Efficient wound repair is crucial for mammalian survival. Healing of skin wounds is severely hampered in diabetic patients, resulting in chronic non-healing wounds that are difficult to treat. High-mobility group box 1 (HMGB1) is an important signaling molecule that is released during wounding, thereby delaying regenerative responses in the skin. Here, we show that dissolving glycyrrhizin, a potent HMGB1 inhibitor, in water results in the formation of a hydrogel with remarkable rheological properties. We demonstrate that these glycyrrhizin-based hydrogels accelerate cutaneous wound closure in normoglycemic and diabetic mice by influencing keratinocyte migration. To facilitate topical application of glycyrrhizin hydrogels on cutaneous wounds, several concentrations of glycyrrhizinic acid in water were tested for their rheological, structural, and biological properties. By varying the concentration of glycyrrhizin, these hydrogel properties can be readily tuned, enabling customized wound care.

The choroid plexus (ChP), located in the brain ventricles, is largely composed of ChP epithelial cells that produce the cerebrospinal fluid (CSF) and form the blood–CSF barrier. At the ChP–brain attachment sites, we have discovered unique fibroblasts referred to as ChP base barrier cells (BBCs). We show that ChP BBCs originate from meningeal mesenchymal precursors, arrive early during development, remain throughout life and are conserved across species. ChP BBCs are transcriptionally similar to meningeal arachnoid barrier cells and are interconnected by both adherens and tight junctions. Notably, we provide evidence that the BBCs function as a barrier, controlling communication between the periphery and central nervous system. Moreover, during inflammatory insult, we observed a loss of barrier integrity and immune cell crossing. Altogether, our research revealed a barrier at the ChP base, crucial in protecting the central nervous system by compartmentalizing the ChP stroma, brain parenchyma and CSF.

Loss-of-function mutations in the human OTULIN gene, encoding a deubiquitinase with exclusive specificity for linear ubiquitin chains, cause a severe multi-organ autoinflammatory condition involving the skin ^1,2 . Mice lacking OTULIN selectively in keratinocytes develop inflamed skin lesions that progress into squamous tumours, a phenotype driven by excessive TNF-induced cell death ^3,4 . Previous studies suggested a role for OTULIN in mediating Wnt signalling during development ⁵ , but the physiological relevance of this association is unknown. Here, we show that OTULIN promotes Wnt signalling in keratinocytes by regulating the linear ubiquitination status of β-catenin. Stabilisation of β-catenin in OTULIN-deficient keratinocytes prevents progressive skin inflammation in prophylactic and therapeutic settings by blocking keratinocyte death. We demonstrate that linearly ubiquitinated β-catenin accumulates in OTULIN-deficient keratinocytes, promoting its ubiquitination with K48 chains and subsequent proteasomal degradation. Reduced Wnt signalling in OTULIN-deficient keratinocytes leads to degradation of TCF3, an essential survival factor for keratinocytes ⁶ . Collectively, our data identify OTULIN’s linear deubiquitination activity as a key regulator of epithelial cell viability, not only by preventing cell death downstream of TNF, but also by promoting canonical Wnt signalling.

Autophagy is a cellular recycling program that serves as a crucial survival pathway and controls inflammatory responses in a context-dependent ma | POSTER

Cryopyrin-associated periodic syndromes (CAPS) are autoinflammatory disorders caused by gain-of-function NLRP3 variants. Although NLRP3 inflammasomes mediate IL-1β secretion through Gasdermin D (GSDMD), we show that GSDMD deletion did not prevent autoinflammation in mice ubiquitously expressing the Nlrp3 ^A350V variant. Inflamed skin of Nlrp3 ^A350V -expressing GSDMD-deficient mice displayed citrullinated histone 3-containing neutrophil extracellular traps (CitH3-NETs). CitH3-NETs induced IL-1β secretion from murine Nlrp3 ^A350V -expressing GSDMD-deficient macrophages as well as from human CAPS patient monocytes and macrophages. Blocking protein arginine deiminase-4 (PAD4) prevented CitH3 release and disabled the IL-1β-inducing NET effects, identifying CitH3 as crucial trigger. Mechanistically, CitH3-NETs activated GSDME in GSDMD-deficient Nlrp3 ^A350V macrophages, and GSDME deletion prevented pathology in Nlrp3 ^A350V -expressing GSDMD-deficient mice. In addition to this GSDME-dependent autoinflammation axis, PAD4 deletion also prevented autoinflammation in mice with neutrophil-specific Nlrp3 ^A350V expression that develop CAPS in a GSDMD-dependent manner. These observations support a CAPS model in which PAD4-mediated CitH3-NET release can trigger both GSDMD-dependent and GSDME-dependent autoinflammation.

Loss-of-function mutations in the human OTULIN gene, encoding a deubiquitinase with exclusive specificity for linear ubiquitin chains, cause a severe multiorgan autoinflammatory condition involving the skin. Mice lacking OTULIN selectively in keratinocytes develop inflamed skin lesions that progress into squamous tumors, a phenotype driven by excessive tumor necrosis factor (TNF)–induced cell death. Previous studies suggest a role for OTULIN in mediating Wnt signaling during development, but the physiological relevance of this association is unknown. Here, we show that OTULIN promotes Wnt signaling in keratinocytes by regulating the linear ubiquitination status of β-catenin. Stabilization of β-catenin in OTULIN-deficient keratinocytes prevents progressive skin inflammation in prophylactic and therapeutic settings by blocking keratinocyte death. We demonstrate that OTULIN prevents proteasomal degradation of β-catenin in cultured keratinocytes. Reduced Wnt signaling in OTULIN-deficient keratinocytes leads to degradation of TCF3/4, an essential survival factor for keratinocytes. Collectively, our data identify OTULIN’s linear deubiquitination activity as a key regulator of epithelial cell viability, not only by preventing cell death downstream of TNF, but also by promoting canonical Wnt signaling.