Tissue engineering has emerged as a promising approach for addressing bone defects. Most of the traditional 3D printing materials predominantly relying on polymers and ceramics. Although these materials exhibit superior osteogenic effects, their gradual degradation poses a limitation. Digital light processing (DLP) 3D bioprinting that uses natural biomaterials as bioinks has become one of the promising strategies for bone regeneration. In this study, we introduce a hydrogel biomaterial derived from silk fibroin (SF). Notably, we present the novel integration of nano-hydroxyapatite (nHA) into the hydrogel, forming a composite hydrogel that rapidly cross-links upon initiation. Moreover, we demonstrate the loading of nHA through non-covalent bonds in SilMA. In vitro experiments reveal that composite hydrogel scaffolds with 10 % nHA exhibit enhanced osteogenic effects. Transcriptomic analysis indicates that the composite hydrogel promotes bone regeneration by inducing M2 macrophage polarization. Furthermore, rat femoral defect experiments validate the efficacy of SilMA/nHA₁₀ in bone regeneration. This study synthesis of a simple and effective composite hydrogel bioink for bone regeneration, presenting a novel strategy for the future implementation of digital 3D printing technology in bone tissue engineering.

Local ischemia and hypoxia are the most important pathological processes in the early phase of secondary spinal cord injury (SCI), in which mitochondria are the main target of ischemic injury. Mitochondrial autophagy, also known as mitophagy, acts as a selective autophagy that specifically identifies and degrades damaged mitochondria, thereby reducing mitochondria-dependent apoptosis. Accumulating evidence shows that the mitophagy receptor, FUN14 domain-containing 1 (FUNDC1), plays an important role in ischemic injury, but the role of FUNDC1 in SCI has not been reported. In this study, we aimed to investigate whether FUNDC1 can enhance mitophagy and inhibit neuronal apoptosis in the early stage of SCI. In a rat SCI model, we found that FUNDC1 overexpression enhanced neuronal autophagy and decreased neuronal apoptosis in the early stage of injury, thereby reducing spinal cord damage. In vitro studies showed that the neuroprotective effects of FUNDC1 were achieved by inhibiting mitochondria-dependent apoptosis and improving mitochondrial function. In addition, FUNDC1 enhanced mitophagy. The protective effects of FUNDC1 against apoptosis and mitochondrial dysfunction were reversed by 3-methyladenine (3-MA), an autophagy inhibitor. Taken together, our results confirm that FUNDC1 can protect against neuronal loss after SCI by inducing mitophagy, inhibiting mitochondria-dependent apoptosis, and improving mitochondrial function.

Objective: Spinal cord injury (SCI) is a severe type of neurological trauma. N6-methyladenosine (m6A) modification is one of the most common internal modifications of RNA. The role of METTL3, the predominant methylation enzyme of m6A modification, in SCI remains unclear. This study aimed to investigate the role of methyltransferase METTL3 in SCI.Methods: After establishing the oxygen-glucose deprivation (OGD) model of PC12 cells and rat spinal cord hemisection model, we found that the expression of METTL3 and the overall m6A modification level were significantly increased in neurons. The m6A modification was identified on B-cell lymphoma 2 (Bcl-2) messenger RNA (mRNA) by bioinformatics analysis, and m6A-RNA immunoprecipitation and RNA immunoprecipitation. In addition, METTL3 was blocked by the specific inhibitor STM2457 and gene knockdown, and then apoptosis levels were measured.Results: In different models, we found that the expression of METTL3 and the overall m6A modification level were significantly increased in neurons. After inducing OGD, inhibition of METTL3 activity or expression increased the mRNA and protein levels of Bcl-2, inhibited neuronal apoptosis, and improved neuronal viability in the spinal cord.Conclusion: Inhibition of METTL3 activity or expression can inhibit the apoptosis of spinal cord neurons after SCI through the m6A/Bcl-2 signaling pathway.