iPSC cell culture

iPSCs and cell culture

Stem cells – including iPSCs – comprise an immortalised cell line that can be grown up and passaged indefinitely, certainly in theory.

Any cell line that undergoes culture in a dish for extended periods of time will accumulate mutations – which mirrors what is happening to cells in the human body.

Cell culture selects for those cells that “like” the conditions – i.e. the reagents and consumables – hence the cell population will inevitably change and ‘drift’ over time.  The rate of change of this drift – and how much the cells change – is dependent on a number of factors.

Factors affecting genomic drift in iPSCs

  • the stability of the cell line in the first place. For example, cancer cell lines tend to have completely ‘mangled’ / distorted (politely put) genomes – and hence change quickly
  • iPSCs derived from skin as opposed to blood have a UV mutation signature
  • poor culture technique and/or poor cryopreservation can amplify drift
  • how long the cells have been kept in culture and how many times they have been passaged the media/reagents can also influence the drift / genetic instability 

The direct consequence of this underlying tendency of iPSCs towards ‘drift’ means that in order to ensure researchers know what iPSCs they are working on, there is a clear and axiomatic need to test the quality and stability of the stem cells on a regular basis. This is the over-arching rationale driving the ISSCR Standards.

Note that one estimate suggests that approximately 30% of iPSC lines contain chromosome microdeletions or duplications, known as copy number variants, and hence are said to suffer from genomic abnormalities.