Expression of cartilage intermediate layer protein/nucleotide pyrophosphohydrolase parallels the production of extracellular inorganic pyrophosphate in response to growth factors and with aging

Arthritis Rheum. 2000 Dec;43(12):2703-11. doi: 10.1002/1529-0131(200012)43:12<2703::AID-ANR10>3.0.CO;2-Y.


Objective: To evaluate the role of the extracellular inorganic pyrophosphate (ePPi)-generating ectoenzyme cartilage intermediate layer protein/nucleotide pyrophosphohydrolase (CILP/NTPPH) in chondrocyte PPi elaboration, we studied CILP/NTPPH expression in response to growth factors during aging.

Methods: Porcine chondrocytes from adult (3-4-year-old) and young (2-week-old) animals were stimulated with transforming growth factor beta1 (TGFbeta1), which enhances ePPi elaboration, and/or insulin-like growth factor 1 (IGF-1), which diminishes ePPi elaboration. Measurements of ePPi, NTPPH enzyme activity, Western blot analysis, reverse transcriptase-polymerase chain reaction (RT-PCR), and Northern blot analysis were performed.

Results: Elaboration of ePPi into conditioned media from adult chondrocytes was significantly increased by TGFbeta1 and significantly inhibited by IGF-1, but no significant differences were observed in young chondrocytes. The protein levels of CILP/NTPPH by Western analysis in the media from adult and young porcine chondrocytes were increased by TGFbeta1. RT-PCR and Northern analysis showed that CILP/NTPPH messenger RNA (mRNA) expression in both adult and young chondrocytes was increased by TGFbeta1 and decreased by IGF-1, but these changes were less significant in the young chondrocytes. Basal and TGFbeta1-up-regulated levels of CILP/NTPPH expression were higher in adult chondrocytes than in young chondrocytes.

Conclusion: These results provide evidence that CILP/NTPPH expression and ePPi elaboration are concomitantly stimulated by TGFbeta1 and down-regulated by IGF-1, especially in adult chondrocytes, implicating CILP/NTPPH as a functional participant in ePPi elaboration. Increased CILP/NTPPH mRNA expression in chondrocytes derived from aged animals compared with young animals might promote the formation of calcium pyrophosphate dihydrate crystals in aged cartilage.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aging / drug effects*
  • Animals
  • Cartilage / enzymology*
  • Cells, Cultured
  • Culture Media, Conditioned
  • Diphosphates / metabolism*
  • Extracellular Space / chemistry
  • Growth Substances / pharmacology*
  • Phosphates / metabolism*
  • Pyrophosphatases / biosynthesis*
  • Pyrophosphatases / genetics
  • Pyrophosphatases / metabolism
  • RNA, Messenger / metabolism
  • Swine


  • Culture Media, Conditioned
  • Diphosphates
  • Growth Substances
  • Phosphates
  • RNA, Messenger
  • Pyrophosphatases
  • nucleotide pyrophosphatase