Bone defects caused by infection, tumor, trauma, and so on remain difficult to treat clinically. Bone tissue engineering (BTE) has great application prospect in promoting bone defect repair. Polycaprolactone (PCL) is a commonly used material for creating BTE scaffolds. In addition, self-assembling peptides (SAPs) can function as the extracellular matrix and promote osteogenesis and angiogenesis. In the work, a PCL scaffold was constructed by 3D printing, then integrated with bone marrow mesenchymal stem cells (BMSCs) and SAPs. The research aimed to assess the bone repair ability of PCL/BMSC/SAP implants. BMSC proliferation in PCL/SAP scaffolds was assessed via Cell Counting Kit-8.osteogenesis of BMSCs cultured in PCL/SAP scaffolds was assessed by alkaline phosphatase staining and activity assays. Enzyme-linked immunosorbent assays were also performed to detect the levels of osteogenic factors. The effects of BMSC-conditioned medium from 3D culture systems on the migration and angiogenesis of human umbilical vein endothelial cells (HUVECs) were assessed by scratch, transwell, and tube formation assays. After 8 weeks oftransplantation, radiography and histology were used to evaluate bone regeneration, and immunohistochemistry staining was utilized to detect neovascularization.results demonstrated that PCL/SAP scaffolds promoted BMSC proliferation and osteogenesis compared to PCL scaffolds, and the PCL/BMSC/SAP conditional medium (CM) enhanced HUVEC migration and angiogenesis compared to the PCL/BMSC CM.results showed that, compared to the blank control, PCL, and PCL/BMSC groups, the PCL/BMSC/SAP group had significantly increased bone and blood vessel formation. Thus, the combination of BMSC-seeded 3D-printed PCL and SAPs can be an effective approach for treating bone defects. Impact statement Both polycaprolactone (PCL) and self-assembling peptides (SAPs) have been broadly applied in bone defect repair. However, the poor osteoinductivity of PCL and weak mechanical strength of SAPs have limited their clinical application. Here, a 3D-printed PCL scaffold was fabricated for seeding bone marrow mesenchymal stem cells (BMSCs), then combined with SAPs to construct a composite PCL/BMSC/SAP implant for treating the calvarial defect. We showed that transplantation of PCL/BMSC/SAP composite implants clearly promoted bone regeneration and neovascularization. To our knowledge, this is the first study to treat bone defects by combination of BMSC-seeded 3D-printed PCL and SAPs. In vitro in vivo In vitro In vivo
