Density-Dependent Metabolic Heterogeneity in Human Mesenchymal Stem Cells

Area of Science:

• Cell Biology
• Metabolic Profiling
• Stem Cell Biology

Background:

• Human mesenchymal stem cells (hMSCs) are known for their heterogeneity, with subpopulations exhibiting varied properties.
• Culturing hMSCs at different densities is a common method to demonstrate these differences in proliferation, multipotency, and function.

Purpose of the Study:

• To investigate the distinct metabolic profiles of hMSC subpopulations enriched at different culture densities.
• To test the hypothesis that clonogenic hMSCs, enriched in low-density cultures, have a unique metabolic phenotype.

Main Methods:

• hMSCs were cultured at clonal (CD), low (LD), medium (MD), and high (HD) densities.
• Global metabolic profiling was performed using gas chromatography-mass spectrometry (GC-MS).
• Metabolic inhibitors were used to assess energy metabolism, glutamine metabolism, and redox state.

Main Results:

• Low-density cultures (LD/CD) showed higher CD146 expression and colony-forming activity compared to medium/high-density (MD/HD) cultures.
• Metabolic profiling revealed distinct differences between LD and HD cultures, with density-dependent variations in glycolysis and TCA cycle coupling.
• Density-dependent differences were observed in glycolysis versus oxidative phosphorylation (OXPHOS) for ATP generation, glutamine metabolism, pentose phosphate pathway dependence, and ROS sensitivity.

Conclusions:

• Significant metabolic heterogeneity exists within hMSC cultures, primarily driven by culture density.
• Active OXPHOS is not essential for proliferation in low-density cultures but contributes to senescence in high-density cultures.
• The distinct metabolic characteristics of clonogenic subpopulations offer potential for optimizing in vitro hMSC expansion.