title: Unsaturated phosphatidylcholines lining on the surface of cartilage and its possible physiological roles.
abstract: BACKGROUND
  Evidence has strongly indicated that surface-active phospholipid (SAPL), or surfactant, lines the surface of cartilage and serves as a lubricating agent. Previous clinical study showed that a saturated phosphatidylcholine (SPC), dipalmitoyl-phosphatidylcholine (DPPC), was effective in the treatment of osteoarthritis, however recent studies suggested that the dominant SAPL species at some sites outside the lung are not SPC, rather, are unsaturated phosphatidylcholine (USPC). Some of these USPC have been proven to be good boundary lubricants by our previous study, implicating their possible important physiological roles in joint if their existence can be confirmed. So far, no study has been conducted to identify the whole molecule species of different phosphatidylcholine (PC) classes on the surface of cartilage. In this study we identified the dominant PC molecule species on the surface of cartilage. We also confirmed that some of these PC species possess a property of semipermeability.
  
  
  METHODS
  HPLC was used to analyse the PC profile of bovine cartilage samples and comparisons of DPPC and USPC were carried out through semipermeability tests.
  
  
  RESULTS
  It was confirmed that USPC are the dominant SAPL species on the surface of cartilage. In particular, they are Dilinoleoyl-phosphatidylcholine (DLPC), Palmitoyl-linoleoyl-phosphatidylcholine, (PLPC), Palmitoyl-oleoyl-phosphatidylcholine (POPC) and Stearoyl-linoleoyl-phosphatidylcholine (SLPC). The relative content of DPPC (a SPC) was only 8%. Two USPC, PLPC and POPC, were capable of generating osmotic pressure that is equivalent to that by DPPC.
  
  
  CONCLUSIONS
  The results from the current study confirm vigorously that USPC is the endogenous species inside the joint as against DPPC thereby confirming once again that USPC, and not SPC, characterizes the PC species distribution at non-lung sites of the body. USPC not only has better anti-friction and lubrication properties than DPPC, they also possess a level of semipermeability that is equivalent to DPPC. We therefore hypothesize that USPC can constitute a possible addition or alternative to the current commercially available viscosupplementation products for the prevention and treatment of osteoarthritis in the future.
authors: Orthopedic Research Unit, Prince Charles Hospital, Australia. chen_y2@hotmail.com
authors: Yi
authors: Y
authors: Chen
authors: Ross W
authors: RW
authors: Crawford
authors: Adekunle
authors: A
authors: Oloyede
references: Perit Dial Int. 2002 May-Jun;22(3):380-5
references: 12227397
references: Comp Biochem Physiol A Mol Integr Physiol. 2001 May;129(1):173-82
references: 11369542
references: Biochem J. 1988 Jul 15;253(2):451-7
references: 3178723
references: Lancet. 1981 Jan 10;1(8211):64-8
references: 6109119
references: Biochim Biophys Acta. 1995 Mar 16;1255(2):99-104
references: 7696337
references: Am J Kidney Dis. 1988 Jul;12(1):31-6
references: 3389351
references: Eur J Surg. 1995 May;161(5):341-4
references: 7662778
references: ANZ J Surg. 2005 Dec;75(12):1111-4
references: 16398821
references: Aust N Z J Surg. 2000 Jun;70(6):443-7
references: 10843402
references: Aust N Z J Surg. 1999 May;69(5):388-90
references: 10353557
references: J Appl Physiol (1985). 1992 Sep;73(3):1034-9
references: 1400014
references: J Rheumatol. 1990 Mar;17(3):349-56
references: 2332857
references: Perit Dial Int. 2000 Sep-Oct;20(5):503-15
references: 11117241
references: Ann Otol Rhinol Laryngol. 1972 Apr;81(2):268-71
references: 5067550
references: J Orthop Res. 2001 Jul;19(4):671-6
references: 11518278
references: Perit Dial Int. 1998 Mar-Apr;18(2):157-65
references: 9576363
references: Br J Rheumatol. 1998 Feb;37(2):143-7
references: 9569068
references: Clin Biomech (Bristol, Avon). 2004 Jun;19(5):534-42
references: 15182990
references: J Biol Chem. 1957 May;226(1):497-509
references: 13428781
references: Pharm Res. 2005 Nov;22(11):1926-30
references: 16132340
references: Am J Med. 1991 Aug 8;91(2A):43S-51S
references: 1882905
references: Proc Soc Exp Biol Med. 1957 May;95(1):170-2
references: 13432025
references: Rheumatology (Oxford). 1999 Oct;38(10):1020-1
references: 10534559
references: Anal Biochem. 1994 Jul;220(1):172-80
references: 7978242
references: J Lipid Res. 2002 Jan;43(1):99-106
references: 11792728
references: Br J Rheumatol. 1996 Sep;35(9):821-7
references: 8810664
references: Pulm Pharmacol Ther. 2006;19(4):292-6
references: 16168690