Evaluation of committed and primitive cord blood progenitors after expansion on adipose stromal cells

Umbilical cord blood mononuclear fraction is a valuable source of hematopoietic stem and progenitor cells (CB HSPCs). The rarity of this population is a serious limitation of its application in cell therapy. Ex vivo expansion enables to significantly amplify the number of hematopoietic precursors of different commitment. Here, we expand CB MNCs in co-culture with human adipose tissue-derived stromal cells (ASCs) to enrich HSPCs and describe phenotypic features of newly formed hematopoietic populations. The CD34+-HSPCs demonstrated 6-fold enrichment with 9000 CFUs per 50 × 103 HSPCs on average. A part of the floating HSPCs were bearing lineage markers, while others were primitive precursors (CD133−/CD34+). Among ASC-associated HSPCs, two subsets of cord blood-borne cells were revealed: СD90+/СD45− and СD90+/СD45+. The proportion of CD3+/CD8+ and NK-T as well as CD25+ and HLA-DR+ Т cells among СD90+/СD45− cells was significantly higher compared to MNCs and floating HSPCs. More than 80% of CD45+/СD90+ HSPCs were identified as late primitive precursors (CD133−/CD34+). Thus, CB MNC expansion in the presence of ASCs provides the generation of both lineage committed lymphoid progenitors and CD34+/CD133− primitive HSPCs. Substantially enriched with primitive precursors, ASC-associated HSPCs could be considered as a perspective tool for a long-term restoration of hematopoiesis in various hematologic disorders.