Abstract

Common
problems with the use of growth factors (GFs) in cell culture systems, whether
for modelling disease or otherwise, include the need for repeated, frequent
additions and/or large doses of GF. Both of these issues arise out of a need to
compensate for short half-lives of GFs. Large doses mean that cells are
temporarily exposed to artificially high, physiologically irrelevant levels of
GF and repetitive additions of GF disturb the system. In collaboration with Kyoto Institute of
Technology, we developed a novel sustained release growth factor technology
which encapsulates GFs in a crystalline protein lattice, protecting and
preserving their function. These protein crystals are produced in insect cells
by co-expression of polyhedrin protein and a cargo protein. The resulting PODS®
(POlyhedrin Delivery System) protein crystals are highly
stable and degrade slowly, resulting in a steady release of cargo protein i.e.
GF over several weeks. Here, we outline how PODS® crystals can be applied to
improve a 3D organoid differentiation protocol.