Recruitment Of Fibroblasts Research Articles

Evaluating Mouse Fibroblast Interaction with Implant Surfaces in a 3D Microenvironment

Previous studies assessing fibroblast interactions with implants have mainly relied on measurements such as cell migration, gene expression, and cell adhesion. For these studies, testing cellular behavior at the implant surface was done by imaging the cell-implant interface using standard microscopy techniques in 2D tissue culture dishes. The true behavior of cells relative to the implant can best be assessed in a more physiologic 3D microenvironment. The embedding of the implant disks in 3D collagen gels was standardized with labeled fibroblasts to allow the imaging of fibroblast morphology and behavior when proximal to or binding to the implant disks. This allowed comparison of the behavior of laser-microgrooved and machined implant disk surfaces quantitatively in an in vitro 3D microenvironment. This in vitro imaging assay revealed for the first time in a 3D microenvironment setting the statistically significant impact laser-microgrooved disk surfaces have on both cell adherence and recruitment of cells in proximity to the disk. It also allowed visualization of membrane protrusivity and cytoskeletal organization in cells adherent to the implant disk. This assay provides a simple and effective way of observing cell behavior on and around the implant disk surface in a more physiologic 3D setting. Within the limits of this study, it revealed that the laser-microgrooved implant surface demonstrates significant superiority in fibroblast recruitment and binding in a 3D microenvironment.

Dermal extracellular matrix response to facetem implant: a randomised controlled experimental study

Background. A leading concept in modern regenerative medicine is the perspective of using own body resources to remodel organs and tissues via the formation of “living scaffold”. A pivotal role in the formation of dermal scaffold is played by fibroblasts that produce extracellular matrix (ECM).Aim. A study of the fibroblast activation mechanism mediating synthesis of the dermal ECM fibrillar component under the Facetem filler administration.Methods. The experimental trial was conducted in Wistar male rats (72 animals). Animals had 0.05 mL Facetem (Korea) injections subdermally. The filler is a calcium-containing product featuring gradual degradation delivered through structural microspheric properties of the Lattice-pore technology. Biological material was sampled at weeks 1 and 2 of months 1, 2, 3 and 5. Tissues were paraffin-embedded in standard histological assays and stained with Mallory’s trichrome, Picrosirius red in polarisation microscopy and immunohistochemistry with collagen types I, III and elastin antibodies (Abcam).Results. Collagen distribution in dermis and the filling zone suggests that collagen production occurs by week 2 of the Facetem filler placement followed by an increase in synthesised matrix volume to 4.39 ± 0.7 for collagen type I and 3.9 ± 0.2 for collagen type III (p < 0.05). The synthetic activity of fi broblasts reduces by month 3, albeit with collagen production remaining above control even by the end of month 5. Elastin synthesis also initiates by week 2 of the filler injection in dermis and grows by month 3.Conclusion. The presence of Facetem filler triggers a foreign body inflammatory response in dermis. This multifactorial process initiates with protein adsorption proceeding to dermal cell recruitment and modulation of fibroblasts and macrophages. Activation of these cell types induces neocollagenesis entailing the extracellular matrix synthesis and expansion in dermis.

Bidirectional epithelial–mesenchymal crosstalk provides self-sustaining profibrotic signals in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is the prototypic progressive fibrotic lung disease with a median survival of 2 to 4 years. Injury to and/or dysfunction of the alveolar epithelium is strongly implicated in IPF disease initiation, but the factors that determine whether fibrosis progresses rather than normal tissue repair occurs remain poorly understood. We previously demonstrated that zinc finger E-box-binding homeobox 1–mediated epithelial–mesenchymal transition in human alveolar epithelial type II (ATII) cells augments transforming growth factor-β–induced profibrogenic responses in underlying lung fibroblasts via paracrine signaling. Here, we investigated bidirectional epithelial–mesenchymal crosstalk and its potential to drive fibrosis progression. RNA-Seq of lung fibroblasts exposed to conditioned media from ATII cells undergoing RAS-induced epithelial–mesenchymal transition identified many differentially expressed genes including those involved in cell migration and extracellular matrix regulation. We confirmed that paracrine signaling between RAS-activated ATII cells and fibroblasts augmented fibroblast recruitment and demonstrated that this involved a zinc finger E-box-binding homeobox 1–tissue plasminogen activator axis. In a reciprocal fashion, paracrine signaling from transforming growth factor-β–activated lung fibroblasts or IPF fibroblasts induced RAS activation in ATII cells, at least partially through the secreted protein acidic and rich in cysteine, which may signal via the epithelial growth factor receptor via epithelial growth factor–like repeats. Together, these data identify that aberrant bidirectional epithelial–mesenchymal crosstalk in IPF drives a chronic feedback loop that maintains a wound-healing phenotype and provides self-sustaining profibrotic signals.

Development of artificial blood vessels made of new materials, used for vascular access in renal dialysis

It can take many years to find a matched kidney donor and, in some cases, a matched donor is never found. Dialysis machines and methods of accessing a patient's cardiovascular system mean patients can live well whilst waiting for a transplant. Patients must undergo one of two surgical procedures before their first haemodialysis; receiving either an arteriovenous fistula or an arteriovenous graft, which join the artery to the vein and facilitate the transfer of blood from body to machine. If a graft is needed, an operation to insert a polytetrafluoroethylene (PTFE) based device is required but complications can arise in the form of blockages. Denan Jin, Department of Innovative Medicine, Osaka Medical and Pharmaceutical University, Japan, has spent years conducting research on the issues related to PTFE device blockage. He worked with his mentor Professor Mizuo Myazaki before his retirement and his colleague Professor Shinji Takai, and these collaborations led to understanding of the major causes of these blockages. Jin and his team are working to develop means to increase the longevity of PTFE grafts. The researchers have discovered two key mechanisms through which the grafts become blocked, which has led to the identification of two possible routes for preventing blockages. These relate to fibroblasts and the researchers have also identified the enzyme chymase as a key intermediate in the process of fibroblast recruitment. Jin and the team are proposing the use of an alternative to PTFE and the development of an effective chymase inhibitor to reduce the recruitment of fibroblasts to the graft site.

Comparison of curcumin and methylprednisolone in the prevention of epidural fibrosis after spinal surgery: An experimental study

We aimed to compare the effectiveness of curcumin, which has been shown to inhibit cell migration and proliferation, with that of methylprednisolone, which has been shown to have a similar mechanism of action to that of curcumin and to delay tissue repair and wound healing, in the prevention of epidural fibrosis in an experimental laminectomy model in rats. The experiment was conducted with 40 male Wistar rats weighing 250-300 g which were divided into four groups. Laminectomy was performed from L1 to L4 in all groups. Curcumin and methylprednisolone were applied to the other two groups except the control and DMSO groups. The vertebral colon was excised en bloc and each section was examined for epidural fibrosis formation under a light microscope to evaluate histologically using the grading system. Results: The statistical analyses indicated that the treatment groups had a significant effect on the histological grades of epidural fibrosis in rats compared to the control group. Curcumin, derived from the rhizome (Rhizoma Curcumae) of turmeric (Curcuma longa) was found to show a significant effect in the prevention of epidural fibrosis formation with its potent antioxidant and anti-inflammatory properties and by inhibiting further recruitment of fibroblasts to the laminectomy area. In the present study, both histological examination and statistical analyses indicated that the administration of curcumin led to a remarkable reduction in epidural fibrosis after laminectomy.

Biological testing of chitosan-collagen-based porous scaffolds loaded with PLGA/Triamcinolone microspheres for ameliorating endoscopic dissection-related stenosis in oesophagus.

ObjectivesEndoscopic submucosal dissection (ESD), a preferential approach for early oesophageal neoplasms, inevitably results in oesophageal strictures in patients. Clinical use of glucocorticoids through submucosal injection is beneficial for inhibiting oesophageal stricture following injury; however, it also has limitations, such as dose loss and perforation. Hence, alternatives to glucocorticoid therapy should be developed.MethodsA novel porous composite scaffold, ChCo‐TAMS, composed of chitosan, collagen‐I and triamcinolone acetonide (TA) loaded into poly (lactic‐co‐glycolic) acid (PLGA) microspheres (TAMS), was successfully constructed and subjected to biological testing to ameliorate oesophageal ESD‐related stenosis.ResultsThe synthesized biomaterials displayed unique properties in inhibiting the activation of macrophages, chemokine‐mediated cell recruitment and fibrogenesis of fibroblasts. Further application of the scaffolds in the rat dermal defect and porcine oesophageal ESD model showed that these novel scaffolds played a robust role in inhibiting wound contracture and oesophageal ESD strictures.ConclusionsThe developed composite scaffolds provide a promising clinical medical device for the prevention of post‐operative oesophageal stricture.

Method for Investigating Fibroblast Durotaxis.

Durotaxis is the phenomena of directed cell migration driven by gradients of extracellular matrix stiffness. Durotaxis has been recently involved in the development of fibrosis by promoting the recruitment of pathological fibroblasts to areas of established fibrosis, thus amplifying the fibrotic response. Here, we describe the fabrication of mechanically patterned hydrogels that can be used to investigate molecular mechanisms controlling durotaxis of fibroblasts and other cells with mechanosensing properties. This method effectively creates a stiffness gradient of 275Pa/μm, mimicking the natural spatial stiffness variations we observed in fibrotic tissues from mouse models of fibrosis and human fibrotic diseases.

Therapeutic Potential of Exosomes in Pulmonary Fibrosis.

Pulmonary fibrosis is closely associated with the recruitment of fibroblasts from capillary vessels with damaged endothelial cells, the epithelial mesenchymal transition (EMT) of type II alveolar epithelial cells, and the transformation of fibroblasts to myofibroblasts. Recent studies suggest that EMT is a key factor in the pathogenesis of pulmonary fibrosis, as the disruption of EMT-related effector molecules can inhibit the occurrence and development of PF. With the numerous advancements made in molecular biology in recent years, researchers have discovered that exosomes and their cargos, such as miRNAs, lncRNAs, and proteins, can promote or inhibit the EMT, modulate the transformation of fibroblasts into myofibroblasts, contribute to the proliferation of fibroblasts and promote immunoregulatory and mitochondrial damage during pulmonary fibrosis. Exosomes are key factors regulating the differentiation of bone marrow mesenchymal stem cells (BMSCs) into myofibroblasts. Interestingly, exosomes derived from BMSCs under pathological and physiological conditions may promote or inhibit the EMT of type II alveolar epithelial cells and the transformation of fibroblasts into myofibroblasts to regulate pulmonary fibrosis. Thus, exosomes may become a new direction in the study of drugs for the treatment of pulmonary fibrosis.

Biological efficacy of perpendicular type-I collagen protruded from TiO2-nanotubes

The aim of this study was to evaluate the biological efficacy of a unique perpendicular protrusion of type-I collagen (Col-I) from TiO2 nanotubes (NT-EPF surface). We hypothesized that the NT-EPF surface would play bifunctional roles in stimulating platelet-mediated fibroblast recruitment and anchoring fibroblast-derived Col-I to form a perpendicular collagen assembly, mimicking the connective tissue attachment around natural teeth for the long-term maintenance of dental implants. Ti surface modification was accomplished in two steps. First, TiO2 nanotubes (NT) array was fabricated via anodization. Diameters and depths of NTs were controlled by applied voltage and duration. Subsequently, an electrophoretic fusion (EPF) method was applied to fuse Col-I into nanotube arrays in a perpendicular fashion. Surface wettability was assessed by contact angle measurement. The bioactivity of modified TiO2 surfaces was evaluated in terms of NIH3T3 fibroblast attachment, platelet activation, and collagen extension. Early attachment, aggregation, and activation of platelets as well as release of platelet-related growth factors were demonstrated on NT-EPF surfaces. Platelet-mediated NIH3T3 cells migration toward NT-EPF was significantly increased and the attached cells showed a typical fibrous morphology with elongated spindle shape. A direct linkage between pseudopod-like processes of fibroblasts to NT-EPF surfaces was observed. Furthermore, the engineered EPF collagen protrusion linked with cell-derived collagen in a perpendicular fashion. Within the limitation of this in vitro study, the TiO2 nanotube with perpendicular Col-I surface (NT-EPF) promoted better cell attachment, induced a strong platelet activation which suggested the ability to create a more robust soft tissue seal.

Complement activation links inflammation to dental tissue regeneration.

Complement is an efficient plasma immune surveillance system. It initiates inflammation by inducing vascular modifications and attracting immune cells expressing Complement receptors. Investigating Complement receptors in non-immune cells pointed out Complement implication in the regeneration of tissue such as liver, skin, or bone. This review will shed the light on Complement implication in the initial steps of dental tissue regeneration. Review of literature was conducted on Complement local expression and implication in oral tissue regeneration in vivo and in vitro. Recent data reported expression of Complement receptors and soluble proteins in dental tissues. Cultured pulp fibroblasts secrete all Complement components. Complement C3b and MAC have been shown to control bacteria growth in the dental pulp while C3a and C5a are involved in the initial steps of pulp regeneration. Indeed, C3a induces pulp stem cell/fibroblast proliferation, and fibroblast recruitment, while C5a induces neurite growth, guides stem cell recruitment, and odontoblastic differentiation. Similarly, cultured periodontal ligament cells produce C5a which induces bone marrow mesenchymal stem cell recruitment. Overall, this review highlights that local Complement synthesis in dental tissues plays a major role, not only in eliminating bacteria but also in the initial steps of dental tissue regeneration, thus providing a link between dental tissue inflammation and regeneration. Complement provides an explanation for understanding why inflammation preceeds regeneration. This may also provide a biological rational for understanding the reported success conservative management of mature permanent teeth with carious pulp exposure.

Periostin and matrix stiffness combine to regulate myofibroblast differentiation and fibronectin synthesis during palatal healing

Although the matricellular protein periostin is prominently upregulated in skin and gingival healing, it plays contrasting roles in myofibroblast differentiation and matrix synthesis respectively. Palatal healing is associated with scarring that can alter or restrict maxilla growth, but the expression pattern and contribution of periostin in palatal healing is unknown. Using periostin-knockout (Postn−/−) and wild-type (WT) mice, the contribution of periostin to palatal healing was investigated through 1.5 mm full-thickness excisional wounds in the hard palate. In WT mice, periostin was upregulated 6 days post-wounding, with mRNA levels peaking at day 12. Genetic deletion of periostin significantly reduced wound closure rates compared to WT mice. Absence of periostin reduced mRNA levels of pivotal genes in wound repair, including α-SMA/acta2, fibronectin and βigh3. Recruitment of fibroblasts and inflammatory cells, as visualized by immunofluorescent staining for fibroblast specific factor-1, vimentin, and macrophages markers Arginase-1 and iNOS was also impaired in Postn−/−, but not WT mice. Palatal fibroblasts isolated from the hard palate of mice were cultured on collagen gels and prefabricated silicon substrates with varying stiffness. Postn−/− fibroblasts showed a significantly reduced ability to contract a collagen gel, which was rescued by the exogenous addition of recombinant periostin. As the stiffness increased, Postn−/− fibroblasts increasingly differentiated into myofibroblasts, but not to the same degree as the WT. Pharmacological inhibition of Rac rescued the deficient myofibroblastic phenotype of Postn−/− cells. Low stiffness substrates (0.2 kPa) resulted in upregulation of fibronectin in WT cells, an effect which was significantly reduced in Postn−/− cells. Quantification of immunostaining for vinculin and integrinβ1 adhesions revealed that Periostin is required for the formation of focal and fibrillar adhesions in mPFBs. Our results suggest that periostin modulates myofibroblast differentiation and contraction via integrinβ1/RhoA pathway, and fibronectin synthesis in an ECM stiffness dependent manner in palatal healing.

Fusobacterium nucleatum host-cell binding and invasion induces IL-8 and CXCL1 secretion that drives colorectal cancer cell migration.

Fusobacterium nucleatum is implicated in accelerating colorectal cancer (CRC) and is found within metastatic CRC cells in patient biopsies. Here, we found that bacterial invasion of CRC cells and cocultured immune cells induced a differential cytokine secretion that may contribute to CRC metastasis. We used a modified galactose kinase markerless gene deletion approach and found that F. nucleatum invaded cultured HCT116 CRC cells through the bacterial surface adhesin Fap2. In turn, Fap2-dependent invasion induced the secretion of the proinflammatory cytokines IL-8 and CXCL1, which are associated with CRC progression and promoted HCT116 cell migration. Conditioned medium from F. nucleatum-infected HCT116 cells caused naïve cells to migrate, which was blocked by depleting CXCL1 and IL-8 from the conditioned medium. Cytokine secretion from HCT116 cells and cellular migration were attenuated by inhibiting F. nucleatum host-cell binding and entry using galactose sugars, l-arginine, neutralizing membrane protein antibodies, or fap2 deletion. F. nucleatum also induces the mobilization of immune cells in the tumor microenvironment. However, in neutrophils and macrophages, the bacterial-induced secretion of cytokines was Fap2 independent. Thus, our findings show that F. nucleatum both directly and indirectly modulates immune and cancer cell signaling and migration. Because increased IL-8 and CXCL1 production in tumors is associated with increased metastatic potential and cell seeding, poor prognosis, and enhanced recruitment of tumor-associated macrophages and fibroblasts, we propose that inhibition of host-cell binding and invasion, potentially through vaccination or novel galactoside compounds, could be an effective strategy for reducing F. nucleatum-associated CRC metastasis.

USING OF BIOCORRECTORS IN REGENERATION PACING OF MECHANICALLY INJURED RATS’ FETAL HEPATIC

The article is devoted to studying the influence of biologically active substances on the regeneration of internal organs in mammals at the early stages of development. Complete recovery of the organ after damage does not occur. It is necessary to look for new ways that reveal the processes that contribute to regeneration. The study of processes that occur in the body before birth allows understanding the mechanisms of what happens in the postnatal period in general pathological processes. It was studied the mechanical damage to the liver in rat fetuses under the influence of biocorrectors “Trepel” and “Suvar.” Morphological, morphometric, histochemical, and immunohistochemical methods were used for processing the material. The results of the work indicate that the combined use of these biocorrectors after the development of a necrosis focus in the liver reduces alternative manifestations of hepatocytes, inhibits reactive inflammation around the injury site, slows down the recruitment of fibroblasts to the injury zone, and inhibits collagen genesis. At the same time, biocorrectors have a pronounced stimulating effect on proliferation of hepatocytes, which, against the background of increased enzymatic activity, manifests itself in the form of mitotic division activation and polyploidization of hepatocytes. Despite the signs of regenerative stimulation, as a result, complete recovery of the liver in the site of the dead tissue in experimental rats does not occur; there is only a 34.7% decrease in the focus of fibrosis formed in the place of dead liver tissue, compared to control animals.

Cylindromatosis Lysine 63 Deubiquitinase (CYLD) Regulates NF-kB Signaling Pathway and Modulates Fibroblast and Endothelial Cells Recruitment in Nasopharyngeal Carcinoma.

Nasopharyngeal carcinoma (NPC) is a malignant epithelial carcinoma of the nasopharynx. Cylindromatosis lysine 63 deubiquitinase (CYLD), a NF-kB inhibitor, was reported as one of the top mutated candidate genes in NPC. NF-kB is an inducible transcription factor, contributing to cancer via regulating inflammation, angiogenesis, cell proliferation, and metastasis. In this study, the impact of CYLD on regulating the NF-kB signaling pathway and its contribution to NPC development was studied using in vitro and in vivo functional assays, together with single cell RNA sequencing to understand the NPC tumor microenvironment. CYLD was downregulated in NPC clinical specimens and multiple cell lines. Functional assays revealed CYLD inhibits NPC cell proliferation and migration in vitro and suppresses NPC tumorigenicity and metastasis in vivo by negatively regulating the NF-kB signaling pathway. Additionally, CYLD was able to inhibit fibroblast and endothelial stromal cell infiltration into the NPC tumor microenvironment. These findings suggest that CYLD inhibits NPC development and provides strong evidence supporting a role for CYLD inhibiting fibroblast and endothelial stromal cell infiltration into NPC via suppressing the NF-kB pathway.

Potential Mechanism of Dermal Wound Treatment With Preparations From the Skin Gel of Arabian Gulf Catfish: A Unique Furan Fatty Acid (F6) and Cholesta-3,5-Diene (S5) Recruit Neutrophils and Fibroblasts to Promote Wound Healing.

Preparations from Arabian Gulf catfish (Arius bilineatus, Val) epidermal gel secretion (PCEGS) effectively heal chronic wounds in diabetic patients. However, specific lipid components of PCEGS that are responsible for various aspects of wound healing are unknown. Here, we report for the first time that, i) a unique preparation containing only proteins and lipids (Fraction B, FB), derived from the PCEGS accelerated the healing of experimental dermal wounds in female rats (transdermal punch biopsy) in vivo. Histological analyses showed that topical treatment of these wounds with FB promoted the migration of fibroblasts, facilitated the production of extracellular matrix (collagen, fibronectin), induced capillary formation and recruitment of immune cells, and accelerated overall wound healing by day 4 (tested at 1, 2, 3, 4, and 10 days; n=15 for vehicle; n=15 for FB treatment), ii) the lipids responsible for different stages of wound healing were separated into a protein-free bioactive lipid fraction, Ft, which contained a few common long-chain fatty acids, a unique furan fatty acid (F6) and a cholesterol metabolite, cholesta-3,5-diene (S5). Ft (the partially purified lipid fraction of PCEGS), and F6 and S5 present in Ft, proved to be bioactive for wound healing in human dermal fibroblasts. Ft increased the production and extracellular deposition of collagen and fibronectin, ex vivo, iii) Ft and its subcomponents, pure F6 and S5, also promoted human dermal fibroblast migration into the scratch wound gaps, ex vivo, iv) Ft, F6, and S5 promoted the recruitment of neutrophils (Green fluorescence protein labeled) to the site of injury in the transected tailfins of transgenic zebrafish, in vivo, v) Ft, but not F6 or S5, promoted the regeneration of tissues at the wound site in the transgenic zebrafish tailfin, in vivo. Therefore, we conclude that lipid fraction Ft from PCEGS contains the components necessary to promote complete wound healing, and F6 and S5 are responsible for promoting fibroblast and neutrophil recruitment to the site of wounds.

Phosphoinositide 3-kinase γ deficiency attenuates kidney injury and fibrosis in angiotensin II-induced hypertension.

We have shown that the CXCL16/CXCR6 axis plays a critical role in recruiting inflammatory cells and bone marrow-derived fibroblasts into the kidney leading to renal injury and fibrosis. However, the underlying signaling mechanisms are not known. In the present study, we examined the role of phosphoinositide-3 kinase γ (PI3Kγ) signaling in the recruitment of inflammatory cells and bone marrow-derived fibroblasts into the kidney and development of renal injury and fibrosis in an experimental model of hypertension induced by angiotensin II. Blood pressure was comparable between wild-type (WT) and PI3Kγ knockout (KO) mice at baseline. Angiotensin II treatment led to an increase in blood pressure that was similar between WT and PI3Kγ KO mice. Compared with WT mice, PI3Kγ KO mice were protected from angiotensin II-induced renal dysfunction and injury and developed less proteinuria. PI3Kγ deficiency suppressed bone marrow-derived fibroblast accumulation and myofibroblast formation in the kidney and inhibited total collagen deposition and extracellular matrix protein production in the kidney in response to angiotensin II. PI3Kγ deficiency inhibited the infiltration of F4/80+ macrophages and CD3+ T cells into the kidney and reduced gene expression levels of pro-inflammatory cytokines in the kidney following angiotensin II treatment. Finally, inhibition of PI3Kγ suppressed CXCL16-induced monocyte migration in vitro. These results indicate that PI3Kγ mediates the influx of macrophages, T cells and bone marrow-derived fibroblasts into the kidney resulting in kidney injury and fibrosis.

ROCK-mediated selective activation of PERK signalling causes fibroblast reprogramming and tumour progression through a CRELD2-dependent mechanism

It is well accepted that cancers co-opt the microenvironment for their growth. However, the molecular mechanisms that underlie cancer-microenvironment interactions are still poorly defined. Here, we show that Rho-associated kinase (ROCK) in the mammary tumour epithelium selectively actuates protein-kinase-R-like endoplasmic reticulum kinase (PERK), causing the recruitment and persistent education of tumour-promoting cancer-associated fibroblasts (CAFs), which are part of the cancer microenvironment. An analysis of tumours from patients and mice reveals that cysteine-rich with EGF-like domains 2 (CRELD2) is the paracrine factor that underlies PERK-mediated CAF education downstream of ROCK. We find that CRELD2 is regulated by PERK-regulated ATF4, and depleting CRELD2 suppressed tumour progression, demonstrating that the paracrine ROCK-PERK-ATF4-CRELD2 axis promotes the progression of breast cancer, with implications for cancer therapy.

Fibrin fragment E potentiates TGF-β-induced myofibroblast activation and recruitment

Fibrin is an essential constituent of the coagulation cascade, and the formation of hemostatic fibrin clots is central to wound healing. Fibrin clots are over time degraded into fibrin degradation products as the injured tissue is replaced by granulation tissue. Our goal was to study the role of the fibrin degradation product fragment E (FnE) in fibroblast activation and migration. We present evidence that FnE is a chemoattractant for fibroblasts and that FnE can potentiate TGF-β-induced myofibroblast formation. FnE forms a stable complex with αVβ3 integrin, and the integrin β3 subunit is required both for FnE-induced fibroblast migration and for potentiation of TGF-β-induced myofibroblast formation. Finally, subcutaneous infusion of FnE in mice results in a fibrotic response in the hypodermis. These results support a model where FnE released from clots in wounded tissue promote wound healing and fibrosis by both recruitment and activation of fibroblasts. Fibrin fragment E could thus represent a therapeutic target for treatment of pathological fibrosis.

Characterizing the Role of the Na+‐H+ Exchanger Isoform 1 (NHE1) in Pulmonary Fibrosis

Pulmonary fibrosis is a chronic, progressive lung disease characterized by stiffening and thickening of the lung tissue leading to reduced respiratory function. When lung tissue becomes damaged, the response is to increase recruitment and proliferation of fibroblasts and increase deposition of extracellular matrix (ECM) proteins such as collagen. This initiates the release of transforming growth factor beta 1 (TGF‐β1), a cytokine known to enhance fibrosis. TGF‐β1 induces myofibroblast differentiation and further stiffening of the ECM by stimulating formation of cytoplasmic microfilament bundles and increasing expression of alpha‐smooth muscle actin (α‐SMA). Signal molecules such as serotonin (5‐HT), and lysophosphatidic acid (LPA) contribute to this by binding to G‐protein coupled receptors that support increased release of TGF‐β1. Fibrosis ultimately results in a state of low blood flow and hypoxia in the lung tissue, a microenvironment associated with upregulation of the sodium‐hydrogen exchanger isoform 1 (NHE1). NHE1 is a ubiquitously expressed protein that regulates intracellular pH. Upregulation of NHE1 supports increased cell proliferation and migration, indicating that it may play a role in the behavior of fibroblasts in pulmonary fibrosis. The proliferation, collagen deposition, and myofibroblast differentiation of two fibroblast cell lines will be characterized. CCL39, Chinese hamster lung fibroblasts, and WI‐38, normal human fibroblast cells, will both be studied. CCL39 cells treated with EIPA, a chemical inhibitor of NHE1, show reduced proliferative rates. This suggests that proliferation in these cells is NHE1‐dependent. In addition to proliferation, it is hypothesized that the collagen deposition and myofibroblast differentiation of this cell line will be NHE1‐dependent. Furthermore, it is hypothesized that WI‐38 cells will display similar NHE1‐dependent proliferation, collagen deposition and myofibroblast differentiation as the CCL39 cells. This suggests that CCL39 cells can serve as a predictor of human fibroblast cell behaviors.

The Role of Chemokine Receptors in Renal Fibrosis.

Renal fibrosis is the final pathological process common to any ongoing, chronic kidney injury or maladaptive repair. Renal fibrosis is considered to be closely related to various cell types, such as fibroblasts, myofibroblasts, T cells, and other inflammatory cells. Multiple types of cells regulate renal fibrosis through the recruitment, proliferation, and activation of fibroblasts, and the production of the extracellular matrix. Cell trafficking is orchestrated by a family of small proteins called chemokines. Chemokines are cytokines with chemotactic properties, which are classified into 4 groups: CXCL, CCL, CX3CL, and XCL. Similarly, chemokine receptors are G protein-coupled seven-transmembrane receptors classified into 4 groups: XCR, CCR, CXCR, and CX3CR. Chemokine receptors are also implicated in the infiltration, differentiation, and survival of functional cells, triggering inflammation that leads to fibrosis development. In this review, we summarize the different chemokine receptors involved in the processes of fibrosis in different cell types. Further studies are required to identify the molecular mechanisms of chemokine signaling that contribute to renal fibrosis.