BRIEF REPORT Discarded plasma obtained after cord blood volume reduction as an alternative for fetal calf serum in mesenchymal stromal cells cultures Marija Vlaski-Lafarge, 1,2 Jean Chevaleyre, 1 Julie Cohen, 1 Zoran Ivanovic, 1,2 and Xavier Lafarge 1,2 BACKGROUND: Utilization of the fetal calf serum (FCS) carries a potential health risk and raises growing economic and ethical problems. Umbilical cord blood volume reduction, required for banking, provides clinical- grade umbilical cord blood plasma (UCBP) discarded as a waste. The aim of this study was to test whether serum derived from UCBP could replace FCS for the amplification of mesenchymal stromal cells (MSCs). STUDY DESIGN AND METHODS: To this end, the amplification of the MSCs and mesenchymal progenitors was estimated in the presence of serum derived from UCBP and its cytokine content was determined by cytometric bead array and enzyme-linked immunosorbent assay techniques. As a comparison, other sources of clinical-grade human serum were tested in parallel: serum derived from solvent/detergent–treated fresh-frozen plasma (S/D-FFP) and from platelet (PLT)- rich and PLT-poor umbilical plasma. RESULTS: Serum derived from UCBP-supplemented culture sustains identical amplification of MSCs and their progenitors as in the case of FCS addition. Furthermore, the assays reveal the presence in the serum derived from UCBP of cytokines influencing the properties of MSCs (basic fibroblast growth factor, transforming growth factor-β, vascular endothelial growth factor, and interleukin-8) or involved in the development of the myeloid lineage (thrombopoietin, erythropoietin, granulocyte–colony-stimulating factor, and granulocyte- macrophage–colony-stimulating factor). Also, our study indicates important differences between neonatal and adult-derived serum. Poor cytokine content in the S/D- FFP makes a less efficient replacement of FCS comparing to other human blood–derived supplements. CONCLUSION: Our work shows that the discarded human cord blood plasma from volume reduction is an easily obtainable and greatly available, xeno-free source of serum that is a highly efficient replacement of FCS in sustaining MSC growth. M esenchymal stromal cell (MSC) administra- tion has found broad clinical applications over the past few years. 1 Consequently, there is an increasing need in ameliorating culture conditions, particularly concerning a high level of biologic safety and the compatibility with the clinical grade. Histori- cally, MSC cultures were performed by supplementation with fetal calf serum (FCS), which allows a good amplifica- tion of these cells. This is a critical point, because introduc- ing the animal serums in the culture could be highly deleterious, resulting from different issues: biologic (risk of contaminations, presence of adverse molecules, important batch-to-batch variability), ethical (fetuses and animals suf- fering), and economical (global demand and supply dis- crepancy). 2 Hence, replacement of FCS is particularly challenging. Several humanized culture alternatives were proposed (autologous and allogeneic human serum, albu- min, thrombin- or collagen-activated PLT releasates, human PLT lysates, autologous marrow-derived plasma), and finally, umbilical cord blood plasma (UCBP). 3 ABBREVIATIONS: α-MEM = alpha minimum essential medium; b-FGF = basic fibroblast growth factor; CBA = cytometric bead array; MSC(s) = mesenchymal stromal cell(s); TPO = thrombopoietin; sHES-UCBP = hydroxyethyl starch-UCBP–derived serum; UCBP = umbilical cord blood plasma; UPPP = umbilical platelet-rich plasma; UPRP = umbilical platelet–rich plasma; VEGF = vascular endothelial growth factor. From the 1 Etablissement Français du Sang Nouvelle-Aquitaine, and the 2 INSERM U1035 University of Bordeaux, Bordeaux, France. Address reprint requests to: Xavier Lafarge, Etablissement fran- çais du sang Nouvelle Aquitaine, Place Amélie Raba Léon CS 21010, 33075 Bordeaux Cedex, France; Email: xavier.lafarge@efs.sante.fr. This study was supported by the Etablissement Français du Sang Nouvelle Aquitaine Bordeaux, regional research and develop- ment budget. Received for publication December 6, 2019; revision received April 24, 2020, and accepted April 25, 2020. doi:10.1111/trf.15920 © 2020 AABB TRANSFUSION 2020;9999;1–8 TRANSFUSION 1