Possible involvement of the oxidized low-density lipoprotein/lectin-like oxidized low-density lipoprotein receptor-1 system in pathogenesis and progression of human osteoarthritis.
OBJECTIVE
Using human cartilage samples and cultured chondrocytes, to assess the possible involvement of oxidized low-density lipoprotein (ox-LDL) and lectin-like ox-LDL receptor-1 (LOX-1) in pathogenesis and progression of osteoarthritis (OA).


METHODS
Thirty-two cartilage samples were obtained from 16 patients with knee OA, and 12 Control samples from six with femoral neck fracture. LOX-1 mRNA expressions in 12 OA and six Control samples were analyzed by reverse transcription-polymerase chain reaction (RT-PCR). Immunohistochemistry for ox-LDL and LOX-1 was performed in all samples. The histological OA grade was assessed with the modified Mankin score. The relative percentage of the ox-LDL and LOX-1 immunopositive chondrocytes was calculated in all samples. The effects of ox-LDL on cell viability in cultured human chondrocytes were investigated by the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay and on proteoglycan synthesis by monitoring [35S] sulfate incorporation.


RESULTS
There was a statistically significant difference between mean LOX-1/GAPDH (LOX-1/human glyceraldehyde-3-phosphate dehydrogenase) ratio of OA samples and that of Control samples (40.6%+/-10.3 and 11.9%+/-2.8, respectively, P<0.0001). The mean percentage of ox-LDL-positive cells was 23.0+/-15.7% in OA and 4.3+/-3.7% in Control cells (P=0.0002). The mean percentage of LOX-1-positive cells was 51.7+/-29.5% in OA and 10.0+/-8.1% in Control cells (P<0.0001). Both the ox-LDL immunoreactivity and the LOX-1 immunoreactivity were significantly correlated with the modified Mankin scores (R2=0.67 and 0.48, respectively; P<0.0001 for each). ox-LDL significantly reduced the human chondrocyte viability and proteoglycan synthesis, and pretreatment with anti-human LOX-1 monoclonal antibody reversed these effects.


CONCLUSIONS
The ox-LDL/LOX-1 system may be involved in human OA.
Akagi
M
M
Department of Orthopaedic Surgery, Kinki University School of Medicine, 377-2 Ohno-Higashi, Osaka-Sayama City, Osaka 589-8511, Japan. makagi@med.kindai.ac.jp
Kanata
S
S
Mori
S
S
Itabe
H
H
Sawamura
T
T
Hamanishi
C
C
D000368:Aged; D000369:Aged, 80 and over; D002358:Cartilage, Articular / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008297:Male; D010003:Osteoarthritis / Q000378:metabolism* / Q000473:pathology; D011509:Proteoglycans / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051127:Scavenger Receptors, Class E / Q000378:metabolism*
D008077:Lipoproteins, LDL; D011509:Proteoglycans; D051127:Scavenger Receptors, Class E; C099252:oxidized low density lipoprotein