title: Hydrogels with differential and patterned mechanics to study stiffness-mediated myofibroblastic differentiation of hepatic stellate cells.
abstract: The differentiation of hepatic stellate cells (HSCs) into myofibroblasts is a key event in liver fibrosis. Due to the local stiffening of the extracellular matrix (ECM) during fibrosis, it is of great interest to develop mimics that can be used to investigate the cellular response to changes in mechanics. Here, we used a step-wise hydrogel crosslinking technique, where macromolecules are crosslinked using a sequence of addition then UV light-mediated radical crosslinking, to generate hydrogels with tunable stiffness. Freshly isolated HSCs remained rounded with lipid droplets and high levels of PPARγ expression on soft substrates (E~2kPa); however, HSCs spread, lost their lipid droplets, and expressed high levels of α-smooth muscle actin (α-SMA) and type I collagen on stiff substrates (E~24kPa). Similarly, fully differentiated cells reverted to a quiescent state when plated on soft substrates. Stiffness-induced differentiation of HSCs was enhanced in the presence of exogenous TGF-β1, a dominant signal in fibrosis. When the UV-induced secondary crosslinking was restricted with a photomask to spatially control mechanics, HSCs responded based on the local hydrogel stiffness, although they remained quiescent on stiff substrates if the stiff feature size was not sufficient to allow cell spreading. This hydrogel system permits the investigation of HSC response to materials with diverse levels and spatially heterogeneous mechanical properties.
authors.affiliation: Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Murat
authors.initials: M
authors.lastname: Guvendiren
authors.affiliation: Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Maryna
authors.initials: M
authors.lastname: Perepelyuk
authors.affiliation: Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address: rgwells@mail.med.upenn.edu.
authors.forename: Rebecca G
authors.initials: RG
authors.lastname: Wells
authors.affiliation: Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address: burdick2@seas.upenn.edu.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Burdick
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects*; D055119:Elastic Modulus / Q000187:drug effects; D055166:Hepatic Stellate Cells / Q000166:cytology* / Q000187:drug effects*; D006820:Hyaluronic Acid / Q000737:chemistry; D020100:Hydrogels / Q000737:chemistry / Q000494:pharmacology*; D008103:Liver Cirrhosis / Q000473:pathology; D055595:Mechanical Phenomena; D008689:Methacrylates / Q000737:chemistry; D058628:Myofibroblasts / Q000166:cytology* / Q000187:drug effects; D047495:PPAR gamma / Q000494:pharmacology; D051381:Rats; D013438:Sulfhydryl Compounds / Q000737:chemistry; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology
chemical_list: D020100:Hydrogels; D008689:Methacrylates; D047495:PPAR gamma; D013438:Sulfhydryl Compounds; D053773:Transforming Growth Factor beta1; D006820:Hyaluronic Acid