A human stromal-based serum-free culture system supports the ex vivo expansion/maintenance of bone marrow and cord blood hematopoietic stem/progenitor cells

Activated mesenchymal stem/stromal cells promote myeloid cell differentiation via CCL2/CCR2 signaling

Myeloid cells, which originate from hematopoietic stem/progenitor cells (HSPCs), play a crucial role in mitigating infections. This study aimed to explore the impact of mesenchymal stem/stromal cells (MSCs) on the differentiation of HSPCs and progenitors through the C-C motif chemokine CCL2/CCR2 signaling pathway. Murine MSCs, identified as PDGFRα+Sca-1+ cells (PαS cells), were found to secrete CCL2, particularly in response to lipopolysaccharide stimulation. MSC-secreted CCL2 promoted the differentiation of granulocyte/macrophage progenitors into the myeloid lineage. MSC-derived CCL2 plays an important role in the early phase of myeloid cell differentiation in vivo. Single-cell RNA sequencing analysis confirmed that CCL2-mediated cell fate determination was also observed in human bone marrow cells. These findings provide valuable insights for investigating the in vivo effects of MSC transplantation.

Engineered hematopoietic and immune cells derived from human pluripotent stem cells

For the past decade, significant advances have been achieved in human hematopoietic stem cell (HSC) transplantation for treating various blood diseases and cancers. However, challenges remain with the quality control, amount, and cost of HSCs and HSC-derived immune cells. The advent of human pluripotent stem cells (hPSCs) may transform HSC transplantation and cancer immunotherapy by providing a cost-effective and scalable cell source for fundamental studies and translational applications. In this review, we discuss the current developments in the field of stem cell engineering for hematopoietic stem and progenitor cell (HSPC) differentiation and further differentiation of HSPCs into functional immune cells. The key advances in stem cell engineering include the generation of HSPCs from hPSCs, genetic modification of hPSCs, and hPSC-derived HSPCs for improved function, further differentiation of HPSCs into functional immune cells, and applications of cell culture platforms for hematopoietic cell manufacturing. Current challenges impeding the translation of hPSC-HSPCs and immune cells as well as further directions to address these challenges are also discussed.

A comprehensive analysis of cell-autonomous and non-cell-autonomous regulation of myeloid leukemic cells: The prospect of developing novel niche-targeting therapies

Leukemic cells (LCs) arise from the hematopoietic stem/and progenitor cells (HSCs/HSPCs) and utilize cues from the bone marrow microenvironment (BMM) for their regulation in the same way as their normal HSC counterparts. Mesenchymal stromal cells (MSCs), a vital component of the BMM promote leukemogenesis by creating a protective and immune-tolerant microenvironment that can support the survival of LCs, helping them escape chemotherapy, thereby resulting in the relapse of leukemia. Conversely, MSCs also induce apoptosis in the LCs and inhibit their proliferation by interfering with their self-renewal potential. This review discusses the work done so far on cell-autonomous (intrinsic) and MSCs-mediated non-cell-autonomous (extrinsic) regulation of myeloid leukemia with a special focus on the need to investigate the extrinsic regulation of myeloid leukemia to understand the contrasting role of MSCs in leukemogenesis. These mechanisms could be exploited to formulate novel therapeutic strategies that specifically target the leukemic microenvironment.

Granulocyte differentiation of rat bone marrow resident C-kit+ hematopoietic stem cells induced by mesenchymal stem cells could be considered as new option in cell-based therapy

Mesenchymal stem cells (MSCs) are effective in hematopoietic engraftment and tissue repair in stem cell transplantation. In addition, these cells control the process of hematopoiesis by secreting growth factors and cytokines. The aim of the present study is to investigate the effect of rat bone marrow (BM)-derived MSCs on the granulocyte differentiation of rat BM-resident C-kit⁺ hematopoietic stem cells (HSCs). The mononuclear cells were collected from rat BM using density gradient centrifugation and MSCs and C-kit⁺ HSCs were isolated. Then, cells were divided into two groups and differentiated into granulocytes; C-kit⁺ HSCs alone (control group) and co-cultured C-kit⁺ HSCs with MSCs (experimental group). Subsequently, the granulocyte-differentiated cells were collected and subjected to real-time PCR and Western blotting for the assessment of their telomere length (TL) and protein expressions, respectively. Afterwards, culture medium was collected to measure cytokine levels. CD34, CD16, CD11b, and CD18 granulocyte markers expression levels were significantly increased in the experimental group compared to the control group. A significant change was also observed in the protein expression of Wnt and β-catenin. In addition, MSCs caused an increase in the TL of granulocyte-differentiated cells. MSCs could affect the granulocyte differentiation of C-kit⁺ HSCs via increasing TL and Wnt/β-catenin protein expression.

Mesenchymal Stem Cells in Acquired Aplastic Anemia: The Spectrum from Basic to Clinical Utility

Aplastic anemia (AA), a rare but potentially life-threatening disease, is a paradigm of bone marrow failure syndromes characterized by pancytopenia in the peripheral blood and hypocellularity in the bone marrow. The pathophysiology of acquired idiopathic AA is quite complex. Mesenchymal stem cells (MSCs), an important component of the bone marrow, are crucial in providing the specialized microenvironment for hematopoiesis. MSC dysfunction may result in an insufficient bone marrow and may be associated with the development of AA. In this comprehensive review, we summarized the current understanding about the involvement of MSCs in the pathogenesis of acquired idiopathic AA, along with the clinical application of MSCs for patients with the disease. The pathophysiology of AA, the major properties of MSCs, and results of MSC therapy in preclinical animal models of AA are also described. Several important issues regarding the clinical use of MSCs are discussed finally. With evolving knowledge from basic studies and clinical applications, we anticipate that more patients with the disease can benefit from the therapeutic effects of MSCs in the near future.

Hypothermic Preservation of Adipose-Derived Mesenchymal Stromal Cells as a Viable Solution for the Storage and Distribution of Cell Therapy Products

Cell and gene therapies (CGT) have reached new therapeutic targets but have noticeably high prices. Solutions to reduce production costs might be found in CGT storage and transportation since they typically involve cryopreservation, which is a heavily burdened process. Encapsulation at hypothermic temperatures (e.g., 2-8 °C) could be a feasible alternative. Adipose tissue-derived mesenchymal stromal cells (MSC(AT)) expanded using fetal bovine serum (FBS)- (MSC-FBS) or human platelet lysate (HPL)-supplemented mediums (MSC-HPL) were encapsulated in alginate beads for 30 min, 5 days, and 12 days. After bead release, cell recovery and viability were determined to assess encapsulation performance. MSC identity was verified by flow cytometry, and a set of assays was performed to evaluate functionality. MSC(AT) were able to survive encapsulated for a standard transportation period of 5 days, with recovery values of 56 ± 5% for MSC-FBS and 77 ± 6% for MSC-HPL (which is a negligible drop compared to earlier timepoints). Importantly, MSC function did not suffer from encapsulation, with recovered cells showing robust differentiation potential, expression of immunomodulatory molecules, and hematopoietic support capacity. MSC(AT) encapsulation was proven possible for a remarkable 12 day period. There is currently no solution to completely replace cryopreservation in CGT logistics and supply chain, although encapsulation has shown potential to act as a serious competitor.

The upregulation of Gata transcription factors family and FOG-1 in expanded and differentiated cord blood-derived CD34+ hematopoietic stem cells to megakaryocyte lineage during co-culture with cord blood mesenchymal stem cells

BACKGROUND

Umbilical cord blood (UCB) has improved into an attractive and alternative source of allogeneic hematopoietic stem cells (all-HSCs) in clinics and, research for three decades. Recently, it has been shown that the limited cell dose of, this valuable source can be enhanced by the ex vivo expansion of cells in many, ways. We evaluated the expression of the Gata transcription factors family and FOG-1, in expanded and differentiated cord blood-derived CD34 + hematopoietic stem cells to, megakaryocytes lineage., Methods: Separated mononuclear cells were cultured in DMEM complete medium., Harvested cells as a mesenchymal stem cell at 85 % confluency were cultured with, trypsin/EDTA and in 24-well plates. The characteristic analyses of isolated UCB- MSCs, were done by flow cytometry and adipogenic, chondrogenic, and osteogenic, differentiation assays. MACS purified UCB-CD34 + hematopoietic cells cultivated and, differentiated to megakaryocyte progenitor cells in the presence of cytokine cocktail, with UCB-MSCs. Then, the GATA1, GATA2, GATA3, and FOG-1 genes expression, after differentiation to megakaryocyte progenitor cells were performed by quantitative, real-time polymerase chain reaction (PCR)., Results: In this study, the results of real-time-PCR showed that the fold change, expression of GATA-1, FOG-1, and GATA-2 genes after co-culturing with UCB-MSCs, significantly increased to 7.3, 4.7, and 3.3-fold in comparison with control groups;respectively., Conclusion: UCB-MSCs can increase the expansion and differentiation of UCBCD34 + , to megakaryocyte progenitor cells through upregulation of GATA-1, GATA-2, and FOG-1 gene expression.

Influence of the mesenchymal stromal cell source on the hematopoietic supportive capacity of umbilical cord blood-derived CD34+-enriched cells

Background

Umbilical cord blood (UCB) is a clinically relevant alternative source of hematopoietic stem/progenitor cells (HSPC). To overcome the low cell number per UCB unit, ex vivo expansion of UCB HSPC in co-culture with mesenchymal stromal cells (MSC) has been established. Bone marrow (BM)-derived MSC have been the standard choice, but the use of MSC from alternative sources, less invasive and discardable, could ease clinical translation of an expanded CD34⁺ cell product. Here, we compare the capacity of BM-, umbilical cord matrix (UCM)-, and adipose tissue (AT)-derived MSC, expanded with/without xenogeneic components, to expand/maintain UCB CD34⁺-enriched cells ex vivo.

Methods

UCB CD34⁺-enriched cells were isolated from cryopreserved mononuclear cells and cultured for 7 days over an established feeder layer (FL) of BM-, UCM-, or AT-derived MSC, previously expanded using fetal bovine serum (FBS) or fibrinogen-depleted human platelet lysate (HPL) supplemented medium. UCB cells were cultured in serum-free medium supplemented with SCF/TPO/FLT3-L/bFGF. Fold increase in total nucleated cells (TNC) as well as immunophenotype and clonogenic potential (cobblestone area-forming cells and colony-forming unit assays) of the expanded hematopoietic cells were assessed.

Results

MSC from all sources effectively supported UCB HSPC expansion/maintenance ex vivo, with expansion factors (in TNC) superior to 50x, 70x, and 80x in UCM-, BM-, and AT-derived MSC co-cultures, respectively. Specifically, AT-derived MSC co-culture resulted in expanded cells with similar phenotypic profile compared to BM-derived MSC, but resulting in higher total cell numbers. Importantly, a subpopulation of more primitive cells (CD34⁺CD90⁺) was maintained in all co-cultures. In addition, the presence of a MSC FL was essential to maintain and expand a subpopulation of progenitor T cells (CD34⁺CD7⁺). The use of HPL to expand MSC prior to co-culture establishment did not influence the expansion potential of UCB cells.

Conclusions

AT represents a promising alternative to BM as a source of MSC for co-culture protocols to expand/maintain HSPC ex vivo. On the other hand, UCM-derived MSC demonstrated inferior hematopoietic supportive capacity compared to MSC from adult tissues. Despite HPL being considered an alternative to FBS for clinical-scale manufacturing of MSC, further studies are needed to determine its impact on the hematopoietic supportive capacity of these cells.

Tailored Cytokine Optimization for ex vivo Culture Platforms Targeting the Expansion of Human Hematopoietic Stem/Progenitor Cells

Umbilical cord blood (UCB) has been established as an alternative source for hematopoietic stem/progenitor cells (HSPC) for cell and gene therapies. Limited cell yields of UCB units have been tackled with the development of cytokine-based ex vivo expansion platforms. To improve the effectiveness of these platforms, namely targeting clinical approval, in this study, we optimized the cytokine cocktails in two clinically relevant expansion platforms for HSPC, a liquid suspension culture system (CS_HSPC) and a co-culture system with bone marrow derived mesenchymal stromal cells (BM MSC) (CS_HSPC/MSC). Using a methodology based on experimental design, three different cytokines [stem cell factor (SCF), fms-like tyrosine kinase 3 ligand (Flt-3L), and thrombopoietin (TPO)] were studied in both systems during a 7-day culture under serum-free conditions. Proliferation and colony-forming unit assays, as well as immunophenotypic analysis were performed. Five experimental outputs [fold increase (FI) of total nucleated cells (FI TNC), FI of CD34+ cells, FI of erythroid burst-forming unit (BFU-E), FI of colony-forming unit granulocyte-monocyte (CFU-GM), and FI of multilineage colony-forming unit (CFU-Mix)] were followed as target outputs of the optimization model. The novel optimized cocktails determined herein comprised concentrations of 64, 61, and 80 ng/mL (CS_HSPC) and 90, 82, and 77 ng/mL (CS_HSPC/MSC) for SCF, Flt-3L, and TPO, respectively. After cytokine optimization, CS_HSPC and CS_HSPC/MSC were directly compared as platforms. CS_HSPC/MSC outperformed the feeder-free system in 6 of 8 tested experimental measures, displaying superior capability toward increasing the number of hematopoietic cells while maintaining the expression of HSPC markers (i.e., CD34+ and CD34+CD90+) and multilineage differentiation potential. A tailored approach toward optimization has made it possible to individually maximize cytokine contribution in both studied platforms. Consequently, cocktail optimization has successfully led to an increase in the expansion platform performance, while allowing a rational side-by-side comparison among different platforms and enhancing our knowledge on the impact of cytokine supplementation on the HSPC expansion process.

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.

The role of the immune system in tendon healing: a systematic review

INTRODUCTION

The role of the immune system in tendon healing relies on polymorphonucleocytes, mast cells, macrophages and lymphocytes, the 'immune cells' and their cytokine production. This systematic review reports how the immune system affects tendon healing.

SOURCES OF DATA

We registered our protocol (registration number: CRD42019141838). After searching PubMed, Embase and Cochrane Library databases, we included studies of any level of evidence published in peer-reviewed journals reporting clinical or preclinical results. The PRISMA guidelines were applied, and risk of bias and the methodological quality of the included studies were assessed. We excluded all the articles with high risk of bias and/or low quality after the assessment. We included 62 articles assessed as medium or high quality.

AREAS OF AGREEMENT

Macrophages are major actors in the promotion of proper wound healing as well as the resolution of inflammation in response to pathogenic challenge or tissue damage. The immune cells secrete cytokines involving both pro-inflammatory and anti-inflammatory factors which could affect both healing and macrophage polarization.

AREAS OF CONTROVERSY

The role of lymphocytes, mast cells and polymorphonucleocytes is still inconclusive.

GROWING POINTS

The immune system is a major actor in the complex mechanism behind the healing response occurring in tendons after an injury. A dysregulation of the immune response can ultimately lead to a failed healing response.

AREAS TIMELY FOR DEVELOPING RESEARCH

Further studies are needed to shed light on therapeutic targets to improve tendon healing and in managing new way to balance immune response.

Three-Dimensional Co-culture of Human Hematopoietic Stem/Progenitor Cells and Mesenchymal Stem/Stromal Cells in a Biomimetic Hematopoietic Niche Microenvironment

The development of cellular therapies to treat hematological malignancies has motivated researchers to investigate ex vivo culture systems capable of expanding the number of hematopoietic stem/progenitor cells (HSPC) before transplantation. The strategies exploited to achieve relevant cell numbers have relied on culture systems that lack biomimetic niche cues thought to be essential to promote HSPC maintenance and proliferation. Although stromal cells adhered to 2-D surfaces can be used to support the expansion of HSPC ex vivo, culture systems aiming to incorporate cell-cell interactions in a more intricate 3-D environment can better contribute to recapitulate the bone marrow (BM) hematopoietic niche in vitro.Herein, we describe the development of a 3-D co-culture system of human umbilical cord blood (UCB)-derived CD34⁺ cells and BM mesenchymal stem/stromal cell (MSC) spheroids in a microwell-based platform that allows to attain large numbers of spheroids with uniform sizes. Further comparison with a traditional 2-D co-culture system exploiting the supportive features of feeder layers of MSC is provided, while functional in vitro assays to assess the features of HSPC expanded in the 2-D vs. 3-D MSC co-culture systems are suggested.

Lysophosphatidic Acid and Hematopoiesis: From Microenvironmental Effects to Intracellular Signaling

Vertebrate hematopoiesis is a complex physiological process that is tightly regulated by intracellular signaling and extracellular microenvironment. In recent decades, breakthroughs in lineage-tracing technologies and lipidomics have revealed the existence of numerous lipid molecules in hematopoietic microenvironment. Lysophosphatidic acid (LPA), a bioactive phospholipid molecule, is one of the identified lipids that participates in hematopoiesis. LPA exhibits various physiological functions through activation of G-protein-coupled receptors. The functions of these LPARs have been widely studied in stem cells, while the roles of LPARs in hematopoietic stem cells have rarely been examined. Nonetheless, mounting evidence supports the importance of the LPA-LPAR axis in hematopoiesis. In this article, we have reviewed regulation of hematopoiesis in general and focused on the microenvironmental and intracellular effects of the LPA in hematopoiesis. Discoveries in these areas may be beneficial to our understanding of blood-related disorders, especially in the context of prevention and therapy for anemia.

Extracellular Vesicle-Educated Macrophages Promote Early Achilles Tendon Healing

Tendon healing follows a complex series of coordinated events, which ultimately produces a mechanically inferior tissue more scar‐like than native tendon. More regenerative healing occurs when anti‐inflammatory M2 macrophages play a more dominant role. Mesenchymal stromal/stem cells (MSCs) are able to polarize macrophages to an M2 immunophenotype via paracrine mechanisms. We previously reported that coculture of CD14+ macrophages (MQs) with MSCs resulted in a unique M2‐like macrophage. More recently, we generated M2‐like macrophages using only extracellular vesicles (EVs) isolated from MSCs creating “EV‐educated macrophages” (also called exosome‐educated macrophages [EEMs]), thereby foregoing direct use of MSCs. For the current study, we hypothesized that cell therapy with EEMs would improve in vivo tendon healing by modulating tissue inflammation and endogenous macrophage immunophenotypes. We evaluated effects of EEMs using a mouse Achilles tendon rupture model and compared results to normal tendon healing (without any biologic intervention), MSCs, MQs, or EVs. We found that exogenous administration of EEMs directly into the wound promoted a healing response that was significantly more functional and more regenerative. Injured tendons treated with exogenous EEMs exhibited (a) improved mechanical properties, (b) reduced inflammation, and (c) earlier angiogenesis. Treatment with MSC‐derived EVs alone were less effective functionally but stimulated a biological response as evidenced by an increased number of endothelial cells and decreased M1/M2 ratio. Because of their regenerative and immunomodulatory effects, EEM treament could provide a novel strategy to promote wound healing in this and various other musculoskeletal injuries or pathologies where inflammation and inadequate healing is problematic. Stem Cells2019;37:652–662

Improving hematopoietic recovery through modeling and modulation of the mesenchymal stromal cell secretome

BACKGROUND

Efficient and sustained hematopoietic recovery after hematopoietic stem cell or bone marrow transplantation is supported by paracrine signaling from specific subpopulations of mesenchymal stromal cells (MSCs). Here, we considered whether in vitro mechanopriming of human MSCs could be administered to predictively and significantly improve in vivo hematopoietic recovery after irradiation injury.

METHODS

First, we implemented regression modeling to identify eight MSC-secreted proteins that correlated strongly with improved rescue from radiation damage, including hematopoietic recovery, in a murine model of hematopoietic failure. Using these partial least squares regression (PLSR) model parameters, we then predicted recovery potential of MSC populations that were culture expanded on substrata of varying mechanical stiffness. Lastly, we experimentally validated these predictions using an in vitro co-culture model of hematopoiesis and using new in vivo experiments for the same irradiation injury model used to generate survival predictions.

RESULTS

MSCs grown on the least stiff (elastic moduli ~ 1 kPa) of these polydimethylsiloxane (PDMS) substrata secreted high concentrations of key proteins identified in regression modeling, at concentrations comparable to those secreted by minor subpopulations of MSCs shown previously to be effective in supporting such radiation rescue. We confirmed that these MSCs expanded on PDMS could promote hematopoiesis in an in vitro co-culture model with hematopoietic stem and progenitor cells (HSPCs). Further, MSCs cultured on PDMS of highest stiffness (elastic moduli ~ 100 kPa) promoted expression of CD123+ HSPCs, indicative of myeloid differentiation. Systemic administration of mechanoprimed MSCs resulted in improved mouse survival and weight recovery after bone marrow ablation, as compared with both standard MSC expansion on stiffer materials and with biophysically sorted MSC subpopulations. Additionally, we observed recovery of white blood cells, platelets, and red blood cells, indicative of complete recovery of all hematopoietic lineages.

CONCLUSIONS

These results demonstrate that computational techniques to identify MSC biomarkers can be leveraged to predict and engineer therapeutically effective MSC phenotypes defined by mechanoprimed secreted factors, for translational applications including hematopoietic recovery.

Exosomes from acellular Wharton's jelly of the human umbilical cord promotes skin wound healing

BACKGROUND

Compromised wound healing has become a global public health challenge which presents a significant psychological, financial, and emotional burden on patients and physicians. We recently reported that acellular gelatinous Wharton's jelly of the human umbilical cord enhances skin wound healing in vitro and in vivo in a murine model; however, the key player in the jelly which enhances wound healing is still unknown.

METHODS

We performed mass spectrometry on acellular gelatinous Wharton's jelly to elucidate the chemical structures of the molecules. Using an ultracentrifugation protocol, we isolated exosomes and treated fibroblasts with these exosomes to assess their proliferation and migration. Mice were subjected to a full-thickness skin biopsy experiment and treated with either control vehicle or vehicle containing exosomes. Isolated exosomes were subjected to further mass spectrometry analysis to determine their cargo.

RESULTS

Subjecting the acellular gelatinous Wharton's jelly to proteomics approaches, we detected a large amount of proteins that are characteristic of exosomes. Here, we show that the exosomes isolated from the acellular gelatinous Wharton's jelly enhance cell viability and cell migration in vitro and enhance skin wound healing in the punch biopsy wound model in mice. Mass spectrometry analysis revealed that exosomes of Wharton's jelly umbilical cord contain a large amount of alpha-2-macroglobulin, a protein which mimics the effect of acellular gelatinous Wharton's jelly exosomes on wound healing.

CONCLUSIONS

Exosomes are being enriched in the native niche of the umbilical cord and can enhance wound healing in vivo through their cargo. Exosomes from the acellular gelatinous Wharton's jelly and the cargo protein alpha-2-macroglobulin have tremendous potential as a noncellular, off-the-shelf therapeutic modality for wound healing.

Exposure of the Bone Marrow Microenvironment to Simulated Solar and Galactic Cosmic Radiation Induces Biological Bystander Effects on Human Hematopoiesis

The stem cell compartment of the hematopoietic system constitutes one of the most radiosensitive tissues of the body and leukemias represent one of the most frequent radiogenic cancers with short latency periods. As such, leukemias may pose a particular threat to astronauts during prolonged space missions. Control of hematopoiesis is tightly governed by a specialized bone marrow (BM) microenvironment/niche. As such, any environmental insult that damages cells of this niche would be expected to produce pronounced effects on the types and functionality of hematopoietic/immune cells generated. We recently reported that direct exposure of human hematopoietic stem cells (HSC) to simulated solar energetic particle (SEP) and galactic cosmic ray (GCR) radiation dramatically altered the differentiative potential of these cells, and that simulated GCR exposures can directly induce DNA damage and mutations within human HSC, which led to leukemic transformation when these cells repopulated murine recipients. In this study, we performed the first in-depth examination to define changes that occur in mesenchymal stem cells present in the human BM niche following exposure to accelerated protons and iron ions and assess the impact these changes have upon human hematopoiesis. Our data provide compelling evidence that simulated SEP/GCR exposures can also contribute to defective hematopoiesis/immunity through so-called "biological bystander effects" by damaging the stromal cells that comprise the human marrow microenvironment, thereby altering their ability to support normal hematopoiesis.

Evaluating Interaction of Cord Blood Hematopoietic Stem/Progenitor Cells with Functionally Integrated Three-Dimensional Microenvironments

Despite advances in ex vivo expansion of cord blood‐derived hematopoietic stem/progenitor cells (CB‐HSPC), challenges still remain regarding the ability to obtain, from a single unit, sufficient numbers of cells to treat an adolescent or adult patient. We and others have shown that CB‐HSPC can be expanded ex vivo in two‐dimensional (2D) cultures, but the absolute percentage of the more primitive stem cells decreases with time. During development, the fetal liver is the main site of HSPC expansion. Therefore, here we investigated, in vitro, the outcome of interactions of primitive HSPC with surrogate fetal liver environments. We compared bioengineered liver constructs made from a natural three‐dimensional‐liver‐extracellular‐matrix (3D‐ECM) seeded with hepatoblasts, fetal liver‐derived (LvSt), or bone marrow‐derived stromal cells, to their respective 2D culture counterparts. We showed that the inclusion of cellular components within the 3D‐ECM scaffolds was necessary for maintenance of HSPC viability in culture, and that irrespective of the microenvironment used, the 3D‐ECM structures led to the maintenance of a more primitive subpopulation of HSPC, as determined by flow cytometry and colony forming assays. In addition, we showed that the timing and extent of expansion depends upon the biological component used, with LvSt providing the optimal balance between preservation of primitive CB HSPC and cellular differentiation. Stem Cells Translational Medicine2018;7:271–282

Hematopoietic Niche - Exploring Biomimetic Cues to Improve the Functionality of Hematopoietic Stem/Progenitor Cells

The adult bone marrow (BM) niche is a complex entity where a homeostatic hematopoietic system is maintained through a dynamic crosstalk between different cellular and non-cellular players. Signaling mechanisms triggered by cell-cell, cell-extracellular matrix (ECM), cell-cytokine interactions, and local microenvironment parameters are involved in controlling quiescence, self-renewal, differentiation, and migration of hematopoietic stem/progenitor cells (HSPC). A promising strategy to more efficiently expand HSPC numbers and tune their properties ex vivo is to mimic the hematopoietic niche through integration of adjuvant stromal cells, soluble cues, and/or biomaterial-based approaches in HSPC culture systems. Particularly, mesenchymal stem/stromal cells (MSC), through their paracrine activity or direct contact with HSPC, are thought to be a relevant niche player, positioning HSPC-MSC co-culture as a valuable platform to support the ex vivo expansion of hematopoietic progenitors. To improve the clinical outcome of hematopoietic cell transplantation (HCT), namely when the available HSPC are present in a limited number such is the case of HSPC collected from umbilical cord blood (UCB), ex vivo expansion of HSPC is required without eliminating the long-term repopulating capacity of more primitive HSC. Here, we will focus on depicting the characteristics of co-culture systems, as well as other bioengineering approaches to improve the functionality of HSPC ex vivo.

Mesenchymal Stem Cell Benefits Observed in Bone Marrow Failure and Acquired Aplastic Anemia

Acquired aplastic anemia (AA) is a type of bone marrow failure (BMF) syndrome characterized by partial or total bone marrow (BM) destruction resulting in peripheral blood (PB) pancytopenia, which is the reduction in the number of red blood cells (RBC) and white blood cells (WBC), as well as platelets (PLT). The first-line treatment option of AA is given by hematopoietic stem cell (HSCs) transplant and/or immunosuppressive (IS) drug administration. Some patients did not respond to the treatment and remain pancytopenic following IS drugs. The studies are in progress to test the efficacy of adoptive cellular therapies as mesenchymal stem cells (MSCs), which confer low immunogenicity and are reliable allogeneic transplants in refractory severe aplastic anemia (SAA) cases. Moreover, bone marrow stromal cells (BMSC) constitute an essential component of the hematopoietic niche, responsible for stimulating and enhancing the proliferation of HSCs by secreting regulatory molecules and cytokines, providing stimulus to natural BM microenvironment for hematopoiesis. This review summarizes scientific evidences of the hematopoiesis improvements after MSC transplant, observed in acquired AA/BMF animal models as well as in patients with acquired AA. Additionally, we discuss the direct and indirect contribution of MSCs to the pathogenesis of acquired AA.

Adipose Derived Stem Cells Affect miR-145 and p53 Expressions of Co-Cultured Hematopoietic Stem Cells

OBJECTIVES

Umbilical cord blood is used for transplantation purposes in regenerative medicine of hematological disorders. MicroRNAs are important regulators of gene expression that control both physiological and pathological processes such as cancer development and incidence. There is a new relation between p53 (tumor suppressor gene) and miR-145 (suppressor of cell growth) upregulation. In this study, we have assessed how adipose-derived stem cells (ADSCs) affect the expansion of hematopoietic stem cells (HSCs), as well as miR-145 and p53 expressions.

MATERIALS AND METHODS

In this experimental study, we cultured passage-3 isolated human ADSCs as a feeder layer. Flow cytometry analysis confirmed the presence of ADSC surface markers CD73, CD90, CD105. Ex vivo cultures of cordblood CD34+ cells were cultured under the following 4 culture conditions for 7 days: i. Medium only supplemented with cytokines, ii. Culture on an ADSCs feeder layer, iii. Indirect culture on an ADSCs feeder layer (Thin Cert™ plate with a 0.4 μm pore size), and iv. Control group analyzed immediately after extraction. Real-time polymerase chain reaction (PCR) was used to determine the expressions of the p53 and miR-145 genes. Flow cytometry analysis of cells stained by annexin V and propidium iodide (PI) was performed to detect the rate of apoptosis in the expanded cells.

RESULTS

ADSCs tested positive for mesenchymal stem cell (MSC) markers CD105, CD90, and CD73, and negative for HSC markers CD34 and CD45. Our data demonstrated the differentiation potential of ASCs to osteoblasts by alizarin red and alkaline phosphatase staining. MTT assay results showed a higher proliferation rate of CD34+cells directly cultured on the ADSCs feeder layer group compared to the other groups. Direct contact between HSCs and the feeder layer was prevented by a microporous membrane p53 expression increased in the HSCs group with indirect contact of the feeder layer compared to direct contact of the feeder layer. p53 significantly downregulated in HSCs cultured on ADSCs, whereas miR-145 significantly upregulated in HSCs cultured on ADSCs.

CONCLUSIONS

ADSCs might increase HSCs proliferation and self-renewal through miR-145, p53, and their relationship.

Coexistence of aberrant hematopoietic and stromal elements in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a group of clonal hematopoietic disorders related to hematopoietic stem and progenitor cell dysfunction. Several studies have shown the role of the bone marrow microenvironment in regulating hematopoietic stem, and progenitor function and their individual abnormalities have been associated with disease pathogenesis. In this study, we simultaneously evaluated hematopoietic stem cells (HSC), hematopoietic stem progenitor cells (HSPCs) and different stromal elements in a cohort of patients with MDS-refractory cytopenia with multilineage dysplasia (RCMD). Karyotyping of these patients revealed variable chromosomal abnormalities in 73.33% of patients. Long-term HSC and lineage-negative CD34+CD38- cells were reduced while among the HPCs, there was an expansion of common myeloid progenitor and loss of granulocyte-monocyte progenitors. Interestingly, loss of HSCs was accompanied by aberrant frequencies of endothelial (ECs) (CD31+CD45-CD71-) and mesenchymal stem cells (MSCs) (CD31-CD45-71-) and its subsets associated with HSC niche. We further demonstrate down-regulation of HSC maintenance genes such as Cxcl12, VEGF in mesenchymal cells and a parallel upregulation in endothelial cells. Altogether we report for the first time quantitative and qualitative de novo changes in hematopoietic stem and its associated niche in a cohort of MDS-RCMD patients. These findings further reinforce the role of different components of the bone marrow microenvironment in MDS pathogenesis and emphasize the need for comprehensive simultaneous evaluation of all niche elements in such studies.

Stem cell manipulation, gene therapy and the risk of cancer stem cell emergence

Stem cells (SCs) have been extensively studied in the context of regenerative medicine. Human hematopoietic stem cell (HSC)-based therapies have been applied to treat leukemic patients for decades. Handling of mesenchymal stem cells (MSCs) has also raised hopes and concerns in the field of tissue engineering. Lately, discovery of cell reprogramming by Yamanaka's team has profoundly modified research strategies and approaches in this domain. As we gain further insight into cell fate mechanisms and identification of key actors and parameters, this also raises issues as to the manipulation of SCs. These include the engraftment of manipulated cells and the potential predisposition of those cells to develop cancer. As a unique and pioneer model, the use of HSCs to provide new perspectives in the field of regenerative and curative medicine will be reviewed. We will also discuss the potential use of various SCs from embryonic to adult stem cells (ASCs), including induced pluripotent stem cells (iPSCs) as well as MSCs. Furthermore, to sensitize clinicians and researchers to unresolved issues in these new therapeutic approaches, we will highlight the risks associated with the manipulation of human SCs from embryonic or adult origins for each strategy presented.

Genetically Engineered In Vitro Erythropoiesis

Background

Engineered blood has the greatest potential to combat a predicted future shortfall in the US blood supply for transfusion treatments. Engineered blood produced from hematopoietic stem cell (HSC) derived red blood cells in a laboratory is possible, but critical barriers exist to the production of clinically relevant quantities of red blood cells required to create a unit of blood. Erythroblasts have a finite expansion capacity and there are many negative regulatory mechanisms that inhibit in vitro erythropoiesis. In order to overcome these barriers and enable mass production, the expansion capacity of erythroblasts in culture will need to be exponentially improved over the current state of art. This work focused on the hypothesis that genetic engineering of HSC derived erythroblasts can overcome these obstacles.

Objectives

The objective of this research effort was to improve in vitro erythropoiesis efficiency from human adult stem cell derived erythroblasts utilizing genetic engineering. The ultimate goal is to enable the mass production of engineered blood.

Methods

HSCs were isolated from blood samples and cultured in a liquid media containing growth factors. Cells were transfected using a Piggybac plasmid transposon.

Results

Cells transfected with SPI-1 continued to proliferate in a liquid culture media. Fluorescence-activated cell sorting (FACS) analysis on culture day 45 revealed a single population of CD71⁺CD117⁺ proerythroblast cells. The results of this study suggest that genetically modified erythroblasts could be immortalized in vitro by way of a system modeling murine erythroleukemia.

Conclusion

Genetic modification can increase erythroblast expansion capacity and potentially enable mass production of red blood cells.

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.

Hematopoietic stem cells: multiparameter regulation

Hematopoietic stem cells (HSCs) are capable to self-renew with multi-potency which generated much excitement in clinical therapy. However, the main obstacle of HSCs in clinical application was insufficient number of HSCs which were derived from either bone marrow, peripheral blood or umbilical cord blood. This review briefly discusses the indispensable utility of growth factors and cytokines, stromal cells, extracellular matrix, bionic scaffold and microenvironment aiming to control the hematopoiesis in all directions and provide a better and comprehensive understanding for in vitro expansion of hematopoietic stem cells.

The Impact of Mesenchymal Stem Cells on Differentiation of Hematopoietic Stem Cells

Bone marrow microenvironment contains cellular and acellular compartments. The cellular compartment includes hematopoietic stem cells, mesenchymal stem cells and some other stromal cell types, while the acellular compartment is composed of scaffold proteins known as the extra cellular matrix. Direct cell-cell contact as well as cytokines secreted by mesenchymal stem cells during coculture of hematopoietic stem cells and mesenchymal stem cells play a critical role in hematopoiesis, and determines the fate of hematopoietic stem cells. Several studies have demonstrated the impact of mesenchymal stem cells on self-renewal, expansion, proliferation and differentiation of hematopoietic stem cells in vitro, which have shown different and contradictory results. In this paper, we will investigate the effect of mesenchymal stem cells on differentiation of hematopoietic stem cells in vitro.

Apoptosis, DAP-Kinase1 Expression and the Influences of Cytokine Milieu and Mesenchymal Stromal Cells on Ex Vivo Expansion of Umbilical Cord Blood-Derived Hematopoietic Stem Cells

Expansion of umbilical cord blood-derived CD34(+) cells can potentially provide them in numbers sufficient for clinical applications in adult humans. In this study apoptosis rate of expanded cells, mRNA expression and promoter methylation status of DAPK1 were evaluated during cord blood hematopoietic stem cell (CB-HSC) ex vivo expansion using cytokines and a co-culture system with mesenchymal stromal cells (MSCs). Ex vivo cultures of CB-HSCs were performed in three culture conditions for 14 days: cytokines with MSCs feeder layer, cytokines without MSCs feeder layer and co-culture with MSCs feeder layer without cytokine. Total number of cells, CD34(+) cells and colony forming unit assay were performed during expansion. Flow cytometric analysis by propidium iodide was performed to detection of apoptosis rate in expanded cells. Methylation status of the DAPK1 gene promoter was analyzed using methylation specific PCR, and DAPK1 mRNA expression was evaluated by real time-PCR. Maximum CB-CD34(+) cells expansion was observed in day 10 of expansion. The highest apoptosis rate was observed in cytokine culture without feeder layer that showed significant difference with co-culture condition. The data showed that ex vivo expansion of CD34(+) cells in all three culture conditions after 10 days resulted in, significant increased expression of DAPK1, also a significant difference between co-culture without cytokine and two other cytokine culture was observed (p < 0.01). DAPK1gene promoter of expanded CD34(+) cells at days 5, 10 and 14 of culture remained in unmethylated form similar to fresh CD34(+) cells. Expression of DAPK1 in hematopoietic cells was increased during 10 days expansion of CD34(+) cells. Also no methylation of DAPK1 promoter was observed; otherwise it would be capable of initiating some leukemic cell progression or disruption in hematopoietic regeneration.

Towards unravelling the kinetics of an acute myeloid leukaemia model system under oxidative and starvation stress: a comparison between two- and three-dimensional cultures

A great challenge when conducting ex vivo studies of leukaemia is the construction of an appropriate experimental platform that would recapitulate the bone marrow (BM) environment. Such a 3D scaffold system has been previously developed in our group [1]. Additionally to the BM architectural characteristics, parameters such as oxygen and glucose concentration are crucial as their value could differ between patients as well as within the same patient at different stages of treatment, consequently affecting the resistance of leukaemia to chemotherapy. The effect of oxidative and glucose stress-at levels close to human physiologic ones-on the proliferation and metabolic evolution of an AML model system (K-562 cell line) in conventional 2D cultures as well as in 3D scaffolds were studied. We observed that the K-562 cell line can proliferate and remain alive for 2 weeks in medium with glucose close to physiological levels both in 20 and 5% O2. We report interesting differences on the cellular response to the environmental, i.e., oxidative and/or nutritional stress stimuli in 2D and 3D. Higher adaptation to oxidative stress under non-starving conditions is observed in the 3D system. The glucose level in the medium has more impact on the cellular proliferation in the 3D compared to the 2D system. These differences can be of significant importance both when applying chemotherapy in vitro and also when constructing mathematical tools for optimisation of disease treatment.

Developing a co-culture system for effective megakaryo/thrombopoiesis from umbilical cord blood hematopoietic stem/progenitor cells

BACKGROUND AIMS

Platelet transfusion can be a life-saving procedure in different medical settings. Thus, there is an increasing demand for platelets, of which shelf-life is only 5 days. The efficient ex vivo biomanufacturing of platelets would allow overcoming the shortages of donated platelets.

METHODS

We exploited a two-stage culture protocol aiming to study the effect of different parameters on the megakaryo/thrombopoiesis ex vivo. In the expansion stage, human umbilical cord blood (UCB)-derived CD34(+)-enriched cells were expanded in co-culture with human bone marrow mesenchymal stromal cells (BM-MSCs). The megakaryocytic commitment and platelet generation were studied, considering the impact of exogenous addition of thrombopoietin (TPO) in the expansion stage and a cytokine cocktail (Cyt) including TPO and interleukin-3 in the differentiation stage, with the use of different culture medium formulations, and in the presence/absence of BM-MSCs (direct versus non-direct cell-cell contact).

RESULTS

Our results suggest that an early megakaryocytic commitment, driven by TPO addition during the expansion stage, further enhanced megakaryopoiesis. Importantly, the results suggest that co-culture with BM-MSCs under serum-free conditions combined with Cyt addition, in the differentiation stage, significantly improved the efficiency yield of megakaryo/thrombopoiesis as well as increasing %CD41, %CD42b and polyploid content; in particular, direct contact of expanded cells with BM-MSCs, in the differentiation stage, enhanced the efficiency yield of megakaryo/thrombopoiesis, despite inhibiting their maturation.

CONCLUSIONS

The present study established an in vitro model for the hematopoietic niche that combines different biological factors, namely, the presence of stromal/accessory cells and biochemical cues, which mimics the BM niche and enhances an efficient megakaryo/thrombopoiesis process ex vivo.

Expansion of mouse hematopoietic progenitor cells in three-dimensional cocultures on frozen-thawed stromal cell layers formed within porous scaffolds

To establish a highly efficient method of ex vivo expansion of hematopoietic cells (HCs), three-dimensional (3D) cocultures of HCs and stromal cell lines were performed using porous polymer scaffolds. Hematopoietic cells derived from mouse fetal livers were expanded by two successive cultures without the use of exogenous cytokines, namely, 3D cultures of stromal cells (DAS 104-8 cell line) to form stromal layers within the scaffolds, and, subsequently, by cocultures of the HCs on the stromal cell layers for 2 weeks. To expand the HCs more conveniently, in some experiments the stromal layers formed within the scaffolds were frozen (3D freezing) before the cocultures, then stored and applied to the cocultures after thawing. When the HCs were cocultured on the stromal layers of the DAS 104-8 cells, primitive HCs (c-kit(+) and CD34(+) cells) were expanded several fold during the cocultures. In contrast, the expansion of these primitive HCs was remarkably enhanced in the cocultures using the 3D frozen-thawed DAS 104-8 stromal layers (c-kit(+) cells > fifteenfold and CD34(+) cells > thirtyfold), and these expansions were significantly higher than those without the 3D freezing. The expansions enhanced by cocultures on the 3D frozen-thawed stromal layers were also observed in the cocultures with another stromal cell line (DAS 104-4). Because 3D frozen-thawed stromal cell lines are easy to handle, 3D coculture of HCs on frozen-thawed stromal cell lines may be an effective and convenient method for expanding primitive HCs.

Heterogeneous functions of perinatal mesenchymal stromal cells require a preselection before their banking for clinical use

Perinatal sources of mesenchymal stromal cells (MSCs) have raised growing interest because they are readily and widely available with minimal ethical/legal issues and can easily be stored for allogeneic settings. In addition, perinatal tissues are known to be important in mediating the fetomaternal tolerance of pregnancy, which confer upon perinatal-MSCs (P-MSCs) a particular interest in immunomodulation. It has been recently shown that it is possible to deeply modify the secreted factor profiles of MSCs with different cytokine stimuli such as interferon gamma or tumor necrosis factor alpha to license MSCs for a better immunosuppresive potential. Therefore, we aimed to compare adult bone marrow-MSCs with MSCs from perinatal tissues (cord blood, umbilical cord, amnion, and chorion) on their in vitro immunological and stromacytic efficiencies under different priming conditions. Our results showed that P-MSCs had a potential to modulate the in vitro immune response and be useful for hematopoietic progenitor cell ex vivo expansion. However, we showed contrasted effects of cytokine priming embedded in an important between-donor variability. In conclusion, our study highlights the importance to elaborate predicitive in vitro tests to screen between-donor variability of perinatal tissues for banking allogeneic standardized MSCs.

Proliferation extent of CD34+ cells as a key parameter to maximize megakaryocytic differentiation of umbilical cord blood-derived hematopoietic stem/progenitor cells in a two-stage culture protocol

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A two-stage protocol established aiming at effective Mk differentiation of UCB CD34⁺-enriched cells.

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Proliferation extent of CD34⁺ cells during expansion identified as a key parameter to maximize Mk differentiation.

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Morphological analysis demonstrated the characteristic features of ex-vivo generated Mks and platelet-like particles.

Co-infusion of ex-vivo generated megakaryocytic progenitors with hematopoietic stem/progenitor cells (HSC/HPC) may contribute to a faster platelet recovery upon umbilical cord blood (UCB) transplantation. A two stage protocol containing cell expansion and megakaryocyte (Mk) differentiation was established using human UCB CD34⁺-enriched cells. The expansion stage used a pre-established protocol supported by a human bone marrow mesenchymal stem cells (MSC) feeder layer and the differentiation stage used TPO (100 ng/mL) and IL-3 (10 ng/mL). 18% of culture-derived Mks had higher DNA content (>4 N) and were able to produce platelet-like particles. The proliferation extent of CD34⁺ cells obtained in the expansion stage (FI-CD34⁺), rather than expansion duration, determined as a key parameter for efficient megakaryocytic differentiation. A maximum efficiency yield (EY) of 48 ± 7.7 Mks/input CD34⁺ cells was obtained for a FI-CD34⁺ of 17 ± 2.5, where a higher FI-CD34⁺ of 42 ± 13 resulted in a less efficient megakaryocytic differentiation (EY of 22 ± 6.7 and 19 ± 4.6 %CD41).

In-vitro Behavior of Human Umbilical Cord Blood Stem Cells Towards Serum Based Minimal Cytokine Growth Conditions

We tried here to optimize the proliferation of both Hematopoietic and Mesenchymal stem cells of Umbilical Cord blood in minimal cytokine growth condition. Failing to get good results of expansion of non-adherent Hematopoietic Total Nucleated Cells and adherent Fibroblastic Mesenchymal Stem Cells derived from 10-12 ml of collected Cord blood, we designed the further experimental study by increasing the volume of Cord blood sample up to 65-70 ml. We harvested the non-adherent as well as adherent fraction separately derived from the primary culture of Umbilical Cord blood stem cells under the influence of growth promoting Cytokines or Growth Factors. The proliferation study was conducted by taking different combinations of two hematopoietic growth stimulatory Cytokines like stem cell factor (SCF) and Fms like tyrosine kinase-3Ligand (Flt3L) at concentrations (10 ng/ml, 100 ng/ml) while we preferred Mesenchymal specific growth factor i.e. basic Fibroblast growth factor (FGF-β) at its 10 ng/ml concentration for adherent cells to get optimal results. The Hematopoietic and Fibroblast Colony forming abilities of the expanded stem cells were performed through Colony Forming Unit assay. Culture Medium containing cytokine combination like SCF 100 ng/ml with Flt3L 10 ng/ml was found to be optimal for the proliferation of hematopoietic stem cells. But the number of hematopoietic colonies like Erythroid colonies generated were less in case of media supplemented with SCF & Flt3L while more number of Myeloid colonies were observed in Growth factor supplemented media in comparison to the control one. The FGF-β supplemented media successfully enhanced the proliferation of Mesenchymal Stem Cells and exhibited its efficient Fibroblast colony forming ability. Our experimental study supports the minimal utilization of cytokines for haematopoietic and mesenchymal stem cell proliferation which may help in future safe Cord blood stem cell infusion.

Expression and promoter methylation changes of the P15INK4b during ex vivo cord blood CD34+ cell expansion following co-culture with mesenchymal stromal cells

BACKGROUND

Because of the insufficient number of cord blood hematopoietic stem cells (CB-HSC), expansion of these cells seems to be important for clinical application in adults. Cell cycle inhibitors are important regulators in normal hematopoietic regeneration. In this study, mRNA expression and promoter methylation status of p15(INK4b) were evaluated during CB-HSC ex vivo expansion using cytokines and in co-culture system with a mesenchymal stem cells (MSCs) feeder layer.

METHODS

ex vivo cultures of CB-HSCs were performed in three culture conditions for 14 days: cytokines with an MSCs feeder layer, cytokines without a MSCs feeder layer, and co-culture with MSCs without cytokines. After expansion, measuring the total number of cells, CD34(+) cells, and CFU assay was performed. Methylation status of the p15(INK4b) gene promoter was analyzed using methylation-specific polymerase chain reaction and p15 mRNA expression was evaluated by real-time reverse transcriptase polymerase chain reaction.

RESULTS

Maximum CB-HSC expansion was observed on day 10 of expansion. The data showed that after 10 days, p15 mRNA expression in the expanded cells in all the three culture conditions was higher than in CD34(+) fresh cells (P < 0.01). p15 gene promoter of expanded CD34(+) cells remained in an unmethylated form just like fresh CD34(+) cells in all the three culture conditions at days 5, 10, and 14 of culture.

CONCLUSIONS

Expression of p15(INK4b) in HSCs was not decreased during ex vivo expansion. Also, no methylation of p15 promoter was observed, otherwise it would be capable of initiating some leukemic cell progression or disruption in hematopoietic regeneration.

Myelodysplastic cells in patients reprogram mesenchymal stromal cells to establish a transplantable stem cell niche disease unit

Myelodysplastic syndromes (MDSs) are a heterogeneous group of myeloid neoplasms with defects in hematopoietic stem and progenitor cells (HSPCs) and possibly the HSPC niche. Here, we show that patient-derived mesenchymal stromal cells (MDS MSCs) display a disturbed differentiation program and are essential for the propagation of MDS-initiating Lin(-)CD34(+)CD38(-) stem cells in orthotopic xenografts. Overproduction of niche factors such as CDH2 (N-Cadherin), IGFBP2, VEGFA, and LIF is associated with the ability of MDS MSCs to enhance MDS expansion. These factors represent putative therapeutic targets in order to disrupt critical hematopoietic-stromal interactions in MDS. Finally, healthy MSCs adopt MDS MSC-like molecular features when exposed to hematopoietic MDS cells, indicative of an instructive remodeling of the microenvironment. Therefore, this patient-derived xenograft model provides functional and molecular evidence that MDS is a complex disease that involves both the hematopoietic and stromal compartments. The resulting deregulated expression of niche factors may well also be a feature of other hematopoietic malignancies.

CAPE promotes the expansion of human umbilical cord blood-derived hematopoietic stem and progenitor cells in vitro

Due to the low number of collectable stem cells from single umbilical cord blood (UCB) unit, their initial uses were limited to pediatric therapies. Clinical applications of UCB hematopoietic stem and progenitor cells (HSPCs) would become feasible if there were a culture method that can effectively expand HSPCs while maintaining their self-renewal capacity. In recent years, numerous attempts have been made to expand human UCB HSPCs in vitro. In this study, we report that caffeic acid phenethyl ester (CAPE), a small molecule from honeybee extract, can promote in vitro expansion of HSPCs. Treatment with CAPE increased the percentage of HSPCs in cultured mononuclear cells. Importantly, culture of CD34(+) HSPCs with CAPE resulted in a significant increase in total colony-forming units and high proliferative potential colony-forming units. Burst-forming unit-erythroid was the mostly affected colony type, which increased more than 3.7-fold in 1 μg mL(-1) CAPE treatment group when compared to the controls. CAPE appears to induce HSPC expansion by upregulating the expression of SCF and HIF1-α. Our data suggest that CAPE may become a potent medium supplement for in vitro HSPC expansion.

New strategies in cord blood cells transplantation

For patients lacking a human leucocyte antigen-matched donor, umbilical cord blood (UCB) is an ideal, alternative source of haematopoietic stem cells (HSCs) for transplantation purposes. UCB has many advantages over bone marrow or peripheral blood taken from volunteer donors. UCB is also an important source of other stem cells, including endothelial progenitors, mesenchymal stem cells, very small embryonic/epiblast-like (VSEL) stem cells, and unrestricted somatic stem cells, which are potentially suitable for regenerative medicine. However, a significant clinical problem is that the number of HSCs in one cord-blood unit is not enough for an adult transplantation. The development of new approaches including use of multiple donors, ex vivo expansion, increasing efficiency of homing and engraftment, retrieving more cells from the placenta and cord blood is of crucial importance for the delayed engraftment after UCB transplantation. In the future, UCB will emerge as a source of cells for cellular therapies associated with tissue repair and regeneration.

Ex vivo expansion of cord blood haematopoietic stem/progenitor cells under physiological oxygen tensions: clear-cut effects on cell proliferation, differentiation and metabolism

Physiologically low O(2) tensions are believed to regulate haematopoietic stem cell (HSC) functions in the bone marrow (BM; 0-5%). In turn, placenta and umbilical cord are characterized by slightly higher physiological O(2) tensions (3-10%). We hypothesized that O(2) concentrations within this range may be exploited to augment the ex vivo expansion/maintenance of HSCs from umbilical cord (placental) blood (UCB). The expansion of UCB CD34(+) -enriched cells was studied in co-culture with BM mesenchymal stem/stromal cells (MSCs) under 2%, 5%, 10% and 21% O(2). 2% O(2) resulted in a significantly lower CD34(+) cell expansion (25-fold vs 60-, 64- and 92-fold at day 10 for 5%, 21%, 10% O(2), respectively). In turn, 10% O(2) promoted the highest CD34(+) CD90(+) cell expansion, reaching 22 ± 5.4- vs 5.6 ± 2.4- and 5.7 ± 2.0-fold for 2%, 5% and 21% O(2), respectively, after 14 days. Similar differentiation patterns were observed under different O(2) tensions, being primarily shifted towards the neutrophil lineage. Cell division kinetics revealed a higher proliferative status of cells cultured under 10% and 21% vs 2% O(2). Expectedly, higher specific glucose consumption and lactate production rates were determined at 2% O(2) when compared to higher O(2) concentrations (5-21%). Overall, these results suggest that physiological oxygen tensions, in particular 10% O(2), can maximize the ex vivo expansion of UCB stem/progenitor cells in co-culture with BM MSCs. Importantly, these studies highlight the importance of exploiting knowledge of the intricate microenvironment of the haematopoietic niche towards the definition of efficient and controlled ex vivo culture systems capable of generating large HSCs numbers for clinical applications.

Stem cell bioengineering strategies to widen the therapeutic applications of haematopoietic stem/progenitor cells from umbilical cord blood

Umbilical cord blood (UCB) transplantation has observed a significant increase in recent years, due to the unique features of UCB haematopoietic stem/progenitor cells (HSCs) for the treatment of blood-related disorders. However, the low cell numbers available per UCB unit significantly impairs the widespread use of this source for transplantation of adult patients, resulting in graft failure, delayed engraftment and delayed immune reconstitution. In order to overcome this issue, distinct approaches are now being considered in clinical trials, such as double-UCB transplantation, intrabone injection or ex vivo expansion. In this article the authors review the current state of the art, future trends and challenges on the ex vivo expansion of UCB HSCs, focusing on culture parameters affecting the yield and quality of the expanded HSC grafts: novel HSC selection schemes prior to cell culture, cytokine/growth factor cocktails, the impact of biochemical factors (e.g. O2 ) or the addition of supportive cells, e.g. mesenchymal stem/stromal cell (MSC)-based feeder layers) were addressed. Importantly, a critical challenge in cellular therapy is still the scalability, reproducibility and control of the expansion process, in order to meet the clinical requirements for therapeutic applications. Efficient design of bioreactor systems and operation modes are now the focus of many bioengineers, integrating the increasing 'know-how' on HSC biology and physiology, while complying with the GMP standards for the production of cellular products, i.e. through the use of commercially available, highly controlled, disposable technologies.

Mesenchymal stem cells induce granulocytic differentiation of acute promyelocytic leukemic cells via IL-6 and MEK/ERK pathways

All-trans retinoic acid (ATRA) induces clinical remission in most acute promyelocytic leukemia (APL) patients by inducing terminal differentiation of APL cells toward mature granulocytes. Here we report that human umbilical cord-derived mesenchymal stem cells (UC-MSCs) are capable of inducing granulocytic differentiation of the APL-derived NB4 cell line as well as primary APL cells and also cooperate with ATRA in an additive manner. Transwell coculture experiments revealed that UC-MSCs' differentiation-inducing effect was mediated through some soluble factors. Differentiation attenuation by IL-6Ra neutralization and induction by addition of exogenous IL-6 confirmed that IL-6 secreted by UC-MSCs was at least partially responsible for this differentiation induction process. Moreover, we found that UC-MSCs activated the MEK/ERK signaling pathway in promyelocytic cells and pharmacological inhibition of the MEK/ERK pathway reversed UC-MSC-induced differentiation, indicating that UC-MSCs exerted effect through activation of the MEK/ERK signaling pathway. These results demonstrate for the first time a stimulatory effect of MSCs on the differentiation of APL cells and bring a new insight into the interaction between MSCs and leukemic cells. Our data suggest that UC-MSCs/ATRA combination could be used as a novel therapeutic strategy for APL patients.