title: In Vivo MRI Tracking of Polyethylenimine-Wrapped Superparamagnetic Iron Oxide Nanoparticle-Labeled BMSCs for Cartilage Repair: A Minipig Model.
abstract: OBJECTIVE
  To evaluate the feasibility of tracking polyethylenimine (PEI)-wrapped superparamagnetic iron oxide (SPIO) nanoparticle-labeled, bone marrow-derived mesenchymal stem cells (BMSCs) by in vivo magnetic resonance imaging (MRI) in articular cartilage repair in a minipig model.
  
  
  METHODS
  Eighteen Guizhou minipigs were randomly divided into three groups (groups A, B, and C). In group A, PEI-wrapped SPIO nanoparticle (PEI/SPIO) and green fluorescent protein (GFP) colabeled, autologous BMSCs seeded in type II collagen gel were transplanted into the articular cartilage defects of the minipig model. In group B, GFP-labeled, autologous BMSCs seeded in type II collagen gel were transplanted. In group C, no treatment was applied for cartilage defects. All minipigs underwent clinical 3.0-T MR imaging at 4, 8, 12, and 24 weeks postsurgery. The findings were compared histologically.
  
  
  RESULTS
  Prussian staining and transmission electron microscope showed that BMSCs were efficiently labeled by PEI/SPIO. Cell viability, proliferation, and differentiation were comparable between labeled and unlabeled cells. MRI SET2WI sequence revealed that marked hypointense signal void areas representing the transplanted labeled BMSCs could be observed for at least 24 weeks. Histochemical staining confirmed the presence of Prussian blue-positive cells and GFP-positive cells at the hypointense signal void areas. At 24 weeks postsurgery, both MR signals and histologic staining of minipigs in groups A and B at the cartilage defect were close to the normal cartilage.
  
  
  CONCLUSIONS
  3.0-T MRI in vivo tracking of PEI/SPIO-labeled BMSCs seeded in type II collagen gel on cartilage repair following transplantation is feasible in minipigs.
authors.affiliation: Center of Joint Surgery, Southwest Hospital, The Third Military Medical University, Chongqing, China.
authors.forename: Jiarong
authors.initials: J
authors.lastname: Chen
authors.affiliation: Center of Joint Surgery, Southwest Hospital, The Third Military Medical University, Chongqing, China.
authors.forename: Fuyou
authors.initials: F
authors.lastname: Wang
authors.affiliation: Center of Joint Surgery, Southwest Hospital, The Third Military Medical University, Chongqing, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Orthopedics, Haikou Hospital, Xiangya Medical College, Central South University, Hainan, China.
authors.forename: Xuhong
authors.initials: X
authors.lastname: Jin
authors.affiliation: Department of Radiology, Southwest Hospital, The Third Military Medical University, Chongqing, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Center of Joint Surgery, Southwest Hospital, The Third Military Medical University, Chongqing, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Center of Joint Surgery, Southwest Hospital, The Third Military Medical University, Chongqing, China.
authors.forename: Liu
authors.initials: L
authors.lastname: Yang
keywords: bone marrow mesenchymal stem cells; cartilage repair; green fluorescent protein; magnetic resonance imaging; superparamagnetic iron oxide