Sirtuin-1 (SIRT1) Is Required for Promoting Chondrogenic Differentiation of Mesenchymal Stem Cells [Developmental Biology]

June 24th, 2014 by Buhrmann, C., Busch, F., Shayan, P., Shakibaei, M.

Sirtuin-1 (SIRT1), a nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase, has been linked to anabolic effects in cartilage, while the mechanisms of SIRT1 signaling during differentiation of mesenchymal stem cells (MSCs) to chondrocytes are poorly understood. Therefore, we investigated the role of SIRT1-mediated signaling during chondrogenic differentiation of MSCs in vitro. High-density and alginate cultures of MSCs were treated with chondrogenic induction medium with/without SIRT1-inhibitor nicotinamide (NAM), antisense oligonucleotides against SIRT1 (SIRT1-ASO), IL-1β or/and resveratrol. Transient transfection of MSCs with SIRT1-ASO, NAM and IL-1β inhibited chondrogenesis, induced down-regulation of cartilage specific proteins, cartilage specific transcription factor Sox9 and enhanced NF-kappaB-regulated gene products involved in the inflammatory and degradative processes in cartilage (MMPs, COX-2, caspase-3), NF-kappaB-phosphorylation, -acetylation and activation of IkappaBα kinase. In contrast, SIRT1 activator resveratrol or BMS-345541 (inhibitor of IKK) inhibited IL-1β- and NAM-induced suppression of cartilage specific proteins, Sox9 and up-regulation of NF-kappaB-regulated gene products. Moreover, SIRT1 was found to interact directly with NF-kappaB and resveratrol suppressed IL-1β- and NAM-, but not SIRT1-ASO-induced NF-kappaB-phosphorylation, -acetylation and activation of IkappaBα kinase. Knockdown of SIRT1 by mRNA abolished the inhibitory effects of resveratrol on inflammatory and apoptotic signaling and Sox9 expression, suggesting the essential role of this enzyme. Finally, the modulatory effects of resveratrol were found to be mediated at least in part by the association between SIRT1 and Sox9. These results indicate for the first time that SIRT1 supports chondrogenic development of MSCs at least in part through inhibition/deacetylation of NF-kappaB and activation of Sox9.