BACKGROUND:3D-printed bone tissue engineering scaffolds have obvious advantages in the research and clinical treatment of bone defect repair.As one of the important raw materials for 3D printed bone scaffolds,poly-L-lactic acid has a great potential for application in performing bone defect repair,but clinical patients with different bone defect causative factors have different requirements for the comprehensive performance of poly-L-lactic acid bone scaffolds.OBJECTIVE:To summarize and review the development of 3D printing technology and poly-L-lactic acid scaffolds and the design strategies chosen for scaffolds for bone repair in the setting of bone diseases such as osteomyelitis,bone tumor,osteonecrosis,and osteoporosis.METHODS:Literature from CNKI,WanFang,PubMed,Science Direct,and Web of Science databases were searched and screened from 1994 to 2024.Search terms were"3D printing,polylactic acid,bone tissue engineering scaffold,osteomyelitis,bone tumor,osteonecrosis,osteoporosis,bone defect"in Chinese and English.The screened 62 articles were systematically summarized and analyzed.RESULTS AND CONCLUSION:(1)Poly-L-lactic acid is considered to be an ideal raw material for artificial bone scaffold design due to its non-toxicity,processability,biocompatibility,and ability to self-degrade in the human environment.The application of 3D printing technology has enabled poly-L-lactic acid bone scaffolds to meet the multilayered and porous structural design requirements of biomimetic artificial bone repair materials,and to optimize the mechanical properties for better bone repair.(2)According to different bone disease microenvironments,timely adjustment of the functional design of poly-L-lactic acid scaffolds is important for the comprehensive osteogenic efficacy of the scaffolds.The article discusses the application of poly-L-lactic acid scaffolds in bone disease environments such as osteomyelitis,bone tumor,osteonecrosis,and osteoporosis,and highlights the importance of rationally grasping the timing of bone disease treatment and bone tissue regeneration for bone defects caused by different bone diseases.(3)Although poly-L-lactic acid scaffolds show potential in bone repair,there are still some problems,such as the need to further optimize the structural design of the scaffolds to fit new bone regeneration,enhance the bioactivity of the scaffolds,and take into account other functions(e.g.,antimicrobial,anti-tumor,and anti-osteoporosis)in order to adapt to the needs of bone tissue repair in different pathological environments.

BACKGROUND:3D-printed bone tissue engineering scaffolds have obvious advantages in the research and clinical treatment of bone defect repair.As one of the important raw materials for 3D printed bone scaffolds,poly-L-lactic acid has a great potential for application in performing bone defect repair,but clinical patients with different bone defect causative factors have different requirements for the comprehensive performance of poly-L-lactic acid bone scaffolds.OBJECTIVE:To summarize and review the development of 3D printing technology and poly-L-lactic acid scaffolds and the design strategies chosen for scaffolds for bone repair in the setting of bone diseases such as osteomyelitis,bone tumor,osteonecrosis,and osteoporosis.METHODS:Literature from CNKI,WanFang,PubMed,Science Direct,and Web of Science databases were searched and screened from 1994 to 2024.Search terms were"3D printing,polylactic acid,bone tissue engineering scaffold,osteomyelitis,bone tumor,osteonecrosis,osteoporosis,bone defect"in Chinese and English.The screened 62 articles were systematically summarized and analyzed.RESULTS AND CONCLUSION:(1)Poly-L-lactic acid is considered to be an ideal raw material for artificial bone scaffold design due to its non-toxicity,processability,biocompatibility,and ability to self-degrade in the human environment.The application of 3D printing technology has enabled poly-L-lactic acid bone scaffolds to meet the multilayered and porous structural design requirements of biomimetic artificial bone repair materials,and to optimize the mechanical properties for better bone repair.(2)According to different bone disease microenvironments,timely adjustment of the functional design of poly-L-lactic acid scaffolds is important for the comprehensive osteogenic efficacy of the scaffolds.The article discusses the application of poly-L-lactic acid scaffolds in bone disease environments such as osteomyelitis,bone tumor,osteonecrosis,and osteoporosis,and highlights the importance of rationally grasping the timing of bone disease treatment and bone tissue regeneration for bone defects caused by different bone diseases.(3)Although poly-L-lactic acid scaffolds show potential in bone repair,there are still some problems,such as the need to further optimize the structural design of the scaffolds to fit new bone regeneration,enhance the bioactivity of the scaffolds,and take into account other functions(e.g.,antimicrobial,anti-tumor,and anti-osteoporosis)in order to adapt to the needs of bone tissue repair in different pathological environments.

BACKGROUND:Careful regulation of bone immune response during repair of bone scaffold is important for bone regeneration. OBJECTIVE:To review the influence of bone immune response on bone repair and the design of bone tissue engineering scaffold with regulating bone immune function and its application in bone repair. METHODS:Relevant articles published from 1973 to 2023 were retrieved from Science Direct,PubMed,Web of Science,and CNKI databases.English search terms were"osteoimmunology,macrophages,bone repair materials,bone scaffold,bone defects,bone regeneration".Chinese search terms were"bone immunity,macrophages,bone repair material,bone stent,bone defect,bone regeneration".Totally 80 articles of the latest research progress in this field were summarized and analyzed. RESULTS AND CONCLUSION:(1)A detailed review was conducted on the important time points in the origin and development process of bone immunity,and it was explained that macrophages,as important members of the bone immune regulatory system,can be divided into two phenotypes:M1(pro-inflammatory)and M2(anti-inflammatory),and play a key role in different stages of bone regeneration.During the inflammatory phase,M1 type macrophages can activate osteoclasts,initiate tissue repair processes,and participate in the reconstruction of bone microvascular networks.On the other hand,during the bone tissue regeneration process in the later stages of inflammation,sustained high expression of M1 type macrophages can hinder the formation of new bones.During the repair phase,M2 macrophages can secrete osteogenic cytokines,stimulate osteogenic differentiation and mineralization of bone marrow mesenchymal stem cells,and promote bone formation.On the other hand,long-term activation of M2 macrophages can increase the secretion of fibrogenic molecules,leading to excessive formation of scar tissue and delaying the healing process.Therefore,regulating macrophages to undergo phenotype transformation at appropriate stages and constructing an immune microenvironment beneficial for osteogenesis has great significance for bone regeneration.(2)In the process of designing bone scaffolds with bone immune regulation characteristics,the physical and chemical properties such as scaffold roughness,pore structure,stiffness,hydrophilicity,surface charge,and surface functional groups can be changed to affect non-specific protein and cell adhesion,thereby affecting the interaction between bone scaffolds and the immune system.By designing surface functional coatings of bioactive substances such as hydroxyapatite,bioactive glass,metal ions,extracellular matrix,drugs,cytokines,and exosomes,the immune microenvironment can be actively regulated by releasing bioactive substances after implantation into the body,affecting macrophage polarization and crosstalk between macrophages and bone cells,and promoting more M2 polarization of macrophages,so as to build a bone immune microenvironment that is conducive to bone regeneration.(3)Based on the research and development of bone tissue engineering scaffolds,in addition to focusing on the direct regulatory factors of stem cell osteogenic differentiation,this article also proposes that attention should be paid to the management of the immune microenvironment of stem cell differentiation.By regulating the appropriate bone immune microenvironment,more stem cell osteogenic differentiation can be induced;the osteogenic efficiency of the scaffold can be enhanced,and the concept of"bone immune regulatory characteristics"can be condensed;deeply elucidated the multi-directional regulatory role of the bone immune microenvironment and introduced the existing strategies for changing the physicochemical properties and surface functional coating of scaffolds to endow them with bone immune regulatory potential,providing new ideas for guiding the development of a new generation of bone tissue engineering scaffolds with bone immune regulatory characteristics.However,the bone immune microenvironment is a dynamic equilibrium state,and most of the existing regulatory strategies do not consider the dynamic matching of regulation.Therefore,the research and development of intelligent bone immune regulatory scaffolds with efficient and targeted regulation of the immune microenvironment will be a key focus of attention for scholars in future.