title: Micrometer-sized iron oxide particle labeling of mesenchymal stem cells for magnetic resonance imaging-based monitoring of cartilage tissue engineering.
abstract: OBJECTIVE
  To examine mesenchymal stem cell (MSC) labeling with micrometer-sized iron oxide particles (MPIOs) for magnetic resonance imaging (MRI)-based tracking and its application to monitoring articular cartilage regeneration.
  
  
  METHODS
  Rabbit MSCs were labeled using commercial MPIOs. In vitro MRI was performed with gradient echo (GRE) and spin echo (SE) sequences at 3T and quantitatively characterized using line profile and region of interest analysis. Ex vivo MRI of hydrogel-encapsulated labeled MSCs implanted within a bovine knee was performed with spoiled GRE (SPGR) and T(1ρ) sequences. Fluorescence microscopy, labeling efficiency, and chondrogenesis of MPIO-labeled cells were also examined.
  
  
  RESULTS
  MPIO labeling results in efficient contrast uptake and signal loss that can be visualized and quantitatively characterized via MRI. SPGR imaging of implanted cells results in ex vivo detection within native tissue, and T(1ρ) imaging is unaffected by the presence of labeled cells immediately following implantation. MPIO labeling does not affect quantitative glycosaminoglycan production during chondrogenesis, but iron aggregation hinders extracellular matrix visualization. This aggregation may result from excess unincorporated particles following labeling and is an issue that necessitates further investigation.
  
  
  CONCLUSIONS
  This study demonstrates the promise of MPIO labeling for monitoring cartilage regeneration and highlights its potential in the development of cell-based tissue engineering strategies.
authors.affiliation: MQIR, Department of Radiology, University of California, San Francisco, CA 94158, USA. kjs@berkeley.edu
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Saldanha
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Doan
authors.forename: Kristy M
authors.initials: KM
authors.lastname: Ainslie
authors.forename: Tejal A
authors.initials: TA
authors.lastname: Desai
authors.forename: Sharmila
authors.initials: S
authors.lastname: Majumdar
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology* / Q000254:growth & development*; D002417:Cattle; D058948:Cell Tracking / Q000379:methods; D002478:Cells, Cultured; D005260:Female; D005290:Ferric Compounds; D050724:Fractures, Cartilage / Q000473:pathology* / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D045164:Mesenchymal Stem Cell Transplantation / Q000379:methods; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D008863:Microspheres; D011817:Rabbits; D012038:Regeneration / Q000502:physiology; D013194:Staining and Labeling / Q000379:methods; D023822:Tissue Engineering / Q000379:methods; D016896:Treatment Outcome
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide