title: In vivo chondrogenesis of mesenchymal stem cells in a photopolymerized hydrogel.
abstract: BACKGROUND
  Surgical options for cartilage reconstruction can be significantly improved through advances in cartilage tissue engineering, whereby functional tissue replacements are created by growing cells on polymer scaffolds. The objective of this study was to use a photopolymerizable hydrogel to implant bone marrow-derived mesenchymal stem cells subcutaneously in a minimally invasive manner and promote cartilage tissue formation by the cells in vivo.
  
  
  METHODS
  Athymic nude mice were injected subcutaneously with polymer solutions of poly(ethylene) oxide diacrylate containing mesenchymal stem cells and placed under a UVA lamp to transdermally photopolymerize (solidify) the injected liquid. Experimental groups included polymer solutions with hyaluronic acid (HA), transforming growth factor (TGF)-beta3, or both. After 3 weeks of implantation, cartilage formation was evaluated by gene expression analysis and histologic techniques.
  
  
  RESULTS
  Hyaluronic acid increased the viscosity of the polymer solutions, which helped maintain the injections at the desired site during photopolymerization. Mesenchymal stem cells in hydrogels containing both HA and TGF-beta3 produced the highest quality cartilage, based on expression of the cartilage-specific genes and production of proteoglycan and collagen II. When used independently, TGF-beta3 and HA alone induced cartilage-specific gene expression and collagen type II production; however, TGF-beta3 was essential for proteoglycan production. HA enhanced proteoglycan production when combined with TGF-beta3 and reduced expression and production of collagen I.
  
  
  CONCLUSIONS
  This study is the first to demonstrate the minimally invasive implantation and subsequent chondrogenic differentiation of mesenchymal stem cells in the subcutaneous environment. This lays the foundation for further optimization of a novel and practical technology for cartilage reconstruction.
authors.affiliation: Baltimore, Md. From the Departments of Biomedical Engineering and Plastic and Reconstructive Surgery, The Johns Hopkins University.
authors.forename: Blanka
authors.initials: B
authors.lastname: Sharma
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Williams
authors.forename: Mehnaz
authors.initials: M
authors.lastname: Khan
authors.forename: Paul
authors.initials: P
authors.lastname: Manson
authors.forename: Jennifer H
authors.initials: JH
authors.lastname: Elisseeff
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D020219:Chondrogenesis; D020100:Hydrogels; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D051379:Mice; D008819:Mice, Nude; D011092:Polyethylene Glycols / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D020100:Hydrogels; C437167:poly(ethylene glycol)diacrylate; D011092:Polyethylene Glycols