Accumulation and transport of microbial-size particles in a pressure protected model burn unit: CFD simulations and experimental evidence.

BACKGROUND: Controlling airborne contamination is of major importance in burn units because of the high susceptibility of burned patients to infections and the unique environmental conditions that can accentuate the infection risk. In particular the required elevated temperatures in the patient room can create thermal convection flows which can transport airborne contaminates throughout the unit. In order to estimate this risk and optimize the design of an intensive care room intended to host severely burned patients, we have relied on a computational fluid dynamic methodology (CFD). METHODS: The study was carried out in 4 steps: i) patient room design, ii) CFD simulations of patient room design to model air flows throughout the patient room, adjacent anterooms and the corridor, iii) construction of a prototype room and subsequent experimental studies to characterize its performance iv) qualitative comparison of the tendencies between CFD prediction and experimental results. The Electricité De France (EDF) open-source software Code_Saturne® (http://www.code-saturne.org) was used and CFD simulations were conducted with an hexahedral mesh containing about 300 000 computational cells. The computational domain included the treatment room and two anterooms including equipment, staff and patient. Experiments with inert aerosol particles followed by time-resolved particle counting were conducted in the prototype room for comparison with the CFD observations. RESULTS: We found that thermal convection can create contaminated zones near the ceiling of the room, which can subsequently lead to contaminate transfer in adjacent rooms. Experimental confirmation of these phenomena agreed well with CFD predictions and showed that particles greater than one micron (i.e. bacterial or fungal spore sizes) can be influenced by these thermally induced flows. When the temperature difference between rooms was 7°C, a significant contamination transfer was observed to enter into the positive pressure room when the access door was opened, while 2°C had little effect. Based on these findings the constructed burn unit was outfitted with supplemental air exhaust ducts over the doors to compensate for the thermal convective flows. CONCLUSIONS: CFD simulations proved to be a particularly useful tool for the design and optimization of a burn unit treatment room. Our results, which have been confirmed qualitatively by experimental investigation, stressed that airborne transfer of microbial size particles via thermal convection flows are able to bypass the protective overpressure in the patient room, which can represent a potential risk of cross contamination between rooms in protected environments.

In vitro and in vivo analysis of endothelial progenitor cells from cryopreserved umbilical cord blood: are we ready for clinical application?

Umbilical cord blood (CB) represents a main source of circulating endothelial progenitor cells (cEPCs). In view of their clinical use, in either the autologous or allogeneic setting, cEPCs should likely be expanded from CB kept frozen in CB banks. In this study, we compared the expansion, functional features, senescence pattern over culture, and in vivo angiogenic potential of cEPCs isolated from fresh or cryopreserved CB (cryoCB). cEPCs could be isolated in only 59% of cryoCB compared to 94% for fresh CB, while CB units were matched in terms of initial volume, nucleated and CD34(+) cell number. Moreover, the number of endothelial colony-forming cells was significantly decreased when using cryoCB. Once cEPCs culture was established, the proliferation, migration, tube formation, and acetylated-LDL uptake potentials were similar in both groups. In addition, cEPCs derived from cryoCB displayed the same senescence status and telomeres length as that of cEPCs derived from fresh CB. Karyotypic aberrations were found in cells obtained from both fresh and cryoCB. In vivo, in a hind limb ischemia murine model, cEPCs from fresh and cryoCB were equally efficient to induce neovascularization. Thus, cEPCs isolated from cryoCB exhibited similar properties to those of fresh CB in vitro and in vivo. However, the low frequency of cEPCs colony formation after cryopreservation shed light on the need for specific freezing conditions adapted to cEPCs in view of their future clinical use.

Bone marrow microenvironment in fanconi anemia: a prospective functional study in a cohort of fanconi anemia patients.

Fanconi anemia (FA) is a rare condition due to the genetic inactivation of the FA/BRCA pathway. During childhood, most FA patients display progressive bone marrow failure (BMF), the mechanism of which has not been clarified to date. We analyzed BM mesenchymal stem cells (MSCs) from a series of 20 FA patients with BMF (patient median age 12.5 years old, range 7-34). Expression of FANCD2 and sensitivity to mitomycin C, differentiation capacities, and hematopoiesis-supporting abilities, as well as proliferation, cell senescence, and telomere length were assessed. FA MSCs demonstrated hypersensitivity to mitomycin C compared to control MSCs, as expected for FA cells. FA MSCs had normal immunophenotype, support long-term culture of hematopoietic stem cells (HSCs), and display normal differentiation capacities. Telomere loss during cell aging was similar for FA and control MSCs. However, FA MSCs showed reduced long-term proliferation ability, higher stem cell factor and interleukin-6 levels, and increased expression of senescent-associated beta-galactosidase compared to normal MSCs, suggesting a potential role of the BM microenvironment in long-term BMF.

Influence of bone marrow graft B lymphocyte subsets on outcome after HLA-identical sibling transplants.

The potential role of the infused B cell subset after Hematopoietic Stem Cell Transplantation has not been yet studied. The present study analyzed the impact of B cells on transplant outcome in 254 patients who received a bone marrow graft from a human leucocyte antigen-identical sibling donor. The influence of B lineage-specific hematopoietic progenitor cells (CD34(+) CD19(+)) and B cells (immature and mature B cells, CD34(-) CD19(+)) was also analyzed. All included patients received a myeloablative regimen. The cumulative incidence function of acute graft-versus-host (GvHD) grade II to IV was 48% and was inversely associated with the number of CD34(+) CD19(+). There were no statistically significant associations between B cell subsets and chronic GvHD or survival. The CD34(+) CD19(+) B cell subset remained significantly associated with acute GvHD in multivariate analysis (Relative risk = 0.32, 95% confidence interval: 0.11-0.92, P = 0.035). In conclusion, a higher B lineage-specific hematopoietic progenitor cells (CD34(+) CD19(+)) cell dose is associated with a significant decrease incidence of acute GvHD.

Tissue engineering for full-thickness burns: a dermal substitute from bench to bedside.

Our aim was to obtain a viable and easily available dermal substitute (DS) for the definitive coverage of full-thickness burns. A DS composed of a collagen-glycosaminoglycan-chitosan dermal matrix (DM) colonized with foreskin fibroblasts (FF) is described. FF-colonized DS were compared to the DM seeded with adult dermal fibroblasts (DF). FF-colonized DS expressed more fibrillin and tropoelastin than that with DF. Reconstructed skin obtained with both FF- and DF-colonized DS similarly expressed laminin-5 and collagen VII at the dermal-epidermal junction. Both FF- and DF-colonized DS produced cutaneous wound healing mediators in a dose-dependent manner in the presence of platelet lysate. After freeze-thawing, the FF-colonized DS were recovered in culture and retained their ability to produce vascular endothelial growth factor. Grafting of DS into nude rats achieved a complete healing of a dermal-epidermal lesion with a good epidermalization.

Association of bone marrow natural killer cell dose with neutrophil recovery and chronic graft-versus-host disease after HLA identical sibling bone marrow transplants.

Allogeneic bone marrow (BM) transplant (BMT) outcomes have been correlated with the infused nucleated, CD34(+), and T- cell dose. The potential impact of natural killer (NK) BM infused cell dose has however not been established. We analysed the outcomes of 78 patients receiving an HLA identical BMT. A higher NK cell dose was associated with the speed of neutrophil (P = 0.05) and platelet recovery (P = 0.04). Higher nucleated cells, CD34(+), CD3(+), CD3(+)/4(+), CD3(+)/8(+) and NK cell dose were associated with a lower incidence of chronic GvHD (cGvHD) in univariate analysis. In multivariate analysis, the risk of cGvHD was increased by a lower NK cell dose [hazard ratio (HR) = 2.3 (1.2-4.4) for cell dose <0.9 x 10(6)/kg; P = 0.01] and an older age [HR = 1.4 /10 years (1.1-1.8); P = 0.002]. In addition, a higher CD3(+)/4(+) and NK cell dose were associated with a decreased incidence of viral infections (P = 0.03 and P = 0.06 respectively). No specific cell subpopulation infused dose was associated with survival. In conclusion, a higher BM NK cell dose is associated with an increased speed of neutrophil recovery and a decreased incidence of cGvHD.

Ex vivo generation of mature and functional human smooth muscle cells differentiated from skeletal myoblasts.

We described the ex vivo production of mature and functional human smooth muscle cells (SMCs) derived from skeletal myoblasts. Initially, myoblasts expressed all myogenic cell-related markers such as Myf5, MyoD and Myogenin and differentiate into myotubes. After culture in a medium containing vascular endothelial growth factor (VEGF), these cells were shown to have adopted a differentiated SMC identity as demonstrated by alphaSMA, SM22alpha, calponin and smooth muscle-myosin heavy chain expression. Moreover, the cells cultured in the presence of VEGF did not express MyoD anymore and were unable to fuse in multinucleated myotubes. We demonstrated that myoblasts-derived SMCs (MDSMCs) interacted with endothelial cells to form, in vitro, a capillary-like network in three-dimensional collagen culture and, in vivo, a functional vascular structure in a Matrigel implant in nonobese diabetic-severe combined immunodeficient mice. Based on the easily available tissue source and their differentiation into functional SMCs, these data argue that skeletal myoblasts might represent an important tool for SMCs-based cell therapy.

Epstein-Barr virus early-antigen antibodies before allogeneic haematopoietic stem cell transplantation as a marker of risk of post-transplant lymphoproliferative disorders.

The occurrence of post-transplant lymphoproliferative disorders (PTLDs) after allogeneic haematopoietic stem cell transplantation (allo-HSCT) represents a clinical problem. Pretransplant Epstein-Barr virus serological status and viral load was determined in 21 recipients and 28 control transplanted patients, with (+) and without (-) PTLD, respectively. Early-antigen immunoglobulin G (EA-IgG) was detected in 12/21 PTLD+ patients, but only 2/28 PTLD patients (P = 0.00023, Odds ratio = 17.42). High viral load was detected in peripheral blood mononuclear cells at PTLD diagnosis, independently of deleted LMP1. Detection of EA-IgG in allo-HSCT recipients pretransplantation might be considered as risk factor for PTLD development.

Quantification of nucleated red blood cells in allogeneic marrow graft and impact of processing on recovery.

BACKGROUND: In allogeneic bone marrow transplantation (BMT), a higher nucleated and CD34+ cell dose has been reported to improve various outcomes. Other cell types, such as lymphocyte subsets, also influenced BMT results. While nucleated red blood cells (NRBCs) represent a subset of bone marrow (BM) cell subpopulation, the question of their quantification in BM grafts and the impact of BM processing on their recovery has not been addressed. STUDY DESIGN AND METHODS: In a prospective study on 77 BM products, NRBCs were enumerated by flow cytometry and the recovery analyzed after manipulation. Because NRBCs could compromise white blood cell count, the impact of NRBC count on CD34+ cell percentage and total nucleated cell (TNC) dose were also determined. RESULTS: The mean percentage of NRBCs in BM grafts was 21.6 percent (range, 7.8%-40.9%). Mean NRBC recoveries after BM concentration or RBC depletion were 98.4 and 28.7 percent, respectively, close to those obtained for TNC cells (88.6 and 31.3%, respectively). When corrected with NRBC count, the mean percentages of corrected CD34+ cell and TNC dose were significantly modified when compared with uncorrected values, whatever the type of BM manipulation. CONCLUSION: Our data show that NRBC quantification might be of importance to improve quality control of BM products and to evaluate the influence of NRBCs cell dose on outcomes after BMT.

ABO-mismatched marrow processing for transplantation: results of 114 procedures and analysis of immediate adverse events and hematopoietic recovery.

BACKGROUND: Red cell (RBC) depletion is needed to bypass ABO mismatch in allogeneic bone marrow transplantation (BMT). Technical and clinical data obtained after bone marrow (BM) processing with a continuous-flow cell separator (Cobe Spectra, Gambro BCT) are reported. STUDY DESIGN AND METHODS: RBC depletion and recovery of nucleated cells, CD3+ cells, CD34+ cells, and colony-forming unit-granulocyte-macrophage were calculated. Bacteriologic contaminations, side effects of graft infusion, and hematopoietic recovery were analyzed. RESULTS: A total of 114 BM samples were processed. The mean volume collected was 1099 mL (range, 390-2450 mL). Initial and residual mean RBCs volumes were 309.9 and 4.0 mL corresponding to a depletion of 98.6 +/- 0.78 percent. Before processing, the mean numbers of nucleated cells, granulocytes, CD3+ cells, CD34+ cells, and CFU-GM were 20.28 x 10(9), 12.79 x 10(9), 1.96 x 10(9), 356.7 x 10(6), and 195.6 x 10(5), respectively. The mean corresponding recoveries after processing were 33.66, 48.98, 82.02, 82.2, and 93.9 percent. Limited side effects were observed in 14 patients without correlation with residual RBCs volume. All but two patients engrafted. CONCLUSION: BM processing with the Cobe Spectra cell separator provides high rates of RBC depletion without significant side effects after BMT.

Prospective flow cytometric evaluation of nucleated red blood cells in cord blood units and relationship with nucleated and CD34(+) cell quantification.

BACKGROUND: Cord blood (CB) represents an alternate source of stem cells in transplantation. Nucleated red blood cells (NRBCs) are a physiological subset of CB population. Although it is important to have an accurate estimate of CD34(+) cell number, NRBCs could compromise white blood cell count and interfere with CD34(+) cell quantification. STUDY DESIGN AND METHODS: A total of 826 CB units were analyzed for total nucleated cells (TNCs), NRBCs, and CD34(+) cells by flow cytometry. NRBCs were also counted conventionally by manual microscopy. Percentages of CD34(+) cells corrected by NRBC count (CD34+c) were determined as follows: %CD34+c = CD34(+)/CD45(+) (x10(6))/(TNCs (x10(8)) - NRBCs (x10(8))). RESULTS: The mean percentages of CD34+ cells and NRBCs were 0.27 percent (range, 0.01%-1.25%) and 7.64 percent (range, 0.13%-84%), respectively. Comparison between flow cytometric and microscopic NRBC count showed a regression of y = 0.685 + 0.719x and a coefficient of determination of r(2) = 0.721. When corrected with NRBC count, the mean percentage of CD34(+) c cells was 0.295 percent (p = 0.0008 compared with CD34(+)%) and mean TNCc count was 14.8 x 10(8) (p < 10(-4) compared to TNC count). CONCLUSION: The determination of NRBCs with a flow cytometric method might represent a new strategy for providing satisfactory quality assurance controls of CB products.

Long term hematologic recovery after autologous stem cell transplantation in lymphoma patients: impact of the number of prefreeze and post-thaw CD34+ cells.

BACKGROUND: Autologous Stem Cell Transplantation (ASCT) with Peripheral Blood Stem Cells is widely used as consolidation in lymphoma patients. The rapidity and stability of cell engraftment correlate with the number of CD34+ cells in the autograft. However, whether CD34+ cells should be quantified before or after cryopreservation remains unclear. PATIENTS AND METHODS: Of 173 consecutive patients who underwent ASCT in our department from Nov 1, 1995 to Nov 1, 2000, 133 (78 %) were alive without relapse at one year. We report here the results for 106 patients whose hematologic data were available. RESULTS: At one year, the hemoglobin was normal in 47% of the patients, the leukocytes, in 77% and the platelets, in 60%. Only 33% had a normal blood count. We observed a significant correlation between prefreeze and post-thaw CD34+ cell numbers (r = 0.77). However, multivariate analysis using the Cox model with smoothing splines to assess the best cut-off point for these numbers demonstrated that the only independent predictive factor for a normal blood count after one year was a prefreeze number of CD34+ cells above 5.10(6)/kg. CONCLUSION: An optimal long-term hematologic recovery after ASCT required a number of prefreeze CD34+ cells of at least 5.10(6)/kg.

Randomized trial and local biological effect of autologous platelets used as adjuvant therapy for chronic venous leg ulcers.

OBJECTIVES: Platelet products have been proposed as adjuvant therapy for wound healing. We undertook this study to determine the healing effect of topically applied frozen autologous platelets (FAP) on chronic venous ulcers, compared with effect of placebo, and whether use of topical FAP modifies local expression of vascular endothelial growth factor (VEGF), keratinocyte growth factor (KGF), interleukin 8 (IL-8), and tissue inhibitor of metalloproteinase-1 (TIMP-1) in wound fluid. METHODS: This randomized, placebo-controlled, double-blind trial was carried out in institutional practice, with ambulatory patients with proved chronic venous leg ulcers. In all patients, whole venous blood was drawn for preparation of FAP. FAP or normal saline solution was applied three times per week for up to 12 weeks, together with hydrocolloids and standardized compression bandages. Leg ulcer surface was assessed with numerical pictures. IL-8, VEGF, KGF, and TIMP-1 levels were determined (enzyme-linked immunosorbent assay) in wound fluid after each 4 weeks of treatment. RESULTS: Fifteen patients were randomized into two groups with comparable leg ulcer characteristics. Mean percent reduction in ulcer area was 26.2% in the FAP group versus 15.2% in the placebo group (P =.94). One ulcer in each group was completely healed at study end. Levels of TIMP-1 increased significantly during FAP treatment. IL-8 concentration was significantly lower in wound fluid of healing ulcers than in the fluid of nonhealing ulcers, in both FAP and placebo groups. Growth factor levels were not modified with FAP treatment. CONCLUSION: Topical autologous platelets have no significant adjuvant effect on healing of chronic venous leg ulcers and increased wound fluid TIMP-1 concentration. Ulcer healing is associated with a decrease in wound fluid IL-8.

Wound healing mediator production by human dermal fibroblasts grown within a collagen-GAG matrix for skin repair in humans.

Cell and tissue therapy applications in humans are being used increasingly, particularly for tissue repair. Several reconstructed skin models have been proposed. Wound healing involves overlapping steps of inflammation, cell migration and proliferation, neovascularisation, extracellular matrix production and remodelling. This is regulated by numerous cytokines and other soluble mediators. We have prepared dermal substitutes (DS) consisting of a collagen-GAG, three-dimensional matrix colonized by human dermal fibroblasts (HDF), isolated by skin explant or enzymatic digestion of the skin for potential therapeutic use in humans. To test the functionality of these DS, we measured (ELISA) the stimulatory effect on HDF in the matrix, of serial dilutions of human serum (HS) on the production of wound healing mediators: interleukin-8 (IL-8), vascular endothelial growth factor (VEGF), keratinocyte growth factor (KGF) and tissue inhibitor of metalloproteinase-1 (TIMP-1). We observed: 1). a stimulatory effect of HS on HDF production of the different mediators tested, with a dose-dependent effect in the case of IL-8 and VEGF. 2). A matrix-potentiating effect on the production of the different mediators by HDF. 3). A decrease in the production of IL-8 and VEGF when HDF isolated by enzymatic digestion was used to colonize the matrix as compared with HDF isolated by skin explant. We conclude: 1). that the production by HDF, in a collagen-GAG matrix, of mediators involved in cutaneous wound healing is decreased when HDF are isolated by enzymatic skin digestion rather than by skin explant. 2). That measurement of the production of cytokines or other mediators could be a useful quality control to test the functionality of tissue-engineered DS for tissue repair therapy in humans and more generally of cells prepared for cell therapy.

Autologous skeletal myoblast transplantation for severe postinfarction left ventricular dysfunction.

OBJECTIVES: This phase I trial was designed to assess the feasibility and safety of autologous skeletal myoblast transplantation in patients with severe ischemic cardiomyopathy. BACKGROUND: Experimentally, myoblast grafting into postinfarction myocardial scars improves left ventricular function. METHODS: Ten patients were included on the basis of the following criteria: 1) severe left ventricular dysfunction (ejection fraction < or = 35%); 2) the presence of a postinfarction akinetic and nonviable scar, as assessed by dobutamine echocardiography and 18-fluorodeoxyglucose positron emission tomography; and 3) an indication of coronary bypass in remote areas. Skeletal myoblasts were grown from a biopsy taken at the thigh. RESULTS: An average of 871 x 10(6) cells (86% of myoblasts) were obtained after a mean period of 16 days and implanted uneventfully across the scar at the time of bypass. Except for one patient whose early death was unrelated to the cell transplantation, all patients had an uncomplicated postoperative course. Four patients showed delayed episodes of sustained ventricular tachycardia and were implanted with an internal defibrillator. At an average follow-up of 10.9 months, the mean New York Heart Association functional class improved from 2.7 +/- 0.2 preoperatively to 1.6 +/- 0.1 postoperatively (p < 0.0001), and the ejection fraction increased from 24 +/- 1% to 32 +/- 1% (p < 0.02). A blinded echocardiographic analysis showed that 63% of the cell-implanted scars (14 of 22) demonstrated improved systolic thickening. One noncardiac death occurred 17.5 months after transplantation. CONCLUSIONS: These preliminary data suggest the feasibility and safety of autologous skeletal myoblast transplantation in severe ischemic cardiomyopathy, with the caveat of an arrhythmogenic potential. New-onset contraction of akinetic and nonviable segments suggests a functional efficacy that requires confirmation by randomized studies.