Ion Homeostasis during the Growth of Human Mesenchymal Stem Culture. I. Density-Dependent Changes of Intracellular K+ and Na+ Content and K+ Influxes.

In this study, we reported proliferation-related changes in cell K⁺ and Na⁺ content and K⁺ influxes in cultivated human mesenchymal stem cells (MSCs). The intracellular K⁺ content calculated per cell protein amount was found to decrease in the growing culture, whereas intracellular Na⁺ content was not significantly changed. It was also revealed that, at higher densities of an hMSC monolayer, the ouabain-sensitive K⁺ influx was decreased thus indicating a decline in Na⁺, K⁺ pump-mediated transport. We analyzed the cell cycle profiles of hMSC cultures and found that, under optimal culture conditions in high-density cultures, the decline in K⁺ content per cell protein was correlated with accumulation of G₁ cells and slowing down cell proliferation in the population. It is concluded that cell K⁺ content per cell protein is an informative test for assessing the functional status of stem cells in vitro. [ABSTRACT FROM AUTHOR]