Matrix metalloproteinase-8 (MMP-8) is the major collagenase in human dentin.
OBJECTIVE
Previously an unidentified collagenolytic metalloprotease together with gelatinase (matrix metalloproteinase-2, MMP-2), and enamelysin (MMP-20) have been detected in human dentin. The aim of the study was to characterize dentinal collagenolytic enzymes. Furthermore, we hypothesized that the dentinal MMPs are protected by the mineral phase, and studied the stability of dentinal MMPs.


METHODS
To characterize dentinal collagenolytic enzymes, we used Western blotting with specific antibodies against MMP collagenases (MMP-1, -8, and -13) and cathepsin K. MMP-8 immunofluorometric assay (IFMA) was also used for MMP-8 detection, and functional collagenase activity was examined with type I collagen degradation assay. The stability of dentinal MMPs was examined by autoclaving dentin blocks before protein extraction and subsequent examination of protein levels and the activities of dentin collagenase and gelatinases.


RESULTS
MMP-8 (collagenase-2) was detected in dentin both with Western blot and IFMA, and dentinal samples also cleaved the intact type I collagen into characteristic 3/4(alphaA)-cleavage products in vitro. No other collagenases or cathepsin K were detected. In autoclaved samples no MMP-8 was found, but gelatinase activity was observed in protein fractions of mineralized dentin.


CONCLUSIONS
MMP-8 represents the major collagenase in human dentin. Unlike MMP-8, dentinal gelatinases can be detected after autoclave treatment of dentin, indicating their high resistance to external sample treatment procedures.
Sulkala
Merja
M
Institute of Dentistry, University of Oulu, PO Box 5281, 90014 University of Oulu, Oulu, Finland.
Tervahartiala
Taina
T
Sorsa
Timo
T
Larmas
Markku
M
Salo
Tuula
T
Tjäderhane
Leo
L
D000328:Adult; D015153:Blotting, Western; D017364:Collagenases / Q000032:analysis / Q000378:metabolism*; D003804:Dentin / Q000201:enzymology*; D018093:Gelatinases / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D007118:Immunoassay; D020784:Matrix Metalloproteinase 8 / Q000032:analysis / Q000378:metabolism*
D017364:Collagenases; D018093:Gelatinases; D020784:Matrix Metalloproteinase 8