Establishment of a cryo-bank of lineage-committed neural progenitor cells produced from engineered human pluripotent stem cells

Human induced pluripotent stem cells (iPSCs), reported in 2007 by Shinya Yamanaka, can be derived from blood or skin of any individual. They are unique because they can be grown indefinitely in the lab, and they have the capacity to produce any mature cell type - a property known as pluripotency. These attributes make iPSCs ideal candidates to replace animals in biological research. The rationale is that iPSC-derived heart cells, nerve cells, liver cells and other cell types can be used for many experiments instead of mice or other animals. Although the complexity of iPSC cultures is not yet approaching that of a whole animal, there is significant progress towards replacing animals in many areas of research.

Despite iPSCs being discovered over 10 years ago, there have been barriers to their wide-spread adoption in academia and industry, which have prevented them from achieving their potential as an alternative to animal use in research. The first barrier was acquisition of high-quality iPSC lines - this is now routine and 1000s of iPSC lines are available world-wide. The second barrier facing many labs is reliable and consistent production of mature specialised cell types (such as cardiac or nerve cells) from iPSCs. The inherent pluripotent nature of iPSCs means they are primed to produce all cell types in a dish. The protocols developed to corral and coax iPSCs to produce specific desired cell types, such as neurons, are complicated, lengthy and sensitive to minor perturbations. Furthermore, published "differentiation" protocols that work for particular iPSC lines are often not easily transferable to other iPSC lines. This has led to a significant level of frustration in the field, and has restricted iPSC technology to selected labs with the necessary expertise and resources to overcome the challenges of iPSC differentiation.

The main aim of this proposal is to completely remove this barrier and increase confidence in iPSC technology through the establishment of the Edinburgh Progenitor Cell Bank (EPB). We have established methods to differentiate iPSCs along cell lineage pathways and freeze them while in a progenitor cell state. A "progenitor cell" is a transition cell type that is half-way between an iPSC and a mature cell type. The frozen progenitor cells we produce are restricted and committed to produce a specific mature cell type after thawing, and they can be cultured by any laboratory and does not require any iPSC expertise.

The EPB will supply and support the use of lineage-committed neural progenitor cells for research purposes in academia and industry. Each batch of frozen progenitor cells undergo test-thaws and vigorous quality-control checks to ensure that recipient labs are supplied with high-quality functional cells. The EPB will be for the neuroscience community in the first instance, but can be expanded to other areas of biological research when other frozen iPSC-derived progenitor cells (eg. cardiac, liver) are included. The goal of the EPB is to provide diverse labs, particularly heavy animal users, with ready-to-use specialised human cells as a reliable and effective replacement for animal research subjects. Supplying progenitor cells in this way increases the capacity for use of this animal alternative by removing the need for labs to possess the skills and knowledge necessary to control stem cell differentiation.

Human induced pluripotent stem cells (iPSCs) can be differentiated into diverse cell types that can serve as models for most human tissues. They have significant potential to replace the use of animals in many areas of biological research. Although iPSC lines are readily available, their adoption is not widespread due to the substantial expertise needed for reliable and scalable production of mature cell types. The time and resources needed to establish iPSC technology and differentiation in a laboratory is a major barrier.

We have demonstrated that iPSC-derived dopaminergic progenitor cells can be cryopreserved and thawed to resume differentiation into mature neurons. Recipient labs with no stem cell expertise have successfully used our progenitors for experiments and publications. This model of working together has reduced animal use by our collaborators and increased confidence in iPSC technology.

Here we propose to increase the capacity and diversity of the cryopreserved neural progenitor cells we can offer through the creation of the Edinburgh Progenitor Cell Bank (EPB). In addition to dopaminergic progenitor cells, we have optimised the freezing and recovery of iPSC-derived cortical progenitor cells. We have also performed CRISPR/Cas9 genome editing in iPSCs to create isogenic collections of neural progenitor cells.

The second and third objectives of this proposal are to (a) target the safe-harbour AAVS1 locus in iPSCs with ageing-related fluorescence reporter genes and (b) convert this allelic series of reporter cell lines into banks of dopaminergic and cortical progenitor cells for distribution through the EPB.

We will initially focus on two types of neural progenitor cells produced from a bespoke collection of iPSC lines. However, future partnerships and further funding could significantly expand the breadth and depth of the cell bank, which would increase the range of progenitor cell types offered to the research community.