Formation and function of the myofibroblast during tissue repair

Role of Cardiac Fibroblasts in Cardiac Injury and Repair

PURPOSE OF REVIEW

The pathological remodeling of cardiac tissue after injury or disease leads to scar formation. Our knowledge of the role of nonmyocytes, especially fibroblasts, in cardiac injury and repair continues to increase with technological advances in both experimental and clinical studies. Here, we aim to elaborate on cardiac fibroblasts by describing their origins, dynamic cellular states after injury, and heterogeneity in order to understand their role in cardiac injury and repair.

RECENT FINDINGS

With the improvement in genetic lineage tracing technologies and the capability to profile gene expression at the single-cell level, we are beginning to learn that manipulating a specific population of fibroblasts could mitigate severe cardiac fibrosis and promote cardiac repair after injury. Cardiac fibroblasts play an indispensable role in tissue homeostasis and in repair after injury. Activated fibroblasts or myofibroblasts have time-dependent impacts on cardiac fibrosis. Multiple signaling pathways are involved in modulating fibroblast states, resulting in the alteration of fibrosis. Modulating a specific population of cardiac fibroblasts may provide new opportunities for identifying novel treatment options for cardiac fibrosis.

Role of Fibroblasts and Myofibroblasts on the Pathogenesis and Treatment of Pelvic Organ Prolapse

Pelvic organ prolapse (POP) is a multifactorial connective tissue disorder caused by damage to the supportive structures of the pelvic floor, leading to the descent of pelvic organs in the vagina. In women with POP, fibroblast function is disturbed or altered, which causes impaired collagen metabolism that affects the mechanical properties of the tissue. Ideal surgical repair, either native tissue repair or POP surgery using an implant, aims to create a functional pelvic floor that is load-bearing, activating fibroblasts to regulate collagen metabolism without creating fibrotic tissue. Fibroblast function plays a crucial role in the pathophysiology of POP by directly affecting the connective tissue quality. On the other hand, fibroblasts determine the success of the POP treatment, as the fibroblast-to-(myo)fibroblast transition is the key event during wound healing and tissue repair. In this review, we aim to resolve the question of “cause and result” for the fibroblasts in the development and treatment of POP. This review may contribute to preventing the development and progress of anatomical abnormalities involved in POP and to optimizing surgical outcomes.

Wound healing properties of a fibrin-based dermal replacement scaffold

When serious cutaneous injury occurs, the innate wound healing process attempts to restore the skin's appearance and function. Wound healing outcome is affected by factors such as contraction, revascularisation, regeneration versus fibrosis and re-epithelialisation and is also strongly influenced by the pattern and extent of damage to the dermal layer. Dermal replacement scaffolds have been designed to substitute for lost tissue, provide a structure to promote dermal regeneration, and aid skin grafting, resulting in a superior healing outcome. In this study the wound healing properties of a novel fibrin-alginate dermal scaffold were assessed in the porcine wound healing model and also compared to two widely used dermal scaffolds and grafting alone. The fibrin-alginate scaffold, unlike the other scaffolds tested, is not used in combination with an overlying skin graft. Fibrin scaffold treated wounds showed increased, sustained superficial blood flow and reduced contraction during early healing while showing comparable wound closure, re-epithelialisation and final wound outcome to other treatments. The increase in early wound vascularisation coupled with a decrease in contraction and no requirement for a skin graft suggest that the fibrin-based scaffold could provide an effective, distinctive treatment option to improve healing outcomes in human patients.

NF-кB c-Rel modulates pre-fibrotic changes in human fibroblasts

Skin fibrosis is one central hallmark of the heterogeneous autoimmune disease systemic sclerosis. So far, there are hardly any standardized and effective treatment options. Pathogenic mechanisms underlying fibrosis comprise excessive and uncontrolled myofibroblast differentiation, increased extracellular matrix protein (ECM) synthesis and an intensification of the forces exerted by the cytoskeleton. A deeper understanding of fibroblast transformation could help to prevent or reverse fibrosis by specifically interfering with abnormally regulated signaling pathways. The transcription factor NF-κB has been implicated in the progression of fibrotic processes. However, the cellular processes regulated by NF-κB in fibrosis as well as the NF-κB isoforms preferentially involved are still completely unknown. In an in vitro model of fibrosis, we consistently observed the induction of the c-Rel subunit of NF-κB. Functional abrogation of c-Rel by siRNA resulted in diminished cell contractility of dermal fibroblasts in relaxed, but not in stressed 3D collagen matrices. Furthermore, directed migration was reduced after c-Rel silencing and total N-cadherin expression level was diminished, possibly mediating the observed cellular defects. Therefore, NF-кB c-Rel impacts central cellular adhesion markers and processes which negatively regulate fibrotic progression in SSc pathophysiology.

Matrix Stiffening Enhances DNCB-Induced IL-6 Secretion in Keratinocytes Through Activation of ERK and PI3K/Akt Pathway

Matrix stiffness, a critical physical property of the cellular environment, is implicated in epidermal homeostasis. In particular, matrix stiffening during the pathological progression of skin diseases appears to contribute to cellular responses of keratinocytes. However, it has not yet elucidated the molecular mechanism underlying matrix-stiffness-mediated signaling in coordination with chemical stimuli during inflammation and its effect on proinflammatory cytokine production. In this study, we demonstrated that keratinocytes adapt to matrix stiffening by increasing cell–matrix adhesion via actin cytoskeleton remodeling. Specifically, mechanosensing and signal transduction are coupled with chemical stimuli to regulate cytokine production, and interleukin-6 (IL-6) production is elevated in keratinocytes on stiffer substrates in response to 2,4-dinitrochlorobenzene. We demonstrated that β1 integrin and focal adhesion kinase (FAK) expression were enhanced with increasing stiffness and activation of ERK and the PI3K/Akt pathway was involved in stiffening-mediated IL-6 production. Collectively, our results reveal the critical role of matrix stiffening in modulating the proinflammatory response of keratinocytes, with important clinical implications for skin diseases accompanied by pathological matrix stiffening.

3D in vitro M2 macrophage model to mimic modulation of tissue repair

Distinct anti-inflammatory macrophage (M2) subtypes, namely M2a and M2c, are reported to modulate the tissue repair process tightly and chronologically by modulating fibroblast differentiation state and functions. To establish a well-defined three-dimensional (3D) cell culture model to mimic the tissue repair process, we utilized THP-1 human monocytic cells and a 3D collagen matrix as a biomimetic tissue model. THP-1 cells were differentiated into macrophages, and activated using IL-4/IL-13 (M_IL-4/IL-13) and IL-10 (M_IL-10). Both activated macrophages were characterized by both their cell surface marker expression and cytokine secretion profile. Our cell characterization suggested that M_IL-4/IL-13 and M_IL-10 demonstrate M2a- and M2c-like subtypes, respectively. To mimic the initial and resolution phases during the tissue repair, both activated macrophages were co-cultured with fibroblasts and myofibroblasts. We showed that M_IL-4/IL-13 were able to promote matrix synthesis and remodeling by induction of myofibroblast differentiation via transforming growth factor beta-1 (TGF-β1). On the contrary, M_IL-10 demonstrated the ability to resolve the tissue repair process by dedifferentiation of myofibroblast via IL-10 secretion. Overall, our study demonstrated the importance and the exact roles of M2a and M2c-like macrophage subtypes in coordinating tissue repair in a biomimetic model. The established model can be applied for high-throughput platforms for improving tissue healing and anti-fibrotic drugs testing, as well as other biomedical studies.

Nanostring-Based Identification of the Gene Expression Profile in Trigger Finger Samples

Trigger finger is a common yet vastly understudied fibroproliferative hand pathology, severely affecting patients' quality of life. Consistent trauma due to inadequate positioning within the afflicted finger's tendon/pulley system leads to cellular dysregulation and eventual fibrosis. While the genetic characteristics of the fibrotic tissue in the trigger finger have been studied, the pathways that govern the initiation and propagation of fibrosis are still unknown. The complete gene expression profile of the trigger finger has never been explored. Our study has used the Nanostring nCounter gene expression assay to investigate the molecular signaling involved in trigger finger pathogenesis. We collected samples from patients undergoing trigger finger (n = 4) release surgery and compared the gene expression to carpal tunnel tissue (n = 4). Nanostring nCounter analysis identified 165 genes that were differentially regulated; 145 of these genes were upregulated, whereas 20 genes were downregulated. We found that several collagen genes were significantly upregulated, and a regulatory matrix metalloproteinase (MMP), MMP-3, was downregulated. Bioinformatic analysis revealed that several known signaling pathways were dysregulated, such as the TGF-β1 and Wnt signaling pathways. We also found several novel signaling pathways (e.g., PI3K, MAPK, JAK-STAT, and Notch) differentially regulated in trigger finger. The outcome of our study helps in understanding the molecular signaling pathway involved in the pathogenesis of the trigger finger.

Molecular Mechanisms and Cellular Contribution from Lung Fibrosis to Lung Cancer Development

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibrosing interstitial lung disease (ILD) of unknown aetiology, with a median survival of 2-4 years from the time of diagnosis. Although IPF has unknown aetiology by definition, there have been identified several risks factors increasing the probability of the onset and progression of the disease in IPF patients such as cigarette smoking and environmental risk factors associated with domestic and occupational exposure. Among them, cigarette smoking together with concomitant emphysema might predispose IPF patients to lung cancer (LC), mostly to non-small cell lung cancer (NSCLC), increasing the risk of lung cancer development. To this purpose, IPF and LC share several cellular and molecular processes driving the progression of both pathologies such as fibroblast transition proliferation and activation, endoplasmic reticulum stress, oxidative stress, and many genetic and epigenetic markers that predispose IPF patients to LC development. Nintedanib, a tyrosine-kinase inhibitor, was firstly developed as an anticancer drug and then recognized as an anti-fibrotic agent based on the common target molecular pathway. In this review our aim is to describe the updated studies on common cellular and molecular mechanisms between IPF and lung cancer, knowledge of which might help to find novel therapeutic targets for this disease combination.

A deep learning approach to identify and segment alpha-smooth muscle actin stress fiber positive cells

Cardiac fibrosis is a pathological process characterized by excessive tissue deposition, matrix remodeling, and tissue stiffening, which eventually leads to organ failure. On a cellular level, the development of fibrosis is associated with the activation of cardiac fibroblasts into myofibroblasts, a highly contractile and secretory phenotype. Myofibroblasts are commonly identified in vitro by the de novo assembly of alpha-smooth muscle actin stress fibers; however, there are few methods to automate stress fiber identification, which can lead to subjectivity and tedium in the process. To address this limitation, we present a computer vision model to classify and segment cells containing alpha-smooth muscle actin stress fibers into 2 classes (α-SMA SF+ and α-SMA SF-), with a high degree of accuracy (cell accuracy: 77%, F1 score 0.79). The model combines standard image processing methods with deep learning techniques to achieve semantic segmentation of the different cell phenotypes. We apply this model to cardiac fibroblasts cultured on hyaluronic acid-based hydrogels of various moduli to induce alpha-smooth muscle actin stress fiber formation. The model successfully predicts the same trends in stress fiber identification as obtained with a manual analysis. Taken together, this work demonstrates a process to automate stress fiber identification in in vitro fibrotic models, thereby increasing reproducibility in fibroblast phenotypic characterization.

Mechanosensing by TRPV4 mediates stiffness-induced foreign body response and giant cell formation

Implantation of biomaterials or devices into soft tissue often leads to the development of the foreign body response (FBR), an inflammatory condition that can cause implant failure, tissue injury, and death of the patient. Macrophages accumulate and fuse to generate destructive foreign body giant cells (FBGCs) at the tissue-implant interface, leading to the development of fibrous scar tissue around the implant that is generated by myofibroblasts. We previously showed that the FBR in vivo and FBGC formation in vitro require transient receptor potential vanilloid 4 (TRPV4), a mechanosensitive ion channel. Here, we report that TRPV4 was required specifically for the FBR induced by implant stiffness independently of biochemical cues and for intracellular stiffening that promotes FBGC formation in vitro. TRPV4 deficiency reduced collagen deposition and the accumulation of macrophages, FBGCs, and myofibroblasts at stiff, but not soft, implants in vivo and inhibited macrophage-induced differentiation of wild-type fibroblasts into myofibroblasts in vitro. Atomic force microscopy demonstrated that TRPV4 was required for implant-adjacent tissue stiffening in vivo and for cytoskeletal remodeling and intracellular stiffening induced by fusogenic cytokines in vitro. Together, these data suggest a mechanism whereby a reciprocal functional interaction between TRPV4 and substrate stiffness leads to cytoskeletal remodeling and cellular force generation to promote FBGC formation during the FBR.

The pig as a model system for investigating the recruitment and contribution of myofibroblasts in skin healing

In the skin-healing field, porcine models are regarded as a useful analogue for human skin due to their numerous anatomical and physiological similarities. Despite the widespread use of porcine models in skin healing studies, the initial origin, recruitment and transition of fibroblasts to matrix-secreting contractile myofibroblasts are not well defined for this model. In this review, we discuss the merit of the pig as an animal for studying myofibroblast origin, as well as the challenges associated with assessing their contributions to skin healing. Although a variety of wound types (incisional, partial thickness, full thickness, burns) have been investigated in pigs in attempts to mimic diverse injuries in humans, direct comparison of human healing profiles with regards to myofibroblasts shows evident differences. Following injury in porcine models, which often employ juvenile animals, myofibroblasts are described in the developing granulation tissue at 4 days, peaking at Days 7-14, and persisting at 60 days post-wounding, although variations are evident depending on the specific pig breed. In human wounds, the presence of myofibroblasts is variable and does not correlate with the age of the wound or clinical contraction. Our comparison of porcine myofibroblast-mediated healing processes with those in humans suggests that further validation of the pig model is essential. Moreover, we identify several limitations evident in experimental design that need to be better controlled, and standardisation of methodologies would be beneficial for the comparison and interpretation of results. In particular, we discuss anatomical location of the wounds, their size and depth, as well as the healing microenvironment (wet vs. moist vs. dry) in pigs and how this could influence myofibroblast recruitment. In summary, although a widespread model used in the skin healing field, further research is required to validate pigs as a useful analogue for human healing with regards to myofibroblasts.

An Emerging Role for Calcium Signaling in Cancer-Associated Fibroblasts

Tumors exist in a complex milieu where interaction with their associated microenvironment significantly contributes to disease progression. Cancer-associated fibroblasts (CAFs) are the primary component of the tumor microenvironment and participate in complex bidirectional communication with tumor cells. CAFs support the development of various hallmarks of cancer through diverse processes, including direct cell-cell contact, paracrine signaling, and remodeling and deposition of the extracellular matrix. Calcium signaling is a key second messenger in intra- and inter-cellular signaling pathways that contributes to cancer progression; however, the links between calcium signaling and CAFs are less well-explored. In this review, we put into context the role of calcium signaling in interactions between cancer cells and CAFs, with a focus on migration, proliferation, chemoresistance, and genetic instability.

IL-6 in the Ecosystem of Head and Neck Cancer: Possible Therapeutic Perspectives

Interleukin-6 (IL-6) is a highly potent cytokine involved in multiple biological processes. It was previously reported to play a distinct role in inflammation, autoimmune and psychiatric disorders, ageing and various types of cancer. Furthermore, it is understood that IL-6 and its signaling pathways are substantial players in orchestrating the cancer microenvironment. Thus, they appear to be potential targets in anti-tumor therapy. The aim of this article is to elucidate the role of IL-6 in the tumor ecosystem and to review the possible therapeutic approaches in head and neck cancer.

The Role of Rho GTPases During Fibroblast Spreading, Migration, and Myofibroblast Differentiation in 3D Synthetic Fibrous Matrices

INTRODUCTION

Connective tissue repair and mechanosensing are tightly entwined in vivo and occur within a complex three-dimensional (3D), fibrous extracellular matrix (ECM). Typically driven by activated fibroblasts, wound repair involves well-defined steps of cell spreading, migration, proliferation, and fibrous ECM deposition. While the role of Rho GTPases in regulating these processes has been explored extensively in two-dimensional cell culture models, much less is known about their role in more physiologic, 3D environments.

METHODS

We employed a 3D, fibrous and protease-sensitive hydrogel model of interstitial ECM to study the interplay between Rho GTPases and fibrous matrix cues in fibroblasts during wound healing.

RESULTS

Modulating fiber density within protease-sensitive hydrogels, we confirmed previous findings that heightened fiber density promotes fibroblast spreading and proliferation. The presence of matrix fibers furthermore corresponded to increased cell migration speeds and macroscopic hydrogel contraction arising from fibroblast generated forces. During fibroblast spreading, Rac1 and RhoA GTPase activity proved crucial for fiber-mediated cell spreading and contact guidance along matrix fibers, while Cdc42 was dispensable. In contrast, interplay between RhoA, Rac1, and Cdc42 contributed to fiber-mediated myofibroblast differentiation and matrix contraction over longer time scales.

CONCLUSION

These observations may provide insights into tissue repair processes in vivo and motivate the incorporation of cell-adhesive fibers within synthetic hydrogels for material-guided wound repair strategies.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12195-021-00698-5.

The interplay between extracellular matrix and progenitor/stem cells during wound healing: Opportunities and future directions

Skin wound healing, a dynamic physiological process, progresses through coordinated overlapping phases to restore skin integrity. In some pathological conditions such as diabetes, wounds become chronic and hard-to-heal resulting in substantial morbidity and healthcare costs. Despite much advancement in understanding mechanisms of wound healing, chronic and intractable wounds are still a considerable challenge to nations' health care systems. Extracellular matrix (ECM) components play pivotal roles in all phases of wound healing. Therefore, a better understanding of their roles during wound healing can help improve wound care approaches. The ECM provides a 3D structure and forms the stem cell niche to support stem cell adhesion and survival and to regulate stem cell behavior and fate. Also, this dynamic structure reserves growth factors, regulates their bioavailability and provides biological signals. In various diseases, the composition and stiffness of the ECM is altered, which as a result, disrupts bidirectional cell-ECM interactions and tissue regeneration. Hence, due to the impact of ECM changes on stem cell fate during wound healing and the possibility of exploring new strategies to treat chronic wounds through manipulation of these interactions, in this review, we will discuss the importance/impact of ECM in the regulation of stem cell function and behavior to find ideal wound repair and regeneration strategies. We will also shed light on the necessity of using ECM in future wound therapy and highlight the potential roles of various biomimetic and ECM-based scaffolds as functional ECM preparations to mimic the native stem cell niche.

Gellan gum-gelatin viscoelastic hydrogels as scaffolds to promote fibroblast differentiation

Fabricating hydrogel scaffolds that are both bioreactive toward fibroblasts while still mechanically compatible with surrounding tissue is a major challenge in tissue engineering. This is because the outcome of scaffold implantation is largely determined by fibroblasts differentiating toward myofibroblasts, which is characterized by the expression of α-smooth muscle actin (α-SMA). Previous studies promoted fibroblasts differentiation by increasing scaffold substrate stiffness. However, the stiffness of scaffold has to be compatible with surrounding tissue, as mismatched stiffness may cause initial hyperplasia and inappropriate endothelial layer development. Therefore, we adjusted the hydrogel chemical component, and thus viscoelasticity to affect the mechano-signaling of fibroblasts and promote fibroblasts differentiation. Elastic gellan gum and viscoelastic gelatin were hybridized at different ratios to fabricate hydrogel scaffold with varied stress-relaxation. Vitronectin (VN) was used to further regulate the interaction between fibroblasts and the substrate. Fibroblast differentiation, characterized by α-SMA area per cell, increased from~3000-4000 μm²/cell on less viscoelastic gels to ~5000 μm²/cell on the most viscoelastic gel. Fibroblasts seeded on hydrogels had a slower migration rate on more viscoelastic hydrogels (slowest at 38 ± 14 μm/h) compared to the migration speed on less viscoelastic hydrogels (74 ± 20 μm/h). VN slowed the migration speed on all hydrogels. The organization of collagen deposited by fibroblasts cultured on the hydrogels was characterized by second harmonic generation (SHG), which showed that collagen was more organized (parallel) on more viscoelastic hydrogels. In summary, we provided a novel strategy to fabricate hydrogel scaffolds that can promote fibroblasts differentiation while keeping the stiffness compatible with blood vessels. The most viscoelastic hydrogel studied here meets these requirements best.

Polymer-Based Nanotherapeutics for Burn Wounds

Burn wounds are complex and intricate injuries that have become a common cause of trauma leading to significant mortality and morbidity every year. Dressings are applied to burn wounds with the aim of promoting wound healing, preventing burn infection and restoring skin function. The dressing protects the injury and contributes to recovery of dermal and epidermal tissues. Polymer-based nanotherapeutics are increasingly being exploited as burn wound dressings. Natural polymers such as cellulose, chitin, alginate, collagen, gelatin and synthetic polymers like poly (lactic-co-glycolic acid), polycaprolactone, polyethylene glycol, and polyvinyl alcohol are being obtained as nanofibers by nanotechnological approaches like electrospinning and have shown wound healing and re-epithelialization properties. Their biocompatibility, biodegradability, sound mechanical properties and unique structures provide optimal microenvironment for cell proliferation, differentiation, and migration contributing to burn wound healing. The polymeric nanofibers mimic collagen fibers present in extracellular matrix and their high porosity and surface area to volume ratio enable increased interaction and sustained release of therapeutics at the site of thermal injury. This review is an attempt to compile all recent advances in the use of polymer-based nanotherapeutics for burn wounds. The various natural and synthetic polymers used have been discussed comprehensively and approaches being employed have been reported. With immense research effort that is currently being invested in this field and development of proper characterization and regulatory framework, future progress in burn treatment is expected to occur. Moreover, appropriate preclinical and clinical research will provide evidence for the great potential that polymer-based nanotherapeutics hold in the management of burn wounds.

Recent advances in nanotherapeutics for the treatment of burn wounds

Moderate or severe burns are potentially devastating injuries that can even cause death, and many of them occur every year. Infection prevention, anti-inflammation, pain management and administration of growth factors play key roles in the treatment of burn wounds. Novel therapeutic strategies under development, such as nanotherapeutics, are promising prospects for burn wound treatment. Nanotherapeutics, including metallic and polymeric nanoformulations, have been extensively developed to manage various types of burns. Both human and animal studies have demonstrated that nanotherapeutics are biocompatible and effective in this application. Herein, we provide comprehensive knowledge of and an update on the progress of various nanoformulations for the treatment of burn wounds.

Mechanisms of Endothelial-to-Mesenchymal Transition Induction by Extracellular Matrix Components in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis can be caused by different factors, including accumulation of pathological extracellular matrix (ECM) with abnormal composition, stiffness, and architecture in the lung tissue. We studied the effect of ECM produced by lung fibroblasts of healthy mice or mice with bleomycin-induced pulmonary fibrosis on the process of endothelialto- mesenchymal transition, one of the main sources of effector myofibroblasts in fibrosis progression. Despite stimulation of spontaneous and TGFβ-1-induced differentiation of fibroblasts into myofibroblasts by fibrotic ECM, the appearance of α-SMA, the main marker of myofibroblasts, and its integration in stress fibrils in endotheliocytes were not observed under similar conditions. However, the expression of transcription factors SNAI1 and SNAI2/Slug and the production of components of fibrotic ECM (specific EDA-fibronectin splice form and collagen type I) were increased in endotheliocytes cultured on fibrotic ECM. Endothelium also demonstrated increased cell velocity in the models of directed cell migration. These data indicate activation of the intermediate state of the endothelial-to-mesenchymal transition in endotheliocytes upon contact with fibrotic, but not normal stromal matrix. In combination with the complex microenvironment that develops during fibrosis progression, it can lead to the replenishment of myofibroblasts pool from the resident endothelium.

A Dual Role for Death Receptor 5 in Regulating Cardiac Fibroblast Function

The fibrotic response is involved in nearly all forms of heart failure and dysregulated responses can lead to enhanced cardiac dysfunction. TNF-related apoptosis-inducing ligand (TRAIL) and its receptor, death receptor (DR) 5, are associated with multiple forms of heart failure, but their role in the heart is poorly defined. Our previous study identified DR5 expression on cardiac fibroblasts however, the impact of DR5 on fibroblast function remains unexplored. To investigate the role of DR5 in cardiac fibroblasts, a variety of fibroblast functions were examined following treatment with the endogenous ligand, TRAIL, or small molecule agonist, bioymifi. DR5 activation did not induce apoptosis in naïve fibroblasts but activated ERK1/2 signaling to increase proliferation. However, upon activation and differentiation to myofibroblasts, DR5 expression was elevated, and DR5 agonists induced caspase 3 activation resulting in myofibroblast apoptosis. To investigate the impact of DR5 regulation of fibroblasts in vivo, a chronic isoproterenol administration model of heart failure was used. Wild-type (WT) mice receiving isoproterenol had increased hypertrophy, cardiomyocyte death, and fibrosis and decreased contractility compared to vehicle treated animals. DR5 knockout (KO) mice had no overt baseline phenotype however, following isoproterenol infusion, increased cardiomyocyte death and hypertrophy in comparison to isoproterenol treated WT animals was observed. DR5KO mice had an augmented fibrotic response with isoproterenol treatment compared with WT, which corresponded with additional decreases in contractility. These findings identify a dual role for DR5 in cardiac fibroblast function through enhanced naïve fibroblast proliferation, which switches to a pro-apoptotic function upon differentiation to myofibroblasts. This is important in heart failure where DR5 activation suppresses maladaptive remodeling and may represent a novel therapeutic target for the treatment of heart failure.

Fluorescent light energy modulates healing in skin grafted mouse model

Skin grafting is often the only treatment for skin trauma when large areas of tissue are affected. This surgical intervention damages the deeper dermal layers of the skin with implications for wound healing and a risk of scar development. Photobiomodulation (PBM) therapy modulates biological processes in different tissues, with a positive effect on many cell types and pathways essential for wound healing. This study investigated the effect of fluorescent light energy (FLE) therapy, a novel type of PBM, on healing after skin grafting in a dermal fibrotic mouse model. Split-thickness human skin grafts were transplanted onto full-thickness excisional wounds on nude mice. Treated wounds were monitored, and excised xenografts were examined to assess healing and pathophysiological processes essential for developing chronic wounds or scarring. Results demonstrated that FLE treatment initially accelerated re-epithelialization and rete ridge formation, while later reduced neovascularization, collagen deposition, myofibroblast and mast cell accumulation, and connective tissue growth factor expression. While there was no visible difference in gross morphology, we found that FLE treatment promoted a balanced collagen remodeling. Collectively, these findings suggest that FLE has a conceivable effect at balancing healing after skin grafting, which reduces the risk of infections, chronic wound development, and fibrotic scarring.

ELF3 mediates IL-1α induced differentiation of mesenchymal stem cells to inflammatory iCAFs

Stromal cells in the tumor microenvironment regulate the immune landscape and tumor progression. Yet, the ontogeny and heterogeneity of reactive stromal cells within tumors is not well understood. Carcinoma-associated fibroblasts exhibiting an inflammatory phenotype (iCAFs) have been identified within multiple cancers; however, mechanisms that lead to their recruitment and differentiation also remain undefined. Targeting these mechanisms therapeutically may be important in managing cancer progression. Here, we identify the ELF3 transcription factor as the canonical mediator of IL-1α-induced differentiation of prostate mesenchymal stem cells to an iCAF phenotype, typical of the tumor microenvironment. Furthermore, IL-1α-induced iCAFs were subsequently refractive to TGF-β1 induced trans-differentiation to a myofibroblast phenotype (myCAF), another key carcinoma-associated fibroblast subtype typical of reactive stroma in cancer. Restricted trans-differentiation was associated with phosphorylation of the YAP protein, indicating that interplay between ELF3 action and activation of the Hippo pathway are critical for restricting trans-differentiation of iCAFs. Together, these data show that the IL-1α/ELF3/YAP pathways are coordinate for regulating inflammatory carcinoma-associated fibroblast differentiation.

Mechanical stretch sustains myofibroblast phenotype and function in microtissues through latent TGF-β1 activation

Developing methods to study tissue mechanics and myofibroblast activation may lead to new targets for therapeutic treatments that are urgently needed for fibrotic disease. Microtissue arrays are a promising approach to conduct relatively high-throughput research into fibrosis as they recapitulate key biomechanical aspects of the disease through a relevant 3D extracellular environment. In early work, our group developed a device called the MVAS-force to stretch microtissues while enabling simultaneous assessment of their dynamic mechanical behavior. Here, we investigated TGF-β1-induced fibroblast to myofibroblast differentiation in microtissue cultures using our MVAS-force device through assessing α-SMA expression, contractility and stiffness. In doing so, we linked cell-level phenotypic changes to functional changes that characterize the clinical manifestation of fibrotic disease. As expected, TGF-β1 treatment promoted a myofibroblastic phenotype and microtissues became stiffer and possessed increased contractility. These changes were partially reversible upon TGF-β1 withdrawal under a static condition, while, in contrast, long-term cyclic stretching maintained myofibroblast activation. This pro-fibrotic effect of mechanical stretching was absent when TGF-β1 receptors were inhibited. Furthermore, stretching promoted myofibroblast differentiation when microtissues were given latent TGF-β1. Altogether, these results suggest that external mechanical stretch may activate latent TGF-β1 and, accordingly, might be a powerful stimulus for continued myofibroblast activation to progress fibrosis. Further exploration of this pathway with our approach may yield new insights into myofibroblast activation and more effective therapeutic treatments for fibrosis.

Nr4A1 modulates inflammation-associated intestinal fibrosis and dampens fibrogenic signaling in myofibroblasts

Intestinal fibrosis is a common complication of the inflammatory bowel diseases (IBDs), contributing to tissue stiffening and luminal narrowing. Human nuclear receptor 4A 1 (NR4A1) was previously reported to regulate mesenchymal cell function and dampen fibrogenic signaling. NR4A1 gene variants are associated with IBD risk, and it has been shown to regulate intestinal inflammation. Here, we tested the hypothesis that NR4A1 acts as a negative regulator of intestinal fibrosis through regulating myofibroblast function. Using the SAMP1/YitFc mouse, we tested whether two pharmacological agents known to enhance NR4A1 signaling, cytosporone B (Csn-B) or 6-mercaptopurine (6-MP), could reduce fibrosis. We also used the dextran sulfate sodium (DSS) model of colitis and assessed the magnitude of colonic fibrosis in mouse nuclear receptor 4A 1 (Nr4a1^-/-) and their wild-type littermates (Nr4a1^+/+). Lastly, intestinal myofibroblasts isolated from Nr4a1^-/- and Nr4a1^+/+ mice or primary human intestinal myofibroblasts were stimulated with transforming growth factor-β1 (TGF-β1), in the presence or absence of Csn-B or 6-MP, and proliferation and ECM gene expression assessed. Csn-B or 6-MP treatment significantly reduced ileal thickness, collagen, and overall ECM content in SAMP1/YitFc mice. This was associated with a reduction in proliferative markers within the mesenchymal compartment. Nr4a1^-/- mice exposed to DSS exhibited increased colonic thickening and ECM content. Nr4a1^-/- myofibroblasts displayed enhanced TGF-β1-induced proliferation. Furthermore, Csn-B or 6-MP treatment was antiproliferative in Nr4a1^+/+ but not Nr4a1^-/- cells. Lastly, activating NR4A1 in human myofibroblasts reduced TGF-β1-induced collagen deposition and fibrosis-related gene expression. Our data suggest that NR4A1 can attenuate fibrotic processes in intestinal myofibroblasts and could provide a valuable clinical target to treat inflammation-associated intestinal fibrosis.NEW & NOTEWORTHY Fibrosis and increased muscle thickening contribute to stricture formation and intestinal obstruction, a complication that occurs in 30%-50% of patients with CD within 10 yr of disease onset. More than 50% of those who undergo surgery to remove the obstructed bowel will experience stricture recurrence. To date, there are no drug-based approaches approved to treat intestinal strictures. In the current submission, we identify NR4A1 as a novel target to treat inflammation-associated intestinal fibrosis.

Fibrillar biopolymer-based scaffolds to study macrophage-fibroblast crosstalk in wound repair

Controlled wound healing requires a temporal and spatial coordination of cellular activities within the surrounding extracellular matrix (ECM). Disruption of cell-cell and cell-matrix communication results in defective repair, like chronic or fibrotic wounds. Activities of macrophages and fibroblasts crucially contribute to the fate of closing wounds. To investigate the influence of the ECM as an active part controlling cellular behavior, coculture models based on fibrillar 3D biopolymers such as collagen have already been successfully used. With well-defined biochemical and biophysical properties such 3D scaffolds enable in vitro studies on cellular processes including infiltration and differentiation in an in vivo like microenvironment. Further, paracrine and autocrine signaling as well as modulation of soluble mediator transport inside the ECM can be modeled using fibrillar 3D scaffolds. Herein, we review the usage of these scaffolds in in vitro coculture models allowing in-depth studies on the crosstalk between macrophages and fibroblasts during different stages of cutaneous wound healing. A more accurate mimicry of the various processes of cellular crosstalk at the different stages of wound healing will contribute to a better understanding of the impact of biochemical and biophysical environmental parameters and help to develop further strategies against diseases such as fibrosis.

Understanding Fibroblast Behavior in 3D Biomaterials

Traditional monolayer culture fails to fully recapitulate the in vivo environment of connective tissue cells such as the fibroblast. When cultured on stiff two-dimensional (2D) plastic, fibroblasts become highly proliferative forming broad lamellipodia and stress fibers. Conversely, in different three-dimensional (3D) culture systems, fibroblasts have displayed a diverse array of features; from an "activated" phenotype like that observed in 2D cultures and by myofibroblasts, to a quiescent state that likely better represents in vivo fibroblasts at rest. Today, a plethora of microfabrication techniques have made 3D culture commonplace, for both tissue engineering purposes and in the study of basic biological interactions. However, establishing the in vivo mimetic credentials of different biomimetic materials is not always straightforward, particularly in the context of fibroblast responses. Fibroblast behavior is governed by the complex interplay of biological features such as integrin binding sites, material mechanical properties that influence cellular mechanotransduction, and microarchitectural features like pore and fiber size, as well as chemical cues. Furthermore, fibroblasts are a heterogeneous group of cells with specific phenotypic traits dependent on their tissue of origin. These features have made understanding the influence of biomaterials on fibroblast behavior a challenging task. In this study, we present a review of the strategies used to investigate fibroblast behavior with a focus on the material properties that influence fibroblast activation, a process that becomes pathological in fibrotic diseases and certain cancers.

Keratin-Alginate Sponges Support Healing of Partial-Thickness Burns

Deep partial-thickness burns damage most of the dermis and can cause severe pain, scarring, and mortality if left untreated. This study serves to evaluate the effectiveness of crosslinked keratin–alginate composite sponges as dermal substitutes for deep partial-thickness burns. Crosslinked keratin–alginate sponges were tested for the ability to support human dermal fibroblasts in vitro and to support the closure and healing of partial-thickness burn wounds in Sus scrofa pigs. Keratin–alginate composite sponges supported the enhanced proliferation of human dermal fibroblasts compared to alginate-only sponges and exhibited decreased contraction in vitro when compared to keratin only sponges. As dermal substitutes in vivo, the sponges supported the expression of keratin 14, alpha-smooth muscle actin, and collagen IV within wound sites, comparable to collagen sponges. Keratin–alginate composite sponges supported the regeneration of basement membranes in the wounds more than in collagen-treated wounds and non-grafted controls, suggesting the subsequent development of pathological scar tissues may be minimized. Results from this study indicate that crosslinked keratin–alginate sponges are suitable alternative dermal substitutes for clinical applications in wound healing and skin regeneration.

Key Roles of RGD-Recognizing Integrins During Cardiac Development, on Cardiac Cells, and After Myocardial Infarction

Cardiac cells interact with the extracellular matrix (ECM) proteins through integrin mechanoreceptors that control many cellular events such as cell survival, apoptosis, differentiation, migration, and proliferation. Integrins play a crucial role in cardiac development as well as in cardiac fibrosis and hypertrophy. Integrins recognize oligopeptides present on ECM proteins and are involved in three main types of interaction, namely with collagen, laminin, and the oligopeptide RGD (Arg-Gly-Asp) present on vitronectin and fibronectin proteins. To date, the specific role of integrins recognizing the RGD has not been addressed. In this review, we examine their role during cardiac development, their role on cardiac cells, and their upregulation during pathological processes such as heart fibrosis and hypertrophy. We also examine their role in regenerative and angiogenic processes after myocardial infarction (MI) in the peri-infarct area. Specific targeting of these integrins may be a way of controlling some of these pathological events and thereby improving medical outcomes.

Serum extracellular vesicles containing MIAT induces atrial fibrosis, inflammation and oxidative stress to promote atrial remodeling and atrial fibrillation via blockade of miR-485-5p-mediated CXCL10 inhibition

BACKGROUND

Atrial fibrillation (AF), a supraventricular arrhythmia that impairs cardiac function, is a main source of morbidity and mortality. Serum-derived extracellular vesicles (EVs) have been identified to carry potential biomarker or target for the diagnosis and treatment of AF. We intended to dissect out the role of lncRNA MIAT enriched in serum-derived EVs in AF.

METHODS

MIAT expression was quantified in EVs isolated from serum samples of AF patients. Mouse and cell models of AF were developed after angiotensin II (Ang II) induction. Relationship between MIAT, miR-485-5p, and CXCL10 was identified. Ectopic expression and depletion assays were implemented in Ang II-treated mice or HL-1 cells, or those co-cultured with serum-derived EVs to explore the roles of EV-carried MIAT.

RESULTS

MIAT was upregulated in EVs from serum samples of AF patients. Further analysis indicated that MIAT enriched in serum-derived EVs promoted atrial fibrosis, inflammation and oxidative stress, and aggravated the atrial remodeling and resultant AF. Mechanistically, MIAT bound to miR-485-5p and weakened its inhibitory role on the target CXCL10, which was responsible for the role of serum-derived EV containing MIAT in cellular fibrosis, oxidative stress and inflammation, and atrial remodeling in vivo.

CONCLUSIONS

In conclusion, serum-derived EV containing MIAT facilitates atrial remodeling and exacerbates the AF by abolishing the miR-485-5p-mediated CXCL10 inhibition. This finding aids in the deeper understanding about the pathophysiology of AF.

Electronic Cigarette Exposure Enhances Lung Inflammatory and Fibrotic Responses in COPD Mice

Although a few studies show that the use of electronic nicotine delivery systems (ENDS) may ameliorate objective and subjective outcomes in COPD smokers who switched to electronic cigarettes, it is unclear whether e-cigarette exposure alters lung pathological features and inflammatory response in COPD. Here, we employed βENaC-overexpressing mice bearing COPD-like pulmonary abnormality, and exposed them to ENDS. We found that ENDS exposure aggravated airspace enlargement and mucus production in βENaC-overexpressing mice, which was associated with increased MMP12 and Muc5ac, respectively. ENDS exposure to mice significantly increased the numbers of macrophages, particularly in M2 macrophages in bronchoalveolar lavage (BAL) fluid, despite ENDS did not induce M2 macrophage polarization in a cultured murine macrophage cell line (RAW264.7). There were no changes in neutrophils in BAL fluid by ENDS exposure. Multiple cytokine productions were increased including M-CSF, IL-1rα, IL-10, and TGF-β1, in BAL fluid from mice when exposed to ENDS. The Sirius Red staining and hydroxyproline assay showed ENDS-exposed mice displayed enhanced fibrotic phenotypes compared to control mice. In conclusion, ENDS exposure enhances airspace enlargement, mucus secretion, and fibrogenesis in COPD mice. This is associated with increased MMP12, inflammatory responses, and M2 macrophage phenotype. This study provides pre-clinical data implicating that electronic cigarette exposure is not safe in COPD patients who want to replace traditional cigarettes with ENDS.

A Scarless Healing Tale: Comparing Homeostasis and Wound Healing of Oral Mucosa With Skin and Oesophagus

Epithelial tissues are the most rapidly dividing tissues in the body, holding a natural ability for renewal and regeneration. This ability is crucial for survival as epithelia are essential to provide the ultimate barrier against the external environment, protecting the underlying tissues. Tissue stem and progenitor cells are responsible for self-renewal and repair during homeostasis and following injury. Upon wounding, epithelial tissues undergo different phases of haemostasis, inflammation, proliferation and remodelling, often resulting in fibrosis and scarring. In this review, we explore the phenotypic differences between the skin, the oesophagus and the oral mucosa. We discuss the plasticity of these epithelial stem cells and contribution of different fibroblast subpopulations for tissue regeneration and wound healing. While these epithelial tissues share global mechanisms of stem cell behaviour for tissue renewal and regeneration, the oral mucosa is known for its outstanding healing potential with minimal scarring. We aim to provide an updated review of recent studies that combined cell therapy with bioengineering exporting the unique scarless properties of the oral mucosa to improve skin and oesophageal wound healing and to reduce fibrotic tissue formation. These advances open new avenues toward the ultimate goal of achieving scarless wound healing.

Fibroblasts: Origins, definitions, and functions in health and disease

Fibroblasts are diverse mesenchymal cells that participate in tissue homeostasis and disease by producing complex extracellular matrix and creating signaling niches through biophysical and biochemical cues. Transcriptionally and functionally heterogeneous across and within organs, fibroblasts encode regional positional information and maintain distinct cellular progeny. We summarize their development, lineages, functions, and contributions to fibrosis in four fibroblast-rich organs: skin, lung, skeletal muscle, and heart. We propose that fibroblasts are uniquely poised for tissue repair by easily reentering the cell cycle and exhibiting a reversible plasticity in phenotype and cell fate. These properties, when activated aberrantly, drive fibrotic disorders in humans.

The functional cross talk between cancer cells and cancer associated fibroblasts from a cancer mechanics perspective

The function of biological tissues in health and disease is regulated at cellular level and is highly influenced by the physical microenvironment, through the interaction of forces between cells and ECM, which are perceived through mechanosensing pathways. In cancer, both chemical and physical signaling cascades and their interactions are involved during cell-cell and cell-ECM communications to meet requirements of tumor growth. Among stroma cells, cancer associated fibroblasts (CAFs) play key role in tumor growth and pave the way for cancer cells to initiate metastasis and invasion to other tissues, and without recruitment of CAFs, the process of cancer invasion is dysfunctional. This is through an intense chemical and physical cross talks with tumor cells, and interactive remodeling of ECM. During such interaction CAFs apply traction forces and depending on the mechanical properties, deform ECM and in return receive physical signals from the micromechanical environment. Such interaction leads to ECM remodeling by manipulating ECM structure and its mechanical properties. The results are in form of deposition of extra fibers, stiffening, rearrangement and reorganization of fibrous structure, and degradation which are due to a complex secretion and expression of different markers triggered by mechanosensing of tumor cells, specially CAFs. Such events define cancer progress and invasion of cancer cells. A systemic knowledge of chemical and physical factors provides a holistic view of how cancer process and enhances the current treatment methods to provide more diversity among targets that involves tumor cells and ECM structure.

Myofibroblast transcriptome indicates SFRP2hi fibroblast progenitors in systemic sclerosis skin

Skin and lung fibrosis in systemic sclerosis (SSc) is driven by myofibroblasts, alpha-smooth muscle actin expressing cells. The number of myofibroblasts in SSc skin correlates with the modified Rodnan skin score, the most widely used clinical measure of skin disease severity. Murine fibrosis models indicate that myofibroblasts can arise from a variety of different cell types, but their origin in SSc skin has remained uncertain. Utilizing single cell RNA-sequencing, we define different dermal fibroblast populations and transcriptome changes, comparing SSc to healthy dermal fibroblasts. Here, we show that SSc dermal myofibroblasts arise in two steps from an SFRP2^hi/DPP4-expressing progenitor fibroblast population. In the first step, SSc fibroblasts show globally upregulated expression of transcriptome markers, such as PRSS23 and THBS1. A subset of these cells shows markers indicating that they are proliferating. Only a fraction of SFRP2^hi SSc fibroblasts differentiate into myofibroblasts, as shown by expression of additional markers, SFRP4 and FNDC1. Bioinformatics analysis of the SSc fibroblast transcriptomes implicated upstream transcription factors, including FOSL2, RUNX1, STAT1, FOXP1, IRF7 and CREB3L1, as well as SMAD3, driving SSc myofibroblast differentiation.

Myofibroblasts drive fibrosis in systemic sclerosis (SSc), but the cellular progenitors are unknown. Utilizing single cell RNA-sequencing, the authors show that SSc dermal myofibroblasts arise in a two-step process from SFRP2/DPP4-expressing progenitors and implicate upstream transcription factors.

Impact of isolation method on cellular activation and presence of specific tendon cell subpopulations during in vitro culture

Tendon injuries are common and heal poorly, due in part to a lack of understanding of fundamental tendon cell biology. A major impediment to the study of tendon cells is the absence of robust, well-characterized in vitro models. Unlike other tissue systems, current tendon cell models do not account for how differences in isolation methodology may affect the activation state of tendon cells or the presence of various tendon cell subpopulations. The objective of this study was to characterize how common isolation methods affect the behavior, fate, and lineage composition of tendon cell cultures. Tendon cells isolated by explant exhibited reduced proliferative capacity, decreased expression of tendon marker genes, and increased expression of genes associated with fibroblast activation compared to digested cells. Consistently, explanted cells also displayed an increased propensity to differentiate to myofibroblasts compared to digested cells. Explanted cultures from multiple different tendons were substantially enriched for the presence of scleraxis-lineage (Scx-lin+) cells compared to digested cultures, while the overall percentage of S100a4-lineage (S100a4-lin+) cells was dependent on both isolation method and tendon of origin. Neither isolation methods preserved the ratios of Scx-lin+ or S100a4-lin+ to non-lineage cells seen in tendons in vivo. Combined, these data indicate that further refinement of in vitro cultures models is required in order to more accurately understand the effects of various stimuli on tendon cell behavior. Statement of clinical significance: The development of informed in vitro tendon cell models will facilitate enhanced screening of potential therapeutic candidates to improve tendon healing.

Histatin 1 enhanced the speed and quality of wound healing through regulating the behaviour of fibroblast

Objectives

Histatin 1(Hst 1) has been proved to promote wound healing. However, there was no specific study on the regulation made by Hst 1 of fibroblasts in the process of wound healing. This research comprehensively studied the regulation of Hst 1 on the function of fibroblasts in the process of wound healing and preliminary mechanism about it.

Materials and methods

The full‐thickness skin wound model was made on the back of C57/BL6 mice. The wound healing, collagen deposition and fibroblast distribution were detected on days 3, 5 and 7 after injury. Fibroblast was cultured in vitro and stimulated with Hst 1, and then, their biological characteristics and functions were detected.

Results

Histatin 1 can effectively promote wound healing, improve collagen deposition during and after healing and increase the number and function of fibroblasts. After healing, the mechanical properties of the skin also improved. In vitro, the migration ability of fibroblasts stimulated by Hst 1 was significantly improved, and the fibroblasts transformed more into myofibroblasts, which improved the function of contraction and collagen secretion. In fibroblasts, mTOR signalling pathway can be activated by Hst 1.

Conclusions

Histatin 1 can accelerate wound healing and improve the mechanical properties of healed skin by promoting the function of fibroblasts. The intermolecular mechanisms need to be further studied, and this study provides a direction about mTOR signalling pathway.

Hypertrophic Scarring: Current Knowledge of Predisposing Factors, Cellular and Molecular Mechanisms

Hypertrophic scarring (HSc) is an age-old problem that still affects millions of people physically, psychologically, and economically. Despite advances in surgical techniques and wound care, prevention and treatment of HSc remains a challenge. Elucidation of factors involved in the development of this common fibroproliferative disorder is crucial for further progress in preventive and/or therapeutic measures. Our knowledge about pathophysiology of HSc at the cellular and molecular level has grown considerably in recent decades. In this article, current knowledge of predisposing factors and the cellular and molecular mechanisms of HSc has been reviewed.

The Mechanism of CD8+ T Cells for Reducing Myofibroblasts Accumulation during Renal Fibrosis

Renal fibrosis is a hallmark of chronic kidney disease (CKD) and a common manifestation of end-stage renal disease that is associated with multiple types of renal insults and functional loss of the kidney. Unresolved renal inflammation triggers fibrotic processes by promoting the activation and expansion of extracellular matrix-producing fibroblasts and myofibroblasts. Growing evidence now indicates that diverse T cells and macrophage subpopulations play central roles in the inflammatory microenvironment and fibrotic process. The present review aims to elucidate the role of CD8⁺ T cells in renal fibrosis, and identify its possible mechanisms in the inflammatory microenvironment.

Vascular Ehlers-Danlos Syndrome: Treatment of a Complex Abdominal Wound with Vitamin C and Mesenchymal Stromal Cells

ABSTRACT

Vascular Ehlers-Danlos syndrome (EDSv) can present with life-threatening surgical complications. The article describes the case of a patient with EDSv who developed total abdominal wound dehiscence and multiple enterocutaneous fistulas. Treatment with IV allogeneic mesenchymal stromal cells (MSCs) and high-dose vitamin C was trialed with success. Near-complete wound healing of the abdominal dehiscence with a 94% reduction in the size of the wound bed occurred. Maturation of the enterocutaneous fistulas also ensued.There is no current consensus on the management of large cutaneous wounds in EDSv. This article discusses the pathophysiology of wound healing with regard to nutrition requirements and growth factors with special reference to collagen deficits in EDSv. A potential therapy with IV vitamin C supplementation and MSCs is proposed following the patient's positive outcome. Medium-dose MSCs and high-dose IV vitamin C may offer significant benefits to complex and problematic wounds.

Lineage tracing of Foxd1-expressing embryonic progenitors to assess the role of divergent embryonic lineages on adult dermal fibroblast function

Recent studies have highlighted the functional diversity of dermal fibroblast populations in health and disease, with part of this diversity linked to fibroblast lineage and embryonic origin. Fibroblasts derived from foxd1-expressing progenitors contribute to the myofibroblast populations present in lung and kidney fibrosis in mice but have not been investigated in the context of dermal wound repair. Using a Cre/Lox system to genetically track populations derived from foxd1-expressing progenitors, lineage-positive fibroblasts were identified as a subset of the dermal fibroblast population. During development, lineage-positive cells were most abundant within the dorsal embryonic tissues, contributing to the developing dermal fibroblast population, and remaining in this niche into adulthood. In adult mice, assessment of fibrosis-related gene expression in lineage-positive and lineage-negative populations isolated from wounded and unwounded dorsal skin was performed, identifying an enrichment of transcripts associated with matrix synthesis and remodeling in the lineage-positive populations. Using a novel excisional wound model, ventral skin healed with a greatly reduced frequency of foxd1 lineage-positive cells. This work supports that the embryonic origin of fibroblasts is an important predictor of fibroblast function, but also highlights that within disparate regions, fibroblasts of different lineages likely undergo convergent differentiation contributing to phenotypic similarities.

Mechanism of bone marrow mesenchymal stem cells secreting miR-26a exosomes affecting high glucose-induced skin fibroblasts function by regulating TLR4/NF-κB signaling

OBJECTIVE

The aim of this study was to investigate the molecular mechanism of human bone marrow mesenchymal stem cells (hMSCs) secreting miR-26a exosomes on the function of skin fibroblasts.

METHODS

Exosomes from hMSCs were extracted and identified by transmission electron microscopy, particle size was analyzed and protein markers were detected. Then, the exosomes were co-cultured with human skin fibroblasts (BJ). CCK-8, Annexin V/P and Transwell assays were used to detect the proliferation, apoptosis, and migration of BJ cells. In addition, the expressions of miR-26a, related proteins, and related inflammatory factors were detected by qRT-PCR, western blotting, and ELISA.

RESULTS

Compared with the high glucose group, the proliferation rate, migration rate, and the expression of α-SMA, bcl-2, TLR4, NF-κB, TNF-α, IL-6, IL- and IL-1 were significantly decreased in the high glucose + MSC-Exo-miR-26a mimics group, while the apoptosis rate and the expression of miR-26a, cleaved-caspase 3, cleaved-caspase 9 and Bax were significantly increased. The results of the high glucose + MSC-Exo-miR-26a inhibitor group were the opposite.

CONCLUSION

These results suggest that hMSCs cells secreting miR-26a exosomes inhibited the proliferation, migration, and transdifferentiation of high glucose-induced BJ cells, and promoted cell apoptosis, which may be related to the TLR4/NF-κB signaling pathway.

Immune cells in lens injury repair and fibrosis

Immune cells, both tissue resident immune cells and those immune cells recruited in response to wounding or degenerative conditions, are essential to both the maintenance and restoration of homeostasis in most tissues. These cells are typically provided to tissues by their closely associated vasculatures. However, the lens, like many of the tissues in the eye, are considered immune privileged sites because they have no associated vasculature. Such absence of immune cells was thought to protect the lens from inflammatory responses that would bring with them the danger of causing vision impairing opacities. However, it has now been shown, as occurs in other immune privileged sites in the eye, that novel pathways exist by which immune cells come to associate with the lens to protect it, maintain its homeostasis, and function in its regenerative repair. Here we review the discoveries that have revealed there are both innate and adaptive immune system responses to lens, and that, like most other tissues, the lens harbors a population of resident immune cells, which are the sentinels of danger or injury to a tissue. While resident and recruited immune cells are essential elements of lens homeostasis and repair, they also become the agents of disease, particularly as progenitors of pro-fibrogenic myofibroblasts. There still remains much to learn about the function of lens-associated immune cells in protection, repair and disease, the knowledge of which will provide new tools for maintaining the core functions of the lens in the visual system.

Osteogenic differentiation of human mesenchymal stromal cells and fibroblasts differs depending on tissue origin and replicative senescence

The need for an autologous cell source for bone tissue engineering and medical applications has led researchers to explore multipotent mesenchymal stromal cells (MSC), which show stem cell plasticity, in various human tissues. However, MSC with different tissue origins vary in their biological properties and their capability for osteogenic differentiation. Furthermore, MSC-based therapies require large-scale ex vivo expansion, accompanied by cell type-specific replicative senescence, which affects osteogenic differentiation. To elucidate cell type-specific differences in the osteogenic differentiation potential and replicative senescence, we analysed the impact of BMP and TGF-β signaling in adipose-derived stromal cells (ASC), fibroblasts (FB), and dental pulp stromal cells (DSC). We used inhibitors of BMP and TGF-β signaling, such as SB431542, dorsomorphin and/or a supplemental addition of BMP-2. The expression of high-affinity binding receptors for BMP-2 and calcium deposition with alizarin red S were evaluated to assess osteogenic differentiation potential. Our study demonstrated that TGF-β signaling inhibits osteogenic differentiation of ASC, DSC and FB in the early cell culture passages. Moreover, DSC had the best osteogenic differentiation potential and an activation of BMP signaling with BMP-2 could further enhance this capacity. This phenomenon is likely due to an increased expression of activin receptor-like kinase-3 and -6. However, in DSC with replicative senescence (in cell culture passage 10), osteogenic differentiation sharply decreased, and the simultaneous use of BMP-2 and SB431542 did not result in further improvement of this process. In comparison, ASC retain a similar osteogenic differentiation potential regardless of whether they were in the early (cell culture passage 3) or later (cell culture passage 10) stages. Our study elucidated that ASC, DSC, and FB vary functionally in their osteogenic differentiation, depending on their tissue origin and replicative senescence. Therefore, our study provides important insights for cell-based therapies to optimize prospective bone tissue engineering strategies.

Down-Regulation of a Profibrotic Transforming Growth Factor-β1/Cellular Communication Network Factor 2/Matrix Metalloprotease 9 Axis by Triamcinolone Improves Idiopathic Subglottic Stenosis

Idiopathic subglottic stenosis (iSGS) is a progressive fibrotic disease characterized by life-threatening airway narrowing. Although the molecular underpinnings are unknown, previous reports showing that subglottic serial intralesional steroid injections (SILSIs) improve clinical outcomes suggest a steroid-sensitive pathway in iSGS. Herein, a prospective study was conducted to determine the changes in profibrotic markers during SILSI to identify steroid-sensitive profibrotic drivers. Seven newly diagnosed patients with iSGS were recruited for SILSI. Subglottic biopsies before and after SILSI treatments were evaluated for histologic and molecular markers by confocal microscopy and RT-qPCR. At baseline, iSGS subglottises contained abundant vimentin-positive/α-smooth muscle actin-negative fibroblasts, intermingled with a matrix of fibronectin and types I and VI collagen. Transforming growth factor (TGF)-β1 was up-regulated primarily in glandular epithelium. Cellular communication network factor 2 (CCN2) was mainly up-regulated in stromal fibroblasts surrounding TGF-β1-positive glandular structures. SILSI improved iSGS by reducing fibroblast infiltration and increasing matrix remodeling. Mechanistically, SILSI counteracted the effects of TGF-β1 by inducing matrix metalloprotease 9 (MMP9) expression while repressing CCN2 expression, without affecting TGFβ1 levels. Treatment of primary iSGS-derived fibroblasts with TGF-β1 recapitulated aspects of the disease in vivo, demonstrating that the induction in CCN2 and repression of MMP9 are caused by changes in histone acetylation induced by TGF-β1. Triamcinolone counteracted the coregulation of these genes by impairing SMAD2/3 binding to promoter regions, and not through histone acetylation. In conclusion, this study shows that SILSI counteracts a dysregulated TGF-β1/CCN2/MMP9 axis involved in iSGS development.

A double-network polysaccharide-based composite hydrogel for skin wound healing

Effective wound dressings are of great significance in preventing infections and promoting wound healing. However, most existing hydrogel dressings have an inadequacy in either mechanical performance, biological activities, or versatilities. Here we presented a double-network cross-linked polysaccharide-based hydrogel composed of collagen peptide-functionalized carboxymethyl chitosan (CS) and oxidized methacrylate sodium alginate (SA). The hydrogel possessed interconnected porous morphologies, suitable swelling ratios, excellent mechanical properties, and favorable biocompatibility. Meanwhile, the in vivo studies using a mouse full-thickness skin defect model showed that the double-network CS/SA hydrogel significantly accelerated wound healing by regulating the inflammatory process, promoting collagen deposition, and improving vascularization. Therefore, the functionalized double-network hydrogel should be a potential candidate as wound dressings.

Myofibroblast progeny in wound biology and wound healing studies

Fibroblasts and myofibroblasts play a myriad of important roles in human tissue function, especially in wound repair and healing. Among all cells, fibroblasts are group of cells that decide the status of wound as they maintain tissue homeostasis. Currently, the increase in the deleterious effects of chronic wound and their morbidity rate has necessitated the need to understand the influence of fibroblasts and myofibroblasts, which chiefly originate locally from tissue-resident fibroblasts to address the same. Wound pathophysiology is complex, herein, we have discussed fibroblast and myofibroblast heterogeneity in skin and different organs by understanding the phenotypical and functional properties of each of its sub-populations in the process of wound healing. Recent advancements in fibroblast activation, differentiation to myofibroblasts, proliferation and migration are discussed in detail. Fibroblasts and myofibroblasts are key players in wound healing and wound remodelling, respectively, and their significance in wound repair is discussed. An increased understanding of their biology during wound healing also gives an opportunity to explore more of fibroblast and myofibroblast focused therapies to treat chronic wounds which are clinical challenges. In this regard, in the current review, we have described the different methods for isolation of primary fibroblasts and myofibroblasts from both animal models and humans, and their characterization. Additionally, we have also provided details on possible molecular targets for better understanding of prognosis, diagnosis and treatment of chronic wounds. Information will help both researchers and clinicians in providing molecular insight that enable them for effective chronic wound management. The knowledge of intimate dialogue between the fibroblast, sub-populations like, myofibroblast and their microenvironment, will serve useful in determining novel, efficient and specific therapeutic targets to treat pathological wound conditions.

Effect of Pig-Adipose-Derived Stem Cells' Conditioned Media on Skin Wound-Healing Characteristics In Vitro

The primary mechanism by which adipose-derived stem cells (ASCs) exert their reparative or regenerative potential relies predominantly on paracrine action. Secretory abilities of ASCs have been found to be amplified by hypoxia pre-conditioning. This study investigates the impact of hypoxia (1% O₂) on the secretome composition of pig ASCs (pASCs) and explores the effect of pASCs’ conditioned media (CM) on skin cell functions in vitro and the expression of markers attributed to wound healing. Exposure of pASCs to hypoxia increased levels of vascular endothelial growth factor (VEGF) in CM-Hyp compared to CM collected from the cells cultured in normoxia (CM-Nor). CM-Hyp promoted the migratory ability of pig keratinocytes (pKERs) and delayed migration of pig dermal fibroblasts (pDFs). Exposure of pKERs to either CM-Nor or CM-Hyp decreased the levels of pro-fibrotic indicators WNT10A and WNT11. Furthermore, CM-Hyp enhanced the expression of KRT14, the marker of the basal epidermis layer. In contrast, CM-Nor showed a stronger effect on pDFs manifested by increases in TGFB1, COL1A1, COL3A1, and FN1 mRNA expression. The formation of three-dimensional endothelial cell networks was improved in the presence of CM-Hyp. Overall, our results demonstrate that the paracrine activity of pASCs affects skin cells, and this property might be used to modulate wound healing.

TGF-β as a driver of fibrosis: physiological roles and therapeutic opportunities

Many chronic diseases are marked by fibrosis, which is defined by an abundance of activated fibroblasts and excessive deposition of extracellular matrix, resulting in loss of normal function of the affected organs. The initiation and progression of fibrosis are elaborated by pro-fibrotic cytokines, the most critical of which is transforming growth factor-β1 (TGF-β1). This review focuses on the fibrogenic roles of increased TGF-β activities and underlying signaling mechanisms in the activated fibroblast population and other cell types that contribute to progression of fibrosis. Insight into these roles and mechanisms of TGF-β as a universal driver of fibrosis has stimulated the development of therapeutic interventions to attenuate fibrosis progression, based on interference with TGF-β signaling. Their promise in preclinical and clinical settings will be discussed. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.