[Skin fibrosis : Novel insights in pathophysiology and treatment]. / Fibrose der Haut : Neue Erkenntnisse in Pathophysiologie und Therapie.

The pathogenesis of fibrosing alterations in the skin and other organ systems is not yet sufficiently understood and current therapeutic options are limited. Fibrosing diseases of the skin lead to a loss of function, which can subsequently be accompanied by serious impairments in quality of life, increased morbidity and ultimately increased mortality. There are currently only a few pharmacological and therapeutic approaches approved to prevent or ameliorate fibrosing diseases. Furthermore, tissue-specific versus common, non-organ-specific pathophysiological cellular and molecular mechanisms are not resolved. The development of new, cause-based and therefore likely more efficient therapeutic approaches is urgently needed. This represents a major challenge, but also opens up the opportunity for special contributions to improve this medically unsolved problem. Here we present important findings from recent years with a focus on the role of the immune response in fibrogenesis.

Isolation of dermal adipocytes from mouse skin for biochemical analysis.

The role of dermal white adipose tissue in regulating skin homeostasis and self-renewal processes has recently attracted interest. However, the isolation of proteins from dermal adipocytes for biochemical analysis is challenging. Here, we provide a protocol for the isolation of murine dermal adipocytes. We describe steps for inducing adipocyte-specific gene deletion, adipocyte isolation, protein purification, and western blot analysis. The reliability of the protocol is demonstrated by verifying efficient adipocyte-specific Atgl gene deletion in a tamoxifen-inducible Cre/loxP-based mouse model. For complete details on the use and execution of this protocol, please refer to Zhang et al. (2019).1.

Type 2 Immunity Regulates Dermal White Adipose Tissue Function.

Type 2 immune responses have been increasingly linked with tissue maintenance, regeneration, and metabolic homeostasis. The molecular basis of regulator and effector mechanisms of type 2 immunity in skin regeneration and homeostasis is still lacking. In this study, we analyzed the role of IL-4Rα signaling in the regeneration of diverse cellular compartments in the skin. Mutants with global IL-4Rα deficiency showed two major phenotypes: first, a pronounced atrophy of the interfollicular epidermis, and second, a significant increase in dermal white adipose tissue thickness in mice aged 3 weeks (postnatal day 21) compared with littermate controls. Notably, IL-4Rα deficiency decreased the activation of hormone-sensitive lipase, a rate-limiting step in lipolysis. Immunohistochemical and FACS analysis in IL-4/enhanced GFP reporter mice showed that IL-4 expression peaked on postnatal day 21 and that eosinophils are the predominant IL-4-expressing cells. Eosinophil-deficient mice recapitulated the lipolytic-defective dermal white adipose tissue phenotype of Il4ra-deficient mice, showing that eosinophils are necessary for dermal white adipose tissue lipolysis. Collectively, we provide mechanistic insights into the regulation of interfollicular epidermis and hormone-sensitive lipase-mediated lipolysis in dermal white adipose tissue in early life by IL-4Rα, and our findings show that eosinophils play a critical role in this process.

Gene-selective transcription promotes the inhibition of tissue reparative macrophages by TNF.

Anti-TNF therapies are a core anti-inflammatory approach for chronic diseases such as rheumatoid arthritis and Crohn's Disease. Previously, we and others found that TNF blocks the emergence and function of alternative-activated or M2 macrophages involved in wound healing and tissue-reparative functions. Conceivably, anti-TNF drugs could mediate their protective effects in part by an altered balance of macrophage activity. To understand the mechanistic basis of how TNF regulates tissue-reparative macrophages, we used RNAseq, scRNAseq, ATACseq, time-resolved phospho-proteomics, gene-specific approaches, metabolic analysis, and signaling pathway deconvolution. We found that TNF controls tissue-reparative macrophage gene expression in a highly gene-specific way, dependent on JNK signaling via the type 1 TNF receptor on specific populations of alternative-activated macrophages. We further determined that JNK signaling has a profound and broad effect on activated macrophage gene expression. Our findings suggest that TNF's anti-M2 effects evolved to specifically modulate components of tissue and reparative M2 macrophages and TNF is therefore a context-specific modulator of M2 macrophages rather than a pan-M2 inhibitor.

Cinnamon reduces inflammatory response in intestinal fibroblasts in vitro and in colitis in vivo leading to decreased fibrosis.

SCOPE: Intestinal fibrosis, a complication of inflammatory bowel disease, is currently being addressed by surgery alone, with no adequate alternative therapy available for patients. We propose that anti-inflammatory plant substances like cinnamon extract (CE) or its main compound cinnamaldeyde (CA) could aid in therapy. We recently found CE reducing inflammation in murine colitis. Here, we analyzed effects of CE on fibrosis in IL-10-/- colitis. METHODS AND RESULTS: IL-10-/- and wild-type (WT) mice were orally treated with/without vehicle or CE. Colonic tissue was analyzed for collagen deposition and expression of matrix metalloproteinases (MMPs). Influence of CE or CA on expression and release of cytokines, and phosphorylation of IκB in LPS-activated fibroblasts was assessed. Fibrosis score and mRNA expression of MMPs were down-regulated in colonic tissue of CE-treated IL-10-/- mice. Fibroblasts treated with CE or CA showed reduced expression and release of IL-6, KC/C-X-C motif ligand (CXCL) 8, and C-C motif ligand (CCL) 2 in response to LPS-treatment. CE and CA appear to act via reducing phosphorylation of IκB. CONCLUSIONS: Cinnamon decreases fibrotic symptoms and markers in murine colitis, and expression of inflammatory and fibrotic markers in hiFB. Thus, CE and CA could be potential anti-fibrotic agents in chronic colitis.