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. 2008 Aug 30;15(2):273–283. doi: 10.1089/ten.tea.2008.0055

FIG. 5.

FIG. 5.

Mitogen-activated protein kinase (MAPK) and phosphatidyl inositol-3-kinase (PI3K) pathways are required for the osteogenic differentiation of mesenchymal stem cells (MSCs) on poly(lactide-co-glycolide) (PLGA) substrates. (A) MSCs were cultured on spin-coated PLGA substrates in OS medium with or without the MAPK pathway inhibitor PD98059 (50 μM) for 1, 7, or 14 days, with the inhibitor replenished at every medium change. Cell lysates analyzed using Western blot for p-MAPK confirmed the pharmacologic inhibition of the MAPK pathway via PD98059. (B) Inhibition of the PI3K pathway via LY294002 (20 μM) generated similar inhibition of that pathway. (C) MSCs cultured on PLGA substrates with or without PD98059 or LY294002 (20 μM) in OS medium show significant reductions in alkaline phosphatase activity. (D) Pharmacologic inhibition of these pathways also induced qualitative reductions in mineral deposition at 14 days, as revealed by von Kossa staining (mineral deposits denoted by black arrows).