Intra-articular Gentamicin-loaded PLA Microparticle Injection for the Treatment of Septic Arthritis in Rabbits

A Fused Membrane-Camouflaged Biomimetic Nanosystem for Dual-Targeted Therapy of Septic Arthritis

Due to the inherent aseptic and enclosed characteristics of joint cavity, septic arthritis (SA) almost inevitably leads to intractable infections and rapidly progressing complex pathological environments. Presently, SA faces not only the deficient effectiveness of the gold-standard systemic antibiotic therapy but also the scarcity of effective localized targeted approaches and standardized animal models. Herein, an ingenious multifunctional nanosystem is designed, which involves the methylation of hyaluronic acid (HA), copolymerization with DEGDA, loading with vancomycin (VAN), and then coating with fused macrophage-platelet membrane (denoted as FM@HA@VAN). Upon intra-articular administration, FM@HA@VAN nanoparticles exhibit sustained retention and selectively targeting to infected sites, leveraging macrophage-mediated inflammation homing and platelet-directed bacteria targeting. The acidic microenvironment triggers responsive release of vancomycin, leading to potent bactericidal effects. Subsequently, the exposed HA@VAN nanoparticles are efficiently internalized by activated macrophages, releasing HA to alleviate oxidative stress and achieve chondroprotection by inhibiting pro-inflammatory cytokines, neutralizing ROS and upregulating macrophage M2 polarization. In vivo model and experiments confirm the efficacy of this dual-targeting antibacterial approach, demonstrating its precision in eradicating bacterial infections and alleviating associated pathological processes, including synovial hyperplasia and cartilage erosion. The dual-targeting therapeutic nanosystem, coordinated with fused-membranes, holds promise for enhancing the treatment efficacy of SA.

Biofilm Formation by Pseudomonas aeruginosa in a Novel Septic Arthritis Model

Background

Bacterial biofilms generally contribute to chronic infections and complicate effective treatment outcomes. To date, there have been no reports describing biofilm formation in animal models of septic arthritis caused by Pseudomonas aeruginosa (P. aeruginosa). P. aeruginosa is an opportunistic pathogenic bacterium which can lead to septic arthritis. The purpose of this study was to establish a rabbit model of septic arthritis caused by P. aeruginosa to determine whether it leads to biofilm formation in the knee joint cavity. In addition, we explored the role of cyclic di-GMP (c-di-GMP) concentrations in biofilm formation in rabbit models.

Methods

Twenty rabbits were randomly assigned to five groups: PAO1 (n = 4), PAO1ΔwspF (n = 4), PAO1/p_lac-yhjH (n = 4) infection group, Luria–Bertani (LB) broth (n = 4), and magnesium tetrasilicate (talc) (n = 4) control groups. Inoculation in the rabbit knee of P. aeruginosa or with the same volume of sterile LB or talc in suspension (control group) was used to induce septic arthritis in the animal model. In the infection groups, septic arthritis was caused by PAO1, PAO1ΔwspF, and PAO1/p_lac-yhjH strains, respectively. Rabbits were euthanized after 7 days, and pathological examination of synovial membrane was performed. The biofilms on the surface of the synovial membrane were observed by scanning electron microscopy, while the biofilms’ fiber deposition was discriminated using peptide nucleic acid-fluorescence in situ hybridization (PNA-FISH).

Results

A rabbit model for knee septic arthritis induced by P. aeruginosa was successfully established. Scanning electron microscopy revealed that PAO1 strains were surrounded in a self-produced extracellular matrix on the surface of synovial membrane and showed biofilm structures. The biofilms in the fibrous deposition were also observed by PNA-FISH. The PNA-FISH assay revealed that the red fluorescence size in the PAO1ΔwspF group was greater than in PAO1 and PAO1/p_lac-yhjH groups.

Conclusions

This is the first study to provide evidence that P. aeruginosa forms biofilms in a rabbit model for septic knee arthritis. The rabbit model can be used to investigate new approaches to treatment of biofilms in septic arthritis. Furthermore, c-di-GMP is a key signaling molecule which impacts on biofilm formation in rabbit models of knee septic arthritis.