Department of Pediatric Dentistry, Hospital of Stomatology, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China.
Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China.
Int J Biochem Cell Biol. 2021 May;134:105962. doi: 10.1016/j.biocel.2021.105962. Epub 2021 Feb 23.
SIRT4 is a mitochondrial sirtuin. Owing to its dependance on the cofactor nicotinamide adenine dinucleotide (NAD), SIRT4 can act as a mitochondrial metabolic sensor of cellular energy status. We have previously shown that enhancement of mitochondrial functions is vital for the odontogenic diff ;erentiation of dental papilla cells (DPCs) during dentinogenesis. However, whether SIRT4 serves as an effective regulator of DPC diff ;erentiation by affecting mitochondrial functions remains unexplored.
Primary DPCs obtained from the first molar dental papilla of neonatal Sprague-Dawley rats were used in this study. The expression pattern of SIRT4 was observed by immunohistochemistry in the first molar of postnatal day 1 (P1) rats. The changes in SIRT4 expression during odontogenic DPC differentiation were evaluated using real-time quantitative polymerase chain reaction (PCR), western blotting, and immunofluorescence. DPCs with loss (small interfering RNA-mediated knockdown) and gain (plasmid transfection-induced overexpression) of SIRT4 function were used to explore the role of SIRT4 in odontogenic differentiation. Mitochondrial function assays were performed using ATP, reactive oxygen species (ROS), and NAD/NADH kits to investigate the potential mechanisms involved in SIRT4-mediated dentinogenesis.
In the present study, we found that SIRT4 expression increased in a time-dependent manner during odontogenic differentiation bothin vivo and in vitro. Sirt4 knockdown resulted in reduced odontogenic differentiation and mineralization, whereas an opposite effect was observed with SIRT4 overexpression. Furthermore, our results verified that in addition to reducing DPC differentiation, Sirt4 knockdown could also significantly reduce ATP levels, elevate the NAD/NADH ratio, and increase ROS levels.
SIRT4 regulates mitochondrial functions and the antioxidant capacity of DPCs, thereby influencing dentin formation and tooth development, a phenomenon that may provide a foundation for better understanding the specific molecular mechanisms underlying dentin regeneration.
SIRT4 是一种线粒体去乙酰化酶。由于其依赖于辅助因子烟酰胺腺嘌呤二核苷酸（NAD），SIRT4 可以作为细胞能量状态的线粒体代谢传感器。我们之前已经表明，增强线粒体功能对于牙本质形成过程中牙髓细胞（DPC）的牙源性分化至关重要。然而，SIRT4 是否通过影响线粒体功能作为 DPC 分化的有效调节剂尚不清楚。
本研究使用来自新生 Sprague-Dawley 大鼠第一磨牙牙髓乳头的原代 DPC。通过免疫组织化学观察 SIRT4 在出生后第 1 天（P1）大鼠第一磨牙中的表达模式。使用实时定量聚合酶链反应（PCR）、western blot 和免疫荧光评估 SIRT4 在牙源性 DPC 分化过程中的表达变化。使用小干扰 RNA 介导的敲低（small interfering RNA-mediated knockdown）和质粒转染诱导的过表达（plasmid transfection-induced overexpression）来研究 SIRT4 在牙源性分化中的作用。使用 ATP、活性氧（reactive oxygen species，ROS）和 NAD/NADH 试剂盒进行线粒体功能测定，以研究 SIRT4 介导牙本质形成过程中涉及的潜在机制。
在本研究中，我们发现 SIRT4 表达在体内和体外牙源性分化过程中呈时间依赖性增加。Sirt4 敲低导致牙源性分化和矿化减少，而 SIRT4 过表达则观察到相反的效果。此外，我们的结果证实，除了降低 DPC 分化外，Sirt4 敲低还可以显著降低 ATP 水平，提高 NAD/NADH 比值，并增加 ROS 水平。
SIRT4 调节 DPC 的线粒体功能和抗氧化能力，从而影响牙本质形成和牙齿发育，这一现象可能为更好地理解牙本质再生的特定分子机制提供基础。
