The mechanism of action of platelet-rich plasma for knee osteoarthritis: a systematic review

Abstract

Background: Platelet-rich plasma (PRP) is a biological intra-articular therapy that has shown good clinical outcomes in patients with knee osteoarthritis (OA) and has been widely studied from in vitro to pre-clinical animal models. We aimed to synthesize non-clinical evidence regarding the different effects related to PRP. Methods: A systematic literature review was conducted in the MEDLINE, EMBASE, and Google Scholar databases in December 2020. Studies were included if they were non-clinical basic science publications describing the effect of PRP treatment, studies focused on knee OA, and articles reporting the use of PRP or a similar platelet-derived product. Included articles were assessed and categorized based on the effect or the mechanism of the action described. The main findings of each study were obtained and analyzed. Results: A total of 41 articles were included to review the outcomes of interest. The most frequently reported mechanism was the modulation of genes involved in synthesizing and degrading the cartilage extracellular matrix (ECM), followed by ECM morphological analysis, inflammation, and cell proliferation. PRP preparations with low and high content of leukocytes were equally reported. Conclusions: The studies reviewed provide evidence for several ways in which PRP can act once it is present in the intra-articular environment. The vast majority of data support a beneficial effect of PRP therapy, especially for leukocyte-poor PRP formulations. The evidence collected gives us a clue as to what the mechanism of action could be. However, the great heterogeneity in the study formulations and models implies further investigation.

Keywords

• Platelet-rich plasma. Knee osteoarthritis. Cartilage. Anti-inflammatory. Systematic review.