Fig. 5

Indirect effect of HAPs on extracellular calcium deposition and ALP activity. hWJ-MSCs were incubated in osteogenic medium for 14 d. a Extracellular calcium deposition was then visualized via ARS staining; b ALP activity of the hWJ-MSCs was assessed via ALP staining, scale bars: 200 μm. c Western blot analysis indicated the expression of RUNX-2 and COL I of hWJ-MSCs in osteogenic medium on day 7. d Densitometric measurements of RUNX-2 and COL I from part (c). Cells incubated in osteogenic medium without HAPs treatment were used as the control group. *P < 0.05; **P < 0.01; ***P < 0.001 versus control group; ^&P < 0.05; ^&&&P < 0.001 versus the m-HAP group; ^###P < 0.001 versus the np20 group. Abbreviations: HAPs hydroxyapatite particles, m-HAP micro-sized HAP particles, hWJ-MSCs human umbilical cord Wharton’s jelly-derived mesenchymal stem cells, ALP alkaline phosphatase