Transplanted fibroblasts prevents dysfunctional repair in a murine CXCR3-deficient scarring model

Evolution, Expression and Functional Analysis of CXCR3 in Neuronal and Cardiovascular Diseases: A Narrative Review

Chemokines form a sophisticated communication network wherein they maneuver the spatiotemporal migration of immune cells across a system. These chemical messengers are recognized by chemokine receptors, which can trigger a cascade of reactions upon binding to its respective ligand. CXC chemokine receptor 3 (CXCR3) is a transmembrane G protein-coupled receptor, which can selectively bind to CXCL9, CXCL10, and CXCL11. CXCR3 is predominantly expressed on immune cells, including activated T lymphocytes and natural killer cells. It thus plays a crucial role in immunological processes like homing of effector cells to infection sites and for pathogen clearance. Additionally, it is expressed on several cell types of the central nervous system and cardiovascular system, due to which it has been implicated in several central nervous system disorders, including Alzheimer's disease, multiple sclerosis, dengue viral disease, and glioblastoma, as well as cardiovascular diseases like atherosclerosis, Chronic Chagas cardiomyopathy, and hypertension. This review provides a narrative description of the evolution, structure, function, and expression of CXCR3 and its corresponding ligands in mammals and zebrafish and the association of CXCR3 receptors with cardiovascular and neuronal disorders. Unraveling the mechanisms underlying the connection of CXCR3 and disease could help researchers investigate the potential of CXCR3 as a biomarker for early diagnosis and as a therapeutic target for pharmacological intervention, along with developing robust zebrafish disease models.

CXCR3A promotes the secretion of the antifibrotic decoy receptor sIL-13Rα2 by pulmonary fibroblasts

CXC chemokine receptor 3 (CXCR3) A and its IFN-inducible ligands CXCL9 and CXCL10 regulate vascular remodeling and fibroblast motility. IL-13 is a profibrotic cytokine implicated in the pathogenesis of inflammatory and fibroproliferative conditions. Previous work from our laboratory has shown that CXCR3A is negatively regulated by IL-13 and is necessary for the basal regulation of the IL-13 receptor subunit IL-13Rα2. This study investigates the regulation of fibroblast phenotype, function, and downstream IL-13 signaling by CXCR3A in vitro. CXCR3A was overexpressed via transient transfection. CXCR3A^-/- lung fibroblasts were isolated for functional analysis. Additionally, the contribution of CXCR3A to tissue remodeling following acute lung injury was assessed in vivo with wild-type (WT) and CXCR3^-/- mice challenged with IL-13. CXCR3 and IL-13Rα2 displayed a reciprocal relationship after stimulation with either IL-13 or CXCR3 ligands. CXCR3A reduced expression of fibroblast activation makers, soluble collagen production, and proliferation. CXCR3A enhanced the basal expression of pERK1/2 while inducing IL-13-mediated downregulation of NF-κB-p65. CXCR3A^-/- pulmonary fibroblasts were increasingly proliferative and displayed reduced contractility and α-smooth muscle actin expression. IL-13 challenge regulated expression of the CXCR3 ligands and soluble IL-13Rα2 levels in lungs and bronchoalveolar lavage fluid (BALF) of WT mice; this response was absent in CXCR3^-/- mice. Alveolar macrophage accumulation and expression of genes involved in lung remodeling was increased in CXCR3^-/- mice. We conclude that CXCR3A is a central antifibrotic factor in pulmonary fibroblasts, limiting fibroblast activation and reducing extracellular matrix (ECM) production. Therefore, targeting of CXCR3A may be a novel approach to regulating fibroblast activity in lung fibrosis and remodeling.

Potential of Tissue-Engineered and Artificial Dermis Grafts for Fingertip Reconstruction

BACKGROUND

Management of skin and soft-tissue defects of the fingertips is functionally and aesthetically important, but controversial, especially when bones are exposed. Recent advances in wound healing technology allow the use of cells or biological dermis. The authors studied the clinical efficacy of tissue-engineered dermis grafts and artificial dermis grafts versus immediate reconstructive procedures, such as the reverse digital artery island flap, in treating bone-exposed fingertip defects.

METHODS

One hundred eighty-two patients with bone-exposed fingertip defects treated with tissue-engineered dermis grafts (n = 71), artificial dermis grafts (n = 23), or reverse digital artery island flaps (n = 88) were included in this retrospective cohort study. Surgical time, duration of hospitalization, total cost, success rate, healing time, sensory recovery, range of motion, scar quality, and patient satisfaction were compared.

RESULTS

No tissue-engineered or artificial dermis graft exhibited graft rejection or failure, whereas there was one partial loss and one total loss after reverse digital artery island flap surgery. Tissue-engineered dermis grafts were superior in scar quality, and artificial dermis grafts had shorter surgical times and lower surgical costs; both groups demonstrated superior results in postoperative range of motion and sensory recovery in two-point discrimination tests and shorter hospitalization, compared with the reverse digital artery island flap group. The reverse digital artery island flap had shorter complete closure time and less postoperative tingling sensation. There were no differences in overall patient satisfaction among the groups.

CONCLUSIONS

Tissue-engineered and artificial dermis grafts may be promising alternatives for fingertip reconstruction. In particular, tissue-engineered dermis grafts may deliver superior functional results, including recovery of sensory discomfort and aesthetic results in terms of scar quality over artificial dermis grafts.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Physicochemically Tuned Myofibroblasts for Wound Healing Strategy

Normal healing of skin wounds involves a complex interplay between many different cellular constituents, including keratinocytes, immune cells, fibroblasts, myofibroblasts, as well as extracellular matrices. Especially, fibroblasts play a critical role in regulating the immune response and matrix reconstruction by secreting many cytokines and matrix proteins. Myofibroblasts, which are differentiated form of fibroblasts, feature high cellular contractility and encourage the synthesis of matrix proteins to promote faster closure of the wounds. We focus on the functional characteristics of these myofibroblasts as the healing strategy for severe wounds where the surplus amount of matrix proteins could be beneficial for better regeneration. In this study, we first employed multiple physicochemical cues, namely topographical alignment, TGF-β1, and electrical field (EF), to induce differentiation of dermal fibroblasts into myofibroblasts, and to further activate the differentiated cells. We then used these cells in a mouse wound model to verify their potential as a transplantable substitute for the severe wound. Our results confirmed that physicochemically stimulated myofibroblasts promoted faster healing of the wound compared to the case with non-stimulated myofibroblasts through elevated matrix reconstruction in the mouse model. Conclusively, we propose the utilization of physicochemically tuned myofibroblasts as a novel strategy for promoting better healing of moderate to severe wounds.

The Pro-reparative Engine: Stem Cells Aid Healing by Dampening Inflammation

Purpose of Review

Stem cells have been proposed as sources for tissue replacement when healing does not occur. These cells could contribute directly to skin structures via differentiation, or via producing trophic factors that would 'educate' the micro-environment to encourage tissue repair. Studies in animals have supported both mechanisms, but translation to humans has been challenged by poor cell survival after transplantation. However, the improvement noted with even transient existence suggests another new possibility, that of suppressing the inflammatory response that limits regenerative healing. Herein, we will propose that this immunomodulatory aspect holds promise for promoting skin healing.

Recent Findings

We have found that stem cell transplantation into wounds can dampen both acute and chronic inflammation, leading to more regenerative-like healing and diminished scarring.

Summary

Wound healing could be improved by dampening inflammation both initially to allow for tissue replacement to proceed and late to reduce scarring.

The Role of CXCR3 and Its Chemokine Ligands in Skin Disease and Cancer

Chemokines and their receptors play an important role in the recruitment, activation and differentiation of immune cells. The chemokine receptor, CXCR3, and its ligands, CXCL9, CXCL10, and CXCL11 are key immune chemoattractants during interferon-induced inflammatory responses. Inflammation of the skin resulting from infections or autoimmune disease drives expression of CXCL9/10/11 and the subsequent recruitment of effector, CXCR3⁺ T cells from the circulation. The relative contributions of the different CXCR3 chemokines and the three variant isoforms of CXCR3 (CXCR3A, CXCR3B, CXCR3alt) to the inflammatory process in human skin requires further investigation. In skin cancers, the CXCR3 receptor can play a dual role whereby expression on tumor cells can lead to cancer metastasis to systemic sites while receptor expression on immune cells can frequently promote anti-tumor immune responses. This review will discuss the biology of CXCR3 and its associated ligands with particular emphasis on the skin during inflammation and carcinogenesis.

Certainties and uncertainties concerning the contribution of pericytes to the pathogenesis of systemic sclerosis

The role of pericytes in systemic sclerosis (SSc) is unclear because of the difficulty in phenotyping them. They are mainly distributed in the pre-capillary, capillary and post-capillary abluminal side of non-muscular micro-vessels, express platelet-derived growth factor receptors (PDGFRs), and preside over vascular integrity and regeneration. By establishing close contact with many endothelial cells, a single pericyte can regulate ion influx, mechanical stress, leukocyte diapedesis, and platelet activation. Moreover, under pathological conditions such as SSc, pericytes may acquire a contractile phenotype and respond to various stimuli, including endothelin, angiotensin II and reactive oxygen species. The pericytes of SSc patients share some molecular patterns with myofibroblasts or fibroblasts, including A disintegrin and metalloproteinase domain 12 (ADAM-12), α-smooth muscle actin (α-SMA), the extra domain A (ED-A) variant of fibronectin, and Thy-1. Following stimulation with PDGF-β or transforming growth factor-β (TGF-β), pericytes may acquire a myofibroblast phenotype, and produce extracellular matrix or indirectly promote fibroblast activation. They may also contribute to fibrosis by means of epigenetic regulation. The pericyte plasmalemma is particularly rich in caveolae containing caveolin-1, a deficit of which has been associated with defective vessel tone control and lung fibrosis in mice. Consequently, dysfunctional pericytes may underlie the microangiopathy and fibrosis observed in SSc patients. However, given its variability in biological behaviour and the lack of a pan-pericyte marker, the exact role of these cells in SSc warrants further investigation.

Multipotent stromal cells/mesenchymal stem cells and fibroblasts combine to minimize skin hypertrophic scarring

Background

Transplantation of mesenchymal stem cells (MSC) has been proposed to improve wound healing. However, as these cells only transiently survive in the implantation site, the mechanisms underlying this beneficial healing response are associated with restorative paracrine effects of MSC matricellular factors on resident stromal cells. However, this requires that the recipient has a robust reservoir of viable cells. Here, we examine the influence of MSCs on the behavior of cotransplanted fibroblasts, in a manner to provide augmented cellular reserve to debilitated individuals, specifically focusing on matrix remodeling following in-vivo wounding.

Methods

Using a Hylan-A dermal filler hydrogel containing collagen I and tenascin-C for delivery and increased survival of transplanted cells, we find that cotransplantation of MSCs with fibroblasts reduces scarring.

Results

Transplanted xenogeneic MSCs augmented fibroblast proliferation, migration, and extracellular matrix deposition critical for wound closure, and reduced inflammation following wounding. MSCs also corrected matrix remodeling by CXCR3-deficient fibroblasts which otherwise led to hypertrophic scarring. This effect was superior to MSC or fibroblast transplantation alone.

Conclusions

Taken together, these data suggest that MSCs, even if eventually rejected, transplanted with fibroblasts normalize matrix regeneration during healing. The current study provides insight into cellular therapies as a viable method for antifibrotic treatment and demonstrates that even transiently engrafted cells can have a long-term impact via matrix modulation and education of other tissue cells.

Theoretical and practical aspects of using fetal fibroblasts for skin regeneration

Cutaneous wounding in late-gestational fetal or postnatal humans results in scar formation without any skin appendages. Early or mid- gestational skin healing in humans is characterized by the absence of scaring in a process resembling regeneration. Tremendous cellular and molecular mechanisms contribute to this distinction, and fibroblasts play critical roles in scar or scarless wound healing. This review discussed the different repair mechanisms involved in wound healing of fibroblasts at different developmental stages and further confirmed that fetal fibroblast transplantation resulted in reduced scar healing in vivo. We also discussed the possible problem in fetal fibroblast transplantation for wound repair. We proposed the use of small molecules to improve the regenerative potential of repairing cells in the wound given that remodeling of the wound microenvironment into a regenerative microenvironment in adults might improve skin regeneration.

Improved Transplanted Stem Cell Survival in a Polymer Gel Supplemented With Tenascin C Accelerates Healing and Reduces Scarring of Murine Skin Wounds

Mesenchymal stem cells (MSCs) remain of great interest in regenerative medicine because of their ability to home to sites of injury, differentiate into a variety of relevant lineages, and modulate inflammation and angiogenesis through paracrine activity. Many studies have found that despite the promise of MSC therapy, cell survival upon implant is highly limited and greatly reduces the therapeutic utility of MSCs. The matrikine tenascin C, a protein expressed often at the edges of a healing wound, contains unique EGF-like repeats that are able to bind EGFR at low affinities and induce downstream prosurvival signaling without inducing receptor internalization. In this study, we utilized tenascin C in a collagen/GAG-based polymer (TPolymer) that has been shown to be beneficial for skin wound healing, incorporating human MSCs into the polymer prior to application to mouse punch biopsy wound beds. We found that the TPolymer was able to promote MSC survival for 21 days in vivo, leading to associated improvements in wound healing such as dermal maturation and collagen content. This was most marked in a model of hypertrophic scarring, in which the scar formation was limited. This approach also reduced the inflammatory response in the wound bed, limiting CD3e+ cell invasion by approximately 50% in the early wound-healing process, while increasing the numbers of endothelial cells during the first week of wound healing as well. Ultimately, this matrikine-based approach to improving MSC survival may be of great use across a variety of cell therapies utilizing matrices as delivery vehicles for cells.

Chemokines in Wound Healing and as Potential Therapeutic Targets for Reducing Cutaneous Scarring

Significance: Cutaneous scarring is an almost inevitable end point of adult human wound healing. It is associated with significant morbidity, both physical and psychological. Pathological scarring, including hypertrophic and keloid scars, can be particularly debilitating. Manipulation of the chemokine system may lead to effective therapies for problematic lesions. Recent Advances: Rapid advancement in the understanding of chemokines and their receptors has led to exciting developments in the world of therapeutics. Modulation of their function has led to clinically effective treatments for conditions as diverse as human immunodeficiency virus and inflammatory bowel disease. Potential methods of targeting chemokines include monoclonal antibodies, small-molecule antagonists, interference with glycosaminoglycan binding and the use of synthetic truncated chemokines. Early work has shown promising results on scar development and appearance when the chemokine system is manipulated. Critical Issues: Chemokines are implicated in all stages of wound healing leading to the development of a cutaneous scar. An understanding of entirely regenerative wound healing in the developing fetus and how the expression of chemokines and their receptors change during the transition to the adult phenotype is central to addressing pathological scarring in adults. Future Directions: As our understanding of chemokine/receptor interactions and scar formation evolves it has become apparent that effective therapies will need to mirror the complexities in these diverse biological processes. It is likely that sophisticated treatments that sequentially influence multiple ligand/receptor interactions throughout all stages of wound healing will be required to deliver viable treatment options.

Skin tissue repair: Matrix microenvironmental influences

The process of repair of wounded skin involves intricate orchestration not only between the epidermal and dermal compartments but also between the resident and immigrant cells and the local microenvironment. Only now are we beginning to appreciate the complex roles played by the matrix in directing the outcome of the repair processes, and how this impacts the signals from the various cells. Recent findings speak of dynamic and reciprocal interactions that occurs among the matrix, growth factors, and cells that underlies this integrated process. Further confounding this integration are the physiologic and pathologic situations that directly alter the matrix to impart at least part of the dysrepair that occurs. These topics will be discussed with a call for innovative model systems of direct relevance to the human situation.

Muscle ring finger-3 protects against diabetic cardiomyopathy induced by a high fat diet

BACKGROUND

The pathogenesis of diabetic cardiomyopathy (DCM) involves the enhanced activation of peroxisome proliferator activating receptor (PPAR) transcription factors, including the most prominent isoform in the heart, PPARα. In cancer cells and adipocytes, post-translational modification of PPARs have been identified, including ligand-dependent degradation of PPARs by specific ubiquitin ligases. However, the regulation of PPARs in cardiomyocytes and heart have not previously been identified. We recently identified that muscle ring finger-1 (MuRF1) and MuRF2 differentially inhibit PPAR activities by mono-ubiquitination, leading to the hypothesis that MuRF3 may regulate PPAR activity in vivo to regulate DCM.

METHODS

MuRF3-/- mice were challenged with 26 weeks 60% high fat diet to induce insulin resistance and DCM. Conscious echocardiography, blood glucose, tissue triglyceride, glycogen levels, immunoblot analysis of intracellular signaling, heart and skeletal muscle morphometrics, and PPARα, PPARβ, and PPARγ1 activities were assayed.

RESULTS

MuRF3-/- mice exhibited a premature systolic heart failure by 6 weeks high fat diet (vs. 12 weeks in MuRF3+/+). MuRF3-/- mice weighed significantly less than sibling-matched wildtype mice after 26 weeks HFD. These differences may be largely due to resistance to fat accumulation, as MRI analysis revealed MuRF3-/- mice had significantly less fat mass, but not lean body mass. In vitro ubiquitination assays identified MuRF3 mono-ubiquitinated PPARα and PPARγ1, but not PPARβ.

CONCLUSIONS

These findings suggest that MuRF3 helps stabilize cardiac PPARα and PPARγ1 in vivo to support resistance to the development of DCM. MuRF3 also plays an unexpected role in regulating fat storage despite being found only in striated muscle.

Skin wound healing and scarring: fetal wounds and regenerative restitution

The adverse physiological and psychological effects of scars formation after healing of wounds are broad and a major medical problem for patients. In utero, fetal wounds heal in a regenerative manner, though the mechanisms are unknown. Differences in fetal scarless regeneration and adult repair can provide key insight into reduction of scarring therapy. Understanding the cellular and extracellular matrix alterations in excessive adult scarring in comparison to fetal scarless healing may have important implications. Herein, we propose that matrix can be controlled via cellular therapy to resemble a fetal-like matrix that will result in reduced scarring.

Cell therapy for wound healing

In covering wounds, efforts should include utilization of the safest and least invasive methods with goals of achieving optimal functional and cosmetic outcome. The recent development of advanced wound healing technology has triggered the use of cells to improve wound healing conditions. The purpose of this review is to provide information on clinically available cell-based treatment options for healing of acute and chronic wounds. Compared with a variety of conventional methods, such as skin grafts and local flaps, the cell therapy technique is simple, less time-consuming, and reduces the surgical burden for patients in the repair of acute wounds. Cell therapy has also been developed for chronic wound healing. By transplanting cells with an excellent wound healing capacity profile to chronic wounds, in which wound healing cannot be achieved successfully, attempts are made to convert the wound bed into the environment where maximum wound healing can be achieved. Fibroblasts, keratinocytes, adipose-derived stromal vascular fraction cells, bone marrow stem cells, and platelets have been used for wound healing in clinical practice. Some formulations are commercially available. To establish the cell therapy as a standard treatment, however, further research is needed.

Role of endothelial nitric oxide synthase and vagal activity in the endothelial protection of atorvastatin in ischemia/reperfusion injury

Vascular endothelial dysfunction plays a pivotal role in the development and maintenance of ischemia/reperfusion (I/R) injury. Statins, developed as lipid-lowering drugs, partially restore vagal activity and exhibit pleiotropic effects. This study was aimed at determining the effect of atorvastatin (ATV) on endothelial dysfunction in peripheral resistance arteries after I/R injury. After pretreatment with ATV (10 mg·kg·d) or its vehicle for 3 days, the superior mesenteric artery was occluded for 60 minutes and reperfusion for 90 minutes or the rats were anesthetized without being subjected to ischemia. In the ATV-treated I/R group, the increased contractions to KCl and 5-hydroxytryptamine induced by I/R were ameliorated, and attenuated endothelium-dependent relaxations to acetylcholine (ACh) were normalized. The restored relaxation to ACh was abolished by N-nitro-L-arginine methyl ester. ATV prevented the structural damage of vascular endothelial cells. Furthermore, the activities of phosphatidylinositol-3-kinase, Akt, and endothelial nitric oxide synthase were elevated in mesenteric arteries after ATV treatment. In addition, I/R-induced increment of endothelial cells apoptosis was also attenuated by ATV. Intriguingly, ATV also increased baroreflex sensitivity and serum ACh content after I/R. In conclusion, the endothelial protective effect of ATV in peripheral arteries is associated with the activated phosphatidylinositol-3-kinase/Akt/endothelial nitric oxide synthase pathway and restored vagal activity.

Chemokines and Their Receptors Are Key Players in the Orchestra That Regulates Wound Healing

SIGNIFICANCE

Normal wound healing progresses through a series of overlapping phases, all of which are coordinated and regulated by a variety of molecules, including chemokines. Because these regulatory molecules play roles during the various stages of healing, alterations in their presence or function can lead to dysregulation of the wound-healing process, potentially leading to the development of chronic, nonhealing wounds.

RECENT ADVANCES

A discovery that chemokines participate in a variety of disease conditions has propelled the study of these proteins to a level that potentially could lead to new avenues to treat disease. Their small size, exposed termini, and the fact that their only modifications are two disulfide bonds make them excellent targets for manipulation. In addition, because they bind to G-protein-coupled receptors (GPCRs), they are highly amenable to pharmacological modulation.

CRITICAL ISSUES

Chemokines are multifunctional, and in many situations, their functions are highly dependent on the microenvironment. Moreover, each specific chemokine can bind to several GPCRs to stimulate the function, and both can function as monomers, homodimers, heterodimers, and even oligomers. Activation of one receptor by any single chemokine can lead to desensitization of other chemokine receptors, or even other GPCRs in the same cell, with implications for how these proteins or their receptors could be used to manipulate function.

FUTURE DIRECTIONS

Investment in better understanding of the functions of chemokines and their receptors in a local context can reveal new ways for therapeutic intervention. Understanding how different chemokines can activate the same receptor and vice versa could identify new possibilities for drug development based on their heterotypic interactions.

The matrikine tenascin-C protects multipotential stromal cells/mesenchymal stem cells from death cytokines such as FasL

Multipotential stromal cells/mesenchymal stem cells (MSCs) are attractive candidates for regenerative therapy due to the ability of these cells to differentiate and positively influence neighboring cells. However, on implantation for wound reconstruction, these cells are lost as they are challenged by nonspecific inflammation signals generated in the wound environment and in response to any implanted foreign body. We have previously shown that sustained and surface-restricted epidermal growth factor receptor (EGFR) signaling by a tethered form of its prototypal ligand EGF enhances survival of MSC in the presence of death cytokines such as FasL, serum deprivation, and low oxygen in vitro. This was proposed to be due to the plasma membrane restriction of EGFR signaling. Interestingly, during wound repair, an extracellular matrix (ECM) component Tenascin-C (TNC) containing EGF-like repeats (EGFL) and fibronectin-like repeats (FNL) is upregulated. A few of the 14 EGFL on each of the 6 arms, especially the 14th, bind as low-affinity/high-avidity ligands to EGFR causing sustained surface-restricted EGFR signaling. We queried whether signaling by this physiologically relevant EGFR matrikine also protects MSCs from FasL-induced death. MSCs grown on TNC and Collagen I (as TNC by itself is antiadhesive) displayed a survival advantage in the presence of FasL. TNC neither sequestered nor neutralized FasL; rather, the effects of survival were via cell signaling. This survival was dependent on TNC activating EGFR and downstream pathways of Erk and Akt through EGFL; to a much lesser extent, the FNL of TNC also contributed to survival. Taken together, these results suggest that providing MSCs with a nonimmunogenic naturally occurring ECM moiety such as TNC enhances their survival in the presence of death factors, and this advantage occurs via signaling through EGFR primarily and integrins only to a minor extent. This matrix component is proposed to supplement MSC delivery on the scaffolds to provide a survival advantage against death upon in vivo implantation.