Cédric Boura

Endothelial cells grown on thin polyelectrolyte mutlilayered films: an evaluation of a new versatile surface modification

Endothelial cell seeding constitutes an appreciated method to improve blood compatibility of small-diameter vascular grafts. In this study, we report the development of a simple innovative technique based on multilayered polyelectrolyte films as cell adhesive substrates. Polyelectrolyte multilayered films ending by poly(sodium-4-styrenesulfonate)/poly(allylamine hydrochloride) (PSS/PAH) or poly(L-glutamic acid)/poly(D-lysine) (PGA/PDL) could enhance cell adhesion by modification of the physico-chemical properties of the surface. The biological responses of human umbilical vein endothelial cells seeded on the polyelectrolyte multilayer films, on PDL or PAH monolayers, and on control surfaces, were evaluated in terms of initial attachment, growth, cellular metabolic activity, endothelial phenotype, and adhesion. The results showed that polyelectrolyte multilayers neither induce cytotoxic effects nor alter the phenotype of the endothelial cells. The polyelectrolyte multilayered films enhanced initial cell attachment as compared to the polyelectrolyte monolayer. Cell growth observed on the films was similar to that on TCPS. Among the different coating tested, the film ending by PSS/PAH exhibited an excellent cellular biocompatibility and appeared to be the most interesting surface in terms of cellular adhesion and growth. Such films could be used to cover hydrophobic (cell resistant) substrates in order to promote cell colonization, thereby constituting an excellent material for endothelial cell seeding.

Volume expansion with modified hemoglobin solution, colloids, or crystalloid after hemorrhagic shock in rabbits: effects in skeletal muscle oxygen pressure and use versus arterial blood velocity and resistance.

Therapeutic goals for hemorrhagic shock resuscitation are the increase of cardiac output and oxygen delivery. The possibility exists that because of microcirculatory effects, different volume expanders result in different tissue oxygen delivery and oxygen use. In a rabbit model of resuscitation from hemorrhagic shock (50% blood loss), we compared the effects of an hemoglobin-based O2-carrying solution (HbOC) with those elicited by albumin, hydroxyethyl starch (HES), or saline on systemic hemodynamics, skeletal muscle O2 pressure (PtiO2), and interstitial concentration of lactate (LACi) through the combined implantation of a microdialysis probe and a sensitive O2 electrode into the hind limb. Hemorrhagic shock induced a 50% decrease in mean arterial pressure (MAP), femoral artery blood flow (BF), and PtiO2. After resuscitation, there were statistically significant differences among the volume expanders. The increase in MAP was faster with HbOC and colloids, and slower with saline, mainly obtained by vasoconstriction for HbOC and by increased BF with albumin and HES. The maximum MAP values were significantly higher for HbOC compared with the other volume expanders. HbOC and colloids induced a faster increase in PtiO2 as compared with saline, but maximum PtiO2 values were not different among the volume expanders. Tissue oxygen use as estimated by LACi increased transiently at the beginning of volume expansion with similar maximum values. Animals resuscitated with saline had significantly higher LACi concentrations after the onset of volume expansion as compared with HbOC but not with colloids. Our results demonstrate that there are measurable differences in MAP and BF upon resuscitation with the four different solutions and there is a slower increase in tissue PtiO2 with saline than with colloids associated with significantly increased LACi consistent with delayed reoxygenation upon resuscitation with saline.

New Peptide-Conjugated Chlorin-Type Photosensitizer Targeting Neuropilin-1 for Anti-Vascular Targeted Photodynamic Therapy

Photodynamic therapy (PDT) is a cancer treatment modality that requires three components, namely light, dioxygen and a photosensitizing agent. After light excitation, the photosensitizer (PS) in its excited state transfers its energy to oxygen, which leads to photooxidation reactions. In order to improve the selectivity of the treatment, research has focused on the design of PS covalently attached to a tumor-targeting moiety. In this paper, we describe the synthesis and the physico-chemical and photophysical properties of six new peptide-conjugated photosensitizers designed for targeting the neuropilin-1 (NRP-1) receptor. We chose a TPC (5-(4-carboxyphenyl)-10,15, 20-triphenyl chlorine as photosensitizer, coupled via three different spacers (aminohexanoic acid, 1-amino-3,6-dioxaoctanoic acid, and 1-amino-9-aza-3,6,12,15-tetraoxa-10-on-heptadecanoic acid) to two different peptides (DKPPR and TKPRR). The affinity towards the NRP-1 receptor of the conjugated chlorins was evaluated along with in vitro and in vivo stability levels. The tissue concentration of the TPC-conjugates in animal model shows good distribution, especially for the DKPPR conjugates. The novel peptide–PS conjugates proposed in this study were proven to have potential to be further developed as future NRP-1 targeting photodynamic therapy agent.

Tumor vascular responses to antivascular and antiangiogenic strategies: looking for suitable models

Antiangiogenic and vascular disrupting agents are in the current cancer therapeutic armamentarium. A better understanding of the intricate mechanisms ruling neovessel survival within tumors during or after treatment is needed. Refinement of imaging and a growing knowledge of molecular biology of tumor vascularization provide new insights. It is necessary to define suitable methods for monitoring tumor response and appropriate tools to analyze data. This review compares most commonly used preclinical models, considering their recent improvements, and describes promising new approaches such as microfluidics, real-time electrical impedance based technique and noninvasive imaging techniques. The advantages and limitations of the in vitro, ex vivo and in vivo models are discussed. This review also provides a critical summary of emerging approaches using mathematical modeling.

Molecular modelling, synthesis and biological evaluation of peptide inhibitors as anti-angiogenic agent targeting neuropilin-1 for anticancer application

Vascular endothelial growth factor (VEGF) and its co-receptor neuropilin-1 (NRP-1) are important targets of many pro-angiogenic factors. In this study, nine peptides were synthesized and evaluated for their molecular interaction with NRP-1 and compared to our previous peptide ATWLPPR. Docking study showed that the investigated peptides shared the same binding region as shown by tuftsin known to bind selectively to NRP-1. Four pentapeptides (DKPPR, DKPRR, TKPPR and TKPRR) and a hexapeptide CDKPRR demonstrated good inhibitory activity against NRP-1. In contrast, peptides having arginine residue at sites other than the C-terminus exhibited low activity towards NRP-1 and this is confirmed by their inability to displace the VEGF165 binding to NRP-1. Docking study also revealed that replacement of carboxyl to amide group at the C-terminal arginine of the peptide did not affect significantly the binding interaction to NRP-1. However, the molecular affinity study showed that these peptides have marked reduction in the activity against NRP-1. Pentapeptides having C-terminal arginine showed strong interaction and good inhibitory activity with NRP thus may be a good template for anti-angiogenic targeting agent.

Influence of polyelectrolyte multilayer films on the ICAM-1 expression of endothelial cells

Recently, the use of polyelectrolyte films has been suggested as a new versatile technique of surface modification aimed at tissue engineering. In the present study, we evaluated the expression of intercellular adhesion molecule (ICAM)-1 of endothelial cells (ECs) seeded on two types of polyelectrolyte multilayer films either terminated by poly(d-lysine) (PDL) or poly(allylamine hydrochloride) (PAH). This work showed that chemical stimulations with tumor necrosis factor (TNF)-α induced the ICAM-1 expression of ECs differently depending largely on the film architecture employed. Compared with PAH-ending films, the PDL-ending ones upregulated the ICAM-1 expression of the ECs after a prolonged exposition to TNF-α, rendering this film type less favorable in tissue engineering. Cytochalasin D (an F-actin disrupting agent) showed the involvement of the cytoskeleton in the upregulation of ICAM-1 for cells deposited on films terminated by PDL. The PAH-ending films did not perturb the ICAM-1 expression of ECs and might thus enhance the seeding of ECs in vascular engineering.

Ultrasmall AGuIX theranostic nanoparticles for vascular-targeted interstitial photodynamic therapy of glioblastoma

Despite combined treatments, glioblastoma outcome remains poor with frequent local recurrences, indicating that a more efficient and local therapy is needed. In this way, vascular-targeted photodynamic therapy (VTP) could help tumor eradication by destroying its neovessels. In this study, we designed a polysiloxane-based nanoparticle (NP) combining a magnetic resonance imaging (MRI) contrast agent, a photosensitizer (PS) and a new ligand peptide motif (KDKPPR) targeting neuropilin-1 (NRP-1), a receptor overexpressed by angiogenic endothelial cells of the tumor vasculature. This structure achieves the detection of the tumor tissue and its proliferating part by MRI analysis, followed by its treatment by VTP. The photophysical properties of the PS and the peptide affinity for NRP-1 recombinant protein were preserved after the functionalization of NPs. Cellular uptake of NPs by human umbilical vein endothelial cells (HUVEC) was increased twice compared to NPs without the KDKPPR peptide moiety or conjugated with a scramble peptide. NPs induced no cytotoxicity without light exposure but conferred a photocytotoxic effect to cells after photodynamic therapy (PDT). The in vivo selectivity, evaluated using a skinfold chamber model in mice, confirms that the functionalized NPs with KDKPPR peptide moiety were localized in the tumor vessel wall.

Sensitivity of glioma initiating cells to a monoclonal anti-EGFR antibody therapy under hypoxia.

AIMS Glioma initiating cells (GICs) represent a subpopulation of tumor cells endowed with self-renewal and multilineage differentiation capacity but also with innate resistance to cytotoxic agents, a feature likely to pose major clinical challenges towards the complete eradication of minimal residual disease in glioma patients. MATERIALS AND METHODS In this work, GICs were obtained from two patient-derived high-grade gliomas xenograft model, expressing differently EGFR. GICs were exposed to anti-EGFR monoclonal antibody cetuximab during 48h in 1% or 21% oxygen tension. Cell viability and self-renewal capacity were then evaluated as well as their angiogenic properties. KEY FINDINGS GICs were sensitive to cetuximab only in normoxic condition whatever the EGFR status. Nevertheless, under hypoxia cetuximab was able to decrease the self-renewal capacity as well as the expression of CD133 while expression of GFAP increased. Moreover, cetuximab decreased the effect of GICs on endothelial cell migration under hypoxia. SIGNIFICANCE Consequently, anti-EGFR therapy can be envisaged to target specifically GICs in order to limit the tumor recurrence.

Stimulation of medulloblastoma stem cells differentiation by a peptidomimetic targeting neuropilin-1

Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Despite the progress of new treatments, the risk of recurrence, morbidity, and death remains important. The neuropilin-1 (NRP-1) receptor has recently been implicated in tumor progression of MB, which seems to play an important role in the phenotype of cancer stem cells. Targeting this receptor appears as an interesting strategy to promote MB stem cells differentiation. Cancer stem-like cells of 3 MB cell lines (DAOY, D283-Med and D341-Med), classified in the more pejorative molecular subgroups, were obtained by in vitro enrichment. These models were characterized by an increase of NRP-1 and cancer stem cell markers (CD15, CD133 and Sox2), meanwhile a decrease of the differentiated cell marker Neurofilament-M (NF-M) was observed. Our previous work investigated potential innovative peptidomimetics that specifically target NRP-1 and showed that MR438 had a good affinity for NRP-1. This small molecule decreased the self-renewal capacity of MB stem cells for the 3 cell lines and reduced the invasive ability of DAOY and D283 stem cells while NRP-1 expression and cancer stem cell markers decreased at the same time. Possible molecular mechanisms were explored and showed that the activation of PI3K/AKT and MAPK pathways significantly decreased for DAOY cells after treatment. Finally, our results highlighted that targeting NRP-1 with MR438 could be a potential new strategy to differentiate MB stem cells and could limit medulloblastoma progression.

PO-013 A novel peptidomimetic targeting nrp1 increases radiosensitivity of medulloblastoma stem cells

Introduction Medulloblastoma (MB) is the most common paediatric malignant brain tumour. Recurrences occur in more than 40% of cases and sequelae are very important due to aggressiveness of the treatments. Cancer stem cells (CSCs) generate tumours through the stem cell patterns of self-renewal and differentiation into multiple tumour cell types and have better DNA repair capability inducing tumour resistance to radiotherapy (RT) and chemotherapy. Neuropilin-1 (NRP1) is involved in the progression of MB and seems to be in relation with the differentiation state of cancer cells. Recent molecular research has provided a better understanding of tumour development for the purpose of more targeted treatments. MR438 is a new sugar-based peptidomimetic targeting NRP-1. Our first results showed that MR438 seemed to induce the differentiation of MB stem cells. The objectives were therefore to demonstrate the effect of MR438 on in vitro and in vivo radiosensitivity. Material and methods DAOY, D283Med and D341Med cell lines were used for obtaining cancer stem cells by in vitro enrichment. Clonogenic assays were performed on MB stem cells exposed to 0, 2, 4, 6, 10 Gy of RT in combination with MR438. For in vivo experiments, xenografted nude mice with 3 subgroup tumours were treated by RT at 2 Gy x 5 days in combination with MR438 and compared to Tuftsin in 6 groups (control, MR438, Tuftsin, RT, RT +MR438, RT +Tuftsin, n=6). Tumour volume was measured by calliper until a maximum of 45 days post-treatment, and then tumours were removed at the set end-points for clonogenic assay and cell viability. Results and discussions Inhibition of NRP-1 via MR438 increased radiosensitivity of CSC models especially at the dose of 2 Gy. The DMF2 were 0.74, 0.89 and 0.88 for DAOY, D283-Med and Med-D341 cells respectively. In heterotopic models, a significant improvement of tumours radiosensitivity was also observed in the MR438 +RT group by comparing RT alone or MR438 alone (p<0.01). In an interesting way, the self-renewal capacity for CSCs after tumour dissociation was also decreased significantly when tumours were treated by MR438 +RT versus RT (p<0.05). Conclusion This work showed the interest of targeting NRP-1 in association with radiotherapy to limit MB progression in decreasing the stem cells number in these tumours. Moreover, our in vivo experiments proved the possibility to use MR438 peptidomimetic as a radiosensitizing agent for treatment of MB.