Distinct roles of Smad pathways and p38 pathways in cartilage-specific gene expression in synovial fibroblasts.
The role of TGF-beta/bone morphogenetic protein signaling in the chondrogenic differentiation of human synovial fibroblasts (SFs) was examined with the adenovirus vector-mediated gene transduction system. Expression of constitutively active activin receptor-like kinase 3 (ALK3CA) induced chondrocyte-specific gene expression in SFs cultured in pellets or in SF pellets transplanted into nude mice, in which both the Smad and p38 pathways are essential. To analyze downstream cascades of ALK3 signaling, we utilized adenovirus vectors carrying either Smad1 to stimulate Smad pathways or constitutively active MKK6 (MKK6CA) to activate p38 pathways. Smad1 expression had a synergistic effect on ALK3CA, while activation of p38 MAP kinase pathways alone by transduction of MKK6CA accelerated terminal chondrocytic differentiation, leading to type X collagen expression and enhanced mineralization. Overexpression of Smad1 prevented MKK6CA-induced type X collagen expression and maintained type II collagen expression. In a mouse model of osteoarthritis, activated p38 expression as well as type X collagen staining was detected in osteochondrophytes and marginal synovial cells. These results suggest that SFs can be differentiated into chondrocytes via ALK3 activation and that stimulating Smad pathways and controlling p38 activation at the proper level can be a good therapeutic strategy for maintaining the healthy joint homeostasis and treating degenerative joint disorders.
Department of Orthopaedic Surgery, Faculty of Medicine, The University of Tokyo, Tokyo, Japan.
Hiroaki
H
Seto
Satoshi
S
Kamekura
Toshiki
T
Miura
Aiichiro
A
Yamamoto
Hirotaka
H
Chikuda
Toru
T
Ogata
Hisatada
H
Hiraoka
Hiromi
H
Oda
Kozo
K
Nakamura
Hisashi
H
Kurosawa
Ung-Il
UI
Chug
Hiroshi
H
Kawaguchi
Sakae
S
Tanaka
D029404:Activin Receptors / Q000378:metabolism; D000256:Adenoviridae / Q000235:genetics; D000328:Adult; D000368:Aged; D000818:Animals; D015152:Blotting, Northern; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002356:Cartilage / Q000378:metabolism*; D002454:Cell Differentiation; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D024121:Collagen Type X / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000502:physiology*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism*; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D006801:Humans; D015151:Immunoblotting; D048669:MAP Kinase Kinase 6; D051379:Mice; D008819:Mice, Nude; D008875:Middle Aged; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D010003:Osteoarthritis / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051785:Smad Proteins; D051898:Smad1 Protein; D013583:Synovial Membrane / Q000166:cytology*; D015534:Trans-Activators / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases
D024121:Collagen Type X; D004268:DNA-Binding Proteins; C497399:SMAD1 protein, human; D051785:Smad Proteins; D051898:Smad1 Protein; C497401:Smad1 protein, mouse; D015534:Trans-Activators; D012313:RNA; D003094:Collagen; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D029404:Activin Receptors; D048669:MAP Kinase Kinase 6; C482566:MAP2K6 protein, human; C482567:Map2k6 protein, mouse