TREM1 and rheumatoid arthritis: Although these published functional tests were predominantly archived in the RA scenario, especially with the RA synovial fibroblasts, our current study identified expression of FAP and TREM-1 significantly upregulated in both synovium and cartilage of OA patients, strongly suggesting that lowering FAP and TREM-1 might be beneficial for both RA and OA patients.