Fetal Bovine and Calf Serums Differ in Their Contents of Endocannabinoids, Unsaturated Fatty Acids, Monoacyl-Glycerols, N-Acyl-Ethanolamines, Oxylipins and Cytokines.

Cell culture relies heavily on serum supplementation, but serum composition makes it difficult to ensure reproducibility and consistency of experimental results. Consequently, research groups must test multiple batches to ensure the functionality and reproducibility of their models of their models. The commonly used serums are fetal bovine serums (FBS) and calf serums (CS), which have been recognized as crucial in modulating cellular processes. While having been utilized for decades, little information is known about their respective lipid mediator contents. This study explored the presence of several major bioactive lipids involved in the regulation of inflammation, metabolism, differentiation, immune response, neuroprotection, and vascular homeostasis. These included polyunsaturated fatty acids, monoacylglycerols (MAGs), N-acyl-ethanolamines (NAEs), and oxylipins. As compared to FBS, CS samples were enriched in most fatty acids except for arachidonic acid. The levels of the endocannabinoids 2-arachidonoyl-glycerol (2-AG) and N-arachidonoyl-ethanolamine (AEA) followed the same pattern as arachidonic acid. On the other hand, most lipoxygenase-derived mediators, including, leukotriene B4, showed higher abundance in CS. Accordingly, CS serum activated the random migration of human neutrophils to a much greater extent than FBS, an effect attenuated by the BLT1 receptor antagonist CP 105,696. These findings highlight how bovine serum lipid composition is a major determinant modulating cellular responses and might thus impact experimental reproducibility. The data presented herein will help key insights beyond conventional cell culture optimization and might represent key features to consider when planning in cellulo experiments across numerous fields, also beyond immunology.