A New Anthropomorphic Mannequin for Efficacy Evaluation of Thoracic Protective Equipment Against Blast Threats

Exposure to blast is one of the major causes of death and disability in recent military conflicts. Therefore, it is crucial to evaluate the protective capability of the ballistic-proof equipment worn by soldiers against the effects of blast overpressure (i.e., primary blast injuries). A focus will be made on thoracic protective equipment (TPE). An anthropomorphic mannequin, called BOPMAN, and anesthetized swine both wearing soft, hard or no ballistic protection, were subjected to an open-field high-intensity blast. For swine, thoracic wall motion (acceleration and velocity) was recorded during blast exposure and severity of lung injury was evaluated postmortem. Different data were collected from BOPMAN thoracic responses, including reflected and internal pressure, as well as the force at the rear face of the instrumented part. The severity of blast-induced lung injuries (contusion extent, Axelsson Severity Scale) and the thoracic wall motion were decreased in animals protected with thoracic ceramic hard plates as compared to those wearing soft or no protection. There was a clear trend towards greater lung injury in animals protected with the soft body armor used, even when compared to unprotected animals. In line with these experimental data, the measured force as well as the force impulse measured using BOPMAN were also decreased with a ceramic hard plate protection and increased when a soft ballistic pack was used compared to no protection. Comparison of data collected on BOPMAN and swine equipped with the same protection level revealed that those two force parameters were well correlated with the level of blast-induced lung injury (force, R² = 0.74 and force impulse, R² = 0.77, p < 0.05). Taken together, our results suggest that the force and the force impulse data from BOPMAN may help estimate the efficiency of existing TPE regarding lung protection under blast exposure and may represent an important tool for development of future TPE.

Cord blood-endothelial colony forming cells are immunotolerated and participate at post-ischemic angiogenesis in an original dorsal chamber immunocompetent mouse model

BACKGROUND

Cardiovascular diseases are the main cause of morbidity and mortality worldwide. Restoring blood supply to ischemic tissues is an essential goal for the successful treatment of these diseases. Growth factor or gene therapy efficacy remains controversial, but stem cell transplantation is emerging as an interesting approach to stimulate angiogenesis. Among the different stem cell populations, cord blood-endothelial progenitor cells (CB-EPCs) and more particularly cord blood-endothelial progenitor cell-derived endothelial colony forming cells (CB-ECFCs) have a great proliferative potential without exhibiting signs of senescence. Even if it was already described that CB-ECFCs were able to restore blood perfusion in hind-limb ischemia in an immunodeficient mouse model, until now, the immunogenic potential of allogenic CB-ECFCs remains controversial. Therefore, our objectives were to evaluate the immune tolerance potency of CB-ECFCs and their capacity to restore a functional vascular network under ischemic condition in immunocompetent mice.

METHODS

In vitro, the expression and secretion of immunoregulatory markers (HLA-G, IL-10, and TGF-β1) were evaluated on CB-ECFCs. Moreover, CB-ECFCs were co-cultured with activated peripheral blood mononuclear cells (PBMCs) for 6 days. PBMC proliferation was evaluated by [3H]-thymidine incorporation on the last 18 h. In vivo, CB-ECFCs were administered in the spleen and muscle of immunocompetent mice. Tissues were collected at day 14 after surgery. Finally, CB-ECFCs were injected intradermally in C57BL/6JRj mice close to ischemic macrovessel induced by thermal cauterization. Mice recovered until day 5 and were imaged, twice a week until day 30.

RESULTS

Firstly, we demonstrated that CB-ECFCs expressed HLA-G, IL-10, and TGF-β1 and secreted IL-10 and TGF-β1 and that they could display immunosuppressive properties in vitro. Secondly, we showed that CB-ECFCs could be tolerated until 14 days in immunocompetent mice. Thirdly, we revealed in an original ischemic model of dorsal chamber that CB-ECFCs were integrated in a new functional vascular network.

CONCLUSION

These results open up new perspectives about using CB-ECFCs as an allogeneic cell therapy product and gives new impulse to the treatment of cardiovascular diseases.

Heterogeneous functions of perinatal mesenchymal stromal cells require a preselection before their banking for clinical use

Perinatal sources of mesenchymal stromal cells (MSCs) have raised growing interest because they are readily and widely available with minimal ethical/legal issues and can easily be stored for allogeneic settings. In addition, perinatal tissues are known to be important in mediating the fetomaternal tolerance of pregnancy, which confer upon perinatal-MSCs (P-MSCs) a particular interest in immunomodulation. It has been recently shown that it is possible to deeply modify the secreted factor profiles of MSCs with different cytokine stimuli such as interferon gamma or tumor necrosis factor alpha to license MSCs for a better immunosuppresive potential. Therefore, we aimed to compare adult bone marrow-MSCs with MSCs from perinatal tissues (cord blood, umbilical cord, amnion, and chorion) on their in vitro immunological and stromacytic efficiencies under different priming conditions. Our results showed that P-MSCs had a potential to modulate the in vitro immune response and be useful for hematopoietic progenitor cell ex vivo expansion. However, we showed contrasted effects of cytokine priming embedded in an important between-donor variability. In conclusion, our study highlights the importance to elaborate predicitive in vitro tests to screen between-donor variability of perinatal tissues for banking allogeneic standardized MSCs.

Kidney transplant recipients treated with belatacept exhibit increased naïve and transitional B cells

Phase III clinical studies have shown that kidney transplant (KT) recipients treated with the costimulation blocker belatacept exhibited a better renal allograft function and lower donor-specific anti-HLA immunization when compared to recipients treated with calcineurin inhibitors (CNI). We analyzed B cell phenotype in KT recipients treated with belatacept and stable renal function (N = 13). Results were compared to those observed in stable patients treated with CNI (N = 12), or with chronic antibody-mediated rejection (N = 5). Both transcriptional profile and phenotypic characterization of peripheral B cells were performed by real-time polymerase chain reaction and flow cytometry, respectively. In belatacept group, the frequency and absolute number of transitional B cells as defined by both phenotypes: CD19(+) CD24(hi) CD38(hi) and CD19(+) IgD(hi) CD38(hi) CD27(-) , as well as naïve B cells were significantly higher compared with CNI group. B cell activating factor (BAFF) and BAFF receptor mRNA levels were significantly lower in belatacept group than in CNI group. These results show for the first time that belatacept influences B cell compartment by favoring the occurrence of transitional B cells with potential regulatory properties, as described in operational tolerant patients. This role may explain the lower alloimmunization rate observed in belatacept-treated patients.

In vivo evidence that secretion of HLA-G by immunogenic tumor cells allows their evasion from immunosurveillance

Human leukocyte antigen-G (HLA-G) expression by tumors has been evidenced in numerous malignancies in association with poor prognosis and resistance to immunotherapy in humans. Particularly, soluble form of HLA-G was measured at high concentrations in malignant effusions and plasma from cancer patients, and inhibits antitumor immune cells in vitro through interaction with immunoglobulin-like transcript (ILT) receptors. Nevertheless, in vivo study demonstrating that HLA-G secretion by tumor cells allows their escape from immunosurveillance remained to be established. Despite nondescribed murine homolog, direct functional interaction of HLA-G with murine paired immunoglobulin-like receptor (PIR)-B, ortholog of human ILT receptors, enables to investigate its role in vivo. Immunocompetent mice were injected either with syngeneic tumor cells co-expressing HLA-G5, the main soluble HLA-G isoform, and the conformation stabilizer human β2-microglubulin (hβ2m), or with hβ2m+ HLA-G5- tumor cells. hβ2m expressed at both tumor cell surface acted as a tumor antigen triggering a specific humoral response. Interestingly, although hβ2m+ HLA-G5- tumors were rejected, secreted HLA-G5 provided hβ2m+ HLA-G5+ tumors a protection against hβ2m-elicited immune rejection, enabling such immunogenic tumors to grow similarly to a poorly immunogenic tumor. HLA-G5 tumor expression was associated with local and peripheral immunosuppression, characterized by dampened anti-hβ2m B-cell response, quantitative and functional T-and B-cell defects, accumulation of myeloid-derived suppressor cells able to inhibit T-cell proliferation and reduced T- and B-cell tumor infiltrate. Our study provides the first in vivo proof that soluble HLA-G counteracts tumor rejection and reinforces the importance to consider HLA-G as a promising target to optimize current cancer immunotherapies.