Fibrin acts as biomimetic niche inducing both differentiation and stem cell marker expression of early human endothelial progenitor cells.

OBJECTIVES: Transplantation of endothelial progenitor cells (EPCs) is a promising approach for revascularization of tissue. We have used a natural and biocompatible biopolymer, fibrin, to induce cell population growth, differentiation and functional activity of EPCs. MATERIALS AND METHODS: Peripheral blood mononuclear cells were cultured for 1 week to obtain early EPCs. Fibrin was characterized for stiffness and capability to sustain cell population expansion at different fibrinogen-thrombin ratios. Viability, differentiation and angiogenic properties of EPCs were evaluated and compared to those of EPCs grown on fibronectin. RESULTS: Fibrin had a nanometric fibrous structure forming a porous network. Fibrinogen concentration significantly influenced fibrin stiffness and cell growth: 9 mg/ml fibrinogen and 25 U/ml thrombin was the best ratio for enhanced cell viability. Moreover, cell viability was significantly higher on fibrin compared to being on fibronectin. Even though no significant difference was observed in expression of endothelial markers, culture on fibrin elicited marked induction of stem cell markers OCT 3/4 and NANOG. In vitro angiogenesis assay on Matrigel showed that EPCs grown on fibrin retain angiogenetic capability as EPCs grown on fibronectin, but significantly better release of cytokines involved in cell recruitment was produced by EPC grown on fibrin. CONCLUSION: Fibrin is a suitable matrix for EPC growth, differentiation and angiogenesis capability, suggesting that fibrin gel may be very useful for regenerative medicine.

Role of endothelial progenitor cell mobilization after percutaneous angioplasty procedure.

Circulating endothelial progenitor cells (EPCs) are bone marrow-derived cells, contributing to endothelial cell regeneration of injured vessels as well as neovascularization of ischemic lesions. EPC levels and function are inversely correlated with cardiovascular risk factors, can predict the occurrence of adverse events and atherosclerotic disease progression. Ischemia and inflammation are the primary triggers for EPC mobilization and homing, however, vascular trauma, as it occurs during surgical procedures, has been demonstrated to stimulate EPC mobilization even in absence of tissue ischemia. The effect of angioplasty on EPCs is not well defined, mainly because of the different and sometimes contrasting clinical results, due to low numbers of patients enrolled and to lack of standardization in evaluating EPCs. Aim of this review is to report recent results on the effect of EPC mobilization and homing after angioplasty, attempting to summarize them in a comprehensive model. The effect on EPCs of different kind of stents and the potential use of new stents able to attract EPCs will be also described. Results obtained in patients undergoing angioplasty in different vascular districts (coronary, peripheral and carotid) will be shown, together with the correlation between circulating progenitor cells and restenosis.

Circulating endothelial progenitor cells characterization, function and relationship with cardiovascular risk factors.

Since the first description of putative progenitor endothelial cells mobilized from bone marrow by stimuli like ischemia and cytokines, several studies in animals have confirmed their role in neovascularization of ischemic organs. In ischemic myocardium endothelial progenitor cells can prevent cardiomyocyte apoptosis, reduce remodeling and improve cardiac function. These observations led to the hypothesis of endothelial progenitor cells as possible cell-based therapy in patients by autologous transplantation in ischemic tissue or by improving peripheral circulating numbers with mobilization by cytokines. Early trials, including a randomized one, suggest that the intracoronary autologous bone marrow cell transfer after myocardial infarction exerts at least short term functional benefits. Since endothelial damage and dysfunction play a critical role in atherosclerosis disease, research interest was addressed to evaluate the role of progenitor endothelial cells in vascular endothelial layer maintenance. Opposing to local resident endothelial cells poor proliferation rate, progenitor endothelial cells regenerative capacity, homing and integration into blood vessels have been interpreted as a protective role of these cells in vascular homeostasis. Indeed, the number and function of endothelial progenitor cells relate with the progression of atherosclerosis; the accumulation of cardiovascular risk factors or an increased overall risk are inversely associated with endothelial progenitor cells number and function. Finally, recent studies have shown a role of progenitor cells numbers to predict cardiovascular events, raising endothelial progenitor cells to the podium of novel prognostic biomarker.

Binding properties of human albumin modified by covalent binding of penicillin.

Derivatisation of lysine residues in human albumin was performed in vitro by reaction with penicillin G. This modification reaction has been reported to occur in patients treated with high dosages of the antibiotic. The structure of the modified protein was characterised by mass spectrometry and circular dichroism. The number of the lysine residues involved depends on the time of incubation and on the drug/protein molar ratio. The secondary structure of the modified protein does not change significantly with respect to the native protein. Furthermore, the binding properties of the modified albumin were characterised by CD spectroscopy. Phenylbutazone, diazepam and bilirubin, known to bind to specific binding areas, were used as markers. A decrease of the affinity to the high-affinity binding sites was observed after the modification.