High density bioprocessing of human pluripotent stem cells by metabolic control and in silico modeling

To harness the full potential of human pluripotent stem cells (hPSCs) we combined instrumented stirred tank bioreactor (STBR) technology with the power of in silico process modeling to overcome substantial, hPSC‐specific hurdles toward their mass production. Perfused suspension culture (3D) of matrix‐free hPSC aggregates in STBRs was applied to identify and control process‐limiting parameters including pH, dissolved oxygen, glucose and lactate levels, and the obviation of osmolality peaks provoked by high density culture. Media supplements promoted single cell‐based process inoculation and hydrodynamic aggregate size control. Wet lab‐derived process characteristics enabled predictive in silico modeling as a new rational for hPSC cultivation. Consequently, hPSC line‐independent maintenance of exponential cell proliferation was achieved. The strategy yielded 70‐fold cell expansion in 7 days achieving an unmatched density of 35 × 10⁶ cells/mL equivalent to 5.25 billion hPSC in 150 mL scale while pluripotency, differentiation potential, and karyotype stability was maintained. In parallel, media requirements were reduced by 75% demonstrating the outstanding increase in efficiency. Minimal input to our in silico model accurately predicts all main process parameters; combined with calculation‐controlled hPSC aggregation kinetics, linear process upscaling is also enabled and demonstrated for up to 500 mL scale in an independent bioreactor system. Thus, by merging applied stem cell research with recent knowhow from industrial cell fermentation, a new level of hPSC bioprocessing is revealed fueling their automated production for industrial and therapeutic applications.

Pantothenic Acid, Vitamin C, and Biotin Play Important Roles in the Growth of Lactobacillus helveticus

Lactobacillus helveticus is an important lactic acid bacterium. The strains used in this study have proven probiotic function, and the potential to produce functional dairy products and bioactive peptides. To explore the effects of vitamins on the growth of L. helveticus, a chemically defined medium was designed and nine vitamins were tested. Pantothenic acid (Vb5), vitamin C (Vc), and biotin were necessary for the growth of L. helveticus CICC 22171. These three vitamins had an important effect on the glucose metabolism and energy metabolism of strain CICC 22171. Through transcriptomic analysis, we found that three vitamins were related to the synthesis of fatty acids and participate in the energy supply of the cells. Additionally, Vb5 was involved in the metabolism of bacterial proteins and lipids and was related to the activity of various enzymes. The results indicated that Vc was involved in protein metabolism, and biotin affected the intracellular transport mechanism of bacteria. The ability of vitamins to promote the growth of the strain was verified in skim milk medium. The results indicated that Vc, biotin, and Vb5 could promote the proliferation of L. helveticus but had no significant effect on Lactobacillus bulgaricus.

Polymodal Transient Receptor Potential Vanilloid (TRPV) Ion Channels in Chondrogenic Cells

Mature and developing chondrocytes exist in a microenvironment where mechanical load, changes of temperature, osmolarity and acidic pH may influence cellular metabolism. Polymodal Transient Receptor Potential Vanilloid (TRPV) receptors are environmental sensors mediating responses through activation of linked intracellular signalling pathways. In chondrogenic high density cultures established from limb buds of chicken and mouse embryos, we identified TRPV1, TRPV2, TRPV3, TRPV4 and TRPV6 mRNA expression with RT-PCR. In both cultures, a switch in the expression pattern of TRPVs was observed during cartilage formation. The inhibition of TRPVs with the non-selective calcium channel blocker ruthenium red diminished chondrogenesis and caused significant inhibition of proliferation. Incubating cell cultures at 41 °C elevated the expression of TRPV1, and increased cartilage matrix production. When chondrogenic cells were exposed to mechanical load at the time of their differentiation into matrix producing chondrocytes, we detected increased mRNA levels of TRPV3. Our results demonstrate that developing chondrocytes express a full palette of TRPV channels and the switch in the expression pattern suggests differentiation stage-dependent roles of TRPVs during cartilage formation. As TRPV1 and TRPV3 expression was altered by thermal and mechanical stimuli, respectively, these are candidate channels that contribute to the transduction of environmental stimuli in chondrogenic cells.

Hydroxyapatite-pulp composite fiber sheet bed: A new material for the immobilization of CHO-K1 cells

A new immobilization material for cell culture, ahydroxyapatite-pulp composite fiber (HAPC) sheet bed, was usedto grow CHO-K1 cells. The sheet bed for cell culture wasprepared from HAPC fiber by paper-making techniques. Scanning electron microscopic analysis revealed that the HAPCsheet bed had a structure consisting of piled fibers with spaces 10-200 mum in diameter and a pore surface area of 0.32 m(2) g(-1). Using a 25 x 25 mm(2) squareHAPC sheet bed 0.41 mm in thickness (85 g m(-2) basis weight) for cell culture, CHO-K1 cells grew to a cell densityof 3.7 x 10(7) cells cm(-3) in a 60 mm plastic dish over a 6-day culture period. High-density culture of CHO-K1 cells was successfully performed using the HAPC sheet bed in a 500 ml spinner flask over a 21-day culture period. The HAPC sheet bed, wound around the stirrer paddle, was rotated in the spinner flask in order to supply nutrientsand remove waste products efficiently. The HAPC sheet bedhas a large surface area to support cell growth and there islarge diffusion space inside of the bed. This newautoclavable substrate for anchorage-dependent cells can be easily scaled-up.