title: In vivo MR imaging tracking of magnetic iron oxide nanoparticle labeled, engineered, autologous bone marrow mesenchymal stem cells following intra-articular injection.
abstract: OBJECTIVE
  To track superparamagnetic iron oxide nanoparticle (SPIO)-labeled, bone-derived mesenchymal stem cells (MSCs) by in vivo magnetic resonance imaging (MRI) with a 1.5T-system following injection of engineered autologous MSCs into the knee joint cavity in rabbit articular cartilage defect models.
  
  
  METHODS
  Rabbit MSCs were labeled with SPIO and a transfection agent. Cell viability, proliferation and differentiation capacity were assessed in vitro using appropriate functional assays. Cells underwent GRE T2*-weighted MRI in vitro. The autologous MSCs seeded in chitosan and glycerophosphate (C-GP) gel were injected into the knee joint cavity of rabbit models for cartilage defects. All rabbits underwent GRE T2*-weighted MRI 1, 4, 8 and 12 weeks post-injection. MR imaging findings were compared histologically.
  
  
  RESULTS
  Nanoparticles were stained with Prussian blue and observed by transmission electron microscopy inside the cells. Cell viability, proliferation, and differentiation were comparable between labeled and non-labeled cells. After intra-articular injection of labeled autologous MSCs, marked hypointense signal void areas representing the injected MSCs can be observed for at least 12 weeks on GRE T2*-weighted images. At 12 weeks post-injection, labeled MSCs migrated into the synovial fluid at the suprapatellar bursa, the popliteal space site and subchondral bone of the femur but no MSCs were detected in the defect. Histochemical staining confirmed the presence of Prussian blue-positive cells and BrdU-positive cells.
  
  
  CONCLUSIONS
  MRI would be an efficient noninvasive technique to visually track SPIO-labeled seed cells in vivo; the engineered autologous MSCs do not actively participate in the repair of articular cartilage defects following intra-articular injection.
authors.affiliation: Center of Joint Surgery, Southwest Hospital, The Third Military Medical University, Chongqing, China.
authors.forename: Xu-hong
authors.initials: XH
authors.lastname: Jing
authors.forename: Liu
authors.initials: L
authors.lastname: Yang
authors.forename: Xiao-jun
authors.initials: XJ
authors.lastname: Duan
authors.forename: Bing
authors.initials: B
authors.lastname: Xie
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Zhong
authors.initials: Z
authors.lastname: Li
authors.forename: Hong-bo
authors.initials: HB
authors.lastname: Tan
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000293:injuries*; D049109:Cell Proliferation; D004195:Disease Models, Animal; D005290:Ferric Compounds; D007270:Injections, Intra-Articular; D007592:Joint Diseases / Q000175:diagnosis* / Q000628:therapy; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D045164:Mesenchymal Stem Cell Transplantation / Q000379:methods*; D059630:Mesenchymal Stem Cells; D053758:Nanoparticles; D011817:Rabbits; D023822:Tissue Engineering; D014182:Transplantation, Autologous
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide