Collagen Scar Formation Research Articles

Implantable conductive polymer bioelectrode with enzymatic antioxidant activity for enhanced tissue responses and in vivo performance

Implantable bioelectrodes enable precise diagnosis and treatment through direct transmission of electrical signals in the living tissues. However, a fundamental challenge arises as implanted bioelectrodes frequently lose performance due to adverse tissue reactions, primarily induced by high oxidative stress and subsequent inflammatory activation of macrophages. In this study, we investigated a novel strategy to address this challenge in implantable bioelectrodes by introducing reactive oxygen species (ROS)-scavenging capabilities to the bioelectrodes. Specifically, a polypyrrole (PPy) electrode doped with hemin-conjugated heparin (HepH) was fabricated to impart robust enzyme-like antioxidant properties. The HepH-doped PPy electrodes exhibited a catalase-mimicking activity, as evidenced by hydrogen peroxide scavenging and oxygen gas generation in the presence of hydrogen peroxide. In vitro primary macrophage culture and in vivo subcutaneous implantation studies revealed that HepH-incorporated PPy electrodes reduced intracellular ROS levels and directed macrophage polarization toward an anti-inflammatory phenotype, mitigating collagenous scar tissue formation around the implanted electrodes. Finally, real-time electrocardiogram monitoring for 20 days demonstrated the extended in vivo signal sensitivity of the HepH-doped PPy electrodes as reliable implantable bioelectrodes.

Mechanosensor YAP cooperates with TGF-β1 signaling to promote myofibroblast activation and matrix stiffening in a 3D model of human cardiac fibrosis

Cardiac fibrosis is characterized by a maladaptive remodeling of the myocardium, which is controlled by various inflammatory pathways and cytokines. This remodeling is accompanied by a significant stiffening of the matrix, which may contribute to further activate collagen synthesis and scar formation. Evidence suggests that TGF-β1 signaling, the main pro-fibrotic pathway in cardiac fibrosis, might cooperates with the Hippo transcriptional pathway by activating YAP. To directly test the cooperation of mechanical cues and paracrine signaling in cardiac fibrosis, we developed a 3D model of cardiac extracellular matrix remodeling by generating tissue blocks with Gelatin Methacrylate, a bioink with tunable stiffness, and human cardiosphere-derived stromal cells. Using this strategy, we assessed the cooperation of TGF-β1 and YAP transcriptional factor to matrix compaction. Using mechanical compression tests, Masson's trichrome staining, immunofluorescence, and RT-qPCR, we demonstrate that pharmacological inhibition of YAP complex reverts almost completely the pro-compaction phenotype and the matrix-remodeling activity of cells treated with TGF-β1. Our data show a direct connection between the classical pro-fibrotic signaling driven by TGF-β1 and the mechanically activated pathways under the control of YAP in cardiac remodeling. Treatment with the elective drug targeting YAP is sufficient to override this cooperation with potential benefits for anti-fibrotic therapeutic applications. Statement of significanceHeart failure is a pathology in continuous growth worldwide, characterized by a progressive fibrosis, which decreases the pumping efficiency of the heart. Experimental evidences suggest that fibroblasts, normally responsible for the turnover of the cardiac matrix, are involved in myocardial fibrosis by differentiating into ‘myofibroblasts’. These cells remodel extensively the cardiac extracellular matrix and deposit abundant collagen with a consequent increase in stiffness. In the present contribution, we propose a new 3D model of cell-mediated cardiac extracellular matrix stiffening to investigate the mechano-chemical mechanisms underlying the onset of the pathology. We also consolidate a pharmacological treatment able to prevent the pathological activation of fibroblasts with potential benefits for anti-fibrotic treatment of the failing heart.

The Mortality Risk and Pulmonary Fibrosis Investigated by Time-Resolved Fluorescence Spectroscopy from Plasma in COVID-19 Patients.

A method of rapidly pointing out the risk of developing persistent pulmonary fibrosis from a sample of blood is extraordinarily needed for diagnosis, prediction of death, and post-infection prognosis assessment. Collagen scar formation has been found to play an important role in the lung remodeling following SARS-CoV-2 infection. For this reason, the concentration of collagen degradation products in plasma may reflect the process of lung remodeling and determine the extent of fibrosis. According to our previously published results of an in vitro study, an increase in the concentration of type III collagen degradation products in plasma resulted in a decrease in the fluorescence lifetime of plasma at a wavelength of 450 nm. The aim of this study was to use time-resolved fluorescence spectroscopy to assess pulmonary fibrosis, and to find out if the lifetime of plasma fluorescence is shortened in patients with COVID-19. The presented study is thus far the only one to explore the fluorescence lifetime of plasma in patients with COVID-19 and pulmonary fibrosis. The time-resolved spectrometer Life Spec II with the sub-nanosecond pulsed 360 nm EPLED® diode was used in order to measure the fluorescence lifetime of plasma. The survival analysis showed that COVID-19 mortality was associated with a decreased mean fluorescence lifetime of plasma. The AUC of mean fluorescence lifetime in predicting death was 0.853 (95% CI 0.735–0.972, p < 0.001) with a cut-off value of 7 ns, and with 62% sensitivity and 100% specificity. We observed a significant decrease in the mean fluorescence lifetime in COVID-19 non-survivors (p < 0.001), in bacterial pneumonia patients without COVID-19 (p < 0.001), and in patients diagnosed with idiopathic pulmonary fibrosis (p < 0.001), relative to healthy subjects. Furthermore, these results suggest that the development of pulmonary fibrosis may be a real and serious problem in former COVID-19 patients in the future. A reduction in the mean fluorescence lifetime of plasma was observed in many patients 6 months after discharge. On the basis of these data, it can be concluded that a decrease in the mean fluorescence lifetime of plasma at 450 nm may be a risk factor for mortality, and probably also for pulmonary fibrosis in hospitalized COVID-19 patients.

Graph-based homogenisation for modelling cardiac fibrosis

Fibrosis, the excess of extracellular matrix, can affect, and even block, propagation of action potential in cardiac tissue. This can result in deleterious effects on heart function, but the nature and severity of these effects depend strongly on the localisation of fibrosis and its by-products in cardiac tissue, such as collagen scar formation. Computer simulation is an important means of understanding the complex effects of fibrosis on activation patterns in the heart, but concerns of computational cost place restrictions on the spatial resolution of these simulations. In this work, we present a novel numerical homogenisation technique that uses both Eikonal and graph approaches to allow fine-scale heterogeneities in conductivity to be incorporated into a coarser mesh. Homogenisation achieves this by deriving effective conductivity tensors so that a coarser mesh can then be used for numerical simulation. By taking a graph-based approach, our homogenisation technique functions naturally on irregular grids and does not rely upon any assumptions of periodicity, even implicitly. We present results of action potential propagation through fibrotic tissue in two dimensions that show the graph-based homogenisation technique is an accurate and effective way to capture fine-scale domain information on coarser meshes in the context of sharp-fronted travelling waves of activation. As test problems, we consider excitation propagation in tissue with diffuse fibrosis and through a tunnel-like structure designed to test homogenisation, interaction of an excitation wave with a scar region, and functional re-entry.

ADAM15 is required for optimal collagen cross-linking and scar formation following myocardial infarction

Collagen cross-linking is an important step in optimal scar formation. Myocardial infarction (MI) results in loss of cardiomyocytes that are replaced with a scar (infarct) tissue. Disintegrin and metalloproteinases (ADAMs) are membrane-bound proteases that can interact with molecules intra- and extra-cellularly to mediate various cellular functions. ADAM15 is expressed in the myocardium, however its function in heart disease has been poorly explored. We utilized mice lacking ADAM15 (Adam15−/−) and wildtype (WT) mice. MI, induced by ligation of the left anterior descending artery, resulted in a transient but significant rise in ADAM15 protein in the WT myocardium at 3-days. Following MI, Adam15−/− mice exhibited markedly higher rate of left ventricular (LV) rupture compared to WT mice (66% vs. 15%, p<0.05). Echocardiography and strain analyses showed worsened LV dysfunction in Adam15−/− mice at 3days, prior to the onset of LV rupture. Second harmonic generation imaging revealed significant disarray and reduction in fibrillar collagen density in Adam15−/− compared to WT hearts. This was associated with lower insoluble and higher soluble collagen fractions, reduced cross-linking enzyme, lysyl oxidase-1 (LOX-1), and fibronectin which is required for LOX-1 function, in Adam15−/−-MI hearts. Post-MI myocardial inflammation was comparable between the genotypes. In vitro, primary adult cardiac fibroblasts from Adam15−/− mice showed suppressed activation in response to ischemia (hypoxia+nutrient depletion) compared to WT fibroblasts. Adam15-deficiency was associated with reduced PAK1(p21-activated kinase-1) levels, a regulator of fibronectin and LOX-1 expression. In female mice, the rate of post-MI LV rupture, PAK1 signaling, LOX-1 and fibronectin protein levels were comparable between Adam15−/− and WT, indicating less impact of ADAM15 loss in females post- MI. This study reports a novel function for ADAM15 in collagen cross-linking and optimal scar formation post-MI which may also apply to scar formation in other tissues.

"Smart Exosomes": A Smart Approach for Tendon Regeneration.

Shoulder tendon injuries are the common musculoskeletal disorder resulting in significant pain and disability. These injuries are characterized by chronic inflammation and tissue degeneration. Tendon pathology exhibits poor innate healing ability, enhanced inflammation, disorganized collagen fibers, calcification, and scar tissue formation affecting the normal healing process. Extracellular vesicle, especially exosomes, treatment has been emerging as a potential regenerative strategy improving the outcomes and biomechanical properties, accelerating tenocyte proliferation and migration, reducing inflammation, and facilitating the healing at tendon-bone interface. In this article, we critically reviewed the potential role of exosomes in tendon regeneration and their applications to accelerate the healing response following injury. In addition, the article provides novel insights on the concept of "Smart Exosomes" by programming/manipulating the secretome contents and functions of exosomes in the management of shoulder tendon injury. Impact statement The exosomes pose tremendous regenerative capacity in otherwise inherently poor tendon healing following shoulder injury. Understanding the exosome biology in the context of tendon injury offers immense opportunities for developing novel regenerative approaches. Herein, we focus on the novel concept of "Smart Exosomes" by programming the regenerative properties of exosomes as a next-generation management strategy for shoulder tendon injury.

IL-10 alleviates lipopolysaccharide-induced skin scarring via IL-10R/STAT3 axis regulating TLR4/NF-κB pathway in dermal fibroblasts.

Hypertrophic scar (HS) is a severe fibrotic skin disease. It has always been a major problem in clinical treatment, mainly because its pathogenesis has not been well understood. The roles of bacterial contamination and prolonged wound inflammation were considered significant. IL‐10 is a potent anti‐inflammatory cytokine and plays a pivotal role in wound healing and scar formation. Here, we investigate whether IL‐10 alleviates lipopolysaccharide (LPS)‐induced inflammatory response and skin scarring and explore the possible mechanism of scar formation. Our results showed that the expression of TLR4 and pp65 was higher in HS and HS‐derived fibroblasts (HSFs) than their counterpart normal skin (NS) and NS‐derived fibroblasts (NSFs). LPS could up‐regulate the expression of TLR4, pp65, Col I, Col III and α‐SMA in NSFs, but IL‐10 could down‐regulate their expression in both HSFs and LPS‐induced NSFs. Blocking IL‐10 receptor (IL‐10R) or the phosphorylation of STAT3, their expression was up‐regulated. In addition, in vitro and in vivo models results showed that IL‐10 could alleviate LPS‐induced fibroblast‐populated collagen lattice (FPCL) contraction and scar formation. Therefore, IL‐10 alleviates LPS‐induced skin scarring via IL‐10R/STAT3 axis regulating TLR4/NF‐κB pathway in dermal fibroblasts by reducing ECM proteins deposition and the conversion of fibroblasts to myofibroblasts. Our results indicate that IL‐10 can alleviate the LPS‐induced harmful effect on wound healing, reduce scar contracture, scar formation and skin fibrosis. Therefore, the down‐regulation of inflammation may lead to a suitable scar outcome and be a better option for improving scar quality.

Enhanced Integrin Activation of PLD2-Deficient Platelets Accelerates Inflammation after Myocardial Infarction

Background: Phospholipase (PL)D1 is crucial for integrin αIIbβ3 activation of platelets in arterial thrombosis and TNF-α-mediated inflammation and TGF-β-mediated collagen scar formation after myocardial infarction (MI) in mice. Enzymatic activity of PLD is not responsible for PLD-mediated TNF-α signaling and myocardial healing. The impact of PLD2 in ischemia reperfusion injury is unknown. Methods: PLD2-deficient mice underwent myocardial ischemia and reperfusion (I/R). Results: Enhanced integrin αIIbβ3 activation of platelets resulted in elevated interleukin (IL)-6 release from endothelial cells in vitro and enhanced IL-6 plasma levels after MI in PLD2-deficient mice. This was accompanied by enhanced migration of inflammatory cells into the infarct border zone and reduced TGF-β plasma levels after 72 h that might account for enhanced inflammation in PLD2-deficient mice. In contrast to PLD1, TNF-α signaling, infarct size and cardiac function 24 h after I/R were not altered when PLD2 was deleted. Furthermore, TGF-β plasma levels, scar formation and heart function were comparable between PLD2-deficient and control mice 21 days post MI. Conclusions: The present study contributes to our understanding about the role of PLD isoforms and altered platelet signaling in the process of myocardial I/R injury.

Evaluation of bacteriophage products against burn wound Methicillin-resistant Staphylococcus aureus (MRSA) infections

Abstract Background The major problem in the management of burn wounds are infections. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major cause of infection in burn wounds. Antibiotic resistant bacteria around the world has become a major therapeutic challenge. Bacteriophages and their lysine are suggested as an antimicrobial alternative agent. Phage display technique is suggested for production of recombinant lysine by Nano carrier technology. The approach of this study was to evaluate the potential of recombinant Nano phage efficacy in MRSA burn wound infection in vivo. Materials and methods The 3rd degree burn wounds were induced in 54 rats and infected with MRSA ATCC 33591 via the topical route in four groups. Burn wound size was measured in 0, 14, 21, 28 days. The efficacy of Nano phage gel was assessed on the basis of percentage collagen deposition, granulation tissue, neovascularization, fibroblastic maturity, re-epithelization, and scar formation in rats following treatment in 14, 21, 28 days. Results The results showed that the percentage of wound size were 3 cm on base line day and the average macroscopic wound healing rates were increased in the prevention groups receiving the recombinant Nano phage gel and natural phage gel, in the treatment groups with secondary infection receiving the recombinant Nano phage gel and the natural phage gel, and in the two control groups respectively. The average microscopic wound healing rates were increased in the prevention groups receiving the recombinant Nano phage gel and natural phage gel, in the treatment groups with secondary infection receiving the recombinant Nano phage gel and the natural phage gel, and in the two control groups respectively. Conclusions In conclusion the recombinant Nano phage gel is efficacy to treat and prevent MRSA burn wound infection.

IL-10 Alleviates Lipopolysaccharide-Induced Skin Scarring &lt;i&gt;via&lt;/i&gt; IL-10R/STAT3 Axis Regulating TLR4/NF-κB Pathway in Dermal Fibroblasts

Background: Hypertrophic scar (HS) is a serious fibrotic skin disease. The roles of bacterial contamination and prolonged inflammation in wound were considered to be significant. IL-10 plays a pivotal role in wound healing and scar formation. Here, we investigate whether IL-10 alleviates lipopolysaccharide (LPS)-induced inflammatory response and skin scarring, explore the possible mechanism in scar formation. Methods: RT-qPCR, Western blotting, histochemistry, immunostaining, ELISA array, electron microscope, fibroblast-populated collagen lattice (FPCL) and a rabbit ear scar model were used to investigate and validate the effect of IL-10 on LPS-stimulated scar formation. Findings: Our results showed that the expression of TLR4 and pp65 was higher in HS and HS-derived fibroblasts (HSFs) than their counterpart normal skin (NS) and NS-derived fibroblasts (NSFs). LPS could upregulate the expression of TLR4, pp65, Col I, Col III and α-SMA in NSFs, but IL-10 could downregulate their expression in both HSFs and LPS-induced NSFs. Blocking IL-10 receptor (IL-10R) or the phosphorylation of STAT3, their expression was upregulated. In addition, in vitro and in vivo models results showed that IL-10 could alleviate LPS-induced fibroblast-populated collagen lattice (FPCL) contraction and scar formation. Interpretation: Our study suggests that IL-10 may improve LPS-induced harmful to wound healing, reduce scar contracture and scar formation via IL-10R/STAT3 axis regulating TLR4/NF-κB pathway in dermal fibroblasts by reducing ECM proteins deposition and the conversion of HSFs to NSFs. Therefore, the downregulation of inflammation may be a better option for improving scar quality, and become potential therapeutic targets for scarring. Funding Statement: This research was supported by grants from the National Natural Science Foundation of China (81571914, and 81741105), and the Natural Science Foundation of Shaanxi Province (2018JQ8048). Declaration of Interests: The authors declare no conflicts of interest. Ethics Approval Statement: Written consent was obtained from all participants before surgery. All protocols used in this study were approved by the Ethics Committee of Xijing Hospital, affiliated to the Fourth Military Medical University of China. Animal experiments were approved by the Experimental Animal Committee of the Fourth Military Medical University (Xi’an, China).

Efficacy of Vitamin C Supplementation on Collagen Synthesis and Oxidative Stress After Musculoskeletal Injuries: A Systematic Review

Background:Recent investigations on the biochemical pathways after a musculoskeletal injury have suggested that vitamin C (ascorbic acid) may be a viable supplement to enhance collagen synthesis and soft tissue healing.Purpose:To (1) summarize vitamin C treatment protocols; (2) report on the efficacy of vitamin C in accelerating healing after bone, tendon, and ligament injuries in vivo and in vitro; and (3) report on the efficacy of vitamin C as an antioxidant protecting against fibrosis and promoting collagen synthesis.Study Design:Systematic review; Level of evidence, 2.Methods:A systematic review was performed, with the inclusion criteria of animal and human studies on vitamin C supplementation after a musculoskeletal injury specific to collagen cross-linking, collagen synthesis, and biologic healing of the bone, ligament, and tendon.Results:The initial search yielded 286 articles. After applying the inclusion and exclusion criteria, 10 articles were included in the final analysis. Of the preclinical studies evaluating fracture healing, 2 studies reported significantly accelerated bone healing in the vitamin C supplementation group compared with control groups. The 2 preclinical studies evaluating tendon healing reported significant increases in type I collagen fibers and scar tissue formation with vitamin C compared with control groups. The 1 preclinical study after anterior cruciate ligament (ACL) reconstruction reported significant short-term (1-6 weeks) improvements in ACL graft incorporation in the vitamin C group compared with control groups; however, there was no long-term (42 weeks) difference. Of the clinical studies evaluating fracture healing, 1 study reported no significant differences in the rate of fracture healing at 50 days or functional outcomes at 1 year. Vitamin C supplementation was shown to decrease oxidative stress parameters by neutralizing reactive oxygen species through redox modulation in animal models. No animal or human studies reported any adverse effects of vitamin C supplementation.Conclusion:Preclinical studies demonstrated that vitamin C has the potential to accelerate bone healing after a fracture, increase type I collagen synthesis, and reduce oxidative stress parameters. No adverse effects were reported with vitamin C supplementation in either animal models or human participants; thus, oral vitamin C appears to be a safe supplement but lacks clinical evidence compared with controls. Because of the limited number of human studies, further clinical investigations are needed before the implementation of vitamin C as a postinjury supplement.

Adipose tissue-derived stem cells inhibit hypertrophic scar (HS) fibrosis via p38/MAPK pathway.

The current study was designed to investigate the effects and underlying mechanisms of adipose tissue-derived stem cells (ADSCs) on hypertrophic scar (HS) fibrosis. Real-time quantitative polymerase chain reaction (qRT-PCR) and Western blot analysis were performed to detect the expression of collagen I (Col1), collagen III (Col3), and α-smooth muscle actin (α-SMA) after fibroblasts and cultured HS tissues were treated with ADSC medium. All data were analyzed by using SPSS17.0 software. Statistical analysis was performed by Student t tests. The in vitro study showed that ADSC medium decreased the expression of Col1, Col3, and α-SMA. In addition, the protein level of p-p38 was downregulated by ADSC medium treatment in a concentration dependent manner. The current study demonstrated that ADSC could decrease collagen deposition and scar formation inin vitro experiments. The regulation of the p38/MAPK signaling pathway might play an important role in the process.

The interstitium in cardiac repair: role of the immune-stromal cell interplay.

Cardiac regeneration, that is, restoration of the original structure and function in a damaged heart, differs from tissue repair, in which collagen deposition and scar formation often lead to functional impairment. In both scenarios, the early-onset inflammatory response is essential to clear damaged cardiac cells and initiate organ repair, but the quality and extent of the immune response vary. Immune cells embedded in the damaged heart tissue sense and modulate inflammation through a dynamic interplay with stromal cells in the cardiac interstitium, which either leads to recapitulation of cardiac morphology by rebuilding functional scaffolds to support muscle regrowth in regenerative organisms or fails to resolve the inflammatory response and produces fibrotic scar tissue in adult mammals. Current investigation into the mechanistic basis of homeostasis and restoration of cardiac function has increasingly shifted focus away from stem cell-mediated cardiac repair towards a dynamic interplay of cells composing the less-studied interstitial compartment of the heart, offering unexpected insights into the immunoregulatory functions of cardiac interstitial components and the complex network of cell interactions that must be considered for clinical intervention in heart diseases.

A Novel Small-Animal Model of Irradiated, Implant-Based Breast Reconstruction.

There is currently a need for a clinically relevant small-animal model for irradiated, implant-based breast reconstruction. Present models are inadequate in terms of suboptimal location of expander placement and mode of radiation delivery, correlating poorly with the human clinical scenario. The authors hypothesized that by delivering fractionated radiation and placing an expander under the scalp of the animal, they would achieve soft-tissue changes histologically analogous to those seen in human irradiated, implant-based breast reconstruction. This study consisted of 11 immunocompetent, hairless rats divided into three groups as follows: untreated control (n = 3), tissue-expanded scalps (n = 4), and fractionated irradiation plus tissue expansion of the scalp (n = 4). At the completion of the experiment for each group, skin tissue samples were analyzed histologically for vascularity, epidermal and dermal thickness, and collagen fiber alignment or scar formation. Expanded rat epidermis was significantly thicker and dermis was more vascular than nonexpanded skin. The authors observed a greater degree of collagen fiber alignment in the expanded group compared with nonexpanded skin. The combination of irradiation and expansion resulted in significant dermal thinning, vascular depletion, and increased scar formation compared with expanded skin alone. The authors describe a novel small-animal model for irradiated, implant-based breast reconstruction where histologic analysis shows structural changes in the skin consistent with known effects of radiation therapy and expansion in human skin. This model represents a significant improvement from previous ones and, as such, holds the potential to be used to test new therapeutic agents to improve clinical outcomes.

1454 Identification of Fetuin A as a potential modulator of scar formation

Wound healing generally leads to scarring in mature skin, but wounds created at early stages of development heal scarlessly. The exact mechanisms leading to scarless healing are not fully understood, but unique characteristics of fetal fibroblasts are believed to be important. Dermal fibroblasts from embryonic day 15 (E15) skin, which heals scarlessly, and embryonic day 18 (E18) skin, which heals with a scar, were compared by proteomics. Fetuin A (Fet A), a protein that has been suggested to be involved in inflammation, was identified as one of the top three differentially expressed proteins. Since inflammation is strongly linked to scar formation and Fet A was more highly expressed in fibroblasts from scar-forming skin, we hypothesized that Fet A may play a role in scar formation. To examine the role of Fet A in fetal wound healing, Fet A protein levels were first confirmed to be higher in E18 fibroblasts compared to E15 fibroblasts by Western blot. The ability of Fet A to induce scar formation was then tested by injecting recombinant Fet A into E15 fetal wounds, which normally heal without a scar. Injection of Fet A into E15 wounds caused the formation of a scar compared to control wounds, which healed scarlessly. The effects of Fet A on fibroblasts were also examined. Treatment of cultured fibroblasts from collagen-GFP reporter mice with Fet A resulted in a significant increase in GFP fluorescence, a readout of collagen expression, compared to untreated controls. These data suggest that Fet A may promote collagen production and scar formation. Further studies are being performed to dissect potential signaling mechanisms and to compare scar formation in wild-type and Fet A knockout mice.

Fto deficiency reduces infarct size and improves heart function after acute myocardial infarction

Obesity is one of the major risk factors that can lead to a myocardial infarction and can negatively influence subsequent cardiac remodeling. The onset of obesity is related to different genetic variants of the fat mass and obesity associated gene (Fto). Fto deficient mice were protected from obesity and showed an improved glucose tolerance under a high fat diet. In addition, it is known that Fto acts as an m6A RNA demethylase, whereby it can influence mRNA stability and translation. In a first approach, we used Fto deficient mice to perform an ischemic/reperfusion (I/R) model. At 24 h after reperfusion, Fto deficient mice already had a smaller infarct size compared to their wild type littermates. Over a time period of three weeks, the heart function was investigated by echocardiography. Three weeks after reperfusion, Fto deficient mice showed a preserved heart function and had reduced collagen scar formation compared to wild‐type control mice. Initial molecular studies indicated a reduction of the mTORC1 pathway and consequently a down regulation of S6K phosphorylation. For a first approach of therapeutic intervention, we used the Fto inhibitor rhein, which binds the active center of Fto and thereby inhibits its demethylase activity. Wild type mice were pre‐treated with rhein or the solvent over three weeks before the I/R procedure was performed. The rhein‐treated mice showed a significant reduction in the infarct size compared to the solvent treated littermates. In this study, we demonstrated that Fto deficiency can modulate the outcome of a myocardial infarction by improving left ventricular function and reduction of the infarct size.Support or Funding InformationSupported by the Deutsche Forschung Gesellschaft (DFG) as Part of the SFB 1116 (project number 236177352)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Lymphocytes at the Heart of Wound Healing.

The adult mammalian heart displays negligible regenerative capacity. Therefore, myocardial infarction (MI) often results in an irreversible loss of contractile tissue, leading to a collagenous scar formation, progressive remodelling and heart failure (HF). Over the past few years, emerging evidences indicate that a myocardial ischemic injury mobilizes not only sterile unspecific inflammation but also lymphocyte-mediated immune responses to cardiac auto-antigens. In the current chapter, we depict the infarcted heart as a "wounded" tissue and focus on the dynamic events leading to myocardial repair, with special emphasis on the role played by lymphocytes in this process.

Adipose tissue-derived stem cells suppress hypertrophic scar fibrosis via the p38/MAPK signaling pathway.

BackgroundHypertrophic scars (HS) generally occur after injury to the deep layers of the dermis, resulting in functional deficiency for patients. Growing evidence has been identified that the supernatant of adipose tissue-derived stem cells (ADSCs) significantly ameliorates fibrosis of different tissues, but limited attention has been paid to its efficacy on attenuating skin fibrosis. In this study, we explored the effect and possible mechanism of ADSC-conditioned medium (ADSC-CM) on HS.MethodReal-time quantitative polymerase chain reaction (qRT-PCR) and Western blotting were used to detect the expression of collagen I (Col1), collagen III (Col3), and α-smooth muscle actin (α-SMA) after fibroblasts and cultured HS tissues were stimulated with ADSC-CM and p38 inhibitor/activator. Immunofluorescence staining was performed to test the expression of α-SMA. Masson’s trichrome staining, hematoxylin and eosin (H&E) staining, and immunohistochemistry staining were carried out to assess the histological and pathological change of collagen in the BALB/c mouse excisional model. All data were analyzed by using SPSS17.0 software. Statistical analysis was performed by Student’s t tests.ResultsThe in vitro and ex vivo study revealed ADSC-CM decreased the expression of Col1, Col3, and α-SMA. Together, thinner and orderly arranged collagen was manifested in HS tissues cultured with ADSC-CM. Dramatically, the assessed morphology showed an accelerated healing rate, less collagen deposition, and col1- and col3-positive cells in the ADSC-CM treated group. Importantly, the protein level of p-p38 was downregulated in a concentration-dependent manner in HS-derived fibroblasts with ADSC-CM treatment, which further decreased the expression of p-p38 after the application of its inhibitor, SB203580. SB203580 led to an obvious decline in the expression of Col1, Col3, and α-SMA in fibroblasts and cultured HS tissues and presented more ordered arrangement and thinner collagen fibers in BALB/c mice. Lastly, anisomycin, an agonist of p38, upregulated the expression of fibrotic proteins and revealed more disordered structure and denser collagen fibers.ConclusionThis study demonstrated that ADSC-CM could decrease collagen deposition and scar formation in in vitro, ex vivo and in vivo experiments. The regulation of the p38/MAPK signaling pathway played an important role in the process. The application of ADSC-CM may provide a novel therapeutic strategy for HS treatment, and the anti-scarring effect can be achieved by inhibition of the p38/MAPK signaling pathway.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-016-0356-6) contains supplementary material, which is available to authorized users.

Genetic lineage tracing defines myofibroblast origin and function in the injured heart.

Cardiac fibroblasts convert to myofibroblasts with injury to mediate healing after acute myocardial infarction (MI) and to mediate long-standing fibrosis with chronic disease. Myofibroblasts remain a poorly defined cell type in terms of their origins and functional effects in vivo. Here we generate Postn (periostin) gene-targeted mice containing a tamoxifen-inducible Cre for cellular lineage-tracing analysis. This Postn allele identifies essentially all myofibroblasts within the heart and multiple other tissues. Lineage tracing with four additional Cre-expressing mouse lines shows that periostin-expressing myofibroblasts in the heart derive from tissue-resident fibroblasts of the Tcf21 lineage, but not endothelial, immune/myeloid or smooth muscle cells. Deletion of periostin+ myofibroblasts reduces collagen production and scar formation after MI. Periostin-traced myofibroblasts also revert back to a less-activated state upon injury resolution. Our results define the myofibroblast as a periostin-expressing cell type necessary for adaptive healing and fibrosis in the heart, which arises from Tcf21+ tissue-resident fibroblasts.

3D Printed Stem-Cell-Laden, Microchanneled Hydrogel Patch for the Enhanced Release of Cell-Secreting Factors and Treatment of Myocardial Infarctions.

Over the past several years, biomaterials loaded with mesenchymal stem cells (MSCs) have increasingly been used to reduce the myocardial fate of postinfarction collagen deposition and scar tissue formation. Despite successful gains, therapeutic efficacy has remained limited because of restricted transport of cell-secreting factors at the site of implantation. We hypothesized that an MSC-laden hydrogel patch with multiple microchannels would retain transplanted cells on target tissue and support transport of cell-secreting factors into tissue. By doing so, the gel patch will improve the therapeutic potential of the cells and minimize the degradation of myocardial tissue postinfarction. To examine this hypothesis, a stereolithographic apparatus (SLA) was used to introduce microchannels of controlled diameters (e.g., 500 and 1000 μm) during in situ cross-linking reaction of poly(ethylene glycol)dimethacrylate solution suspended with cells. Placement of the MSC-laden, microchanneled gel patch on the occluded left coronary artery in a murine model showed significant improvement in the ejection fraction, fractional shortening, and stroke volume, compared with gel patches without MSCs and MSC-laden gel patches without microchannels. In particular, the microchannels significantly reduced the number of cells required to recover cardiac function, while minimizing cardiac remodeling. In sum, the microchanneled gel patch would provide a means to prevent abnormal fibrosis resulting from acute ischemic injury.