EPCs after 3 but not after 1 month(s). Thus, the statin dose during chronic and continuous treatment independently predicts reduced numbers of circulating as well as isolated EPCs in patients with CAD.

Antigens, CD34↗

PubMed2006

A novel drug-eluting stent coated with an integrin-binding cyclic Arg-Gly-Asp peptide inhibits neointimal hyperplasia by recruiting endothelial progenitor cells.

OBJECTIVES: Novel stents loaded with an integrin-binding cyclic Arg-Gly-Asp peptide (cRGD) were analyzed for their potential to limit coronary neointima formation and to accelerate endothelialization by attracting endothelial progenitor cells (EPCs). BACKGROUND: Re-endothelialization is important for healing after arterial injury. METHODS: Effects of cRGD on EPC number, recruitment in flow, and invasion were analyzed in vitro. A durable polymer coating containing 67 microg cRGD per stent was developed for Guidant Tetra stents. Twelve cRGD-loaded polymer, 12 unloaded polymer, and 12 bare metal stents were deployed in porcine coronary arteries. Quantification of cRGD in peri-stent tissue was established by high-performance liquid chromatography (HPLC) and mass spectrometry (MS). Histomorphometry and immunostaining were performed after 4 and 12 weeks. Recruitment of labeled porcine EPCs was assessed 7 days after intracoronary infusion. RESULTS: The cRGD clearly supported the outgrowth, recruitment, and migration of EPCs in vitro. At 4 weeks, there was no difference for mean neointimal area and percent area stenosis in the cRGD-loaded, polymer, or bare metal stent group. At 12 weeks, neointimal area (2.2 +/- 0.3 mm2) and percent area stenosis (33 +/- 5%) were significantly reduced compared with polymer stents (3.8 +/- 0.4 mm2, 54 +/- 6%; p = 0.010) or bare metal stents (3.8 +/- 0.3 mm2, 53 +/- 3%; p < 0.001). The HPLC/MS confirmed cRGD tissue levels of 1 to 3 mug/stent at 4 weeks, whereas cRGD was not detectable at 12 weeks. Staining for CD34 and scanning electron microscopy indicated enhanced endothelial coverage on cRGD-loaded stents at 4 weeks associated with a significant increase in the early recruitment of infused EPCs. CONCLUSIONS: Stent coating with cRGD may be useful for reducing in-stent restenosis by accelerating endothelialization.

Animals↗

PubMed2006

[The therapeutic effect of autologous bone marrow cells in ischemic heart disease].

Adult human bone marrow and peripheral blood contain diverse stem and progenitor cells with some properties resembling those of embryonic stem cells, as this has been revealed by an increasing body of evidence within the near past. Numerous in vitro experiments and subsequent animal studies have already demonstrated that these adult progenitor cells considerably contribute to the regeneration of ischemic or injured tissue. Over the last 4 years, several clinical studies employing such a hypothesis in the context of myocardial repair after acute infarction or during chronic ischemic heart disease have been published. These studies have used autologous bone marrow- as well as peripheral blood-derived progenitor cells, which were delivered via intracoronary or intramyocardial routes near the ischemic area. The initial results demonstrated the safety and possible benefit of this strategy, which appears to be relatively inexpensive and free of side effects. However, the present clinical studies were small in size so that the overall therapeutic efficacy remains open to debate and evaluation. Furthermore, a major part of the underlying repair mechanisms has been proposed but not yet elaborated. Hence, larger case-controlled, randomized and double-blinded trials in addition to experimental investigations on the primary molecular mechanisms of myocardial repair are crucial for the future.

Animals↗

PubMed2006

The therapeutic potential of progenitor cells in ischemic heart disease--Past, present and future.

Within the recent past, it has become increasingly evident that adult bone marrow and peripheral blood do not only contain diverse hematopoietic precursors but also stem- and progenitor cells with some properties resembling those of embryonic cells. These adult progenitor cells can contribute to the regeneration of injured tissue as has been revealed by in vitro experiments and subsequent animal studies. Over the last four years, several clinical studies employing such a hypothesis in the context of myocardial repair after acute infarction or during chronic ischemic failure have been published. These studies have used autologous bone marrow cells as well as peripheral blood-derived progenitor cells, which were delivered via intracoronary or intramyocardial routes near the infarct area. The initial results demonstrated the safety and possible benefit of this strategy, which appear to be relatively simple, inexpensive and free of side effects. However, the present clinical studies were small in size so that the overall therapeutic efficacy remains open to debate and evaluation. Furthermore, a major part of the molecular mechanisms underlying progenitor cell-mediated repair has been proposed but not yet elaborated. Hence, larger controlled randomized and double-blinded trials in addition to experimental investigations on the primary mechanisms of repair are keenly anticipated.

Clinical Trials as Topic↗

PubMed2004

Apoptotic bodies from endothelial cells enhance the number and initiate the differentiation of human endothelial progenitor cells in vitro.

Endothelial progenitor cells (EPCs) play a role in the repair of ischemic or injured tissue. Because endothelial injury can be associated with apoptosis, we have investigated whether apoptotic bodies from mature endothelial cells (ECs) may affect growth and differentiation of EPCs in vitro. A 24-hour incubation of isolated human EPCs with apoptotic bodies-rich medium (ABRM) from ECs led to a significant increase in the number of spindle-shaped attached cells. EPCs were characterized by DiI-Ac-LDL/lectin staining and measurement of CD34 and kinase insert domain receptor (KDR) expression. The treatment with ABRM resulted in a 2-fold increase of DiI-Ac-LDL/lectin-positive cells and up-regulation of CD34 (22% +/- 2% versus 13% +/- 3%, P < .05 and KDR (49% +/- 12% versus 19% +/- 7%, P < .05). Fluorescence and confocal laser microscopy demonstrated the uptake of apoptotic bodies by the EPCs. Apoptotic bodies-depleted medium had no effect, whereas the incubation with suspension of apoptotic bodies induced effects similar to those of ABRM. Our results suggest that apoptotic bodies from ECs are taken up by EPCs, increasing their number and differentiation state. Such a mechanism may facilitate the repair of injured endothelium and may represent a new signaling pathway between progenitor and damaged somatic cells.

Apoptosis↗

PubMed2003

Endothelial progenitor cells: mobilization, differentiation, and homing.

Postnatal bone marrow contains a subtype of progenitor cells that have the capacity to migrate to the peripheral circulation and to differentiate into mature endothelial cells. Therefore, these cells have been termed endothelial progenitor cells (EPCs). The isolation of EPCs by adherence culture or magnetic microbeads has been described. In general, EPCs are characterized by the expression of 3 markers, CD133, CD34, and the vascular endothelial growth factor receptor-2. During differentiation, EPCs obviously lose CD133 and start to express CD31, vascular endothelial cadherin, and von Willebrand factor. EPCs seem to participate in endothelial repair and neovascularization of ischemic organs. Clinical studies using EPCs for neovascularization have just been started; however, the mechanisms stimulating or inhibiting the differentiation of EPC in vivo and the signals causing their migration and homing to sites of injured endothelium or extravascular tissue are largely unknown at present. Thus, future studies will help to explore areas of potential basic research and clinical application of EPCs.

AC133 Antigen↗

PubMed2003

HMG-CoA reductase inhibitors induce apoptosis in neointima-derived vascular smooth muscle cells.

In the context of atherogenesis and restenosis, vascular smooth muscle cell (SMC) proliferation and apoptosis play a crucial role. Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (statins) have been shown to inhibit the migration and proliferation of SMC, and to induce apoptosis in different cell types including SMC. However, it is not known whether these agents induce apoptosis in neointimal SMC. We investigated the effects of statin treatment on neointimal SMC as compared to medial cells by using trypan blue counting, MTT test, Annexin V staining, cell cycle analysis and a co-culture model. The incubation of neointimal or medial SMC with lovastatin reduced the MTT activity as well as the total cell number, and increased the amount of trypan blue positive cells, indicative of cell death. We tested by staining with Annexin V/propidium iodide, specific antibodies to active caspase-3, TUNEL reaction, and by the appearance of a sub-G1 peak, whether the observed increase in cell death was due to apoptosis. After treatment with lovastatin, programmed cell death was slightly increased in medial SMC, while neointimal cells showed a pronounced rate of apoptosis. In an attempt to mimic early phases of restenosis in vitro by seeding low density neointimal cells onto high density medial cells, we found that statin treatment induced cell death preferentially in the neointimal SMC. Our results suggest that statins enhance the rate of apoptosis in neointimal SMC, which may be an interesting feature to reduce restenosis after successful angioplasty.

Animals↗

PubMed2003

Endothelial progenitor cells: isolation and characterization.

Bone marrow of adults contains a subtype of progenitor cells that have the capacity to differentiate into mature endothelial cells and have therefore been termed endothelial progenitor cells (EPCs). Of the three cell markers (CD133, CD34, and the vascular endothelial growth factor receptor 2) that characterize the early functional EPCs, located predominantly in the bone marrow, EPCs obviously lose CD133/CD34 and start to express CD31, vascular endothelial cadherin, and von Willebrand factor when migrating to the circulation. Various isolation procedures of EPCs from different sources by using adherence culture or magnetic microbeads have been described, but published findings with regard to the number of EPCs in the peripheral circulation of healthy adults are scanty and no data regarding the lifetime of EPCs in vivo exist. Clinical studies employing EPCs for neovascularization of ischemic organs have just been started; however, the mechanisms stimulating or inhibiting the differentiation of bone marrow-derived EPCs in vivo and the signals causing their adhesion, migration, and homing to sites of injured tissue are largely unknown at present.

Cell Separation↗

PubMedDate not supplied

Endothelial progenitor cells: characterization, pathophysiology, and possible clinical relevance.

Bone marrow and peripheral blood of adults contain a special sub-type of progenitor cells which are able to differentiate into mature endothelial cells, thus contributing to re-endothelialization and neo-vascularization. These angiogenic cells have properties of embryonal angioblasts and were termed endothelial progenitor cells (EPCs). In general, three surface markers (CD133, CD34 and the vascular endothelial growth factor receptor-2) characterize the early functional angioblast, located predominantly in the bone marrow. Later, when migrating to the systemic circulation EPCs gradually lose their progenitor properties and start to express endothelial marker like VE-cadherin, endothelial nitric oxide synthase and von Willebrand factor. The number of circulating EPCs in healthy subjects is rather low and a variety of conditions or factors may further influence this number. In the context of possible therapeutic application of EPCs recent clinical studies employing these cells for neo-vascularization of ischemic organs have just been published. However, the specificity of the observed positive clinical effects, the mechanisms regulating the differentiation of EPCs and their homing to sites of injured tissue remain partially unknown at present.

Animals↗