FSTL1 and osteoarthritis: Another study showed that when synoviocytes from the synovial tissues of patients with osteoarthritis were exposed to recombinant FSTL-1 protein, the levels of some inflammatory factors, such as TNF-α, IL-6, and IL-1β, were significantly increased, and the activation of the NF-κB signaling pathway was also significantly upregulated [25].