Platelet-Rich Plasma Activates Proinflammatory Signaling Pathways and Induces Oxidative Stress in Tendon Fibroblasts

Abstract

Background Tendon injuries are one of the most common musculoskeletal conditions in active patients. Platelet rich plasma (PRP) has shown some promise in the treatment of tendon disorders, but little is known as to the mechanisms by which PRP can improve tendon regeneration. PRP contains numerous different growth factors and cytokines which activate various cellular signaling cascades, but it has been difficult to determine precisely which signaling pathways and cellular responses are activated following PRP treatment. Additionally, macrophages play an important role in modulating tendon regeneration, but the influence of PRP on determining whether macrophages assume a proinflammatory or antiinflammatory phenotype remains unknown. Hypothesis/Purpose We used genome wide expression profiling, bioinformatics and protein analysis to determine the cellular pathways activated in fibroblasts treated with PRP. We also evaluated the effect of PRP on macrophage polarization. Study Design Controlled laboratory study. Methods Tendon fibroblasts or macrophages from rats were cultured and treated with either platelet poor plasma (PPP) or PRP. RNA or protein was isolated from cells and analyzed using microarrays, qPCR, immunoblot or bioinformatics techniques. Results Pathway analysis determined that the most highly induced signaling pathways in PRP treated tendon fibroblasts was the TNFα and NFκB pathways. PRP also downregulated the expression of ECM genes and induced the expression of autophagy related genes and reactive oxygen species (ROS) genes and protein markers in tendon fibroblasts. PRP failed to have a major impact on markers of macrophage polarization. Conclusions PRP induces an inflammatory response in tendon fibroblasts which leads to the formation of ROS and activation of oxidative stress pathways. PRP does not appear to significantly modulate macrophage polarization. Clinical Relevance PRP might act by inducing a transient inflammatory event which could then trigger a tissue regeneration response.

Sex differences in tendon structure and function

“…RNA isolation, microarray analysis, and quantitative PCR (qPCR) were performed as previously described . A total of six animals were used for each sex.…”

Regeneration of Skeletal Muscle After Eccentric Injury

“…However, in a blunt force contusion injury model in rats, PRP treatment does not improve force production compared to controls 73 . In cultured connective tissue fibroblasts, PRP turns on several pro-inflammatory pathways, including the potent TNF-α/NFκB pathway 74 . While the mechanism of action of PRP is not entirely clear, PRP may work in chronic injuries by triggering an acute bout of inflammation that is followed by a regenerative response 74 .…”

“…In cultured connective tissue fibroblasts, PRP turns on several pro-inflammatory pathways, including the potent TNF-α/NFκB pathway 74 . While the mechanism of action of PRP is not entirely clear, PRP may work in chronic injuries by triggering an acute bout of inflammation that is followed by a regenerative response 74 . Although the utilization of PRP is gaining popularity, based on the mixed results of these small-scale laboratory studies and the lack of any large scale clinical trials 71 , there continues to be little evidence to support PRP use in the treatment of muscle strain injuries.…”

Pathogenesis and management of tendinopathies in sports medicine

“…Platelets are thought to be particularly important for injured tissues to properly heal, as they are enriched with multiple growth factors and cytokines, including transforming growth factor beta (TGFb), interleukins (ILs), fibroblast growth factors (FGFs), platelet-derived growth factors (PDGFs), vascular endothelial growth factors (VEGFs), connective tissue growth factor (CTGF), and others. 56 These proteins are thought to enhance tissue healing when delivered locally. 2 However, recent work using wide-scale genome profiling and bioinformatics has reported PRP to work through inducing local inflammation in tissue.…”

“…2 However, recent work using wide-scale genome profiling and bioinformatics has reported PRP to work through inducing local inflammation in tissue. 56 There have been several clinical studies to explore the effectiveness of PRP in treating patients with tendinopathy, but have produced mixed results. 57,58 Some of the most encouraging results have come in the treatment of lateral epicondylitis, with PRP demonstrating a near twofold improvement in outcomes compared to corticosteroids.…”