Youzhuan Xie

Bone microtissue grafts mimicking skeletal features and organogenesis are an emerging strategy, different from the traditional tissue engineered bone grafts using the three-dimensional (3D) cell encapsulation and the top cell seeding, and remain challenging in regenerative medicine and drug discovery, because the existing scaffold-free and microcarrier-based microtissue systems are difficult to manipulate the microtissue morphologies towards native bone microstructures limited by their mechanical weakness and the absence of interconnected inner cavities. Herein, we synthesized a supramolecular cryogel by an ice-templated freezing-polymerization process, acquiring a promising microcarrier resembling native bone trabecular morphology for 3D culture of trabecular bone microtissue grafts. In our strategy, a macromolecular chitosan monomer and two supramolecular monomers including glycinamide and phytic acid constituted the supramolecular cryogel, the modification using glycinamide and phytic acid components enables the cryogel microcarrier with porous cavities and compression-resistant abilities like the native trabecular bone tissues. Moreover, the mineralization of the cryogel microcarriers was also improved by the modification of phytic acid monomers, consequently strengthening osteogenic differentiation of bone-marrow-derived mesenchymal stem cells and in vitro microtissue biomineralization. The in vivo results also revealed that a trabeculae-like bone microtissue forms on the cryogel microcarriers, with vessel invasion into inner cavities of the trabecular bone microtissues. After in situ implantation of the prepared trabecular bone microtissues, the bone regeneration characterized by raising bone mineral density and remodeling bone trabecular microstructures was observed on a rat femur condyle defect model. Last but not least, we also discovered the intestinal bacterial communities and compositions are closely related to the bone regeneration after implantation of the engineered bone microtissue grafts, which is the first evidence focusing on the intestinal microbiota response to the bone injury and bone regeneration events representing a feasible approach to bone regeneration examination. In brief, the supramolecular cryogels we developed in this study have been proved to be a promising microcarrier for the construction and 3D culture of trabecular bone microtissues, and this work offers a novelty insight into microtissue engineering and bone regeneration.

Surgical site infections (SSIs) represent a global healthcare burden, a challenge intensified by the increasing prevalence of antibiotic resistance. To address drug-resistant bacterial infections, various non-antibiotic therapeutic strategies have been explored, among which sonodynamic therapy (SDT) has emerged as a promising approach due to its deep tissue penetration and controllability. Nevertheless, bacteria are not defenseless against SDT and can produce endogenous hydrogen sulfide (H₂S) as an antioxidant to resist reactive oxygen species (ROS)-mediated killing, thereby limiting therapeutic efficacy. Herein, we reported a dual-functional and synergistic sonodynamic antibacterial strategy based on two-dimensional bismuth porphyrin metal-organic frameworks (Bi-TCPP). Bi-TCPP simultaneously functioned as an efficient sonosensitizer to generate singlet oxygen (¹O₂) under ultrasound irradiation and as an effective scavenger of bacterial-derived H₂S through strong Bi³⁺-H₂S interactions. By weakening the bacterial antioxidant reduction system and disrupting redox homeostasis, this strategy enabled efficient bacterial eradication via low-level ROS, thereby significantly amplifying SDT-mediated antibacterial efficacy. The effectiveness of this synergistic strategy was systematically demonstrated against multiple bacterial species, including drug-resistant strains and different survival states such as planktonic bacteria and biofilms in vitro. It was further validated in vivo, highlighting its potential as an alternative therapeutic approach for treating drug-resistant bacterial infections.

Background: Intervertebral disc degeneration (IVDD) is a major cause of chronic back pain. Recent studies suggest that ferroptosis, a form of cell death, contributes to the degeneration of nucleus pulposus cells (NPCs). This study explores a novel therapeutic strategy using cell-free fat extract (CEFFE), rich in cytokines, to mitigate IVDD by inhibiting oxidative stress-induced ferroptosis. Methods: In vitro, NPC degeneration was induced by TNF-α/TBHP. The effects of CEFFE on matrix metabolism were evaluated using Western blotting, RT-qPCR, and high-density culture, with regenerative effects measured via CCK-8 assays. Ferroptosis was assessed by Western blotting, immunofluorescence, and electron microscopy. In vivo, rats with caudal IVDD were treated with CEFFE for 4 weeks, and therapeutic efficacy was evaluated through imaging and histological analysis. Results: In vitro, CEFFE reduced TNF-α-induced inflammation and promoted matrix synthesis by inhibiting MAPK and NF-κB pathways. It also activated NRF2 to prevent TBHP-induced ferroptosis. In rats, CEFFE facilitated nucleus pulposus repair and significantly slowed disc degeneration. Conclusions: CEFFE is a promising strategy to delay IVDD progression by inhibiting ferroptosis, offering potential therapeutic benefits for disc degeneration.

As an innovative regenerative medicine technology, bone organoids represent a promising therapy for refractory bone injury repair, whereas the key to fabricating bone organoids is grounded in the utilization of biomaterials with osteogenesis cues. Considering the intricate crosstalk between neurons and osteocytes would support bone organoid development and bone wound healing, it is extremely essential to predicate biomaterial design and osteo-organoid construction on understanding the roles of neural growth in ossification center formation and bone-like tissue development. Therefore, this review presents the recent advances of bone organoids with innervated ossification centers after the detailed introduction in the nerve–bone crosstalk. Beginning with the exploration of underlying interaction mechanisms within the osteogenic microenvironment, the importance of the nerve–bone crosstalk on skeleton development and bone regeneration is emphasized at first. The following discussions mainly include diverse biomaterial strategies designed to enhance osteogenesis through early innervation, such as the incorporation of bioactive minerals, controlled release of neurotrophic factors, and exosome-mediated nerve regeneration. Last but not least, the review highlights the advanced technologies in fabricating tissue-engineered bone organoids, with a focus on the applications of cell-laden and multicellular 3D-bioprinted bone microtissues for constructing bone organoids with neurovascularization. These insights are critical to the development of novel biomaterials to construct innervated osteo-organoids, with significant implications for future clinical applications, while also exploring the potential to advance bone regenerative therapies through enhanced nerve–bone crosstalk and laying the foundation for innovative translational research in this field.

The transpedicular procedure has been widely used in spinal surgery. The determination of the best entry point is the key to perform a successful transpedicular procedure. Various techniques have been used to determine this point, but the results are variable. This study was carried out to determine the posterior endpoint of the lumbar pedicle central axis on the standard anterior–posterior (AP) fluoroscopic images. Computer-aided design technology was used to determine the pedicle central axis and the posterior endpoint of the pedicle central axis on the posterior aspect of the vertebra. The standard AP fluoroscopic image of the lumbar vertebral models by three-dimensional printing was achieved. The endpoint projection on the AP fluoroscopic image was determined in reference to the pedicle cortex projection by the measurements of the angle and distance on the established X–Y coordinate system of the radiologic image. The projection of posterior endpoint of the lumbar pedicle central axis were found to be superior to the X-axis of the established X–Y coordinate system and was located on the pedicle cortex projection on the standard AP fluoroscopic image of the vertebra. The projection point was distributed in different sectors in the coordinate system. It was located superior to the X-axis by 18° to 26° at L1, while they were located superior to the X-axis by 12° to 14° at L2 to L5. The projections of posterior endpoints of the lumbar pedicle central axis were located in different positions on the standard AP fluoroscopic image of the vertebra. The determination method of the projection point was helpful for selecting an entry point for a transpedicular procedure with a fluoroscopic technique.