Indoxyl Sulfate Inhibits Osteogenesis in Bone Marrow Mesenchymal Stem Cells through the AhR/Hes1 Pathway

Area of Science:

• Nephrology
• Bone Biology
• Stem Cell Biology

Background:

• Chronic kidney disease (CKD) is associated with bone disorders like low turnover osteodystrophy.
• Uremic toxins, including indoxyl sulfate (IS), are implicated in impaired bone formation.
• The aryl hydrocarbon receptor (AhR) pathway is known to suppress osteogenic differentiation in bone marrow mesenchymal stem cells (BMSCs).

Purpose of the Study:

• To investigate whether indoxyl sulfate (IS) affects BMSC osteogenesis through the AhR/Hes1 signaling pathway.
• To elucidate the molecular mechanisms by which IS impacts early bone formation.

Main Methods:

• Cultured mouse BMSCs (D1 cells) and treated them with varying concentrations of IS.
• Measured mineralization and expression of key osteogenesis genes (Runx2, Bmp2, Alp, Oc).
• Assessed AhR and Hes1 expression levels, and utilized AhR antagonists and gene knockdown (Ahr) to confirm pathway involvement.

Main Results:

• IS significantly reduced BMSC mineralization and downregulated osteogenesis genes (Runx2, Bmp2, Alp, Oc) at 2-50 μM concentrations.
• The inhibitory effects of IS on osteogenesis were reversed by AhR antagonism and Ahr knockdown.
• IS induced Hes1 expression via AhR signaling, leading to suppressed Runx2 and Bmp2 transcription.

Conclusions:

• Indoxyl sulfate inhibits early osteogenesis in BMSCs by activating the AhR/Hes1 pathway.
• This pathway suppresses the transcription of critical osteogenic genes Runx2 and Bmp2.
• Findings offer potential therapeutic targets for managing bone disorders in CKD patients.