ls. Many of the biological effects of resveratrol have already been demonstrated in the literature; these include cardiovascular protection, anticancer activity and stimulation of proliferation and osteoblastic differentiation in human and mouse MSCs. However, its effects on bone are less studied and are particularly 
relevant to this investigation. The sirtuins are highly conserved nicotinamide adenine dinucleotide -dependent enzymes that deacetylate residues of acetylated lysine. These histone deacetylases are involved in deacetylation of histones and non-histone proteins, including transcription factors, proteins and enzymes playing an important role in chromatin architectures, gene expression, control of cellular metabolism and cancer in many species. Mammals possess seven sirtuins, whereas the histone deacetylase Sirt-1 is located in the nucleus and shares identity with Sir2. The activity of the Sirt1 protein is known to be regulated by resveratrol and nicotinamide, which activate and inhibit Sirt-1, respectively. Activation of Sirt-1 decreases adipocyte formation during osteoblastic differentiation of MSCs. PPAR-c, a member of the nuclear receptors has been found to be an important regulator of adipogenesis and plays a MedChemExpress INK-128 central role in fat tissue development, inflammatory responses, cellular proliferation and differentiation, as well as the balance between osteogenesis and adipogenesis. PPAR-c is activated by a wide variety of substances including long chain fatty acids, peroxisome proliferators and thiazolidinedione compounds. In addition, it has been shown that adipocytes and osteoblasts share a common progenitor, i.e., mesenchymal stem cells in which expression of PPAR-c signaling can induce transdifferentiation of osteoblasts to adipocytes in adipogenic medium. Moreover, several nuclear receptors have been found to interact with the nuclear receptor co-repressor and silencing mediator for retinoid and thyroid hormone receptor . Furthermore, these co-repressors are required for the inhibition function of nuclear receptors and transcription factors. The transcription factor, Runt-related transcription factor 2 is one of the earliest and most specific markers during osteogenesis. Runx2 induces osteoblast-specific gene expression in vitro. Different specific signals, like mechanical signals can regulate Runx2 activation stimulating osteoblast differentiation through the activation of the MAPKinase signal-transduction pathway and Ras/Raf-dependent Erk1/2 activation. In this study, we have established an in vitro model of osteogenesis using adipose derived MSCs in monolayer and high-density cultures and present new evidence to show that resveratrol-activated Sirt-1 significantly favors osteogenic differentiation over adipogenic differentiation. The question of whether an interaction between resveratrol-activated Sirt-1 and Runx2 occurs 2 Resveratrol Promotes Osteogenesis of MSCs and whether this causes deacetylation of Runx2 during osteogenesis is an important focus of this study. Materials and Methods Antibodies Polyclonal anti-collagen type I antibody and alkaline phosphatase linked sheep anti-mouse and sheep anti-rabbit secondary antibodies for immunoblotting were purchased from Millipore. Polyclonal anti- Runx2 was purchased from Alpha Diagnostics Int. San Antonio, TX, USA. Monoclonal anti-b-actin and nicotinamide were purchased from SigmaAldrich. Polyclonal anti-Sirt-1 and antiNCoR were purchased from Abcam PLC. Polyclonal anti-P