Figure 4. Blocking integrin αv or integrin β1 accelerates the adipogenic differentiation and retards the osteogenic differentiation of wild-type MSCs.

(A) Expression levels of various integrin subunits by wild-type MSCs or OPN^-/- MSCs were determined by flow cytometry using subunit-specific polyclonal antibodies: integrin β1, β3, β5, αv, α4, α8, α9. (B, C, and D) Wild-type MSCs supplemented with blocking antibodies against integrin β1 or CD44, or an isotype control (each 10 μg/ml) were cultured in adipogenic differentiation medium for 6 days and stained with Oil Red O (bar: 100 μm; adipocytes counted in six random fields from four wells per group) (B and C), or in osteogenic differentiation medium for 24 days and stained with Alizarin Red S (D). (E and F) Wild-type MSCs were cultured in control medium or adipogenic differentiation medium supplemented with cyclic RGD (10 μM) or solvent (acetic acid) for 6 days, then stained with Oil Red O (bar: 100 μm) (E). Adipocytes were quantitated as described above (F). ns, not significant; ***, P < 0.001. Representative of three independent experiments.