Ex vivo expansion of G-CSF-mobilized peripheral blood CD133+ progenitor cells on coculture with human stromal cells

Extracellular vesicle miR-7977 is involved in hematopoietic dysfunction of mesenchymal stromal cells via poly(rC) binding protein 1 reduction in myeloid neoplasms

The failure of normal hematopoiesis is observed in myeloid neoplasms. However, the precise mechanisms governing the replacement of normal hematopoietic stem cells in their niche by myeloid neoplasm stem cells have not yet been clarified. Primary acute myeloid leukemia and myelodysplastic syndrome cells induced aberrant expression of multiple hematopoietic factors including Jagged-1, stem cell factor and angiopoietin-1 in mesenchymal stem cells even in non-contact conditions, and this abnormality was reverted by extracellular vesicle inhibition. Importantly, the transfer of myeloid neoplasm-derived extracellular vesicles reduced the hematopoietic supportive capacity of mesenchymal stem cells. Analysis of extracellular vesicle microRNA indicated that several species, including miR-7977 from acute myeloid leukemia cells, were higher than those from normal CD34(+)cells. Remarkably, the copy number of miR-7977 in bone marrow interstitial fluid was elevated not only in acute myeloid leukemia, but also in myelodysplastic syndrome, as compared with lymphoma without bone marrow localization. The transfection of the miR-7977 mimic reduced the expression of the posttranscriptional regulator, poly(rC) binding protein 1, in mesenchymal stem cells. Moreover, the miR-7977 mimic induced aberrant reduction of hematopoietic growth factors in mesenchymal stem cells, resulting in decreased hematopoietic-supporting capacity of bone marrow CD34(+)cells. Furthermore, the reduction of hematopoietic growth factors including Jagged-1, stem cell factor and angiopoietin-1 were reverted by target protection of poly(rC) binding protein 1, suggesting that poly(rC) binding protein 1 could be involved in the stabilization of several growth factors. Thus, miR-7977 in extracellular vesicles may be a critical factor that induces failure of normal hematopoiesis via poly(rC) binding protein 1 suppression.

Phenotypic, Morphological and Adhesive Differences of Human Hematopoietic Progenitor Cells Cultured on Murine versus Human Mesenchymal Stromal Cells

Xenogenic transplantation models have been developed to study human hematopoiesis in immunocompromised murine recipients. They still have limitations and therefore it is important to delineate all players within the bone marrow that could account for species-specific differences. Here, we evaluated the proliferative capacity, morphological and physical characteristics of human CD34⁺ hematopoietic stem and progenitor cells (HSPCs) after co-culture on murine or human bone marrow-derived mesenchymal stromal cells (MSCs). After seven days, human CD34⁺CD133^– HSPCs expanded to similar extents on both feeder layers while cellular subsets comprising primitive CD34⁺CD133⁺ and CD133⁺CD34^– phenotypes are reduced fivefold on murine MSCs. The number of migrating HSPCs was also reduced on murine cells suggesting that MSC adhesion influences cellular polarization of HSPC. We used atomic force microscopy-based single-cell force spectroscopy to quantify their adhesive interactions. We found threefold higher detachment forces of human HSPCs from murine MSCs compared to human ones. This difference is related to the N-cadherin expression level on murine MSCs since its knockdown abolished their differential adhesion properties with human HSPCs. Our observations highlight phenotypic, morphological and adhesive differences of human HSPCs when cultured on murine or human MSCs, which raise some caution in data interpretation when xenogenic transplantation models are used.

Human bone marrow stromal cells simultaneously support B and T/NK lineage development from human haematopoietic progenitors: a principal role for flt3 ligand in lymphopoiesis

The regulation of human early lymphopoiesis remains unclear. B- and T-lineage cells cannot develop simultaneously with conventional stromal cultures. Here we show that telomerized human bone marrow stromal cells supported simultaneous generation of CD19(+) CD34(lo/-) CD10(+) cyCD79a(+) CD20(+/-) VpreB(-) pro-B cells and CD7(+) CD34(+) CD45RA(+) CD56(-) cyCD3(-) early T/Natural Killer (NK) cell precursors from human haematopoietic progenitors, and the generation of both lymphoid precursors was promoted by flt3 ligand (flt3L). On the other hand, stem cell factor or thrombopoietin had little or no effect when used alone. However, both acted synergistically with flt3L to augment the generation of both lymphoid precursors. Characteristics of these lymphoid precursors were evaluated by gene expression profiles, rearrangements of IgH genes, or replating assays. Similar findings were observed with primary human bone marrow stromal cells. Notably, these two lymphoid-lineage precursors were generated without direct contact with stromal cells, indicating that early B and T/NK development can occur, at least in part, by stromal cell-derived humoral factors. In serum-free cultures, flt3L elicited similar effects and appeared particularly important for B cell development. The findings of this study identified the potential of human bone marrow stromal cells to support human early B and T lymphopoiesis and a principal role for flt3L during early lymphopoiesis.

Irradiated Mesenchymal Stem Cells improve the ex vivo expansion of Hematopoietic Progenitors by partly mimicking the bone marrow endosteal environment

Mesenchymal Stem Cells (MSCs) regulate the growth and differentiation of Hematopoietic Progenitor cells (HPCs) through the release of soluble factors or through their differentiation into osteoblasts. We recently demonstrated that expansion of megakaryocyte (MK) progenitors ex vivo had reached a plateau when CD34(+) cells were grown with two optimized cytokine cocktails developed for the growth of MK. Hence, we sought to determine whether co-culture of CD34(+) cells with Bone Marrow (BM) MSCs could further increase the expansion of myeloid and MK progenitors. First, we tested the impact of cell-cell contact and pre-irradiation treatment of the MSCs to identify the condition that best supports HPC expansion. This screen revealed that HPC expansions were generally greater in the non-contact conditions, and that pre-irradiation of the MSCs appeared to be of added benefits. Improved expansion of both myeloid and MK progenitors in co-culture with irradiated MSCs without contact was subsequently confirmed. Next, cytokine array profiling was carried out to investigate why irradiation promoted progenitor expansion. This revealed that the levels of as many as 33 factors were potentially altered. ELISA confirmed the significant up regulation of NT-3 and IGFBP-2. Since, these factors are known to be released by and important for osteogenic and endothelial cells, we investigated and confirmed that irradiation of MSCs induced their rapid differentiation into osteogenic-like cells, but not into endothelial-like cells. Supporting this finding, expansions of myeloid and MK progenitors were increased when CD34(+) cells were co-culture with MSCs-derived osteoblasts. Altogether, these results indicate that the improved expansion of HPCs obtained with irradiated MSCs is due in part to their differentiation into osteoblast-like cells, thereby recreating an endosteal-like environment that provides improved support for HPCs expansion.

Biological activities and molecular interactions of the C-terminal residue of thrombospondin-4, an epitome of acidic amphipathic peptides

C21, the C-terminal residue of thrombospondin-4 (TSP-4), was identified as a peptide growth factor during an investigation concerning erythropoietin-dependent, erythroid stimulating factors of endothelial origin. It is active in cultures of several human hematopoietic stem cells, skin fibroblasts and kidney epithelial cells and stimulates red cell formation in anemic mice. A method of affinity chromatography in the presence of high concentrations of Triton X-100, previously developed for identifying proteins associated with the TSP-1 receptor CD47, was utilized for the detection of C21 binding molecules and their detergent-resistant, associated partners. These experiments helped to delineate two different mechanisms of C21 action, which are compatible with its cell proliferating activity. As a cell matrix peptide, C21 binds to the osteopontin receptor CD44 and could act as an osteopontin antagonist, preventing the inhibition of primitive hematopoietic stem cell proliferation. TSP-1, another matrix protein, binds to C21 and could indirectly act as an antagonist, by shunting C21-CD44 interactions. The second mechanism is a direct effect of C21 on cell proliferation. The extremely rapid internalization and nuclear localization of the peptide could be explained by CD44-mediated internalization, followed by a microtubule-mediated transport towards the nucleus, or, eventually, direct membrane insertion. These alternative hypotheses are supported by previously observed membrane insertion of similar synthetic and viral acidic amphipathic peptides, the presence of microtubule-associated protein 1B (MAP1B) and dynactin in the triton-soluble complexes associated with C21 and the presence in such complexes of dual compartment proteins for nuclei and plasma membranes, such as MAP1B, AHNAK and CD44.

Osteopontin and the C-terminal peptide of thrombospondin-4 compete for CD44 binding and have opposite effects on CD133+ cell colony formation

Background

C21, the C-terminal peptide of thrombospondin-4, has growth promoting activity and was discovered as one of several erythropoietin-dependent endothelial proteins. C21 stimulates red cell formation in anemic mice and is a growth factor for CD34+ and CD36+ hematopoietic cells, skin fibroblasts and kidney epithelial cells. ROD1 has been identified as an intracellular mediator. Nothing is known about the existence of putative C21 receptors on plasma membranes of target cells.

Findings

We analyzed the nature of C21-binding proteins in cell lysates of skin fibroblasts using C21 affinity columns. The membrane receptor CD44 was identified as C21-binding protein by mass spectrometry. We were unable to demonstrate any direct involvement of CD44 on cell growth or the effect of C21 on cell proliferation. A soluble form of CD44 was synthesized in insect cells and purified from culture supernatants with a combination of PVDF filtration in the presence of ammonium sulphate and HPLC. Both osteopontin and hyaluronic acid competitively displaced Biotin-C21 binding to CD44. In a colony-forming assay using primitive CD133+ hematopoietic stem cells from cord blood, osteopontin and C21 had opposite effects and C21 reduced the inhibitory action of osteopontin.

Conclusion

CD44 is a C21-binding membrane protein. We could not demonstrate an involvement of CD44 in the proliferative action of C21. Nevertheless, based on the antagonism of C21 and osteopontin in hematopoietic precursors, we speculate that C21 could indirectly have a major impact on hematopoietic stem cell proliferation, by hindering osteopontin membrane binding at the level of the bone marrow niche.

Effects of encapsulated rabbit mesenchymal stem cells on ex vivo expansion of human umbilical cord blood hematopoietic stem/progenitor cells

The expansion of umbilical cord blood mononuclear cells (UCB MNCs) was investigated in a novel co-culture system by means of encapsulation of rabbit bone marrow (BM) mesenchymal stem cells (MSCs) in alginate beads (Alg beads). Three kinds of media were applied and the experiments lasted for 7 days. The total nucleated cell density was measured every 24 h. Flow cytometric assay for CD34(+) cells and methylcellulose colony assays were carried out at 0, 72 and 168 h. It was found that the encapsulated MSCs illustrated remarkable effects on UCB MNCs expansion regardless of whether serum is present in culture media or not. At the end of 168 h co-culture, the total nucleated cell number was multiplied by 15 +/- 2.9 times, and CD34(+) cells 5.3 +/- 0.3 times and colony-forming units in culture (CFU-Cs) 5.6 +/- 1.2 times in the serum-free media supplemented with conventional dose of cytokines, which was very similar to the results in the containing 20% serum media. While in the control, i.e. MNC expansion without encapsulated MSCs, however, total nucleated cells density changed mildly, CD34(+) cells and CFU-Cs showed little effective expansion. It is demonstrated that the encapsulated stromal cells can support the expansion of UCB MNCs effectively under the experimental condition.

Placental/umbilical cord blood-derived mesenchymal stem cell-like stromal cells support hematopoietic recovery of X-irradiated human CD34+ cells

AIMS

The potential of human mesenchymal stem cell-like stroma prepared from placental/umbilical cord blood for hematopoietic regeneration by X-irradiated hematopoietic stem cells is herein assessed.

MAIN METHODS

Placental/umbilical cord blood-derived mesenchymal stem cell-like stromal cells were applied to a regenerative ex vivo expansion of X-irradiated human CD34(+) cells in a serum-free liquid culture supplemented with a combination of interleukine-3 plus stem cell factor plus thrombopoietin.

KEY FINDINGS

The total number of cells and of lineage-committed myeloid hematopoietic progenitor cells generated in the co-culture of both non-irradiated and X-irradiated cells with stromal cells was significantly higher than those in the stroma-free culture. In addition, the number of CD34(+) cells and CD34(+)/CD38(-) cells, immature hematopoietic stem/progenitor cells also increased more than the stroma-free culture. The stromal cells produced various types of cytokines, although there was little difference between the co-cultures of non-irradiated and X-irradiated cells with stromal cells. Furthermore, when X-irradiated cells came in contact with stromal cells for 16 h before cytokine stimulation, a similar degree of hematopoiesis was observed, thus suggesting the critical role of cell-to-cell interaction.

SIGNIFICANCE

The present results showed the potential efficacy of human mesenchymal stem cell-like stroma for hematopoietic regeneration from irradiated hematopoietic stem/progenitor cells.

Maternal plasma or human serum albumin in wash buffer enhances enrichment and ex vivo expansion of human umbilical cord blood CD34+ cells

Umbilical cord blood is a valuable source of haemopoietic stem/progenitor cells (HSC) for transplantation. This study explored the effect of maternal plasma/human serum albumin (HSA) in the purification and culture conditions of CD34+ cells derived from human umbilical cord blood. During CD34+ cell enrichment, including maternal plasma or HSA instead of fetal bovine serum (FBS) in the wash buffer, significantly increased the purity and the fold expansion of CD34+ cells. The increase in fold expansion of CD34+ cells was independent of CD34+ cell purity before expansion. With FBS, the mean fold expansion of CD34+ cells and total nucleated cells on day 7 was 9.7 +/- 5.5 and 39.7 +/- 13.7 respectively. The use of maternal plasma increased the mean fold expansion of CD34+ cells and total nucleated cells on day 7 to 28.2 +/- 6.7 and 71.5 +/- 15.4 respectively. When HSA was added to wash buffer, the mean fold expansion of CD34+ cells and total nucleated cells were 30.4 +/- 10.5 and 83.5 +/- 24.8 respectively. No statistical significance was found between using HSA and maternal plasma on total cell and CD34+ cell expansion. We propose that HSA in maternal plasma was responsible for the positive effect on CD34+ cell enrichment and expansion.

Neural Network Analysis of Ex-vivo Expansion of Hematopoietic Stem Cells

The shortage of hematopoietic stem cells (HSCs) greatly limits their widespread clinical applications. Few studies however, investigated the relationship between the cellular expansion and the influencing factors although wide variety results of the ex-vivo expansion of HSCs existed in literature. Here, a back-propagation (BP) neural network model was employed to evaluate the ex-vivo expansions of nuclear cells (NCs), CD34(+) cells, and colony-forming units (CFU-Cs), where the output was the cellular expansion folds and the inputs include inoculated density, cytokines, resources, serum, stroma, culture time, and bioreactor types. Around 124, 86, and 90 samples were used to train the neural network for the expansion evaluations of NCs, CD34(+ )cells, and CFU-Cs, respectively, while 17, 14, and 10 samples were applied to predict respectively. The results show that for the training of network, the interval accuracy of the expansion folds for the different cells is 85.5, 86.1, and 86.7%, respectively, while the truth-value accuracy is still up to 59.7, 50.0, and 62.2%, respectively within a relative error (RE) of +/-20%. For the prediction of network, the interval accuracy can be up to 82.4, 71.4, and 70%, respectively, while the truth-value accuracy is only 29.4, 14.3, and 50.0%, respectively (RE = +/-20%). Moreover, six verification experiments were carried out based on our interval predicted values and the results proved that the five group predicted conditions lead to the correct expansion of the HSCs with the accuracy more than 80%. Considering the complexity of HSC expansion and complicated wide range of the experimental data, such relatively high interval accuracy for training and prediction as well as verification are satisfied. Therefore this nonlinear modeling makes it possible to describe quantitatively the effects of the culture conditions on the HSC expansion and to predict the optimal culture conditions for higher ex-vivo expansion of HSCs.

Polarization of human hematopoietic progenitors during contact with multipotent mesenchymal stromal cells: effects on proliferation and clonogenicity

Establishment of a defined cell culture system that facilitates ex vivo expansion of isolated hematopoietic stem and progenitor cells (HSPCs) is a crucial issue in hematology and stem cell transplantation. Here we have evaluated the capacity of primary human multipotent mesenchymal stromal cells (MSCs) to support the ex vivo expansion of peripheral CD34(+)-enriched HSPCs. We observed that HSPCs co-cultured on MSCs showed a substantially higher total expansion rate compared to those growing without. Moreover, in addition to the expansion of CD34(+)CD133(+) and CD34(+)CD133(-) cells, a third population of CD133(+)CD34(-) stem cells became detectable after expansion. Direct contact between HSPCs and the feeder layer appears beneficial for the expansion of HSPCs harboring CD133(+) phenotype, i.e., CD34(+)CD133(+) and CD133(+)CD34(-), in contrast to CD34(+)CD133(-) cells. Interestingly, electron microscopy and immunofluorescence analyses revealed that adherent HSPCs display various morphologies; they are either round with, in some cases, the appearance of a microvillar pole or exhibit several distinct types of plasma membrane protrusions such as lamellipodium and magnupodium. CD133 is selectively concentrated therein, whereas CD34 is randomly distributed over the entire surface of HSPCs. Together, this co-culture offers a unique experimental system to further characterize the biology and role of markers of rare stem cell populations.