title: Collagen Type II enhances chondrogenic differentiation in agarose-based modular microtissues.
abstract: OBJECTIVE
  Cell-based therapies have made an impact on the treatment of osteoarthritis; however, the repair and regeneration of thick cartilage defects is an important and growing clinical problem. Next-generation therapies that combine cells with biomaterials may provide improved outcomes. We have developed modular microenvironments that mimic the composition of articular cartilage as a delivery system for consistently differentiated cells.
  
  
  METHODS
  Human bone marrow-derived mesenchymal stem cells (MSC) were embedded in modular microbeads consisting of agarose (AG) supplemented with 0%, 10% and 20% collagen Type II (COL-II) using a water-in-oil emulsion technique. AG and AG/COL-II microbeads were characterized in terms of their structural integrity, size distribution and protein content. The viability of embedded MSC and their ability to differentiate into osteogenic, adipogenic and chondrogenic lineages over 3 weeks in culture were also assessed.
  
  
  RESULTS
  Microbeads made with <20% COL-II were robust, generally spheroidal in shape and 80 ± 10 µm in diameter. MSC viability in microbeads was consistently high over a week in culture, whereas viability in corresponding bulk hydrogels decreased with increasing COL-II content. Osteogenic differentiation of MSC was modestly supported in both AG and AG/COL-II microbeads, whereas adipogenic differentiation was strongly inhibited in COL-II containing microbeads. Chondrogenic differentiation of MSC was clearly promoted in microbeads containing COL-II, compared with pure AG matrices.
  
  
  CONCLUSIONS
  Inclusion of collagen Type II in agarose matrices in microbead format can potentiate chondrogenic differentiation of human MSC. Such compositionally tailored microtissues may find utility for cell delivery in next-generation cartilage repair therapies.
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Ramkumar
authors.initials: R
authors.lastname: Tiruvannamalai Annamalai
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Mertz
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Ethan L H
authors.initials: EL
authors.lastname: Daley
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA. Electronic address: jpsteg@umich.edu.
authors.forename: Jan P
authors.initials: JP
authors.lastname: Stegemann
mesh_terms: D001672:Biocompatible Materials / Q000378:metabolism; D002358:Cartilage, Articular / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D064987:Cell- and Tissue-Based Therapy / Q000379:methods*; D002478:Cells, Cultured; D020219:Chondrogenesis / Q000502:physiology*; D024043:Collagen Type II / Q000378:metabolism*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D008863:Microspheres; D010003:Osteoarthritis / Q000628:therapy*; D010012:Osteogenesis / Q000502:physiology*; D012685:Sepharose / Q000737:chemistry; D014945:Wound Healing / Q000502:physiology
chemical_list: D001672:Biocompatible Materials; D024043:Collagen Type II; D012685:Sepharose
keywords: Agarose; Biomaterials; Cartilage tissue engineering; Chondrogenesis; Collagen; Mesenchymal stromal cells; Microencapsulation; Modular tissue engineering