Role of Protease Activated Receptor Type 1 (PAR₁) on the Osteogenic Activity of Human Periodontal Ligament Cells

Objectives: The aim of this study was to evaluate the effect of PAR₁ on the extracellular matrix mineralization in human periodontal ligament (PDL) cells.

Methods: Human PDL cells, obtained from 3 subjects, were stimulated with thrombin for 7 and 14 days. PDL cells were seeded at a density of 2x10⁴/cm² and treated with a control medium (α-MEM, 15% fetal bovine serum, 2 mM L-glutamine, 100 U/mL of penicillin, 100 µg/ml of streptomycin and 0.5mg/mL of amphotericin B) or with an osteogenic medium (control medium + Dexamethasone and β-glycerophosphate). Extracellular matrix mineralization (calcium deposits) was assessed by Alizarin Red S staining in the presence of thrombin (0,1 U/ml), PAR₁ specific agonist peptide (100nM) and PAR₁ antagonist peptide (100 nM).

Results: At 7 days, no significant differences were found between treatments. At 14 days, the results showed that treatment with osteogenic medium plus thrombin or PAR₁ specific agonist promoted extracellular matrix mineralization, with no significant difference between these treatments. In addition, PAR₁ blockage by its specific antagonist prevented the formation of extracellular matrix mineralization.

Conclusions: The present study demonstrates that PAR₁ inactivation prevented the formation of calcium deposits, suggesting that PAR₁ plays a role in bone formation.