To ensure that the difference observed was indeed linked to a difference in HOTAIR expression according to diseases and not to a difference in the number of fibroblasts in the tissue, we normalized the expression of HOTAIR in the tissue to a fibroblast specific gene, namely COL3A1. This approach did not change the result (Fig. 3f), confirming the difference in HOTAIR expression between OA and RA in vivo. The gene discussed is HOTAIR; the disease is rheumatoid arthritis.