Epigenetic modification is a key driver of differentiation and the deacetylase Sirtuin1 (SIRT1) is an established regulator of cell function, ageing and articular cartilage homeostasis. Here we investigate the role of SIRT1 during development of chondrocytes by using human embryonic stem cells (hESCs). HESC-chondroprogenitors were treated with SIRT1 activator; SRT1720, or inhibitor; EX527, at different development stages. Activation of SIRT1 during 3D-pellet culture led to significant increases in expression of ECM genes for type-II collagen (COL2A1) and aggrecan (ACAN), and chondrogenic transcription factors SOX5 and ARID5B, with SOX5 ChIP analysis demonstrating enrichment on the ACAN -10 enhancer. Unexpectedly, while ACAN was enhanced, GAG retention in the matrix was reduced when SIRT1 was activated. Significantly, ARID5B and COL2A1 were positively correlated, with Co-IP indicating binding of ARID5B to SIRT,1 suggesting that COL2A1 expression is promoted by an ARID5B and SIRT1 interaction. In conclusion, SIRT1 activation positively impacts on the expression of the main ECM components, whilst mitigating ECM organization and GAG content during cartilage development. These results suggest that SIRT1 activity is beneficial to cartilage development and matrix synthesis, but that use in cartilage regeneration would require tailoring.

中文翻译：

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SIRT1活性协调hESC软骨分化过程中的ECM表达。

表观遗传修饰是分化的关键驱动力，而脱乙酰基酶Sirtuin1（SIRT1）是细胞功能，衰老和关节软骨稳态的成熟调节剂。在这里，我们通过使用人类胚胎干细胞（hESCs）研究SIRT1在软骨细胞发育过程中的作用。用SIRT1激活剂处理HESC软骨生成器；SRT1720或抑制剂；EX527，处于不同的开发阶段。在3D颗粒培养过程中SIRT1的激活导致II型胶原（COL2A1）和蛋白聚糖（ACAN）以及软骨形成转录因子SOX5和ARID5B的ECM基因表达显着增加，其中SOX5 ChIP分析证明了ACAN -10的富集增强剂。出乎意料的是，虽然提高了ACAN，但激活SIRT1时，GAG在基质中的保留却降低了。重要的是 ARID5B和COL2A1正相关，Co-IP表示ARID5B与SIRT结合，1提示ARID5B和SIRT1相互作用促进了COL2A1表达。总之，SIRT1激活可积极影响主要ECM成分的表达，同时在软骨发育过程中减轻ECM组织和GAG含量。这些结果表明，SIRT1活性有益于软骨发育和基质合成，但是在软骨再生中的使用将需要定制。