-
Journal of the American Society of... Jul 2017Interstitial fibrosis is an important contributor to graft loss in chronic renal allograft injury. Inflammatory macrophages are associated with fibrosis in renal...
Interstitial fibrosis is an important contributor to graft loss in chronic renal allograft injury. Inflammatory macrophages are associated with fibrosis in renal allografts, but how these cells contribute to this damaging response is not clearly understood. Here, we investigated the role of macrophage-to-myofibroblast transition in interstitial fibrosis in human and experimental chronic renal allograft injury. In biopsy specimens from patients with active chronic allograft rejection, we identified cells undergoing macrophage-to-myofibroblast transition by the coexpression of macrophage (CD68) and myofibroblast (-smooth muscle actin [-SMA]) markers. CD68/-SMA cells accounted for approximately 50% of the myofibroblast population, and the number of these cells correlated with allograft function and the severity of interstitial fibrosis. Similarly, in C57BL/6J mice with a BALB/c renal allograft, cells coexpressing macrophage markers (CD68 or F4/80) and -SMA composed a significant population in the interstitium of allografts undergoing chronic rejection. Fate-mapping in Lyz2-Cre/Rosa26-Tomato mice showed that approximately half of -SMA myofibroblasts in renal allografts originated from recipient bone marrow-derived macrophages. Knockout of protected against interstitial fibrosis in renal allografts and substantially reduced the number of macrophage-to-myofibroblast transition cells. Furthermore, the majority of macrophage-to-myofibroblast transition cells in human and experimental renal allograft rejection coexpressed the M2-type macrophage marker CD206, and this expression was considerably reduced in -knockout recipients. In conclusion, our studies indicate that macrophage-to-myofibroblast transition contributes to interstitial fibrosis in chronic renal allograft injury. Moreover, the transition of bone marrow-derived M2-type macrophages to myofibroblasts in the renal allograft is regulated a Smad3-dependent mechanism.
Topics: Allografts; Animals; Cell Transdifferentiation; Chronic Disease; Female; Fibrosis; Humans; Kidney; Kidney Diseases; Kidney Transplantation; Macrophages; Male; Mice; Mice, Inbred C57BL; Myofibroblasts; Postoperative Complications
PubMed: 28209809
DOI: 10.1681/ASN.2016050573 -
Experimental Eye Research Dec 2020Myofibroblasts are alpha-smooth muscle actin (SMA)+ cells that have a critical role in the corneal stromal response to infections, injuries, and surgeries, and which... (Review)
Review
Myofibroblasts are alpha-smooth muscle actin (SMA)+ cells that have a critical role in the corneal stromal response to infections, injuries, and surgeries, and which produce corneal scarring fibrosis when they develop in excess. These contractile and opaque cells-produce large amounts of disordered extracellular matrix (ECM)-and develop from keratocyte-derived corneal fibroblasts or bone marrow-derived fibrocytes, and possibly other cell types, in response to TGFβ1, TGFβ2 and PDGF from the epithelium, tears, endothelium, and other stromal cells. Recent proteomic analyses have revealed that the myofibroblasts that develop from different progenitors aren't interchangeable, but have major differences in protein expression and functions. Absence or defective regeneration of the epithelial basement membrane (EBM) and/or Descemet's basement membrane (DBM) results in development and persistence of myofibroblasts in the corneal stroma. The functions of myofibroblasts in the cornea include production of volume-additive ECM, tissue contraction, production of various growth factors, cytokines and chemokines that regulate stromal cells, including other myofibroblasts, production of collagenases and metalloproteinases involved in tissue remodeling, and the expression of toll-like receptors that likely have critical roles in the clearance of bacteria and viruses causing corneal infections.
Topics: Animals; Cornea; Corneal Diseases; Extracellular Matrix; Fibroblasts; Humans; Myofibroblasts
PubMed: 33010289
DOI: 10.1016/j.exer.2020.108272 -
Journal of Neuroinflammation Nov 2020Macular fibrosis causes irreparable vision loss in neovascular age-related macular degeneration (nAMD) even with anti-vascular endothelial growth factor (VEGF) therapy....
BACKGROUND
Macular fibrosis causes irreparable vision loss in neovascular age-related macular degeneration (nAMD) even with anti-vascular endothelial growth factor (VEGF) therapy. Inflammation is known to play an important role in macular fibrosis although the underlying mechanism remains poorly defined. The aim of this study was to understand how infiltrating macrophages and complement proteins may contribute to macular fibrosis.
METHODS
Subretinal fibrosis was induced in C57BL/6J mice using the two-stage laser protocol developed by our group. The eyes were collected at 10, 20, 30 and 40 days after the second laser and processed for immunohistochemistry for infiltrating macrophages (F4/80 and Iba-1), complement components (C3a and C3aR) and fibrovascular lesions (collagen-1, Isolectin B4 and α-SMA). Human retinal sections with macular fibrosis were also used in the study. Bone marrow-derived macrophages (BMDMs) from C57BL/6J mice were treated with recombinant C3a, C5a or TGF-β for 48 and 96 h. qPCR, Western blot and immunohistochemistry were used to examine the expression of myofibroblast markers. The involvement of C3a-C3aR pathway in macrophage to myofibroblast transition (MMT) and subretinal fibrosis was further investigated using a C3aR antagonist (C3aRA) and a C3a blocking antibody in vitro and in vivo.
RESULTS
Approximately 20~30% of F4/80 (or Iba-1) infiltrating macrophages co-expressed α-SMA in subretinal fibrotic lesions both in human nAMD eyes and in the mouse model. TGF-β and C3a, but not C5a treatment, significantly upregulated expression of α-SMA, fibronectin and collagen-1 in BMDMs. C3a-induced upregulation of α-SMA, fibronectin and collagen-1 in BMDMs was prevented by C3aRA treatment. In the two-stage laser model of induced subretinal fibrosis, treatment with C3a blocking antibody but not C3aRA significantly reduced vascular leakage and Isolectin B4 lesions. The treatment did not significantly alter collagen-1 fibrotic lesions.
CONCLUSIONS
MMT plays a role in macular fibrosis secondary to nAMD. MMT can be induced by TGF-β and C3a but not C5a. Further research is required to fully understand the role of MMT in macular fibrosis. Macrophage to myofibroblast transition (MMT) contributes to subretinal fibrosis. Subretinal fibrosis lesions contain various cell types, including macrophages and myofibroblasts, and are fibrovascular. Myofibroblasts are key cells driving pathogenic fibrosis, and they do so by producing excessive amount of extracellular matrix proteins. We have found that infiltrating macrophages can transdifferentiate into myofibroblasts, a phenomenon termed macrophage to myofibroblast transition (MMT) in macular fibrosis. In addition to TGF-β1, C3a generated during complement activation in CNV can also induce MMT contributing to macular fibrosis. RPE = retinal pigment epithelium. BM = Bruch's membrane. MMT = macrophage to myofibroblast transition. TGFB = transforming growth factor β. a-SMA = alpha smooth muscle actin. C3a = complement C3a.
Topics: Animals; Cells, Cultured; Complement C3a; Female; Fibrosis; Humans; Macrophages; Macular Degeneration; Male; Mice; Mice, Inbred C57BL; Myofibroblasts; Neovascularization, Pathologic; Retina
PubMed: 33239022
DOI: 10.1186/s12974-020-02033-7 -
Cell Reports Feb 2022Intrahepatic cholangiocarcinoma (ICC) contains abundant myofibroblasts derived from hepatic stellate cells (HSCs) through an activation process mediated by TGF-β. To...
Intrahepatic cholangiocarcinoma (ICC) contains abundant myofibroblasts derived from hepatic stellate cells (HSCs) through an activation process mediated by TGF-β. To determine the role of programmed death-ligand 1 (PD-L1) in myofibroblastic activation of HSCs, we disrupted PD-L1 of HSCs by shRNA or anti-PD-L1 antibody. We find that PD-L1, produced by HSCs, is required for HSC activation by stabilizing TGF-β receptors I (TβRI) and II (TβRII). While the extracellular domain of PD-L1 (amino acids 19-238) targets TβRII protein to the plasma membrane and protects it from lysosomal degradation, a C-terminal 260-RLRKGR-265 motif on PD-L1 protects TβRI mRNA from degradation by the RNA exosome complex. PD-L1 is required for HSC expression of tumor-promoting factors, and targeting HSC PD-L1 by shRNA or Cre/loxP recombination suppresses HSC activation and ICC growth in mice. Thus, myofibroblast PD-L1 can modulate the tumor microenvironment and tumor growth by a mechanism independent of immune suppression.
Topics: Animals; B7-H1 Antigen; Cell Movement; Cell Proliferation; Hepatic Stellate Cells; Humans; Liver Neoplasms; Mice; Myofibroblasts; Receptor, Transforming Growth Factor-beta Type I; Receptors, Transforming Growth Factor beta; Signal Transduction; Tumor Microenvironment
PubMed: 35139382
DOI: 10.1016/j.celrep.2022.110349 -
Biochimica Et Biophysica Acta.... Jan 2017Cardiac myofibroblasts play an important role in myocardial remodeling. Although α-smooth muscle actin (α-SMA) expression is the hallmark of mature myofibroblasts, its...
Cardiac myofibroblasts play an important role in myocardial remodeling. Although α-smooth muscle actin (α-SMA) expression is the hallmark of mature myofibroblasts, its role in regulating fibroblast function remains poorly understood. We explore the effects of the matrix environment in modulating cardiac fibroblast phenotype, and we investigate the role of α-SMA in fibroblast function using loss- and gain-of-function approaches. In murine myocardial infarction, infiltration of the infarct border zone with abundant α-SMA-positive myofibroblasts was associated with scar contraction. Isolated cardiac fibroblasts cultured in plates showed high α-SMA expression localized in stress fibers, exhibited activation of focal adhesion kinase (FAK), and synthesized large amounts of extracellular matrix proteins. In contrast, when these cells were cultured in collagen lattices, they exhibited marked reduction of α-SMA expression, negligible FAK activation, attenuated collagen synthesis, and increased transcription of genes associated with matrix metabolism. Transforming Growth Factor-β1-mediated contraction of fibroblast-populated collagen pads was associated with accentuated α-SMA synthesis. In contrast, serum- and basic Fibroblast Growth Factor-induced collagen pad contraction was associated with reduced α-SMA expression. α-SMA siRNA knockdown attenuated contraction of collagen pads populated with serum-stimulated cells. Surprisingly, α-SMA overexpression also reduced collagen pad contraction, suggesting that α-SMA is not sufficient to promote contraction of the matrix. Reduced contraction by α-SMA-overexpressing cells was associated with attenuated proliferative activity, in the absence of any effects on apoptosis. α-SMA may be implicated in contraction and remodeling of the extracellular matrix, but is not sufficient to induce contraction. α-SMA expression may modulate cellular functions, beyond its effects on contractility.
Topics: Actins; Animals; Cells, Cultured; Extracellular Matrix; Female; Fibroblasts; Male; Mice, Inbred C57BL; Myocardial Infarction; Myofibroblasts; Transforming Growth Factor beta1
PubMed: 27825850
DOI: 10.1016/j.bbadis.2016.11.006 -
Cells Jun 2022Fibrosis results from defective wound healing processes often seen after chronic injury and/or inflammation in a range of organs. Progressive fibrotic events may lead to... (Review)
Review
Fibrosis results from defective wound healing processes often seen after chronic injury and/or inflammation in a range of organs. Progressive fibrotic events may lead to permanent organ damage/failure. The hallmark of fibrosis is the excessive accumulation of extracellular matrix (ECM), mostly produced by pathological myofibroblasts and myofibroblast-like cells. The Hippo signaling pathway is an evolutionarily conserved kinase cascade, which has been described well for its crucial role in cell proliferation, apoptosis, cell fate decisions, and stem cell self-renewal during development, homeostasis, and tissue regeneration. Recent investigations in clinical and pre-clinical models has shown that the Hippo signaling pathway is linked to the pathophysiology of fibrotic diseases in many organs including the lung, heart, liver, kidney, and skin. In this review, we have summarized recent evidences related to the contribution of the Hippo signaling pathway in the development of organ fibrosis. A better understanding of this pathway will guide us to dissect the pathophysiology of fibrotic disorders and develop effective tissue repair therapies.
Topics: Fibrosis; Hippo Signaling Pathway; Humans; Myofibroblasts; Protein Serine-Threonine Kinases; Signal Transduction
PubMed: 35805148
DOI: 10.3390/cells11132065 -
Current Opinion in Rheumatology Jan 2013Interest in the myofibroblast as a key player in propagation of chronic progressive fibrosis continues to elicit many publications, with focus on its cellular origins... (Review)
Review
PURPOSE OF REVIEW
Interest in the myofibroblast as a key player in propagation of chronic progressive fibrosis continues to elicit many publications, with focus on its cellular origins and the mechanisms underpinning their differentiation and/or transition. The objective of the review is to highlight this recent progress.
RECENT FINDINGS
The epithelial origin of the myofibroblast in fibrosis has been challenged by recent studies, with the pericyte suggested as a possible precursor instead. Additional signaling pathways, including Notch, Wnt, and hedgehog, are implicated in myofibroblast differentiation. The importance of NADPH oxidase 4 was highlighted recently to suggest a potential link between cellular/oxidative stress and the genesis of the myofibroblast. Recent observations on the importance of lysophosphatidic acid in fibrosis suggest that this may be due, in part, to its ability to regulate myofibroblast differentiation. Finally, there is increasing evidence for the role of epigenetic mechanisms in regulating myofibroblast differentiation, including DNA methylation and miRNA regulation of gene expression.
SUMMARY
These recent discoveries open up a whole new array of potential targets for novel antifibrotic therapies. This is of special importance given the current bleak outlook for chronic progressive fibrotic diseases, such as scleroderma, due to lack of effective therapies.
Topics: Cell Differentiation; Epigenesis, Genetic; Epithelial-Mesenchymal Transition; Fibrosis; Humans; Myofibroblasts; Signal Transduction
PubMed: 23114586
DOI: 10.1097/BOR.0b013e32835b1352 -
The Journal of Clinical Investigation Jan 2018Fibrosis is the excessive accumulation of extracellular matrix that often occurs as a wound healing response to repeated or chronic tissue injury, and may lead to the... (Review)
Review
Fibrosis is the excessive accumulation of extracellular matrix that often occurs as a wound healing response to repeated or chronic tissue injury, and may lead to the disruption of organ architecture and loss of function. Although fibrosis was previously thought to be irreversible, recent evidence indicates that certain circumstances permit the resolution of fibrosis when the underlying causes of injury are eradicated. The mechanism of fibrosis resolution encompasses degradation of the fibrotic extracellular matrix as well as elimination of fibrogenic myofibroblasts through their adaptation of various cell fates, including apoptosis, senescence, dedifferentiation, and reprogramming. In this Review, we discuss the present knowledge and gaps in our understanding of how matrix degradation is regulated and how myofibroblast cell fates can be manipulated, areas that may identify potential therapeutic approaches for fibrosis.
Topics: Animals; Apoptosis; Cell Dedifferentiation; Cellular Reprogramming; Cellular Senescence; Extracellular Matrix; Fibrosis; Humans; Myofibroblasts
PubMed: 29293097
DOI: 10.1172/JCI93563 -
Progress in Biophysics and Molecular... Jul 2019The phenotypic conversion of normal fibroblasts to myofibroblasts is central to normal wound healing and to pathological fibrosis that can occur in the heart and many... (Review)
Review
The phenotypic conversion of normal fibroblasts to myofibroblasts is central to normal wound healing and to pathological fibrosis that can occur in the heart and many other tissues. The transformation occurs in two stages. The first stage is driven mainly by mechanical changes such as increased stiffness of the heart due to hypertension and cellular contractility. The second stage requires both increasing stiffness and biochemical factors such as the growth factor, TGFβ. As more and more cells convert from weakly contractile fibroblasts to strongly contractile myofibroblasts, the stiffness of the ventricular muscle increases. We propose a simple model for the establishment of non-equilibrium steady states with different compositions of fibroblasts and myofibroblasts. Under some conditions a positive feedback loop resulting from the increasing stiffness caused by increasing numbers of myofibroblasts can produce a bifurcation between steady states with low and high myofibroblast content. We illustrate the large mechanical differences between normal fibroblasts and myofibroblasts with measurements in engineered tissue constructs.
Topics: Animals; Biomechanical Phenomena; Feedback, Physiological; Humans; Kinetics; Models, Biological; Myofibroblasts; Phenotype
PubMed: 30174171
DOI: 10.1016/j.pbiomolbio.2018.08.004 -
International Journal of Molecular... Apr 2023Organ fibrosis represents a dysregulated, maladaptive wound repair response that results in progressive disruption of normal tissue architecture leading to detrimental... (Review)
Review
Organ fibrosis represents a dysregulated, maladaptive wound repair response that results in progressive disruption of normal tissue architecture leading to detrimental deterioration in physiological function, and significant morbidity/mortality. Fibrosis is thought to contribute to nearly 50% of all deaths in the Western world with current treatment modalities effective in slowing disease progression but not effective in restoring organ function or reversing fibrotic changes. When physiological wound repair is complete, myofibroblasts are programmed to undergo cell death and self-clearance, however, in fibrosis there is a characteristic absence of myofibroblast apoptosis. It has been shown that in fibrosis, myofibroblasts adopt an apoptotic-resistant, highly proliferative phenotype leading to persistent myofibroblast activation and perpetuation of the fibrotic disease process. Recently, this pathological adaptation has been linked to dysregulated expression of tumour suppressor gene p53. In this review, we discuss p53 dysregulation and apoptotic failure in myofibroblasts and demonstrate its consistent link to fibrotic disease development in all types of organ fibrosis. An enhanced understanding of the role of p53 dysregulation and myofibroblast apoptosis may aid in future novel therapeutic and/or diagnostic strategies in organ fibrosis.
Topics: Humans; Myofibroblasts; Tumor Suppressor Protein p53; Fibrosis; Apoptosis; Wound Healing; Cell Differentiation
PubMed: 37047710
DOI: 10.3390/ijms24076737