Jiang Fengjuan, Zhang Yunhe, Peng Fengping, Liu Hui, Ding Kai, Cao Panpan, Liu Xiaohan, Li Lijuan, Liu Zhaoyun, Fu Rong
Department of Hematology, Tianjin Medical University General Hospital, 154 Anshan Street, Heping District, Tianjin, 300052, China.
Tianjin Key Laboratory of Bone Marrow Failure and Malignant Hemopoietic Clone Control, Tianjin, 300052, China.
J Transl Med. 2025 Mar 16;23(1):338. doi: 10.1186/s12967-025-06319-3.
Myeloma bone disease (MBD) is the most common complication of multiple myeloma (MM). Our previous study showed that the complement C3a activates osteoclasts to participate in the pathogenesis of MBD; however, its mechanism of action is diverse and complex. Studies have shown that the Sirtuin (Sirt) family of proteins (i.e., Sirt1-7) are expressed in human bone and cartilage, and participate in bone metabolic balance.
We measured the levels of complement C3a, Sirt1, osteoclast-related genes, and bone disease-related biological indicators using enzyme-linked immunosorbent assay (ELISA), quantitative real-time PCR and western blotting. Sirt1 expression in osteoclasts was observed to be lower in patients with MM compared to healthy donors and negatively correlated with complement C3a levels, osteoclast-related gene expression, and osteolysis-related markers. Co-immunoprecipitation (Co-IP) and immunostaining were used to verify the interaction between C3a and Sirt1 in RAW264.7 cells. Osteoclasts were then induced from bone marrow mononuclear cells (BMMCs) in patients with MM or cultured RAW264.7 cells, using C3a and/or Sirt1 activator (SRT1720)/inhibitors (EX527) in vitro. Sirt1 inhibits osteoclast formation and complement C3a reverses this inhibitory function of Sirt1 to activate osteoclasts. RAW264.7 cells with induced overexpression or knockdown Sirt1 were transfected with plasmid or shRNA, and RNA-seq analysis was performed. Increased Sirt1 expression resulted in the inhibition of the PI3K/PDK1/SGK3 pathway, which could be reactivated by complement C3a. Sirt1 knockdown activated the PI3K/PDK1/SGK3 pathway, which was further enhanced by complement C3a. A mouse model of MBD was successfully constructed. We injected this model with complement C3a or SRT1720, which further verified that complement C3a can significantly increase the degree of MBD bone damage, whereas SRT1720 can reduce the bone damage aggravated by C3a and treat MBD.
We demonstrated that complement C3a interacts with Sirt1 in osteoclasts to participate in the pathogenesis of MBD. Complement C3a promotes osteoclast formation by inhibiting Sirt1 to activate the PI3K/PDK1/SGK3 pathway in patients with MM, which is reduced by treatment with a Sirt1 activator. The application of a Sirt1 activator can reduce the formation of osteoclasts and reduce the severity of bone diseases in vivo and may be useful for the treatment of MBD. This study identified novel potential therapeutic targets and strategies for patients with MBD.
骨髓瘤骨病（MBD）是多发性骨髓瘤（MM）最常见的并发症。我们之前的研究表明，补体C3a激活破骨细胞参与MBD的发病机制；然而，其作用机制多样且复杂。研究表明，沉默调节蛋白（Sirt）家族蛋白（即Sirt1 - 7）在人骨和软骨中表达，并参与骨代谢平衡。
我们使用酶联免疫吸附测定（ELISA）、定量实时PCR和蛋白质印迹法测量补体C3a、Sirt1、破骨细胞相关基因和骨病相关生物学指标的水平。观察到MM患者破骨细胞中Sirt1表达低于健康供体，且与补体C3a水平、破骨细胞相关基因表达和骨溶解相关标志物呈负相关。采用免疫共沉淀（Co - IP）和免疫染色验证RAW264.7细胞中C3a与Sirt1的相互作用。然后在体外使用C3a和/或Sirt1激活剂（SRT1720）/抑制剂（EX527）从MM患者的骨髓单个核细胞（BMMCs）或培养的RAW264.7细胞诱导破骨细胞。Sirt1抑制破骨细胞形成，补体C3a逆转Sirt1的这种抑制功能以激活破骨细胞。对诱导过表达或敲低Sirt1的RAW264.7细胞进行质粒或shRNA转染，并进行RNA测序分析。Sirt1表达增加导致PI3K/PDK1/SGK3通路受到抑制，补体C3a可使其重新激活。Sirt1敲低激活PI3K/PDK1/SGK3通路，补体C3a可进一步增强该通路。成功构建了MBD小鼠模型。我们向该模型注射补体C3a或SRT1720，进一步验证补体C3a可显著增加MBD骨损伤程度，而SRT1720可减轻C3a加重的骨损伤并治疗MBD。
我们证明补体C3a与破骨细胞中的Sirt1相互作用参与MBD的发病机制。补体C3a通过抑制Sirt1激活MM患者的PI3K/PDK1/SGK3通路来促进破骨细胞形成，而Sirt1激活剂治疗可减轻这种作用。Sirt1激活剂的应用可减少破骨细胞形成并减轻体内骨病严重程度，可能对MBD治疗有用。本研究为MBD患者确定了新的潜在治疗靶点和策略。
