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.