Occurrence and temporal variation in matrix metalloproteinases and their inhibitors during murine secondary palatal morphogenesis

Extracellular matrix (ECM) molecules are known to play a pivotal Pole in mo rphogenesis of the secondary palate, and changes in their composition and d istribution, not attributable to changes in synthesis. are known to occur d uring palatogenesis. The present study was undertaken to determine if the e nzymes responsible for mediating their degradation, the matrix metalloprote inases (MMP), and their specific inhibitors, the tissue inhibitors of metal loproteinases (TIMP), are temporospatially regulated during murine palatal shelf morphogenesis, Palatal shelves were harvested at gestational days (gd ) 12, 13 and 14. MMPs were identified by gelatin zymography, with and witho ut inhibitors, and the identity of specific bands confirmed by Western blot analysis. TIMPs were identified by reverse zymography. MMP and TIMP messag es were detected using RT-PCR with specific primers to MMPs 2, 3, 7, 9 and 13 and TIMPs 1 and 2. Zymography revealed bands of molecular weights corres ponding to MMPs 2, 7, 9 and 13 at all ages examined; the intensity of these bands increased with developmental age. Western blot analysis established the presence of MMP-3 and its developmental variation in expression. RT-PCR demonstrated the presence of mRNA for all MMPs and TIMP at all sampling ti mes and all but MMP-2 showed developmental variation. Whereas increases in mRNA were detected for MMPs 3, 9, and 13, MMP-7 mRNA decreased between gd 1 2 and 14. The results of this study demonstrate that MMPs 2, 3, 7, 9 and 13 and TIMPs 1 and 2 and their messages are present during the course of pala tal shelf remodelling and that their expression is temporally regulated.