Mineralized nanofibrous scaffold promotes phenamil-induced osteoblastic differentiation while mitigating adipogenic differentiation

Anti-aging Metabolite-Based Polymeric Microparticles for Intracellular Drug Delivery and Bone Regeneration

Alpha-ketoglutarate (AKG), a key component of the tricarboxylic acid (TCA) cycle, has attracted attention for its anti-aging properties. Our recent study indicates that locally delivered cell-permeable AKG significantly promotes osteogenic differentiation and mouse bone regeneration. However, the cytotoxicity and rapid hydrolysis of the metabolite limit its application. In this study, we synthesize novel AKG-based polymeric microparticles (PAKG MPs) for sustained release. In vitro data suggest that the chemical components, hydrophilicity, and size of the MPs can significantly affect their cytotoxicity and pro-osteogenic activity. Excitingly, these biodegradable PAKG MPs are highly phagocytosable for nonphagocytic pre-osteoblasts MC3T3-E1 and primary bone marrow mesenchymal stem cells (BMSCs), significantly promoting their osteoblastic differentiation. RNAseq data suggest that PAKG MPs strongly activate Wnt/β-catenin and PI3K-Akt pathways for osteogenic differentiation. Moreover, PAKG enables poly (L-lactic acid) and poly (lactic-co-glycolic acid) MPs (PLLA & PLGA MPs) for efficient phagocytosis. Our data indicate that PLGA-PAKG MPs-mediated intracellular drug delivery can significantly promote stronger osteoblastic differentiation compared to PLGA MPs-delivered phenamil. Notably, PAKG MPs significantly improve large bone regeneration in a mouse cranial bone defect model. Thus, the novel PAKG-based MPs show great promise to improve osteogenic differentiation, bone regeneration, and enable efficient intracellular drug delivery for broad regenerative medicine.

Biomineralized tetramethylpyrazine-loaded PCL/gelatin nanofibrous membrane promotes vascularization and bone regeneration of rat cranium defects

Conventional electrospinning produces nanofibers with smooth surfaces that limit biomineralization ability. To overcome this disadvantage, we fabricated a tetramethylpyrazine (TMP)-loaded matrix-mimicking biomineralization in PCL/Gelatin composite electrospun membranes with bubble-shaped nanofibrous structures. PCL/Gelatin membranes (PG), PCL/Gelatin membranes containing biomineralized hydroxyapatite (HA) (PGH), and PCL/Gelatin membranes containing biomineralized HA and loaded TMP (PGHT) were tested. In vitro results indicated that the bubble-shaped nanofibrous surface increased the surface roughness of the nanofibers and promoted mineralization. Furthermore, sustained-release TMP had an excellent drug release efficiency. Initially released vigorously, it reached stabilization at day 7, and the slow-release rate stabilized at 61.0 ± 1.8% at 28 days. All membranes revealed an intact cytoskeleton, cell viability, and superior adhesion and proliferation when stained with Ghost Pen Cyclic Peptide, CCK-8, cell adhesion, and EdU. In PGHT membranes, the osteogenic and vascularized gene expression of BMSCs and human vascular endothelial cells was significantly upregulated compared with that in other groups, indicating the PGHT membranes exhibited an effective vascularization role. Subsequently, the membranes were implanted in a rat cranium defect model for 4 and 8 weeks. Micro-CT and histological analysis results showed that the PGHT membranes had better bone regenerative patterns. Additionally, the levels of CD31 and VEGF significantly increased in the PGHT membrane compared with those in other membranes. Thus, PGHT membranes could accelerate the repair of cranium defects in vivo via HA and TMP synergistic effects.

Dual drug delivery system of teicoplanin and phenamil based on pH-sensitive silk fibroin/sodium alginate hydrogel scaffold for treating chronic bone infection

For effective treatment of infected bone, it is essential to use local drug delivery systems with the ability to deliver both antibiotics and osteoinductive factors. Herein, a pH-sensitive silk fibroin (SF)/sodium alginate (SA) hydrogel scaffolds containing teicoplanin (TEC) and phenamil (PM) loaded SF nanoparticles (PMSFNPS) are introduced for treating chronic osteomyelitis. The TEC and PM showed a sustained- and pH-sensitive release behavior from SF/SA hydrogel. The higher release rate was seen in an alkaline pH in comparison to neutral and acidic pH during 10 days. The eluted TEC maintained its antibacterial activity of >75 % during 35 days and in three different pH values (5.5, 7.4, and 8.5). The cellular study indicated that the scaffolds containing PMSFNPs could promote the cell viability, ALP activity, and matrix mineralization. Moreover, the in vivo effectiveness of hydrogel scaffolds were analyzed with radiography, histological and Immunohistochemistry evaluations. The lower infection and higher regeneration were observed in methicillin-resistant Staphylococcus aureus (MRSA) infected rat bone treated with hydrogel scaffold containing PMSFNPs and TEC compared to other groups. Consequently, this dual-drug delivery system could be a hopeful approach for effective treatment of chronic bone infection.

MicroRNA function in craniofacial bone formation, regeneration and repair

Bone formation in the craniofacial complex is regulated by cranial neural crest (CNC) and mesoderm-derived cells. Different elements of the developing skull, face, mandible, maxilla (jaws) and nasal bones are regulated by an array of transcription factors, signaling molecules and microRNAs (miRs). miRs are molecular modulators of these factors and act to restrict their expression in a temporal-spatial mechanism. miRs control the different genetic pathways that form the craniofacial complex. By understanding how miRs function in vivo during development they can be adapted to regenerate and repair craniofacial genetic anomalies as well as bone diseases and defects due to traumatic injuries. This review will highlight some of the new miR technologies and functions that form new bone or inhibit bone regeneration.

Nanoclay Promotes Mouse Cranial Bone Regeneration Mainly through Modulating Drug Binding and Sustained Release

Nanoclay (Nanosilicates, NS) is appearing as an intriguing 2D nanomaterial for bone tissue engineering with multiple proposed functions, e.g., intrinsic osteoinductivity, improving mechanical properties, and drug release capacity. However, the mechanism of NS for in vivo bone regeneration has been hardly defined so far. This knowledge gap will significantly affect the design/application of NS-based biomaterials. To determine the role of NS in osteoblastic differentiation and bone formation, we used the mouse calvarial-derived pre-osteoblasts (MC3T3-E1) and a clinically-relevant mouse cranial bone defect model. Instead of a hydrogel, we prepared biomimetic 3D gelatin nanofibrous scaffolds (GF) and NS-blended composite scaffolds (GF/NS) to determine the essential role of NS in critical low-dose (0.5 μg per scaffold) of BMP2-induced cranial bone regeneration. In contrast to "osteoinductivity", our data indicated that NS could enable single-dose of BMP2, promoting significant osteoblastic differentiation while multiple-dose of BMP2 (without NS) was required to achieve similar efficacy. Moreover, our release study revealed that direct binding to NS in GF scaffolds provided stronger protection to BMP2 and sustained release compared to GF/NS composite scaffolds. Consistently, our in vivo data indicated that only BMP2/NS direct binding treatment was able to repair the large mouse cranial bone defects after 6 weeks of transplantation while neither BMP2, NS alone, nor BMP2 released from GF/NS scaffolds was sufficient to induce significant cranial bone defect repair. Therefore, we concluded that direct nanoclay-drug binding enabled sustained release is the most critical contribution to the significantly improved bone regeneration compared to other possible mechanisms based on our study.

Biomimetic Nanofibrous 3D Materials for Craniofacial Bone Tissue Engineering

Repair of large bone defects using biomaterials-based strategies has been a significant challenge due to the complex characteristics required for tissue regeneration, especially in the craniofacial region. Tissue engineering strategies aimed at restoration of function face challenges in material selection, synthesis technique, and choice of bioactive factor release in combination with all aforementioned facets. Biomimetic nanofibrous (NF) scaffolds are attractive vehicles for tissue engineering due to their ability to promote endogenous bone regeneration by mimicking the shape and chemistry of natural bone extracellular matrix (ECM). To date, several techniques for generation of biomimetic NF scaffolds have been discovered, each possessing several advantages and drawbacks. This spotlight highlights two of the more popular techniques for biomimetic NF scaffold synthesis: electrospinning and thermally-induced phase separation (TIPS), covering development from inception in each technique as well as discussing the most recent innovations in each fabrication method.