Western blot of intracellular signaling molecules expressed by hMSCs cultured on Col-GAG and MC-GAG in the absence and presence of PD98059. Western blot of A) phosphorylated Smad1/5 (P-Smad1/5) and total Smad (Smad5), phosphorylated ERK1/2 (P-ERK1/2) and total ERK1/2 (ERK1/2), phosphorylated JNK1/2 (P-JNK1/2) and total JNK1/2 (JNK1/2), Runx2 and B) phosphorylated p38 (p-p38) and total p38, phosphorylated Akt (p-Akt) and total Akt, and actin in hMSCs cultured on Col-GAG and MC-GAG at days 0, 4, 14, and week 4 of culture with and without 50 μm PD98059.