Fibroblasts residing in connective tissues throughout the body are responsible for extracellular matrix (ECM) homeostasis and repair. In response to tissue damage, they activate to become myofibroblasts, which have organized contractile cytoskeletons and produce a myriad of proteins for ECM remodeling. However, persistence of myofibroblasts can lead to fibrosis with excessive collagen deposition and tissue stiffening. Thus, understanding which signals regulate de-activation of myofibroblasts during normal tissue repair is critical. Substrate modulus has recently been shown to regulate fibrogenic properties, proliferation and apoptosis of fibroblasts isolated from different organs. However, few studies track the cellular responses of fibroblasts to dynamic changes in the microenvironmental modulus. Here, we utilized a light-responsive hydrogel system to probe the fate of valvular myofibroblasts when the Young’s modulus of the substrate was reduced from ∼32 kPa, mimicking pre-calcified diseased tissue, to ∼7 kPa, mimicking healthy cardiac valve fibrosa. After softening the substrata, valvular myofibroblasts de-activated with decreases in α-smooth muscle actin (α-SMA) stress fibers and proliferation, indicating a dormant fibroblast state. Gene signatures of myofibroblasts (including α-SMA and connective tissue growth factor (CTGF)) were significantly down-regulated to fibroblast levels within 6 hours of in situ substrate elasticity reduction while a general fibroblast gene vimentin was not changed. Additionally, the de-activated fibroblasts were in a reversible state and could be re-activated to enter cell cycle by growth stimulation and to express fibrogenic genes, such as CTGF, collagen 1A1 and fibronectin 1, in response to TGF-β1. Our data suggest that lowering substrate modulus can serve as a cue to down-regulate the valvular myofibroblast phenotype resulting in a predominantly quiescent fibroblast population. These results provide insight in designing hydrogel substrates with physiologically relevant stiffness to dynamically redirect cell fate in vitro.
Redirecting Valvular Myofibroblasts into Dormant Fibroblasts through Light-mediated Reduction in Substrate Modulus
Huan Wang,S. Haeger,April M. Kloxin,L. Leinwand,K. Anseth
Published 2012 in PLoS ONE
ABSTRACT
PUBLICATION RECORD
- Publication year
2012
- Venue
PLoS ONE
- Publication date
2012-07-13
- Fields of study
Medicine
- Identifiers
- External record
- Source metadata
Semantic Scholar, PubMed
CITATION MAP
EXTRACTION MAP
CLAIMS
CONCEPTS
- collagen 1a1
A collagen gene and matrix component associated with fibrogenic activation in fibroblasts.
Aliases: COL1A1, collagen type I alpha 1
- ctgf
Connective tissue growth factor, a fibrogenic gene and protein measured in the fibroblast-to-myofibroblast program.
Aliases: connective tissue growth factor
- dormant fibroblast state
A quiescent fibroblast-like state associated with reduced contractile and proliferative activity.
Aliases: quiescent fibroblast population, dormant state
- fibronectin 1
A matrix gene and protein associated with extracellular matrix remodeling in fibroblasts.
Aliases: FN1, fibronectin-1
- substrate modulus reduction
An experimental change in the stiffness of the hydrogel substrate from a higher to a lower Young's modulus.
Aliases: softening the substrata, in situ substrate elasticity reduction
- tgf-β1
Transforming growth factor beta 1, a soluble growth factor used to stimulate re-activation and fibrogenic gene expression.
Aliases: TGF-beta1, transforming growth factor beta 1
- valvular myofibroblasts
Activated fibroblast-like cells from cardiac valves that express contractile and matrix-remodeling programs.
Aliases: myofibroblasts
- vimentin
A general fibroblast-associated intermediate filament protein used here as a marker that remained unchanged.
- α-sma
Alpha-smooth muscle actin, a marker of the contractile myofibroblast phenotype.
Aliases: alpha-SMA, ACTA2
- α-sma stress fibers
Actin-based contractile fiber structures marked by alpha-smooth muscle actin in myofibroblasts.
Aliases: alpha-SMA stress fibers, α-smooth muscle actin stress fibers
REFERENCES
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