title: Covalently tethered TGF-β1 with encapsulated chondrocytes in a PEG hydrogel system enhances extracellular matrix production.
abstract: Healing articular cartilage defects remains a significant clinical challenge because of its limited capacity for self-repair. While delivery of autologous chondrocytes to cartilage defects has received growing interest, combining cell-based therapies with growth factor delivery that can locally signal cells and promote their function is often advantageous. We have previously shown that PEG thiol-ene hydrogels permit covalent attachment of growth factors. However, it is not well known if embedded chondrocytes respond to tethered signals over a long period. Here, chondrocytes were encapsulated in PEG hydrogels functionalized with transforming growth factor-beta 1 (TGF-β1) with the goal of increasing proliferation and matrix production. Tethered TGF-β1 was found to be distributed homogenously throughout the gel, and its bioactivity was confirmed with a TGF-β1 responsive reporter cell line. Relative to solubly delivered TGF-β1, chondrocytes presented with immobilized TGF-β1 showed significantly increased DNA content, and GAG and collagen production over 28 days, while maintaining markers of articular cartilage. These results indicate the potential of thiol-ene chemistry to covalently conjugate TGF-β1 to PEG to locally influence chondrocyte function over 4 weeks. Scaffolds with other or multiple tethered growth factors may prove broadly useful in the design of chondrocyte delivery vehicles for cartilage tissue engineering applications.
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado at Boulder, Boulder, Colorado; Biofrontiers Institute, University of Colorado at Boulder, Boulder, Colorado.
authors.forename: Balaji V
authors.initials: BV
authors.lastname: Sridhar
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Doyle
authors.forename: Mark A
authors.initials: MA
authors.lastname: Randolph
authors.forename: Kristi S
authors.initials: KS
authors.lastname: Anseth
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology / Q000378:metabolism*; D002478:Cells, Cultured; D018914:Cells, Immobilized / Q000166:cytology / Q000378:metabolism; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism*; D003094:Collagen / Q000096:biosynthesis; D005109:Extracellular Matrix / Q000378:metabolism*; D006801:Humans; D055767:Immobilized Proteins / Q000737:chemistry / Q000494:pharmacology; D011092:Polyethylene Glycols / Q000737:chemistry / Q000494:pharmacology; D013552:Swine; D023822:Tissue Engineering / Q000379:methods; D053773:Transforming Growth Factor beta1 / Q000737:chemistry / Q000494:pharmacology
chemical_list: D055767:Immobilized Proteins; C508960:TGFB1 protein, human; D053773:Transforming Growth Factor beta1; D011092:Polyethylene Glycols; D003094:Collagen
keywords: cartilage tissue engineering; chondrocytes; hydrogels; protein conjugation; transforming growth factor-β1