Antibiotics induce sustained dysregulation of intestinal T cell immunity by perturbing macrophage homeostasis

Macrophages in the healthy intestine are highly specialized and usually respond to the gut microbiota without provoking an inflammatory response. A breakdown in this tolerance leads to inflammatory bowel disease (IBD), but the mechanisms by which intestinal macrophages normally become conditioned to promote microbial tolerance are unclear. Strong epidemiological evidence linking disruption of the gut microbiota by antibiotic use early in life to IBD indicates an important role for the gut microbiota in modulating intestinal immunity. Here, we show that antibiotic use causes intestinal macrophages to become hyperresponsive to bacterial stimulation, producing excess inflammatory cytokines. Re-exposure of antibiotic-treated mice to conventional microbiota induced a long-term, macrophage-dependent increase in inflammatory T helper 1 (T 1) responses in the colon and sustained dysbiosis. The consequences of this dysregulated macrophage activity for T cell function were demonstrated by increased susceptibility to infections requiring T 17 and T 2 responses for clearance (bacterial and helminth infections), corresponding with increased inflammation. Short-chain fatty acids (SCFAs) were depleted during antibiotic administration; supplementation of antibiotics with the SCFA butyrate restored the characteristic hyporesponsiveness of intestinal macrophages and prevented T cell dysfunction. Butyrate altered the metabolic behavior of macrophages to increase oxidative phosphorylation and also promoted alternative macrophage activation. In summary, the gut microbiota is essential to maintain macrophage-dependent intestinal immune homeostasis, mediated by SCFA-dependent pathways. Oral antibiotics disrupt this process to promote sustained T cell-mediated dysfunction and increased susceptibility to infections, highlighting important implications of repeated broad-spectrum antibiotic use

Design and in vivo evaluation of a molecularly defined acellular skin construct: Reduction of early contraction and increase in early blood vessel formation

Item does not contain fulltextSkin substitutes are of great benefit in the treatment of patients with full thickness wounds, but there is a need for improvement with respect to wound closure with minimal contraction, early vascularisation, and elastin formation. In this study we designed and developed an acellular double-layered skin construct, using matrix molecules and growth factors to target specific biological processes. The epidermal layer was prepared using type I collagen, heparin and fibroblast growth factor 7 (FGF7), while the porous dermal layer was prepared using type I collagen, solubilised elastin, dermatan sulfate, heparin, fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor (VEGF). The construct was biochemically and morphologically characterised and evaluated in vivo using a rat full thickness wound model. The results were compared with the commercial skin substitute IntegraDRT and untreated wounds. The double-layered construct was prepared according to the design specifications. The epidermal layer was about 40 mum thick, containing 9% heparin and 0.2 mug FGF7 mg per layer, localised at the periphery. The dermal layer was 2.5 mm thick, had rounded pores and contained 10% dermatan sulfate+heparin, and 0.7 mug FGF2+VEGF mg per layer. The double-layered skin construct was implanted in a skin defect and on day 7, 14, 28 and 112 the (remaining) wound area was photographed, excised and (immuno) histologically evaluated. The double-layered skin construct showed more cell influx, significantly less contraction and increased blood vessel formation at early time points in comparison with IntegraDRT and/or the untreated wound. On day 14 the double-layered skin construct also had the fewest myofibroblasts present. On day 112 the double-layered skin construct contained more elastic fibres than IntegraDRT and the untreated wound. Structures resembling hair follicles and sebaceous glands were found in the double-layered skin construct and the untreated wound, but hardly any were found in IntegraDRT. The results provide new opportunities for the application of acellular skin constructs in the treatment of surgical wounds