In a recent comprehensive study on the role of different immunological and non-immunological pathways in the behavior of RA FLSs, unexpectedly, the “Huntington’s Disease Signaling” pathway and specifically huntingtin-interacting protein-1 (HIP1) was introduced as the regulator of matrix invasion in RA FLSs [89]. This evidence concerns the gene HIP1 and rheumatoid arthritis.