Novel therapeutic targets in osteoarthritis: Narrative review on knock-out genes involved in disease development in mouse animal models

Osteoarthritis (OA) can affect every joint, especially the knee. Given the complexity of this pathology, OA is difficult to treat with current therapies, which only relieve pain and inflammation and are not capable of restoring tissues once OA has started. Currently, researchers focus on finding a therapeutic strategy that may help to arrest disease progression. The present narrative review gives an overview of the genes involved in the development and progression of OA, assessing in vivo studies performed in knock-out mice affected by OA, to suggest new therapeutic strategies. The article search was performed on the PubMed database and www.webofknowledge.com website with the following keywords: "knee osteoarthritis" AND "knockout mice". The included studies were in English and published from 2005 to 2015. Additional papers were found within the references of the selected articles. In the 55 analyzed in vivo studies, genes mainly affected chondrocyte homeostasis, inflammatory processes, extracellular matrix and the relationship between obesity and OA. Genes are defined as inducing, preventing and not influencing OA. This review shows that joint homeostasis depends on a variety of genetic factors, and preventing or restoring the loss of a gene encoding for protective proteins, or inhibiting the expression of proteins that induce OA, might be a potential therapeutic approach. However, conclusions cannot be drawn because of the wide variability concerning the technique used for OA induction, the role of the genes, the method for tissue evaluations and the lack of assessments of all joint tissues.