Cell-free fat extract-loaded microneedles attenuate inflammation-induced apoptosis and mitochondrial damage in tendinopathy.

Existing clinical treatments for tendinopathy mainly focus on reducing pain, whereas inhibiting or reversing disease progression remains challenging. Local therapeutic drugs, such as glucocorticoids, cause adverse effects on the metabolism of tendon tissues and injection-related complications. Therefore, new administration modalities for tendinopathy need to be developed. In this study, we designed a hydrogel-based microneedle (MN) system for the long-term transdermal delivery of our novel biological cell-free fat extract (CEFFE) to treat tendinopathies. We found that CEFFE-loaded MNs (CEFFE-MNs) had good biosafety and inhibited lipopolysaccharide (LPS)-induced apoptosis and matrix degradation in Achilles tendon cells of rats. The Achilles tendons of rats returned to their maximum mechanical strength after applying CEFFE-MNs. The administration of CEFFE-MNs had better anti-apoptosis and tendon repair-promoting effects than CEFEF injections in vivo. Transcriptome sequencing indicated that the anti-apoptosis effect of CEFFE-MNs was highly related to tumor necrosis factor (TNF) signaling. CEFFE-MNs inhibited the expression of TNF, TNF receptor 1, and downstream nuclear factor-kappa B signaling. Additionally, CEFFE-MNs rescued LPS-induced mitochondrial dynamics in tendon cells via the TNF-Drp1 axis. Our study reports a novel CEFFE-MN system that exhibits long-term anti-inflammatory and anti-apoptotic effects, suggesting it as a new treatment route for tendinopathy with broad clinical translation prospects.

3D-printed biodegradable magnesium alloy scaffolds with zoledronic acid-loaded ceramic composite coating promote osteoporotic bone defect repair.

Osteoporotic fracture is one of the most serious complications of osteoporosis. Most fracture sites have bone defects, and restoring the balance between local osteogenesis and bone destruction is difficult during the repair of osteoporotic bone defects. In this study, we successfully fabricated three-dimensional (3D)-printed biodegradable magnesium alloy (Mg-Nd-Zn-Zr) scaffolds and prepared a zoledronic acid-loaded ceramic composite coating on the surface of the scaffolds. The osteogenic effect of Mg and the osteoclast inhibition effect of zoledronic acid were combined to promote osteoporotic bone defect repair. In vitro degradation and drug release experiments showed that the coating significantly reduced the degradation rate of 3D-printed Mg alloy scaffolds and achieved a slow release of loaded drugs. The degradation products of drug-loaded coating scaffolds can promote osteogenic differentiation of bone marrow mesenchymal stem cells as well as inhibit the formation of osteoclasts and the bone resorption by regulating the expression of related genes. Compared with the uncoated scaffolds, the drug-coated scaffolds degraded at a slower rate, and more new bone grew into these scaffolds. The healing rate and quality of the osteoporotic bone defects significantly improved in the drug-coated scaffold group. This study provides a new method for theoretical research and clinical treatment using functional materials for repairing osteoporotic bone defects.

3D-printed vascularized biofunctional scaffold for bone regeneration.

3D-printed biofunctional scaffolds have promising applications in bone tissue regeneration. However, the development of bioinks with rapid internal vascularization capabilities and relatively sustained osteoinductive bioactivity is the primary technical challenge. In this work, we added rat platelet-rich plasma (PRP) to a methacrylated gelatin (GelMA)/methacrylated alginate (AlgMA) system, which was further modified by a nanoclay, laponite (Lap). We found that Lap was effective in retarding the release of multiple growth factors from the PRP-GelMA/AlgMA (PRP-GA) hydrogel and sustained the release for up to 2 weeks. Our in vitro studies showed that the PRP-GA@Lap hydrogel significantly promoted the proliferation, migration, and osteogenic differentiation of rat bone marrow mesenchymal stem cells, accelerated the formation of endothelial cell vascular patterns, and promoted macrophage M2 polarization. Furthermore, we printed hydrogel bioink with polycaprolactone (PCL) layer-by-layer to form active bone repair scaffolds and implanted them in subcutaneous and femoral condyle defects in rats. In vivo experiments showed that the PRP-GA@Lap/PCL scaffolds significantly promoted vascular inward growth and enhanced bone regeneration at the defect site. This work suggests that PRP-based 3D-bioprinted vascularized scaffolds will have great potential for clinical translation in the treatment of bone defects.

The first 3D-bioprinted personalized active bone to repair bone defects: A case report.

The repair and reconstruction of bone defects are still major problems to be solved in the field of orthopedics. Meanwhile, 3D-bioprinted active bone implants may provide a new and effective solution. In this case, we used bioink prepared from the patient's autologous platelet-rich plasma (PRP) combined with polycaprolactone/ß-tricalcium phosphate (PCL/ß-TCP) composite scaffold material to print personalized PCL/ß-TCP/PRP active scaffolds layer by layer through 3D bioprinting technology. The scaffold was then applied in the patient to repair and reconstruct bone defect after tibial tumor resection. Compared with traditional bone implant materials, 3D-bioprinted personalized active bone will have significant clinical application prospects due to its advantages of biological activity, osteoinductivity, and personalized design.

Mechanosensitive miR-99b mediates the regulatory effect of matrix stiffness on bone marrow mesenchymal stem cell fate both in vitro and in vivo.

Mechanical signals from extracellular matrix stiffness are important cues that regulate the proliferation and differentiation of bone marrow mesenchymal stem cells (BMSCs). However, the incorporation of BMSCs into soft hydrogels and the dominance of soft matrices for BMSC growth and differentiation limit the directed differentiation of BMSCs incorporated into hydrogels for tissue engineering, especially osteogenesis. Here, we found that the expression of miR-99b increased with increasing hydrogel stiffness and that miR-99b regulated the proliferation and differentiation of BMSCs seeded on the surface of substrates with different stiffnesses. Furthermore, miR-99b significantly promoted the migration of BMSCs in 3D hydrogels. Mechanistically, we demonstrated that matrix stiffness-sensitive miR-99b targets the mammalian target of the rapamycin signaling pathway to regulate the adipogenic and osteogenic differentiation of BMSCs. In addition, by modulating the expression of miR-99b, the osteogenic differentiation of BMSCs in soft 3D hydrogels was promoted. Consistently, the flexible BMSC-GelMA hydrogel transfected with miR-99b significantly promoted bone regeneration in the rat calvarial defect area. These results suggest that miR-99b plays a key role in the mechanotransduction and phenotypic transformation of BMSCs and may inspire new tissue engineering applications with MSCs as key components.

Niobium promotes fracture healing in rats by regulating the PI3K-Akt signalling pathway: An in vivo and in vitro study.

Background: Stable fixation is crucial in fracture treatment. Currently, optimal fracture fixation devices with osteoinductivity, mechanical compatibility, and corrosion resistance are urgently needed for clinical practice. Niobium (Nb), whose mechanical properties are similar to those of bone tissue, has excellent biocompatibility and corrosion resistance, so it has the potential to be the most appropriate fixation material for internal fracture treatment. However, not much attention has been paid to the use of Nb in the area of clinical implants. Yet its role and mechanism of promoting fracture healing remain unclear. Hence, this study aims at elucidating on the effectiveness of Nb by systematically evaluating its osteogenic performance via in vivo and ex vivo tests. Methods: Systematic in vivo and in vitro experiments were conducted to evaluate the osteogenic properties of Nb. In vitro experiments, the biocompatibility and osteopromoting activity of Nb were assessed. And the osteoinductive activity of Nb was assessed by alizarin red, ALP staining and PCR test. In vivo experiments, the effectiveness and biosafety of Nb in promoting fracture healing were evaluated using a rat femoral fracture model. Through the analysis of gene sequencing results of bone scab tissues, the upregulation of PI3K-Akt pathway expression was detected and it was verified by histochemical staining and WB experiments. Results: Experiments in this study had proved that Nb had excellent in-vitro cell adhesion and proliferation-promoting effects without cytotoxicity. In addition, ALP activity, alizarin red staining and semi-quantitative analysis in the Nb group had indicated its profound impact on enhancing osteogenic differentiation of MC3T3-E1 cells. We also found that the use of Nb implants can accelerate fracture healing compared to that with Ti6Al4V using an animal model of femur fracture in rats, and the biosafety of Nb was confirmed in vivo via histological evaluation. Furthermore, we found that the osteogenic effects of Nb were achieved through activation of the PIK/Akt3 signalling pathway. Conclusion: As is shown in the present research, Nb possessed excellent biosafety in clinical implants and accelerated fracture healing by activating the PI3K-Akt signalling pathway, which had good prospects for clinical translation, and it can replace titanium alloy as a material for new functional implants.