Interactions of pentosan polysulfate with cartilage matrix proteins and synovial fibroblasts derived from patients with osteoarthritis.
Pentosan polysulfate (PPS) has been shown to improve symptoms of patients with osteoarthritis (OA) when studied under double-blinded conditions. Laboratory studies indicated that this drug exhibits multiple actions, including the preservation of articular cartilage (AC) proteoglycans in animal models of OA and the stimulation of hyaluronan synthesis by synovial fibroblasts in vitro and in vivo. As PPS is strongly anionic and has a molecular weight of approximately 5700 Da its ability to enter connective tissues rich in proteoglycans and interact with the resident cells has been questioned. In the present studies, experiments were undertaken to isolate and characterize proteins in human AC which have the potential to bind PPS. Thrombospondin was identified in 4.0 M GuHCl extracts of human AC as a PPS-binding protein. Furthermore, synovial fibroblasts derived from OA joints were shown to secrete thrombospondin and also bind PPS. Using bovine erythrocytes conjugated with PPS a rosetting of the synovial fibroblast could be demonstrated. The level of rosetting was not affected by pre-incubating cultures with thrombospondin antibody suggesting that PPS was interacting directly with the cells. Kinetic studies of 3H-PPS uptake by synovial fibroblasts showed saturation of binding sites within 30 min when cells were maintained at 4 degrees C but preservation of drug uptake for up to 120 min when cells were cultured at 37 degrees C. These data, together with the finding that cells labeled with drug at 37 degrees C showed higher incorporation, than at 4 degrees C after trypsin digestion suggests that PPS first binds to the cell membrane when at 37 degrees C is internalized, possibly by pinocytosis.
Ghosh
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Raymond Purves Bone and Joint Research Laboratories (University of Sydney), Royal North Shore Hospital of Sydney St. Leonards, NSW, Australia.
Hutadilok
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D000368:Aged; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000378:metabolism*; D001665:Binding Sites; D064236:Cartilage Oligomeric Matrix Protein; D002358:Cartilage, Articular / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D005260:Female; D005270:Femur Head / Q000378:metabolism / Q000473:pathology; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D019084:Fluorescent Antibody Technique, Indirect; D006023:Glycoproteins; D006801:Humans; D064235:Matrilin Proteins; D008562:Membrane Glycoproteins / Q000378:metabolism*; D015207:Osteoarthritis, Hip / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D010426:Pentosan Sulfuric Polyester / Q000378:metabolism*; D010873:Pinocytosis; D013582:Synovial Fluid / Q000166:cytology; D019699:Thrombospondins
D000894:Anti-Inflammatory Agents, Non-Steroidal; D064236:Cartilage Oligomeric Matrix Protein; D015815:Cell Adhesion Molecules; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D064235:Matrilin Proteins; D008562:Membrane Glycoproteins; C577553:TSP5 protein, human; D019699:Thrombospondins; D010426:Pentosan Sulfuric Polyester