The reconstruction of severe alveolar bone defects remains a complex and challenging field for clinicians. Three-dimensional-printed scaffolds can adapt precisely to the complicated shape of the bone defects, which is an alternative solution to bone tissue engineering. Our previous study constructed an innovative low-temperature 3D-printed silk fibroin/collagen I/nano-hydroxyapatite (SF/COL-I/nHA) composite scaffold with a stable structure and remarkable biocompatibility. However, the clinical translation of most scaffolds is limited by insufficient angiogenesis and osteogenesis. In this study, we investigated the effects of human umbilical cord mesenchymal-stem-cell-derived exosomes (hUCMSC-Exos) on bone regeneration, especially from the perspective of inducing angiogenesis. HUCMSC-Exos were isolated and characterized. In vitro, the effect of hUCMSC-Exos on the proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs) was examined. Moreover, the loading and release of hUCMSC-Exos on 3D-printed SF/COL-I/nHA scaffolds were evaluated. In vivo, hUCMSC-Exos and 3D-printed SF/COL-I/nHA scaffolds were implanted into alveolar bone defects, and bone regeneration and angiogenesis were investigated by micro-CT, HE staining, Masson staining, and immunohistochemical analysis. The results showed that hUCMSC-Exos stimulated HUVEC proliferation, migration, and tube formation in vitro, and the effect increased with increasing exosome concentrations. In vivo, the combination of hUCMSC-Exos and 3D-printed SF/COL-I/nHA scaffolds promoted alveolar bone defect repair by enhancing angiogenesis and osteogenesis. We constructed an elaborate cell-free bone-tissue-engineering system by combining hUCMSC-Exos with 3D-printed SF/COL-I/nHA scaffolds, potentially providing new ideas for treating alveolar bone defects.

Osteocytes, which are the most abundant cell type in bone, regulate osteoblasts and osteoclasts via both cell–cell interactions and paracrine signaling, and osteocyte-derived exosomes might contribute to this paracrine action. In this study, we investigated the effects of osteocyte-derived exosomes on regulating osteoblasts and osteoclasts and studied the potential mechanism. Materials and Methods: Osteocyte-derived exosomes were extracted and identified. PKH67-labeled exosomes were incubated with MC3T3-E1 cells and RAW264.7 cells, and fluorescence confocal microscopy was used to analyze the uptake of exosomes. ALP stain- ing and TRAP staining were used to analyze osteoblast activity and osteoclast formation. The level of miR-214-3p in exosomes was analyzed by qPCR and the incorporation of FAM-labeled miR-214-3p from exosomes into MC3T3-E1 cells was evaluated. The expressions of ephrinA2 and RANKL in exosomes were studied. Results: Our results demonstrated that osteocyte-derived exosomes might recognize osteoblasts through the ephrinA2 protein; thus, miR-214-3p in exosomes was transferred into osteoblasts to inhibit osteoblast activity. Meanwhile, we found that osteocyte-derived exosomes could be transferred into osteoclasts to induce osteoclast formation by releasing RANKL. Conclusion: These findings suggest that osteocyte-derived exosomes play an important role in the regulation of osteoblast and osteoclast activity, which might occur via miR-214-3p and RANKL.

The unique anatomical structure of the atrophic edentulous maxilla limits the placement of endosteal root form dental implants without bone grafting and augmentation. Surgical placement of zygomatic implants in an optimal position remains challenging. This technique report illustrates a novel digital guide technology, including the design workflow, application method, and indications for assisting with the placement of zygomatic implants using a bone‐supported titanium double‐sleeve guide. In addition, when the implant body reaches the zygomatic bone following an intra‐sinus path, including ZAGA type 0 and ZAGA type 1 cases, a matching window osteotomy surgical guide is used to locate the lateral window boundary and protect the sinus membrane. With this technique, the surgical procedure is simplified, and the precision of guided zygomatic implant placement is improved.