Plasticity of clonal populations of dedifferentiated adult human articular chondrocytes.
OBJECTIVE
To investigate whether adult human articular chondrocytes (AHACs), dedifferentiated by monolayer expansion, can differentiate toward diverse mesenchymal lineages and, if so, whether this ability is regulated by growth factors during monolayer expansion.


METHODS
AHACs were expanded as multiclonal or clonal populations in medium without (control) or with factors enhancing cell dedifferentiation (transforming growth factor beta1, fibroblast growth factor 2, and platelet-derived growth factor type BB [TFP]). Cells were then cultured under conditions promoting chondrogenic, osteogenic, or adipogenic differentiation, and the acquired phenotypes were assessed histologically, biochemically, and by real-time reverse transcriptase-polymerase chain reaction.


RESULTS
Multiclonal populations of both control- and TFP-expanded AHACs differentiated toward the chondrogenic, osteogenic, and adipogenic lineages. Compared with control-expanded AHACs, TFP-expanded cells displayed enhanced chondrogenic differentiation capacity (2.4-fold higher glycosaminoglycan/DNA content and 2,500-fold higher up-regulation of type II collagen) and osteogenic differentiation capacity (9.4-fold higher increase in alkaline phosphatase activity and 12.4-fold higher up-regulation of bone sialoprotein), but reduced formation of adipocytes (5.2-fold lower oil red O-positive cells/area). Clonal populations of AHACs could be efficiently expanded in TFP, but not in control medium. Most TFP-expanded clones were able to redifferentiate only into chondrocytes (7 of 20) or were unable to differentiate (6 of 20). However, some clones (2 of 20) differentiated toward all of the lineages investigated, thus displaying characteristics of mesenchymal progenitor cells.


CONCLUSIONS
Dedifferentiated AHACs exhibit differentiation plasticity, which is modulated by growth factors used during monolayer expansion and is highly heterogeneous across different clones. Clonal culture of AHACs in the presence of regulatory molecules could lead to the identification of AHAC subpopulations with enhanced cartilage repair capacity.
Barbero
Andrea
A
University Hospital, Basel, Switzerland.
Ploegert
Sabine
S
Heberer
Michael
M
Martin
Ivan
I
D017667:Adipocytes / Q000166:cytology; D000328:Adult; D000469:Alkaline Phosphatase / Q000378:metabolism; D000077214:Becaplermin; D002358:Cartilage, Articular / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D002999:Clone Cells; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000096:biosynthesis; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D058574:Integrin-Binding Sialoprotein; D007719:Knee Joint; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D020574:Proto-Oncogene Proteins c-sis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012795:Sialoglycoproteins / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D053773:Transforming Growth Factor beta1
D017931:DNA Primers; D018076:DNA, Complementary; D006025:Glycosaminoglycans; C546871:IBSP protein, human; D058574:Integrin-Binding Sialoprotein; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D012795:Sialoglycoproteins; C508960:TGFB1 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D016222:Fibroblast Growth Factor 2; D000077214:Becaplermin; C013786:A73025; D000469:Alkaline Phosphatase