Igf-I extends the chondrogenic potential of human articular chondrocytes in vitro: molecular association between Sox9 and Erk1/2.
Expansion of articular chondrocytes in monolayer culture leads to loss of the unique chondrocyte phenotype and the cells' redifferentiation capacity. Dedifferentiation of chondrocytes in monolayer culture is a challenging problem for autologous chondrocyte transplantation (ACT). It is well established that Igf-I exerts positive anabolic effects on chondrocytes in vivo and in vitro. Accordingly, in this study, we examined whether the anabolic insulin-like growth factor-I (Igf-I) is capable of extending the chondrogenic potential of dedifferentiated chondrocytes in vitro. Chondrocyte monolayers were cultured up to 10 passages. At each passage chondrocytes were stimulated with Igf-I (10ng/ml) and introduced to high-density cultures for up to 7 days. Expression of collagen type II, cartilage-specific proteoglycans, activated caspase-3, integrin beta1, extracellular signal-regulated kinase (Erk) and Sox9 was examined by Western blotting, immunoprecipitation and immunomorphological techniques. Monolayer chondrocytes rapidly lost their differentiated phenotype. When introduced to high-density cultures, only chondrocytes from P1-P4 redifferentiated. In contrast, Igf-I treated cells from P1 up to P7 redifferentiated and formed cartilage-like tissue in high-density culture. P8-P10 cells exhibited apoptotic alterations and produced significantly less matrix. Igf-I markedly increased expression of integrin beta1, Erk and Sox9. Immunoprecipitation revealed that phosphorylated Erk1/2 physically interacts with Sox9 in chondrocyte nuclei, suggesting a previously unreported functional association which was markedly enhanced by Igf-I. Treatment of chondrocyte cultures with Igf-I stabilizes chondrogenic potential, stimulates Sox9 and promotes molecular interactions between Erk and Sox9. These effects appear to be regulated by the integrin/MAPK signaling pathways.
Shakibaei
Mehdi
M
Institute of Anatomy, Ludwig-Maximilians-University, Pettenkoferstrasse 11, 80336 Munich, Germany. mehdi.shakibaei@med.uni-muenchen.de
Seifarth
Claudia
C
John
Thilo
T
Rahmanzadeh
Masyar
M
Mobasheri
Ali
A
D015415:Biomarkers / Q000378:metabolism; D002358:Cartilage, Articular / Q000187:drug effects / Q000648:ultrastructure; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects* / Q000648:ultrastructure; D024043:Collagen Type II / Q000378:metabolism; D006609:High Mobility Group Proteins / Q000378:metabolism*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D046529:Microscopy, Electron, Transmission; D016253:Microscopy, Immunoelectron; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D055758:SOX9 Transcription Factor; D014157:Transcription Factors / Q000378:metabolism*
D015415:Biomarkers; D024043:Collagen Type II; D006609:High Mobility Group Proteins; D055758:SOX9 Transcription Factor; C527932:SOX9 protein, human; D014157:Transcription Factors; D007334:Insulin-Like Growth Factor I; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3