scholarly journals Fibroblast to Myofibroblast Transition is Enhanced by Increased Cell Density

Author(s):  
Mary T. Doolin ◽  
Ian M. Smith ◽  
Kimberly M. Stroka

Idiopathic pulmonary fibrosis (IPF) is a chronic disease of the lung caused by a rampant inflammatory response that results in the deposition of excessive extracellular matrix (ECM). IPF patient lungs also develop fibroblastic foci that consist of activated fibroblasts and myofibroblasts. In concert with ECM deposition, the increased cell density within fibroblastic foci imposes confining forces on lung fibroblasts. In this work, we observed that increased cell density increases the incidence of fibroblast to myofibroblast transition (FMT), but mechanical confinement imposed by micropillars has no effect on FMT incidence. We found that human lung fibroblasts (HLFs) express more α-SMA and deposit more collagen matrix, which are both characteristics of myofibroblasts, in response to TGF-β1 when cells were seeded at a high density compared to a medium or a low density. These results support the hypothesis that HLFs undergo FMT more readily in response to TGF-β1 when cells are densely packed, and this effect could be dependent on increased OB-cadherin expression. This work demonstrates that cell density is an important factor to consider when modelling IPF in vitro, and it may suggest decreasing cell density within fibroblastic foci as a strategy to reduce IPF burden.

Inflammation ◽  
2007 ◽  
Vol 30 (5) ◽  
pp. 153-160 ◽  
Author(s):  
Ulrika Zagai ◽  
Elham Dadfar ◽  
Joachim Lundahl ◽  
Per Venge ◽  
C. Magnus Sköld

1999 ◽  
Vol 276 (5) ◽  
pp. L814-L824 ◽  
Author(s):  
Oliver Eickelberg ◽  
Eleonore Köhler ◽  
Frank Reichenberger ◽  
Sybille Bertschin ◽  
Thomas Woodtli ◽  
...  

Increased collagen and extracellular matrix (ECM) deposition within the lung is a characteristic feature of lung fibrosis. Transforming growth factor (TGF)-β isoforms play a pivotal role in the production of collagen and ECM. In this study, we investigated the effects of TGF-β1 and TGF-β3 on the main processes controlling ECM deposition using primary human lung fibroblasts. We analyzed 1) collagen metabolism by [3H]proline incorporation, 2) matrix metalloproteinase (MMP) expression by substrate gel zymography, and 3) tissue inhibitor of metalloproteinases (TIMP) expression by Western blot analysis. TGF-β1 and TGF-β3 increased the percentage of secreted collagens in supernatants of primary fibroblasts from 8.0 ± 1.2 (control) to 23.6 ± 4.6 and 22.3 ± 1.3%, respectively. The collagen percentage in deposited ECM was increased from 5.8 ± 0.3 (control) to 9.0 ± 0.5 and 8.8 ± 0.5% by TGF-β1 and TGF-β3, respectively. Secretion of MMP-1 (interstitial collagenase) by fibroblasts was reduced by both TGF-β isoforms, whereas secretion of MMP-2 (gelatinase A) was unaffected by either of the two isoforms. Both TGF-β isoforms increased TIMP-1 protein expression, whereas TIMP-2 protein was decreased. We thus conclude that TGF-β1 and TGF-β3 are equally potent in increasing ECM deposition. Their fibrotic effect in lung fibroblasts results from 1) an increase in the secretion and deposition of total ECM and collagens, 2) a decrease in MMP-1 secretion, and 3) an increase of TIMP-1 expression.


2020 ◽  
Vol 68 (11) ◽  
pp. 797-811
Author(s):  
Stephen P. Evanko ◽  
Michel D. Gooden ◽  
Inkyung Kang ◽  
Christina K. Chan ◽  
Robert B. Vernon ◽  
...  

Hyaluronan and proteoglycan link protein 1 (HAPLN1) stabilizes interactions between two important extracellular matrix (ECM) macromolecules, versican and hyaluronan, which facilitate proliferation of fibroblasts and their conversion to myofibroblasts. However, the role of HAPLN1 in these events has not been studied. Using immunocytochemistry, cellular and ECM locations of HAPLN1 were evaluated in cultured human lung fibroblasts during proliferation and conversion to myofibroblasts. HAPLN1 localized to pericellular matrices, associating with both versican and hyaluronan in the ECM and on the cell surface. Nuclear and total HAPLN1 immunostaining increased after myofibroblast induction. Confocal microscopy showed HAPLN1 predominant in the ECM under cells while versican predominated above cells. Versican and HAPLN1 were also juxtaposed in columnar inclusions in the cytoplasm and nucleus. Nuclear HAPLN1 staining in interphase cells redistributed to the cytosol during mitosis. In the absence of TGF-β1, addition of exogenous bovine HAPLN1 (together with aggrecan G1) facilitated myofibroblast formation, as seen by significant upregulation of α-smooth muscle actin (SMA) staining, while adding full-length bovine versican had no effect. Increased compaction of hyaluronan-rich ECM suggests that HAPLN1 plus G1 addition affects hyaluronan networks and myofibroblast formation. These observations demonstrate changes in both extracellular and intracellular localization of HAPLN1 during fibroblast proliferation and myofibroblast conversion suggesting a possible role in fibrotic remodeling:


FEBS Open Bio ◽  
2021 ◽  
Author(s):  
Ryota Kikuchi ◽  
Yuki Maeda ◽  
Takao Tsuji ◽  
Kazuhiro Yamaguchi ◽  
Shinji Abe ◽  
...  

2015 ◽  
Vol 309 (8) ◽  
pp. L821-L833 ◽  
Author(s):  
Anurag Mishra ◽  
Todd A. Stueckle ◽  
Robert R. Mercer ◽  
Raymond Derk ◽  
Yon Rojanasakul ◽  
...  

Carbon nanotubes (CNTs) induce rapid interstitial lung fibrosis, but the underlying mechanisms are unclear. Previous studies indicated that the ability of CNTs to penetrate lung epithelium, enter interstitial tissue, and stimulate fibroblasts to produce collagen matrix is important to lung fibrosis. In this study, we investigated the activation of transforming growth factor-β receptor-1 [TGF-β R1; i.e., activin receptor-like kinase 5 (ALK5) receptor] and TGF-β/Smad signaling pathway in CNT-induced collagen production in human lung fibroblasts. Human lung fibroblasts and epithelial cells were exposed to low, physiologically relevant concentrations (0.02–0.6 μg/cm2) of single-walled CNTs (SWCNT) and multiwalled CNTs (MWCNT) in culture and analyzed for collagen, TGF-β1, TGF-β R1, and SMAD proteins by Western blotting and immunofluorescence. Chemical inhibition of ALK5 and short-hairpin (sh) RNA targeting of TGF-β R1 and Smad2 were used to probe the fibrogenic mechanism of CNTs. Both SWCNT and MWCNT induced an overexpression of TGF-β1, TGF-β R1 and Smad2/3 proteins in lung fibroblasts compared with vehicle or ultrafine carbon black-exposed controls. SWCNT- and MWCNT-induced collagen production was blocked by ALK5 inhibitor or shRNA knockdown of TGF-β R1 and Smad2. Our results indicate the critical role of TGF-β R1/Smad2/3 signaling in CNT-induced fibrogenesis by upregulating collagen production in lung fibroblasts. This novel finding may aid in the design of mechanism-based risk assessment and development of rapid screening tests for nanomaterial fibrogenicity.


1969 ◽  
Vol 41 (1) ◽  
pp. 298-311 ◽  
Author(s):  
Tom Elsdale ◽  
Robert Foley

Randomly seeded Petri dish cultures of embryonic human lung fibroblasts generate, in the course of their growth, highly ordered cellular arrangements. Thick, bilaterally symmetrical ridges with an axial polarity and an orthogonal, multilayered internal organization are observed within stationary cultures. The generation of these structures has been investigated. Ridges result from the spontaneous aggregation of cells in postconfluent cultures brought about by directed cell movements. These movements are promoted by the localized production of extracellular matrix sheets containing collagen, which provide new substrates for cellular colonization. Cells that have colonized one matrix substrate may secrete another above themselves, which will in turn be colonized. By a continuation of this cycle, thick stacks consisting of alternate layers of cells and matrix are produced to yield the observed aggregations. The distribution and shape of ridges in a culture imply that matrix substrates are confined to specific locations. The suggested control hypothesis assumes that all the cells in fibroblast cultures are potential producers of a single species of matrix. The serviceability of this matrix as a substrate for cellular colonization, however, is destroyed if the producer cells are motile. Matrix substrates, therefore, are only made by nonmotile cells.


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