Comparison of culture media supplements identifies serum components in self-reported serum-free preparations.

BACKGROUND: Cell culture media are essential for cell expansion and many cells still depend on blood-derived supplements for optimal growth. From a regulatory perspective, these materials are ideally xeno-free, serum-free or even chemically defined. However, differences in composition and in performance are seldom clear from the terminology used in this field. METHODS: Therefore, we set out to investigate the presence of serum in seven serum-free media (SFM) and link that information to the performance and cost. We used fetal bovine serum and five human platelet lysate preparations (hPL) for comparison. RESULTS: Our data show significant differences in growth factor content between categories, but this did not correlate with mesenchymal stem cell (MSC) growth kinetics or maximal cell yield. Myeloperoxidase, glycocalicin and fibrinogen, derived from human leukocytes, platelets and plasma were detected at significant levels in 2 from 7 SFM. MSC cultured in these two SFM had a CD44-phenotype akin to hPL, essentially reclassifying them as hPL. Most SFM supported MSC expansion well, but some did not. In contract, all hPL supported MSC growth. The cost of SFM is significantly higher than hPL. CONCLUSIONS: We conclude that terminology regarding serum presence can be misleading. The cost-performance balance is best for hPL at this moment. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13287-025-04561-6.