Effects of intermittent hydrostatic pressure and BMP-2 on osteoarthritic human chondrocyte metabolism in vitro.
OBJECTIVE
This study examined effects of intermittent hydrostatic pressure (IHP) and a chondrogenic growth factor, bone morphogenetic protein-2 (BMP-2), on anabolic, catabolic, and other metabolic markers in human osteoarthritic (OA) chondrocytes in vitro.


METHODS
Articular chondrocytes, isolated from femoral OA cartilage and maintained in high-density monolayer culture, were examined for effects of BMP-2 and IHP on gene expression of matrix-associated proteins (aggrecan, type II collagen, and SOX9) and catabolic matrix metalloproteinases (MMP-2 and MMP-3) and culture medium levels of the metabolic markers MMP-2, nitric oxide (NO), and glycosaminoglycan (GAG). The results were analyzed using a mixed linear regression model to investigate the effects of load and growth factor concentration.


RESULTS
IHP and BMP-2 modulated OA chondrocyte metabolism in accordance with growth factor concentration independently, without evidence of synergism or antagonism. Each type of stimulus acted independently on anabolic matrix gene expression. Type II collagen and SOX9 gene expression were stimulated by both IHP and BMP-2 whereas aggrecan was increased only by BMP-2. IHP exhibited a trend to decrease MMP-2 gene expression as a catabolic marker whereas BMP-2 did not. NO production was increased by addition of BMP-2 and IHP exhibited a trend for increased levels. GAG production was increased by BMP-2.


CONCLUSIONS
This study confirmed the hypothesis that human OA chondrocytes respond to a specific type of mechanical load, IHP, through enhanced articular cartilage macromolecule gene expression and that IHP, in combination with a chondrogenic growth factor BMP-2, additively enhanced matrix gene expression without interactive effects.
Smith
R L
RL
Bone and Joint RR&D Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304, USA. smith@rrd.stanford.edu
Lindsey
D P
DP
Dhulipala
L
L
Harris
A H S
AH
Goodman
S B
SB
Maloney
W J
WJ
D000368:Aged; D053674:Aggrecans / Q000235:genetics; D015415:Biomarkers / Q000378:metabolism; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology*; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D003470:Culture Media / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000235:genetics; D005260:Female; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D006874:Hydrostatic Pressure; D066298:In Vitro Techniques; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D008660:Metabolism / Q000187:drug effects / Q000502:physiology; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism; D020370:Osteoarthritis, Knee / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D016474:Weight-Bearing / Q000502:physiology*
C508319:ACAN protein, human; D053674:Aggrecans; C525718:BMP2 protein, human; D015415:Biomarkers; D055396:Bone Morphogenetic Protein 2; D003470:Culture Media; D016326:Extracellular Matrix Proteins; D006025:Glycosaminoglycans; D009569:Nitric Oxide; C511768:MMP3 protein, human; D019278:Matrix Metalloproteinase 3; C522361:MMP2 protein, human; D020778:Matrix Metalloproteinase 2