SIRT1 directly regulates SOX2 to maintain self-renewal and multipotency in bone marrow-derived mesenchymal stem cells

Area of Science:

• Stem Cell Biology
• Molecular Biology
• Biochemistry

Background:

• SOX2 is essential for mesenchymal stem cell (MSC) self-renewal and multipotency.
• The regulatory mechanisms governing SOX2 stability and function in MSCs are not fully understood.

Purpose of the Study:

• To elucidate the role of sirtuin 1 (SIRT1) in regulating SOX2 stability and function in human bone marrow-derived MSCs (BM-MSCs).
• To investigate the impact of the SIRT1-SOX2 interaction on MSC self-renewal and differentiation capacities.

Main Methods:

• RNA interference (RNAi) to deplete SIRT1 in BM-MSCs.
• Immunoprecipitation to assess direct binding between SIRT1 and SOX2.
• Analysis of SOX2 acetylation, nuclear export, ubiquitination, and proteasomal degradation.
• Treatment with trichostatin A (TSA) and resveratrol to modulate SIRT1 activity.
• Assessment of colony-forming ability and differentiation potential (osteogenic and adipogenic).

Main Results:

• SIRT1 depletion reduced SOX2 protein levels, impairing BM-MSC self-renewal and differentiation.
• SIRT1 directly binds to SOX2.
• SIRT1 depletion induced SOX2 acetylation, nuclear export, and ubiquitination, leading to proteasomal degradation.
• Resveratrol, a SIRT1 activator, counteracted TSA-induced SOX2 suppression and reduced SOX2 acetylation and ubiquitination.
• Resveratrol enhanced BM-MSC colony formation and differentiation potential in a dose-dependent manner, which was abrogated by SOX2 depletion.

Conclusions:

• The SIRT1-SOX2 axis is critical for maintaining the self-renewal and multipotency of BM-MSCs.
• SIRT1 promotes SOX2 stability by inhibiting its nuclear export and subsequent ubiquitination, thereby preserving SOX2 protein levels in the nucleus.
• SIRT1-mediated deacetylation is a key mechanism for maintaining SOX2 function in BM-MSCs.