Osteogenic protein-1 promotes the synthesis and retention of extracellular matrix within bovine articular cartilage and chondrocyte cultures.
OBJECTIVE
We have used recombinant osteogenic protein-1 to investigate our hypothesis that proper repair and maintenance of cartilage requires not only enhanced biosynthesis and replenishment of the extracellular matrix but also the enhancement of components necessary for matrix retention.


METHODS
The effects of osteogenic protein-1 were examined on bovine articular cartilage slices as well as isolated chondrocytes grown in alginate beads. Cartilage slices were examined for accumulation of proteoglycan by incorporation of 35S-sulfate and staining using Safranin O or, a biotinylated probe specific for hyaluronan. Bovine chondrocytes were characterized by use of a particle exclusion assay, in-situ hybridization, quantitative-competitive RT-PCR and a hyaluronan-binding assay.


RESULTS
Osteogenic protein-1 treatment substantially enhanced the accumulation of hyaluronan and proteoglycan within cartilage tissue slices. As with the tissue, osteogenic protein-1 enhanced the size of cell-associated matrices assembled and retained by chondrocytes in vitro. This enhanced matrix assembly was paralleled by an increased expression of mRNA for aggrecan, hyaluronan synthase-2 and CD44. Of the two hyaluronan synthase genes expressed by chondrocytes, only hyaluronan synthase-2 was upregulated by osteogenic protein-1. Coupled with the increase in the CD44 mRNA was an increase in functional hyaluronan binding activity present at the chondrocyte cell surface.


CONCLUSIONS
These results demonstrate that osteogenic protein-1 stimulates not only the synthesis of the major cartilage extracellular matrix component aggrecan, but also two associated molecules necessary for the retention of aggrecan, namely hyaluronan and CD44.
Nishida
Y
Y
Department of Biochemistry, Rush Medical College, Rush-Presbyterian-St Luke's Medical Center, Chicago, Illinois 60612, USA.
Knudson
C B
CB
Kuettner
K E
KE
Knudson
W
W
D053674:Aggrecans; D000818:Animals; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D002358:Cartilage, Articular / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism; D046508:Culture Techniques; D005109:Extracellular Matrix / Q000378:metabolism*; D016326:Extracellular Matrix Proteins; D015870:Gene Expression; D014453:Glucuronosyltransferase / Q000235:genetics; D018960:Hyaluronan Receptors / Q000235:genetics; D006820:Hyaluronic Acid / Q000378:metabolism; D017403:In Situ Hybridization / Q000379:methods; D037181:Lectins, C-Type; D011509:Proteoglycans / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013268:Stimulation, Chemical; D016212:Transforming Growth Factor beta
D053674:Aggrecans; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D016326:Extracellular Matrix Proteins; D018960:Hyaluronan Receptors; D037181:Lectins, C-Type; D011509:Proteoglycans; D012333:RNA, Messenger; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D006820:Hyaluronic Acid; D014453:Glucuronosyltransferase