Sustained and controllable local gene therapy is a potential method for treating osteoarthritis (OA) through the delivery of therapeutic microRNAs (miRNAs) to targeted cells. However, direct injection of crude miRNAs for local gene therapy is limited due to its inadequate transfection efficiency, easy inactivation, and short half-life. Here, a multifunctional gene vector, arginine, histidine, and phenylalanine-modified generation 5 polyamidoamine (named G5-AHP), was employed to form G5-AHP/miR-140 nanoparticles by forming a complex with microRNA-140 (miR-140). Then, the nanoparticles were entrapped in hydrogel microspheres (MSs) to construct a “nano-micron” combined gene hydrogel to alleviate the degradation of articular cartilage. Monodisperse gelatin methacryloyl hydrogel MSs were produced under ultraviolet light using one-step innovative microfluidic technology. Evenly dispersed MSs showed better injectability in sustainable and matrix metalloproteinases (MMPs)-responsive degradation methods for local gene delivery. The G5-AHP/miR-140 nanoparticles released from the MSs exhibited high gene transfection efficacy and long-term bioactivity, facilitated endocytosis, and thus maintained the metabolic balance of cartilage matrix by promoting the expression of type II collagen and inhibiting the expression of a disintegrin and metalloproteinase with thrombospondin motifs-5 and MMP13 in chondrocytes. After injection of the “nano-micron” combined gene hydrogel into the articular cavity of the OA model, the gene hydrogel increased G5-AHP/miR-140 nanoparticle retention, prevented articular cartilage degeneration, and reduced osteophyte formation in a surgically induced mouse model of OA. The present study provides a novel cell-free approach to alleviate the progression of OA that shows potential for locally injected gene delivery systems.

Osteoarthritis (OA) is the most common degenerative joint disease in the world. Gene therapy based on delivering microRNAs (miRNAs) into cells has potential for the treatment of OA. However, the effects of miRNAs are limited by the poor cellular uptake and stability. Here, we first identify a type of microRNA-224-5p (miR-224-5p) from clinical samples of patients with OA that can protect articular cartilage from degeneration and further synthesize urchin-like ceria nanoparticles (NPs) that can load miR-224-5p for enhanced gene therapy of OA. Compared with traditional sphere ceria NPs, the thorns of urchin-like ceria NPs can efficiently promote the transfection of miR-224-5p. In addition, urchin-like ceria NPs have excellent performance of scavenging reactive oxygen species (ROS), which can regulate the microenvironment of OA to further improve the gene treatment of OA. The combination of urchin-like ceria NPs and miR-224-5p not only exhibits favorable curative effect for OA but also provides a promising paradigm for translational medicine.

Tumor necrosis factor-alpha (TNF-α) promotes osteoclasts differentiation to enhance bone resorption and inhibits osteoblasts differentiation to impair bone formation, which plays a central role in the development of postmenopausal osteoporosis (PMOP). Recent studies implicated an important role of circular RNAs (circRNAs) in osteoporosis. The purpose of this study is to investigate whether circRNAs might be implicated in TNF-α-regulated osteoclasts differentiation and osteoblasts differentiation in PMOP. QRT-PCR was applied to detect expression of circRNA-circHmbox1 and miR-1247-5p in TNF-α-induced osteoclasts differentiation. Western blot, TRAP staining, alkaline phosphatase staining, alizarin red S staining, transwell and cell transfection were conducted to confirm that TNF-α inhibited osteoblasts differentiation by exosomal with low circHmbox1 expression from osteoclasts. Bioinformatics analysis and luciferase reporter revealed the mechanisms of the circHmbox1/miR-1247-5p/B cell lymphoma 6 (Bcl6) interaction. In this study, we found that the level of circRNA-circHmbox1 was obviously reduced in TNF-α-induced osteoclast formation in vivo and in vitro. CircHmbox1 could inhibit RANKL-induced osteoclasts differentiation primarily through binding to microRNA-1247-5p. TNF-α decreased osteoblasts differentiation by exosomal with low circHmbox1 expression from osteoclasts. Mechanistic studies showed that microRNA-1247-5p regulated osteoclasts differentiation and osteoblasts differentiation by targeting Bcl6, which was confirmed to play opposite roles in osteoblasts differentiation and osteoclasts differentiation. Our results provide evidence that circHmbox1-targeting miR-1247-5p is involved in the regulation of bone metabolisms by TNF-α in PMOP.