SphK1 Suppresses Human Dental Pulp Stem Cell Apoptosis by Promoting Glycolysis Under Simulated Microgravity

Area of Science:

• Space life sciences
• Stem cell biology
• Cell metabolism

Background:

• Glycolysis is crucial for mesenchymal stem cell (MSC) proliferation and survival.
• The impact of microgravity on MSC metabolism and apoptosis is not fully understood.
• Investigating simulated microgravity's effects on human dental pulp stem cells (hDPSCs) is important for space biology.

Purpose of the Study:

• To investigate the influence of simulated microgravity (SMG) on glycolytic activity and apoptosis in hDPSCs.
• To elucidate the role of Sphingosine kinase 1 (SphK1) in mediating these effects.
• To confirm the protective role of glycolysis against apoptosis under SMG.

Main Methods:

• Assessed glycolytic flux via lactic acid and glucose measurements.
• Quantified gene expression (HK2, PKM2, LDHA) using qPCR and protein expression (HK2, PKM2) via Western blotting.
• Evaluated apoptosis using annexin V-FITC/PI staining and immunoblotting for apoptosis-related proteins (BAX, BCL-2, cleaved caspase-3).
• Utilized pharmacological inhibitors (PF-543 for SphK1, 2-DG for glycolysis).

Main Results:

• SMG significantly increased glycolytic capacity and reduced apoptosis in hDPSCs.
• SphK1 expression was upregulated under SMG, and its inhibition attenuated both glycolysis and the antiapoptotic effect.
• Inhibition of glycolysis by 2-DG increased apoptosis, confirming glycolysis's protective role.
• These findings highlight SphK1 as a key regulator linking enhanced glycolysis to reduced apoptosis under SMG.

Conclusions:

• Simulated microgravity enhances glycolysis and suppresses apoptosis in hDPSCs, partly through SphK1 upregulation.
• Microgravity conditions may promote stem cell survival and function.
• Targeting glycolytic pathways and SphK1 could be beneficial for maintaining stem cell viability in space environments.