Cell culture medium composition

Cell culture medium is an essential components in ex vivo cell maintenance. Basic media provide all the necessary elements for growth and survival.
Culture media can be either of natural origin (biological fluids) or synthetic. Synthetic media generally consist of organic and inorganic nutrients (amino acids, proteins, lipids, salts, carbohydrates, vitamins, trace elements), non-nutrient factors (growth factors, hormones, binding proteins), dissolved O2 and CO2, enzymatic cofactors, as well as pH and osmolarity-regulating substances. Synthetic media growth supplements can be of animal, bacterial or human origin. Different synthetic media formulations are comprised depending on the purpose of the cell culture. The unfortunately still most common  culture supplement for primary human (stem) cell cultures is fetal bovine serum (FBS). Serum provides the medium with various growth and protection factors, hormones, binding proteins, protease inhibitors, antitoxins, trace elements and amino acids. However, the quality and quantity of serum compounds are highly inconsistent because of the high variability between batches and the use of serum is also associated with increased risk of contamination. Synthetic media can be grouped into four categories: 1) serum containing, 2) serum-free, 3) protein-free and 4) chemically defined media (known formulation with ultra-pure ingredients). Furthermore, because the animal/bacterial-derived growth supplements utilized in cell culture media manufacturing can lead to clinical complications, nowadays animal/xeno-free media formulations are also available especially for the cultivation of human stem cells.

In order to avoid the use of FBS in culture media, suitable alternatives that can replace the functions of serum must be used to ensure cell survival and growth. Human platelet lysate (hPL) is a growth factor-rich supplement isolated from human blood platelets usually with a freeze/thaw technique and considered a promising substitute for FBS in cell cultures. hPL has been shown to be more efficient in persevering the differentiation and immunosuppressive capacities of human mesenchymal stem cells (MSCs) than FBS.

MSC media are often supplied with antibiotics and antifungal compounds in order to prevent contaminations during culture. Antibiotics however, have been shown to have detrimental effects on the phenotype, proliferation, differentiation and metabolic activity of cultured MSCs.

Phenol red is also present in most commercially available media formulations as a pH indicator. However, phenol red can stimulate estrogen sensitive cells, and it can also interfere with the differentiation of MSCs in vitro.

A common cell culture strategy; cells, culture medium and supplements are combined in a culture vessel and during or at the end of the process cells or products produced by the cells can be harvested, whereas cellular waste products have to be eliminated

Ideal culture media should provide the MSCs with adequate amounts of nutrients in the correct time during their development, while preserving their physiological characteristics or guide their differentiation, therefore a suitable feeding strategy has to be applied to ensure optimal supply with all components at physiological concentration throughout the cultivation process.