The Nobel Prize–winning discovery that mature, specialized cells can be reprogrammed to lend them pluripotency (that is, the ability to develop into all tissues of the body) unleashed vast potential in the fields of disease modeling, drug screening, regenerative medicine, and wound healing. The reprogrammed cells are known as induced pluripotent stem cells (iPSCs). In culture, pluripotency must be maintained when iPSCs undergo proliferation in advance of differentiation. Production of large, homogeneous quantities of iPSCs and their differentiation into specific cell products requires precise control of culture conditions, including the concentration, sequencing, and timing of a variety of growth factors and cytokines.
Ensuring a steady concentration of the growth factors and cytokines needed to drive proliferation and preferential differentiation can be time consuming and labor intensive. These proteins are highly labile, with each having a different half-life in cell culture media. When the proteins are added to a culture vessel, their concentrations peak and then rapidly decline. At the same time, the ratios of factors change, altering cell signaling patterns.
When the proteins are replenished by media exchanges, the same pattern repeats. Consider the impact of fibroblast growth factor 2 (FGF2) on iPSCs, which has a half-life of approximately 4 hours in culture medium. At a relatively high concentration, FGF2 provides a pluripotency signal to iPSCs; at a relatively low concentration, it signals differentiation. Peaks and troughs of FGF2 concentration resulting from medium exchanges can lead to the iPSC population getting “mixed signals” and becoming increasingly heterogenous, the opposite of what is needed.
Control culture conditions for induced pluripotent stem cells
FGF2 DISC™ devices consist of biodegradable StemBeads® loaded with recombinant human FGF2 embedded in an inert nonbiodegradable, biocompatible hydrogel. Placed directly into the cell culture vessel, DISC devices enable precise control of the concentration of FGF2 throughout the duration of an experiment, creating a more physiologic environment (Figure 1). StemBeads contained within the DISC device release growth factor at a controlled rate, minimizing variations in concentration and reducing the resulting stress on cells. DISC devices do not degrade and can be easily added or removed from culture vessels.