Abstract
Introduction: In hereditary multiple exostosis (HME) the synthesis of the polysaccharide heparan sulphate (HS) is disrupted. HS-proteoglycans are low affinity receptors involved in fibroblast growth factor signaling. Activation of FGF receptor 3 (FGFr3) on mature chondrocytes leads to growth attenuation rather than stimulation. We tested the hypothesis that in HME chondrocytes with absent or reduced HS-PG synthesis there is impaired response to the FGFr3 ligand and loss of control of chondrocyte proliferation.
Materials and methods: Chondrocytes were harvested from normal growth plate (epiphyseodesis) or HME osteochondroma cartilage cap obtained as surgical discard and cultured to 70% confluence in growth media. Cells were re-plated for experimentation. Growth curves were obtained for cells over a period of 5 days. In addition proliferative responses of healthy and HME chondrocytes were determined after low serum synchronization followed by challenge with FGF 9 (10 and 100ng/ml) and incorporation of BrdU for 2hours every two hours over a twenty eight hour period. Using these techniques it is possible to describe in detail the time dependent entry of cells into S-phase of the cell cycle and compare cell lines and treatment.
Results: Significant differences were observed in the growth characteristics over a five-day period (p< 0.05). Under baseline growing conditions the chondrocytes derived from osteochondroma had a more rapid doubling time when compared with the normal growth plate chondrocyte (2.6+/− 0.6 vs 4.9+/−1.0, p< 0.05). In response to incubation with FGF-9 cells from normal growth plate have a lower peak proportion of cells entering the s-phase than with media alone (7% vs 25%). This inhibition is not observed in chondrocytes from osteochondroma.
Conclusions: It would appear that osteochondroma chondrocytes are resistant to the normal regulatory effect of FGF-9 on cell proliferation. The differential response to FGF may be responsible for the growth differences observed both in-vitro and in-vivo.
The abstracts were prepared by Mrs Leslie O’Leary. Correspondence should be addressed to her at British Orthopaedic Association, 35–43 Lincoln’s Inn Fields, London WC2A 3PE or at l.oleary@boa.ac.uk
