The Differential Expressions and Associations of Intracellular and Extracellular GRP78/Bip with Disease Activity and Progression in Rheumatoid Arthritis Patients

GRP78/BiP, a stress-induced protein and autoantigen in rheumatoid arthritis (RA), exhibits different expressions in various biological fluids and tissues, namely serum, synovial fluid (SF), and synovium, all of which are pertinent to the disease activity and progression of RA; however, there is a scarcity of data linking both intracellular and extracellular GRP78/Bip to the disease activity and progression of RA within the realm of rheumatology. This study was undertaken to investigate the differential expression of intracellular and extracellular GRP78/Bip in serum, SF, and synovium, and to determine their association with disease activity and progression in patients with RA. Patients with RA, osteoarthritis (OA), and traumatic meniscal injury (TMI) without radiographic OA were consecutively recruited for the study at our hospital. Among the patients with RA, six different subgroups were established based on their disease activity and progression. Disease activity was measured using the DAS28 criterion, while disease progression was evaluated using the Steinbrocker classification grade. This study conducted a comprehensive analysis of the differential expressions of GRP78/Bip in multiple sample types, including serum, SF, and synovium, with the specific emphasis on their associations with disease activity and progression in RA. The expression levels of GRP78/Bip, TNF-α, and IL-10 were significantly elevated in serum, SF, and synovium of patients with RA when compared to both the CON and iCON groups(P