Effect of the neurosphere size on the viability and metabolism of neural stem/progenitor cells

Abstract

The objective of this study was to investigate the metabolic activity and viability of the mouse neural stem/progenitor cells (NSPCs) affected by the size of neurospheres. NSPCs dissociated from the forebrain of embryonic 14 days (E14) mice were cultured in flask for 120 h. During cultivation, the diameter distribution of neurospheres, cell viability and metabolic activities were monitored, together with the concentrations of glucose, lactate, glutamine and ammonia in the media. The results show that cell activity decreased with the increment of neurospheres size. When the diameter reached about 100 μm and the concentration of glucose and glutamine were 36.38 and 1.33 mmol/L, the growth of central cells in neurospheres began to surface. Furthermore, when the diameter reached about 100 to 150 μm and the concentrations of glucose and glutamine were 31.11 and 1.15 mmol/L, simultaneously, the death rate of NSPCs was larger than that of the newly born cells within the neurospheres. The metabolic activity of the cells declined to a very low level. This observation can be explained by diffusion limitation of nutrients and metabolic waste inside neurosphere. In conclusion, the mass transfer will be limited when the neurospheres size reaches a critical value of 100 to 150 μm and beyond this critical value, serious impact of nutrient supply and metabolites on the cell viability and metabolism occurs.

Key words: Neural stem/progenitor cells (NSPCs), neurospheres, critical size, metabolism, mass transfer.