In vitro effects of nanophase hydroxyapatite particles on proliferation and osteogenic differentiation of bone marrow-derived mesenchymal stem cells.

Coculturing scaffolds with seeded cells in vitro is an indispensable process for construction of engineered tissues. It is essential to understand effects of the constituent particles of scaffold on seeded cells. In this study, we investigated the influence of nano-sized hydroxyapatite (nHAP) particles on the proliferation and osteogenic differentiation of bone marrow-derived mesenchymal stem cells (MSCs). nHAP particles were cocultured with MSCs separated from rabbit. Cellular effects of particles were determined by cell counts, Vonkossa stains, and reverse transcription-polymerase chain reaction (RT-PCR) examinations. Results showed that nHAP particles could promote the MSCs growth when particle concentrations were lower than 20 microg/10(4) cells. This effect disappeared when the particles and the cells were cocultured in serum-free media. Higher particle concentrations could significantly inhibit the cell growth. Under the standard culture condition, the only effect of nHAP particles on osteogenic differentiation of MSCs was to enhance the expression of collagen I. Under the osteogenic-inductive culture condition, nHAP particles could inhibit mineralization of cells but promote their osteogenic differentiation. These cellular effects of particles still existed when the particles and the cells were cultured in indirect coculture system. nHAP particles could decrease calcium and phosphate concentrations of culture media, which possibly contributed to the cellular effects of nHAP particles.