title: Disease-modifying effects of phosphocitrate and phosphocitrate-β-ethyl ester on partial meniscectomy-induced osteoarthritis.
abstract: BACKGROUND
  It is believed that phosphocitrate (PC) exerts its disease-modifying effects on osteoarthritis (OA) by inhibiting the formation of crystals. However, recent findings suggest that PC exerts its disease-modifying effect, at least in part, through a crystal-independent action. This study sought to examine the disease-modifying effects of PC and its analogue PC-β-ethyl ester (PC-E) on partial meniscectomy-induced OA and the structure-activity relationship.
  
  
  METHODS
  Calcification- and proliferation-inhibitory activities were examined in OA fibroblast-like synoviocytes (FLSs) culture. Disease-modifying effects were examined using Hartley guinea pigs undergoing partial meniscectomy. Cartilage degeneration was examined with Indian ink, safranin-O, and picrosirius red. Levels of matrix metalloproteinase-13 (MMP-13), ADAM metallopeptidase with thrombospondin type 1 motif 5 (ADAMTS5), chemokine (C-C motif) ligand 5 (CCL5), and cyclooxygenase-2 (Cox-2) were examined with immunostaining. The effects of PC-E and PC on gene expressions in OA FLSs were examined with microarray. Results are expressed as mean ± standard deviation and analyzed using Student's t test or Wilcoxon rank sum test.
  
  
  RESULTS
  PC-E was slightly less powerful than PC as a calcification inhibitor but as powerful as PC in the inhibition of OA FLSs proliferation. PC significantly inhibited cartilage degeneration in the partial meniscectomied right knee. PC-E was less powerful than PC as a disease-modifying drug, especially in the inhibition of cartilage degeneration in the non-operated left knee. PC significantly reduced the levels of ADAMTS5, MMP-13 and CCL5, whereas PC-E reduced the levels of ADAMTS5 and CCL5. Microarray analyses revealed that PC-E failed to downregulate the expression of many PC-downregulated genes classified in angiogenesis and inflammatory response.
  
  
  CONCLUSIONS
  PC is a disease-modifying drug for posttraumatic OA therapy. PC exerts its disease-modifying effect through two independent actions: inhibiting pathological calcification and modulating the expression of many genes implicated in OA. The β-carboxyl group of PC plays an important role in the inhibition of cartilage degeneration, little role in the inhibition of FLSs proliferation, and a moderate role in the inhibition of FLSs-mediated calcification.
authors.affiliation: Department of Orthopedic Surgery, Carolinas Medical Center, PO Box 32861, Charlotte, NC, 28232, USA. yubo.sun@carolinashealthcare.org.
authors.forename: Yubo
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Department of Orthopedic Surgery, Carolinas Medical Center, PO Box 32861, Charlotte, NC, 28232, USA. nikkole.haines@carolianshealthcare.org.
authors.forename: Nikkole
authors.initials: N
authors.lastname: Haines
authors.affiliation: Department of Orthopedic Surgery, Carolinas Medical Center, PO Box 32861, Charlotte, NC, 28232, USA. andrea.roberts@carolinashealthcare.org.
authors.forename: Andrea
authors.initials: A
authors.lastname: Roberts
authors.affiliation: Department of Orthopedic Surgery, Carolinas Medical Center, PO Box 32861, Charlotte, NC, 28232, USA. michael.ruffolo@carolinashealthcare.org.
authors.forename: Michael
authors.initials: M
authors.lastname: Ruffolo
authors.affiliation: Department of Orthopedic Surgery, Carolinas Medical Center, PO Box 32861, Charlotte, NC, 28232, USA. david.mauerhan@carolinashealthcare.org.
authors.forename: David R
authors.initials: DR
authors.lastname: Mauerhan
authors.affiliation: Department of Comparative Medicine, Carolinas Medical Center, PO Box 32861, Charlotte, NC, 28232, USA. kim.mikalko@carolinashealthcare.org.
authors.forename: Kim L
authors.initials: KL
authors.lastname: Mihalko
authors.affiliation: Department of Orthopedic Surgery, Carolinas Medical Center, PO Box 32861, Charlotte, NC, 28232, USA. jane.ingram@carolinashealthcare.org.
authors.forename: Jane
authors.initials: J
authors.lastname: Ingram
authors.affiliation: Department of Orthopedic Surgery, Carolinas Medical Center, PO Box 32861, Charlotte, NC, 28232, USA. Michael.cox@carolinashealthcare.org.
authors.forename: Michael
authors.initials: M
authors.lastname: Cox
authors.affiliation: Department of Orthopedic Surgery, Carolinas Medical Center, PO Box 32861, Charlotte, NC, 28232, USA. edward.hanley@carolinashealthcare.org.
authors.forename: Edward N
authors.initials: EN
authors.lastname: Hanley
mesh_terms: D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D018501:Antirheumatic Agents / Q000737:chemistry / Q000494:pharmacology*; D002114:Calcinosis / Q000517:prevention & control; D002358:Cartilage, Articular / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D018946:Chemokine CCL5 / Q000235:genetics / Q000378:metabolism; D002951:Citrates / Q000737:chemistry / Q000494:pharmacology*; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D006168:Guinea Pigs; D008297:Male; D053509:Matrix Metalloproteinase 13 / Q000235:genetics / Q000378:metabolism; D008592:Menisci, Tibial / Q000601:surgery*; D015394:Molecular Structure; D010003:Osteoarthritis / Q000188:drug therapy* / Q000209:etiology / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D013329:Structure-Activity Relationship; D013583:Synovial Membrane / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology
chemical_list: D018501:Antirheumatic Agents; D018946:Chemokine CCL5; D002951:Citrates; C014148:phosphocitrate; D051546:Cyclooxygenase 2; D051722:ADAM Proteins; D053509:Matrix Metalloproteinase 13