Papel de NF-κB Y miRNA-34a en la patogénesis de la osteoartritis y como posible diana de las nuevas terapias biológicas

Introduction: Osteoarthritis is a degenerative joint disease that is not only quite common, but also a clear example of a disease with a complex etiology, with its cause stemming from the interaction of acquired factors and genetic inheritance. NF-κB is a protein complex that controls DNA transcription and is part of the cellular response to several stimuli such as stress, cytokines, or viral or bacterial antigens. A microRNA is a small non-coding RNA which regulates gene expression by inhibiting messenger RNA. Over the last decade, the epigenetic mechanisms that occur during the degenerative process of osteoarthritis and the inflammatory phenomena have become key targets of study. Methods and material: A clinical study was conducted on 27 patients who underwent a total knee arthroplasty for symptomatic osteoarthritis. subsequently, a histological and immunohistochemical study was performed on the proximal tibia cartilage samples obtained from these patients during the procedure, and an experimental model for chondrocyte cultivation was developed. Three independent cultures were set up, one control, one stimulated with IL-1β and a third with IL-1β in absence and the presence of a NF-κB inhibitor called Parthenolide. Western-Blot was used to analyse the expression of NF-κB; qPCR-RT was used for mRNA34a and mRNA from NF-κB, and finally, ELISA was used for the expression of MCP-1. Results: The average age of the patients who underwent surgery was 70.03, with 66.7% of the cases being women. 51.9% of the patients presented disabling pain associated with repeated knee effusions with major functional incapacity. The Knee-society-score analysis showed average scores of 19.85, while 70.4% of the patients were grade III on the Albhäck scale. In 70.04% of the patients, there was no clinical and radiological correlation. Histologically, it manifests as the loss of cartilage flexibility provokes a tear of the collagen fibers and the appearance of cleavages, that later evolve into fractures and finally ulcerations. The immunohistochemical study highlights a strong NF-κB expression at the cytoplasm level of the chondrocytes. In the chondrocytes cultures, the IL-1β considerably increased the NF-κB expression, however, the increase of phosphorylated form, NF-κB-p-p65 is very discreet, and as such, it is not activated in those cells. Similarly, the addition of Parthenolide did not obtain the expected results, as the levels of both are similar to those obtained after the stimulation with IL-1β, and not less, as would be expected. The PCR analysis shows a greater expression of mRNA-NF-κB in the cells inhibited with Parthenolide compared to the control cells, while the analysis of the miR-34a expression shows an increase when the cells are induced by IL-1β, and a decrease when they are inhibited with Parthenolide. The stimulation of chondrocyte with IL-1β caused a notable increase of MCP-1, while the inhibition caused a marked decrease. Discussion and conclusions: Osteoarthritis of the knee is a degenerative joint disease with a significant inflammatory aspect that affects patients in their later years, most often women, with a significant clinical-radiological disassociation. Identifying and quantifying the NF-κB proteins supports the idea that Parthenolide acts to inhibit the path of NF-κB phosphorylation, leading to the accumulation of it to cytoplasmic level, but also its deactivation, which is corroborated by the MCP-1 expression in the different cultures. The results obtained suggest that miR-34a acts as a positive modulator for the expression of the NF-κB gene, expressing itself to activate NF-κB after being stimulated by IL-1β and silenced by the cytoplasmic increase of NF-κB-p65, even if no direct relation between them has been observed. Hence, NF-κB and miR-34a have become a future therapeutic target for continued analysis, as more studies are necessary regarding its functional mechanisms, in order to use them for therapeutic means.