MULTIPLICITY OF STEADY STATES IN CONTINUOUS CULTURE OF MAMMALIAN CELLS

Transcription

1 MULTIPLICITY OF STEADY STATES IN CONTINUOUS CULTURE OF MAMMALIAN CELLS Andrew Yongky, Tung Le, Simon Grimm, Wei-Shou Hu Department of Chemical Engineering and Materials Science, University of Minnesota

2 Major incentives for continuous operations Reduced turn around time Steady state operation (a continuous operation need not to be at a steady state)

3 Continuous Process with recycle F, s (1+α) F, s, x V, s, x F, s, x 2 αf, s, cx

4 F, s F, s, x, x d V, s, x

5 F, s F, s, x, x d V, s, x

6 What is a steady state Has meaningful solution(s) when the system s equations are set to Sometimes a system has a unique steady state for a set of operating conditions Other times, has mutliple steady state

7 Stead State Concentrations in Continuous Culture with Cell Recycle Cell and Substrate Concentrations Cell Cell Simple Continuous Culture Washout Substrate Dilution Rate With Cell Recycle Washout Substrate

8 What is a steady state from an operational perspective D =.33; Glc = 7 mm Concentration (mm) Cell conc 8 6 Lac 4 2 Glc Time (hr) 8 1 Cell Conc (x1 6 cells/ml) Flux (mm/h) Growth Rate JGlc JLac.1 5 Time (hr) 1 Growth Rate (hr-1) Under one set of conditions (dilution rate, feed concentration), the state reaches constant values Key physiological parameters: growth rate, metabolism are constant

9 What is a steady state from an operational perspective D =.33; Glc = 7 mm Concentration (mm) Cell conc 8 6 Lac 4 2 Glc Time (hr) 8 1 Cell Conc (x1 6 cells/ml) Flux (mm/h) Growth Rate JGlc JLac 5 1 Time (hr) The same data if obtained from perfusion culture, may not be SS growth rate, metabolism may not be constant

10 Continuous Process with recycle F, s (1+α) F, s, x V, s, x F, s, x 2 αf, s, cx

11 The Theme Multiple metabolic state when cells grow at one set of growth rate, glucose and lactate concentrations The metabolic steady state multiplicity leads to cell concentration multiplicity If we ensure the same steady state is achieved in different runs, process will be more robust

12 Glucose High flux state Lactate Pyruvate AcetylCoA Cell Mass CO 2 TCA cycle O 2 NH 3 Glutamine Amino Acids

13 Glucose Low flux state Lactate Pyruvate AcetylCoA Cell Mass CO 2 TCA cycle O 2 NH 3 Glutamine Amino Acids

14 Glucose Low flux state Lactate Pyruvate AcetylCoA Cell Mass CO 2 TCA cycle O 2 NH 3 Glutamine Amino Acids

15 Continuous Culture with Metabolic Shift Cell Conc. (1 9 /L) Fedbatch Batch Glucose (g/l) L/ G (mol/mol) Time (hr) Lactate (g/l) Time (hr)

16 Distinct Steady States Corresponding to Different Metabolic States L/ G Cell Conc (1 6 /ml) Time (hrs)

17 The system: A ball A contour of surface on which it can move

18 Steady State, where things can be steady, at equilibrium Unstable steady state Stable steady state No steady state

19 The system: A ball A contour of surface that it can move Force: gravitational force, external force, friction force

20 The system: A ball A contour of surface that it can move The stability of the system can be shown mathematically using equations describing the system Force: gravitational force, external force, friction force

21 Unstable steady state Stable steady state

22 When the state of a system changes, it moves along where the system has stable steady state.

23 Stability analysis can be applied to chemical reaction systems The kinetic equations for all glycolysis, PPP and TCA cycle enzymes are all very well characterized

24 Allosteric Regulations in Glycolysis Pathway Fructose-2,6- Bisphosphate PFK2 Glucose Glucose-6- Phosphate Hexokinase Fructose-6-Phosphate Phosphofructokinase Fructose-1,6- Bisphosphate Inhibition Activation Lactate Phosphoenol Pyruvate Pyruvate Kinase Pyruvate Pyruvate mito

25 Glycolysis Flux (mm/h) Stable, high flux state Unstable steady state, unrealizable Stable, low flux state Extracellular Glucose (mm)

26 When the state of a system changes, it moves along where the system has stable steady state.

27 Glycolysis Flux (mm/h) Extracellular Glucose (mm)

28 Allosteric Regulations in Glycolysis Pathway Fructose-2,6- Bisphosphate PFK2 Glucose Glucose-6- Phosphate Hexokinase Fructose-6-Phosphate Phosphofructokinase Fructose-1,6- Bisphosphate Inhibition Activation Lactate Phosphoenol Pyruvate Pyruvate Kinase Pyruvate Pyruvate mito

29 Pyruvate Akt Down-regulated and p53 Up-regulated in Late Stage Glucose Akt AMPK GLUT1 Glucose HK Glucose-6- Phosphate p53 Fructose-2,6- Bisphosphate PFK2 PFK2 Fructose-6- Phosphate Myc Hif1a PFK1 Fructose-1,6- Bisphosphate PGAM Inhibition Activation Phosphoenol Pyruvate Pyruvate Kinase

30 Bistabilty in Central Metabolism Glycolysis Flux (mm/h) High Flux State Extracellular Glucose (mm)

31 Effect of Lactate on Glycolytic Flux Glycolysis Flux (mm/h) Lactate (mm) Glucose (mm) 1

32 Effect of Lactate on Glycolytic Flux Glycolysis Flux (mm/h) Lactate (mm) Glucose (mm)

33 Effect of Lactate on Glycolytic Flux Glycolysis Flux (mm/h) Lactate (mm) Glucose (mm)

34 Effect of AKT on Glycolytic Activity

35 Trajectory of Cells in Shifting to Low Flux State

36 Trajectory of Cells in Shifting to Low Flux State

37 Trajectory of Cells in Shifting to Low Flux State

38 Figure 6: Transient behavior demonstrating effect of glucose concentration perturbations on cellular metabolic state 8 C A 6 B E 1 Glc (mm) 5 D Lac (mm) 1

39 Multi-scale Model: Metabolism Model in Continuous Culture F, s F, s, x, x d V, s, x

40 Glucose (mm) Bistability in Continuous Culture Multiscale model simulation Glc = 8 mm Dilution Rate (hr -1 ) 2 8 Cell Conc (x1 6 cells/ml) Dilution Rate (hr -1 ) J Glc (mm/hr) Dilution Rate (hr -1 )

41 Bistability in Continuous Culture 8 12 J Glc (mm/hr) Glucose (mm) Cell Conc (x1 6 cells/ml) Glucose (mm)

42 Cell Conc (x1 6 cells/ml) Cell Conc (x1 6 cells/ml) Cell Conc (x1 6 cells/ml) Glc = 15 mm Dilution Rate (hr -1 ) Glc = 8 mm Dilution Rate (hr -1 ) Glc = 5 mm Effect of Glucose Feed Dilution Rate (hr -1 ) J Glc (mm/hr) J Glc (mm/hr) J Glc (mm/hr) Dilution Rate (hr -1 ) Dilution Rate (hr -1 ) Dilution Rate (hr -1 )

43 Distinct Steady States Corresponding to Different Metabolic States L/ G Cell Conc (1 6 /ml) Time (hrs)

44 Transient Trajectory of Culture with High Metabolic Flux D =.33; Glc = 7 mm Concentration (mm) Lac Cell conc Glc Cell Conc (x1 6 cells/ml) Flux (mm/h) JLac Growth Rate JGlc Growth Rate (hr-1) Time (hr) Time (hr) 8 1

45 Transient Trajectory of Culture with Low Metabolic Flux D =.33; Glc = 7 mm Concentration (mm) Cell conc 8 6 Lac 4 2 Glc Time (hr) 8 1 Cell Conc (x1 6 cells/ml) Flux (mm/h) Growth Rate JGlc JLac.1 5 Time (hr) 1 Growth Rate (hr-1)

46 Benefit of slow growth rate? Transcriptome analysis effect of culture age?

47 Conclusion Physiological steady state - truly benefit continuous operation Metabolic regulation and growth causes metabolic steady state multiplicity Continuous cell culture reactor multiple steady state Different trajectories lead to different steady state

48 Thank you!