Immuno-based profiling of knee osteoarthritis patients identifies baseline characteristics associated with positive response to autologous platelet-rich plasma injection at one-year follow-up.

BACKGROUND: Osteoarthritis (OA) is a degenerative musculoskeletal disease of multifactorial origin causing chronic disability, despite numerous treatment options for which there are no predictive biomarkers on the different endotypes. We aimed at defining a peripheral blood (PB) profile potentially predictive of early and sustained response to intra-articular injection of autologous platelet-rich plasma (PRP). METHODS: A prospective study was conducted on male and female patients aged 40-74 years, with Kellgren-Lawrence knee OA grade 2-3 candidates to PRP injection. PB was obtained from patients at enrollment prior to PRP injection to assess immune phenotype of PBMCs with multiparametric flow cytometry; serum antioxidant capacity; PBMC expression of molecules involved in inflammatory pathways; serum concentrations of related inflammatory cytokines and chemokines. After one year of follow-up, response was defined based on WOMAC questionnaires and clinical criteria and correlated with the immune profile. RESULTS: Among 109 enrolled patients, 60 had early and sustained response to treatment and 49 were non-responders, irrespective of age, sex, and previous conservative therapy or surgery. Responders had lower oxidative stress and a peculiar profile of inflammatory markers (higher CD40L, Eotaxin 1; G-CSF, GROα, MIP3b, and PD-L1; lower TNFα, PTX3, and PDGF-AA) and immune cell composition (higher circulating CD14+; higher central memory CD8+, lower effector memory CD4+ and terminal effector CD4+ and CD8+ cells; lower Tregs) in the PB at baseline. DISCUSSION: We describe an immunophenotype associated with early and sustained response to PRP treatment in knee OA and submit that this may be candidate to validation for predicting clinical benefit.