Comparison Of Osteogenesis And Vascularization Of Two 3D Printed PCL Scaffolds With Different Structures

Background:3D printing technology can achieve precise control over the pore size and porosity of bone tissue scaffolds.Based on the perspective of nutrient transport and cell-matrix interaction,a large number of scaffolds with different macrostructures were fabricated,which improved the mechanical properties of the scaffolds,enhanced the biological activities of cells,and promoted tissue regeneration.However,problems such as the inability of cells in the scaffold to achieve high-density implanting,precise spatial positioning and distribution,and insufficient oxygen transport still need to be solved.Therefore,improving the scaffold structure to enhance its biological behavior is a hot issue in scaffold design.Objective:This study aimed to compare effects of two types of polycaprolactone（PCL）scaffold structure on bone repair and angiogenesis in a rat calvarial defect model,which may provide new insights into the design of the scaffoldsMethods:1.The two types scaffolds,which had a relatively open structure and a relatively obstructed structure,respectively,were designed and fabricated by using the 3D printing technique.Scanning electron microscopy（SEM）,microcomputed tomography（μ-CT）,and universal tester were performed to evaluate their structure and mechanical properties.2.In vitro,mouse osteoblasts（MC3T3-E1）were seeded onto the pretreated scaffolds.Cell adhesion efficiency was evaluated.Cell viability was analyzed by Live/Dead assay reagent.Cell Counting Kit-8（CCK-8）assay detected the proliferation ability of cells.The cytoskeletal distribution was observed by F-actin staining.3.In vivo,circular calvaria defects（5 mm in diameter）were constructed and implanted the scaffolds.The rats were sacrificed at weeks 1 and 8.The samples were assessed by radiographical evaluation,hematoxylin-eosin（HE）,Masson’s trichrome,CD31 immunohistochemistry,and reverse transcriptase-polymerase chain reaction（RT-PCR）to analyze their effects on bone repair and angiogenesis.Results:1.The two scaffolds were fabricated,denoted as“no shift”with a relatively open structure and“shift”with a relatively obstructed structure.Compression tests showed that the“no shift”scaffolds possessed higher stiffness compared to“shift”scaffolds.2.In vitro:Both scaffolds have good biocompatibility,“shift”scaffolds improved cell adhesion and proliferation compared to“no shift”scaffolds（^*P<0.05）.3.The results of the radiographical evaluation,histological analysis,and RT-PCR revealed that greater vessel circumference and more new bone were observed in the“no shift”group in vivo.Conclusion:Two types of scaffolds were fabricated and both had good biocompatibility.The“shift”scaffolds were more conducive to cell adhesion and proliferation in vitro.While the“no shift”scaffolds were more beneficial to the formation of blood vessels and repairing bone defects in vivo.