title: Novel fluorescent compound (DDP) in calf, rabbit, and human articular cartilage and synovial fluid.
abstract: OBJECTIVE
  To investigate the presence of and quantify 2,6-dimethyldifuro-8-pyrone (DDP), a novel fluorescent compound identified as in various calf, rabbit, and human tissue/fluid samples, to determine the DDP level in articular cartilage (AC) laminae, and to investigate the changes in cartilage DDP content with cartilage maturation.
  
  
  METHODS
  Samples were obtained from calf (< 2 years), rabbit (< 2 weeks to 2 years) or human AC and synovial fluid (SF) as well as other non-cartilaginous tissues. SF and tissue samples were hydrolyzed with 6 M HCl (24 hours at 110 degrees C), lyophilized, and dissolved in HPLC mobile phase. DDP and collagen crosslink peaks were measured using a fluorescence detector at excitation and emission wavelengths of 295 and 395 nm, respectively.
  
  
  RESULTS
  DDP was detected from calf metacarpophalangeal joint AC (362 +/- 48 pmol/mg dry weight), SF (4.5 +/- 0.3 pmol/microl SF), and intervertebral disc (24 +/- 4 pmol/mg). DDP was not detected in calf ligament, tendon, bone, ocular lens, cornea, or elastic cartilage. The DDP amount was greater in mid-deep cartilage lamina (448 +/- 63 pmol/mg) than superficial-mid lamina (129 +/- 52 pmol/mg) (p = 0.008). DDP level decreased with maturation in rabbit knee joint AC from 185 +/- 40 (< 2 weeks) to 27 +/- 3 (2 years) pmol/mg dry weight. DDP was not detected in adult rabbit ligament, tendon, meniscus, or bone. DDP was detected in human knee joint AC and SF. The DDP level in osteoarthritic lesions was present in lower concentrations (range: 0 to 96 pmol/mg dried AC) compared to intact AC (range: 63 to 236 pmol/mg) of the same knee.
  
  
  CONCLUSIONS
  DDP is a hyaline cartilage specific compound present in all articular cartilage samples from various articulating joints/animal species. DDP level increases with AC depth and decreases with cartilage maturation. DDP is a potential indicator of cartilage metabolism during normal growth, ageing, and cartilage disease.
authors.affiliation: Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: Harpal K
authors.initials: HK
authors.lastname: Gahunia
authors.forename: Reinhold
authors.initials: R
authors.lastname: Vieth
authors.forename: Kenneth
authors.initials: K
authors.lastname: Pritzker
mesh_terms: D000368:Aged; D000375:Aging / Q000378:metabolism*; D000818:Animals; D001168:Arthritis / Q000175:diagnosis* / Q000378:metabolism / Q000503:physiopathology; D002358:Cartilage, Articular / Q000378:metabolism*; D002417:Cattle; D005260:Female; D005453:Fluorescence; D006801:Humans; D007403:Intervertebral Disc / Q000378:metabolism; D007798:Lampreys / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011753:Pyrones / Q000378:metabolism*; D011817:Rabbits; D013583:Synovial Membrane / Q000378:metabolism*
chemical_list: D011753:Pyrones