Tetraspanin CD151 is expressed in osteoarthritic cartilage and is involved in pericellular activation of pro-matrix metalloproteinase 7 in osteoarthritic chondrocytes.
OBJECTIVE
The proenzyme of matrix metalloproteinase 7 (proMMP-7), which can degrade various extracellular matrix (ECM) and non-ECM molecules after being activated, is overexpressed in osteoarthritic (OA) articular cartilage, but the process of its activation in the cartilage remains unknown. The present study was undertaken to investigate the expression of tetraspanin CD151 in OA cartilage and its involvement in proMMP-7 activation.


METHODS
The expression of CD151 in articular cartilage was examined by reverse transcription-polymerase chain reaction (RT-PCR), real-time PCR, immunohistochemistry, in situ hybridization, and immunoblotting. Chondrocytes were used to study the interaction between CD151 and proMMP-7, and activation of proMMP-7.


RESULTS
RT-PCR revealed expression of CD151 messenger RNA in all OA cartilage samples, but in only 30% of normal control cartilage samples. Immunohistochemistry and in situ hybridization findings indicated that CD151 was coexpressed with proMMP-7 in chondrocytes, mainly in the superficial and transitional zones of OA cartilage. CD151 immunoreactivity directly correlated with the Mankin score (r = 0.757, P < 0.0001 [n = 30]) and the degree of chondrocyte cloning (r = 0.83, P < 0.0001 [n = 30]) in the cartilage samples. Complexes CD151 and proMMP-7 and their colocalization on the cell membranes were demonstrated by immunoprecipitation and double fluorescence immunostaining of the OA chondrocytes. In situ zymography indicated that chondrocytes exhibit pericellular proteolytic activity, which was abolished by treatment with MMP inhibitors, anti-MMP-7 antibody, or anti-CD151 antibody.


CONCLUSIONS
These data demonstrate that CD151 is overexpressed in OA cartilage and suggest that CD151 plays a role in the pericellular activation of proMMP-7, leading to cartilage destruction and/or chondrocyte cloning.
Fujita
Yoshinari
Y
School of Medicine, Keio University, Tokyo, Japan.
Shiomi
Takayuki
T
Yanagimoto
Shigeru
S
Matsumoto
Hideo
H
Toyama
Yoshiaki
Y
Okada
Yasunori
Y
D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D002356:Cartilage / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation; D006801:Humans; D053582:Interleukin-1alpha / Q000502:physiology; D020783:Matrix Metalloproteinase 7 / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000235:genetics / Q000378:metabolism*; D020370:Osteoarthritis, Knee / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060185:Tetraspanin 24; D016212:Transforming Growth Factor beta / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000502:physiology
D015703:Antigens, CD; C554715:CD151 protein, human; D053582:Interleukin-1alpha; D012333:RNA, Messenger; D060185:Tetraspanin 24; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D042461:Vascular Endothelial Growth Factor A; C060932:MMP7 protein, human; D020783:Matrix Metalloproteinase 7