Fig 2: Regulation of Lrrc15 on the NF‐κB signaling pathway in FLS in vitro. (A and B) Primary rat FLSs transfected with siNC or siLrrc15 were treated with 10 ng/mL IL‐1β for 24 h. NF‐κB (p65)‐positive cells were measured by immunofluorescence assay (A). The protein levels of NF‐κB (p65), p‐NF‐κB (p‐p65), p‐IKBα, IKBα, and Nrf2 were measured by western blot (B). (C) A schematic diagram displaying the regulatory relationship between Lrrc15 and NF‐κB signaling pathway in FLS. Data were presented as Mean ± SD and analyzed using the one‐way ANOVA. N = 3. *p < 0.05; **p < 0.01.

Fig 3: Functional effects of Lrrc15 on pro‐inflammatory cytokine levels in CIA rats. Ad‐scramble or Ad‐shLrrc15 was injected into both joint cavities of CIA rats. CIA and control group of rats injected with same volume of vehicle. (A) The mRNA changes of Ifng, Il6, Il1b, and Il10 in synovial tissues of rats were examined using RT‐qPCR. (B) The levels of IFN‐γ, IL‐6, IL‐1β, and IL‐10 in synovial fluid of rats were assessed using ELISA. Data were presented as Mean ± SD and analyzed using the one‐way ANOVA. N = 6. *p < 0.05; **p < 0.01.

Fig 4: Effects of Lrrc15 on IL‐1β‐induced FLS activation in vitro. (A–E) Primary rat FLSs transfected with siNC or siLrrc15 were treated with 10 ng/mL IL‐1β for 24 h. LRRC15 expression was measured by RT‐qPCR (A) and western blot (B). The proliferation of FLSs was detected by CCK‐8 (C) and EdU staining (D). The migration of FLSs was assessed by Transwell assay (E). Data were presented as Mean ± SD and analyzed using the one‐way or two‐way ANOVA. N = 3. *p < 0.05; **p < 0.01.

Fig 5: Expression of LRRC15 in the synovial tissues of CIA rats. (A) Cell atlas of RA tissues. (B) Cell markers for marking different cell types in cell clusters. (C) The UMAP plot of fibroblasts in RA tissues. (D and E) The expression of Lrrc15 in the fibroblasts of control and RA tissues. (F and G) Wistar rats were injected with bovine Collagen II emulsified in complete Freund's adjuvant for the establishment of CIA animal models. The expression of LRRC15 in the synovial tissues of control and CIA rats was detected by RT‐qPCR (F) and immunohistochemistry (G). Data were presented as mean ± SD and analyzed using the unpaired t‐test. N = 6. **p < 0.01.