Expression of MMP-2 induced by two bonding systems in HPFs

Objectives: This study aimed to evaluate the effects of two different dentin bonding systems on primary cultures of human pulp fibroblasts (HPFs). Cells viability and expression of procollagen α1 type I and matrix-metalloproteinase 2 (MMP-2) were investigated. Methods: Cured adhesive-disks of the bonding agent of a two-step self-etch (TechBond, Isasan, Italy) and primer/bonding of a two-step etch-and-rinse adhesive (Optibond Solo, KerrHawe, Switzerland) were used for culture medium conditioning for 24 and 96 h. HPFs were then incubated with control or adhesive-conditioned medium for 24 h. HPFs viability was determined using the 3-dimethylthiazol-2,5-diphenyltetrazolium bromide (MTT) assay; Western Blot analysis was performed to analyze procollagen α1 type I protein and MMP-2 expression. Statistical analyses were performed by student's-T test. Results: HFPs incubated with adhesive-conditioned medium for 24 hours showed a percentage of viable cells of 45% for TechBond and 30% for Optibond Solo, whereas this percentage significantly increased after exposure to the 96 h adhesive-conditioned medium (62% and 77%, respectively; p<0.05). For both adhesives, procollagen α1 type I expression in HPFs decreased after incubation with the 24h-conditioned medium, and completely disappeared with the 96h-conditioned medium. MMP-2 expression showed a faint band at 67 KDa, similar for both adhesives, when HPFs were treated with the 24h-conditioned medium, whereas its expression increased after incubation with the 96h-conditioned medium, mainly in the self-etch adhesive-conditioned medium. Conclusion: HPFs exposure to different dental adhesives leads to an early cytotoxic effect (24h-adhesive conditioning) that decreased after 96h-conditioning time. After exposure to 96h adhesive-conditioned media, HPFs response seems to be characterized by an increased MMP-2 expression (especially for the self-etch conditioned HPFs), and a decreased procollagen α1 type I synthesis. It can be speculated that MMP-2 increased expression/activation may also represent a defensive mechanism exhibited by HPFs towards dentin bonding systems.