Osteoclast inhibition by factors from cells associated with regenerative tissue
The purpose of this study was to determine whether cells associated with regenerative tissue can inhibit osteoclast differentiation and activity and to begin characterizing and identifying the factors mediating the observed effects. Cell isolates from regenerative cells adherent to ePTFE, membranes recovered from patients after GTR, and ridge augmentation procedures were established in culture. Human periodontal ligament (PDL) cells from periodontally healthy bicuspids extracted for orthodontic reasons also were cultured. Conditioned medium from these cells was tested by different assays to determine osteoclast-like differentiation and osteoclast resorption. The conditioned medium was characterized by Western blot analysis in order to establish the presence or absence of interferon gamma (IFN-gamma).The addition of each of these conditioned media to the bone marrow cultures significantly reduced the number of tartrate-resistant, acid phosphatase- positive osteoclast-like cells, compared with the control medium. The total resorbed surface area and number of resorption pits formed by these cells also were reduced. Heating the conditioned medium from the ePTFE cells to 56o C for one hour abrogated the inhibitory activity. The unheated fraction of the same experimental sample exhibited a statistically significant reduction. These experiments strongly suggest that the inhibitory effect is mediated by a protein. Western blot analysis of the conditioned medium detected a band at the molecular weight of IFN-gamma.
In conclusion, the factor in the conditioned medium that inhibits osteoclast differentiation is soluble and heat liable, suggestive of a protein and not a prostaglandin. The molecular weighs of this factor appears to be less than 30 kDa. Western blot analysis confirmed the presence of IFN-gamma in the conditioned medium. The finding that the factor is heat liable also correlates with the presence of IFN-gamma. [C.C.]
Rowe, D.J., W.W. Leung, and D.L. Del Carlo, J Periodont, 67:414, 1996