Efficient Purification of CD4+ Lymphocytes from Peripheral Blood Progenitor Cell Products Using Affinity Bead Acoustophoresis

Processing of peripheral blood progenitor cells (PBPC) for clinical transplantation or research applications aims to effectively isolate or deplete specific cell populations, utilizing primarily magnetic or fluorescence activated sorting methods. Here, we investigated the performance of microfluidic acoustophoresis for the separation of lymphocyte subsets from PBPC, and present a novel method for affinity-bead-mediated acoustic separation of cells which can otherwise not be acoustically discriminated. As the acoustic force on a particle depends on particle size, density and compressibility, targeting of cells by affinity specific beads will generate cell-bead complexes that exhibit distinct acoustic properties relative to nontargeted cells and are, thus, possible to isolate. To demonstrate this, PBPC samples (n = 22) were obtained from patients and healthy donors. Following density gradient centrifugation, cells were labeled with anti-CD4-coated magnetic beads (Dynal) and isolated by acoustophoresis and, for comparison, standard magnetic cell sorting technique in parallel. Targeted CD4+ lymphocytes were acoustically isolated with a mean (±SD) purity of 87 ± 12%, compared with 96 ± 3% for control magnetic sorting. Viability of sorted cells was 95 ± 4% (acoustic) and 97 ± 3% (magnetic), respectively. The mean acoustic separation efficiency of CD4+ lymphocytes to the target fraction was 65 ± 22%, compared with a mean CD4+ lymphocyte recovery of 56 ± 15% for magnetic sorting. Functional testing of targeted CD4+ lymphocytes demonstrated unimpaired mitogen-mediated proliferation capacity and cytokine production. Hematopoietic progenitor cell assays revealed a preserved colony forming ability of nontarget cells post sorting. We conclude that the acoustophoresis platform can be utilized to efficiently isolate bead-labeled CD4+ lymphocytes from PBPC samples in a continuous flow format, with preserved functional capacity of both target and nontarget cells. These results open up for simultaneous affinity-bead-mediated separation of multiple cell populations, something which is not possible with current standard magnetic cell separation technolog

Expression of Integrin A2 Receptor in Human Cord Blood Cd34+Cd38-Cd90+ Stem Cells Engrafting Long-Term in Nod/Scid-Il2rγ(C) Null Mice.

Human hematopoietic stem cells reside in the CD34+CD38-CD90+ population in cord blood and bone marrow. However, this cell fraction is heterogeneous, and the phenotype of the rare primitive stem cells remains poorly defined. We here report that primitive cord blood CD34+CD38-CD90+ stem cells, with the ability to reconstitute NOD/SCID-IL2Rγ(c) null mice long term, at 24 weeks after transplantation, can be prospectively isolated at an increased purity by using integrin α2 receptor as an additional stem cell marker. Using a limiting dilution transplantation assay, we found a highly significant enrichment of multilineage reconstituting stem cells in the CD34+CD38-CD90+ cell fraction expressing the integrin α2 receptor, with a frequency of 1/29 cells, as compared to a frequency of 1/157 in the corresponding integrin α2- cells. In line with this, long-term reconstituting stem cells within the cord blood CD34+CD38- cell population were significantly enriched in the integrin α2+ fraction, while stem cells and progenitors reconstituting short-term, at 8-12 weeks, were heterogeneous in integrin α2 expression. Global gene expression profiling revealed that the lineage-marker negative (Lin-) CD34+CD38-CD90+CD45RA- integrin α2+ cell population was molecularly distinct from the integrin α2- cell population and the more mature Lin-CD34+CD38-CD90-CD45RA- cell population. Our findings identify integrin α2 as a novel stem cell marker, which improves prospective isolation of the primitive human hematopoietic stem cells within the CD34+CD38-CD90+ cell population for experimental and therapeutic stem cell applications

Upregulation of Flt3 expression within the bone marrow Lin(-)Sca1(+)c-kit(+) stem cell compartment is accompanied by loss of self-renewal capacity

Flt3 has emerged as a potential regulator of hematopoietic stem cells (HSC). Sixty percent of cells in the mouse marrow Lin(-)Sca1(+)c-kit(+) HSC pool expressed flt3. Although single cell cloning showed comparable high proliferative, myeloid, B, and T cell potentials of Lin(-)Sca1(+)c-kit(+)flt3(+) and Lin(-)Sca1(+)c-kit(+)flt3(-) cells, only Lin(-)Sca1(+)c-kit(+)flt3(-) cells supported sustained multilineage reconstitution. In striking contrast, Lin(-)Sca1(+)c-kit(+)flt3(+) cells rapidly and efficiently reconstituted B and T lymphopoiesis, whereas myeloid reconstitution was exclusively short term. Unlike c-kit, activation of flt3 failed to support survival of HSC, whereas only flt3 mediated survival of Lin(-)Sca1(+)c-kit(+)flt3(+) reconstituting cells. Phenotypic and functional analysis support that Lin(-)Sca1(+)c-kit(+)flt3(+) cells are progenitors for the common lymphoid progenitor. Thus, upregulation of flt3 expression on Lin(-)Sca1(+)c-kit(+) HSC cells is accompanied by loss of self-renewal capacity but sustained lymphoid-restricted reconstitution potential

Involvement and functional impairment of the CD34(+)CD38(-)Thy-1(+) hematopoietic stem cell pool in myelodysplastic syndromes with trisomy 8.

Clonality studies of mature cells suggest that the primary transformation event in myelodysplastic syndrome (MDS) most frequently occurs in a myeloid-restricted progenitor, a hypothesis supported by recent studies of purified CD34(+)Thy1(+) hematopoietic stem cells (HSCs) in cases with trisomy 8 (+8). In contrast, we recently demonstrated that a lymphomyeloid HSC is the target for transformation in MDS cases with del(5q), potentially reflecting heterogeneity within MDS. However, since +8 is known to frequently be a late event in the MDS transformation process, it remained a possibility that CD34(+)CD38(-)Thy1(+) HSC disomic for chromosome 8 might be part of the MDS clone. In the present studies, although a variable fraction of CD34(+)CD38(-)Thy1(+) cells were disomic for chromosome 8, they did not possess normal HSC activity in long-term cultures and nonobese diabetic-severe combined immunodeficiency (NOD-SCID) mice. Mixing experiments with normal CD34(+)CD38(-) cells suggested that this HSC deficiency was intrinsic and not mediated by indirect mechanisms. Furthermore, investigation of 4 MDS cases with combined del(5q) and +8 demonstrated that the +8 aberration was always secondary to del(5q). Whereas del(5q) invariably occurs in CD34(+)CD38(-)Thy-1(+) HSCs, the secondary +8 event might frequently arise in progeny of MDS HSCs. Thus, CD34(+)CD38(-)Thy1(+) HSCs are invariably part of the MDS clone also in +8 patients, and little HSC activity can be recovered from the CD34(+) CD38(-)Thy1(+) HSC. Finally, in advanced cases of MDS, the MDS reconstituting activity is exclusively derived from the minor CD34(+)CD38(-) HSC population, demonstrating that MDS stem cells have a similar phenotype as normal HSCs, potentially complicating the development of autologous transplantation for MDS

The molecular signature of MDS stem cells supports a stem-cell origin of 5q - myelodysplastic syndromes

Global gene expression profiling of highly purified 5q-deleted CD34(+)CD38(-)Thy1(+) cells in 5q(-) myelodysplastic syndromes (MDSs) supported that they might originate from and outcompete normal CD34(+)CD38(-)Thy1(+) hematopoietic stem cells. Few but distinct differences in gene expression distinguished MDS and normal stem cells. Expression of BMI1, encoding a critical regulator of self-renewal, was up-regulated in 5q- stem cells. Whereas multiple previous MDS genetic screens failed to identify altered expression of the gene encoding the myeloid transcription factor CEBPA, stage-specific and extensive down-regulation of CEBPA was specifically observed in MDS progenitors. These studies establish the importance of molecular characterization of distinct stages of cancer stem and progenitor cells to enhance the resolution of stage-specific dysregulated gene expression