Synoviocyte detachment: an overlooked yet crucial histological aspect in rheumatoid arthritis

Abstract

Objective: Rheumatoid arthritis (RA) is a prevalent autoimmune disorder that leads to chronic joint inflammation, deformity, disability, and systemic complications. This study aimed to analyze the clinical characteristics and synovial pathology of RA patients with synoviocyte detachment, and explore the factors associated with this phenomenon.

Methods: This was a retrospective cohort study included RA patients who underwent synovial biopsy at our center from April to September 2023. Demographic, clinical, laboratory, and synovial histological data were retrospectively collected from medical records at the time of joint synovial biopsy in patients. Microscopic examination of hematoxylin and eosin (HE)-stained synovial tissue sections categorized the samples into synoviocyte detachment and no-synoviocyte detachment groups. Clinical characteristics and synovial pathological changes were compared between the two groups, and the factors associated with synoviocyte detachment were explored through logistic regression analysis.

Results: Fifty-five RA patients were enrolled; 45 were females, and the mean age was 53.4 ± 11.8 years. Nine RA patients exhibited synoviocyte detachment. A total of 46 RA patients in the no-synoviocyte detachment group (15 with a normal lining layer and 31 with synovial cell proliferation) were included. Compared with the no-synoviocyte detachment group, the synoviocyte detachment group presented higher RF, ESR, CRP and DAS28-CRP levels (P < 0.05). The synoviocyte detachment group exhibited more prominent neovascularization (P < 0.05). ESR, DAS28-CRP and synovial neovascularization were risk factors associated with synoviocyte detachment in RA patients.

Conclusion: RA patients with synoviocyte detachment exhibit elevated clinical disease activity, marked by pronounced synovial pathology featuring increased neovascularization and less inflammatory cell infiltration. A significant reduction in lymphocyte count compared with patients with synovial cell proliferation was also observed.

Keywords: Rheumatoid arthritis; Synovial pathology; Synoviocyte Detachment.

Fig. 1

Various alterations in the synovial lining layer of RA patients were detected via hematoxylin and eosin (HE) staining. (A) synoviocyte detachment; (B) normal lining layer cell; (C) synovial cell proliferation

Fig. 2

Synovial pathology (A-F) and X-ray (G) of a 50-year-old Asian female diagnosed with RA. Her ESR was 71 mm/h and her CRP level was 36.71 mg/L. The disease activity score was 6.02 according to the DAS28-CRP, indicating a high degree of disease activity. Synovial biopsy pathological results revealed thinning or disappearance of the synovial lining layer (←); slight lymphocyte infiltration around blood vessels (*); and interstitial vascular hyperplasia, thickening of the vessel wall, dilation and congestion of blood vessels (#). Wrist and hand radiography revealed a blurred joint surface, periarticular bone osteoporosis and narrowing of the joint space

Fig. 3

RF (A), ESR (B), CRP (C), DAS28-CRP (D), CD3⁺ cell count (E), CD20⁺ cell count (F), CD68⁺ cell count (G) and CD138⁺ cell count (H) comparisons between the two groups. Hyperplasia, synovial cell proliferation group; detachment, synoviocyte detachment group. * P < 0.05