title: Effect of substrate stiffness on pulmonary fibroblast activation by TGF-β.
abstract: Peptide crosslinkers containing the sequence C-X-CG (X represents various adhesive peptides) were incorporated into poly(ethylene glycol) (PEG) hydrogel networks with different mechanical properties. Pulmonary fibroblasts (PFs) exhibit increased adhesion to rigid hydrogels modified with X=RGDS, DGEA and IKVAV (0.5 and/or 5 mM) compared with a scrambled control (X=HRPNS). PFs exhibit increased adhesion to softer hydrogels when X=DGEA at low (0.5 mM) peptide concentration. PFs seeded onto hydrogels modified with X=RGDS produce alpha-smooth muscle actin (α-SMA), a myofibroblast marker, and form an extensive cytoskeleton with focal adhesions. Decreasing substrate stiffness (achieved through hydrolytic degradation) results in down-regulation of α-SMA expression by PFs. Substrate stiffness increases the sensitivity of PFs to exogenously applied transforming growth factor beta (TGF-β1); PFs on the most rigid gels (E=900 kPa) express α-SMA when treated with low concentrations of TGF-β1 (1 ng ml(-1)), while those on less rigid gels (E=20-60 kPa) do not. These results demonstrate the importance of both mechanical and chemical cues in studying pulmonary fibroblast activation, and establish PEG hydrogels as a viable material for further study of IPF etiology.
authors.affiliation: Biomedical Engineering Interdepartmental Program, University of California, Los Angeles, 90095, USA.
authors.forename: H N
authors.initials: HN
authors.lastname: Chia
authors.forename: M
authors.initials: M
authors.lastname: Vigen
authors.forename: A M
authors.initials: AM
authors.lastname: Kasko
mesh_terms: D000199:Actins / Q000378:metabolism; D000327:Adsorption / Q000187:drug effects; D000595:Amino Acid Sequence; D002448:Cell Adhesion / Q000187:drug effects; D002450:Cell Communication / Q000187:drug effects; D002452:Cell Count; D002454:Cell Differentiation / Q000187:drug effects; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry* / Q000494:pharmacology; D008168:Lung / Q000166:cytology*; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D010641:Phenotype; D011092:Polyethylene Glycols / Q000494:pharmacology; D013314:Stress, Mechanical; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*
chemical_list: C541116:ACTA2 protein, human; D000199:Actins; D010455:Peptides; D053773:Transforming Growth Factor beta1; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011092:Polyethylene Glycols