Regulation of anabolic and catabolic gene expression in normal and osteoarthritic adult human articular chondrocytes by osteogenic protein-1.
OBJECTIVE
Osteoarthritis is characterized by dramatic changes in chondrocyte metabolism including the overexpression of catabolic enzymes, but also a lack of anabolic activity. In this respect, osteogenic protein 1 (OP-1) appears to be one of the most potent anabolic factors of chondrocytes. In this study, we were interested in: (1) whether recombinant human OP-1 exerts its anabolic effects also on osteoarthritic chondrocytes, (2) whether OP-1 modulates the expression of catabolic genes, and (3) whether the BMP effects are related to the expression levels of its intracellular mediators (R- and I-Smads).


METHODS
Chondrocytes were isolated from cartilage of either normal (n = 5) or osteoarthritic (n = 8) human knee joints and cultured in short-term high-density monolayer cultures with and without recombinant OP-1. RNA was isolated and analyzed for mRNA expression levels of anabolic (aggrecan, collagen type II), catabolic (MMP-1, -3, -13, ADAMTS-4), and intracellular signaling mediators (Smad 1, 4, 5, 6, 7, and 8) by quantitative online PCR.


RESULTS
After OP-1 stimulation, the anabolic genes were significantly up-regulated in osteoarthritic chondrocytes in comparison to normal chondrocytes. Neither in normal nor osteoarthritic chondrocytes were significant changes observed for the matrix degrading enzymes. Smads were also expressed in both normal and osteoarthritic cells at roughly the same level with and without stimulation with OP-1.


CONCLUSIONS
Osteoarthritic chondrocytes are not hypo-responsive to anabolic stimulation by OP-1. Thus, human recombinant OP-1 could be a suitable anabolic activator of osteoarthritic chondrocytes. This might be of particular interest as chondrocytes themselves showed very low levels of OP-1 expression.
Fan
Z
Z
Department of Pathology, University of Erlangen-Nürnberg, Krankenhausstr. 8-10, D-91054 Erlangen, Germany.
Chubinskaya
S
S
Rueger
D C
DC
Bau
B
B
Haag
J
J
Aigner
T
T
D051722:ADAM Proteins; D000071121:ADAMTS4 Protein; D000328:Adult; D000368:Aged; D053674:Aggrecans; D045930:Anabolic Agents / Q000494:pharmacology; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D002358:Cartilage, Articular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism*; D024043:Collagen Type II / Q000235:genetics / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D015342:DNA Probes / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D016326:Extracellular Matrix Proteins; D005260:Female; D015870:Gene Expression; D006801:Humans; D037181:Lectins, C-Type; D008297:Male; D020782:Matrix Metalloproteinases / Q000235:genetics / Q000378:metabolism; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods; D011348:Procollagen N-Endopeptidase; D011509:Proteoglycans / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins; D051785:Smad Proteins; D051898:Smad1 Protein; D019914:Taq Polymerase; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta
D053674:Aggrecans; D045930:Anabolic Agents; C525819:BMP7 protein, human; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D024043:Collagen Type II; D017931:DNA Primers; D015342:DNA Probes; D004268:DNA-Binding Proteins; D016326:Extracellular Matrix Proteins; D037181:Lectins, C-Type; D011509:Proteoglycans; D012333:RNA, Messenger; D011994:Recombinant Proteins; C497399:SMAD1 protein, human; D051785:Smad Proteins; D051898:Smad1 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D019914:Taq Polymerase; D051722:ADAM Proteins; D020782:Matrix Metalloproteinases; D008666:Metalloendopeptidases; D011348:Procollagen N-Endopeptidase; D000071121:ADAMTS4 Protein; C000603918:ADAMTS4 protein, human