Global analyses of gene expression in early experimental osteoarthritis.
OBJECTIVE
To analyze genome-wide changes in chondrocyte gene expression in a surgically induced model of early osteoarthritis (OA) in rats, to assess the similarity of this model to human OA, and to identify genes and mechanisms leading to OA pathogenesis.


METHODS
OA was surgically induced in 5 rats by anterior cruciate ligament transection and partial medial meniscectomy. Sham surgery was performed in 5 additional animals, which were used as controls. Both groups underwent 4 weeks of forced mobilization, 3 times per week. RNA was extracted directly from articular chondrocytes in the OA (operated), contralateral, and sham-operated knees. Affymetrix GeneChip expression arrays were used to assess genome-wide changes in gene expression. Expression patterns of selected dysregulated genes, including Col2a1, Mmp13, Adamts5, Ctsc, Ptges, and Cxcr4, were validated by real-time polymerase chain reaction, immunofluorescence, or immunohistochemistry 2, 4, and 8 weeks after surgery.


RESULTS
After normalization, comparison of OA and sham-operated samples showed 1,619 differentially expressed probe sets with changes in their levels of expression > or = 1.5-fold, 722 with changes > or = 2-fold, 135 with changes > or = 4-fold, and 20 with changes of 8-fold. Dysregulated genes known to be involved in human OA included Mmp13, Adamts5, and Ptgs2, among others. Several dysregulated genes (e.g., Reln, Phex, and Ltbp2) had been identified in our earlier microarray study of hypertrophic chondrocyte differentiation. Other genes involved in cytokine and chemokine signaling, including Cxcr4 and Ccl2, were identified. Changes in gene expression were also observed in the contralateral knee, validating the sham operation as the appropriate control.


CONCLUSIONS
Our results demonstrate that the animal model mimics gene expression changes seen in human OA, supporting the relevance of newly identified genes and pathways to early human OA. We propose new avenues for OA pathogenesis research and potential targets for novel OA treatments, including cathepsins and cytokine, chemokine, and growth factor signaling pathways, in addition to factors controlling the progression of chondrocyte differentiation.
Appleton
C T G
CT
Canadian Institutes of Health Research, Ottawa, Ontario, Canada.
Pitelka
V
V
Henry
J
J
Beier
F
F
D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism; D000071116:ADAMTS5 Protein; D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery; D001169:Arthritis, Experimental / Q000209:etiology / Q000235:genetics* / Q000503:physiopathology; D002358:Cartilage, Articular / Q000378:metabolism / Q000473:pathology; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism; D024043:Collagen Type II / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D005786:Gene Expression Regulation / Q000502:physiology*; D008297:Male; D053509:Matrix Metalloproteinase 13 / Q000235:genetics / Q000378:metabolism; D008592:Menisci, Tibial / Q000601:surgery; D020411:Oligonucleotide Array Sequence Analysis; D010003:Osteoarthritis / Q000209:etiology / Q000235:genetics* / Q000503:physiopathology; D000071876:Prostaglandin-E Synthases; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D019718:Receptors, CXCR4 / Q000235:genetics / Q000378:metabolism; D000091042:Reelin Protein
C511513:COL2A1 protein, rat; C491766:Ccl2 protein, rat; D018932:Chemokine CCL2; D024043:Collagen Type II; C486264:Cxcr4 protein, rat; D019718:Receptors, CXCR4; D000091042:Reelin Protein; C000717129:Reln protein, rat; D011451:Prostaglandin-Endoperoxide Synthases; C000717127:RELN protein, human; D051722:ADAM Proteins; D000071116:ADAMTS5 Protein; C518696:Adamts5 protein, rat; D053509:Matrix Metalloproteinase 13; C507083:Mmp13 protein, rat; D000071876:Prostaglandin-E Synthases; C497818:Ptges protein, rat