Biomedical subjects

J F Stoltz

Publications and source records attributed to J F Stoltz.

At least 19 recordsLinked to original sources

PubMed2003

The strength of integrin binding between neutrophils and endothelial cells.

The firm adhesion of activated polymorphonuclear neutrophils to endothelial cells in blood vessels is achieved through binding of the integrin intercellular adhesion molecule. To contribute to the better understanding of this adhesion step, our investigation is aimed at the relationship between integrin expression and the strength of neutrophil binding to endothelial cells. Flow cytometry and 3D scanning microscopy are used to study integrin expression and distribution, respectively. It is found that CD11b/CD18 integrin expression is localized in clusters distributed irregularly over the neutrophil surface. After cell activation, the cluster distribution polarizes, increasing the local CD11b/CD18 density concurrently with nearly doubled integrin expression. The neutrophil adhesion efficiency is measured in a flow chamber coated successively by various substrates, including endothelial cells in an activated state. Analysis of the flow dependence of the number of attached cells reveals the prevailing number of neutrophils with stronger binding to the endothelium when both cells are in the activated state in comparison with non-activated cells.

CD11b Antigen↗

PubMed2003

Biological response of human aortic endothelial cells exposed to acellular hemoglobin solutions developed as potential blood substitutes.

The cardiovascular effects of hemoglobin-based oxygen carriers (HBOCs) are mainly related to their nitric oxide (NO) scavenging properties but other effects such as the impact of these hemoglobins on the endothelial cell (EC) biology are not well understood. We hypothesized that HBOCs could modify EC functions by altering gene expression, in particular the endothelial NO synthase (NOS3) and/or by activating EC. Cultured human aortic endothelial cells (HAEC) were incubated for 3 hours with purified cell-free Hb, Dex-BTC-Hb or alpha alpha-Hb (16 g/L). Expression of NOS3 mRNA and protein were assessed by semi-quantitative RT-PCR and Western blot respectively immediately after and 24 hours after incubation. The expression and localization of the adhesion molecule ICAM-1 were detected by fluorescence microscopy. None of the solutions tested modified NOS3 mRNA and protein expression despite adequate controls that up- or down-regulate NOS3 expression. The expression and the localization of ICAM-1 on the cell membrane were modified after 3 hours of incubation with all the hemoglobin solutions tested in a manner similar to tumor necrosis factor-alpha. In conclusion, HAEC incubation with clinically relevant concentrations of HBOCs induced changes in the pattern of ICAM-1 expression consistent with cell activation/cell signaling mechanisms. However, HBOCs did not alter NOS3 gene expression.

Aorta↗

PubMed2003

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.

Biocompatible Materials↗

PubMed2003

Complete recovery from Cryptosporidium parvum infection with gastroenteritis and sclerosing cholangitis after successful bone marrow transplantation in two brothers with X-linked hyper-IgM syndrome.

We describe two brothers who suffered from hyper-IgM syndrome (HIGM1) with similar clinical features: recurrent infections, especially cryptosporidium gastroenteritis with cholangitis. Their activated T cells did not express CD40L. Nucleotide sequencing revealed a mutation in both boys with respect to intron 4 and exon 5 boundaries of the CD40L gene in Xq26. They underwent successful bone marrow transplantation (BMT) from HLA-geno-identical siblings. The Cryptosporidium infection and cholangitis resolved thereafter. At 6 months after BMT, expression of CD40L on activated T lymphocytes was normal. After 1 year, both boys are well, and immune reconstitution has improved. Based on these two successful experiences, BMT with a genoidentical sibling seems a reasonable therapeutic approach for HIGM1, if Cryptosporidium infection occurs.

Animals↗

PubMed2003

Caveolin-1 redistribution in human endothelial cells induced by laminar flow and cytokine.

Caveolin-1 is a principal component of caveolae and is involved in signaling transduction in a number of cells. A hypothesis was proposed in this work that mechanical forces due to flow induce caveolin-1 translocation. So the changes of caveolin-1 expression and distribution in cultured endothelial cells (HUVECs) exposed to a steady laminar flow were studied. For comparing with the influence of cytokine, caveolin-1 in the cells stimulated by TNF-alpha was also investigated. Indirect immunofluorescence and double fluorescence labeling showed that in control cells, caveolin-1 was primarily localized on the cell surface, which corresponded to the peripheral distribution of F-actin, and presented some local concentrations. In the cells exposed to a laminar flow (1.0 Pa), caveolin-1 distribution showed a time-dependent variation. After 24 h of shear, the local concentration of caveolin-1 was found, in the most cells, at upstream side of cell body. Also more caveolin-1 molecules were observed in the cells. In contrast, TNF-alpha induced a decrease of caveolin-1 in cells. The redistribution of caveolin-1 seems to be correlated to F-actin organization.

Actins↗

PubMed2003

The cooperative effect of L-selectin clusters and velocity-dependent bond formation that stabilizes leukocyte rolling.

The role of clustered of L-selectin receptors on the leukocyte surface is discussed in connection with the postulated velocity-dependent formation of selectin-ligand tether bonds to interpret the mechanism of leukocyte tethering to, and rolling along, the vascular endothelium. The distinct feature of this step-wise process is a weak dependence of leukocyte rolling velocity on the hydrodynamic forces of ambient flow due to the increased number of selectin bonds with increasing flow shear rate and also their clustering. The contact zones on the leukocyte surface are separated by distances with distribution which corresponds to the distribution of distances of the observed L-selectin clusters. It suggests that the localization of L-selectin receptors to clusters and the way of their approach to the ligand molecules creates such conditions for binding of L-selectin and ligand molecules that resulting number of bonds stabilizes rolling velocity.

Blood Flow Velocity↗

PubMed2003

CD34+ cells homing: quantitative expression of adhesion molecules and adhesion of CD34+ cells to endothelial cells exposed to shear stress.

To investigate the function of the main adhesion receptors (CD62L, CD49d, CD49e, CD11b and CD18) on CD34+ cells during homing, their expression was quantified by flow cytometry using calibration beads. CD34+ cells were isolated from bone-marrow (BM), cord blood (CB) or peripheral blood (PB) from patients with myeloma. As this process might mimic the mature leukocyte migration, we also observed the effect of exposing endothelial cells to shear stress (7 dyn/cm(2)) on the adhesion of CB CD34+ cells. The proportion of CD34+/CD62L+ cells was greater in PB than in BM (p<0.05). Likewise, we found a significantly greater expression of CD62L receptor on PB cells compared to BM cells (p<0.05) and on BM cells compared to CB cells (p<0.05). The proportions of CD34+/CD49d+ cells and CD34+/CD49e+ cells were significantly higher in the BM and CB than in PB. However, no significant difference in CD49d or CD49e antigen densities was observed. The beta_2 integrins (CD11b and CD18) receptors are also implicated in CD34+ cells homing to BM. No significant variation in CD34+/CD11b+ and CD34+/CD18+ cells frequency was noted. However quantitative analysis revealed that CD18 was more strongly expressed on BM cells than on PB and CB cells. The adhesion assay showed that fluid flow may favour a firm adhesion of CB CD34+ cells to endothelial cells whereas static conditions just allowed CD34+ cells sedimentation. In conclusion, quantitative expression of the main receptors on CD34+ cells indicates that the three main sources of CD34+ cells currently used for transplantation have neither the same phenotype nor the same number of antigenic sites for a receptor. So, we hypothesize that migrational capacity of these cells might be different. Moreover, it seems that shear stress could favor adhesion of CD34+ cells to endothelial cells.

Antigens, CD34↗

PubMed2003

Characterization of monoclonal antibodies against human red blood group cells antigens by laser backscattering.

A problem in immunohematology is to define the antibody quality which is related to its affinity expressed by the equilibrium constant. The activity of an antibody can be measured by the strength of its interaction, related to the adhesive energy exchanged during RBC agglutination which depends on the antigen-antibody liaison strength. To estimate this adhesive energy, two methods are used in this paper. Firstly, the dissociation behaviour of suspended RBC agglutinates was analysed by laser backscattering intensity (r) in a Couette flow. Backscattered intensity issued from shear-induced mechanical dissociation is recorded and submitted to a numerical process to obtain the energy parameter (ED). Secondly, a modification of this technique is proposed for measuring specific binding energy. Samples were exposed to increasing shear stress, and backscattered intensity was recorded. A constant increase of this intensity with raising shear stress was observed, pointed to a progressive dissociation of RBC agglutinates into smaller ones. Considering that complete dissociation of agglutinates is only approached asymptotically it is assumed that the final break-up of doublets (two-cell agglutinates) is produced at a critical shear stress (tauC) reflecting the work done to breaking-up the molecular bridges between both adjacent cells. This shear stress is defined by the extrapolation of the linear part of the curves [r-log tau] to the backscattered signal (r0) corresponding to the complete dispersion of RBCs. These approaches permit to define the specific surface adhesive energy (Gamma) by using the Derjaguin relation and to assess the functional characterization of specific immunoglobulins. In conclusion, two parameters characterizing monoclonal antibody agglutination properties, ED and Gamma, were estimated by laser backscattering methods, which could be very useful for antibodies quality control.

ABO Blood-Group System↗

PubMed2003

Comparison of wide-field/deconvolution and confocal microscopy in bioengineering. Interest of multi-photon microscopy in the study of articular cartilage.

The increase in lateral and spatial resolutions is one of the major targets of research and development in the field of optical microscopies applied to living tissue. The optical geometry of Confocal Laser Scanning Microscopy (CLSM) demonstrates its undeniable advantage on conventional fluorescence microscopy by segregating the planes outside the focussing plane. The methodological and technological advances of the last five years have been fast evolving, especially with regard to the optimisation of CLSM and deconvolution process. The limited analysis in thick tissue have given rise to the development of other techniques, multi-photon excitation microscopy in particular. In this paper, we have applied these techniques on major biological applications in bioengineering (endothelial cell, chondrocyte in 3D-culture, human cartilage) and discussed the technical limitations and perspectives.

Actins↗

PubMed2002

Shear stress induces caveolin-1 translocation in cultured endothelial cells.

Considering that vascular endothelial caveolae could be flow sensors converting mechanical stimuli into chemical signals transmitted into the cell, this work studied, in vitro, the change of caveolin-1 expression and distribution of cultured endothelial cells exposed to laminar flows. Experimental results showed that, in control cells, caveolin-1 were primarily localized on the cell surface, and presented some local concentrations. In cells exposed to laminar flows, caveolin-1 distribution showed a time-dependent variation. After 24 h of shear (1.0 Pa), the expression of caveolin-1 increased and a local caveolin-1 concentration was found, in most cells, at the upstream side of the cell body where the hydrostatic pressure and the spatial gradient of shear stress were at a maximum. As a comparison, tumor necrosis factor-a induced a decrease of caveolin-1 in the cells.

Caveolin 1↗

PubMed2002

Influence of temperature variation from 5 degrees C to 37 degrees C on aggregation and deformability of erythrocytes.

Erythrocyte aggregation and elongation index (EI) (deformability) are measured at temperatures ranging from 5 degrees C to 37 degrees C by aggregometer MA1, and diffractometer Rheodyne SSD and the LORCA, respectively. The test samples are prepared from blood obtained from healthy subjects in test tubes containing EDTA as an anticoagulant and prior to measurement are placed in a water bath for 30 min, maintained at respective temperatures. The aggregation process is given in terms of primary aggregation time and indices of aggregation. These show significant to highly significant changes with the increase of temperature compared to that at 5 degrees C. The EI increases with the increase of shear stress but shows significant decrease with the decrease of temperature.

Erythrocyte Aggregation↗

PubMed2002

In vitro study of intracellular IL-1beta production and beta1 integrins expression in stimulated chondrocytes--effect of rhein.

The purpose of the present study was to investigate the intracellular IL-1beta production and beta1 integrins (alpha4/beta1 and alpha5/beta1) expression on chondrocytes. Chondroytes monolayer (human chondrosarcoma cell line HEM-C55) were incubated for 12, 24 and 48 hours in the presence of Tumor Necrosis Factor-alpha (TNF-alpha, Sigma, France) or recombinant human IL-1alpha (rh-IL1alpha, Becton Dickinson, France). After direct immunolabelling, cells were either analyzed on FACScan flow cytometer (Becton Dickinson, France), or observed under an epi-fluorescence inverted microscope equipped with the CellScan EPR optical scanning acquisition system (IPLab-Scanalytics, USA). We found that the IL-1beta mean fluorescence intensity in flow cytometry and in 3D microscopy was increased in the presence of TNF-alpha or rh-IL-1alpha, and alpha4/beta1 or alpha5/beta1 expression was higher on stimulated cells than on control cells. On the other hand, we have evaluated the in vitro effects of rhein (10(-5) M, Negma, France), an active metabolite of diacerein, on the intracellular IL-1beta and beta1 integrins expressed by stimulated or no-stimulated chondrocytes. The results indicated that rhein leads to a reduction of IL-1beta synthesis whereas a weak decrease of beta1 integrins receptors expression is observed. From this study, it seems that rhein partially reduce cytokine-induced intracellular IL-1beta production, and it has a weak action on alpha4/beta1 or alpha5/beta1 receptors.

Anthraquinones↗

PubMed2001

Sodium alginate sponges with or without sodium hyaluronate: in vitro engineering of cartilage.

Studies are underway to design biosystems containing embedded chondrocytes to fill osteochondral defects and to produce a tissue close to native cartilage. In the present report, a new alginate three-dimensional support for chondrocyte culture is described. A sodium alginate solution, with or without hyaluronic acid (HA), was freeze-dried to obtain large-porosity sponges. This formulation was compared with a hydrogel of the same composition. In the sponge formulation, macroscopic and microscopic studies demonstrated the formation of a macroporous network (average pore size, 174 microm) associated with a microporous one (average pore size, 250 nm). Histological and biochemical studies showed that, when loaded with HA, the sponge provides an adapted environment for proteoglycan and collagen synthesis by chondrocytes. Cytoskeleton organization was studied by three-dimensional fluorescence microscopy (CellScan EPR). Chondrocytes exhibit a marked spherical shape with a nonoriented and sparse actin microfilament network. Type II collagen was detected in both types of sponges (with or without HA) using immunohistochemistry. In conclusion, the sponge formulation affords new perspectives with respect to the in vitro production of "artificial" cartilage. Furthermore, the presence of hyaluronate within the alginate sponge mimics a functional environment, suitable for the production by embedded chondrocytes of an extracellular matrix.

Alginates↗

PubMed2001

[Quantitative expression of the adhesion receptors VLA-4, VLA-5, L-selectin, MAC-1, and ICAM-1 on the surface of CD34+ cells].

The aim of this work was to quantify by flow cytometry the main adhesion receptors on CD34+ cells. These cells were isolated from bone marrow (BM) or mobilized peripheral blood (PB). The proportions of CD34+/CD49d+ and CD34+/CD49e+ are weaker on PB cells, without quantitative expression variation. This phenotypic variation may induce CD34+ cells exist from BM into circulation, promoting the mobilization. The homing to the BM implicate the CD62L receptor, which expression was found more frequently and stronger on PB cells than on BM. The CD11b, CD18 and CD54 receptors are implicated in CD34+ cells adhesion to BM micro-environment. No significant variation in CD34+/CD11b+ and CD34+/CD18+ cells frequency was noted. Moreover, CD54 receptor was more frequently expressed on PB cells. Quantitative analysis revealed that CD18 was more strongly expressed on BM than on PB cells. This quantitative variation could promote progenitor adhesion by interacting with stromal cells. Finally, quantitative expression of the main receptors on CD34+ cells provides an original option for studying CD34+ cells during the mobilization, the homing or the adhesion to BM micro-environment.

Antigens, CD↗

PubMed2001

Effects of three Hb-based oxygen-carrying solutions on neutrophil activation in vitro: quantitative measurement of the expression of adherence receptors.

BACKGROUND: Hb-based oxygen carriers (HbOCs) are currently under investigation as RBC substitutes. These solutions have vasoactive properties and may modify the behavior of the RBC in vitro. The effects of these agents on other blood cells have not been extensively investigated. The aim of this study was to evaluate the potential effect(s) of three differently modified HbOCs on the activation of PMNs. STUDY DESIGN AND METHODS: Whole blood from humans was incubated with Hb dextran-benzene-tetracarboxylate, alphaalpha-Hb, or o-raffinose-poly-Hb for 15, 30, and 60 minutes. The expression of adherence receptors CD62L, CD18, and CD11b, which reflects the activation state of the neutrophils, was assessed in vitro by a direct immunofluorescence method using calibration beads measured by flow cytometry. RESULTS: The observed expression of each of the three adherence receptors for each solution at each time point was similar to that noted with the RPMI control. Decreases in CD62L and increases in CD18 expression were noted at 15 minutes of incubation but, when those values were compared to the values obtained with TNFalpha as the positive control of PMN activation, the profile of expression of adherence receptors obtained with HbOC solutions did not conform to the expected activation profile of PMNs. CONCLUSION: Hb solutions modified by a variety of methods, as obtained and employed in this study, did not appear to activate neutrophils in vitro.

Aspirin↗

PubMed2001

Quantitative expression of adhesion molecules on granulocyte colony-stimulating factor-mobilized peripheral blood, bone marrow, and cord blood CD34+ cells.

The purpose of this study is to investigate the function of the main adhesion receptors on CD34(+) cells during hematopoietic stem cell transplantation. Expression was quantified by flow cytometry using calibration beads. CD34(+) cells were isolated from either bone marrow (BM), cord blood (CB), or peripheral blood (PB) from study patients and a control group after granulocyte colony-stimulating factor (G-CSF) administration. The study of the CD34(+) cell differentiation showed that CD34(+) cells are mainly CD38(+) and HLA-DR(+), whatever the type of harvest. However, quantitative analysis elicited a weaker expression of CD38 on PB and CB CD34(+) cells in comparison to BM CD34(+) cells. The proportions of CD34(+)/CD49d(+) and CD34(+)/CD49e(+) were smaller on PB cells, without quantitative expression variation. This phenotypic variation promotes CD34(+) cells to exit from BM into circulation, inducing the mobilization. The homing of the CD34(+) cells to the BM involves the CD62L receptor. The expression of this receptor was found to be more frequent and stronger on PB cells than on BM or CB cells. The CD11b, CD18, and CD54 receptors are implicated in CD34(+) cell adhesion to BM microenvironment. No significant variation in CD34(+)/CD11b(+) and CD34(+)/CD18(+) cell frequency was noted. Moreover, the CD54 receptor was more frequently expressed on CB and PB cells. Quantitative analysis revealed that CD18 was more strongly expressed on BM than on PB cells to promote progenitors adhesion by interacting with stromal cells. Finally, the quantitative expression of the main receptors on CD34(+) cells explained cellular functions during the different steps of hematopoietic stem cells transplantation.

ADP-ribosyl Cyclase↗

PubMed2001

Investigation of 3-D mechanical properties of blood vessels using a new in vitro tests system: results on sheep common carotid arteries.

In order to investigate the three-dimensional (3-D) mechanical properties of blood vessels, a new experimental device is described allowing in vitro static and dynamic measurements on segments of arteries with high technical performances. Static tests are applied to sheep common carotid arteries. Considering a thick-walled cylindrical model of orthotropic material under large deformations, a classical 3-D approach based on strain energy density is used to calculate the resulting mechanical behavior law in radial and circumferencial directions and stresses distribution throughout the wall thickness. Results are presented with reference to unloaded and zero-stress initial state thanks to simple measurements of inner and outer circumferences. A particular ratio relating the two main stresses (circumferential and longitudinal) is calculated that put into the forth the progressive modifications in the direction of the predominant stress in the wall and the specific radial location where these changes occur. We observe that this point location is a function of the test conditions of the specimen, i.e., stretching length and level of pressure.

Animals↗

PubMed2001

[Introduction to vascular engineering].

Vascular engineering developed through advancing knowledge of the physiological and pathological processes operating in cells and tissues subjected to environmental mechanical stress. We review briefly the more relevant cellular and general mechanism characteristic of vascular tissue examining the performances obtained with prosthetic materials (allografts, synthetic grafts) and current research and development of new vessel substitutes (biohybrids or biovessels).

Biomechanical Phenomena↗