Katrin Schäfer

Tissue injury initiates a complex, multicellular programme whose outcome i.e. functional repair or irreversible fibrosis, is determined by the coordinated activity of the stroma-vascular compartment (SVC). This network of resident fibroblasts, vascular mural cells, endothelial cells and immune populations acts as a gatekeeper of tissue integrity. Following ischaemia, trauma, or mechanical damage, extracellular danger signals are sensed by pattern-recognition receptors and transduced into cell type-specific metabolic and mechanical responses. An initial inflammatory wave clears cellular debris, after which endothelial sprouting and matrix deposition proceed toward scar maturation; a collagen-rich structure whose geometry ultimately governs future perfusion. Epigenetic reprogramming and metabolic rewiring enforce each of these transitions while simultaneously imprinting a memory that skews subsequent responses in the context of ageing, diabetes, chronic inflammation or clonal haematopoiesis. Targeting the SVC, rather than the parenchyma alone, now underpins therapeutic strategies spanning precision senolytics, engineered stromal cell grafts, and biomechanically instructive scaffolds.

Endothelial dysfunction is a hallmark of pathological angiogenesis and associated with erythrocyte extravasation and lysis. Whether mediators released from lysed erythrocytes instruct endothelial cells (ECs) for new vessel formation is unknown. Here, we show that the membrane fraction of lysed erythrocytes activates inflammatory endothelial gene transcription and metabolically reprograms ECs to promote angiogenic sprout formation. Alterations in endothelial glucose metabolism occurred downstream of NFκB p65 activation by extracellular ATP via fast-acting endothelial P2X7 receptors and also involved ATP-mediated adenylyl cyclase activation and cyclic AMP generation via P2RY11. Overexpression and acetylation of histone 3 at lysine 27 of NR4A1 was identified as anti-inflammatory control mechanism and angio-metabolic switch activating VEGF , PFKFB3 and other AP-1 dependent gene transcription programs. The angiogenic potential of lysed erythrocyte membranes from patients with peripheral artery disease was impaired and could be restored by inhibiting endothelial phosphodiesterase 4 to prevent endothelial cAMP degradation. Our findings uncover that erythrolysis metabolically primes ECs for angiogenesis and that targeting endothelial cAMP generation may be a promising strategy to restore endothelial angiogenic functions.

Background: Up to one-third of all adults are affected by chronic venous insufficiency, with varicose veins being a common manifestation of the condition. It is believed that inflammation plays a central role in the progression of the disease; however, the immune cell populations and mechanisms involved remain unclear. Methods: Varicose veins were subjected to a stepwise mechanical and enzymatic dissociation, and the mononuclear cells resulting from these steps were characterized by flow cytometry. CD206-negative connective tissue macrophages and CD206-positive venous wall macrophages were sorted from five donors and subjected to transcriptomic profiling. Cytokine production by T cells in varicose veins was characterized following inhibition of intracellular protein transport. The ability of cytokines identified in macrophage transcriptomes to induce cytokine production in CD8 ⁺ and CD4 ⁺ effector and memory T cells was investigated using combinations of recombinant cytokines. Results: Varicose veins harbor CD206 ^neg IL-1α ⁺ S100A8/9 ⁺ macrophages in the connective tissue and pro-resolving and tissue regenerating CD206 ⁺ TIMD4 ⁺ LYVE1 ⁺ macrophages in the vein wall. T cells predominantly localize within the connective tissue, express an effector-memory T cell phenotype and produce IFN-γ in situ. Cytokines identified in the macrophage transcriptome collectively induced IFN-γ, as well as TNF-α, IL-22, and GM-CSF in effector memory T cells; in addition to IL-15 and IL-18, TNF-α and IL-10 proved to be key drivers. Conclusions: The identified macrophage-T cell cytokine axis contributes to chronic venous insufficiency pathogenesis and represents a potential therapeutic target. Abstract Figure:

BACKGROUND: Endothelial dysfunction is an early event in atherosclerosis development and is centrally linked with insufficient endothelial NO production. However, chronically increased NO levels, including NO from other cellular sources, may induce endothelial dysfunction. Here, we studied how chronically elevated NO production from erythrocytes, achieved by genetic deletion of ARG1 (arginase-1), impacts smooth muscle cell (SMC) lipid accumulation and atherosclerosis progression. METHODS: Primary aortic SMCs from mice lacking ARG1 in red blood cell (RBC.ARG1-knockout [KO]) were subjected to RNA-sequencing, lipidomic, metabolic, and molecular analyses; atherosclerosis burden was quantified en face and at the aortic root. RESULTS: Increased lipid droplet formation in SMCs from RBC.ARG1-KO mice was observed using brightfield and electron microscopy and confirmed by Oil Red O and boron-dipyrromethene lipid dye staining. RNA sequencing revealed the simultaneous overexpression of genes regulating lipid uptake ( Cd36 ), catabolism ( Cpt1a ), and de novo lipogenesis ( Acaca , Fasn [ Fatty acid synthase ]) in RBC.ARG1-KO SMCs, and inhibiting fatty acid translocase (CD36), ACC (acetyl-CoA [coenzyme A] carboxylase), or fatty acid synthase prevented the lipid accumulation in RBC.ARG1-KO SMCs. Increased expression of CD36 downstream of NO and overactivated sGC (soluble guanylyl cyclase)-cyclic guanosine monophosphate signaling was identified as a mediator of increased lipid uptake in RBC.ARG1-KO SMCs. Loss of PDE (phosphodiesterase) 2A, coupling cyclic guanosine monophosphate with cyclic adenosine monophosphate and PKA (protein kinase A) activation, was also observed, resulting in AMPK (5’ AMP-activated protein kinase) inhibition, thus unlocking acetyl-CoA carboxylase, catalyzing the rate-limiting step in fatty acid synthesis. Inhibiting PDE2A recapitulated the RBC.ARG1-KO SMC phenotype, while inhibiting PKA or ATP generation from cyclic adenosine monophosphate abrogated the lipid droplet accumulation in RBC.ARG1-KO SMCs. Increased Oil Red O-positive aortic atherosclerosis burden in hypercholesterolemic apolipoprotein E–deficient RBC.ARG1-KO mice was confirmed by histology and elevated levels of polyunsaturated long-chain cholesterol esters in aortic atheroma by mass spectrometry lipidomics. CONCLUSIONS: Our findings show the importance of erythrocyte-derived NO for metabolically reprogramming SMCs toward increased fatty acid uptake and lipogenesis, and identify PDE2A as a molecular switch linking chronically activated NO signaling with lipid accumulation and atheroma progression.

Glucagon-like peptide-1 (GLP-1) and glucose-induced insulinotropic polypeptide (GIP) receptor agonists have revolutionized obesity therapy, but causes of obesity-associated dysregulation of endogenous incretin production remain incompletely understood. Here we show that intestinal transmembrane serine protease 2 (TMPRSS2) plays a pivotal role in deregulating anti-diabetic GLP-1 production in obesity. TMPRSS2 is widely coexpressed in intestinal epithelial cells along with its signaling target protease-activated receptor 2 (PAR2). In addition to its role in regulating coagulation protease–mediated adipose tissue inflammation, PAR2 signaling in the gut controls postprandial GIP secretion. TMPRSS2, but not the epithelial cell–expressed proteases FXa or matriptase, activates PAR2 and thereby promotes postprandial GIP release. Accordingly, a PAR2-mutant mouse resistant to TMPRSS2 cleavage is protected from GIP upregulation and diet-induced obesity. In the context of obesity, TMPRSS2 also attenuates bioavailability of the ghrelin pathway and thereby suppresses GLP-1–mediated control of glucose homeostasis. Pharmacological inhibition or genetic deletion of TMPRSS2 restores ghrelin signaling–dependent GLP-1 secretion and GLP-1’s anti-diabetic effects on nutritional glucose homeostasis. Thus, epithelial cell–expressed TMPRSS2, which critically contributes to the lung pathology in SARS-CoV-2 infection, emerges as an intestinal incretin regulator and a potential link between infection and chronic cardiometabolic diseases. GLP-1 based therapeutics revolutionized anti-diabetic and anti-obesity treatments. The current study identifies epithelial TMPRSS2 as a critical regulator of GLP-1 in obesity induced diabetes.

Aims: Angiotensin II (AngII) causes hypertension and vascular inflammation and is essential in neurohumoral activation promoting the development of heart failure. The role of the adaptor protein myeloid factor of differentiation 88 (MyD88) driving this pathology remains incompletely understood. Methods and results: Male C57BL/6JMyD88−/−, LysMCre/wtMyD88LSL/LSL, LysMCre/wt, TLR2−/−, TLR4−/−, TLR7−/−, and TLR9−/− mice were investigated (1 mg/AngIIkg/d for 7 days). Additionally, we performed biodata analyses from a population-based cohort study and human protein network interactome analyses to understand the role of MyD88 in hypertension. MyD88 deficiency attenuated AngII-induced hypertension and endothelial dysfunction in conductance and resistance vessels, surpassing the effect of single TLR deficiencies. Vascular mRNA expression levels of vcam-1, nos2, nox2, cd62L, cd68, ccl2, il12, and il1b and accumulation of CD11b+Ly6Chi inflammatory monocytes and interferon-g+ NK cells were significantly dampened in MyD88−/−. Vascular protection was conferred by MyD88 deficiency in bone marrow–derived cells. Re-expression of MyD88 in LysMCre/wtMyD88LSL/LSL mice restored AngII-induced pathology, revealing that myeloid cells drive vascular dysfunction in a MyD88-dependent manner. Computational analyses of the human protein interactome demonstrated that MyD88 expression significantly associates with proteins encoded by genetic loci associated with blood pressure traits in multiple GWAS. In hypertensive individuals of the Gutenberg Health Study, monocytic MyD88 mRNA expression was associated with prevalent heart failure and all-cause mortality after a median follow-up of 16.5 years. Conclusion: MyD88 promotes AngII-induced vascular dysfunction and arterial hypertension and might serve as both an inflammatory diagnostic marker and a drug target to tackle the risk of death and incident heart failure in hypertensive patients.

Endothelial cells within chronic pulmonary artery thrombi in CTEPH overexpress transmembrane protein 100 (TMEM100), an activin A receptor‐like kinase 1 (ACVRL1 or ALK1) signaling‐dependent gene, and TGFβ1 upregulated TMEM100 transcription in healthy lung ECs. TMEM100 permitted the TGFβ1‐induced increase of ALK1, while repressing ALK5, and preventing ALK1–TMEM100 signaling impaired angiogenesis ex vivo. Our data indicate that TGFβ1–ALK1–TMEM100 signaling is active during CTEPH thrombus revascularization.