Application and development of bone tissue engineering scaffolds with bone immune regulatory properties in repairing bone defects / 中国组织工程研究

ABSTRACT

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.