Table 1.

Characteristic of included studies

Study	Study location	Sample size	Tissue source
Miranda-Duarte et al. [16]	Mexican mestizos	689	PBMCs (SNP-related study)
Nie et al. [17]	China	132	Synovial fluid
Wu et al. [18]	China	70	Plasma
Zhang et al. [19]	China	44	Cartilage
Kmiolek et al. [20]	Poland	26	Treg cells
Rousseau et al. [21]	France	133	Plasma
Shao et al. [22]	China	40	Cartilage
Wang et al. [23]	China	610	Plasma
Papathanasiou et al. [24]	Greece	1688	PBMCs (SNP-related study)
Papathanasiou et al. [25]	Greece	35	Chondrocytes/synoviocytes
Skrzypa et al. [26]	Poland	30	Cartilage/serum
Ali et al. [27]	India	28	Serum
Budd et al. [28]	UK	22	Chondrocytes
Cheleschi et al. [29]	Italy	10	Chondrocytes
Kopanska et al. [30]	Poland	31	Cartilage
Soyocak et al. [31]	Turkey	150	PBMC
Mu et al. [32]	China	60	Synovial fluid
Zakaria et al. [33]	Egypt	56	PBMC
Xu et al. [34]	China	20	Synovial fluid
Wang et al. [35]	China	14	PBMC
Qian et al. [36]	China	30	PBMC
Abou-Zeid et al. [37]	Egypt	105	PBMC
Okuhara et al. [38]	Japan	72	PBMC
Murata et al. [39]	Japan	68	Plasma
Niimoto et al. [40]	Japan	11	PBMC
Nakasa et al. [41]	Japan	6	Synovial tissue

PBMCs peripheral blood mononuclear cells, SNP single nucleotide polymorphism, Treg cells regulator T cells