Low-energy electron beam sterilization of solid alginate and chitosan, and their polyelectrolyte complexes.

Polysaccharidic scaffolds hold great hope in regenerative medicine, however their sterilization still remains challenging since conventional methods are deleterious. Recently, electron beams (EB) have raised interest as emerging sterilization techniques. In this context, the aim of this work was to study the impact of EB irradiations on polysaccharidic macroporous scaffolds. The effects of continuous and pulsed low energy EB were examined on polysaccharidic or on polyelectrolyte complexes (PEC) scaffolds by SEC-MALLS, FTIR and EPR. Then the scaffolds' physicochemical properties: swelling, architecture and compressive modulus were investigated. Finally, sterility and in vitro biocompatibility of irradiated scaffolds were evaluated to validate the effectiveness of our approach. Continuous beam irradiations appear less deleterious on alginate and chitosan chains, but the use of a pulsed beam limits the time of irradiation and better preserve the architecture of PEC scaffolds. This work paves the way for low energy EB tailor-made sterilization of sensitive porous scaffolds.

Alginate-chitosan PEC scaffolds: A useful tool for soft tissues cell therapy.

In this study we evaluate macroporous scaffolds made of alginate-chitosan polyelectrolyte complexes (PEC) as tools to optimize the results of soft tissues cell therapy. Cell therapy using mesenchymal stem cells (MSC) has become attractive for tissue repair and regeneration in a number of acute and chronic injuries. Unfortunately their low retention and/or survival after injection limit their beneficial effects. A biomaterial-assisted implantation, providing cells a three-dimensional (3D) microenvironment is a promising strategy. To this purpose, we designed a family of PEC scaffolds, and studied if they could meet the requirement of such application. Xray tomography showed that all PEC scaffolds present an interconnected macroporosity, and both rheology and tensile measurements reveal optimized mechanical properties (higher storage moduli and Young moduli) compared to alginate reference scaffolds. In vitro assays demonstrated their ability to allow MSC retention (higher than 90%), long-term viability and FGF2 secretion. Then, we used a skeletal muscle implantation model to assess the biological response to scaffolds graft, and showed that they support in vivo vascular formation within the implant-derived tissue. The combination of alginate/chitosan PEC scaffolds architecture and angiogenic potential make them appear as interesting tools to optimize MSC therapy results in soft tissues.

A CD103+ Conventional Dendritic Cell Surveillance System Prevents Development of Overt Heart Failure during Subclinical Viral Myocarditis.

Innate and adaptive immune cells modulate heart failure pathogenesis during viral myocarditis, yet their identities and functions remain poorly defined. We utilized a combination of genetic fate mapping, parabiotic, transcriptional, and functional analyses and demonstrated that the heart contained two major conventional dendritic cell (cDC) subsets, CD103+ and CD11b+, which differentially relied on local proliferation and precursor recruitment to maintain their tissue residency. Following viral infection of the myocardium, cDCs accumulated in the heart coincident with monocyte infiltration and loss of resident reparative embryonic-derived cardiac macrophages. cDC depletion abrogated antigen-specific CD8+ T cell proliferative expansion, transforming subclinical cardiac injury to overt heart failure. These effects were mediated by CD103+ cDCs, which are dependent on the transcription factor BATF3 for their development. Collectively, our findings identified resident cardiac cDC subsets, defined their origins, and revealed an essential role for CD103+ cDCs in antigen-specific T cell responses during subclinical viral myocarditis.