title: Tracking of autologous adipose tissue-derived mesenchymal stromal cells with in vivo magnetic resonance imaging and histology after intralesional treatment of artificial equine tendon lesions--a pilot study.
abstract: BACKGROUND
  Adipose tissue-derived mesenchymal stromal cells (AT-MSCs) are frequently used to treat equine tendinopathies. Up to now, knowledge about the fate of autologous AT-MSCs after intralesional injection into equine superficial digital flexor tendons (SDFTs) is very limited. The purpose of this study was to monitor the presence of intralesionally injected autologous AT-MSCs labelled with superparamagnetic iron oxide (SPIO) nanoparticles and green fluorescent protein (GFP) over a staggered period of 3 to 9 weeks with standing magnetic resonance imaging (MRI) and histology.
  
  
  METHODS
  Four adult warmblood horses received a unilateral injection of 10 × 10(6) autologous AT-MSCs into surgically created front-limb SDFT lesions. Administered AT-MSCs expressed lentivirally transduced reporter genes for GFP and were co-labelled with SPIO particles in three horses. The presence of AT-MSCs in SDFTs was evaluated by repeated examinations with standing low-field MRI in two horses and post-mortem in all horses with Prussian blue staining, fluorescence microscopy and with immunofluorescence and immunohistochemistry using anti-GFP antibodies at 3, 5, 7 and 9 weeks after treatment.
  
  
  RESULTS
  AT-MSCs labelled with SPIO particles were detectable in treated SDFTs during each MRI in T2*- and T1-weighted sequences until the end of the observation period. Post-mortem examinations revealed that all treated tendons contained high numbers of SPIO- and GFP-labelled cells.
  
  
  CONCLUSIONS
  Standing low-field MRI has the potential to track SPIO-labelled AT-MSCs successfully. Histology, fluorescence microscopy, immunofluorescence and immunohistochemistry are efficient tools to detect labelled AT-MSCs after intralesional injection into surgically created equine SDFT lesions. Intralesional injection of 10 × 10(6) AT-MSCs leads to the presence of high numbers of AT-MSCs in and around surgically created tendon lesions for up to 9 weeks. Integration of injected AT-MSCs into healing tendon tissue is an essential pathway after intralesional administration. Injection techniques have to be chosen deliberately to avoid reflux of the cell substrate injected. In vivo low-field MRI may be used as a non-invasive tool to monitor homing and engraftment of AT-MSCs in horses with tendinopathy of the SDFT.
authors.affiliation: Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Bünteweg 9, 30559, Hannover, Germany. Florian.Geburek@tiho-hannover.de.
authors.forename: Florian
authors.initials: F
authors.lastname: Geburek
authors.affiliation: Pferdeklink Kirchheim, Nürtinger Straße 200, 73230, Kirchheim unter Teck, Germany. k.mundle@pferdeklinik-kirchheim.de.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Mundle
authors.affiliation: , P.O. Box 1243, 72072, Tübingen, Germany. saco_de@yahoo.de.
authors.forename: Sabine
authors.initials: S
authors.lastname: Conrad
authors.affiliation: Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Bünteweg 9, 30559, Hannover, Germany. maren.hellige@tiho-hannover.de.
authors.forename: Maren
authors.initials: M
authors.lastname: Hellige
authors.affiliation: Pferdeklink Kirchheim, Nürtinger Straße 200, 73230, Kirchheim unter Teck, Germany. dr.walliser@pferdeklinik-kirchheim.de.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Walliser
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112, 3584, CM, Utrecht, The Netherlands. hans.vanschie@utcimaging.com.
authors.forename: Hans T M
authors.initials: HT
authors.lastname: van Schie
authors.affiliation: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112, 3584, CM, Utrecht, The Netherlands. r.vanweeren@uu.nl.
authors.forename: René
authors.initials: R
authors.lastname: van Weeren
authors.affiliation: Institute for Anatomy and Cell Biology, University of Heidelberg, Im Neuenheimer Feld 307, 69120, Heidelberg, Germany. skutella@ana.uni-heidelberg.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Skutella
authors.affiliation: Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Bünteweg 9, 30559, Hannover, Germany. peter.stadler@tiho-hannover.de.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Stadler
mesh_terms: D000818:Animals; D058948:Cell Tracking / Q000379:methods*; D002478:Cells, Cultured; D005260:Female; D049452:Green Fluorescent Proteins / Q000096:biosynthesis; D006734:Horse Diseases / Q000628:therapy*; D006736:Horses; D008279:Magnetic Resonance Imaging; D058185:Magnetite Nanoparticles; D008297:Male; D045164:Mesenchymal Stem Cell Transplantation; D059630:Mesenchymal Stem Cells / Q000502:physiology*; D010865:Pilot Projects; D052256:Tendinopathy / Q000628:therapy / Q000662:veterinary*; D013710:Tendons / Q000473:pathology; D014182:Transplantation, Autologous
chemical_list: D058185:Magnetite Nanoparticles; D049452:Green Fluorescent Proteins
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