IL-13Rα2 Glycosylation Holds the Dance Card for Partnering with IL-13

Therapeutic potential of CHI3L1 in osteoarthritis: Inhibition of cartilage matrix degradation and inflammation through TLR4-MAPK-STAT1 pathway

AIMS

CHI3L1 has been identified as a protein expressed in various tissues and tumor tissues, playing critical roles in diverse physiological and pathological processes such as inflammation, oxidative stress, cell death, and immune regulation. Previous studies have indicated that the elevated CHI3L1 levels in synovial fluid and serum of osteoarthritis patients may serve as a biomarker for osteoarthritis. However, the mechanisms by which CHI3L1 affects chondrocytes and the significance of its upregulated expression remain to be fully elucidated. This study aims to investigate the effects of CHI3L1 on chondrocytes and elucidate its molecular mechanisms.

METHODS

Interleukin-1 beta (IL-1β) was utilized in vitro to induce an inflammatory injury model in chondrocytes. The destabilization of the medial meniscus (DMM) surgery was employed to establish a mouse model of osteoarthritis in vivo. Experimental techniques, including Western blot, RT-qPCR, immunofluorescence, transcriptome sequencing, and co-immunoprecipitation, were applied to investigate the effects and mechanisms of CHI3L1 on chondrocytes. Microcomputed tomography (micro-CT), X-ray imaging, and IHC were used to evaluate the impact of CHI3L1 on knee joint osteoarthritis in mice.

RESULTS

In vitro experiments demonstrated that CHI3L1 enhanced matrix synthesis markers, suppressed matrix degradation indicators, and reduced inflammatory factors levels in chondrocytes. In vivo studies showed that intra-articular overexpression of CHI3L1 via rAAV-Chi3l1 alleviated cartilage degeneration and synovial inflammation in a murine osteoarthritis model. Mechanistically, integrated transcriptomic profiling and functional assays revealed that CHI3L1 interacts with TLR4 to attenuate MAPK phosphorylation, thereby inhibiting STAT1 phosphorylation and nuclear translocation.

CONCLUSION

The expression of CHI3L1 is upregulated in osteoarthritis. CHI3L1 alleviates osteoarthritis inflammation and cartilage matrix degradation through the TLR4-MAPK-STAT1 pathway, thereby inhibiting the progression of osteoarthritis. These findings indicate that CHI3L1 is a cytokine with protective effects in osteoarthritis and may represent a promising therapeutic target for alleviating osteoarthritis.

ARTICLE FOCUS

The objective of this study is to investigate the effects of CHI3L1 on chondrocytes and to further elucidate the underlying mechanisms by which CHI3L1 exerts its influence on chondrocytes.

KEY MESSAGES

In this study, it is proposed that CHI3L1 maintains the homeostasis of the cartilage matrix and alleviates inflammation by inhibiting the activation of the TLR4-MAPK-STAT1 signaling pathway.

STRENGTHS AND LIMITATIONS

We have established the protective role of CHI3L1 in maintaining cartilage matrix homeostasis, identified potential receptors and pathways associated with CHI3L1, and elucidated its mechanisms of action. The role of CHI3L1 in osteoarthritic synovial tissue has not yet been investigated. Further research is needed to elucidate the effects of CHI3L1 secreted by synovial tissue on chondrocytes.

Increased Muc5AC and Decreased Ciliated Cells in Severe Asthma Partially Restored by Inhibition of IL-4Rα Receptor

Rationale: The role of IL-13 on the airway epithelium in severe asthma leading to airway remodeling remains poorly understood. Objectives: To study IL-13-induced airway remodeling on goblet cells and cilia in the airway epithelium in severe asthma and the impact of an anti-IL4Rα antibody, dupilumab, in vitro. Methods: Quantitative computed tomography of the lungs and endobronchial biopsies and brushings were obtained in 51 participants (22 with severe asthma, 11 with nonsevere asthma, and 18 healthy participants) in SARPIII (Severe Asthma Research Program III) and measured for mucin and cilia-related proteins. Epithelial cells were differentiated at air-liquid interface (ALI) with IL-13 with or without dupilumab and assessed for mucin, cilia, cilia beat frequency (CBF), and epithelial integrity (transepithelial electrical resistance [TEER]). Measurements and Main Results: Increased Muc5AC (mucin 5AC) (Δ + 263.2 ± 92.7 luminosity/epithelial area) and decreased ciliated cells (Δ - 0.07 ± 0.03 Foxj1+ cells/epithelial area) were observed in biopsies from patients with severe asthma when compared with healthy control subjects (P < 0.01 and P = 0.047, respectively). RNA sequencing of endobronchial cell brushings confirmed a Muc5AC increase with a decrease in a five-gene cilia-related mean in patients with severe asthma compared with healthy subjects (all P < 0.05). IL-13 (5 ng/ml)-differentiated ALI cultures of healthy and asthmatic samples (from participants with severe and nonsevere asthma) increased Muc5AC, decreased cilia (α-aceytl-tubulin) in samples from healthy participants (Δ + 6.5% ± 1.5%, Δ - 14.1% ± 2.7%; all P < 0.001 respectively) and participants with asthma (Δ + 4.4% ± 2.5%, Δ - 13.1% ± 2.7%; P = 0.084, P < 0.001 respectively), and decreased epithelial integrity (TEER) in samples from healthy participants (-140.9 ± 21.3 [ohms], P < 0.001), while decreasing CBF in samples from participants with asthma (Δ - 4.4 ± 1.7 [Hz], P < 0.01). When dupilumab was added to ALI with IL-13, there was no significant decrease in Mu5AC, but there was restoration of cilia in healthy participants and participants with asthma (absolute increase of 67.5% and 32.5% cilia, all P < 0.05, respectively), whereas CBF increased (Δ + 3.6 ± 1.1 [Hz], P < 0.001) and TEER decreased (only in asthma, Δ - 37.8 ± 16.2 [ohms], P < 0.05). Conclusions: IL-13 drives features of airway remodeling in severe asthma, which are partially reversed by inhibiting the IL-4Rα receptor in vitro.