In vitro human cord blood platelet lysate characterisation with potential application in wound healing

Platelets contain abundant growth factors and cytokines that have a positive influence on the migration and proliferation of different cell types by modulating its physiopathological processes. As it is known that human umbilical cord blood platelet lysate (UCB-PL) contains a supraphysiological concentration of growth factors, in the present study, we investigated its effectiveness in wound-healing processes. Human UCB-PL was obtained by the freeze/thaw of platelet concentrate (1.1 × 10⁹ platelets/L), and its effect was evaluated on human or mouse endothelial cells, monocytes, fibroblasts, and keratinocytes in different concentrations. Human UCB-PL was observed to have high levels of pro-angiogenic growth factor than peripheral blood platelet-rich plasma. Among the cell lines, different concentrations of human UCB-PL were necessary to influence their viability and proliferation. For L929 cells, 5% of total volume was necessary, while for human umbilical vein endothelial cell, it was 10%. Cell migration on monocytes was increased with respect to the positive control, and scratch closure on keratinocytes was increased with respect to serum-free medium with only 10% of human UCB-PL. We concluded that the human UCB-PL may be useful to produce a large amount of standard platelet concentrates sufficient for several clinical-scale expansions avoiding inter-individual variability, which can also be used as a functional tool for clinical regenerative application for wound healing.

Chemical–physical and in vivo evaluations of a self-assembling amphiphilic peptide as an injectable hydrogel scaffold for biomedical applications

The self-aggregation and gelation of an amphiphilic peptide (C17H35CONH–A4G3ERGD, peptide amphiphile) were studied by light scattering, viscometry, nuclear magnetic resonance diffusometry, and atomic force microscopy. The peptide amphiphile critical aggregation concentration was evaluated to be 16 and 60 µM by light scattering and viscometry, respectively. The observed difference was attributed to the larger sensitivity of the latter technique to the presence of long fibrils. The addition of one equivalent or more of divalent cations (Ca2+ and Mg2+) to peptide amphiphile formed dense incoherent hydrogels. Based on the atomic force microscopy and nanoindentation data, both the hydrogel morphology and stiffness were independent of the cation type and peptide amphiphile concentration. However, gel stiffness increased on increasing Ca2+/peptide amphiphile molar ratio while a parallel decrease in the apparent water diffusion rate was observed by nuclear magnetic resonance diffusometry. The dispersions of endothelial progenitor cells in the peptide amphiphile hydrogels were evaluated in vivo on a rat tissue hypoxia model. Significant capillary formation at the injection site was observed by tissue appearance and histological examination, which indicated endothelial progenitor cell/peptide amphiphile hydrogel-enhanced angiogenesis in ischemic tissue.

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.

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.