| The overall prognosis of osteosarcoma patients has not improved significantly in the past40 years.One of the important reasons is the lack of an animal model close to the clinical characteristics of osteosarcoma,which leads to little understanding of the cellular and molecular mechanisms of the occurrence,development,metastasis and immune escape of osteosarcoma.At the same time,hyperthermia has become one of the new tumor treatment methods which have received great attention besides traditional surgery,chemotherapy and radiotherapy.Microwave thermal ablation is more and more used in the treatment of bone tumors because of its special advantages in bone tissue.However,due to the slow rate of osseointegration and frequent fracture after microwave thermal ablation of bone tumors,its further application is limited.Therefore,in this study,based on the heterogeneity of osteosarcoma,we domesticated and screened the UMR-106 osteosarcoma cell line and / or tumor block with immune tolerance through the autoimmunity of SD rats,and then used it to construct the rat osteosarcoma model in situ.Secondly,based on the model of bone tumor in situ,the process of microwave thermal ablation for bone tumor was simulated,and the process of reactivation of ablated bone after ablation was systematically studied.Finally,the tissue engineering materials were designed according to the influencing factors of the repair and integration process of ablated bone.The tissue engineering materials were evaluated in vivo and in vitro,and finally verify their promoting effect on ablated bone of osseointegration and osteogenesis in animal models.Through the design and optimization of tissue engineering materials,we hope to provide possible solutions for clinical problems.The main contents and conclusions of this study are as follows:1)Construction of bone tumor model in situ.The immune tolerant UMR-106 tumor cell line and/or tumor tissue were used to establish an in situ osteosarcoma model of distal femur in SD rats.The tumor growth pattern was evaluated from imaging and histopathology.The animal model of osteosarcoma in situ constructed by this method is easy to operate,with high tumorigenic rate and short tumorigenic time.The tumorigenic rate in two weeks is 100%.The model tumor has the clinical characteristics of osteosarcoma: bone destruction,osteolysis,lung metastasis and tumor osteogenesis.Because the model animal has immunity and the osteosarcoma on the model grows in the bone microenvironment,it can better reflect the interaction between the host and the tumor,and is more in line with the growth and metastasis mode of clinical osteosarcoma.It provides an animal model for the in-depth study of osteosarcoma in the later stage,especially for the immune-related research of osteosarcoma.In addition,we also used VX2 tumor to construct tumor model in situ of bone in the New Zealand white rabbit,because of its large size,it can better simulate the process of clinical microwave thermal ablation for bone tumor.The tumor formation rate of VX2 tumor in femoral condyle and radial cortex of New Zealand white rabbits was 100%.The tumor formation rate was fast,and it had clinical osteosarcoma related oncological behaviors,such as bone destruction and osteolysis.New Zealand white rabbits are large and convenient for osteosarcoma related research which needs surgical operation.2)Study on the factors influencing the reactivation of the ablated bone after microwave thermal ablation of bone tumors.On the basis of in situ osteosarcoma model,the clinical process of microwave thermal ablation of osteosarcoma was simulated.The bone after ablation was detected and analyzed by Hematology,Histocytology,Imaging and Histopathology.We draw the following conclusions: First of all,the outer periosteum plays an absolute leading role in the reactivation of ablated bone.The stem cells from the outer periosteum and the tartrate resistant acid phosphatase positive cells in the outer periosteum participate in the whole process of reactivation of ablated bone after ablation.No tartrate resistant acid phosphatase positive cells were found in the inner periosteum,and no callus formation was found in the process of reactivation of ablated bone after ablation.It is speculated that the inner periosteum does not participate in the process.The reactivation of ablated bone begins from the outer periosteum,and then from the outside to the inside and / or starts from the junction of normal periosteum and ablated bone and crawls to the ablated bone.Therefore,the outer periosteum,especially the stem cells and tartrate resistant acid phosphatase positive cells in the outer periosteum,play a leading role in the process of inactivated bone reactivation.Secondly,the ablated bone also undergoes a slow process of reactivation.The reactivation begins in the Haversian canal,accompanied by the growth of vascular endothelial cells and osteoclasts,and then the osteocytes infiltrate into the deep layer of the ablated bone along the Haversian canal.Compared with periosteum,the reactivation process of ablated bone through internal Haversian canal is relatively slow,which also is one of the important factors affecting the reactivation of ablated bone.3)Design and evaluation of tissue engineering materials for promoting reactivation of ablated bone.According to the factors that affect the reactivation and repair of ablated bone after microwave thermal ablation,the corresponding bone tissue engineering materials were designed: SDF-1?/CGRP-nHA/SF artificial periosteum and nHA/PDA/CMCS based 3D printing scaffold loaded with SDF-1?/CGRP factor.It was evaluated from material science,in vitro cytology and in vivo experiments.The results show that: j In vitro experiments showed that SDF-1?/CGRP-nHA/SF artificial periosteum had good hydrophilicity,biocompatibility,mechanical properties and factor loading capacity.SDF-1?/CGRP-nHA/SF artificial periosteum has a good chemotaxis effect on rPDSC and promotes bone differentiation;through co-culture with HUVEC cells,it shows a good role in promoting angiogenesis.Animal experiments show that SDF-1?/CGRP-nHA/SF artificial periosteum has a good ability to promote the reactivation of ablated bone.k 3D printing nHA/PDA/CMCS bone filled scaffold based on micro-nano hydroxyapatite,carboxymethyl chitosan and polydopamine has good photothermal properties,mechanical properties,bone differentiation promoting properties,and photothermal anti-tumor properties in vivo and in vitro.The nHA/PDA/CMCS scaffolds loaded with SDF-1?/CGRP not only have the above excellent properties as nHA/PDA/CMCS scaffolds,but also have significant chemotactic effect on rPDSC by releasing SDF-1?/CGRP.The chemotaxis of nHA/PDA/CMCS scaffolds with SDF-1?/CGRP was 5 times higher than that of nHA/PDA/CMCS scaffolds without SDF-1?/CGRP.Animal experiments further confirmed that the nHA/PDA/CMCS based 3D printing scaffolds loaded with SDF-1?/CGRP had a good promoting effect on the reactivation of ablated bone.In conclusion,this study provides an immunocompetent animal model of osteosarcoma in situ for clinical osteosarcoma research;Secondly,based on the animal model of bone tumor in situ,we systematically studied the process of reactivation and repair of ablated bone after microwave ablation,and found two main factors affecting the reactivation of ablated bone:periosteum and vascularization.According to these two factors,nHA/SF artificial periosteum and nHA/PDA/CMCS 3D printing scaffold,loaded with SDF-1? / CGRP factor,were designed and synthesized.To provide a possible solution to the problem of bone repair after microwave ablation of bone tumors. |
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