Compensatory Cellular Reactions to Non-Steroidal Anti-Inflammatory Drugs on Osteogenic Differentiation in Canine Bone Marrow-Derived Mesenchymal Stem Cells

Abstract

Suppressive effects of non-steroidal anti-inflammatory drugs (NSAIDs) on bone healing process have remained controversial, since no clinical data have clearly showed the relationship between NSAIDs and bone healing. The aim of this study was to assess compensatory response of canine bone marrow-derived mesenchymal stem cells (BMSCs) to several classes of NSAIDs, including carprofen, meloxicam, indomethacin and robenacoxib on osteogenic differentiation. Each of NSAIDs (10 µM) was treated during 20 days of osteogenic process with human recombinant IL-1β (1 ng/ml) as an inflammatory stimulator. Gene expression of osteoblast differentiation markers (alkaline phosphatase and osteocalcin), receptors of PGE₂ (EP2 and EP4) and enzymes for prostaglandin (PG) E2 synthesis (COX-1, COX-2, cPGES and mPGES-1) was measured by using quantitative reverse transcription-polymerase chain reaction. Protein production levels of alkaline phosphatase, osteocalcin and PGE₂ were quantified using alkaline phosphatase activity assay, osteocalcin immunoassay and PGE₂ immunoassay, respectively. Histologic analysis was performed using alkaline phosphatase staining, von Kossa staining and alizarin red staining. Alkaline phosphatase and calcium deposition were suppressed by all NSAIDs. However, osteocalcin production showed no significant suppression by NSAIDs. Gene expression levels of PGE₂-related receptors and enzymes, which were up-regulated during continuous treatment of NSAIDs, while certain channels for PGE₂ synthesis were utilized differently depending on the kind of NSAIDs. These data suggest that canine BMSCs have compensatory mechanism to restore PGE₂ synthesis, which would be an intrinsic regulator to maintain differentiation of osteoblasts under NSAIDs treatment.