Figure 4: Effects of nitric oxide radicals on the differentiation of MSC. MSC were expanded and osteogenic or adipogenic differentiation was induced in the absence or presence of SNP. MSC in expansion media served as the control. A. Incubation of MSC in osteogenic induction medium for 7 days resulted in an increase in expression of the early osteogenic marker Runx2. Addition of SNP to osteogenic induction (daily change of medium containing 1 mM SNP) blocked expression of Runx2. B. However, the expression of the late osteogenic marker osteocalcin was only slightly elevated and NO reduced this small increase to levels recorded in mock controls. C. Upon addition of adipogenic induction medium for 7 days to MSC, expression of the early adipogenic marker PPRg2 was drastically elevated, but a major NO effect was not recorded for adipogenesis (C).