MMP-2 and MMP-14 Expressions by Epithelial-mesenchymal Inteactions in vitro

Objectives: Epithelial-mesenchymal interactions are responsible for morphogenesis and cell differentiation during periodontal regeneration. Type IV collagen and laminin were found at the interface between cells of the epithelial rests of Malassez (ERM) and fibroblasts from human periodontal ligament (HPDL). MMP-2 can degrade type IV collagen and MMP-14 can activate pro-MMP-2. The current study was undertaken to examine the expression of MMP-2 and MMP-14 by ERM cells and HPDL fibroblasts. Methods: HPDL tissues were sampled from the root of extracted teeth and produced outgrowths containing both ERM cells and HPDL fibroblasts in a modified serum-free MCDB 153 medium. The distribution and expression of MMP-2 and MMP-14 were analyzed by immunohistochemistry, in situ hybridization and RT-PCR. ERM cells cultured alone and HPDL fibroblasts cultured alone were used as control. Results: ERM cells at the interface expressed MMP-2 and MMP-14 protein strongly. On the other hand, in situ hybridization analysis showed that HPDL fibroblasts expressed MMP-2 mRNA and ERM cells expressed MMP-14 mRNA at the interface strongly. RT-PCR analysis demonstrated that the expression of MMP-2 mRNA was significantly higher, when ERM cells and HPDL fibroblasts were co-cultured, than when each of them was cultured alone. On the other hand, the interaction between them did not affect the expression of MMP-14. Conclusion: These findings indicate that ERM cells stimulate the production of MMP-2 in HPDL fibroblasts. Up-regulated MMP-2 activated by MMP-14 expressed in ERM cells could degrade matrix molecules, such as Type IV collagen in the basal membrane between ERM cells and HPDL fibroblasts.