Knockdown of SIGLEC1 inhibits osteogenic differentiation to alleviate ankylosing spondylitis progression by suppressing the TGF-β1/SMAD signaling pathway.

Ankylosing spondylitis (AS) is a chronic inflammatory joint disease, which can result in disability in severe cases and endanger physical health. Two microarray datasets related to AS were selected from NCBI for bioinformatics analysis. Differentially expressed genes (DEGs) were screened and protein-protein interaction network was constructed to obtain hub genes. hSMSCs were injected with TNF-α to construct AS cell models. The hSMSCs were transfected with SIGLEC1 siRNA to silence SIGLEC1 expression. CCK-8, western blot, qRT-PCR, and ELISA were performed to detect the effects of SIGLEC1 knockdown on cell proliferation, osteogenic differentiation (ALP, BMP2, Osterix, and Runx2), inflammation (IL-23 and IL-6), and TGF-β1/SMAD signaling pathway (SMAD3, SMAD7 and TGF-β1). A TGF-β1 activator was applied for feedback function assays. A total of 29 common DEGs were screened from GSE181364 and GSE221786, and the key gene SIGLEC1 was selected. Knockdown of SIGLEC1 promoted cell proliferation and inhibited ALP activity, the level of BMP2, Osterix and Runx2 in TNF-α-induced hSMSCs, as well as the decreased inflammatory factors IL-23 and IL-6. Furthermore, knockdown of SIGLEC1 inhibited the expression of TGF-β1/SMAD signaling pathway related proteins, while the treatment of TGF-β1 activator weakened the inhibiting effects of sh-SIGLEC1 on the osteogenic differentiation and inflammation in TNF-α-induced hSMSCs. In summary, knockdown of SIGLEC1 promoted cell proliferation and inhibited osteogenic differentiation and inflammation by inhibiting TGF-β1/SMAD signaling pathway, thereby suppressing the development of AS.