Multi-color immune-phenotyping of CD34 subsets reveals unexpected differences between various stem cell sources

Abstract

Flow cytometric routine CD34 analysis enumerates hematopoietic stem and progenitor cells irrespective of their subpopulations although this might predict engraftment dynamics and immune reconstitution. We established a multi-color CD34 assay containing CD133, CD45RA, CD10, CD38 and CD33. We examined PBSC, donor bone marrow (BMd) and BM of patients 1 year after allografting (BM1y) regarding their CD34 subset composition, which differed significantly amongst those materials: the early CD45RA − CD133 + CD38 low subpopulations were significantly more frequent in PBSC than in BMd, and very low in BM1y. Vice versa, clearly more committed CD34 stages prevailed in BM, particularly in BM1y where the proportion of multi-lymphoid and CD38 ++ B-lymphoid precursors was highest (mean 59%). CD33 was expressed at different intensity on CD45RA ± CD133 ± subsets allowing discrimination of earlier from more committed myeloid precursors. Compared with conventional CD34 + cell enumeration, the presented multicolor phenotyping is a qualitative approach defining different CD34 subtypes in any CD34 source. Its potential impact to predict engraftment kinetics and immune reconstitution has to be evaluated in future studies.

Lost in Transplantation? Unexpected shift from multipotent to late lymphomyeloid hematopoietic stem and progenitor cells in patients 1 year after hematopoietic stem cell transplantation

“…In this context, we recently showed that cocultivation with mesenchymal stem/stromal cells (MSCs) does not support HSC/MPP expansion or even their maintenance, but promotes the development of lymphomyeloid progenitors. from our in vitro studies and the novel data of Dmytrus et al, 13 it is tempting to hypothesize that MPPs in principle cannot self-renew, and irrespective of the environmental conditions divide asymmetrically to create LMPPs and EMPs. Alternatively, HSC/MPP-supporting niches might have been damaged in the patients before or following HSCT, and thus have lost their capability to efficiently support HSC/MPP expansion at least within the first year following HSCT.…”

“…In summary, Dmytrus et al 13 provide a first comprehensive and multiparameter phenotypic comparison of HSPC subsets before and after HSCT. Their results provide important new aspects for HSCT.…”

“…Now, Dmytrus et al 13 have comprehensively analyzed HSPC subpopulations in grafts before and in the BM of patients 1 year after HSCT. Interestingly, in comparison with the original grafts, the authors observed a significant decrease in more primitive and an increase in more mature HSPC frequencies after HSCT.…”

“…Related to the clinical situation, a number of novel aspects can be addressed: the HSPC composition in the grafts was compared with the situation in the BM 1 year after HSCT. 13 Although it will be ethically challenging, BM analyses at regular intervals might help to unravel HSPC repopulation dynamics following HSCT, and avoid a potential 'single time point bias'. The majority of patients whose BM was examined after allogeneic HSCT had received antithymocyte globulins (ATG) (15/21).…”

“…Of note and as previously discussed in detail, especially the inclusion of the cell surface marker CD133 resulted in the identification of unexpected lineage relationships, which were incompatible with prevailing models of human hematopoiesis, and let us propose a revised model of hematopoiesis ( Figure 1). 6,14,16 Now, by using a multicolor flow-cytometric panel comprising Abs against all these Ags, Dmytrus et al 13 performed immunephenotypic analyses of both HSC grafts before and the BM of patients 1 year after HSCT. By applying this panel, the authors were able to detect defined subsets of HSPCs, and compared their content and frequencies between PBSC and BM grafts, and between graft and patient BM samples after HSCT.…”