β-Tricalcium Phosphate Micron Particles Enhance Calcification of Human Mesenchymal Stem CellsIn Vitro

Abstract

β-Tricalcium phosphate (β-TCP) micron particles whose diameters range from 1 μm to 10 μm have been recently developed, however, their biological effects remain unknown. We investigated the biological effects ofβ-TCP micron particles on proliferation, cytotoxicity, and calcification of human synovial mesenchymal stem cells (MSCs). MSCs were cultured without dexamethasone,β-glycerophosphate, or ascorbic acid. 1.0 mg/mLβ-TCP micron particles inhibited proliferation of MSCs significantly and increased dead cells. In the contact condition, 0.1 mg/mLβ-TCP micron particles promoted calcification of MSCs evaluated by alizarin red staining and enhanced mRNA expressions of runx2, osteopontin, and type I collagen. In the noncontact condition, these effects were not observed. 0.1 mg/mLβ-TCP micron particles increased calcium concentration in the medium in the contact condition, while 1.0 mg/mLβ-TCP micron particles decreased calcium and phosphorus concentrations in the medium in the noncontact condition. By transmission electron microscopy,β-TCP micron particles were localized in the phagosome of MSCs and were dissolved. In conclusion,β-TCP micron particles promoted calcification of MSCs and enhanced osteogenesis-related gene expressionsin vitro.