A novel protocol that allows short-term stem cell expansion of both committed and pluripotent hematopoietic progenitor cells suitable for clinical use

Cell division patterns in acute myeloid leukemia stem-like cells determine clinical course: a model to predict patient survival

Acute myeloid leukemia (AML) is a heterogeneous disease in which a variety of distinct genetic alterations might occur. Recent attempts to identify the leukemia stem-like cells (LSC) have also indicated heterogeneity of these cells. On the basis of mathematical modeling and computer simulations, we have provided evidence that proliferation and self-renewal rates of the LSC population have greater impact on the course of disease than proliferation and self-renewal rates of leukemia blast populations, that is, leukemia progenitor cells. The modeling approach has enabled us to estimate the LSC properties of 31 individuals with relapsed AML and to link them to patient survival. On the basis of the estimated LSC properties, the patients can be divided into two prognostic groups that differ significantly with respect to overall survival after first relapse. The results suggest that high LSC self-renewal and proliferation rates are indicators of poor prognosis. Nevertheless, high LSC self-renewal rate may partially compensate for slow LSC proliferation and vice versa. Thus, model-based interpretation of clinical data allows estimation of prognostic factors that cannot be measured directly. This may have clinical implications for designing treatment strategies.

Production of large numbers of plasmacytoid dendritic cells with functional activities from CD34(+) hematopoietic progenitor cells: use of interleukin-3

Plasmacytoid dendritic cells (pDC), a subset of dendritic cells characterized by a rapid and massive type-I interferon secretion through the Toll-like receptor pathway in response to viral infection, play important roles in the pathogenesis of several diseases, such as chronic viral infections (e.g., hepatitis C virus, human immunodeficiency virus), autoimmunity (e.g., psoriasis, systemic lupus erythematosus), and cancer. As pDC represent a rare cell type in the peripheral blood, the goal of this study was to develop a new method to efficiently generate large numbers of cells from a limited number of CD34(+) cord blood progenitors to provide a tool to resolve important questions about how pDC mediate tolerance, autoimmunity, and cancer. Human CD34(+) hematopoietic progenitor cells isolated from cord blood were cultured with a combination of Flt3-ligand (Flt3L), thrombopoietin (TPO), and one of the following cytokine: interleukin (IL)-3, interferon-β(IFN-β), or prostaglandin E2(PGE(2)). Cells obtained in the different culture conditions were analyzed for their phenotype and functional characteristics. The addition of IL-3 cooperates with Flt3L and TPO in the induction of pDC from CD34(+) hematopoietic progenitor cells. Indeed, Flt3L/TPO alone or supplemented with prostaglandin E2 or interferon-β produced smaller amounts of pDC from hematopoietic progenitor cells. In addition, pDC generated in Flt3L/TPO/IL-3 cultures exhibited morphological, immunohistochemical, and functional features of peripheral blood pDC. We showed that IL-3, in association with Flt3L and TPO, provides an advantageous tool for large-scale generation of pDC. This culture condition generated, starting from 2 × 10(5) CD34(+) cells, up to 2.6 × 10(6) pDC presenting features of blood pDC.

Ex-vivo expanded umbilical cord blood stem cells retain capacity for myocardial regeneration

BACKGROUND

Umbilical cord blood (UCB) is a source of human hematopoietic precursor cells (HPCs), a stem cell (SC) type that has been used in several trials for myocardial repair. A certain minimal number of cells is required for measurable regeneration and a major challenge of SC-based regenerative therapy constitutes ex-vivo expansion of the primitive cell compartment. The aim of this study was to investigate the ex-vivo expansion potential of UCB-derived HPCs and the ability of these expanded cells to migrate to the site of damage and improve ventricular function in a rodent model of myocardial infarction (MI).

METHODS AND RESULTS

UCB-derived HPCs, defined by coexpression of CD133 and CD34, were expanded using various cytokine combinations. MI was induced by left anterior descending artery ligation in nude rats. Cells were injected intravenously 2 days after infarction. The combination of SC factor, thrombopoietin, flt3-ligand and interleukin-6 was found to be the most effective for inducing proliferation of HPCs. The migratory capacity of expanded HPCs was similar to that of non-expanded HPCs and improvement of ejection fraction was significant in both groups, with a relative increase of >60%.

CONCLUSIONS

UCB-derived HPCs can be reproducibly expanded ex-vivo and retain their potential to improve cardiac function post-MI. (Circ J 2010; 74: 188 - 194).

Protocols for hematopoietic stem cell expansion from umbilical cord blood

The reconstitution of adult stem cells may be a promising source for the regeneration of damaged tissues and for the reconstitution of organ dysfunction. However, there are two major limitations to the use of such cells: they are rare, and only a few types exist that can easily be isolated without harming the patient. The best studied and most widely used stem cells are of the hematopoietic lineage. Pioneering work on hematopoietic stem cell (HSC) transplantation was done in the early 1970s by ED. Thomas and colleagues. Since then HSCs have been used in allogenic and autologous transplantation settings to reconstitute blood formation after high-dose chemotherapy for various blood disorders. The cells can be easily harvested from donors, but the cell number is limited, especially when the HSCs originate from umbilical cord blood (UCB). It would be desirable to set up an ex vivo strategy to expand HSCs in order to overcome the cell dose limit, whereby the expansion would favor cell proliferation over cell differentiation. This review provides an overview of the various existing HSC expansion strategies-focusing particularly on stem cells derived from UCB-of the parameters that might affect the outcome, and of the difficulties that may occur when trying to expand such cells.

Inverse Tendency between Ex Vivo Expansion Potential of Hematopoietic Progenitors and Time to Engraftment after Hematopoietic Stem Cell Transplantation

BACKGROUND

The CD34(+) cell dose and infused number of committed progenitor cells in transplantation are important factors in hematologic engraftment. However, the relationship between expansion potential of progenitor cells and hematologic engraftment remains controversial. We evaluated whether expansion potential of progenitor cells is a predictive factor of post-transplantation hematologic engraftment.

METHODS

Mononuclear cells isolated from mobilized peripheral blood and bone marrow were cultured with cytokine cocktail for 7 days. Progenitor cells and committed progenitors were analyzed using stem cell markers (CD34 and CD133) and lineage specific markers. Hematologic engraftment was defined as neutrophil counts over 500/microL and platelet counts over 20,000/microL without transfusion. Acute and chronic graft-versus-host disease (GVHD) were investigated.

RESULTS

There was inverse tendency between the number and fold expansion of progenitor cells or committed (granulocytic or megakaryocytic) progenitors and time to engraftment. Especially, fold expansion of CD34(+)/CD33(+) cells was significantly correlated with time to neutrophil engraftment in bone marrow transplantation (r=-0.56, P=0.04). The infused number and fold expansion of lymphoid progenitors were not related to the occurrence of acute or chronic GVHD.

CONCLUSIONS

We could not prove that expansion potential of progenitor cells and committed progenitor cells is correlated to hematologic engraftment although there is a correlation between CD34(+)/ CD33(+) cells and time to neutrophil engraftment. But, a further study on the value of expansion potential is required because there is an inverse tendency.

Pre-clinical development of cord blood-derived progenitor cell graft expanded ex vivo with cytokines and the polyamine copper chelator tetraethylenepentamine

BACKGROUND

We have previously demonstrated that the copper chelator tetraethylenepentamine (TEPA) enables preferential expansion of early hematopoietic progenitor cells (CD34+CD38-, CD34+CD38-Lin-) in human umbilical cord blood (CB)-derived CD34+ cell cultures. This study extends our previous findings that copper chelation can modulate the balance between self-renewal and differentiation of hematopoietic progenitor cells.

METHODS

In the present study we established a clinically applicative protocol for large-scale ex vivo expansion of CB-derived progenitors. Briefly, CD133+ cells, purified from CB using Miltenyi Biotec's (Bergisch Gladbach, Germany) CliniMACS separation device and the anti-CD133 reagent, were cultured for 3 weeks in a clinical-grade closed culture bag system, using the chelator-based technology in combination with early-acting cytokines (SCF, thrombopoietin, IL-6 and FLT-3 ligand). This protocol was evaluated using frozen units derived from accredited cord blood banks.

RESULTS

Following 3 weeks of expansion under large-scale culture conditions that were suitable for clinical manufacturing, the median output value of CD34+ cells increase by 89-fold, CD34+CD38- increase by 30-fold and CFU cells (CFUc) by 172-fold over the input value. Transplantation into sublethally irradiated non-obese diabetic (NOD/SCID) mice indicated that the engraftment potential of the ex vivo expanded CD133+ cells was significantly superior to that of unexpanded cells: 60+/-5.5% vs. 21+/-3.5% CD45+ cells, P=0.001, and 11+/-1.8% vs. 4+/-0.68% CD45+CD34+ cells, P=0.012, n=32, respectively.

DISCUSSION

Based on these large-scale experiments, the chelator-based ex vivo expansion technology is currently being tested in a phase 1 clinical trial in patients undergoing CB transplantation for hematological malignancies.

Evaluation of ex vivo expansion and engraftment in NOD-SCID mice of umbilical cord blood CD34+ cells using the DIDECO "Pluricell System"

The Dideco "Pluricell System" is a commercially available closed device composed of an expansion chamber and a kit of certified reagents that allow haematopoietic stem cell expansion. We have expanded seven umbilical cord blood (UCB) samples following the manufacturer's instructions; two groups of irradiated NOD-SCID mice have been transplanted with expanded and nonexpanded cells from the same UCB, and bone marrow was analysed for the presence of human cells. Average UCB volume was 61.6+/-8.8 ml; mean nucleated cell content was 1090.5+/-189.9 x 10(6). Percentage and number of CD34+ cells were 0.37+/-0.13% and 3.9+/-1.2 x 10(6). After separation, CD34+ cell purity was 82+/-11%. Mean number of inoculated cells was 760 000; mean NC and CD34+ fold expansion at 12 days was 230.4+/-91.5 and 21.0+/-11.9. Both groups of mice showed successful engraftment: the percentage of human cells was higher in the group receiving expanded cells (3.4+/-2.01%) compared to the group receiving nonexpanded cells (1.5+/-0.66%) (P<0.00018, Mann-Whitney test). The cell population obtained after 12 days expansion consisted mainly of myeloid and megakaryocytic progenitors. The CD34+ antigen reached the maximum expression level at day 12 (7.5+/-2.0%). Analysis of lineage-markers for human myelomonocytic, megakaryocytic, B, T, CD34 and erythroid cells, gave evidence that all the lineages were represented in the marrow of transplanted mice.

MUTZ-3, a human cell line model for the cytokine-induced differentiation of dendritic cells from CD34+ precursors

Many human myeloid leukemia-derived cell lines possess the ability to acquire a dendritic cell (DC) phenotype. However, cytokine responsiveness is generally poor, requiring direct manipulation of intracellular signaling mechanisms for differentiation. In contrast, the CD34+ human acute myeloid leukemia cell line MUTZ-3 responds to granulocyte macrophage- colony-stimulating factor (GM-CSF), interleukin 4 (IL-4), and tumor necrosis factor alpha (TNFalpha), cytokines known to be pivotal both in vivo and in vitro for DC generation from monocytes and CD34+ stem cells. In all respects, MUTZ-3 cells behave as the immortalized equivalent of CD34+ DC precursors. Upon stimulation with specific cytokine cocktails, they acquire a phenotype consistent with either interstitial- or Langerhans-like DCs and upon maturation (mDC), express CD83. MUTZ-3 DC display the full range of functional antigen processing and presentation pathways. These findings demonstrate the unique suitability of MUTZ-3 cells as an unlimited source of CD34+ DC progenitors for the study of cytokine-induced DC differentiation.