Alginate encapsulant incorporating CXCL12 supports long-term allo- and xenoislet transplantation without systemic immune suppression.

Islet transplantation represents a potentially curative approach for individuals with Type I Diabetes. The requirement for systemic immune suppression to control immune-mediated rejection of transplanted islets and the limited human islet supply represent significant roadblocks to progress for this approach. Islet microencapsulation in alginate offers limited protection in the absence of systemic immunosuppression, but does not support long-term islet survival. The chemokine, CXCL12, can repel effector T cells while recruiting immune-suppressive regulatory T cells (Tregs) to an anatomic site while providing a prosurvival signal for beta-cells. We proposed that coating or encapsulating donor islets with CXCL12 would induce local immune-isolation and protect and support the function of an allo- or xenograft without systemic immune suppression. This study investigated the effect of alginate microcapsules incorporating CXCL12 on islet function. Islet transplantation was performed in murine models of insulin-dependent diabetes. Coating of islets with CXCL12 or microencapsulation of islets with alginate incorporating the chemokine, resulted in long-term allo- and xenoislet survival and function, as well as a selective increase in intragraft Tregs. These data support the use of CXCL12 as a coating or a component of an alginate encapsulant to induce sustained local immune-isolation for allo- or xenoislet transplantation without systemic immunosuppression.

Treatment of experimental esophagogastric myotomy with bone marrow mesenchymal stem cells in a rat model.

BACKGROUND: Over the last 15 years, many studies demonstrated the myogenic regenerative potential of bone marrow mesenchymal stem cells (BM-MSC), making them an attractive tool for the regeneration of damaged tissues. In this study, we have developed an animal model of esophagogastric myotomy (MY) aimed at determining the role of autologous MSC in the regeneration of the lower esophageal sphincter (LES) after surgery. METHODS: Syngeneic BM-MSC were locally injected at the site of MY. Histological and functional analysis were performed to evaluate muscle regeneration, contractive capacity, and the presence of green fluorescent protein-positive BM-MSC (BM-MSC-GFP(+) ) in the damaged area at different time points from implantation. KEY RESULTS: Treatment with syngeneic BM-MSC improved muscle regeneration and increased contractile function of damaged LES. Transplanted BM-MSC-GFP(+) remained on site up to 30 days post injection. Immunohistochemical analysis demonstrated that MSC maintain their phenotype and no differentiation toward smooth or striated muscle was shown at any time point. CONCLUSIONS & INFERENCES: Our data support the use of autologous BM-MSC to both improve sphincter regeneration of LES and to control the gastro-esophageal reflux after MY.

Manipulation of dendritic cells for host defence against intracellular infections.

Dendritic cells (DCs) are an important innate immune cell type which is the bridge between innate and adaptive immunity. Mounting experimental evidence suggests that manipulating DCs represents a powerful means to enhance host defence against intracellular infectious diseases. We have developed several strategies to manipulate DCs either in vivo or in vitro for the purpose of enhancing the effect of vaccination or immunotherapeutics. In vivo delivery of transgene encoding GM-CSF (granulocyte/macrophage colony-stimulating factor), a DC-activating cytokine, increases the number and activation status of DCs at various tissue sites and enhances antimicrobial immune responses in murine models. Co-expression or co-delivery of GM-CSF gene transfer vector with an antimicrobial vaccine enhances microbial antigen-specific T-cell responses and immune protection. Murine bone marrow-derived DCs are being manipulated in vitro and exploited as a vaccine delivery system. Transduction of DCs with a virus-vectored tuberculosis vaccine is a powerful way to activate T-cells in vivo. Such genetically modified DC vaccines can be administered either parenterally or mucosally via the respiratory tract.

Role of IL-12 in macrophage activation during intracellular infection: IL-12 and mycobacteria synergistically release TNF-alpha and nitric oxide from macrophages via IFN-gamma induction.

IL-12 is believed to play an important role in cell-mediated immunity against intracellular infection primarily by acting on T and NK cells. Recent evidence has suggested, however, that IL-12 has broader cellular targets than previously thought. In this study, we examined the role of IL-12 in macrophage TNF-alpha and nitric oxide (NO) release by using an in vitro model of intracellular infection. IL-12 alone released relatively little TNF-alpha and NO, whereas live mycobacteria alone released TNF-alpha markedly but little NO from murine alveolar macrophages. However, IL-12 and mycobacteria together enhanced TNF-alpha and NO release synergistically. Because IL-12 and mycobacteria also released IFN-gamma from macrophages synergistically, and exogenous IFN-gamma with mycobacteria enhanced TNF-alpha and NO release synergistically, we examined the role of endogenous IFN-gamma in IL-12/mycobacteria-stimulated macrophage activation. Using macrophages from mice deficient in IFN-gamma, we found that IL-12/mycobacteria-enhanced macrophage TNF-alpha and NO release was mediated through endogenous IFN-gamma. We further demonstrated that IFN-gamma and mycobacteria together had a selective effect on macrophage cytokine release because they released TNF-alpha synergistically but not macrophage chemotactic protein-1 (MCP-1). These findings reveal that IL-12 can activate macrophages potently during intracellular infection, and this activating effect is mediated primarily through its effect on macrophage IFN-gamma release.