Li Zhi-Zheng, Wang Hai-Tao, Lee Grace Y, Yang Ying, Zou Yan-Ping, Wang Bing, Gong Chu-Jie, Cai Yu, Ren Jian-Gang, Zhao Ji-Hong
The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) & Key Laboratory of Oral Biomedicine Ministry of Education, School & Hospital of Stomatology, Wuhan University, Wuhan, China.
Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Br J Pharmacol. 2021 Jan;178(2):312-327. doi: 10.1111/bph.15281. Epub 2020 Dec 13.
Tooth eruption is a complicated process regulated by the dental follicles (DF). Our recent study discovered that tooth eruption was inhibited upon injection of bleomycin into DF. However, the mechanisms were unknown.
Human dental follicle cells (hDFCs) were treated by bleomycin or exogenous TGF-β1 or transfected by plasmids loading SMAD7 or shRNA targeting SMAD7, followed by osteogenesis induction assay and signalling analysis. Human fresh DF tissues and Wistar rats were used to further confirm bleomycin function.
Bleomycin decreased expression of RUNX2 and osteogenic genes in hDFCs, reducing osteogenic capacity. TGF-β1 expression was up-regulated in bleomycin-treated hDFCs. The effects of exogenous TGF-β1 were similar to those of bleomycin in hDFCs. Additionally, compared to SMAD2/3, SMAD7 expression increased more in bleomycin- or TGF-β1-treated hDFCs. Overexpression of SMAD7 likewise significantly decreased RUNX2 expression and osteogenic capacity of hDFCs. Knockdown of SMAD7 markedly attenuated the inhibitory effects of bleomycin and TGF-β1 on osteogenic capacity and RUNX2 expression of hDFCs. Most importantly, changes in TGF-β1, SMAD7, and RUNX2 expressions were similar in the DF of rats and humans treated with bleomycin.
SMAD7 was a negative regulator of osteogenic differentiation in DFCs through suppressing RUNX2 expression. Bleomycin or TGF-β1 inhibited osteogenic differentiation of DFCs via a TGF-β1/SMAD7/RUNX2 pathway. Our findings might be beneficial for enhancing the osteogenic activity of DFCs or inhibiting the eruption of undesirable teeth.
牙齿萌出是一个由牙囊（DF）调控的复杂过程。我们最近的研究发现，向牙囊中注射博来霉素会抑制牙齿萌出。然而，其机制尚不清楚。
用博来霉素或外源性转化生长因子-β1（TGF-β1）处理人牙囊细胞（hDFCs），或用加载SMAD7的质粒或靶向SMAD7的短发夹RNA（shRNA）转染hDFCs，随后进行成骨诱导试验和信号分析。用人新鲜牙囊组织和Wistar大鼠进一步证实博来霉素的作用。
博来霉素降低了hDFCs中RUNX2和成骨基因的表达，降低了成骨能力。在博来霉素处理的hDFCs中，TGF-β1表达上调。外源性TGF-β1在hDFCs中的作用与博来霉素相似。此外，与SMAD2/3相比，在博来霉素或TGF-β1处理的hDFCs中，SMAD7表达增加更多。SMAD7的过表达同样显著降低了hDFCs的RUNX2表达和成骨能力。敲低SMAD7显著减弱了博来霉素和TGF-β1对hDFCs成骨能力和RUNX2表达的抑制作用。最重要的是，在用博来霉素处理的大鼠和人的牙囊中，TGF-β1、SMAD7和RUNX2表达的变化相似。
SMAD7通过抑制RUNX2表达是牙囊细胞成骨分化的负调节因子。博来霉素或TGF-β1通过TGF-β1/SMAD7/RUNX2途径抑制牙囊细胞的成骨分化。我们的发现可能有助于增强牙囊细胞的成骨活性或抑制不必要牙齿的萌出。
