YTHDF3 regulates IL32 mRNA stability to promote osteogenic differentiation of bone mesenchymal stem cells in ankylosing spondylitis

As a member of the family of the YTH domain and a an m6A reader, YTHDF3 is implicated in cancer and inflammatory diseases. However, its function in ankylosing spondylitis (AS)-a chronic inflammatory disease marked by aberrant bone formation-is still mysterious. The research set out to study how YTHDF3 may promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) in AS and delineate the underlying mechanism.

BMSCs were separated from AS and healthy controls patients. YTHDF3 expression was manipulated using lentiviral transduction. Alkaline phosphatase (ALP) activity and Alizarin Red staining were utilized to assess osteogenic differentiation. This work employed quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blot (WB) analysis, and enzyme-linked immunosorbent assay to determine the expression of osteogenic markers, including RUNX2, SP7, BMP2, and OCN. Furthermore, RNA sequencing (RNA-seq), m6A sequencing (m6A-seq), and RNA immunoprecipitation were performed to identify downstream targets, particularly focusing interleukin 32 (IL32). Additionally, RNA stability assays and fluorescence in situ hybridization were used to evaluate the role of YTHDF3 in stabilizing IL32.

YTHDF3 expression was notably increased in AS-BMSCs in comparison with the control group. YTHDF3 overexpression promoted osteogenic differentiation, as shown by the rise in ALP activities, boosted calcium deposition, and upregulation of osteogenic markers. In contrast, the YTHDF3 knockdown inhibited these processes. IL32 was identified as a key downstream target using RNA-seq and m6A-seq, whose mRNA stability was directly regulated by YTHDF3 via m6A modifications. Notably, increased IL32 expression in AS contributed to osteogenesis.

YTHDF3 prevents IL32 mRNA degradation and promotes osteogenic differentiation of AS-BMSCs in an m6A-dependent manner. The results shed light on previous questions regarding the molecular mechanisms behind ectopic bone formation in AS, identifying YTHDF3 as a potential therapeutic target for controlling pathological bone formation.