RESUMO
BACKGROUND:Toll-like receptors are an important class of pattern recognition receptors that have important functions in pathogen immunity and cytokine synthesis by recognizing specific molecular patterns.Previous studies have found that different types of bone tissue cells also express Toll-like receptors.Activation or inhibition of Toll-like receptors can have significant effects on osteoblast and osteoclast function through multiple pathways. OBJECTIVE:To summarize the expression and action pathways of Toll-like receptors in osteoblasts and osteoclasts,in order to further elucidate the biological mechanisms involved in the regulation of Toll-like receptors under physiological and pathological conditions. METHODS:Relevant literature was retrieved from databases such as PubMed and CNKI as of December 2022.The Chinese and English search terms included"Toll-like receptor,osteoblast,osteoclast,mesenchymal stem cells,macrophage,cytokine,signaling pathway".According to the research needs,the corresponding criteria were established to screen the final literature. RESULTS AND CONCLUSION:(1)Toll-like receptors could directly regulate osteoblast and osteoclast differentiation through the activation of related signaling pathways.(2)Toll-like receptor activation induces cytokine production and exerts regulatory effects.(3)Toll-like receptor activation can affect the survival and migration ability of osteoblasts and osteoclasts.(4)Toll-like receptors in osteoblasts and osteoclasts are activated in certain diseases and pathological settings and are involved in intercellular interactions.
RESUMO
BACKGROUND:Tumor necrosis factor-α is a broadly acting inflammatory cytokine that plays an important role in the immune inflammatory response of the body.The current study concluded that tumor necrosis factor-α has significant biological effects on a variety of bone tissue cells. OBJECTIVE:To summarize the expression and action pathways of tumor necrosis factor-α in osteoblastic and osteoclastic cells to further elucidate the regulatory role of tumor necrosis factor-α on bone tissue cells. METHODS:PubMed and CNKI were searched until March 2023,and the Chinese search terms included"tumor necrosis factor α,osteoblast,osteoclast,osteoclast,osteoprogenitor";the English search terms included"TNF-α,osteoblast,osteoclast,osteocyte,osteoprogenitor cell".The corresponding criteria were established according to the research needs,and the final literature was screened.Finally,77 articles were included for review. RESULTS AND CONCLUSION:(1)Tumor necrosis factor-α is participating in regulating the recruitment,appreciation,and differentiation of osteoprogenitor cells,but leads to osteoprogenitor cell stripping and death under specific environments.It also participates in bone resorption directly or indirectly through secreted enzymes.(2)Tumor necrosis factor-α can increase the level of inflammatory factors in the environment by activating relevant signaling pathways in osteoclast lineage cells or directly induce the generation of osteoclasts in specific environments.(3)Tumor necrosis factor-α can inhibit osteogenic differentiation by activating nuclear factor-κB signaling pathway,inhibiting the expression of transcription factors such as RUNX2 and Osterix,and inducing apoptosis and necrotizing apoptosis in osteoblasts.(4)Tumor necrosis factor-α inhibits osteogenesis and promotes osteoclastogenesis by activating the nuclear factor-κB signaling pathway in osteocytes and inducing cytokines such as RANKL,SOST,and DKK1,while enhancing apoptosis of the osteocytes,as well as bone resorption around the apoptotic bone tissue.(5)Taken together,the effect of tumor necrosis factor-α in bone tissue is mainly to inhibit osteogenesis and promote osteoclastosis.The biological effect of tumor necrosis factor-α in bone tissue cells is usually dependent on the activation of tumor necrosis factor receptor and nuclear factor-κB signaling pathways.(6)The interaction of tumor necrosis factor-α with other tissue cell types surrounding bone tissue and its role in bone immune regulation still deserve attention in future studies.