title: Relative percentage and zonal distribution of mesenchymal progenitor cells in human osteoarthritic and normal cartilage.
abstract: BACKGROUND
  Mesenchymal stem cells (MSC) are highly attractive for use in cartilage regeneration. To date, MSC are usually recruited from subchondral bone marrow using microfracture. Recent data suggest that isolated cells from adult human articular cartilage, which express the combination of the cell-surface markers CD105 and CD166, are multi-potent mesenchymal progenitor cells (MPC) with characteristics similar to MSC. MPC within the cartilage matrix, the target of tissue regeneration, may provide the basis for in situ regeneration of focal cartilage defects. However, there is only limited information concerning the presence/abundance of CD105+/CD166+ MPC in human articular cartilage. The present study therefore assessed the relative percentage and particularly the zonal distribution of cartilage MPC using the markers CD105/CD166.
  
  
  METHODS
  Specimens of human osteoarthritic (OA; n = 11) and normal (n = 3) cartilage were used for either cell isolation or immunohistochemistry. Due to low numbers, isolated cells were expanded for 2 weeks and then analyzed by flow cytometry (FACS) or immunofluorescence in chamber slides for the expression of CD105 and CD166. Following immunomagnetic separation of CD166+/- OA cells, multi-lineage differentiation assays were performed. Also, the zonal distribution of CD166+ cells within the matrix of OA and normal cartilage was analyzed by immunohistochemistry.
  
  
  RESULTS
  FACS analysis showed that 16.7 ± 2.1% (mean ± SEM) of OA and 15.3 ± 2.3 of normal chondrocytes (n.s.) were CD105+/CD166+ and thus carried the established MPC marker combination. Similarly, 13.2% ± 0.9% and 11.7 ± 2.1 of CD105+/CD166+cells, respectively, were identified by immunofluorescence in adherent OA and normal chondrocytes. The CD166+ enriched OA cells showed a stronger induction of the chondrogenic phenotype in differentiation assays than the CD166+ depleted cell population, underlining the chondrogenic potential of the MPC. Strikingly, CD166+ cells in OA and normal articular cartilage sections (22.1 ± 1.7% and 23.6% ± 1.4%, respectively; n.s.) were almost exclusively located in the superficial and middle zone.
  
  
  CONCLUSIONS
  The present results underline the suitability of CD166 as a biomarker to identify and, in particular, localize and/or enrich resident MPC with a high chondrogenic potential in human articular cartilage. The percentage of MPC in both OA and normal cartilage is substantially higher than previously reported, suggesting a yet unexplored reserve capacity for regeneration.
authors.affiliation: Experimental Rheumatology Unit, Department of Orthopedics, University Hospital Jena, Klosterlausnitzer Str, 81, Eisenberg, D-07607, Germany. David.Pretzel@med.uni-jena.de
authors.forename: David
authors.initials: D
authors.lastname: Pretzel
authors.forename: Stefanie
authors.initials: S
authors.lastname: Linss
authors.forename: Steffen
authors.initials: S
authors.lastname: Rochler
authors.forename: Michaela
authors.initials: M
authors.lastname: Endres
authors.forename: Christian
authors.initials: C
authors.lastname: Kaps
authors.forename: Saifeddin
authors.initials: S
authors.lastname: Alsalameh
authors.forename: Raimund W
authors.initials: RW
authors.lastname: Kinne
mesh_terms: D000368:Aged; D015703:Antigens, CD / Q000096:biosynthesis; D002358:Cartilage, Articular / Q000166:cytology* / Q000378:metabolism; D015816:Cell Adhesion Molecules, Neuronal / Q000096:biosynthesis; D019070:Cell Lineage; D002469:Cell Separation; D000071063:Endoglin; D005260:Female; D005326:Fetal Proteins / Q000096:biosynthesis; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism; D020370:Osteoarthritis, Knee; D011956:Receptors, Cell Surface / Q000096:biosynthesis; D020410:Activated-Leukocyte Cell Adhesion Molecule
chemical_list: D015703:Antigens, CD; D015816:Cell Adhesion Molecules, Neuronal; D000071063:Endoglin; D005326:Fetal Proteins; D011956:Receptors, Cell Surface; C105613:ALCAM protein, human; D020410:Activated-Leukocyte Cell Adhesion Molecule; C064206:ENG protein, human