Progression of chondrogenesis in C3H10T1/2 cells is associated with prolonged and tight regulation of ERK1/2.
Close contact of mesenchymal cells in vivo and also in super dense micromass cultures in vitro results in cellular condensation and alteration of existing cellular signaling required for initiation and progression of chondrogenesis. To investigate chondrogenesis related changes in the activity of ubiquitous cell signaling mediated by mitogen-activated protein kinases (MAP kinase), we have compared the effect of cell seeding of pluripotent C3H10T1/2 mesenchymal cells as monolayers (non-chondrogenic culture) or high density micromass cultures (chondrogenic) on the regulation and phosphorylation state of extracellular signal-regulated kinase 1 and 2 (ERK1/2) and also on regulation of ERK1/2 nuclear targets, namely, activation protein-1 (AP-1) and serum response factor (SRF). Increasing cell density resulted in reduced DNA binding as well as activity of AP-1. SRF activity, on the other hand, was up-regulated in confluent monolayer cultures but like AP-1 was inhibited in micromass cultures. Low levels of PD 98059 (5 microM), a specific inhibitor of ERK1/2, resulted in delayed induction of AP-1 and SRF activity whereas higher concentrations of this inhibitor (10-50 microM) conferred an opposite effect. Increasing concentrations of the PD 98059 inhibitor in long term monolayer or micromass cultures (2.5 day) resulted in differential regulation of c-Fos and c-Jun protein levels as well as total expression and phosphorylation levels of ERK1/2. PD 98059 treatment of C3H10T1/2 micromass cultures also resulted in up-regulation of type IIB collagen and Sox9 gene expression. While high expression of aggrecan and type IIB collagen genes were dependent on BMP-2 signaling, ERK inhibition of BMP-2 treated micromass cultures resulted in reduced activity of both genes. Our findings show that the activity of ERK1/2 in chondrogenic cultures of C3H10T1/2 cells is tightly controlled and can cross interact with other signaling activities mediated by BMP-2 to positively regulate chondrogensis.
Seghatoleslami
M Reza
MR
Division of Rheumatology, Department of Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA. reza.seghatoleslami@mexil.tju.edu
Roman-Blas
Jorge A
JA
Rainville
Anne M
AM
Modaressi
Rozbeh
R
Danielson
Keith G
KG
Tuan
Rocky S
RS
D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D002460:Cell Line; D020219:Chondrogenesis / Q000235:genetics / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation; D048369:MAP Kinase Kinase 1; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis; D026362:Serum Response Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism; D016212:Transforming Growth Factor beta
D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D026362:Serum Response Factor; D018808:Transcription Factor AP-1; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one