Intra-articular infiltration of adipose-derived stromal vascular fraction cells slows the clinical progression of moderate-severe knee osteoarthritis: hypothesis on the regulatory role of intra-articular adipose tissue

BACKGROUND: The infiltration of the stromal vascular fraction (SVF) of autologous adipose tissue to treat osteoarthritis has been used for several years demonstrating its safety and noticeable efficacy. This article presents clinical data from patients afftected by moderate and severe knee osteoarthritis demonstrating safety and clinical efficacy of the treatment when this autologous cell product is injected in the knee joint and patients evaluated post-operatively after 1 year. However, what do we know about the mechanism that underlies this clinical improvement? This article proposes, for the first time in our opinion, a hypothesis of the mode of action that involves structural and molecular interactions between SVF and infrapatellar fat pad (IFP). As consequence, there would be a re-education of intra-articular adipose tissue, which we consider a key player for the clinical effect observed in the mid and long term mainly due to immuno-regulatory mechanisms. METHODS: This is a retrospective and not controlled study that evaluated 50 patients (100 joints) ranging from 50 to 89 years old, separated by age cohorts. Clinical efficacy was assessed using the Lequesne, WOMAC, and VAS scales, by ultrasound control and quantification of the biochemical profiles of synovial fluid. RESULTS: There were no serious adverse effects. All the indexes studied showed a significant clinical improvement after 1-year follow-up for all ages and OA degree groups. This finding was correlated with the ultrasound observations and biochemical data, which show a marked decrease in catabolic and pro-inflammatory molecules (MMP-2, IL-1B, IL-6, and IL-8) and significant increase for anabolic and anti-inflammatory molecules (IGF-1 and IL-10). CONCLUSIONS: We conclude that intra-articular SVF infiltration for knee OA treatment is safe and effective during 1 year. We propose that applied SVF cells cause a cascade of molecular and structural events that, through complex interactions between IFP and SVF, re-educating the intra-articular fatty tissue towards a homeostatic, protective, and anti-inflammatory function, which will ultimately promote the restructuring and regeneration of damaged tissues.