Osteogenically committed hUCMSCs-derived exosomes promote the recovery of critical-sized bone defects with enhanced osteogenic properties.

Low viability of seed cells and the concern about biosafety restrict the application of cell-based tissue-engineered bone (TEB). Exosomes that bear similar bioactivities to donor cells display strong stability and low immunogenicity. Human umbilical cord mesenchymal stem cells-derived exosomes (hUCMSCs-Exos) show therapeutic efficacy in various diseases. However, little is known whether hUCMSCs-Exos can be used to construct TEB to repair bone defects. Herein, PM-Exos and OM-Exos were separately harvested from hUCMSCs which were cultured in proliferation medium (PM) or osteogenic induction medium (OM). A series of in-vitro studies were performed to evaluate the bioactivities of human bone marrow mesenchymal stem cells (hBMSCs) when co-cultured with PM-Exos or OM-Exos. Differential microRNAs (miRNAs) between PM-Exos and OM-Exos were sequenced and analyzed. Furthermore, PM-Exos and OM-Exos were incorporated in 3D printed tricalcium phosphate scaffolds to build TEBs for the repair of critical-sized calvarial bone defects in rats. Results showed that PM-Exos and OM-Exos bore similar morphology and size. They expressed representative surface markers of exosomes and could be internalized by hBMSCs to promote cellular migration and proliferation. OM-Exos outweighed PM-Exos in accelerating the osteogenic differentiation of hBMSCs, which might be attributed to the differentially expressed miRNAs. Furthermore, OM-Exos sustainably released from the scaffolds, and the resultant TEB showed a better reparative outcome than that of the PM-Exos group. Our study found that exosomes isolated from osteogenically committed hUCMSCs prominently facilitated the osteogenic differentiation of hBMSCs. TEB grafts functionalized by OM-Exos bear a promising application potential for the repair of large bone defects.

Prefabricated 3D-Printed Tissue-Engineered Bone for Mandibular Reconstruction: A Preclinical Translational Study in Primate.

The advent of three dimensionally (3D) printed customized bone grafts using different biomaterials has enabled repairs of complex bone defects in various in vivo models. However, studies related to their clinical translations are truly limited. Herein, 3D printed poly(lactic-co-glycolic acid)/ß-tricalcium phosphate (PLGA/TCP) and TCP scaffolds with or without recombinant bone morphogenetic protein -2 (rhBMP-2) coating were utilized to repair primate's large-volume mandibular defects and compared efficacy of prefabricated tissue-engineered bone (PTEB) over direct implantation (without prefabrication). 18F-FDG PET/CT was explored for real-time monitoring of bone regeneration and vascularization. After 3-month's prefabrication, the original 3D-architecture of the PLGA/TCP-BMP scaffold was found to be completely lost, while it was properly maintained in TCP-BMP scaffolds. Besides, there was a remarkable decrease in the PLGA/TCP-BMP scaffold density and increase in TCP-BMP scaffolds density during ectopic (within latissimus dorsi muscle) and orthotopic (within mandibular defect) implantation, indicating regular bone formation with TCP-BMP scaffolds. Notably, PTEB based on TCP-BMP scaffold was successfully fabricated with pronounced effects on bone regeneration and vascularization based on radiographic, 18F-FDG PET/CT, and histological evaluation, suggesting a promising approach toward clinical translation.

Accuracy of Implant Placement Guided with Surgical Template: An In Vitro and In Vivo Study.

This study evaluated the accuracy of implant placement with surgical-template guidance both in vitro and in vivo. Virtual surgical planning was performed based on the data from CBCT scans and an intraoral scanner. Surgical templates were designed according to the planned implants and manufactured with stereolithography. In vitro, 60 implants were placed in 15 resin models. In vivo, 74 implants were placed in 54 patients. The implants were scanned with CBCT postoperatively. Implant accuracy was evaluated by measuring the following parameters: central deviation at the apex and shoulder, horizontal deviation at the apex and shoulder, vertical deviation at the apex and shoulder, and angular deviation. There were statistically significant in vitro and in vivo deviations for all parameters, and the implant deviations in vivo were significantly greater than those in vitro. When using a mucosa-supported template, horizontal deviations at the apex were significantly greater than when a teeth-supported template was used. Within the limitation of the study design, inaccuracy existed in implant placement guided with a surgical template. More studies are needed to investigate the value of the procedure in future.

Bioinspired channeled, rhBMP-2-coated ß-TCP scaffolds with embedded autologous vascular bundles for increased vascularization and osteogenesis of prefabricated tissue-engineered bone.

To date, the recovery of large bone defects is a major clinical challenge despite the availability of numerous therapeutic procedures including tissue engineering. Although there is a pressing need for large tissue-engineered constructs, inadequate vascularization remains an insurmountable barrier for successful clinical translation. Considering that vascularization is a prerequisite for osteogenesis, we proposed an advanced design of large customized porous ß-tricalcium phosphate (TCP) scaffolds with biomimetic vascular hierarchy which upon embedding of femoral axial vascular bundles significantly improved overall vascularity of the scaffolds. Such scaffolds also promoted osteogenesis when they were coated with recombinant bone morphogenetic protein-2 (rhBMP-2). Compared to the conventional TCP scaffolds (S), the newly designed multi-channeled ß-TCP (CS) scaffolds led to adequate blood vessels and bone-like tissue formation throughout their porous hierarchy within 4 weeks of implantation. Especially, the scaffolds coated with rhBMP-2 and embedded with flow-through vascular bundle (FVB) were able to form more uniform vascularized bone within 2 weeks post-implantation. Based on the clinical, radiographic, angiographic and histological assessments, the newly designed multi-channeled scaffolds were found to be promising for successful recovery of large bone defects.

Particulate Coral Hydroxyapatite Sheltered by Titanium Mesh for Localized Alveolar Rehabilitation After Onlay Graft Failure: A Case Report.

Reconstruction of bone loss in the alveolar ridge has long been challenging. Autologous bone grafts are considered as the "golden standard," while little research has focused on how to repair pronounced alveolar bone defects after autologous bone graft failure. The aim of this study was to detail a method based on the titanium mesh technique coupled with particulate coral hydroxyapatite to solve the onlay graft failure. With bone deficiency in the No. 11 and No. 24-25 regions, we harvested 2 autologous bone blocks for reconstruction. Two weeks after transplantation, the graft in the No. 11 region had healed uneventfully, while the graft in the anterior mandible became infected because of soft tissue dehiscence. After removal of the failed autologous bone block, pure coral hydroxyapatite stabilized within titanium mesh was used for alveolar rehabilitation. Six months later, the width of the local alveolar bone was evaluated. After the titanium mesh was removed, a biopsy was performed to study bone regeneration by micro computerized tomography and histology, following by a standard Straumann implant insertion. Although there was wound dehiscence 14 days after bone augmentation, repeated local rinsing and anti-inflammation therapy controlled the inflammatory reaction. The total horizontal bone gain was 4.2 ± 0.5 mm. Micro computerized tomography revealed that the closer the coral hydroxyapatite was to the host bone, the more was resorbed and the more bone regenerated. Histology showed mature lamellar bone structures, with evident residual coral hydroxyapatite. A 3-year follow-up revealed stable bone around the dental implant and successful function of the implant-born prosthesis. This study proposes that the method of particulate coral hydroxyapatite sheltered by titanium mesh is a promising solution in handling alveolar bone augmentation failure. More cases are needed for further research to form an efficient treatment procedure.