A Novel Mechanical-Based Injective Hydrogel for Treatment with Aromatase Inhibitors Caused Joint Inflammation via the NF-κB Pathway

Abstract

Synovium has widely participated in induced inflammation, suggesting that it is a potential target to reduce aromatase inhibitors (AIs) causing joint inflammation or pain. Exercise and mechanical stimulation are important strategies for precaution and treatment of bone inflammation. In this work, we developed a novel thermo-sensitive hydrogel, which could be injected intra-articularly. The aim of this research was to investigate the role of various mechanical strength hydrogels in reducing synovium inflammation. The effect of different mechanical strength hydrogels on regulating synovium inflammation was used to stimulate human fibroblast-like synoviocytes (FLS) under a cyclic mechanical compression environment in vitro. Cytokine and metalloprotease expression in FLS was analyzed by the western blot and q-PCR method, in which FLS were cultured with the different mechanical strength hydrogels. The results showed that a moderate-intensity hydrogel mechanical stimulation might be suitable in reducing AI-induced FLS inflammation via the NK-κB pathway. In addition, we built an AI-treated rat model and injected the different mechanical strength hydrogels. Similarly, the moderate-strength mechanical hydrogel could reduce the inflammatory factor and metalloproteinase expression in synovial tissues and intra-articular synovia.

Figure 1

(A) Synthetic circuit diagram of gelatin-grafted Pluronic; (B) images of the hydrogel production process; (C) ¹H NMR spectra of Pluronic, gelatin, and GP; (D) phase diagram of Pluronic and GP; (E) oscillatory frequency sweep tests (at a strain of 0.05%) at 37 °C; and (F) SEM images of GP hydrogels of different stiffness values.

Figure 2

Synovial fibroblasts’ cell viability cultured with low-intensity, moderate-intensity, and high-intensity hydrogels at different times. (A) The cells were stained by vimentin immunofluorescence and DAPI. (B) The cell proliferation rate was measured by the MTT method.

Figure 3

Synovial fibroblasts’ cell viability cultured with low-intensity, moderate-intensity, and high-intensity hydrogels at 72 h at cyclic compression pressure. The cells apoptosis was analyzed by flow cytometry.

Figure 4

The effect of different mechanical intensities of the hydrogel on inflammatory agent mRNA expression in the FLS was demonstrated. The mRNA expression levels of bone markers IL-1β (A), IL-6 (B), TNF-α (C), and MMP-1 (D) at 24 h were detected by qPCR.

Figure 5

Western blotting showed protein levels of p-IKBα, IKBα, p-p65, p65, IL-6, and MMP-1 at 24 h (A). Statistical analysis of the relative protein expression of p-p65/p65 (B), IL-6 (C), and MMP-1 (D) at 24 h. All data are the average values from several independent experiments (n = 3). *P < 0.05, **P < 0.01 vs the control group.

Figure 6

Immunohistochemical image of IL-6 (A) and MMP-1 (C) expressions in synovial tissues after injection of different strength hydrogels at week 2. Quantitative analysis of IL-6 (B) and MMP-1 (D) expressions in intra-articular synovia after injection of different strength hydrogels at week 2. All experiments were conducted in triplicate. *P < 0.05, **P < 0.01 vs the control group. The scale bars are 200 (A) and 30 μm (C), respectively.