Regulation of YKL-40 production by human articular chondrocytes.
OBJECTIVE
YKL-40 (human cartilage glycoprotein 39) is one of the most abundant proteins secreted by cultured chondrocytes. The objectives of the present study were to identify regulators of YKL-40 production in cartilage and chondrocytes and to map the localization of YKL-40 in chondrocytes.


METHODS
Human articular chondrocytes and cartilage explants (obtained from subjects at autopsy, from a tissue bank, and from osteoarthritis [OA] patients undergoing total joint replacement surgery) were stimulated with cytokines, growth factors, and other agents. YKL-40 expression was analyzed by Northern blot and polymerase chain reaction. YKL-40 secretion into the media was determined by enzyme-linked immunosorbent assay.


RESULTS
YKL-40 production increased to very high levels during the early phase of chondrocyte monolayer culture and in normal cartilage explant cultures as a response to tissue injury. Spontaneous YKL-40 release was higher in OA than in normal cartilage explant cultures. In chondrocyte monolayer cultures, interleukin-1beta (IL-1beta) and transforming growth factor beta (TGFbeta) decreased the levels of secreted YKL-40, and this was associated with a reduction in YKL-40 messenger RNA levels. IL-1beta, but not TGFbeta, reduced YKL-40 production in cartilage explant cultures. Media from explants treated with cycloheximide had no detectable YKL-40, suggesting that the released protein was newly synthesized. Immunofluorescence microscopy showed YKL-40 staining in the Golgi system of the chondrocytes, but YKL-40 could not be detected in the extracellular matrix.


CONCLUSIONS
The spontaneous increase in the production of YKL-40 in the early phase of culture appears to represent a cellular response to changes in the extracellular matrix environment. This, coupled with the profound suppressive effects of IL-1beta and TGFbeta on YKL-40 production, identifies a novel regulatory pattern for this major chondrocyte-derived protein.
Johansen
J S
JS
University of California San Diego, La Jolla, USA.
Olee
T
T
Price
P A
PA
Hashimoto
S
S
Ochs
R L
RL
Lotz
M
M
D054392:Adipokines; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001324:Autoantigens / Q000096:biosynthesis* / Q000235:genetics; D015152:Blotting, Northern; D002358:Cartilage, Articular / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D000071451:Chitinase-3-Like Protein 1; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D017077:Culture Media, Conditioned / Q000494:pharmacology; D006023:Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007375:Interleukin-1 / Q000494:pharmacology; D007719:Knee Joint / Q000378:metabolism / Q000473:pathology; D037102:Lectins; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D054392:Adipokines; D001324:Autoantigens; C084533:CHI3L1 protein, human; D000071451:Chitinase-3-Like Protein 1; D017077:Culture Media, Conditioned; D006023:Glycoproteins; D007375:Interleukin-1; D037102:Lectins; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta