Ex vivo expansion of umbilical cord blood stem cells for transplantation: growing knowledge from the hematopoietic niche

Mesenchymal Stromal Cells from Perinatal Tissues as an Alternative for Ex Vivo Expansion of Hematopoietic Progenitor and Stem Cells from Umbilical Cord Blood

Umbilical cord blood (UCB) serves as a source of hematopoietic stem and progenitor cells (HSPCs) utilized in the regeneration of hematopoietic and immune systems, forming a crucial part of the treatment for various benign and malignant hematological diseases. UCB has been utilized as an alternative HSPC source to bone marrow (BM). Although the use of UCB has extended transplantation access to many individuals, it still encounters significant challenges in selecting a histocompatible UCB unit with an adequate cell dose for a substantial proportion of adults with malignant hematological diseases. Consequently, recent research has focused on developing ex vivo expansion strategies for UCB HSPCs. Our results demonstrate that co-cultures with the investigated mesenchymal stromal cells (MSCs) enable a 10- to 15-fold increase in the cellular dose of UCB HSPCs while partially regulating the proliferation capacity when compared to HSPCs expanded with early acting cytokines. Furthermore, the secretory profile of UCB-derived MSCs closely resembles that of BM-derived MSCs. Moreover, both co-cultures exhibit alterations in cytokine secretion, which could potentially impact HSPC proliferation during the expansion process. This study underscores the fact that UCB-derived MSCs possess a remarkably similar supportive capacity to BM-derived MSCs, implying their potential use as feeder layers in the ex vivo expansion process of HSPCs.

Human Hematopoietic Stem Cells Co-cultured in 3D with Stromal Support to Optimize Lentiviral Vector-mediated Gene Transduction

HSC transplantation (HSCT) has emerged as a promising treatment option for hematological and immunological disorders. Unfortunately, many viral vectors are inefficient at transduction, limiting the number of cells available for gene therapy in cord blood HSC transplantation. Combining ex vivo expansion and genetic manipulation of cord blood cells is a potential gene therapy approach. We present a 3D co-culture method using a demineralized bone matrix scaffold to optimize lentiviral vector-mediated gene transduction. pLenti-III-miR-GFP-has-miR-124 was transduced into cord blood HSCs. Transduced CD34 + cells co-cultured on the stromal layer for 72 h under cytokine-free conditions. We performed flow cytometry, colony assays, real-time polymerase chain reaction, and SEM morphological analysis. Seventy-two hours after transduction, when pLentiIII-miR-GFP-has-miR-124 and control vector-transduced expanded cord blood HSCs were compared to non-transduced expanded cord blood HSCs, the findings revealed 15 ± 3.04 and 55 ± 3.05-fold increases in miR-124 mRNA expression, respectively. Compared to a control culture on the same day, the expansion of CD34+, CD38-HSCs in 3D culture increased 544 ± 31.09 fold. This result demonstrated that the 3D-culture system could emerge as a novel approach to overcoming the current limitations of cord blood HSC transduction. In the future, this research could be applied in a therapeutic setting.

Cord Blood Plasma and Placental Mesenchymal Stem Cells-Derived Exosomes Increase Ex Vivo Expansion of Human Cord Blood Hematopoietic Stem Cells While Maintaining Their Stemness

BACKGROUND

Mesenchymal stem cells (MSCs) have been used for ex vivo expansion of umbilical cord blood (UCB) hematopoietic stem cells (HSCs) to maintain their primitive characters and long-term reconstitution abilities during transplantation. Therapeutic effects of MSCs mainly rely on paracrine mechanisms, including secretion of exosomes (Exos). The objective of this study was to examine the effect of cord blood plasma (CBP)-derived Exos (CBP Exos) and Placental MSCs-derived Exos (MSCs Exos) on the expansion of UCB HSCs to increase their numbers and keep their primitive characteristics.

METHODS

CD34⁺ cells were isolated from UCB, cultured for 10 days, and the expanded HSCs were sub-cultured in semisolid methylcellulose media for primitive colony forming units (CFUs) assay. MSCs were cultured from placental chorionic plates.

RESULTS

CBP Exos and MSCs Exos compared with the control group significantly increased the number of total nucleated cells (TNCs), invitro expansion of CD34⁺ cells, primitive subpopulations of CD34⁺38⁺ and CD34⁺38^-Lin^- cells (p < 0.001). The expanded cells showed a significantly higher number of total CFUs in the Exos groups (p < 0.01).

CONCLUSION

CBP- and placental-derived exosomes are associated with significant ex vivo expansion of UCB HSCs, while maintaining their primitive characters and may eliminate the need for transplantation of an additional unit of UCB.

Therapeutic targeting and HSC proliferation by small molecules and biologicals

Hematopoietic stem cells (HSCs) have considerably therapeutic value on autologous and allogeneic transplantation for many malignant/non-malignant hematological diseases, especially with improvement of gene therapy. However, acquirement of limited cell dose from HSC sources is the main handicap for successful transplantation. Therefore, many strategies based on the utilization of various cytokines, interaction of stromal cells, modulation of several extrinsic and intrinsic factors have been developed to promote ex vivo functional HSC expansion with high reconstitution ability until today. Besides all these strategies, small molecules become prominent with their ease of use and various advantages when they are translated to the clinic. In the last two decades, several small molecule compounds have been investigated in pre-clinical studies and, some of them were evaluated in different stages of clinical trials for their safety and efficiencies. In this chapter, we will present an overview of HSC biology, function, regulation and also, pharmacological HSC modulation with small molecules from pre-clinical and clinical perspectives.

IL3 Has a Detrimental Effect on Hematopoietic Stem Cell Self-Renewal in Transplantation Settings

The ex vivo expansion and maintenance of long-term hematopoietic stem cells (LT-HSC) is crucial for stem cell-based gene therapy. A combination of stem cell factor (SCF), thrombopoietin (TPO), FLT3 ligand (FLT3) and interleukin 3 (IL3) cytokines has been commonly used in clinical settings for the expansion of CD34⁺ from different sources, prior to transplantation. To assess the effect of IL3 on repopulating capacity of cultured CD34⁺ cells, we employed the commonly used combination of STF, TPO and FILT3 with or without IL3. Expanded cells were transplanted into NSG mice, followed by secondary transplantation. Overall, this study shows that IL3 leads to lower human cell engraftment and repopulating capacity in NSG mice, suggesting a negative effect of IL3 on HSC self-renewal. We, therefore, recommend omitting IL3 from HSC-based gene therapy protocols.

New Insights into Hematopoietic Stem Cell Expansion to Stimulate Repopulation of the Adult Blood System for Transplantation

Successful engraftment of hematopoietic stem cells (HSCs) and progenitor cells (HSPCs) may be considered as a basis for the repopulation of the blood cells after transplantation in adults. Therefore, in vivo and ex vivo expansion of HSCs holds great promise for clinical applications. In this review, the mechanisms of HSC expansion will be discussed, considering the previous studies and works of literature. This is aimed to identify the signaling pathways that regulate HSC expansion and improve the application of engraftment in disease management. The following aspects will be included: (i) Stimulation of HSCs growth in vivo through gene regulation and cytokines activation; (ii) direct or indirect induction of HSC expansion by regulating signaling pathways; (iii) addition to assisting cells to help in the proliferation of HSCs; (iv) changing of living environment in the HSCs cultures via adjusting components and forms of cultures; (v) enhancement of HSC expansion by incorporating substances, such as extracellular vesicles (EVs), UM171, among others. In this review, recent new findings that provide us with new insights into HSC expansion methods have been summarized. Furthermore, these findings will also provide more possibilities for the development of some novel strategies for expanding and engrafting HSCs applied for treatments of some hematopoietic disorders.

In vitro culture of hematopoietic stem cell niche using angiopoietin-1-coupled alginate hydrogel

Stem cells exist and maintain their quiescence and pluripotency in stem cell niche. Here, we hypothesized that regulation of cell-cell interactions using a polymeric scaffold as synthetic extracellular matrix (ECM) could be critical in creating a hematopoietic stem cell (HSC) niche in vitro. Angiopoietin-1 (Ang1) binds to the tyrosine kinase receptor (Tie2), and regulation of the Tie2/Ang1 interaction is important in maintaining the quiescence of HSCs in vivo. Alginate hydrogel was thus modified with Ang1 as a synthetic ECM to mimic the HSC niche. Long-term HSCs (CD34^-, CD135^-, and CD150⁺) were isolated from mouse femurs and cultured on Ang1-modified alginate hydrogel. The percentage of LT-HSCs in G₀ phase was 46.8 ± 1.8%, which was comparable to that of LT-HSCs co-cultured with osteoblasts (46.8 ± 2.1%). Ang1-coupled alginate gels were useful to provide a niche for HSC quiescence without a co-culture system. Polymeric scaffolds containing biomimetic and cell-instructive characteristics for stem cell phenotype regulation might help create HSC niches in vitro and be useful to engineer tissues and transplant stem cells.

Genomic Engineering in Human Hematopoietic Stem Cells: Hype or Hope?

Many gene editing techniques are developed and tested, yet, most of these are optimized for transformed cell lines, which differ from their primary cell counterparts in terms of transfectability, cell death propensity, differentiation capability, and chromatin accessibility to gene editing tools. Researchers are working to overcome the challenges associated with gene editing of primary cells, namely, at the level of improving the gene editing tool components, e.g., the use of modified single guide RNAs, more efficient delivery of Cas9 and RNA in the ribonucleoprotein of these cells. Despite these efforts, the low efficiency of proper gene editing in true primary cells is an obstacle that needs to be overcome in order to generate sufficiently high numbers of corrected cells for therapeutic use. In addition, many of the therapeutic candidate genes for gene editing are expressed in more mature blood cell lineages but not in the hematopoietic stem cells (HSCs), where they are tightly packed in heterochromatin, making them less accessible to gene editing enzymes. Bringing HSCs in proliferation is sometimes seen as a solution to overcome lack of chromatin access, but the induction of proliferation in HSCs often is associated with loss of stemness. The documented occurrences of off-target effects and, importantly, on-target side effects also raise important safety issues. In conclusion, many obstacles still remain to be overcome before gene editing in HSCs for gene correction purposes can be applied clinically. In this review, in a perspective way, we will discuss the challenges of researching and developing a novel genetic engineering therapy for monogenic blood and immune system disorders.

Effects of mouse fetal liver cell culture density on hematopoietic cell expansion in three-dimensional cocultures with stromal cells

OBJECTIVE

An effective ex vivo expansion system of primitive hematopoietic cells (HCs) is required for wider application of hematopoietic stem cell transplantation. In this study, we examined effects of culture density on mouse fetal liver cells (FLCs) used as an HC source for the expansion of primitive HCs in three-dimensional (3D) cocultures with two kinds of mouse stromal cell lines (OP9 or C3H10T1/2).

MATERIALS AND METHODS

FLCs were seeded at different densities (1, 2, and 10 × 10⁷ cells/cm³) into porous polymer scaffolds with or without stromal cell layers and HCs were expanded in the cultures for 2 weeks without exogenous cytokines.

RESULTS

Differential effects of culture density on HC expansion were observed between cocultures and solitary FLC controls. In stromal cell cocultures, high expansion of HCs was achieved when FLCs were seeded at low densities. In contrast, the expansion in the controls was enhanced with increasing culture densities. With respect to expansion of primitive HCs existing in the FLCs, cocultures with C3H10T1/2 cells were superior to those with OP9 cells with a 29.3-fold expansion for c-kit⁺ hematopoietic progenitor cells and 8.3-fold expansion for CD34⁺ hematopoietic stem cells. In the controls, HC expansion was lower than in any cocultures, demonstrating the advantages of coculturing for HC expansion.

CONCLUSION

Stromal cell lines are useful in expanding primitive HCs derived from FLCs in 3D cocultures. Culture density is a pivotal factor for the effective expansion of primitive HCs and this effect differs by culture condition.

Therapeutic Potential of Umbilical Cord Stem Cells for Liver Regeneration

The liver is a vital organ for life and the only internal organ that is capable of natural regeneration. Although the liver has high regeneration capacity, excessive hepatocyte death can lead to liver failure. Various factors can lead to liver damage including drug abuse, some natural products, alcohol, hepatitis, and autoimmunity. Some models for studying liver injury are APAP-based model, Fas ligand (FasL), D-galactosamine/endotoxin (Gal/ET), Concanavalin A, and carbon tetrachloride-based models. The regeneration of the liver can be carried out using umbilical cord blood stem cells which have various advantages over other stem cell types used in liver transplantation. UCB-derived stem cells lack tumorigenicity, have karyotype stability and high immunomodulatory, low risk of graft versus host disease (GVHD), low risk of transmitting somatic mutations or viral infections, and low immunogenicity. They are readily available and their collection is safe and painless. This review focuses on recent development and modern trends in the use of umbilical cord stem cells for the regeneration of liver fibrosis.

Expansion of mouse primitive hematopoietic cells in three-dimensional cultures on chemically fixed stromal cell layers

To establish a practical and convenient method to expand hematopoietic cells (HCs), we applied chemically-fixed stromal cell layers formed within three-dimensional (3D) scaffolds to feeder of HC cultures. The HCs were expanded using two successive cultures. First, stromal cells were cultured within porous polymer scaffolds and formed tissue-engineered constructs (TECs); the scaffolds containing stromal cells, were fixed using aldehyde (formaldehyde or glutaraldehyde) or organic solvents (acetone, methanol or ethanol). Second, mouse fetal liver cells (FLCs), as a source of HCs, were cultured on the TECs for 2 weeks, and the effects of fixative solutions on expansion of primitive HCs (c-kit⁺ and CD34⁺ cells) were examined. In the cultures on aldehyde-fixed TECs, primitive HCs were expanded 2.5- to 5.1-fold in the cultures on TECs fixed with glutaraldehyde, whereas no expansions were detected in those fixed with formaldehyde. However, we achieved expansion of primitive HCs > fivefold in the cultures using TECs fixed with organic solvents. Among these solvents, the highest expansions-of roughly tenfold-were obtained using acetone fixation. Ethanol-fixed TECs also supported the expansion of the primitive HCs well (6.6- to 8.0-fold). In addition to these sufficient expansions, the procedure and storage of fixed TECs is fairly easy. Thus, HC expansion on chemically-fixed TECs may be a practical method for expanding primitive HCs.

Preclinical Development of Autologous Hematopoietic Stem Cell-Based Gene Therapy for Immune Deficiencies: A Journey from Mouse Cage to Bed Side

Recent clinical trials using patient’s own corrected hematopoietic stem cells (HSCs), such as for primary immunodeficiencies (Adenosine deaminase (ADA) deficiency, X-linked Severe Combined Immunodeficiency (SCID), X-linked chronic granulomatous disease (CGD), Wiskott–Aldrich Syndrome (WAS)), have yielded promising results in the clinic; endorsing gene therapy to become standard therapy for a number of diseases. However, the journey to achieve such a successful therapy is not easy, and several challenges have to be overcome. In this review, we will address several different challenges in the development of gene therapy for immune deficiencies using our own experience with Recombinase-activating gene 1 (RAG1) SCID as an example. We will discuss product development (targeting of the therapeutic cells and choice of a suitable vector and delivery method), the proof-of-concept (in vitro and in vivo efficacy, toxicology, and safety), and the final release steps to the clinic (scaling up, good manufacturing practice (GMP) procedures/protocols and regulatory hurdles).

The intragraft vascularized bone marrow component plays a critical role in tolerance induction after reconstructive transplantation

The role of the vascularized bone marrow component as a continuous source of donor-derived hematopoietic stem cells that facilitate tolerance induction of vascularized composite allografts is not completely understood. In this study, vascularized composite tissue allograft transplantation outcomes between recipients receiving either conventional bone marrow transplantation (CBMT) or vascularized bone marrow (VBM) transplantation from Balb/c (H2d) to C57BL/6 (H2b) mice were compared. Either high- or low-dose CBMT (1.5 × 10⁸ or 3 × 10⁷ bone marrow cells, respectively) was applied. In addition, recipients were treated with costimulation blockade (1 mg anti-CD154 and 0.5 mg CTLA4Ig on postoperative days 0 and 2, respectively) and short-term rapamycin (3 mg/kg/day for the first posttransplant week and then every other day for another 3 weeks). Similar to high-dose conventional bone marrow transplantation, 5/6 animals in the vascularized bone marrow group demonstrated long-term allograft survival (>120 days). In contrast, significantly shorter median survival was noted in the low-dose CBMT group (~64 days). Consistently high chimerism levels were observed in the VBM transplantation group. Notably, low levels of circulating CD4⁺ and CD8⁺ T cells and a higher ratio of Treg to Teff cells were maintained in VBM transplantation and high-dose CBMT recipients (>30 days) but not in low-dose VBM transplant recipients. Donor-specific hyporesponsiveness was shown in tolerant recipients in vitro. Removal of the vascularized bone marrow component after secondary donor-specific skin transplantation did not affect either primary allograft or secondary skin graft survival.

HIV-1 Tat protein inhibits the hematopoietic support function of human bone marrow mesenchymal stem cells

Most HIV-1-infected patients experience hematopoiesis suppression complications. Bone marrow mesenchymal stem cells (BMSCs) are involved in regulation of hematopoietic homeostasis, so we investigated the role of Tat, a protein released by infected cells in bone marrow and impacted differentiation potential of mesenchymal stem cells, in the BMSC hematopoietic support function. BMSCs were treated with HIV-1 Tat protein (BMSC_Tat-p), transfected with HIV-1 Tat mRNA (BMSC_Tat-m) or treated with solvent (PBS) (BMSC_con) for 20 days. Then, the hematopoietic support function of BMSC_Tat-p, BMSC_Tat-m and BMSC_con was analyzed via ex vivo expansion of hematopoietic stem cells (HSCs) grown on the BMSCs and via in vivo cotransplantation of HSCs and BMSCs. In addition, the hematopoiesis-supporting gene expression patterns of BMSC_Tat-p, BMSC_Tat-m and BMSC_con were compared. The results showed that BMSC_Tat-p and BMSC_Tat-m displayed reduced expansion, a decline in the number of colony forming units (CFUs) and a decreased proportion of the primitive subpopulation of hematopoietic stem cells under coculture conditions compared with BMSC_con. The ability of BMSC_Tat-p to support hematopoietic recovery was also impaired, which was further confirmed by the patterns in gene expression analysis. In conclusion, Tat treatment reduced the function of BMSCs in hematopoietic support, likely by downregulating the expression of a series of hematopoietic cytokines.

CXCL12/CXCR4 Signaling Enhances Human PSC-Derived Hematopoietic Progenitor Function and Overcomes Early In Vivo Transplantation Failure

Human pluripotent stem cells (hPSCs) generate hematopoietic progenitor cells (HPCs) but fail to engraft xenograft models used to detect adult/somatic hematopoietic stem cells (HSCs) from donors. Recent progress to derive hPSC-derived HSCs has relied on cell-autonomous forced expression of transcription factors; however, the relationship of bone marrow to transplanted cells remains unknown. Here, we quantified a failure of hPSC-HPCs to survive even 24 hr post transplantation. Across several hPSC-HPC differentiation methodologies, we identified the lack of CXCR4 expression and function. Ectopic CXCR4 conferred CXCL12 ligand-dependent signaling of hPSC-HPCs in biochemical assays and increased migration/chemotaxis, hematopoietic progenitor capacity, and survival and proliferation following in vivo transplantation. This was accompanied by a transcriptional shift of hPSC-HPCs toward somatic/adult sources, but this approach failed to produce long-term HSC xenograft reconstitution. Our results reveal that networks involving CXCR4 should be targeted to generate putative HSCs with in vivo function from hPSCs.

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Transplant kinetics indicate human PSC-HPCs fail in the first 24 hr in bone marrow

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hPSC-HPCs aberrantly express chemokine receptors, specifically lacking CXCR4

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Ectopic CXCR4 enhances hPSC-HPC function in vitro and transplantation in vivo

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CXCR4 linked with global transcriptional shift of hPSC-HPCs toward somatic HPCs

Ex Vivo Expansion of Hematopoietic Stem Cells for Therapeutic Purposes: Lessons from Development and the Niche

Expansion of hematopoietic stem cells (HSCs) for therapeutic purposes has been a “holy grail” in the field for many years. Ex vivo expansion of HSCs can help to overcome material shortage for transplantation purposes and genetic modification protocols. In this review, we summarize improved understanding in blood development, the effect of niche and conservative signaling pathways on HSCs in mice and humans, and also advances in ex vivo culturing protocols of human HSCs with cytokines or small molecule compounds. Different expansion protocols have been tested in clinical trials. However, an optimal condition for ex vivo expansion of human HSCs still has not been found yet. Translating and implementing new findings from basic research (for instance by using genetic modification of human HSCs) into clinical protocols is crucial to improve ex vivo expansion and eventually boost stem cell gene therapy.

Clinical Applications of Carbon Nanomaterials in Diagnostics and Therapy

Nanomaterials have the potential to improve how patients are clinically treated and diagnosed. While there are a number of nanomaterials that can be used toward improved drug delivery and imaging, how these nanomaterials confer an advantage over other nanomaterials, as well as current clinical approaches is often application or disease specific. How the unique properties of carbon nanomaterials, such as nanodiamonds, carbon nanotubes, carbon nanofibers, graphene, and graphene oxides, make them promising nanomaterials for a wide range of clinical applications are discussed herein, including treating chemoresistant cancer, enhancing magnetic resonance imaging, and improving tissue regeneration and stem cell banking, among others. Additionally, the strategies for further improving drug delivery and imaging by carbon nanomaterials are reviewed, such as inducing endothelial leakiness as well as applying artificial intelligence toward designing optimal nanoparticle-based drug combination delivery. While the clinical application of carbon nanomaterials is still an emerging field of research, there is substantial preclinical evidence of the translational potential of carbon nanomaterials. Early clinically trial studies are highlighted, further supporting the use of carbon nanomaterials in clinical applications for both drug delivery and imaging.

Homing Genes Expression in Fucosyltransferase VI-Treated Umbilical Cord Blood CD133+ Cells which Expanded on Protein-Coated Nanoscaffolds

Umbilical cord blood (UCB)-derived hematopoietic stem cells (HSCs) are considered because of their self-renewing, differentiating, proliferating, and readily available properties. Moreover, HSCs' homing to the hematopoietic microenvironment is an important step in their transplantation process. But low content of progenitor cells in one unit of UCB and defect in the bone marrow (BM) homing limit their applications. Hence, we decided to correct this deficiency with ex vivo incubation of CD133+ cells using fucosyltransferase VI and GDP-fucose. Then C-X-C chemokines receptor-4 (CXCR4), very late activation antigen-4 (VLA4), very late activation antigen-5 (VLA5), lymphocyte function-associated antigen-1 (LFA-1), and E-cadherin (E-cad) genes expressions were investigated with the goal of homing evaluation. The purity of MACS isolated CD133+ cells and confirmation of fucosylation were done by flow cytometry, and the viability of cells seeded on protein-coated poly L-lactic acid (PLLA) scaffold was proven via MTT assay. Scanning electron microscopy (SEM), CFU assays, and expression assays of CXCR4, VLA4, VLA5, LFA-1 and E-cad by real-time PCR were performed, too. Flow cytometry data showed that isolated cells were suitable for fucosyltransferase VI (FT-VI) incubation and expansion on nanoscaffolds. MTT, CFU assays, and SEM micrographs demonstrated fibronectin (FN)-collagen-selectin (FCS)-coated scaffold serve as best environment for viability, clonogenicity, and cell attachment. High levels of homing genes expression were also observed in cells seeded on FCS-coated scaffolds. Also, CXCR4 flow cytometry analysis confirmed real-time data. FCS-PLLA scaffolds provided optimal conditions for viability of FT-VI-treated CD133+ cells, and clonogenicity with the goal of improving homing following UCB-HSCs transplantation.

Tracking hematopoietic precursor division ex vivo in real time

BACKGROUND

Deciphering molecular mechanisms underlying the division of hematopoietic stem cells (HSCs) and malignant precursors would improve our understanding of the basis of stem cell-fate decisions and oncogenic transformation.

METHODS

Using a novel reporter of hematopoietic precursor, Evi1-GFP, we tracked the division of hematopoietic precursors in culture in real time.

RESULTS

First, we confirmed that Evi1-GFP is a faithful reporter of HSC activity and identified three dividing patterns of HSCs: symmetric renewal, symmetric differentiation, and asymmetric division. Moreover, we found that the cytokine and growth factor combination (STIF) promotes symmetric renewal, whereas OP9 stromal cells balance symmetric renewal and differentiation of HSCs ex vivo. Interestingly, we found that Tet2 knockout HSCs underwent more symmetric differentiation in culture compared with the wild-type control. Intriguingly, OP9 stromal cells reverse the phenotype of Tet2 knockout HSCs ex vivo. Furthermore, we demonstrated that Tet2 ^-/- ;Flt3^ITD acute myeloid leukemia (AML) precursors primarily underwent symmetric renewal divisions in culture. Mechanistically, we demonstrated that inhibiting DNA methylation can reverse the aberrant division phenotypes of Tet2 ^-/- and Tet2 ^-/- ;FLT3^ITD precursors, suggesting that abnormal DNA methylation plays an important role in controlling (pre-)leukemic precursor fate decision ex vivo.

CONCLUSIONS

Our study exploited a new system to explore the molecular mechanisms of the regulation of benign and malignant hematopoietic precursor division ex vivo. The knowledge learned from these studies will provide new insights into the molecular mechanisms of HSC fate decision and leukemogenesis.

Transcriptionally and Functionally Distinct Mesenchymal Subpopulations Are Generated from Human Pluripotent Stem Cells

Various mesenchymal cell types have been identified as critical components of the hematopoietic stem/progenitor cell (HSPC) niche. Although several groups have described the generation of mesenchyme from human pluripotent stem cells (hPSCs), the capacity of such cells to support hematopoiesis has not been reported. Here, we demonstrate that distinct mesenchymal subpopulations co-emerge from mesoderm during hPSC differentiation. Despite co-expression of common mesenchymal markers (CD73, CD105, CD90, and PDGFRβ), a subset of cells defined as CD146^hiCD73^hi expressed genes associated with the HSPC niche and supported the maintenance of functional HSPCs ex vivo, while CD146^loCD73^lo cells supported differentiation. Stromal support of HSPCs was contact dependent and mediated in part through high JAG1 expression and low WNT signaling. Molecular profiling revealed significant transcriptional similarity between hPSC-derived CD146⁺⁺ and primary human CD146⁺⁺ perivascular cells. The derivation of functionally diverse types of mesenchyme from hPSCs opens potential avenues to model the HSPC niche and develop PSC-based therapies.

Endogenous Stem Cells in Homeostasis and Aging

In almost all human tissues and organs, adult stem cells or tissue stem cells are present in a unique location, the so-called stem cell niche or its equivalent, continuously replenishing functional differentiated cells. Those endogenous stem cells can be expanded for cell therapeutics using ex vivo cell culture or recalled for tissue repair in situ through cell trafficking and homing. In the aging process, inefficiency in the endogenous stem cell-mediated healing mechanism can emerge from a variety of impairments that accumulate in the processes of stem cell self-renewal, function, differentiation capacity, and trafficking through cell autonomous intrinsic pathways (such as epigenetic alterations) or systemic extrinsic pathways. This review examines the homeostasis of endogenous stem cells, particularly bone marrow stem cells, and their dysregulation in disease and aging and discusses possible intervention strategies. Several systemic pro-aging and rejuvenating factors, recognized in heterochronic parabiosis or premature aging progeroid animal models, are reviewed as possible anti-aging pharmaceutical targets from the perspective of a healthy environment for endogenous stem cells. A variety of epigenetic modifications and chromosome architectures are reviewed as an intrinsic cellular pathway for aging and senescence. A gradual increase in inflammatory burden during aging is also reviewed. Finally, the tissue repair and anti-aging effects of Substance-P, a peptide stimulating stem cell trafficking from the bone marrow and modifying the inflammatory response, are discussed as a future anti-aging target.

Human Bone Marrow Mesenchymal Stromal Cell-Derived Osteoblasts Promote the Expansion of Hematopoietic Progenitors Through Beta-Catenin and Notch Signaling Pathways

Coculture of hematopoietic stem cells (HSC) with primary stromal cells from HSC niches supports the maintenance and expansion of HSC and progenitors ex vivo. However, a major drawback is the availability of primary human samples for research and clinical applications. We investigated the use of in vitro derived osteoblasts as a new source of feeder cells and characterized the molecular pathways that mediate their growth-promoting activities. First, we compared the growth and differentiation modulating activities of mesenchymal stromal cells (MSC)-derived osteoblasts (M-OST) with those of their undifferentiated precursor on umbilical cord blood (UCB) progenitors. Feeder-free cultures were also included as baseline control. Cell growth and expansion of hematopoietic progenitors were significantly enhanced by both feeder cell types. However, progenitor cell growth was considerably greater with M-OST. Coculture also promoted the maintenance of immature CD34⁺ progenitor subsets and modulated in a positive fashion the expression of several homing-related cell surface receptors, in a feeder-specific fashion. Serial transplantation experiments revealed that M-OST coculture supported the maintenance of long-term lympho-myeloid reconstituting HSC that provided engraftment levels that were generally superior to those from MSC cocultures. Mechanistically, we found that coculture with M-OST was associated with enhanced beta-catenin (β-Cat) activity in UCB cells and that abrogation of β-Cat/T-cell factor activity blunted the growth-promoting activity of the M-OST coculture. Conversely, Notch inhibition reduced UCB cell expansion, but to a much lesser extent. In conclusion, this study demonstrates that M-OST are excellent feeder cells for HSC and progenitors, and it identifies key molecular pathways that are responsible for the growth-enhancing activities of osteoblasts on UCB progenitors.

Engineered M13 Nanofiber Accelerates Ischemic Neovascularization by Enhancing Endothelial Progenitor Cells

Dysfunction or loss of blood vessel causes several ischemic diseases. Although endothelial progenitor cells (EPCs) are a promising source for cell-based therapy, ischemia-induced pathophysiological condition limits the recovery rate by causing drastic cell death. To overcome this issue, we attempted to develop a cell-targeted peptide delivery and priming system to enhance EPC-based neovascularization using an engineered M13 bacteriophage harboring nanofibrous tubes displaying ~2700 multiple functional motifs. The M13 nanofiber was modified by displaying RGD, which is an integrin-docking peptide, on the minor coat protein, and by mutilayering SDKP motifs, which are the key active sites for thymosin β4, on the major coat protein. The engineered M13 nanofiber dramatically enhanced ischemic neovascularization by activating intracellular and extracellular processes such as proliferation, migration, and tube formation in the EPCs. Furthermore, transplantation of the primed EPCs with the M13 nanofiber harboring RGD and SDKP facilitated functional recovery and neovascularization in a murine hindlimb ischemia model. Overall, this study demonstrates the effectiveness of the M13 nanofiber-based novel peptide delivery and priming strategy in promoting EPC bioactivity and neovessel regeneration. To our knowledge, this is first report on M13 nanofibers harboring dual functional motifs, the use of which might be a novel strategy for stem and progenitor cell therapy against cardiovascular ischemic diseases.

Immobilisation of Delta-like 1 ligand for the scalable and controlled manufacture of hematopoietic progenitor cells in a stirred bioreactor

Background

Umbilical cord blood provides a source of hematopoietic stem cells for transplantation with immunological and availability advantages over conventional bone marrow sources. Limited cell numbers and slower engraftment from umbilical cord blood units has led to the clinical development of immobilised Notch ligand Delta-Like 1 to promote ex vivo expansion of a rapidly engrafting cell population. However, current immobilisation methods are not simple to scale in a controlled manner.

Results

Delta-Like 1 was immobilised onto streptavidin coated magnetic particles via a heterobifunctionalised polyethylene glycol linker molecule to provide an easily manipulated format of surface protein presentation. CD34⁺ enriched cord blood cells were treated with Delta-Like 1 immobilised particles, and immunophenotypic markers measured to monitor population distributions using cluster identification, characterization, and regression software. The amenability of the approach to scalability was evaluated in a micro-scale stirred tank bioreactor. Surface concentration of Delta-Like 1 was well controlled used differing stoichiometric reagent ratios. Protein immobilisation was a cost effective process and particles were efficiently removed from the final cell product. Immobilised Delta-Like 1 is functional and stimulates qualitatively similar CD34^hi, CD38^lo, CD90^lo, CD133^hi, CD135^hi progenitor expansion in both static culture and scalable stirred culture platforms.

Conclusions

Immobilised Delta-Like 1 in this form has the potential to improve the manufacturing efficiency and control of final ex vivo expanded cell product through compatibility with highly controlled and characterised suspension culture systems.

Electronic supplementary material

The online version of this article (doi:10.1186/s12896-017-0383-0) contains supplementary material, which is available to authorized users.

Endothelial progenitor cells promote efficient ex vivo expansion of cord blood-derived hematopoietic stem/progenitor cells

BACKGROUND AIMS

Cord blood (CB) hematopoietic stem cell transplantation has often been limited by the scarcity of stem cells. Therefore, the number of CB hematopoietic stem/progenitor cells (HSPCs) should be increased while maintaining the stem cell characteristics.

METHODS

We designed an ex vivo culture system using endothelial progenitor cells (EPCs) as stroma to determine the capacity of expanding CB-HSPCs in a defined medium, the effect on engraftment of the expanded cells in a mouse model and the underlying mechanism.

RESULTS

After 7 days of culture, compared with those cultured with cytokines alone (3.25 ± 0.59), CD34+ cells under contact and non-contact co-culture with EPCs were expanded by 5.38 ± 0.61 (P = 0.003) and 4.06 ± 0.43 (P = 0.025)-fold, respectively. Direct cell-to-cell contact co-culture with EPCs resulted in more primitive CD34+ CD38- cells than stroma-free culture (156.17 ± 21.32 versus 79.12 ± 19.77-fold; P = 0.010). Comparable engraftment of day 7 co-cultured HSPCs with respect to HSPCs at day 0 in nonobese diabetic-severe combined immunodeficiency disease (NOD/SCID) mice was measured as a percentage of chimerism (13.3% ± 11.0% versus 16.0% ± 14.3%; P = 0.750). EPCs highly expressed interleukin 6 (IL6) and angiopoietin 1 (ANGPT1), the hematopoietic- related cytokines. A higher transcriptional level of WNT5A genes in EPCs and co-cultured HSPCs suggests that the activation of Wnt signaling pathway may play a role in HSPCs' expansion ex vivo.

DISCUSSION

These data demonstrated that EPCs improve the CD34+ population but do not compromise the repopulating efficacy of the amplified HSPCs, possibly via cytokine secretion and Wnt signaling pathway activation.

Specification of haematopoietic stem cell fate via modulation of mitochondrial activity

Haematopoietic stem cells (HSCs) differ from their committed progeny by relying primarily on anaerobic glycolysis rather than mitochondrial oxidative phosphorylation for energy production. However, whether this change in the metabolic program is the cause or the consequence of the unique function of HSCs remains unknown. Here we show that enforced modulation of energy metabolism impacts HSC self-renewal. Lowering the mitochondrial activity of HSCs by chemically uncoupling the electron transport chain drives self-renewal under culture conditions that normally induce rapid differentiation. We demonstrate that this metabolic specification of HSC fate occurs through the reversible decrease of mitochondrial mass by autophagy. Our data thus reveal a causal relationship between mitochondrial metabolism and fate choice of HSCs and also provide a valuable tool to expand HSCs outside of their native bone marrow niches.

Pharmacological inhibition of AKT activity in human CD34+ cells enhances their ability to engraft immunodeficient mice

Although practiced clinically for more than 40 years, the use of hematopoietic stem cell (HSC) transplantation remains limited by the inability to expand functional HSCs ex vivo. To determine the role of phosphoinositide 3-kinase (PI3K)/AKT signaling in human hematopoietic stem and progenitor cell (HSPC) maintenance, we examined the effect of genetic and pharmacological inhibition of AKT on human umbilical cord blood (UCB) CD34⁺ cells. We found that knock-down of AKT1 in human UCB CD34⁺ cells using short interfering RNAs targeting AKT1 enhances their quiescence and colony formation potential in vitro. We treated human UCB CD34⁺ cells with an AKT-specific inhibitor (AKTi) and performed both in vitro and in vivo stem and progenitor cell assays. We found that ex vivo treatment of human HSPCs maintains CD34 expression and enhances colony formation in serial replating assays. Moreover, pharmacological inhibition of AKT enhances the short-term repopulating potential of human UCB CD34⁺ cells in immunodeficient mice. Mechanistically, genetic and pharmacological inhibition of AKT activity promotes human HSPC quiescence. These preclinical results suggest a positive role for AKTi during ex vivo culture of human UCB HSPCs.

Evaluation of umbilical cord blood CD34+ hematopoietic stem cells expansion with inhibition of TGF-β receptorII in co-culture with bone marrow mesenchymal stromal cells

BACKGROUND

Umbilical cord blood (UCB) is an important source of hematopoietic stem cells (HSCs). However, low number of HSCs in UCB has been an obstacle for adult hematopoietic stem cell transplantation. The expansion of HSCs in culture is one approach to overcome this problem. In this study, we investigated the expansion of UCB-HSCs by using human bone marrow mesenchymal stromal cells (MSCs) as feeder layer as well as inhibiting the TGF-β signaling pathway through reduction of TGF-βRII expression.

MATERIALS AND METHODS

CD34(+) cells were isolated from UCB and transfected by SiRNA targeting TGF-βRII mRNA. CD34(+) cells were expanded in four culture media with different conditions, including 1) expansion of CD34(+) cells in serum free medium containing growth factors, 2) expansion of cells transfected with SiRNA targeting TGF-βRII in medium containing growth factors, 3) expansion of cells in presence of growth factors and MSCs, 4) expansion of cells transfected with SiRNA targeting TGF-βRII on MSCs feeder layer in medium containing growth factors. These culture conditions were evaluated for the number of total nucleated cells (TNCs), CD34 surface marker as well as using CFU assay on 8th day after culture.

RESULTS

The fold increase in CD34(+) cells, TNCs, and colony numbers (71.8±6.9, 93.2±10.2 and 128±10, respectively) was observed to be highest in fourth culture medium compared to other culture conditions. The difference between number of cells in four culture media in 8th day compared to unexpanded cells (0day) before expansion was statistically significant (P<0.05).

CONCLUSION

The results showed that transfection of CD34(+) cells with SiRNA targeting TGF-βRII and their co-culture with MSCs could considerably increase the number of progenitors. Therefore, this method could be useful for UCB-HSCs expansion.

Gene editing and its application for hematological diseases

The use of precise, rationally designed gene-editing nucleases allows for targeted genome and transcriptome modification, and at present, four major classes of nucleases are being employed: zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), meganucleases (MNs), and clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9. Each reagent shares the ability to recognize and bind a target sequence of DNA. Depending on the properties of the reagent, the DNA can be cleaved on one or both strands, or epigenetic changes can be mediated. These novel properties can impact hematological disease by allowing for: (1) direct modification of hematopoietic stem/progenitor cells (HSPCs), (2) gene alteration of hematopoietic lineage committed terminal effectors, (3) genome engineering in non-hematopoietic cells with reprogramming to a hematopoietic phenotype, and (4) transcriptome modulation for gene regulation, modeling, and discovery.

Caught in a Wnt storm: Complexities of Wnt signaling in hematopoiesis

The Wnt signaling pathway is an evolutionary conserved pathway that is involved in the development of almost every organ system in the body and provides self-renewal signals for most, if not all, adult stem cell systems. In recent years, this pathway has been studied by various research groups working on hematopoietic stem cells, resulting in contradicting conclusions. Here, we discuss and interpret the results of these studies and propose that Wnt dosage, the source of hematopoietic stem cells, and interactions with other pathways explain these disparate results.

Expansion of Human Hematopoietic Stem/Progenitor Cells on Decellularized Matrix Scaffolds

Umbilical cord blood (UCB) is one of the richest sources for hematopoietic stem/progenitor cells (HSPCs), with more than 3000 transplantations performed each year for the treatment of leukemia and other bone marrow, immunological, and hereditary diseases. However, transplantation of single cord blood units is mostly restricted to children, due to the limited number of HSPC per unit. This unit develops a method to increase the number of HSPCs in laboratory conditions by using cell-free matrices from bone marrow cells that mimic 'human-body-niche-like' conditions as biological scaffolds to support the ex vivo expansion of HSPCs. In this unit, we describe protocols for the isolation and characterization of HSPCs from UCB and their serum-free expansion on decellularized matrices. This method may also help to provide understanding of the biochemical organization of hematopoietic niches and lead to suggestions regarding the design of tissue engineering-based biomimetic scaffolds for HSPC expansion for clinical applications.

IL2rg Cytokines Enhance Umbilical Cord Blood CD34+ Cells Differentiation to T Cells

PURPOSE

Umbilical cord blood (UCB) is an alternative source of hematopoietic stem cell (HSC) transplantation for the treatment of patients with leukemia if matched donor is not available. CD34+ is a pan marker for human hematopoietic stem cells, including umbilical cord blood stem cell. In comparison to other sources, cord blood CD34+ cells proliferate more rapidly and produce large number of progeny cells. For ex vivo expansion of Umbilical Cord Blood- HSCs/HPCs, different combinations of cytokines have been used in many laboratories. IL2rg cytokines, including IL2, IL7 and IL15, are key cytokines in the regulation of differentiation, proliferation and survival of immune cells. IL2 is important cytokine for T cell survival and proliferation, IL7 involve in B cell development and IL15 is a key cytokine for NK cell development. In this study we evaluated the generation of T cells derived from CD34+ and CD34- cord blood mononuclear cells by using combination of cytokines including IL2, IL7 and IL15.

METHODS

Cultured cord blood mononuclear cells were evaluated at distinct time points during 21 days by using flow cytometry.

RESULTS

Present study showed that differentiation of T cells derived from CD34+ cord blood mononuclear cells increased by using IL2 and IL7 at different time points. In the other hand IL15 did not show any significant role in generation of T cells from CD34+ cord blood mononuclear cells.

CONCLUSION

Taken together, our data illustrated that either IL2 or IL7 versus other cytokine combinations, generate more T cell from cord blood CD34 cells, probably this cytokines can be the best condition for ex vivo expansion of UCB HSCs.

Differential ability of MSCs isolated from placenta and cord as feeders for supporting ex vivo expansion of umbilical cord blood derived CD34(+) cells

INTRODUCTION

Ex vivo expansion of umbilical cord blood (UCB) is attempted to increase cell numbers to overcome the limitation of cell dose. Presently, suspension cultures or feeder mediated co-cultures are performed for expansion of hematopoietic stem cells (HSCs). Mesenchymal stem cells (MSCs) have proved to be efficient feeders for the maintenance of HSCs. Here, we have established MSCs-HSCs co-culture system with MSCs isolated from less invasive and ethically acceptable sources like umbilical cord tissue (C-MSCs) and placenta (P-MSCs). MSCs derived from these tissues are often compared with bone marrow derived MSCs (BM-MSCs) which are considered as a gold standard. However, so far none of the studies have directly compared C-MSCs with P-MSCs as feeders for ex vivo expansion of HSCs. Thus, we for the first time performed a systematic comparison of hematopoietic supportive capability of C and P-MSCs using paired samples.

METHODS

UCB-derived CD34(+) cells were isolated and co-cultured on irradiated C and P-MSCs for 10 days. C-MSCs and P-MSCs were isolated from the same donor. The cultures comprised of serum-free medium supplemented with 25 ng/ml each of SCF, TPO, Flt-3 L and IL-6. After 10 days cells were collected and analyzed for phenotype and functionality.

RESULTS

C-MSCs and P-MSCs were found to be morphologically and phenotypically similar but exhibited differential ability to support ex vivo hematopoiesis. Cells expanded on P-MSCs showed higher percentage of primitive cells (CD34(+)CD38(-)), CFU (Colony forming unit) content and LTC-IC (Long term culture initiating cells) ability. CD34(+) cells expanded on P-MSCs also exhibited better in vitro adhesion to fibronectin and migration towards SDF-1α and enhanced NOD/SCID repopulation ability, as compared to those grown on C-MSCs. P-MSCs were found to be closer to BM-MSCs in their ability to expand HSCs. P-MSCs supported expansion of functionally superior HSCs by virtue of reduction in apoptosis of primitive HSCs, higher Wnt and Notch activity, HGF secretion and cell-cell contact. On the other hand, C-MSCs facilitated expansion of progenitors (CD34(+)CD38(+)) and differentiated (CD34(-)CD38(+)) cells by secretion of IL1-α, β, MCP-2, 3 and MIP-3α.

CONCLUSIONS

P-MSCs were found to be better feeders for ex vivo maintenance of primitive HSCs with higher engraftment potential than the cells expanded with C-MSCs as feeders.

The use of covalently immobilized stem cell factor to selectively affect hematopoietic stem cell activity within a gelatin hydrogel

Hematopoietic stem cells (HSCs) are a rare stem cell population found primarily in the bone marrow and responsible for the production of the body's full complement of blood and immune cells. Used clinically to treat a range of hematopoietic disorders, there is a significant need to identify approaches to selectively expand their numbers ex vivo. Here we describe a methacrylamide-functionalized gelatin (GelMA) hydrogel for in vitro culture of primary murine HSCs. Stem cell factor (SCF) is a critical biomolecular component of native HSC niches in vivo and is used in large dosages in cell culture media for HSC expansion in vitro. We report a photochemistry based approach to covalently immobilize SCF within GelMA hydrogels via acrylate-functionalized polyethylene glycol (PEG) tethers. PEG-functionalized SCF retains the native bioactivity of SCF but can be stably incorporated and retained within the GelMA hydrogel over 7 days. Freshly-isolated murine HSCs cultured in GelMA hydrogels containing covalently-immobilized SCF showed reduced proliferation and improved selectivity for maintaining primitive HSCs. Comparatively, soluble SCF within the GelMA hydrogel network induced increased proliferation of differentiating hematopoietic cells. We used a microfluidic templating approach to create GelMA hydrogels containing gradients of immobilized SCF that locally direct HSC response. Together, we report a biomaterial platform to examine the effect of the local presentation of soluble vs. matrix-immobilized biomolecular signals on HSC expansion and lineage specification. This approach may be a critical component of a biomaterial-based artificial bone marrow to provide the correct sequence of niche signals to grow HSCs in the laboratory.

Human adipose-tissue derived stromal cells in combination with hypoxia effectively support ex vivo expansion of cord blood haematopoietic progenitors

The optimisation of haematopoietic stem and progenitor cell expansion is on demand in modern cell therapy. In this work, haematopoietic stem/progenitor cells (HSPCs) have been selected from unmanipulated cord blood mononuclear cells (cbMNCs) due to adhesion to human adipose-tissue derived stromal cells (ASCs) under standard (20%) and tissue-related (5%) oxygen. ASCs efficiently maintained viability and supported further HSPC expansion at 20% and 5% O₂. During co-culture with ASCs, a new floating population of differently committed HSPCs (HSPCs-1) grew. This suspension was enriched with СD34⁺ cells up to 6 (20% O₂) and 8 (5% O₂) times. Functional analysis of HSPCs-1 revealed cobble-stone area forming cells (CAFCs) and lineage-restricted colony-forming cells (CFCs). The number of CFCs was 1.6 times higher at tissue-related O₂, than in standard cultivation (20% O₂). This increase was related to a rise in the number of multipotent precursors - BFU-E, CFU-GEMM and CFU-GM. These changes were at least partly ensured by the increased concentration of MCP-1 and IL-8 at 5% O₂. In summary, our data demonstrated that human ASCs enables the selection of functionally active HSPCs from unfractionated cbMNCs, the further expansion of which without exogenous cytokines provides enrichment with CD34⁺ cells. ASCs efficiently support the viability and proliferation of cord blood haematopoietic progenitors of different commitment at standard and tissue-related O₂ levels at the expense of direct and paracrine cell-to-cell interactions.

Predictions for optimal mitigation of paracrine inhibitory signalling in haemopoietic stem cell cultures

Introduction

Recent studies in the literature have highlighted the critical role played by cell signalling in determining haemopoietic stem cell (HSC) fate within ex vivo culture systems. Stimulatory signals can enhance proliferation and promote differentiation, whilst inhibitory signals can significantly limit culture output.

Methods

Numerical models of various mitigation strategies are presented and applied to determine effectiveness of these strategies toward mitigation of paracrine inhibitory signalling inherent in these culture systems. The strategies assessed include mixing, media-exchange, fed-batch and perfusion.

Results

The models predict that significant spatial concentration gradients exist in typical cell cultures, with important consequences for subsequent cell expansion. Media exchange is shown to be the most effective mitigation strategy, but remains labour intensive and difficult to scale-up for large culture systems. The fed-batch strategy is only effective at very small Peclet number, and its effect is diminished as the cell culture volume grows. Conversely, mixing is effective at high Peclet number, and ineffective at low Peclet number. The models predict that cell expansion in fed-batch cultures becomes independent of increasing dilution rate, consistent with experimental results previously reported in the literature. In contrast, the models predict that increasing the flow rate in perfused cultures will lead to increased cell expansion, indicating the suitability of perfusion for use as an automated, tunable strategy. The effect of initial cell seeding density is also investigated, with the model showing that perfusion outperforms dilution for all densities considered.

Conclusions

The models predict that the impact of inhibitory signalling in HSC cultures can be mitigated against using media manipulation strategies, with the optimal strategy dependent upon the protein diffusion time-scale relative to the media manipulation time-scale. The key messages from this study can be applied to any complex cell culture scenario where cell-cell interactions and paracrine signalling networks impact upon cell fate and cell expansion.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0048-7) contains supplementary material, which is available to authorized users.

CD133 allows elaborated discrimination and quantification of haematopoietic progenitor subsets in human haematopoietic stem cell transplants

The success of haematopoietic stem cell (HSC) transplantation largely depends on numbers of transplanted HSCs, which reside in the CD34(+) populations of bone marrow (BM), peripheral blood stem cells (PBSC) and umbilical cord blood (UCB). More specifically HSCs reside in the CD38(low/-) subpopulation, which cannot be objectively discriminated from mature CD34(+)  CD38(+) progenitors. Thus, better marker combinations for the quantification of more primitive haematopoietic stem and progenitor cells in transplants are required. Recently, by combining CD34 and CD133 we could clearly distinguish CD133(+)  CD34(+) multipotent and lympho-myeloid from CD133(low)  CD34(+) erythro-myeloid progenitors in UCB samples. To qualify the assessment of CD133 for routine quality control of adult HSC sources, we analysed the developmental potentials of CD133(+) and CD133(low) subpopulations in BM and PBSC. Similar to UCB, CD133 expression objectively discriminated functionally distinct subpopulations in adult HSC sources. By implementing anti-CD45RA staining, which separates multipotent (CD133(+)  CD34(+)  CD45RA(-) ) from lympho-myeloid (CD133(+)  CD34(+)  CD45RA(+) ) progenitor fractions, UCB was found to contain 2-3 times higher multipotent progenitor frequencies than BM and PBSC. To test for the consistency of CD133 expression, we compared CD133(+)  CD34(+) contents of 128 UCB samples with maternal and obstetrical factors and obtained similar correlations to related studies focusing on CD34(+) cell contents. In conclusion, implementation of anti-CD133 staining into existing routine panels will improve the quality control analyses for HSC transplants.

Evaluation of human cord blood CD34+ hematopoietic stem cell differentiation to megakaryocyte on aminated PES nanofiber scaffold compare to 2-D culture system

CONTEXT

Recently, umbilical cord blood (UCB) has been recognized as a suitable potential source of hematopoietic stem/progenitor cells (HSPCs) for transplantation. Lengthy thrombocytopenia after UCB transplantation is a major problem because of insufficient megakaryocyte (Mk) progenitors, which results in delayed platelet recovery. Frequent allogenic platelet transfusion leads to resistance to platelet units and higher risk of transmission of pathogenic agent.

OBJECTIVE

Ex vivo expansion of HSPCs and their differentiation to Mk progenitors on aminated PES nanofiber could lead to faster platelet recovery after UCB transplantation.

MATERIALS AND METHODS

CD34 cells were positively enriched using the MidiMACS system. CD34(+) cells were seeded onto conventional culture and aminated PES scaffold. The proliferation of CD34(+) cells, and also their differentiation into Mk progenitors, were evaluated. We used the flow cytometric method for analyzing CD41 and CD61 markers and real-time PCR for the expression level of transcription factors, as NF-E2 and GATA-1.

RESULTS

This study indicated increased CD34(+) cell population in aminated PES compared to the conventional system. After differentiation, the amount of CD41/CD61-expressing cells and the quantity of NF-E2 expression level increased in the aminated PES versus the 2-D system. The quantity of GATA-1 expression level was reduced on CD41/CD61(+) cells compared to CD34(+) cells, with no difference between the aminated PES and the conventional system.

DISCUSSION

Aminated PES nanofiber could have more effect on the proliferation of CD34(+) cells and Mk differentiation than the conventional culture.

CONCLUSION

Injection of the expanded cells and differentiated Mk progenitors, along with the transplantation of UCB stem cells might accelerate recovery of platelets and decrease the period of thrombocytopenia after transplantation.

Expansion and homing of umbilical cord blood hematopoietic stem and progenitor cells for clinical transplantation

The successful expansion of hematopoietic stem and progenitor cells (HSPCs) from umbilical cord blood (UCB) for transplantation could revolutionize clinical practice by improving transplantation-related outcomes and making available UCB units that have suboptimal cell doses for transplantation. New cytokine combinations appear able to promote HSPC growth with minimal differentiation into mature precursors and new agents, such as insulin-like growth factor-binding protein 2, are being used in clinical trials. Molecules that simulate the HSPC niche, such as Notch ligand, have also shown promise. Further improvements have been made with the use of mesenchymal stromal cells, which have made possible UCB expansion without a potentially deleterious prior CD34/CD133 cell selection step. Chemical molecules, such as copper chelators, nicotinamide, and aryl hydrocarbon antagonists, have shown excellent outcomes in clinical studies. The use of bioreactors could further add to HSPC studies in future. Drugs that could improve HSPC homing also appear to have potential in improving engraftment times in UCB transplantation. Technologies to expand HSPC from UCB and to enhance the homing of these cells appear to have attained the goal of accelerating hematopoietic recovery. Further discoveries and clinical studies are likely to make the goal of true HSPC expansion a reality for many applications in future.