The proteome signature of cord blood plasma with high hematopoietic stem and progenitor cell count

Hematopoietic stem and progenitor cells (HSPC) from umbilical cord blood (UCB) are used for transplantation to treat blood disorders. Methods to estimate the HSPC count in umbilical cord blood, and thereby identify high-value blood units, are time-consuming and costly. Recent studies indicate that the UCB plasma protein composition relates to the HSPC count. We compared the plasma proteome of UCB with high vs low HSPC cell count (> 115 x 10(6) vs < 51 x 10(6) CD34(+) cells l(-1)) by using a combination of global untargeted MS quantitative proteomics and targeted proximity extension assay (PEA) proteomics. For the MS platform, 96 proteins differed significantly between the CD34(+) groups, and out of these, 44 proteins showed more than a two-fold difference. Seven pathways were enriched in high CD34(+) samples, including pathways relating to platelets, coagulation, and lipid transport. For the PEA platform, 61 proteins were differentially abundant, and among these 7 proteins showed more than a two-fold difference between groups. In the PEA data, a high CD34(+) cell count was associated with a protein hub with functions in platelet degranulation. We conclude that the HSPC count is related to the UCB plasma proteome, but that further studies are needed to discern if these findings reflect causal relationships.