Type X collagen synthesis in human osteoarthritic cartilage. Indication of chondrocyte hypertrophy.
OBJECTIVE
To investigate the appearance of hypertrophic chondrocytes in osteoarthritic (OA) cartilage, using type X collagen as a specific marker.


METHODS
The biosynthesis of type X collagen was examined by metabolic labeling of freshly isolated articular chondrocytes with 3H-proline, immunoprecipitation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the synthesized collagens. Extracellular deposition of types X and II collagen was analyzed immunohistochemically.


RESULTS
Immunostaining revealed an irregular distribution of type X collagen, which was localized around chondrocyte clusters in fibrillated OA cartilage, but was absent from the noncalcified region of normal articular cartilage. Freshly isolated OA chondrocytes synthesized predominantly type X collagen, while control chondrocytes synthesized mostly type II collagen.


CONCLUSIONS
Our findings indicate focal premature chondrocyte differentiation to hypertrophic cells in OA cartilage.
von der Mark
K
K
Max-Planck-Society, Department of Orthopaedics, Waldkrankenhaus St. Marien, Erlangen, Federal Republic of Germany.
Kirsch
T
T
Nerlich
A
A
Kuss
A
A
Weseloh
G
G
Glückert
K
K
Stöss
H
H
D000328:Adult; D000368:Aged; D002358:Cartilage, Articular / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology*; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis* / Q000737:chemistry; D005260:Female; D006801:Humans; D006984:Hypertrophy; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000378:metabolism*; D012016:Reference Values
D003094:Collagen