Progenitor Cells from Cartilage—No Osteoarthritis-Grade-Specific Differences in Stem Cell Marker Expression Peter Bernstein and Ines Sperling Dept. of Orthopaedics, University Hospital Carl Gustav Carus, 01307 Dresden, Germany Denis Corbeil Tissue Engineering Laboratories, Biotec, Technical University Dresden, 01307 Dresden, Germany Ute Hempel Institute of Physiological Chemistry, Technical University Dresden, 01307 Dresden, Germany Stefan Fickert Sporthopaedicum Straubing-Regensburg, 94315 Straubing, Germany Medical Faculty Mannheim, University of Heidelberg, 68167 Mannheim, Germany DOI 10.1002/btpr.1668 Published online December 20, 2012 in Wiley Online Library (wileyonlinelibrary.com). Tissue engineering efforts for the fabrication of cartilage substitutes head toward applic- ability in osteoarthritis (OA). Progenitor cells can be harvested from the osteoarthritic joint itself, resembling multipotent mesenchymal stromal cells (MSC). Our objective was to ana- lyze MSC characteristics of those cells in respect to the OA-related damage of their harvest site. OA cartilage was obtained from six patients during alloarthroplastic knee surgery, sam- ple grading was done according to Outerbridge’s classification. Upon enzymatic dissocia- tion, primary chondrocytes were expanded in two-dimensional monolayer culture. At distinct cell passages, the process of dedifferentiation was phenotypically monitored; cell surface expression of classical MSC markers was analyzed by flow cytometry. Cells were subjected to chondrogenesis and osteogenesis after their fourth passage. At third passage, 95% of cells became positive for cluster of differentiation (CD)105 and further subclassification revealed that the majority of them were positive for both CD73 and CD90. CD105 þ CD73 þ CD90 þ phenotype meets thus the minimal surface antigen criteria for MSC definition. More than one-third of dedifferentiated chondrocytes displayed a coexpression of CD9 þ CD166 þ CD90 þ and to a lesser extent CD105 þ CD73 þ CD44 þ , irrespective of the stage of the original carti- lage degradation. Finally, we could successfully demonstrate a redifferentiation of these pro- genitors into sulfated glycosaminoglycan producing cells. The basic level of alkaline phosphatase activity could not be enhanced upon osteogenic differentiation. In conclusion, chondrogenic progenitors derived from OA cartilages with low or high Outerbridge’s grade can be seen as a potential cellular source for cartilage replacement. V V C 2012 American Insti- tute of Chemical Engineers Biotechnol. Prog., 29: 206–212, 2013 Keywords: chondrogenic progenitors, dedifferentiation, mesenchymal stromal cell, osteoarthritis, surface markers Introduction Treatment of osteoarthritis (OA) is heading toward regen- erative approaches. From a laboratory-methodological point of view, this encompasses tissue engineering of joint carti- lage. 1–4 However, a limiting factor is the large number of cells needed for defect filling. Whereas in non-OA cases (like traumatic osteochondral defects), cells can be obtained from healthy, nonloaded zones, a major portion of OA-carti- lage has to be regarded as diseased to a more or less account, containing fewer cells for tissue engineering pur- poses. The OA defect itself is often noncontained, broad on the surface, and reaching down into the cartilage–bone inter- face. Cartilage tissue engineering strategies have prompted the use of multipotent mesenchymal stromal cells (MSC) as healthy chondrocytes are of very limited number and are not available in OA joints. 5 MSC can be harvested from multiple remote sites, including fat pads and iliac crest bone marrow. 6 Their multilineage potential has been described. 7 However, stable chondrogenic differentiation has not yet been achieved due to the hypertrophic potential, which leads the cells through the enchondral ossification pathway toward bone formation. 2,8 Joint cartilage’s volume comprises of about 5% cells, which are believed to be terminally differentiated Additional Supporting Information may be found in the online ver- sion of this article. Correspondence concerning this article should be addressed to P. Bernstein at peter.bernstein@uniklinikum-dresden.de. 206 V V C 2012 American Institute of Chemical Engineers