Everyone who is entering the field of clinical expansion of mesenchymal stromal cells (MSC) facing the problem: available reliable supply of serum for cell culture. As number of MSC clinical trials is increasing with years, the global demand for serum is growing dramatically. Taking into account prevalence of using serum for clinical MSC culture worldwide and “peak serum phenomenon”, it becomes clear that this “serum model” is not going to work in the future. There will be not enough supplies of clinical grade serum (animal or human), serum-based MSC manufacturing model will be unsustainable and, eventually, obsolete. It is also clear to me that serum alternatives or completely synthetic media should be tested early during product development. New serum-free formulations may have advantages over serum or alternatives, but not many products available to test, since industry in its early days. That’s why every good study on this topic is a worth our attention! Today I’ve picked one of such studies, recently published in Cytotherapy.
The authors tested hypothesis of finding one “ideal” serum-free media (SFM) for different MSC cultures. They tested 6 SFM on 7 different MSC lines in 3 different culture methods. Tested SFM:
- StemPro MSC SFM Xeno-free (Life Technologies/ Thermo)
- MSC Nutristem XF (Biological Industries)
- MesenCult-XF (StemCell Technologies)
- StemXVivo SFM (R&D Systems)
- 2 in-house SFM fromulations (Biotechnology Processing Institute)
Human MSC cell lines were obtained from:
- CTI Biotech
Tissue sources of these lines were:
- umbilical cord matrix
- umbilical cord blood
- adult bone marrow
- fetal bone marrow
- adipose tissue
Cell culture methods:
- 3D static microcarrier
- 3D agitated microcarrier
Now, I’d like to summarize findings from this study:
- In monolayer culture MSC density/ proliferation did not correlate between SFM and serum+.
- In terms of MSC density, most SFM outperformed serum+.
- There was no single SFM optimal for growth of all tested MSC lines.
- Cell density/ expansion differ significantly between different SFM.
- The optimal SFM differ between monolayer and microcarrier-based cultures.
- There was no correlation in MSC growth between static and agitated microcarrier cultures.
- There was a poor correlation between MSC growth in monolayer and microcarrier serum+ culture.
- Some of MSC lines were slowly growing and none of SFM supported them on static microcarriers.
- Cell attachment onto microcarriers may not predict good proliferation in SFM.
Take home messages from this study:
Optimize SFM for your particular MSC type, method of expansion, other culture supplements, coating matrices and application! I couldn’t emphasize this more! There is nothing more important for MSC developer than cell culture optimization! Find your own “magic formula”! It worth your time and money! Do it early on – before even starting Phase 1 of trial. Try all available options – commercial/ in-house-made SFM formulations and serum alternatives. Use lower (1-2%) and high (5-20%) concentration of serum as controls. Don’t rely on publications, don’t make assumptions – test it on your own! Your adipose/ marrow MSC could grow very differently from other reported adipose/marrow MSC in the same culture conditions.