QuantifyingIn VitroGrowth and Metabolism Kinetics of Human Mesenchymal Stem Cells Using a Mathematical Model

Abstract

Better quantitative understanding of human mesenchymal stem cells (hMSCs) metabolism is needed to identify, understand, and subsequently optimize the processes in expansion of hMSCs in vitro. For this purpose, we analyzed growth of hMSCs in vitro with a mathematical model based on the mass balances for viable cell numbers, glucose, lactate, glutamine, and glutamate. The mathematical modeling had two aims: (1) to estimate kinetic parameters of important metabolites for hMSC monolayer cultures, and (2) to quantitatively assess assumptions on growth of hMSCs. Two cell seeding densities were used to investigate growth and metabolism kinetics of MSCs from three human donors. We analyzed growth up to confluency and used metabolic assumptions described in literature. Results showed a longer initial phase, a slower growth rate, and a higher glucose, lactate, glutamine, and glutamate metabolic rates at the lower cell seeding density. Higher metabolic rates could be induced by a lower contact inhibition effect when seeding at 100 cells/cm2 than when seeding at 1000 cells/cm2. In addition, parameter estimation describing kinetics of hMSCs in culture, depending on the seeding density, showed doubling times in the order of 17-32h, specific glucose consumption in the order of 1.25 x 10(-1) to 3.77 x 10(-1) pmol/cell/h, specific lactate production in the order of 2.48 x 10(-1) to 7.67 x 10(-1)pmol/cell/h, specific glutamine production in the order of 7.04 x 10(-3) to 2.27 pmol/cell/h, and specific glutamate production in the order of 4.87 x 10(-1) to 23.4 pmol/cell/h. Lactate-to-glucose yield ratios confirmed that hMSCs use glucose via anaerobic glycolysis. In addition, glutamine and glutamate metabolic shifts were identified that could be important for understanding growth of hMSCs in vitro. This study showed that the mathematical modeling approach supports quantitative analysis of important mechanisms in proliferation of hMSCs in vitro.

Patterns of Amino Acid Metabolism by Proliferating Human Mesenchymal Stem Cells

“…First, the numbers of viable cells were analyzed. Specific growth rates, glucose, and lactate metabolic rates in static and dynamic cultures were consistent with values found in literature, 22,23,32,35 where average values are 2 · 10 -2 h -1 ; 0.5 picomoles glucose/cell/h and 1 picomoles lactate/cell hour, respectively. Our results were consistent with previous reports that specific growth rates are significantly lower in dynamic than in static culture of hMSCs.…”

“…37,38 In addition, micro-carrier and tissue culture plastic also present important surface differences 39 that account for different specific growth rates between static and dynamic cultures. Further, glycolysis levels (Y lac/glac ) were maintained and were comparable to previous reports of static 22,23,35 and dynamic 30 cultures, where glycolysis and proliferation data suggest that the Warburg effect 40 is the rule rather than the exception in hMSCs metabolism.…”

“…Either one of these factors could have an effect on hMSCs proliferation. 23,36,39 Further, the standard deviations in the data reflect the variability associated with hMSCs in static culture that can be explained by three factors. First, lower cell numbers in static cultures induce smaller changes of concentrations than higher cell numbers in dynamic cultures.…”

“…First, the law of conservation of mass can be applied to determine the kinetics of amino acid transport as has been shown earlier. 4,22,23 Second, the kinetics of amino acid metabolism are connected to the transport of amino acids by diffusion to determine molecular gradients in 3D. As a consequence, the benefit is that the kinetics reveal how the micro-environment of human mesenchymal stem cells (hMSCs) is shaped in time.…”

Expansion of Human Mesenchymal Stem Cells in a Fixed-Bed Bioreactor System Based on Non-Porous Glass Carrier – Part B: Modeling and Scale-up of the System

“…Since glutamine was reported as an unimportant energy source for hMSC only the oxygen and glucose kinetics were taken into account [7]. Figure 1 gives an overview of the model, which considers the mass balance of the conditioning vessel and the fixed bed.…”