Selection for transcatheter versus surgical aortic valve replacement and mid-term survival: results of the AUTHEARTVISIT study.

OBJECTIVES: Limited data are available from randomized trials comparing outcomes between transcatheter aortic valve replacement (TAVR) and surgery in patients with different risks and with follow-up of at least 4 years or longer. In this large, population-based cohort study, long-term mortality and morbidity were investigated in patients undergoing aortic valve replacement (AVR) for severe aortic stenosis using a surgically implanted bioprosthesis (sB-AVR) or TAVR. METHODS: Individual data from the Austrian Insurance Funds from 2010 through 2020 were analysed. The primary outcome was all-cause mortality, assessed in the overall and propensity score-matched populations. Secondary outcomes included reoperation and cardiovascular events. RESULTS: From January 2010 through December 2020, a total of 18 882 patients underwent sB-AVR (n = 11 749; 62.2%) or TAVR (n = 7133; 37.8%); median follow-up was 5.8 (95% CI 5.7-5.9) years (maximum 12.3 years). The risk of all-cause mortality was higher with TAVR compared with sB-AVR: hazard ratio (HR) 1.552, 95% confidence interval (CI) 1.469-1.640, p < 0.001; propensity score-matched HR 1.510, 1.403-1.625, p < 0.001. Estimated median survival was 8.8 years (95% CI 8.6-9.1) with sB-AVR versus 5 years (4.9-5.2) with TAVR. Estimated 5-year survival probability was 0.664 (0.664-0.686) with sB-AVR versus 0.409 (0.378-0.444) with TAVR overall, and 0.690 (0.674-0.707) and 0.560 (0.540-0.582), respectively, with propensity score matching. Separate subgroup analyses for patients aged 65-75 years and >75 years indicated a significant survival benefit in patients selected for sB-AVR in both groups. Other predictors of mortality were age, sex, previous heart failure, diabetes, and chronic kidney disease. CONCLUSIONS: In this retrospective national population-based study, selection for TAVR was significantly associated with higher all-cause mortality compared with sB-AVR in patients ≥65 years with severe, symptomatic aortic stenosis in the >2-year follow-up.

Revisiting aortic valve prosthesis choice in patients younger than 50 years: 10 years results of the AUTHEARTVISIT study.

OBJECTIVES: This population-based cohort study investigated mid-term outcome after surgical aortic valve replacement with a bioprosthetic or mechanical valve prosthesis in patients aged <50 years in a European social welfare state. METHODS: We analysed patient data from the main social insurance carriers in Austria (2010-2020). Subsequent patient-level record linkage with national health data provided patient characteristics and clinical outcome. Survival, reoperation, myocardial infarction, heart failure, embolic stroke or intracerebral haemorrhage, bleeding other than intracerebral haemorrhage and major adverse cardiac events were evaluated as outcomes. RESULTS: A total of 991 patients were analysed. Regarding demographics, no major differences between groups were observed. Multivariable Cox regression revealed no significant difference in overall survival (P = 0.352) with a median follow-up time of 6.2 years. Reoperation-free survival was decreased (hazard ratio = 1.560 [95% CI: 1.076-2.262], P = 0.019) and the risk for reoperation was increased (hazard ratio = 2.770 [95% CI: 1.402-5.472], P = 0.003) in patients who received bioprostheses. Estimated probability of death after reoperation was 0.23 (CL: 0.08-0.35) after 2 years and 0.34 (CL: 0.06-0.53) after 10 years over both groups. Regarding further outcomes, no significant differences between the two groups were observed. CONCLUSIONS: In patients below 50 years of age receiving aortic valve replacement, implantation of bioprostheses when compared to mechanical heart valve prostheses was associated with a significantly higher rate of reoperations and reduced reoperation-free survival. Nevertheless, we could not observe a difference in overall survival. However, long-term follow-up has to evaluate that a significantly lower rate of reoperations may translate in consistently improved long-term survival.

Exploring the heterogeneous transcriptional response of the CNS to systemic LPS and Poly(I:C).

Peripheral contact to pathogen-associated molecular patterns (PAMPs) evokes a systemic innate immune response which is rapidly relayed to the central nervous system (CNS). The remarkable cellular heterogeneity of the CNS poses a significant challenge to the study of cell type and stimulus dependent responses of neural cells during acute inflammation. Here we utilized single nuclei RNA sequencing (snRNAseq), serum proteome profiling and primary cell culture methods to systematically compare the acute response of the mammalian brain to the bacterial PAMP lipopolysaccharide (LPS) and the viral PAMP polyinosinic:polycytidylic acid (Poly(I:C)), at single cell resolution. Our study unveiled convergent transcriptional cytokine and cellular stress responses in brain vascular and ependymal cells and a downregulation of several key mediators of directed blood brain barrier (BBB) transport. In contrast the neuronal response to PAMPs was limited in acute neuroinflammation. Moreover, our study highlighted the dominant role of IFN signalling upon Poly(I:C) challenge, particularly in cells of the oligodendrocyte lineage. Collectively our study unveils heterogeneous, shared and distinct cell type and stimulus dependent acute responses of the CNS to bacterial and viral PAMP challenges. Our findings highlight inflammation induced dysregulations of BBB-transporter gene expression, suggesting potential translational implications on drug pharmacokinetics variability during acute neuroinflammation. The pronounced dependency of oligodendrocytes on IFN stimulation during viral PAMP challenges, emphasizes their limited molecular viral response repertoire.

Elevation of neutrophil-derived factors in patients after multiple trauma.

Trauma represents one of the leading causes of death worldwide. Traumatic injuries elicit a dynamic inflammatory response with systemic release of inflammatory cytokines. Disbalance of this response can lead to systemic inflammatory response syndrome or compensatory anti-inflammatory response syndrome. As neutrophils play a major role in innate immune defence and are crucial in the injury-induced immunological response, we aimed to investigate systemic neutrophil-derived immunomodulators in trauma patients. Therefore, serum levels of neutrophil elastase (NE), myeloperoxidase (MPO) and citrullinated histone H3 (CitH3) were quantified in patients with injury severity scores above 15. Additionally, leukocyte, platelet, fibrinogen and CRP levels were assessed. Lastly, we analysed the association of neutrophil-derived factors with clinical severity scoring systems. Although the release of MPO, NE and CitH3 was not predictive of mortality, we found a remarkable increase in MPO and NE in trauma patients as compared with healthy controls. We also found significantly increased levels of MPO and NE on Days 1 and 5 after initial trauma in critically injured patients. Taken together, our data suggest a role for neutrophil activation in trauma. Targeting exacerbated neutrophil activation might represent a new therapeutic option for critically injured patients.

FAM3C/ILEI protein is elevated in psoriatic lesions and triggers psoriasiform hyperproliferation in mice.

FAM3C/ILEI is an important cytokine for tumor progression and metastasis. However, its involvement in inflammation remains elusive. Here, we show that ILEI protein is highly expressed in psoriatic lesions. Inducible keratinocyte-specific ILEI overexpression in mice (K5-ILEIind ) recapitulates many aspects of psoriasis following TPA challenge, primarily manifested by impaired epidermal differentiation and increased neutrophil recruitment. Mechanistically, ILEI triggers Erk and Akt signaling, which then activates STAT3 via Ser727 phosphorylation. Keratinocyte-specific ILEI deletion ameliorates TPA-induced skin inflammation. A transcriptomic ILEI signature obtained from the K5-ILEIind model shows enrichment in several signaling pathways also found in psoriasis and identifies urokinase as a targetable enzyme to counteract ILEI activity. Pharmacological inhibition of urokinase in TPA-induced K5-ILEIind mice results in significant improvement of psoriasiform symptoms by reducing ILEI secretion. The ILEI signature distinguishes psoriasis from healthy skin with uPA ranking among the top "separator" genes. Our study identifies ILEI as a key driver in psoriasis, indicates the relevance of ILEI-regulated genes for disease manifestation, and shows the clinical impact of ILEI and urokinase as novel potential therapeutic targets in psoriasis.

Therapeutic Application of Cell Secretomes in Cutaneous Wound Healing.

Although the application of stem cells to chronic wounds emerged as a candidate therapy in the previous century, the mechanism of action remains unclear. Recent evidence has implicated secreted paracrine factors in the regenerative properties of cell-based therapies. In the last two decades, considerable research advances involving the therapeutic potential of stem cell secretomes have expanded the scope of secretome-based therapies beyond stem cell populations. In this study, we review the modes of action of cell secretomes in wound healing, important preconditioning strategies for enhancing their therapeutic efficacy, and clinical trials on secretome-based wound healing.

The Secretome of Irradiated Peripheral Mononuclear Cells Attenuates Hypertrophic Skin Scarring.

Hypertrophic scars can cause pain, movement restrictions, and reduction in the quality of life. Despite numerous options to treat hypertrophic scarring, efficient therapies are still scarce, and cellular mechanisms are not well understood. Factors secreted by peripheral blood mononuclear cells (PBMCsec) have been previously described for their beneficial effects on tissue regeneration. In this study, we investigated the effects of PBMCsec on skin scarring in mouse models and human scar explant cultures at single-cell resolution (scRNAseq). Mouse wounds and scars, and human mature scars were treated with PBMCsec intradermally and topically. The topical and intradermal application of PBMCsec regulated the expression of various genes involved in pro-fibrotic processes and tissue remodeling. We identified elastin as a common linchpin of anti-fibrotic action in both mouse and human scars. In vitro, we found that PBMCsec prevents TGFß-mediated myofibroblast differentiation and attenuates abundant elastin expression with non-canonical signaling inhibition. Furthermore, the TGFß-induced breakdown of elastic fibers was strongly inhibited by the addition of PBMCsec. In conclusion, we conducted an extensive study with multiple experimental approaches and ample scRNAseq data demonstrating the anti-fibrotic effect of PBMCsec on cutaneous scars in mouse and human experimental settings. These findings point at PBMCsec as a novel therapeutic option to treat skin scarring.

The p-rpS6-zone delineates wounding responses and the healing process.

The spatial boundaries of tissue response to wounding are unknown. Here, we show that in mammals, the ribosomal protein S6 (rpS6) is phosphorylated in response to skin injury, forming a zone of activation surrounding the region of the initial insult. This p-rpS6-zone forms within minutes after wounding and is present until healing is complete. The zone is a robust marker of healing as it encapsulates features of the healing process, including proliferation, growth, cellular senescence, and angiogenesis. A mouse model that is unable to phosphorylate rpS6 shows an initial acceleration of wound closure, but results in impaired healing, identifying p-rpS6 as a modulator but not a driver of healing. Finally, the p-rpS6-zone accurately reports on the status of dermal vasculature and the effectiveness of healing, visually dividing an otherwise homogeneous tissue into regions with distinct properties.

Lipids of Platelet-Rich Fibrin Reduce the Inflammatory Response in Mesenchymal Cells and Macrophages.

Platelet-rich fibrin (PRF) has a potent anti-inflammatory activity but the components mediating this effect remain unknown. Blood lipids have anti-inflammatory properties. The question arises whether this is also true for the lipid fraction of PRF. To answer this question, lipid fractions of solid and liquid PRF were tested for their potential to lower the inflammatory response of ST2 bone marrow stromal cells and primary bone marrow macrophages exposed to IL1ß and TNFα, and LPS, respectively. Cytokine production and the underlying signalling pathway were analysed by RT-PCR, immunoassays, and Western blotting. We report here that lipids from solid and liquid PRF substantially lowered cytokine-induced expression of IL6, CCL2 and CCL5 in ST2 cells. Moreover, the inflammatory response induced by Pam3CSK4, the agonist of Toll-like receptor (TLR) TLR2, was partially reduced by the lipid extracts in ST2 cells. The PRF lipids further reduced the LPS-induced expression of IL1ß, IL6 and CCL5 in macrophages at the transcriptional level. This was confirmed by showing the ability of PRF lipids to diminish IL6 at the protein level in ST2 cells and macrophages. Likewise, PRF lipid extracts reduced the phosphorylation of p38 and JNK and moderately decreased the phosphorylation of NFκB-p65 in ST2 cells. These findings suggest that the lipid fraction is at least partially responsible for the anti-inflammatory activity of PRF in vitro.

Antithymocyte Globulin Inhibits CD8+ T Cell Effector Functions via the Paracrine Induction of PDL-1 on Monocytes.

BACKGROUND: Antithymocyte globulins (ATG) are T cell-depleting antibodies used in solid organ transplantation for induction therapy in sensitized patients with a high risk of graft rejection. Previously described effects besides the depletion of T cells have suggested additional modes of action and identified further cellular targets. METHODS: We examined the transcriptional changes arising in immune cells from human blood after ex vivo stimulation with ATG at the single-cell level to uncover additional mechanisms by which ATG regulates T cell activity and effector functions. FINDINGS: Analysis of the paracrine factors present in the plasma of ATG-treated whole blood revealed high levels of chemokines and cytokines, including interferon-γ (IFN-γ). Furthermore, we identified an increase in the surface expression of the programmed death ligand 1 (PDL-1) on monocytes mediated by the released paracrine factors. In addition, we showed that this induction is dependent on the activation of JAK/STAT signaling via the binding of IFN-γ to interferon-γ receptor 1 (IFN-γR1). Lastly, we demonstrated that the modulation of the immune regulatory axis of programmed cell death protein 1 (PD1) on activated CD8+ T cells with PDL-1 found on monocytes mediated by ATG potently inhibits effector functions including the proliferation and granzyme B release of activated T cells. INTERPRETATION: Together, our findings represent a novel mode of action by which ATG exerts its immunosuppressive effects.

ORF1p Is a Potential Novel Diagnostic Marker for Differentiated Vulvar Intraepithelial Neoplasia.

Accurate diagnosis of differentiated vulvar intraepithelial neoplasia (dVIN) can be challenging as histomorphologic features may be subtle and overlap with nondysplastic lesions. In practice, aberrant p53 expression supports the diagnosis, but a substantial percentage retains wild-type p53. Recently, the retrotransposon long interspersed nuclear element 1 has been detected in distinct cancer types. We have now investigated the expression of the long interspersed nuclear element 1 encoded protein ORF1p in dysplastic and nondysplastic vulvar samples to assess its diagnostic value. Specimens of dVIN (n=29), high-grade squamous intraepithelial lesions (n=26), inflammatory vulvar lesions (n=20), lichen sclerosus (n=22), and normal vulvar epithelia (n=29) were included. ORF1p and p53 expression was determined using immunohistochemistry. The majority of dVIN [27/29 (93%)] and high-grade squamous intraepithelial lesions [20/26 (77%)] showed distinct (i.e. moderate or strong) ORF1p expression in the basal and suprabasal or all epithelial layers, respectively. Of note, ORF1p was present in all 4 cases of dVIN with wild-type p53 staining pattern. In contrast, ORF1p was negative or weakly expressed in most inflammatory lesions [14/20 (70%)] and lichen sclerosus [18/22 (82%), P <0.001]. Normal control epithelium exhibited negative staining in all cases. In conclusion, ORF1p might be a useful diagnostic marker for dVIN, especially in cases with retained wild-type p53.

Single nucleus RNA sequencing reveals glial cell type-specific responses to ischemic stroke.

Reactive neuroglia critically shape the brains response to ischemic stroke. However, their phenotypic heterogeneity impedes a holistic understanding of the cellular composition and microenvironment of the early ischemic lesion. Here we generated a single cell resolution transcriptomics dataset of the injured brain during the acute recovery from permanent middle cerebral artery occlusion. This approach unveiled infarction and subtype specific molecular signatures in oligodendrocyte lineage cells and astrocytes, which ranged among the most transcriptionally perturbed cell types in our dataset. Specifically, we characterized and compared infarction restricted proliferating oligodendrocyte precursor cells (OPCs), mature oligodendrocytes and heterogeneous reactive astrocyte populations. Our analyses unveiled unexpected commonalities in the transcriptional response of oligodendrocyte lineage cells and astrocytes to ischemic injury. Moreover, OPCs and reactive astrocytes were involved in a shared immuno-glial cross talk with stroke specific myeloid cells. In situ, osteopontin positive myeloid cells accumulated in close proximity to proliferating OPCs and reactive astrocytes, which expressed the osteopontin receptor CD44, within the perilesional zone specifically. In vitro, osteopontin increased the migratory capacity of OPCs. Collectively, our study highlights molecular cross talk events which might govern the cellular composition and microenvironment of infarcted brain tissue in the early stages of recovery.

The transcriptional profile of keloidal Schwann cells.

Recently, a specific Schwann cell type with profibrotic and tissue regenerative properties that contributes to keloid formation has been identified. In the present study, we reanalyzed published single-cell RNA sequencing (scRNA-seq) studies of keloids, healthy skin, and normal scars to reliably determine the specific gene expression profile of keloid-specific Schwann cell types in more detail. We were able to confirm the presence of the repair-like, profibrotic Schwann cell type in the datasets of all three studies and identified a specific gene-set for these Schwann cells. In contrast to keloids, in normal scars, the number of Schwann cells was not increased, nor was their gene expression profile distinctly different from that of Schwann cells of normal skin. In addition, our bioinformatics analysis provided evidence for a role of transcription factors of the AP1, STAT, and KLF families, and members of the IER genes in the dedifferentiation process of keloidal Schwann cells. Together, our analysis strengthens the role of the profibrotic Schwann cell type in the formation of keloids. Knowledge of the exact gene expression profile of these Schwann cells will facilitate their identification in other organs and diseases.

Paracrine Factors of Stressed Peripheral Blood Mononuclear Cells Activate Proangiogenic and Anti-Proteolytic Processes in Whole Blood Cells and Protect the Endothelial Barrier.

Tissue-regenerative properties have been attributed to secreted paracrine factors derived from stem cells and other cell types. In particular, the secretome of γ-irradiated peripheral blood mononuclear cells (PBMCsec) has been shown to possess high tissue-regenerative and proangiogenic capacities in a variety of preclinical studies. In light of future therapeutic intravenous applications of PBMCsec, we investigated the possible effects of PBMCsec on white blood cells and endothelial cells lining the vasculature. To identify changes in the transcriptional profile, whole blood was drawn from healthy individuals and stimulated with PBMCsec for 8 h ex vivo before further processing for single-cell RNA sequencing. PBMCsec significantly altered the gene signature of granulocytes (17 genes), T-cells (45 genes), B-cells (72 genes), and, most prominently, monocytes (322 genes). We detected a strong upregulation of several tissue-regenerative and proangiogenic cyto- and chemokines in monocytes, including VEGFA, CXCL1, and CXCL5. Intriguingly, inhibitors of endopeptidase activity, such as SERPINB2, were also strongly induced. Measurement of the trans-endothelial electrical resistance of primary human microvascular endothelial cells revealed a strong barrier-protective effect of PBMCsec after barrier disruption. Together, we show that PBMCsec induces angiogenic and proteolytic processes in the blood and is able to attenuate endothelial barrier damage. These regenerative properties suggest that systemic application of PBMCsec might be a promising novel strategy to restore damaged organs.

The Effect of Paracrine Factors Released by Irradiated Peripheral Blood Mononuclear Cells on Neutrophil Extracellular Trap Formation.

Neutrophil extracellular trap (NET)-formation represents an important defence mechanism for the rapid clearance of infections. However, exaggerated NET formation has been shown to negatively affect tissue-regeneration after injury. As our previous studies revealed the strong tissue-protective and regenerative properties of the secretome of stressed peripheral blood mononuclear cells (PBMCsec), we here investigated the influence of PBMCsec on the formation of NETs. The effect of PBMCsec on NET formation was assessed ex vivo in ionomycin stimulated neutrophils derived from healthy donors using flow cytometry, image stream analysis, and quantification of released extracellular DNA. The effect of PBMCsec on molecular mechanisms involved in NET formation, including Ca-flux, protein kinase C activity, reactive oxygen species production, and protein arginine deiminase 4 activity, were analysed. Our results showed that PBMCsec significantly inhibited NET formation. Investigation of the different biological substance classes found in PBMCsec revealed only a partial reduction in NET formation, suggesting a synergistic effect. Mechanistically, PBMCsec treatment did not interfere with calcium signalling and PKC-activation, but exerted anti-oxidant activity, as evidenced by reduced levels of reactive oxygen species and upregulation of heme oxygenase 1 and hypoxia inducible-factor 1 in PBMCsec-treated neutrophils. In addition, PBMCsec strongly inhibited the activation of protein arginine deiminase 4 (PAD4), ultimately leading to the inhibition of NET formation. As therapeutics antagonizing excessive NET formation are not currently available, our study provides a promising novel treatment option for a variety of conditions resulting from exaggerated NET formation.

The secretome of irradiated peripheral blood mononuclear cells attenuates activation of mast cells and basophils.

BACKGROUND: IgE-mediated hypersensitivity is becoming increasingly prevalent and activation of mast cells and basophils represent key events in the pathophysiology of allergy. We have previously reported that the secretome of γ-irradiated peripheral blood mononuclear cells (PBMCsec) exerts beneficial anti-inflammatory effects. Yet, its ability to alleviate allergic symptoms has not been investigated so far. METHODS: Several experimental in vitro and in vivo models have been used in this basic research study. A murine ear swelling model was used to study the effects of PBMCsec on 48/80-induced mast cell degranulation in vivo. The transcriptional profile of murine mast cells was analysed by single cell RNA sequencing (scRNAseq). Mast cell activation was studied in vitro using primary skin mast cells. Basophils from individuals allergic to birch pollens were used to investigate basophile activation by allergens. Transcriptomic and lipidomic analyses were used to identify mRNA expression and lipid species present in PBMCsec, respectively. FINDINGS: Topical application of PBMCsec on mouse ears (C57BL/6) significantly reduced tissue swelling following intradermal injection of compound 48/80, an inducer of mast cell degranulation. Single cell RNA sequencing of PBMCsec-treated murine dermal mast cells (Balb/c) revealed a downregulation of genes involved in immune cell degranulation and Fc-receptor signalling. In addition, treatment of primary human dermal mast cells with PBMCsec strongly inhibited compound 48/80- and α-IgE-induced mediator release in vitro. Furthermore, PBMCsec remarkably attenuated allergen driven activation of basophils from allergic individuals. Transcriptomic analysis of these basophils showed that PBMCsec downregulated a distinct gene battery involved in immune cell degranulation and Fc-receptor signalling, corroborating results obtained from dermal mast cells. Finally, we identified the lipid fraction of PBMCsec as the major active ingredient involved in effector cell inhibition. INTERPRETATION: Collectively, our data demonstrate that PBMCsec is able to reduce activation of mast cells and basophils, encouraging further studies on the potential use of PBMCsec for treating allergy. FUNDING: Austrian Research Promotion Agency (852748 and 862068, 2015-2019), Vienna Business Agency (2343727, 2018-2020), Aposcience AG, Austrian Federal Ministry of Education, Science and Research (SPA06/055), Danube Allergy Research Cluster, Austrian Science Fund (I4437 and P32953).

EGR1 Is Implicated in Right Ventricular Cardiac Remodeling Associated with Pulmonary Hypertension.

BACKGROUND: Pulmonary hypertension (PH) is a vasoconstrictive disease characterized by elevated mean pulmonary arterial pressure (mPAP) at rest. Idiopathic pulmonary arterial hypertension (iPAH) and chronic thromboembolic pulmonary hypertension (CTEPH) represent two distinct subtypes of PH. Persisting PH leads to right ventricular (RV) hypertrophy, heart failure, and death. RV performance predicts survival and surgical interventions re-establishing physiological mPAP reverse cardiac remodeling. Nonetheless, a considerable number of PH patients are deemed inoperable. The underlying mechanism(s) governing cardiac regeneration, however, remain largely elusive. METHODS: In a longitudinal approach, we profiled the transcriptional landscapes of hypertrophic RVs and recovered hearts 3 months after surgery of iPAH and CTEPH patients. RESULTS: Genes associated with cellular responses to inflammatory stimuli and metal ions were downregulated, and cardiac muscle tissue development was induced in iPAH after recovery. In CTEPH patients, genes related to muscle cell development were decreased, and genes governing cardiac conduction were upregulated in RVs following regeneration. Intriguingly, early growth response 1 (EGR1), a profibrotic regulator, was identified as a major transcription factor of hypertrophic RVs in iPAH and CTEPH. A histological assessment confirmed our biocomputational results, and suggested a pivotal role for EGR1 in RV vasculopathy. CONCLUSION: Our findings improved our understanding of the molecular events driving reverse cardiac remodeling following surgery. EGR1 might represent a promising candidate for targeted therapy of PH patients not eligible for surgical treatment.

Schwann cells contribute to keloid formation.

Keloids are disfiguring, hypertrophic scars with yet poorly understood pathomechanisms, which could lead to severe functional impairments. Here we analyzed the characteristics of keloidal cells by single cell sequencing and discovered the presence of an abundant population of Schwann cells that persisted in the hypertrophic scar tissue after wound healing. In contrast to normal skin, keloidal Schwann cells show a unique, pro-fibrotic phenotype. Our data support the hypothesis that keloidal Schwann cells contribute to the formation of the extracellular matrix and are able to affect M2 polarization of macrophages. Indeed, we show that macrophages in keloids predominantly display a M2 polarization and produce factors that inhibit Schwann cell differentiation. This study suggests the contribution of a Schwann cell - macrophage cross-talk to the continuous expansion of keloids, and that targeting Schwann cells might represent an interesting novel treatment option for keloids.

Severity of thermal burn injury is associated with systemic neutrophil activation.

Burn injuries elicit a unique and dynamic stress response which can lead to burn injury progression. Though neutrophils represent crucial players in the burn-induced immunological events, the dynamic secretion pattern and systemic levels of neutrophil-derived factors have not been investigated in detail so far. Serum levels of neutrophil elastase (NE), myeloperoxidase (MPO), citrullinated histone H3 (CitH3), and complement factor C3a were quantified in burn victims over 4 weeks post injury. Furthermore, the potential association with mortality, degree of burn injury, and inhalation trauma was evaluated. In addition, leukocyte, platelet, neutrophil, and lymphocyte counts were assessed. Lastly, we analyzed the association of neutrophil-derived factors with clinical severity scoring systems. Serum levels of NE, MPO, CitH3, and C3a were remarkably elevated in burn victims compared to healthy controls. Leukocyte and neutrophil counts were significantly increased on admission day and day 1, while relative lymphocytes were decreased in the first 7 days post burn trauma. Though neutrophil-derived factors did not predict mortality, patients suffering from 3rd degree burn injuries displayed increased CitH3 and NE levels. Accordingly, CitH3 and NE were elevated in cases with higher abbreviated burn severity indices (ABSI). Taken together, our data suggest a role for neutrophil activation and NETosis in burn injuries and burn injury progression. Targeting exacerbated neutrophil activation might represent a new therapeutic option for severe cases of burn injury.