Calcium deposition in osteoarthritic meniscus and meniscal cell culture.
BACKGROUND
Calcium crystals exist in the knee joint fluid of up to 65% of osteoarthritis (OA) patients and the presence of these calcium crystals correlates with the radiographic evidence of hyaline cartilaginous degeneration. This study sought to examine calcium deposition in OA meniscus and to investigate OA meniscal cell-mediated calcium deposition. The hypothesis was that OA meniscal cells may play a role in pathological meniscal calcification.


METHODS
Studies were approved by our human subjects Institutional Review Board. Menisci were collected during joint replacement surgeries for OA patients and during limb amputation surgeries for osteosarcoma patients. Calcium deposits in menisci were examined by alizarin red staining. Expression of genes involved in biomineralization in OA meniscal cells was examined by microarray and real-time RT-PCR. Cell-mediated calcium deposition in monolayer culture of meniscal cells was examined using an ATP-induced (45)calcium deposition assay.


RESULTS
Calcium depositions were detected in OA menisci but not in normal menisci. The expression of several genes involved in biomineralization including ENPP1 and ANKH was upregulated in OA meniscal cells. Consistently, ATP-induced calcium deposition in the monolayer culture of OA meniscal cells was much higher than that in the monolayer culture of control meniscal cells.


CONCLUSIONS
Calcium deposition is common in OA menisci. OA meniscal cells calcify more readily than normal meniscal cells. Pathological meniscal calcification, which may alter the biomechanical properties of the knee meniscus, is potentially an important contributory factor to OA.
Sun
Yubo
Y
Department of Orthopaedic Surgery, Carolinas Medical Center, PO Box 32861, Charlotte, NC 28232, USA. yubo.sun@carolinas.org
Mauerhan
David R
DR
Honeycutt
Patrick R
PR
Kneisl
Jeffrey S
JS
Norton
H James
HJ
Zinchenko
Natalia
N
Hanley
Edward N
EN
Gruber
Helen E
HE
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000328:Adult; D000368:Aged; D000880:Anthraquinones / Q000737:chemistry; D002118:Calcium / Q000032:analysis / Q000378:metabolism; D002478:Cells, Cultured; D002648:Child; D002805:Chondrocalcinosis / Q000378:metabolism / Q000473:pathology*; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D005260:Female; D015870:Gene Expression; D006801:Humans; D007719:Knee Joint / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008592:Menisci, Tibial / Q000378:metabolism / Q000473:pathology*; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D020370:Osteoarthritis, Knee / Q000378:metabolism / Q000473:pathology*; D028061:Phosphate Transport Proteins / Q000235:genetics / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000235:genetics / Q000378:metabolism; D011755:Pyrophosphatases / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation
C498770:ANKH protein, human; D000880:Anthraquinones; D028061:Phosphate Transport Proteins; D012333:RNA, Messenger; C010078:alizarin; D000255:Adenosine Triphosphate; D010727:Phosphoric Diester Hydrolases; C065962:ectonucleotide pyrophosphatase phosphodiesterase 1; D011755:Pyrophosphatases; D002118:Calcium