One of the powers of iPSCs is that all of these strategies can also be applied to multiple different cell types, although it remains to be seen to what extent the results obtained in such isolated cell populations recapitulate the effects seen in complex human tissues. As differentiation protocols and three-dimensional cell culture techniques evolve, this can only improve our ability to use such systems to model many aspects of human disease. However, such cellular systems will always be limited in terms of assaying more complex system-level physiological and behavioural phenotypes, although xenograft systems may provide one means of achieving this in an in vivo context. One of the most important aspects of employing iPSC models of human disease is therefore in cellular and molecular phenotyping. Whilst for many diseases, such phenotypes will be known and predictable, for others this will require correlation of the normally complex physiological phenotypes seen in disease to the underlying molecular and cellular defects. Whilst challenging, this will also provide invaluable information about the pathogenic mechanisms leading to such diseases and novel avenues for therapeutic intervention.
