Table 1 ∣.
Clinical relevance of cell types associated with synovitis in OA
| Cell type | Markers | Clinical relevance | Refs |
|---|---|---|---|
| Macrophages | Folate receptor detected by 99mTc-EC20 SPECT–CT | The quantity of activated macrophages correlated with radiographic OA severity and pain and stiffness | 71 |
| CD14+CD16+ macrophages in synovial fluid express mature macrophage marker 25F9 (indicating activation) | CD14+ macrophages/total macrophages ratio in synovial fluid is a predictor of KOOS and WOMAC scores, regardless of CD16 expression | 63 | |
| CD14 and CD163 in synovial fluid significantly associated with activated macrophages (detected by 99mTc-EC20 SPECT–CT), in the capsule (P = 0.002 and P = 0.005, respectively) and in the synovium (P = 0.0005 and P = 0.002, respectively) | CD14 and CD163 presence in the synovial fluid is associated with osteophyte severity Synovial fluid CD14 and serum CD163 associated with severity of joint space narrowing Severity of self-reported knee joint symptoms associated with both synovial fluid (β = 0.773; P = 0.003) and serum (β = 0.641; P = 0.031) CD14 levels |
71 | |
| CD11c+/CD206+ or CD86+/CD163+ ratio in synovial fluid | Associated with KL grading and severity of knee OA in patients | 72 | |
| Mannose receptors MRC1 and MRC2 | MRC1 and MRC2 recognize collagen, promoting its internalization and lysosomal degradation Resulting improvement in collagen turnover restores ECM homeostasis in the joint and ameliorates cartilage destruction Type II collagen helps to maintain expression of anti-inflammatory macrophage-related genes and pro-chondrogenic cytokines |
77 | |
| SEPP1, FLOR2, STAB1, TXNIP and CD169 | Gene expression profile is indicative of enhanced phagocytic activity and immunosuppressive activity, suggesting an immunoregulatory role | 58 | |
| CCR2+ macrophages | Present in human synovium Invasive cells that are associated with cartilage erosion in OA |
65 | |
| CCL3, CCL4, IL1B and TNF | Pro-inflammatory macrophages | 58 | |
| FLS | CD34−THY1+ FLS | Less abundant in OA synovium than in RA synovium (8% versus 22% of cells, respectively) Perivascular location, proliferative and secrete pro-inflammatory cytokines Proportion of these FLS is correlated with synovitis and synovial hypertrophy assessed by ultrasonography |
90 |
| CD34−THY− FLS | Located in synovial lining Express the osteoblastic bone formation promoter BMP6 (involved in osteophyte formation) More abundant in OA than in RA synovium |
90 | |
| CADM1, COL8A2 and DKK3 | Located in synovial lining DKK3 is a strong inhibitor of cytokine-induced collagen loss |
59,259 | |
| PTGDS, CXCL3, RSPO3, NRN1, NFKBIA, CXCL2, GEM, VCAM1, LIF, IL6 and INHBA | Associated with painful synovial sites in early OA | 52 | |
| HSPA1A, DNAJB1, SLC39A8, HTRA3, ATF3, PTGIS and BNIP3 | Associated with painful synovial sites in end-stage OA | 52 |
ECM, extracellular matrix; FLS, fibroblast-like synoviocytes; KL, Kellgren and Lawrence; KOOS, Knee Injury and Osteoarthritis Outcome Score; OA, osteoarthritis; RA, rheumatoid arthritis; TNF, tumour necrosis factor.