Abstract P485: Loss Of Acta2 In Cardiac Fibroblasts Does Not Prevent The Myofibroblast Differentiation Or Affect The Cardiac Repair After Myocardial Infarction

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Yuxia Li ◽  
Chaoyang Li ◽  
Qianglin Liu ◽  
Leshan Wang ◽  
Adam X Bao ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Cardiac Fibroblasts ◽  
Cardiac Repair ◽  
Fiber Formation ◽  
Stress Fibers ◽  
Myofibroblast Differentiation ◽  
Filamentous Actin ◽  
Actin Isoforms ◽  
Cytoplasmic Actin ◽  
Cardiac Myofibroblasts

In response to myocardial infarction (MI), quiescent cardiac fibroblasts differentiate into myofibroblasts mediating tissue repair in the infarcted area. One of the most widely accepted markers of myofibroblast differentiation is the expression of Acta2 which encodes smooth muscle alpha-actin (SMαA) that is assembled into stress fibers. However, the requirement of Acta2 / SMαA in the myofibroblast differentiation of cardiac fibroblasts and its role in post-MI cardiac repair remained largely unknown. To answer these questions, we generated a tamoxifen-inducible cardiac fibroblast-specific Acta2 knockout mouse line. Surprisingly, mice that lacked Acta2 in cardiac fibroblasts had a normal survival rate after MI. Moreover, Acta2 deletion did not affect the function or overall histology of infarcted hearts. No difference was detected in the proliferation, migration, or contractility between WT and Acta2 -null cardiac myofibroblasts. It was identified that Acta2 -null cardiac myofibroblasts had a normal total filamentous actin level and total actin level. Acta2 deletion caused a unique compensatory increase in the transcription level of Actg2 and an increase in the protein level of sarcomeric actin isoform(s). In addition, the specific muscle actin isoforms that were upregulated in Acta2 -null cardiac myofibroblasts varied between individual cells. Moreover, the formation of stress fibers by cytoplasmic actin isoforms, especially the cytoplasmic gamma-actin, was enhanced in Acta2 -null cardiac myofibroblasts despite their unchanged RNA and protein expression. In conclusion, the deletion of Acta2 does not prevent the myofibroblast differentiation of cardiac fibroblasts or affect the post-MI cardiac repair, and the increased expression and stress fiber formation of non-SMαA actin isoforms and the functional redundancy between actin isoforms are able to compensate for the loss of Acta2 in cardiac myofibroblasts.

scholarly journals Loss of Acta2 in cardiac fibroblasts does not affect myofibroblast differentiation or cardiac repair after myocardial infarction

2021 ◽  
Author(s):  
Yuxia Li ◽  
Chaoyang Li ◽  
Qianglin Liu ◽  
Leshan Wang ◽  
Adam Bao ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Cardiac Fibroblasts ◽  
Cardiac Repair ◽  
Stress Fibers ◽  
Myofibroblast Differentiation ◽  
Filamentous Actin ◽  
Actin Isoforms ◽  
Cytoplasmic Actin ◽  
Alpha Actin ◽  
Cardiac Myofibroblasts

In response to myocardial infarction (MI), quiescent cardiac fibroblasts differentiate into myofibroblasts mediating tissue repair in the infarcted area. One of the most widely accepted markers of myofibroblast differentiation is the expression of Acta2 which encodes smooth muscle alpha-actin (SMαA) that is assembled into stress fibers. However, the requirement of Acta2 in the myofibroblast differentiation of cardiac fibroblasts and its role in post-MI cardiac repair were still not known. To answer these questions, we generated a tamoxifen-inducible cardiac fibroblast-specific Acta2 knockout mouse line. Surprisingly, mice that lacked Acta2 in cardiac fibroblasts had a normal survival rate after MI. Moreover, Acta2 deletion did not affect the function or overall histology of infarcted hearts. No difference was detected in the proliferation, migration, or contractility between WT cardiac fibroblasts and Acta2-null cardiac myofibroblasts. Additional analysis identified that Acta2-null cardiac myofibroblasts had a normal total filamentous actin level and total actin level. Acta2 deletion caused a unique compensatory increase in the transcription level of Actg2 and a possible increase in the protein abundance of cytoplasmic actin isoforms. In conclusion, SMαA stress fibers are not required for myofibroblast differentiation of cardiac fibroblasts or the post-MI cardiac repair, and the increase in the expression of non-SMαA actin isoforms and the functional redundancy between actin isoforms are likely able to compensate for the loss of Acta2 in cardiac myofibroblasts.

scholarly journals Delayed stress fiber formation mediates pulmonary myofibroblast differentiation in response to TGF-β

2011 ◽  
Vol 301 (5) ◽  
pp. L656-L666 ◽  
Author(s):  
Nathan Sandbo ◽  
Andrew Lau ◽  
Jacob Kach ◽  
Caitlyn Ngam ◽  
Douglas Yau ◽  
...  
Keyword(s):  
Rho Kinase ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Stress Fibers ◽  
Nuclear Accumulation ◽  
Myofibroblast Differentiation ◽  
Latrunculin B ◽  
Stress Fiber Formation ◽  
Actin Expression ◽  
Actin Stress Fibers

Myofibroblast differentiation induced by transforming growth factor-β (TGF-β) and characterized by de novo expression of smooth muscle (SM)-specific proteins is a key process in wound healing and in the pathogenesis of fibrosis. We have previously shown that TGF-β-induced expression and activation of serum response factor (SRF) is required for this process. In this study, we examined the signaling mechanism for SRF activation by TGF-β as it relates to pulmonary myofibroblast differentiation. TGF-β stimulated a profound, but delayed (18–24 h), activation of Rho kinase and formation of actin stress fibers, which paralleled SM α-actin expression. The translational inhibitor cycloheximide blocked these processes without affecting Smad-dependent gene transcription. Inhibition of Rho kinase by Y-27632 or depolymerization of actin by latrunculin B resulted in inhibition TGF-β-induced SRF activation and SM α-actin expression, having no effect on Smad signaling. Conversely, stabilization of actin stress fibers by jasplakinolide was sufficient to drive these processes in the absence of TGF-β. TGF-β promoted a delayed nuclear accumulation of the SRF coactivator megakaryoblastic leukemia-1 (MKL1)/myocardin-related transcription factor-A, which was inhibited by latrunculin B. Furthermore, TGF-β also induced MKL1 expression, which was inhibited by latrunculin B, by SRF inhibitor CCG-1423, or by SRF knockdown. Together, these data suggest a triphasic model for myofibroblast differentiation in response to TGF-β that involves 1) initial Smad-dependent expression of intermediate signaling molecules driving Rho activation and stress fiber formation, 2) nuclear accumulation of MKL1 and activation of SRF as a result of actin polymerization, and 3) SRF-dependent expression of MKL1, driving further myofibroblast differentiation.

Calponin 1 contributes to myofibroblast differentiation of human pleural mesothelial cells

2022 ◽  
Author(s):  
Young-yeon Choo ◽  
Tsuyoshi Sakai ◽  
Satoshi Komatsu ◽  
Reiko Ikebe ◽  
Ann Jeffers ◽  
...  
Keyword(s):  
Contractile Activity ◽  
Focal Adhesions ◽  
Scar Tissue ◽  
Mesothelial Cells ◽  
Fiber Formation ◽  
Stress Fibers ◽  
Myofibroblast Differentiation ◽  
Mesenchymal Transition ◽  
Pleural Mesothelial Cells ◽  
Pleural Fibrosis

Pleural mesothelial cells (PMCs) can become myofibroblasts via mesothelial-mesenchymal transition (MesoMT) and contribute to pleural organization, fibrosis, and rind formation. However, how these transformed mesothelial cells contribute to lung fibrosis remains unclear. Here, we investigated the mechanism of contractile myofibroblast differentiation of PMCs. TGF-b induced marked upregulation of calponin 1 expression, which was correlated with notable cytoskeletal rearrangement in human PMCs (HPMCs) to produce stress fibers. Downregulation of calponin 1 expression reduced stress fiber formation. Interestingly, induced stress fibers predominantly contain αSMA associated with calponin 1 but not b-actin. Calponin 1 associated stress fibers also contained myosin II and α-actinin. Further, focal adhesions were aligned with the produced stress fibers. These results suggest that calponin 1 facilitates formation of stress fibers that resemble contractile myofibrils. Supporting this notion, TGF-b significantly increased the contractile activity of HPMCs, an effect that was abolished by downregulation of calponin 1 expression. We infer that differentiation of HPMCs to contractile myofibroblasts facilitates stiffness of scar tissue in pleura to promote pleural fibrosis and that upregulation of calponin 1 plays a central role in this process.

scholarly journals In vivo combinatory gene therapy synergistically promotes cardiac function and vascular regeneration following myocardial infarction

2020 ◽  
Vol 11 ◽  
pp. 204173142095341
Author(s):  
Sunghun Lee ◽  
Bong-Woo Park ◽  
Yong Jin Lee ◽  
Kiwon Ban ◽  
Hun-Jun Park
Keyword(s):  
Myocardial Infarction ◽  
Gene Therapy ◽  
Transcription Factors ◽  
Heart Function ◽  
Cardiac Fibroblasts ◽  
Capillary Density ◽  
Cardiac Repair ◽  
Vascular Regeneration ◽  
Intramyocardial Delivery

Since myocardial infarction (MI) excessively damage the myocardium and blood vessels, the therapeutic approach for treating MI hearts should simultaneously target these two major components in the heart to achieve comprehensive cardiac repair. Here, we investigated a combinatory platform of ETV2 and Gata4, Mef2c and Tbx5 (GMT) transcription factors to develop a strategy that can rejuvenate both myocardium and vasculatures together in MI hearts. Previously ETV2 demonstrated significant effects on neovascularization and GMT was known to directly reprogram cardiac fibroblasts into cardiomyocytes under in vivo condition. Subsequently, intramyocardial delivery of a combination of retroviral GMT and adenoviral ETV2 particles into the rat MI hearts significantly increased viable myocardium area, capillary density compared to ETV2 or GMT only treated hearts, leading to improved heart function and reduced scar formation. These results demonstrate that this combinatorial gene therapy can be a promising approach to enhance the cardiac repair in MI hearts.

scholarly journals Infarct Collagen Topography Regulates Fibroblast Fate via p38-Yes-Associated Protein Transcriptional Enhanced Associate Domain Signals

2020 ◽  
Vol 127 (10) ◽  
pp. 1306-1322
Author(s):  
Darrian Bugg ◽  
Ross Bretherton ◽  
Peter Kim ◽  
Emily Olszewski ◽  
Abigail Nagle ◽  
...  
Keyword(s):  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Phenotypic Diversity ◽  
Cardiac Fibroblasts ◽  
Focal Adhesions ◽  
Cardiac Fibroblast ◽  
Stress Fibers ◽  
Mouse Heart ◽  
Myofibroblast Differentiation ◽  
Collagen Organization

Rationale: Myocardial infarction causes spatial variation in collagen organization and phenotypic diversity in fibroblasts, which regulate the heart’s ECM (extracellular matrix). The relationship between collagen structure and fibroblast phenotype is poorly understood but could provide insights regarding the mechanistic basis for myofibroblast heterogeneity in the injured heart. Objective: To investigate the role of collagen organization in cardiac fibroblast fate determination. Methods and Results: Biomimetic topographies were nanofabricated to recapitulate differential collagen organization in the infarcted mouse heart. Here, adult cardiac fibroblasts were freshly isolated and cultured on ECM topographical mimetics for 72 hours. Aligned mimetics caused cardiac fibroblasts to elongate while randomly organized topographies induced circular morphology similar to the disparate myofibroblast morphologies measured in vivo. Alignment cues also induced myofibroblast differentiation, as >60% of fibroblasts formed αSMA (α-smooth muscle actin) stress fibers and expressed myofibroblast-specific ECM genes like Postn (periostin). By contrast, random organization caused 38% of cardiac fibroblasts to express αSMA albeit with downregulated myofibroblast-specific ECM genes. Coupling topographical cues with the profibrotic agonist, TGFβ (transforming growth factor beta), additively upregulated myofibroblast-specific ECM genes independent of topography, but only fibroblasts on flat and randomly oriented mimetics had increased percentages of fibroblasts with αSMA stress fibers. Increased tension sensation at focal adhesions induced myofibroblast differentiation on aligned mimetics. These signals were transduced by p38-YAP (yes-associated protein)-TEAD (transcriptional enhanced associate domain) interactions, in which both p38 and YAP-TEAD (yes-associated protein transcriptional enhanced associate domain) binding were required for myofibroblast differentiation. By contrast, randomly oriented mimetics did not change focal adhesion tension sensation or enrich for p38-YAP-TEAD interactions, which explains the topography-dependent diversity in fibroblast phenotypes observed here. Conclusions: Spatial variations in collagen organization regulate cardiac fibroblast phenotype through mechanical activation of p38-YAP-TEAD signaling, which likely contribute to myofibroblast heterogeneity in the infarcted myocardium.

scholarly journals Inhibition of stress fiber formation preserves blood–brain barrier after intracerebral hemorrhage in mice

2016 ◽  
Vol 38 (1) ◽  
pp. 87-102 ◽  
Author(s):  
Anatol Manaenko ◽  
Peng Yang ◽  
Derek Nowrangi ◽  
Enkhjargal Budbazar ◽  
Richard E Hartman ◽  
...  
Keyword(s):  
Intracerebral Hemorrhage ◽  
Brain Edema ◽  
Blood Brain Barrier ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Stress Fibers ◽  
Brain Barrier ◽  
Filamentous Actin ◽  
Stress Fiber Formation ◽  
Blood Brain

Intracerebral hemorrhage (ICH) represents the deadliest subtype of all strokes. The development of brain edema, a consequence of blood–brain barrier (BBB) disruption, is the most life-threatening event after ICH. Pathophysiological conditions activate the endothelium, one of the components of BBB, inducing rearrangement of the actin cytoskeleton. Upon activation, globular actin assembles into a filamentous actin resulting in the formation of contractile actin bundles, stress fibers. The contraction of stress fibers leads to the formation of intercellular gaps between endothelial cells increasing the permeability of BBB. In the present study, we investigated the effect of ICH on stress fiber formation in CD1 mice. We hypothesized that ICH-induced formation of stress fiber is triggered by the activation of PDGFR-β and mediated by the cortactin/RhoA/LIMK pathway. We demonstrated that ICH induces formation of stress fibers. Furthermore, we demonstrated that the inhibition of PDGFR-β and its downstream reduced the number of stress fibers, preserving BBB and resulting in the amelioration of brain edema and improvement of neurological functions in mice after ICH.

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