ACVR1 and ankylosing spondylitis: Altered expression of miRNA detected in HO. mir148b and mir365 down-regulate ACVR1/Alk-2 expression, whereas mir26a showed a positive effect on its mRNA.Inhibition of miRNAs, miR-146b-5p and -424 suppresses osteocyte maturation. Manipulating miR-574-3p levels both in vitro and in vivo inhibits chondrogenesis. miR-630 downregulated in early HO and used to distinguish HO from other processes in tHO. miR-17-5p upregulated in ankylosing spondylitis (AS) patients versus non-AS individuals. Knockdown and overexpression of miR-17-5p in fibroblasts derived from AS patients modulates osteogenesis.