The myofibroblast matrix: implications for tissue repair and fibrosis

Inhibition of ER stress by targeting the IRE1α-TXNDC5 pathway alleviates crystalline silica-induced pulmonary fibrosis

Long-term exposure to crystalline silica (CS) results in silicosis, which is characterized by progressive pulmonary fibrosis. The endoplasmic reticulum (ER) plays a critical role in protein processing, and the accumulation of unfolded proteins triggered by external stimuli often leads to ER stress. In the present study, we found that inhibition of ER stress alleviated CS-induced pulmonary fibrosis. Moreover, we observed that TXNDC5, a resident ER protein, was involved in the activation of fibroblasts. Mechanistically, we explored the relationship between ER stress and TXNDC5 and demonstrated that IRE1α-XBP-1 signaling was closely related to TXNDC5. Pharmacological inhibition of IRE1α endoribonuclease activity, in addition to knockdown of Xbp1 expression, reduced TXNDC5 expression in activated fibroblasts. Furthermore, pharmacological inhibition of IRE1α in vivo ameliorated pulmonary function and delayed CS-induced lung fibrosis. In conclusion, the present study illuminates the role of ER stress-related IRE1α-TXNDC5 signaling in fibroblast activation and its effects on CS-induced pulmonary fibrogenesis, which may provide novel targets for silicosis therapy.

Eplerenone Attenuates Fibrosis in the Contralateral Kidney of UUO Rats by Preventing Macrophage-to-Myofibroblast Transition

Severe renal fibrosis often occurs in obstructive kidney disease, not only in the obstructed kidney but also in the contralateral kidney, causing renal dysfunction. Although the mechanisms of injury in obstructed kidney have been studied for years, the pathogenesis of fibrosis in the contralateral kidney remains largely unknown. Here, we examined long-term unilateral ureteral obstruction (UUO) model in male Sprague-Dawley rats and found that macrophage-to-myofibroblast transition (MMT) is contributing to renal fibrosis in the contralateral kidney of UUO rats. Interestingly, this process was attenuated by treatment of eplerenone, a specific blocker of the mineralocorticoid receptor (MR). In-vitro, stimulating MR in primary cultured or cell line macrophages enhances MMT, which were also inhibited by MR blockade. Collectively, these findings provide a plausible mechanism for UUO-induced injury in the contralateral kidney, suggesting the benefit of using MR blockage as a part of treatment to UUO to protect the contralateral kidney thereby preserve renal function.

Development of poly(D,L-lactic-co-glycolic acid) films coated with biomembrane-mimicking polymers for anti-adhesion activity

A physical barrier is one of the most effective strategies to alleviate excessive postoperative adhesion (POA) between tissues at an injury site. To overcome the limitations of current polymeric film-type physical barriers, we suggest a film of poly(lactic-co-glycolic acid) (PLGA) that is non-covalently coated with poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate (BMA)) (PMB). While maintaining the degradability and mechanical properties of PLGA, the PMB coating introduces strong anti-adhesive properties to the film by forming a zwitterionic MPC-based surface through the hydrophobic interactions between BMA moieties and PLGA. Compared to SurgiWrap®, the commercially available poly(lactic acid)-based anti-adhesive film against POA, the PMB-coated PLGA film is much more inhibitory against protein adsorption and fibroblast adhesion, processes that are crucial to the POA process. PMB coating also inhibits the expression of fibronectin containing extra domain A (FN-EDA), α-smooth muscle actin (α-SMA), and collagen type IV alpha 2 (COL4A2), which are marker genes and proteins involved in fibroblast activation and excessive fibrosis during POA. Such inhibitory activities are clearly observed in a 3-dimensional culture of fibroblasts within a collagen matrix, which mimics the in vivo environment of an injury site, as well as in a 2-dimensional culture. The kinetics and the stability of the PMB coating suggest potential future clinical use to coat PLGA films to create a film-type anti-adhesion barrier that overcomes the limitations of current products.

Emerging roles of steroid receptor coactivators in stromal cell responses

Tissue parenchyma is the functional unit of an organ and all of the remaining cells within that organ collectively make up the tissue stroma. The stroma includes fibroblasts, endothelial cells, immune cells, and nerves. Interactions between stromal and epithelial cells are essential for tissue development and healing after injury. These interactions are governed by growth factors, inflammatory cytokines and hormone signaling cascades. The steroid receptor coactivator (SRC) family of proteins includes three transcriptional coactivators that facilitate the assembly of multi-protein complexes to induce gene expression in response to activation of many cellular transcription factor signaling cascades. They are ubiquitously expressed and are especially critical for the developmental function of steroid hormone responsive tissues. The SRCs are overexpressed in multiple cancers including breast, ovarian, prostate and endometrial cancers. In this review, we focus on the role of the SRCs in regulating the functions of stromal cell components responsible for angiogenesis, inflammation and cell differentiation.

Proteoglycans in the periodontium: A review with emphasis on specific distributions, functions, and potential applications

Proteoglycans (PGs) are largely glycosylated proteins, consisting of a linkage sugar, core proteins, and glycosaminoglycans (GAGs). To date, more than 40 kinds of PGs have been identified, and they can be classified as intracellular, cell surface, pericellular, and extracellular PGs according to cellular locations. To illustrate, extracellular PGs are known for regulating the homeostasis of the extracellular matrix; cell-surface PGs play a role in mediating cell adhesion and binding various growth factors. In the field of periodontology, PGs are implicated in cellular proliferation, migration, adhesion, contractility, and anoikis, thereby exerting a profound influence on periodontal tissue development, wound repair, the immune response, biomechanics, and pathological process. Additionally, the expression patterns of some PGs are dynamic and cell-specific. Therefore, determining the roles and spatial-temporal expression patterns of PGs in the periodontium could shed light on treatments for wound healing, tissue regeneration, periodontitis, and gingival overgrowth. In this review, close attention is paid to the distributions, functions, and potential applications of periodontal PGs. Related genetically modified animal experiments and involved signal transduction cascades are summarized for improved understanding of periodontal PGs. To date, however, there is a large amount of speculation on this topic that requires rigorous experiments for validation.

Macromolecular Crowding as a Tool to Screen Anti-fibrotic Drugs: The Scar-in-a-Jar System Revisited

An unsolved therapeutic problem in fibrosis is the overproduction of collagen. In order to screen the effect of anti-fibrotic drugs on collagen deposition, the Scar-in-a-Jar approach has been introduced about a decade ago. With macromolecular crowding a rapid deposition of collagen is seen, resulting in a substantial decrease in culture time, but the system has never been tested in an adequate way. We therefore have compared six different macromolecular crowders [Ficoll PM 70 (Fc70), Ficoll PM 400 (Fc400), a mixture of Ficoll 70 and 400 (Fc70/400), polyvinylpyrrolidone 40 (PVP40), polyvinylpyrrolidone 360 (PVP360), neutral dextran 670 (ND670), dextran sulfate 500 (DxS500), and carrageenan (CR)] under profibrotic conditions (addition of TGFβ1) with primary human adult dermal fibroblasts in the presence of 0.5 and 10% FBS. We found that (1) collagen deposition and myofibroblast formation was superior with 0.5% FBS, (2) DxS500 and CR results in an aberrant collagen deposition pattern, (3) ND670 does not increase collagen deposition, and (4) CR, DxS500, and Fc40/700 affected important phenotypical properties of the cells when cultured under pro-fibrotic conditions, whereas PVP40 and PVP360 did less or not. Because of viscosity problems with PVP360, we conclude that PVP40 is the most optimal crowder for the screening of anti-fibrotic drugs. Finally, the effect of various concentrations of Imatinib, Galunisertib, Omipalisib or Nintedanib on collagen deposition and myofibroblast formation was tested with PVP40 as the crowder.

Autophagy, tissue repair, and fibrosis: a delicate balance

Tissue repair and fibrosis, an abnormal form of repair, occur in most human organs in response to injury or inflammation. Fibroblasts play a major role in the normal repair process by differentiating into myofibroblasts that synthesize extracellular matrix (ECM) components and favor tissue remodeling to reestablish normal function and integrity. However, their persistent accumulation at the site of injury is a hallmark of fibrosis. Autophagy is a catabolic process that occurs in eukaryotic cells as a stress response to allow cell survival and maintenance of cellular homeostasis by degrading and recycling intracellular components. Recent advances identify autophagy as an important regulator of myofibroblast differentiation, tissue remodeling, and fibrogenesis. In this mini-review, we provide an overview of the interactions between autophagy, ECM, and fibrosis, and emphasize the molecular mechanisms involved in myofibroblast differentiation. We also describe the emerging concept of secretory autophagy as a new avenue for intercellular communication at the site of tissue injury and repair.

Airway Elastin is increased in severe asthma and relates to proximal wall area: histological and computed tomography findings from the U-BIOPRED severe asthma study

BACKGROUND

Airway remodelling, which may include goblet cell hyperplasia / hypertrophy, changes in epithelial integrity, accumulation of extracellular matrix components, smooth muscle hypertrophy and thickening of the lamina reticularis, is a feature of severe asthma and contributes to the clinical phenotype.

OBJECTIVE

Within the U-BIOPRED severe asthma study, we have assessed histological elements of airway remodelling and their relationship to computed tomography (CT) measures of proximal airway dimensions.

METHODS

Bronchial biopsies were collected from two severe asthma groups, one non-smoker (SAn, n = 28) and one current/ex-smoker (SAs/ex, n = 13), and a mild-moderate asthma group (MMA, n = 28) classified and treated according to GINA guidelines, plus a healthy control group (HC, n = 33). Movat's pentachrome technique was used to identify mucin, elastin and total collagen in these biopsies. The number of goblet cells (mucin+) was counted as a percentage of the total number of epithelial cells and the percentage mucin epithelial area measured. The percentage area of elastic fibres and total collagen within the submucosa was also measured, and the morphology of the elastic fibres classified. Participants in the asthma groups also had a CT scan to assess large airway morphometry.

RESULTS

The submucosal tissue elastin percentage was higher in both severe asthma groups (16.1% SAn, 18.9% SAs/ex) compared with the HC (9.7%) but did not differ between asthma groups. There was a positive relationship between elastin and airway wall area measured by CT (n = 18-20, rho=0.544, p = 0.024), which also related to an increase in elastic fibres with a thickened lamellar morphological appearance. Mucin epithelial area and total collagen were not different between the four groups. Due to small numbers of suitable CT scans, it was not feasible to compare airway morphometry between the asthma groups.

CONCLUSION

These findings identify a link between extent of elastin deposition and airway wall thickening in severe asthma.

ECM-regulation of autophagy: The yin and the yang of autophagy during wound healing

Wound healing is a complex sequence of tissue protection, replacement, and reorganization leading to regenerated tissue. Disruption of any of these steps results in the process being incomplete as an ulcer or over-exuberant as a hypertrophic scar. Over the past decade, it has become evident that the extracellular matrix and associated components orchestrate this process. However, the cellular events that are induced by the extracellular matrix to accomplish wound healing remain to be defined. Herein we propose that matrix-regulated cellular macro-autophagy is key to both the tissue replacement and resolution stages of healing by directing cellular function or apoptosis. Further, disruptions in matrix turnover alter autophagic function leading to chronic wounds or scarring. While the literature that directly investigates autophagy during wound healing is sparse, the emerging picture supports our proposing a model of the centrality of the matrix-autophagy modulation as central to physiologic and pathologic healing.

Myofibroblast Markers and Microscopy Detection Methods in Cell Culture and Histology

The identification of myofibroblasts is essential for mechanistic in vitro studies, cell-based drug tests, and to assess the level of fibrosis in experimental animal or human fibrosis. The name myo-fibroblast was chosen in 1971 to express that the formation of contractile features-stress fibers is the essential criterion to define these cells. Additional neo-expression of α-smooth muscle actin (α-SMA) in stress fibers has become the most widely used molecular marker. Here, we briefly introduce the concept of different myofibroblast activation states, of which the highly contractile α-SMA-positive phenotype represents a most advanced functional stage. We provide targeted immunofluorescence protocols to assess this phenotype, and publicly accessible image analysis tools to quantify the level of myofibroblast activation in culture and in tissues.

Adenosine A1 Receptor Deficiency Aggravates Extracellular Matrix Accumulation in Diabetic Nephropathy through Disturbance of Peritubular Microenvironment

BACKGROUND

We previously observed that adenosine A1 receptor (A1AR) had a protective role in proximal tubular megalin loss associated with albuminuria in diabetic nephropathy (DN). In this study, we aimed to explore the role of A1AR in the fibrosis progression of DN.

METHODS

We collected DN patients' samples and established a streptozotocin-induced diabetes model in wild-type (WT) and A1AR-deficient (A1AR^-/-) mice. The location and expression of CD34, PDGFRβ, and A1AR were detected in kidney tissue samples from DN patients by immunofluorescent and immunohistochemical staining. We also analyzed the expression of TGFβ, collagen (I, III, and IV), α-SMA, and PDGFRβ using immunohistochemistry in WT and A1AR^-/- mice. CD34 and podoplanin expression were analyzed by Western blotting and immunohistochemical staining in mice, respectively. Human renal proximal tubular epithelial cells (HK2) were cultured in medium containing high glucose and A1AR agonist as well as antagonist.

RESULTS

In DN patients, the expression of PDGFRβ was higher with the loss of CD34. The location of PDGFRβ and TGFβ was near to each other. The A1AR, which was colocalized with CD34 partly, was also upregulated in DN patients. In WT-DN mice, obvious albuminuria and renal pathological leisure were observed. In A1AR^-/- DN mice, more severe renal tubular interstitial fibrosis and more extracellular matrix deposition were observed, with lower CD34 expression and pronounced increase of PDGFRβ. In HK2 cells, high glucose stimulated the epithelial-mesenchymal transition (EMT) process, which was inhibited by A1AR agonist.

CONCLUSION

A1AR played a critical role in protecting the tubulointerstitial fibrosis process in DN by regulation of the peritubular microenvironment.

Smoking effect on the ultrastructural properties of cultured lung myofibroblasts

This study aimed at an ultrastructural characterization of myofibroblasts cultured from different compartments of lung from never-smokers and smokers with or without COPD. In addition, we evaluated the expression of alpha smooth muscle actin (α-SMA), a marker for myofibroblasts, and contractile properties. Stromal cells cultured from central and corresponding peripheral or only from peripheral lung of never-smokers, smokers without COPD and COPD patients were analyzed by transmission electron microscopy (TEM), immunoelectron microscopy (IEM), Western analysis and/or by collagen gel contraction assay. TEM revealed that myofibroblasts cultured from smokers and COPD had less prominent intracellular actin filaments. We also examined fibronexus (FNX), which is a typical ultrastructural feature of myofibroblasts, and observed that patients with COPD more frequently had tandem-like FNX as compared to other samples. Western analysis showed that the samples derived from the central lung of never-smokers expressed higher levels of α-SMA than those of smokers and COPD patients. Cells from central lung were less contractile than those from peripheral lung. We conclude that myofibroblasts have variable ultrastructural and functional properties based on their localization in the lung and, moreover, these properties are affected by both smoking history and COPD.

MSC-released TGF-β regulate α-SMA expression of myofibroblast during wound healing

Objective: Wound healing without fibrosis remains a clinical challenge and a new strategy to promote the optimal wound healing is needed. Mesenchymal stem cells (MSCs) can completely regenerate tissue injury due to the robust MSCs ability in controlling inflammation niche leading to granulation tissue formation, particularly through a release of various growth factors including transforming growth factor-β (TGF-β). In response to TGF-β stimulation, fibroblasts differentiate into myofibroblast, marked by alpha-smooth muscle actin (α-SMA) that leads to wound healing acceleration. On the other hand, sustained activation of TGF-β in wound areas may contribute to fibrosis-associated scar formation. The aim of this study was to evaluate the α-SMA expression of myofibroblast induced by MSC-released TGF-β during wound healing process. Materials and Methods: Twenty-four full-thickness excisional rat wound models were randomly divided into four groups: sham (Sh), Control (C), and MSCs treatment groups; topically treated by the MSCs at doses 2x10⁶ cells (T1) and 1x10⁶ cells (T2), respectively. While the control group was treated with NaCl. TGF-β level was determined using ELISA assay, α-SMA expression of myofibroblast was analyzed by immunofluorescence staining, and wound size measurement was calculated using a standard caliper. Results: This study showed a significant increase in TGF-β levels in all treatment groups on days 3 and 6. This finding was consistent with a significant increase of α-SMA expression of myofibroblast at day 6 and wound closure percentage, indicating that MSCs might promote an increase of wound closure. Conclusion: MSCs regulated the release of TGF-β to induce α-SMA expression of myofibroblast for accelerating an optimal wound healing.

Overcoming interferon (IFN)-γ resistance ameliorates transforming growth factor (TGF)-β-mediated lung fibroblast-to-myofibroblast transition and bleomycin-induced pulmonary fibrosis

Abnormal activation of transforming growth factor (TGF)-β is a common cause of fibroblast activation and fibrosis. In bleomycin (BLM)-induced lung fibrosis, the marked expression of phospho-Src homology-2 domain-containing phosphatase (SHP) 2, phospho-signal transducer and activator of transcription (STAT) 3, and suppressor of cytokine signaling (SOCS) 3 was highly associated with pulmonary parenchymal lesions and collagen deposition. Human pulmonary fibroblasts differentiated into myofibroblasts exhibited activation of SHP2, SOCS3, protein inhibitor of activated STAT1, STAT3, interleukin (IL)-6, and IL-10. The significant retardation of interferon (IFN)-γ signaling in myofibroblasts was revealed by the decreased expression of phospho-STAT1, IFN-γ-associated genes, and IFN-γ-inducible protein (IP) 10. Microarray analysis showed an induction of fibrotic genes in TGF-β1-differentiated myofibroblasts, whereas IFN-γ-regulated anti-fibrotic genes were suppressed. Interestingly, BIBF 1120 treatment effectively inhibited both STAT3 and SHP2 phosphorylation in TGF-β1-differentiated myofibroblasts and BLM fibrotic lung tissues, which was accompanied by suppression of fibroblast-myofibroblast transition. Moreover, the combined treatment of BIBF 1120 plus IFN-γ or SHP2 inhibitor PHPS1 plus IFN-γ markedly reduced TGF-β1-induced α-smooth muscle actin and further ameliorated BLM lung fibrosis. Accordingly, myofibroblasts were hyporesponsiveness to IFN-γ, while blockade of SHP2 contributed to the anti-fibrotic efficacy of IFN-γ.

Pluripotent epigenetic regulator OBP-801 maintains filtering blebs in glaucoma filtration surgery model

Inhibition of fibrosis is indispensable for maintaining filtering blebs after glaucoma filtration surgery (GFS). The purpose of this study was to investigate the ability of a pluripotent epigenetic regulator OBP-801 (OBP) to ameliorate extracellular matrix formation in a rabbit model of GFS. Rabbits that underwent GFS were treated with OBP. The gene expression profiles and intraocular pressure (IOP) were monitored until 30 postoperative days. The bleb tissues were evaluated for tissue fibrosis at 30 postoperative days. In in vitro models, OBP interfered the functions of diverse genes during the wound-healing process. In in vivo GFS models, the expressions of TGF-β3, MMP-2, TIMP-2 and 3, LOX, COL1A and SERPINH1 were significantly inhibited at 30 postoperative days in the OBP group compared with those in the vehicle control group. OBP treatment involving subconjunctival injection or eye drops showed no adverse effects, and reduced levels of α-SMA and collagen deposition at the surgical wound site. OBP maintained the long-lived bleb without scar formation, and IOP was lower at 30 postoperative days compared with the vehicle control group. These findings suggest that OBP is an effective and useful candidate low-molecular-weight agent for improving wound healing and surgical outcomes in a rabbit model of GFS.

TGF-β Pathway in Salivary Gland Fibrosis

Fibrosis is presented in various physiologic and pathologic conditions of the salivary gland. Transforming growth factor beta (TGF-β) pathway has a pivotal role in the pathogenesis of fibrosis in several organs, including the salivary glands. Among the TGF-β superfamily members, TGF-β1 and 2 are pro-fibrotic ligands, whereas TGF-β3 and some bone morphogenetic proteins (BMPs) are anti-fibrotic ligands. TGF-β1 is thought to be associated with the pro-fibrotic pathogenesis of sialadenitis, post-radiation salivary gland dysfunction, and Sjögren’s syndrome. Potential therapeutic strategies that target multiple levels in the TGF-β pathway are under preclinical and clinical research for fibrosis. Despite the anti-fibrotic effect of BMPs, their in vivo delivery poses a challenge in terms of adequate clinical efficacy. In this article, we will review the relevance of TGF-β signaling in salivary gland fibrosis and advances of potential therapeutic options in the field.

A Tissue Engineering Approach to Metastatic Colon Cancer

Colon cancer remains the third most common cause of cancer in the US, and the third most common cause of cancer death. Worldwide, colon cancer is the second most common cause of cancer and cancer deaths. At least 25% of patients still present with metastatic disease, and at least 25-30% will develop metastatic colon cancer in the course of their disease. While chemotherapy and surgery remain the mainstay of treatment, understanding the fundamental cellular niche and mechanical properties that result in metastases would facilitate both prevention and cure. Advances in biomaterials, novel 3D primary human cells, modelling using microfluidics and the ability to alter the physical environment, now offers a unique opportunity to develop and test impactful treatment.

A Potential Theragnostic Regulatory Axis for Arthrofibrosis Involving Adiponectin (ADIPOQ) Receptor 1 and 2 (ADIPOR1 and ADIPOR2), TGFβ1, and Smooth Muscle α-Actin (ACTA2)

(1) Background: Arthrofibrosis is a common cause of patient debility and dissatisfaction after total knee arthroplasty (TKA). The diversity of molecular pathways involved in arthrofibrosis disease progression suggest that effective treatments for arthrofibrosis may require a multimodal approach to counter the complex cellular mechanisms that direct disease pathogenesis. In this study, we leveraged RNA-seq data to define genes that are suppressed in arthrofibrosis patients and identified adiponectin (ADIPOQ) as a potential candidate. We hypothesized that signaling pathways activated by ADIPOQ and the cognate receptors ADIPOR1 and ADIPOR2 may prevent fibrosis-related events that contribute to arthrofibrosis. (2) Methods: Therefore, ADIPOR1 and ADIPOR2 were analyzed in a TGFβ1 inducible cell model for human myofibroblastogenesis by both loss- and gain-of-function experiments. (3) Results: Treatment with AdipoRon, which is a small molecule agonist of ADIPOR1 and ADIPOR2, decreased expression of collagens (COL1A1, COL3A1, and COL6A1) and the myofibroblast marker smooth muscle α-actin (ACTA2) at both mRNA and protein levels in basal and TGFβ1-induced cells. (4) Conclusions: Thus, ADIPOR1 and ADIPOR2 represent potential drug targets that may attenuate the pathogenesis of arthrofibrosis by suppressing TGFβ-dependent induction of myofibroblasts. These findings also suggest that AdipoRon therapy may reduce the development of arthrofibrosis by mediating anti-fibrotic effects in joint capsular tissues.

NF-κB activation persists into the remodeling phase of tendon healing and promotes myofibroblast survival

Although inflammation is necessary during the early phases of tissue repair, persistent inflammation contributes to fibrosis. Acute tendon injuries often heal through a fibrotic mechanism, which impedes regeneration and functional recovery. Because inflammation mediated by nuclear factor κB (NF-κB) signaling is implicated in this process, we examined the spatial, temporal, and cell type-specific activation profile of canonical NF-κB signaling during tendon healing. NF-κB signaling was maintained through all phases of tendon healing in mice, including the remodeling phase, and tenocytes and myofibroblasts from the Scleraxis (Scx) lineage were the predominant populations that retained NF-κB activation into the late stages of repair. We confirmed persistent NF-κB activation in myofibroblasts in human tendon scar tissue. Deleting the canonical NF-κB kinase, IKKβ, in Scx-lineage cells in mice increased apoptosis and the deposition of the matrix protein periostin during the late stages of tendon repair, suggesting that persistent NF-κB signaling may facilitate myofibroblast survival and fibrotic progression. Consistent with this, myofibroblasts in human tendon scar samples displayed enhanced prosurvival signaling compared to control tissue. Together, these data suggest that NF-κB may contribute to fibrotic tendon healing through both inflammation-dependent and inflammation-independent functions, such as NF-κB-mediated cell survival.

Primary Ciliary Signaling in the Skin-Contribution to Wound Healing and Scarring

Primary cilia (PC) are solitary, post-mitotic, microtubule-based, and membrane-covered protrusions that are found on almost every mammalian cell. PC are specialized cellular sensory organelles that transmit environmental information to the cell. Signaling through PC is involved in the regulation of a variety of cellular processes, including proliferation, differentiation, and migration. Conversely, defective, or abnormal PC signaling can contribute to the development of various pathological conditions. Our knowledge of the role of PC in organ development and function is largely based on ciliopathies, a family of genetic disorders with mutations affecting the structure and function of PC. In this review, we focus on the role of PC in their major signaling pathways active in skin cells, and their contribution to wound healing and scarring. To provide comprehensive insights into the current understanding of PC functions, we have collected data available in the literature, including evidence across cell types, tissues, and animal species. We conclude that PC are underappreciated subcellular organelles that significantly contribute to both physiological and pathological processes of the skin development and wound healing. Thus, PC assembly and disassembly and PC signaling may serve as attractive targets for antifibrotic and antiscarring therapies.

Lumican promotes joint fibrosis through TGF-β signaling

Joint contracture (also known as arthrofibrosis) is a fibrotic joint disorder characterized by excessive collagen production to form fibrotic scar tissue and adhesions within joint capsules. This can severely affect day‐to‐day activities and quality of life because of a restricted range of motion in affected joints. The precise pathogenic mechanism underlying joint contractures is not fully understood. Lumican belongs to the class II small leucine‐rich repeat proteoglycan superfamily, which makes up collagen fibrils in the extracellular matrix. Lumican is ubiquitously expressed in the skin, liver, heart, uterus and articular cartilage and has reported roles in cell migration, proliferation, angiogenesis and Toll‐like receptor 4 signaling. Previous research has suggested that lumican is involved in the pathogenesis of several fibrotic diseases. Because joint contracture resembles a fibrotic disease, we aimed to investigate the role of lumican in the development of joint contracture in vitro. Here, we showed that protein levels were up‐regulated in the fibrotic joint capsule versus control. We observed that lumican significantly enhanced the proliferation, migration and fibroblast–myofibroblast transition of synovial fibroblasts. Moreover, lumican led to increased transcription of alpha‐smooth muscle actin, matrix metallopeptidase 9, Collagen I, plasminogen activator inhibitor 1 and transforming growth factor‐β in vitro. Lumican treatment promoted collagen lattice contraction in a dose‐dependent manner as early as 24 h after treatment. Thus, our studies reveal that lumican could promote fibroblast–myofibroblast transition and joint contracture.

The promise of mTOR as a therapeutic target pathway in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterised by the progressive deposition of excessive extracellular matrix proteins within the lung parenchyma and represents the most rapidly progressive and fatal of all fibrotic conditions. Current anti-fibrotic drugs approved for the treatment of IPF fail to halt disease progression and have significant side-effect profiles. Therefore, there remains a pressing need to develop novel therapeutic strategies for IPF. Mammalian target of rapamycin (mTOR) forms the catalytic subunit of two complexes, mTORC1 and mTORC2. mTORC1 acts as critical cellular sensor which integrates intracellular and extracellular signals to reciprocally regulate a variety of anabolic and catabolic processes. The emerging evidence for a critical role for mTORC1 in influencing extracellular matrix production, metabolism, autophagy and senescence in the setting of IPF highlights this axis as a novel therapeutic target with the potential to impact multiple IPF pathomechanisms.

Current evidence supports the scientific rationale for targeting the mTOR pathway in idiopathic pulmonary fibrosishttps://bit.ly/33OQiYf

Quantitative proteomic comparison of myofibroblasts derived from bone marrow and cornea

Myofibroblasts are fibroblastic cells that function in wound healing, tissue repair and fibrosis, and arise from bone marrow (BM)-derived fibrocytes and a variety of local progenitor cells. In the cornea, myofibroblasts are derived primarily from stromal keratocytes and from BM-derived fibrocytes after epithelial-stromal and endothelial-stromal injuries. Quantitative proteomic comparison of mature alpha-smooth muscle actin (α-SMA)+ myofibroblasts (verified by immunocytochemistry for vimentin, α-SMA, desmin, and vinculin) generated from rabbit corneal fibroblasts treated with transforming growth factor (TGF) beta-1 or generated directly from cultured BM treated with TGF beta-1 was pursued for insights into possible functional differences. Paired cornea-derived and BM-derived α-SMA+ myofibroblast primary cultures were generated from four New Zealand white rabbits and confirmed to be myofibroblasts by immunocytochemistry. Paired cornea- and BM-derived myofibroblast specimens from each rabbit were analyzed by LC MS/MS iTRAQ technology using an Orbitrap Fusion Lumos Tribrid mass spectrometer, the Mascot search engine, the weighted average quantification method and the UniProt rabbit and human databases. From 2329 proteins quantified with ≥ 2 unique peptides from ≥ 3 rabbits, a total of 673 differentially expressed (DE) proteins were identified. Bioinformatic analysis of DE proteins with Ingenuity Pathway Analysis implicate progenitor-dependent functional differences in myofibroblasts that could impact tissue development. Our results suggest BM-derived myofibroblasts may be more prone to the formation of excessive cellular and extracellular material that are characteristic of fibrosis.

Transforming growth factor-β1 promotes fibrosis but attenuates calcification of valvular tissue applied as a three-dimensional calcific aortic valve disease model

Calcific aortic valve disease (CAVD) is characterized by valvular fibrosis and calcification and driven by differentiating valvular interstitial cells (VICs). Expression data from patient biopsies suggest that transforming growth factor (TGF)-β1 is implicated in CAVD pathogenesis. However, CAVD models using isolated VICs failed to deliver clear evidence on the role of TGF-β1. Thus, employing cultures of aortic valve leaflets, we investigated effects of TGF-β1 in a tissue-based three-dimensional (3-D) CAVD model. We found that TGF-β1 induced phosphorylation of Mothers against decapentaplegic homolog (SMAD) 3 and expression of SMAD7, indicating effective downstream signal transduction in valvular tissue. Thus, TGF-β1 increased VIC contents of rough endoplasmic reticulum, Golgi, and secretory vesicles as well as tissue levels of RNA and protein. In addition, TGF-β1 raised expression of proliferation marker cyclin D1, attenuated VIC apoptosis, and upregulated VIC density. Moreover, TGF-β1 intensified myofibroblastic VIC differentiation as evidenced by increased α-smooth muscle actin and collagen type I along with diminished vimentin expression. In contrast, TGF-β1 attenuated phosphorylation of SMAD1/5/8 and upregulation of β-catenin while inhibiting osteoblastic VIC differentiation as revealed by downregulation of osteocalcin expression, alkaline phosphatase activity, and extracellular matrix incorporation of hydroxyapatite. Collectively, these effects resulted in blocking of valvular tissue calcification and associated disintegration of collagen fibers. Instead, TGF-β1 induced development of fibrosis. Overall, in a tissue-based 3-D CAVD model, TGF-β1 intensifies expressional and proliferative activation along with myofibroblastic differentiation of VICs, thus triggering dominant fibrosis. Simultaneously, by inhibiting SMAD1/5/8 activation and canonical Wnt/β-catenin signaling, TGF-β1 attenuates osteoblastic VIC differentiation, thus blocking valvular tissue calcification. These findings question a general phase-independent CAVD-promoting role of TGF-β1.NEW & NOTEWORTHY Employing aortic valve leaflets as a tissue-based three-dimensional disease model, our study investigates the role of transforming growth factor (TGF)-β1 in calcific aortic valve disease pathogenesis. We find that, by activating Mothers against decapentaplegic homolog 3, TGF-β1 intensifies expressional and proliferative activation along with myofibroblastic differentiation of valvular interstitial cells, thus triggering dominant fibrosis. Simultaneously, by inhibiting activation of Mothers against decapentaplegic homolog 1/5/8 and canonical Wnt/β-catenin signaling, TGF-β1 attenuates apoptosis and osteoblastic differentiation of valvular interstitial cells, thus blocking valvular tissue calcification. These findings question a general phase-independent calcific aortic valve disease-promoting role of TGF-β1.

Role of the CXCR4-SDF1-HMGB1 pathway in the directional migration of cells and regeneration of affected organs

In recent years, several studies have reported positive outcomes of cell-based therapies despite insufficient engraftment of transplanted cells. These findings have created a huge interest in the regenerative potential of paracrine factors released from transplanted stem or progenitor cells. Interestingly, this notion has also led scientists to question the role of proteins in the secretome produced by cells, tissues or organisms under certain conditions or at a particular time of regenerative therapy. Further studies have revealed that the secretomes derived from different cell types contain paracrine factors that could help to prevent apoptosis and induce proliferation of cells residing within the tissues of affected organs. This could also facilitate the migration of immune, progenitor and stem cells within the body to the site of inflammation. Of these different paracrine factors present within the secretome, researchers have given proper consideration to stromal cell-derived factor-1 (SDF1) that plays a vital role in tissue-specific migration of the cells needed for regeneration. Recently researchers recognized that SDF1 could facilitate site-specific migration of cells by regulating SDF1-CXCR4 and/or HMGB1-SDF1-CXCR4 pathways which is vital for tissue regeneration. Hence in this study, we have attempted to describe the role of different types of cells within the body in facilitating regeneration while emphasizing the HMGB1-SDF1-CXCR4 pathway that orchestrates the migration of cells to the site where regeneration is needed.

Myh11+ microvascular mural cells and derived mesenchymal stem cells promote retinal fibrosis

Retinal diseases are frequently characterized by the accumulation of excessive scar tissue found throughout the neural retina. However, the pathophysiology of retinal fibrosis remains poorly understood, and the cell types that contribute to the fibrotic response are incompletely defined. Here, we show that myofibroblast differentiation of mural cells contributes directly to retinal fibrosis. Using lineage tracing technology, we demonstrate that after chemical ocular injury, Myh11+ mural cells detach from the retinal microvasculature and differentiate into myofibroblasts to form an epiretinal membrane. Inhibition of TGFβR attenuates Myh11+ retinal mural cell myofibroblast differentiation, and diminishes the subsequent formation of scar tissue on the surface of the retina. We demonstrate retinal fibrosis within a murine model of oxygen-induced retinopathy resulting from the intravitreal injection of adipose Myh11-derived mesenchymal stem cells, with ensuing myofibroblast differentiation. In this model, inhibiting TGFβR signaling does not significantly alter myofibroblast differentiation and collagen secretion within the retina. This work shows the complexity of retinal fibrosis, where scar formation is regulated both by TGFβR and non-TGFβR dependent processes involving mural cells and derived mesenchymal stem cells. It also offers a cautionary note on the potential deleterious, pro-fibrotic effects of exogenous MSCs once intravitreally injected into clinical patients.

Anti-fibrotic Actions of Equine Interleukin-10 on Transforming Growth Factor-Beta1-Stimulated Dermal Fibroblasts Isolated From Limbs of Horses

Fibroproliferative disorders occur in both humans and horses following skin injury. In horses, wound healing on the limb is often complicated by the formation of fibroproliferative exuberant granulation tissue, characterized by persistent expression of pro-fibrotic transforming growth factor-beta1 (TGF-β1) and deficient expression of anti-inflammatory interleukin-10 (IL-10). IL-10 has been shown to directly modulate fibrotic gene expression in human fibroblasts, so we hypothesized that equine IL-10 (eIL-10) may exert similar anti-fibrotic effects on equine dermal fibroblasts. Cell-lines were created from the limb skin of six individual horses. Recombinant eIL-10 was produced and purified, and its effects on the cells investigated in the presence and absence of equine TGF-β1 (eTGF-β1). Myofibroblast differentiation and collagen production were examined using immunofluorescent cytometry, cell contractility in a collagen gel assay, and fibrotic gene expression using quantitative PCR. In response to eTGF-β1, fibroblasts increased in contractility and expression of alpha-smooth muscle actin, collagen types 1 and 3, and matrix metalloproteinase 1, 2, and 9. Equine IL-10 limited cell contractility and production of alpha-smooth muscle actin and type 3 collagen, and decreased mRNA levels of eCol3a1 and eMMP9, while increasing that of eMMP1. Opposing effects on eTGF-βR3 and eIL-10R1 gene expression were also observed, with mRNA levels decreasing following eTGF-β1 treatment, and increasing with eIL-10 treatment. These findings indicate that eIL-10 limits the pro-fibrotic effects of eTGF-β1, potentially through the modulation of fibrotic and receptor gene expression. Further investigations are warranted to assess the therapeutic utility of eIL-10 in the treatment of exuberant granulation tissue.

Interleukin-36 Cytokine/Receptor Signaling: A New Target for Tissue Fibrosis

Tissue fibrosis is a major unresolved medical problem, which impairs the function of various systems. The molecular mechanisms involved are poorly understood, which hinders the development of effective therapeutic strategies. Emerging evidence from recent studies indicates that interleukin 36 (IL-36) and the corresponding receptor (IL-36R), a newly-characterized cytokine/receptor signaling complex involved in immune-inflammation, play an important role in the pathogenesis of fibrosis in multiple tissues. This review focuses on recent experimental findings, which implicate IL-36R and its associated cytokines in different forms of organ fibrosis. Specifically, it outlines the molecular basis and biological function of IL-36R in normal cells and sums up the pathological role in the development of fibrosis in the lung, kidney, heart, intestine, and pancreas. We also summarize the new progress in the IL-36/IL-36R-related mechanisms involved in tissue fibrosis and enclose the potential of IL-36R inhibition as a therapeutic strategy to combat pro-fibrotic pathologies. Given its high association with disease, gaining new insight into the immuno-mechanisms that contribute to tissue fibrosis could have a significant impact on human health.

Selective YAP/TAZ inhibition in fibroblasts via dopamine receptor D1 agonism reverses fibrosis

Tissue fibrosis is characterized by uncontrolled deposition and diminished clearance of fibrous connective tissue proteins, ultimately leading to organ scarring. Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) have recently emerged as pivotal drivers of mesenchymal cell activation in human fibrosis. Therapeutic strategies inhibiting YAP and TAZ have been hindered by the critical role that these proteins play in regeneration and homeostasis in different cell types. Here, we find that the Gα_s-coupled dopamine receptor D1 (DRD1) is preferentially expressed in lung and liver mesenchymal cells relative to other resident cells of these organs. Agonism of DRD1 selectively inhibits YAP/TAZ function in mesenchymal cells and shifts their phenotype from profibrotic to fibrosis resolving, reversing in vitro extracellular matrix stiffening and in vivo tissue fibrosis in mouse models. Aromatic l-amino acid decarboxylase [DOPA decarboxylase (DDC)], the enzyme responsible for the final step in biosynthesis of dopamine, is decreased in the lungs of subjects with idiopathic pulmonary fibrosis, and its expression inversely correlates with disease severity, consistent with an endogenous protective role for dopamine signaling that is lost in pulmonary fibrosis. Together, these findings establish a pharmacologically tractable and cell-selective approach to targeting YAP/TAZ via DRD1 that reverses fibrosis in mice.

Proximal digit tip amputation initiates simultaneous blastema and transient fibrosis formation and results in partial regeneration

Complete extremity regeneration in mammals is restricted to distal amputations of the digit tip, the terminal phalanx (P3). In mice, P3 regeneration is mediated via the formation of a blastema, a transient population of progenitor cells that form from the blending of periosteal and endosteal/marrow compartmentalized cells that undergo differentiation to restore the amputated structures. Compartmentalized blastema cells are formed independently, and periosteal compartment-derived cells are required for restoration of amputated skeletal length. P3 regenerative capacity is progressively attenuated at increasingly more proximal amputation levels, eventually resulting in regenerative failure. The continuum of regenerative capacity within the P3 wound milieu is a unique model to investigate mammalian blastema formation in response to distal amputation, as well as the healing response associated with regenerative failure at proximal amputation levels. We report that P3 proximal amputation healing, previously reported to result in regenerative failure, is not an example of complete regenerative failure, but instead is characterized by a limited bone regeneration response restricted to the endosteal/marrow compartment. The regeneration response is mediated by blastema formation within the endosteal/marrow compartment, and blastemal osteogenesis progresses through intramembranous ossification in a polarized proximal to distal sequence. Unlike bone regeneration following distal P3 amputation, osteogenesis within the periosteal compartment is not observed in response to proximal P3 amputation. We provide evidence that proximal P3 amputation initiates the formation of fibrotic tissue that isolates the endosteal/marrow compartment from the periosteal compartment and wound epidermis. While the fibrotic response is transient and later resolved, these studies demonstrate that blastema formation and fibrosis can occur in close proximity, with the regenerative response dominating the final outcome. Moreover, the results suggest that the attenuated proximal P3 regeneration response is associated with the absence of periosteal-compartment participation in blastema formation and bone regeneration.

Huoxin pill attenuates myocardial infarction-induced apoptosis and fibrosis via suppression of p53 and TGF-β1/Smad2/3 pathways

Huoxin Pill (HXP), a Traditional Chinese Medicine, is used widely to treat patients with coronary heart disease and angina pectoris in China. However, the underlying protective mechanism of HXP on cardiac apoptosis and fibrosis has never been evaluated. Therefore, the aim of this study was to investigate the role of HXP in a myocardial infarction (MI) mouse model. The mice were randomly divided into 3 groups and subjected to surgical ligation of the left anterior descending (LAD) coronary artery or sham surgery (n = 6 for each group) and treated with HXP (50 mg/kg/day) or saline by gavage for 2 weeks. At 2 weeks post MI, we found that HXP significantly enhanced myocardial function and attenuated the increase of heart weight index (HWI) and pathological changes in MI mice. RNA-sequencing and KEGG pathway analyses identified 660 differentially expressed genes and multiple enriched signaling pathways including p53 and TGF-β. In support of these findings, HXP attenuated cardiac apoptosis and decreased p53 and Bax protein expression, while increasing Bcl-2 protein expression in cardiac tissues of MI mice. Furthermore, HXP treatment inhibited cardiac fibrosis and significantly down-regulated TGF-β1 protein expression and Smad2/3 phosphorylation in cardiac tissues. In summary, HXP can improve cardiac function in mice after MI by attenuating cardiac apoptosis and fibrosis partly via supression of the p53/Bax/Bcl-2 and TGF-β1/Smad2/3 pathways.

Neural transcription factor Pou4f1 promotes renal fibrosis via macrophage-myofibroblast transition

Unresolved inflammation can lead to tissue fibrosis and impaired organ function. Macrophage-myofibroblast transition (MMT) is one newly identified mechanism by which ongoing chronic inflammation causes progressive fibrosis in different forms of kidney disease. However, the mechanisms underlying MMT are still largely unknown. Here, we discovered a brain-specific homeobox/POU domain protein Pou4f1 (Brn3a) as a specific regulator of MMT. Interestingly, we found that Pou4f1 is highly expressed by macrophages undergoing MMT in sites of fibrosis in human and experimental kidney disease, identified by coexpression of the myofibroblast marker, α-SMA. Unexpectedly, Pou4f1 expression peaked in the early stage in renal fibrogenesis in vivo and during MMT of bone marrow-derived macrophages (BMDMs) in vitro. Mechanistically, chromatin immunoprecipitation (ChIP) assay identified that Pou4f1 is a Smad3 target and the key downstream regulator of MMT, while microarray analysis defined a Pou4f1-dependent fibrogenic gene network for promoting TGF-β1/Smad3-driven MMT in BMDMs at the transcriptional level. More importantly, using two mouse models of progressive renal interstitial fibrosis featuring the MMT process, we demonstrated that adoptive transfer of TGF-β1-stimulated BMDMs restored both MMT and renal fibrosis in macrophage-depleted mice, which was prevented by silencing Pou4f1 in transferred BMDMs. These findings establish a role for Pou4f1 in MMT and renal fibrosis and suggest that Pou4f1 may be a therapeutic target for chronic kidney disease with progressive renal fibrosis.

Aesculetin Attenuates Alveolar Injury and Fibrosis Induced by Close Contact of Alveolar Epithelial Cells with Blood-Derived Macrophages via IL-8 Signaling

Pulmonary fibrosis is a disease in which lung tissues become fibrous and thereby causes severe respiratory disturbances. Various stimuli induce infiltration of macrophages to the respiratory tract, secreting inflammatory cytokines, which subsequently leads to the development of pulmonary fibrosis. Aesculetin, a major component of the sancho tree and chicory, is known to biologically have antioxidant and anti-inflammatory effects. Human alveolar epithelial A549 cells were cultured for 24 h in conditioned media of THP-1 monocyte-derived macrophages (mCM) with 1–20 μM aesculetin. Micromolar aesculetin attenuated the cytotoxicity of mCM containing inflammatory tumor necrosis factor-α (TNF)-α and interleukin (IL)-8 as major cytokines. Aesculetin inhibited alveolar epithelial induction of the mesenchymal markers in mCM-exposed/IL-8-loaded A549 cells (≈47–51% inhibition), while epithelial markers were induced in aesculetin-treated cells subject to mCM/IL-8 (≈1.5–2.3-fold induction). Aesculetin added to mCM-stimulated A549 cells abrogated the collagen production and alveolar epithelial CXC-chemokine receptor 2 (CXCR2) induction. The production of matrix metalloproteinase (MMP) proteins in mCM-loaded A549 cells was reduced by aesculetin (≈52% reduction), in parallel with its increase in tissue inhibitor of metalloproteinases (TIMP) proteins (≈1.8-fold increase). In addition, aesculetin enhanced epithelial induction of tight junction proteins in mCM-/IL-8-exposed cells (≈2.3–2.5-fold induction). The inhalation of polyhexamethylene guanidine (PHMG) in mice accompanied neutrophil predominance in bronchoalveolar lavage fluid (BALF) and macrophage infiltration in alveoli, which was inhibited by orally administrating aesculetin to mice. Treating aesculetin to mice alleviated PHMG-induced IL-8-mediated subepithelial fibrosis and airway barrier disruption. Taken together, aesculetin may antagonize pulmonary fibrosis and alveolar epithelial barrier disruption stimulated by the infiltration of monocyte-derived macrophages, which is typical of PHMG toxicity, involving interaction of IL-8 and CXCR2. Aesculetin maybe a promising agent counteracting macrophage-mediated inflammation-associated pulmonary disorders.

An immunohistochemical prostate cell identification key indicates that aging shifts procollagen 1A1 production from myofibroblasts to fibroblasts in dogs prone to prostate-related urinary dysfunction

Background

The identity and spatial distribution of prostatic cell types has been determined in humans but not in dogs, even though aging- and prostate-related voiding disorders are common in both species and mechanistic factors, such as prostatic collagen accumulation, appear to be shared between species. In this publication we characterize the regional distribution of prostatic cell types in the young intact dog to enable comparisons with human and mice and we examine how the cellular source of procollagen 1A1 changes with age in intact male dogs.

Methods

A multichotomous decision tree involving sequential immunohistochemical stains was validated for use in dog and used to identify specific prostatic cell types and determine their distribution in the capsule, peripheral, periurethral and urethral regions of the young intact canine prostate. Prostatic cells identified using this technique include perivascular smooth muscle cells, pericytes, endothelial cells, luminal, intermediate, and basal epithelial cells, neuroendocrine cells, myofibroblasts, fibroblasts, fibrocytes, and other hematolymphoid cells. To enhance rigor and transparency, all high resolution images (representative images shown in the figures and biological replicates) are available through the GUDMAP database at https://doi.org/10.25548/16-WMM4.

Results

The prostatic peripheral region harbors the largest proportion of epithelial cells. Aging does not change the density of hematolymphoid cells, fibroblasts, and myofibroblasts in the peripheral region or in the fibromuscular capsule, regions where we previously observed aging- and androgen-mediated increases in prostatic collagen abundance Instead, we observed aging-related changes the procollagen 1A1 positive prostatic cell identity from a myofibroblast to a fibroblast.

Conclusions

Hematolymphoid cells and myofibroblasts are often identified as sources of collagen in tissues prone to aging-related fibrosis. We show that these are not the likely sources of pathological collagen synthesis in older intact male dogs. Instead, we identify an aging-related shift in the prostatic cell type producing procollagen 1A1 that will help direct development of cell type and prostate appropriate therapeutics for collagen accumulation.

The myofibroblast at a glance

In 1971, Gabbiani and co-workers discovered and characterized the “modification of fibroblasts into cells which are capable of an active spasm” (contraction) in rat wound granulation tissue and, accordingly, named these cells ‘myofibroblasts’. Now, myofibroblasts are not only recognized for their physiological role in tissue repair but also as cells that are key in promoting the development of fibrosis in all organs. In this Cell Science at a Glance and the accompanying poster, we provide an overview of the current understanding of central aspects of myofibroblast biology, such as their definition, activation from different precursors, the involved signaling pathways and most widely used models to study their function. Myofibroblasts will be placed into context with their extracellular matrix and with other cell types communicating in the fibrotic environment. Furthermore, the challenges and strategies to target myofibroblasts in anti-fibrotic therapies are summarized to emphasize their crucial role in disease progression.

Chitosan hydrogels functionalized with either unfractionated heparin or bemiparin improve diabetic wound healing

Diabetes mellitus causes severe impairment in the cutaneous wound healing process, which has led to extensive research striving to establish new treatments. In this work, we describe the effects of chitosan hydrogels functionalized with either unfractionated heparin or bemiparin (a low molecular weight heparin, LMWH) as topical treatments in an experimental diabetic wound healing model. Although wound morphometry showed similar values at the end of the study, microscopic analyses revealed impaired healing in diabetic animals in terms of inflammation and tissue formation. However, both types of loaded hydrogels accelerated inflammation resolution and improved the epithelialization process, while showing a neodermal thickness similar to that of nondiabetic animals. Immunohistochemistry analyses revealed an intermediate response in macrophage evolution between diabetic and nondiabetic controls in the treated groups, as well as enhanced collagenization and myofibroblast progression patterns. However, these changes were not accompanied by differences among groups in collagen I, III and TGF-β1 gene expression. Functionalized hydrogels improved diabetes-associated impaired wound healing, thus promoting the progression of the process and inducing the formation of high-quality cicatricial tissue. Although the beneficial healing effect observed after topical treatment with chitosan hydrogels loaded with bemiparin or unfractionated heparin was similar, the chitosan hydrogel loaded with bemiparin is the preferred choice as it exhibited high-quality tissue in the neoformed dermal tissue.

A pulsed current electric field alters protein expression creating a wound healing phenotype in human skin cells

Aim: Pulsed current (PC) electric field (EF) devices promote healing in chronic wounds but the underpinning mechanisms are largely unknown. The gap between clinical evidence and mechanistic understanding limits device uptake in clinics. Materials & methods: Migration, proliferation and gene/protein expression profiles were investigated in the presence/absence of PCEF, in skin: keratinocytes (NHK); dermal fibroblasts (HDF); dermal microvascular endothelial cells (HDMEC) and macrophages (THP-1). Results: While PCEF had little effect on migration or proliferation, it significantly altered the expression of 31 genes and the secretion of 7 pro-angiogenic and pro-regenerative growth factors using ELISAs. Conclusion: PCEF significantly altered skin cell genomes/proteomes which provides some evidence of how PCEF devices promote healing of chronic wounds.

Emerging Roles of Matricellular Proteins in Systemic Sclerosis

Systemic sclerosis is a rare chronic heterogenous disease that involves inflammation and vasculopathy, and converges in end-stage development of multisystem tissue fibrosis. The loss of tight spatial distribution and temporal expression of proteins in the extracellular matrix (ECM) leads to progressive organ stiffening, which is a hallmark of fibrotic disease. A group of nonstructural matrix proteins, known as matricellular proteins (MCPs) are implicated in dysregulated processes that drive fibrosis such as ECM remodeling and various cellular behaviors. Accordingly, MCPs have been described in the context of fibrosis in sclerosis (SSc) as predictive disease biomarkers and regulators of ECM synthesis, with promising therapeutic potential. In this present review, an informative summary of major MCPs is presented highlighting their clear correlations to SSc- fibrosis.

Understanding the impact of fibroblast heterogeneity on skin fibrosis

Tissue fibrosis is the deposition of excessive extracellular matrix and can occur as part of the body's natural wound healing process upon injury, or as a consequence of diseases such as systemic sclerosis. Skin fibrosis contributes to significant morbidity due to the prevalence of injuries resulting from trauma and burn. Fibroblasts, the principal cells of the dermis, synthesize extracellular matrix to maintain the skin during homeostasis and also play a pivotal role in all stages of wound healing. Although it was previously believed that fibroblasts are homogeneous and mostly quiescent cells, it has become increasingly recognized that numerous fibroblast subtypes with unique functions and morphologies exist. This Review provides an overview of fibroblast heterogeneity in the mammalian dermis. We explain how fibroblast identity relates to their developmental origin, anatomical site and precise location within the skin tissue architecture in both human and mouse dermis. We discuss current evidence for the varied functionality of fibroblasts within the dermis and the relationships between fibroblast subtypes, and explain the current understanding of how fibroblast subpopulations may be controlled through transcriptional regulatory networks and paracrine communications. We consider how fibroblast heterogeneity can influence wound healing and fibrosis, and how insight into fibroblast heterogeneity could lead to novel therapeutic developments and targets for skin fibrosis. Finally, we contemplate how future studies should be shaped to implement knowledge of fibroblast heterogeneity into clinical practice in order to lessen the burden of skin fibrosis.

Summary: This Review discusses the multifaceted aspects of fibroblast heterogeneity and the different roles of fibroblast subpopulations to help overcome skin scarring and fibrosis.

Deciphering the cellular interplays underlying obesity-induced adipose tissue fibrosis

Obesity originates from an imbalance between caloric intake and energy expenditure that promotes adipose tissue expansion, which is necessary to buffer nutrient excess. Patients with higher visceral fat mass are at a higher risk of developing severe complications such as type 2 diabetes and cardiovascular and liver diseases. However, increased fat mass does not fully explain obesity's propensity to promote metabolic diseases. With chronic obesity, adipose tissue undergoes major remodeling, which can ultimately result in unresolved chronic inflammation leading to fibrosis accumulation. These features drive local tissue damage and initiate and/or maintain multiorgan dysfunction. Here, we review the current understanding of adipose tissue remodeling with a focus on obesity-induced adipose tissue fibrosis and its relevance to clinical manifestations.

The Emerging Role of Innate Immunity in Chronic Kidney Diseases

Renal fibrosis is a common fate of chronic kidney diseases. Emerging studies suggest that unsolved inflammation will progressively transit into tissue fibrosis that finally results in an irreversible end-stage renal disease (ESRD). Renal inflammation recruits and activates immunocytes, which largely promotes tissue scarring of the diseased kidney. Importantly, studies have suggested a crucial role of innate immunity in the pathologic basis of kidney diseases. This review provides an update of both clinical and experimental information, focused on how innate immune signaling contributes to renal fibrogenesis. A better understanding of the underlying mechanisms may uncover a novel therapeutic strategy for ESRD.

Post-Ischemic Renal Fibrosis Progression Is Halted by Delayed Contralateral Nephrectomy: The Involvement of Macrophage Activation

(1) Background: Successful treatment of acute kidney injury (AKI)-induced chronic kidney disease (CKD) is unresolved. We aimed to characterize the time-course of changes after contralateral nephrectomy (Nx) in a model of unilateral ischemic AKI-induced CKD with good translational utility. (2) Methods: Severe (30 min) left renal ischemia-reperfusion injury (IRI) or sham operation (S) was performed in male Naval Medical Research Institute (NMRI) mice followed by Nx or S one week later. Expression of proinflammatory, oxidative stress, injury and fibrotic markers was evaluated by RT-qPCR. (3) Results: Upon Nx, the injured kidney hardly functioned for three days, but it gradually regained function until day 14 to 21, as demonstrated by the plasma urea. Functional recovery led to a drastic reduction in inflammatory infiltration by macrophages and by decreases in macrophage chemoattractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF-α) mRNA and most injury markers. However, without Nx, a marked upregulation of proinflammatory (TNF-α, IL-6, MCP-1 and complement-3 (C3)); oxidative stress (nuclear factor erythroid 2-related factor 2, NRF2) and fibrosis (collagen-1a1 (Col1a1) and fibronectin-1 (FN1)) genes perpetuated, and the injured kidney became completely fibrotic. Contralateral Nx delayed the development of renal failure up to 20 weeks. (4) Conclusion: Our results suggest that macrophage activation is involved in postischemic renal fibrosis, and it is drastically suppressed by contralateral nephrectomy ameliorating progression.

Bad Neighborhood: Fibrotic Stroma as a New Player in Melanoma Resistance to Targeted Therapies

Current treatments for metastatic cutaneous melanoma include immunotherapies and drugs targeting key molecules of the mitogen-activated protein kinase (MAPK) pathway, which is often activated by BRAF driver mutations. Overall responses from patients with metastatic BRAF mutant melanoma are better with therapies combining BRAF and mitogen-activated protein kinase kinase (MEK) inhibitors. However, most patients that initially respond to therapies develop drug resistance within months. Acquired resistance to targeted therapies can be due to additional genetic alterations in melanoma cells and to non-genetic events frequently associated with transcriptional reprogramming and a dedifferentiated cell state. In this second scenario, it is possible to identify pro-fibrotic responses induced by targeted therapies that contribute to the alteration of the melanoma tumor microenvironment. A close interrelationship between chronic fibrosis and cancer has been established for several malignancies including breast and pancreatic cancers. In this context, the contribution of fibrosis to drug adaptation and therapy resistance in melanoma is rapidly emerging. In this review, we summarize recent evidence underlining the hallmarks of fibrotic diseases in drug-exposed and resistant melanoma, including increased remodeling of the extracellular matrix, enhanced actin cytoskeleton plasticity, high sensitivity to mechanical cues, and the establishment of an inflammatory microenvironment. We also discuss several potential therapeutic options for manipulating this fibrotic-like response to combat drug-resistant and invasive melanoma.

Activin-mediated alterations of the fibroblast transcriptome and matrisome control the biomechanical properties of skin wounds

Matrix deposition is essential for wound repair, but when excessive, leads to hypertrophic scars and fibrosis. The factors that control matrix deposition in skin wounds have only partially been identified and the consequences of matrix alterations for the mechanical properties of wounds are largely unknown. Here, we report how a single diffusible factor, activin A, affects the healing process across scales. Bioinformatics analysis of wound fibroblast transcriptome data combined with biochemical and histopathological analyses of wounds and functional in vitro studies identify that activin promotes pro-fibrotic gene expression signatures and processes, including glycoprotein and proteoglycan biosynthesis, collagen deposition, and altered collagen cross-linking. As a consequence, activin strongly reduces the wound and scar deformability, as identified by a non-invasive in vivo method for biomechanical analysis. These results provide mechanistic insight into the roles of activin in wound repair and fibrosis and identify the functional consequences of alterations in the wound matrisome at the biomechanical level.

The relationship between histopathology, gene expression, and biochemical and mechanical properties of wounds is largely unknown. Here, the authors show that activin A alters wound healing at multiple levels by promoting pro-fibrotic gene expression and matrix deposition, thereby affecting biomechanical properties of skin wounds.

Molecular Insights Into Lysyl Oxidases in Cartilage Regeneration and Rejuvenation

Articular cartilage remains among the most difficult tissues to regenerate due to its poor self-repair capacity. The lysyl oxidase family (LOX; also termed as protein-lysine 6-oxidase), mainly consists of lysyl oxidase (LO) and lysyl oxidase-like 1-4 (LOXL1-LOXL4), has been traditionally defined as cuproenzymes that are essential for stabilization of extracellular matrix, particularly cross-linking of collagen and elastin. LOX is essential in the musculoskeletal system, particularly cartilage. LOXs-mediated collagen cross-links are essential for the functional integrity of articular cartilage. Appropriate modulation of the expression or activity of certain LOX members selectively may become potential promising strategy for cartilage repair. In the current review, we summarized the advances of LOX in cartilage homeostasis and functioning, as well as copper-mediated activation of LOX through hypoxia-responsive signaling axis during recent decades. Also, the molecular signaling network governing LOX expression has been summarized, indicating that appropriate modulation of hypoxia-responsive-signaling-directed LOX expression through manipulation of bioavailability of copper and oxygen is promising for further clinical implications of cartilage regeneration, which has emerged as a potential therapeutic approach for cartilage rejuvenation in tissue engineering and regenerative medicine. Therefore, targeted regulation of copper-mediated hypoxia-responsive signalling axis for selective modulation of LOX expression may become potential effective therapeutics for enhanced cartilage regeneration and rejuvenation in future clinical implications.

Intraglomerular Monocyte/Macrophage Infiltration and Macrophage-Myofibroblast Transition during Diabetic Nephropathy Is Regulated by the A2B Adenosine Receptor

Diabetic nephropathy (DN) is considered the main cause of kidney disease in which myofibroblasts lead to renal fibrosis. Macrophages were recently identified as the major source of myofibroblasts in a process known as macrophage–myofibroblast transition (MMT). Adenosine levels increase during DN and in vivo administration of MRS1754, an antagonist of the A_2B adenosine receptor (A_2BAR), attenuated glomerular fibrosis (glomerulosclerosis). We aimed to investigate the association between A_2BAR and MMT in glomerulosclerosis during DN. Kidneys/glomeruli of non-diabetic, diabetic, and MRS1754-treated diabetic (DM+MRS1754) rats were processed for histopathologic, transcriptomic, flow cytometry, and cellular in vitro analyses. Macrophages were used for in vitro cell migration/transmigration assays and MMT studies. In vivo MRS1754 treatment attenuated the clinical and histopathological signs of glomerulosclerosis in DN rats. Transcriptomic analysis demonstrated a decrease in chemokine-chemoattractants/cell-adhesion genes of monocytes/macrophages in DM+MRS1754 glomeruli. The number of intraglomerular infiltrated macrophages and MMT cells increased in diabetic rats. This was reverted by MRS1754 treatment. In vitro cell migration/transmigration decreased in macrophages treated with MRS1754. Human macrophages cultured with adenosine and/or TGF-β induced MMT, a process which was reduced by MRS1754. We concluded that pharmacologic blockade of A_2BAR attenuated some clinical signs of renal dysfunction and glomerulosclerosis, and decreased intraglomerular macrophage infiltration and MMT in DN rats.

Sustained delivery of growth factors with high loading efficiency in a layer by layer assembly

Layer by layer (LBL) assembly has garnered considerable interest due to its ability to generate multifunctional films with high tunability and versatility in terms of substrates and polyelectrolytes, allowing the option to use complex devices and drugs. Polyelectrolytes, such as growth factors (GFs), are essential, but costly, delicate, biological molecules that have been used in various tissue regeneration applications. For this reason, the controlled drug delivery of efficiently loaded GFs via LBL assembly (GF-LBL) can contribute to the establishment of cost-effective biologically triggered biomedical applications. We have developed an LBL method to load GFs (specifically, transforming growth factor beta 1, platelet-derived growth factor ββ, and insulin growth factor 1), with up to 90% efficiency approximately, by gas plasma surface activation and tuning the pH to increase the ionic strength of polyelectrolytes. Poly(styrenesulfonate) (PSS) and poly(ethyleneimine) (PEI) have been used to provide the initial necessary charge for multilayer build-up. Heparin and dextran sulphate have been investigated as counter polyelectrolytes to enhance the activity of GFs by protecting their ligands, where heparin resulted in the highest achievable loading efficiency for all GFs. Oxygen gas plasma and acidic pH levels also resulted in a significant increase in GF loading efficiency. The three GFs were released by diffusion and erosion in a controlled manner over lengthy time scales and the bioactivity was maintained for up to 14 days. When tested as implants in vitro, GF-LBL constructs increased fibroblast proliferation, influenced cell morphology and migration, and enhanced myofibroblast differentiation, indicating that the biological functionalities of the GFs were preserved. In conclusion, this developed LBL assembly method can provide a simple drug delivery system, which may yield more effective applications for tissue regeneration as well as biomedical sciences at large.

Human Organ-Specific 3D Cancer Models Produced by the Stromal Self-Assembly Method of Tissue Engineering for the Study of Solid Tumors

Cancer research has considerably progressed with the improvement of in vitro study models, helping to understand the key role of the tumor microenvironment in cancer development and progression. Over the last few years, complex 3D human cell culture systems have gained much popularity over in vivo models, as they accurately mimic the tumor microenvironment and allow high-throughput drug screening. Of particular interest, in vitrohuman 3D tissue constructs, produced by the self-assembly method of tissue engineering, have been successfully used to model the tumor microenvironment and now represent a very promising approach to further develop diverse cancer models. In this review, we describe the importance of the tumor microenvironment and present the existing in vitro cancer models generated through the self-assembly method of tissue engineering. Lastly, we highlight the relevance of this approach to mimic various and complex tumors, including basal cell carcinoma, cutaneous neurofibroma, skin melanoma, bladder cancer, and uveal melanoma.