Cellular and molecular profiling of primitive HSC subsets in umbilical cord blood samples: Implications for cellular therapy

Background: Traditionally, hematopoietic stem/ progenitor cells (HSPCs) from bone-marrow, peripheral blood and cord blood donors are used to cure obstinate blood disorders and to influence tolerance in graft-versus-host disease. The most primitive HSCs in mammals comprise the well characterized CD34 and the rare disused CD34 HSCs subsets. However, the defined analysis of the molecular nature of human CD34 and their relation to CD34 HSCs fractions has been held up by the lack of specific markers. Objectives: This study was intended to provide a thorough analysis using phenotypic, functional, and systemic approaches to decipher the cellular and the molecular signature of different HSPCs components, based on a comparative study combining both surface phenotypic markers and functional ALDH activity on human cord blood samples. Materials & Methods: Different HPSCs subsets were sorted from UCB and analyzed by flow cytometry, real time PCR, and proteomic techniques and their multi-differential capacity was assessed in vitro by colony forming unit assay Results: Evaluation of different HPSCs fractions revealed that CD34LinCD38ALDH and CD34LinCD38ALDHare the most primitive HPSCs populations as illustrated by their in vitro proliferation potentials by colony forming units and stemness related gene expression. Moreover, protein profiling performed on few samples showed that there is a high degree of similarities in the total number or resolved spots in both CD34 and CD3 gels indicating that perhaps CD34are also HSCs Conclusions: Our study confirmed that HPSCs is a heterogeneous population. The simultaneous expression of surface markers and ALDH activity indicated that the neglected LinCD34CD38ALDH HPSCs compartment included primitive HSCs and displayed similar functional and molecular characteristics to their counterpart LinCD34CD38ALDH. The common protein spots identified on HSCs subsets will eventually help in their selection for scientific and clinical applications.