title: Anatomic Mesenchymal Stem Cell-Based Engineered Cartilage Constructs for Biologic Total Joint Replacement.
abstract: Cartilage has a poor healing response, and few viable options exist for repair of extensive damage. Hyaluronic acid (HA) hydrogels seeded with mesenchymal stem cells (MSCs) polymerized through UV crosslinking can generate functional tissue, but this crosslinking is not compatible with indirect rapid prototyping utilizing opaque anatomic molds. Methacrylate-modified polymers can also be chemically crosslinked in a cytocompatible manner using ammonium persulfate (APS) and N,N,N',N'-tetramethylethylenediamine (TEMED). The objectives of this study were to (1) compare APS/TEMED crosslinking with UV crosslinking in terms of functional maturation of MSC-seeded HA hydrogels; (2) generate an anatomic mold of a complex joint surface through rapid prototyping; and (3) grow anatomic MSC-seeded HA hydrogel constructs using this alternative crosslinking method. Juvenile bovine MSCs were suspended in methacrylated HA (MeHA) and crosslinked either through UV polymerization or chemically with APS/TEMED to generate cylindrical constructs. Minipig porcine femoral heads were imaged using microCT, and anatomic negative molds were generated by three-dimensional printing using fused deposition modeling. Molded HA constructs were produced using the APS/TEMED method. All constructs were cultured for up to 12 weeks in a chemically defined medium supplemented with TGF-β3 and characterized by mechanical testing, biochemical assays, and histologic analysis. Both UV- and APS/TEMED-polymerized constructs showed increasing mechanical properties and robust proteoglycan and collagen deposition over time. At 12 weeks, APS/TEMED-polymerized constructs had higher equilibrium and dynamic moduli than UV-polymerized constructs, with no differences in proteoglycan or collagen content. Molded HA constructs retained their hemispherical shape in culture and demonstrated increasing mechanical properties and proteoglycan and collagen deposition, especially at the edges compared to the center of these larger constructs. Immunohistochemistry showed abundant collagen type II staining and little collagen type I staining. APS/TEMED crosslinking can be used to produce MSC-seeded HA-based neocartilage and can be used in combination with rapid prototyping techniques to generate anatomic MSC-seeded HA constructs for use in filling large and anatomically complex chondral defects or for biologic joint replacement.
authors.affiliation: 1 McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania , Philadelphia, Pennsylvania.|2 Translational Musculoskeletal Research Center, Philadelphia Veterans Affairs Medical Center , Philadelphia, Pennsylvania.
authors.forename: Vishal
authors.initials: V
authors.lastname: Saxena
authors.affiliation: 1 McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania , Philadelphia, Pennsylvania.|2 Translational Musculoskeletal Research Center, Philadelphia Veterans Affairs Medical Center , Philadelphia, Pennsylvania.|3 Department of Bioengineering, University of Pennsylvania , Philadelphia, Pennsylvania.
authors.forename: Minwook
authors.initials: M
authors.lastname: Kim
authors.affiliation: 1 McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania , Philadelphia, Pennsylvania.|2 Translational Musculoskeletal Research Center, Philadelphia Veterans Affairs Medical Center , Philadelphia, Pennsylvania.
authors.forename: Niobra M
authors.initials: NM
authors.lastname: Keah
authors.affiliation: 1 McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania , Philadelphia, Pennsylvania.|2 Translational Musculoskeletal Research Center, Philadelphia Veterans Affairs Medical Center , Philadelphia, Pennsylvania.
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Neuwirth
authors.affiliation: 1 McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania , Philadelphia, Pennsylvania.|2 Translational Musculoskeletal Research Center, Philadelphia Veterans Affairs Medical Center , Philadelphia, Pennsylvania.
authors.forename: Brendan D
authors.initials: BD
authors.lastname: Stoeckl
authors.affiliation: 1 McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania , Philadelphia, Pennsylvania.|3 Department of Bioengineering, University of Pennsylvania , Philadelphia, Pennsylvania.
authors.forename: Kevin
authors.initials: K
authors.lastname: Bickard
authors.affiliation: 1 McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania , Philadelphia, Pennsylvania.|3 Department of Bioengineering, University of Pennsylvania , Philadelphia, Pennsylvania.
authors.forename: David J
authors.initials: DJ
authors.lastname: Restle
authors.affiliation: 1 McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania , Philadelphia, Pennsylvania.|3 Department of Bioengineering, University of Pennsylvania , Philadelphia, Pennsylvania.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Salowe
authors.affiliation: 1 McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania , Philadelphia, Pennsylvania.|3 Department of Bioengineering, University of Pennsylvania , Philadelphia, Pennsylvania.
authors.forename: Margaret Ye
authors.initials: MY
authors.lastname: Wang
authors.affiliation: 1 McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania , Philadelphia, Pennsylvania.|2 Translational Musculoskeletal Research Center, Philadelphia Veterans Affairs Medical Center , Philadelphia, Pennsylvania.
authors.forename: David R
authors.initials: DR
authors.lastname: Steinberg
authors.affiliation: 1 McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania , Philadelphia, Pennsylvania.|2 Translational Musculoskeletal Research Center, Philadelphia Veterans Affairs Medical Center , Philadelphia, Pennsylvania.|3 Department of Bioengineering, University of Pennsylvania , Philadelphia, Pennsylvania.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Mauck
mesh_terms: D000818:Animals; D019644:Arthroplasty, Replacement, Hip; D002356:Cartilage; D002417:Cattle; D006820:Hyaluronic Acid / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry*; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism; D008689:Methacrylates / Q000737:chemistry; D013552:Swine; D013556:Swine, Miniature; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D020100:Hydrogels; D008689:Methacrylates; C008384:methacrylic acid; D006820:Hyaluronic Acid