Objective To observe the repair effect and safety of melt stacked 3D printed calcium carbonate(CaCO3)/Polylactic acid(PLA)material loaded with human umbilical cord blood mesenchymal stem cells on cartilage defects in New Zealand white rabbits.Methods CaCO3/PLA material was prepared using melt stacking 3D printing technology,and its microstructure was scanned by electron microscopy.CD90 was qualitatively detected by immunofluorescence of human umbilical cord blood mesen-chymal stem cells.After establishing a rabbit knee joint cartilage defect model,24 experimental rabbits were divided into 4 groups,with 6 rabbits in each group and given different treatments.The control group was given 0.5 mL of phosphate buffer,while the stem cell group was given 0.5 mL of cell suspension(with a cell count of approximately 6.56×106/mL).In the material group the articular cartilage defect was filled with 3D printed CaCO3/PLA material.In the stem cell+material group the 3D printed CaCO3/PLA material was co-cultured with human umbilical cord blood mesenchymal stem cells and 0.5 mL of cell sus-pension was injected.After 8 weeks of intervention,histological hematoxylin eosin and safranin green staining were performed.The repair of knee joint cartilage in each group was evaluated based on staining results combined with ICRS gross score and im-proved Pineda score.Results Melt stacked 3D printed CaCO3/PLA material showed neat vertical and horizontal arrangement in electron microscopy scanning,with a loose porous structure inside and continuous pore channels,with a pore size of 580-800μm.The micro scanning surface presented a three-dimensional structure.The results of CD90 immunofluorescence detection of human umbilical cord blood mesenchymal stem cell marker showed that human umbilical cord blood mesenchymal stem cells were spindle shaped,with oval shaped nuclei inside the cells.The cytoplasm was stained red and the nuclei were stained blue.The average ICRS score of the control group was 1 point,the average score of the stem cell group was 6.5 points,the average score of the material group was 5.5 points,and the average score of the stem cell+material group was 10.8 points.The average improved Pineda score in the control group was 13.17 points,the average score in the stem cell group was 4.01 points,the aver-age score in the material group was 8.01 points,and the average score in the stem cell+material group was 2.66 points.Conclu-sion Melt stacked 3D printed CaCO3/PLA material loaded with human umbilical cord blood mesenchymal stem cells has the ability to repair knee joint cartilage defects,and the material has good tissue compatibility,further proving the feasibility of us-ing tissue engineering methods for cartilage damage repair,as well as the effectiveness and safety of stem cell therapy.
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