Purpose Methacrylic anhydride-modified gelatin (GelMA) hydrogels exhibit many beneficial biological features and are widely studied for bone tissue regeneration. However, deficiencies in the mechanical strength, osteogenic factors and mineral ions limit their application in bone defect regeneration. Incorporation of inorganic fillers into GelMA to improve its mechanical properties and bone regenerative ability has been one of the research hotspots. Methods In this work, hydroxyapatite nanofibers (HANFs) were prepared and mineralized in a simulated body fluid to make their components and structure more similar to those of natural bone apatite, and then different amounts of mineralized HANFs (m-HANFs) were incorporated into the GelMA hydrogel to form m-HANFs/GelMA composite hydrogels. The physicochemical properties, biocompatibility and bone regenerative ability of m-HANFs/GelMA were determined in vitro and in vivo. Results The results indicated that m-HANFs with high aspect ratio presented rough and porous surfaces coated with bone-like apatite crystals. The incorporation of biomimetic m-HANFs improved the biocompatibility, mechanical, swelling, degradation and bone regenerative performances of GelMA. However, the improvement in the performance of the composite hydrogel did not continuously increase as the amount of added m-HANFs increased, and the 15m-HANFs/GelMA group exhibited the best swelling and degradation performances and the best bone repair effect in vivo among all the groups. Conclusion The biomimetic m-HANFs/GelMA composite hydrogel can provide a novel option for bone tissue engineering in the future; however, it needs further investigations to optimize the proportions of m-HANFs and GelMA for improving the bone repair effect.

Background and Objectives Periodontitis, the most common chronic inflammation characterized by persistent alveolar bone resorption in the periodontitis, affects almost half of the adult population worldwide. Oxidative stress is one of the pathophysiological mechanisms underlying periodontitis, which affects the occurrence and development of periodontitis. Exosomes are increasingly recognized as vehicles of intercellular communication and are closely related to periodontitis. However, the effects of oxidative stress on exosome secretion and the specific mechanisms remain elusive in human periodontal ligament cells (hPDLCs). The relationship between exosome secretion and the osteogenic differentiation of hPDLCs also needs to be investigated. Methods Isolated PDLSCs were identified using flow cytometry. Osteogenesis was measured using alizarin red staining and ALP staining. Expression of exosomal markers and PRMT1 was analyzed using western blot. Immunofluorescence was used to measure exosome uptake and the expression of EEA1. Results The secretion capacity of exosomes was markedly suppressed under oxidative stress. Protein arginine methyltransferase 1 (PRMT1) has been strongly associated with both oxidative stress and inflammation, and PRMT1 was significantly upregulated under oxidative stress conditions. Lentivirus‐mediated overexpression of PRMT1 caused a significant reduction in the secretion of exosomes, but multivesicular bodies (MVBs) containing a large number of intraluminal vesicles (ILVs) were increased. Rab11a and Rab27a expression, which mediate MVBs fusion with cell membranes, decreased, although this phenomenon was restored after knocking down PRMT1 expression under oxidative stress. Conclusions These results indicated that PRMT1 mediated a decrease in exosome secretion of hPDLCs. The decrease in Rab11a and Rab27a leads to a large accumulation of MVBs in cells and is one of the main reasons for impaired exosome secretion. The decrease in osteogenic differentiation of hPDLCs caused by H2O2 may originate in part from the inhibition of exosome secretion.

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