Low-dose insulin-like growth factor binding proteins 1 and 2 and angiopoietin-like protein 3 coordinately stimulate ex vivo expansion of human umbilical cord blood hematopoietic stem cells as assayed in NOD/SCID gamma null mice

Human umbilical cord mesenchymal stem cells in diabetes mellitus and its complications: applications and research advances

Diabetes mellitus and its complications pose a major threat to global health and affect the quality of life and life expectancy of patients. Currently, the application of traditional therapeutic drugs for diabetes mellitus has great limitations and can only temporarily control blood glucose but not fundamentally cure it. Mesenchymal stem cells, as pluripotent stromal cells, have multidirectional differentiation potential, high self-renewal, immune regulation, and low immunogenicity, which provide a new idea and possible development direction for diabetes mellitus treatment. Regenerative medicine with mesenchymal stem cells treatment as the core treatment will become another treatment option for diabetes mellitus after traditional treatment. Recently, human umbilical cord mesenchymal stem cells have been widely used in basic and clinical research on diabetes mellitus and its complications because of their abundance, low ethical controversy, low risk of infection, and high proliferation and differentiation ability. This paper reviews the therapeutic role and mechanism of human umbilical cord mesenchymal stem cells in diabetes mellitus and its complications and highlights the challenges faced by the clinical application of human umbilical cord mesenchymal stem cells to provide a more theoretical basis for the application of human umbilical cord mesenchymal stem cells in diabetes mellitus patients.

Ex Vivo Expansion and Homing of Human Cord Blood Hematopoietic Stem Cells

Cord blood (CB) has been proven to be an alternative source of haematopoietic stem cells (HSCs) for clinical transplantation and has multiple advantages, including but not limited to greater HLA compatibility, lower incidence of graft-versus-host disease (GvHD), higher survival rates and lower relapse rates among patients with minimal residual disease. However, the limited number of HSCs in a single CB unit limits the wider use of CB in clinical treatment. Many efforts have been made to enhance the efficacy of CB HSC transplantation, particularly by ex vivo expansion or enhancing the homing efficiency of HSCs. In this chapter, we will document the major advances regarding human HSC ex vivo expansion and homing and will also discuss the possibility of clinical translation of such laboratory work.

Isolation, Maintenance and Expansion of Adult Hematopoietic Stem/Progenitor Cells and Leukemic Stem Cells

Simple Summary

Transplantation of adult hematopoietic stem cells is an important therapeutic tool to help patients suffering from diverse hematological disorders. All types of blood cells can develop from a single hematopoietic stem cell underlining their enormous potential. Intense efforts are ongoing to generate “engraftable” human hematopoietic stem cells to treat hematopoietic diseases and to understand the molecular machinery driving them. Leukemic stem cells represent a low frequency subpopulation of leukemia cells that possess stem cell properties. They can instigate, maintain, and serially propagate leukemia in vivo, while they retain the capacity to differentiate into committed progenitors. Leukemic stem cells are unaffected by many therapeutic strategies and represent the major cause of relapse. We here describe all methods to maintain and expand murine and human hematopoietic cells in culture and describe their specific advantages. These methods are also employed to understand the biology of leukemic stem cells and to identify novel therapeutic strategies.

Abstract

Hematopoietic stem cells (HSCs) are rare, self-renewing cells that perch on top of the hematopoietic tree. The HSCs ensure the constant supply of mature blood cells in a tightly regulated process producing peripheral blood cells. Intense efforts are ongoing to optimize HSC engraftment as therapeutic strategy to treat patients suffering from hematopoietic diseases. Preclinical research paves the way by developing methods to maintain, manipulate and expand HSCs ex vivo to understand their regulation and molecular make-up. The generation of a sufficient number of transplantable HSCs is the Holy Grail for clinical therapy. Leukemia stem cells (LSCs) are characterized by their acquired stem cell characteristics and are responsible for disease initiation, progression, and relapse. We summarize efforts, that have been undertaken to increase the number of long-term (LT)-HSCs and to prevent differentiation towards committed progenitors in ex vivo culture. We provide an overview and compare methods currently available to isolate, maintain and enrich HSC subsets, progenitors and LSCs and discuss their individual advantages and drawbacks.

Differentiated Cells Derived from Hematopoietic Stem Cells and Their Applications in Translational Medicine

Hematopoietic stem cells (HSCs) and their development are one of the most widely studied model systems in mammals. In adults, HSCs are predominantly found in the bone marrow, from where they maintain homeostasis. Besides bone marrow and mobilized peripheral blood, cord blood is also being used as an alternate allogenic source of transplantable HSCs. HSCs from both autologous and allogenic sources are being applied for the treatment of various conditions like blood cancers, anemia, etc. HSCs can further differentiate to mature blood cells. Differentiation process of HSCs is being extensively studied so as to obtain a large number of pure populations of various differentiated cells in vitro so that they can be taken up for clinical trials. The ability to generate sufficient quantity of clinical-grade specialized blood cells in vitro would take the field of hematology a step ahead in translational medicine.

Platelet-activating factor induces the stemness of ovarian cancer cells via the PAF/PAFR signaling pathway

BACKGROUND

Cancer stem cells (CSCs) play an important role in tumor recurrence, metastasis, and chemoresistance. CSCs can shift between non-CSC and CSC states in certain tumor microenvironments. The mechanisms of this shift are not well understood. We previously demonstrated that platelet-activating factor (PAF), a lipid mediator of inflammation in the tumor microenvironment, can promote ovarian cancer progression and induce chemoresistance via PAF/PAFR-mediated inflammatory signaling pathways. Here, we investigated the role of PAF/PAFR signaling in the stemness of ovarian cancer cell.

METHODS

The effects of PAF and PAFR antagonists on the stemness of SKOV3 and A2780 cells were evaluated using sphere-formation assays, FACS analysis and real-time PCR in vitro and a SKOV3 tumor-formation experiment in nude mice in vivo. The potential mechanism of the PAF effect on the stemness of ovarian cancer cells was evaluated by human cytokine antibody microarray analysis.

RESULTS

PAF can promote spheroid formation and inhibit the transition of quiescent ovarian cancer cells into the cell cycle. The percentage of cancer stem cells increased significantly, and the expression of stemness genes increased in PAF-treated group. These effects could be blocked by PAFR inhibitors. Ginkgolide B (GB) inhibited tumor growth and decreased the CSC percentage in vivo. Human cytokine antibody microarray analysis showed that some stemness-maintaining proteins increased in PAF-treated group.

CONCLUSION

Our results suggest that PAF can regulate the stemness of ovarian cancer cells through the PAF/PAFR pathway, suggesting a new target for the treatment of ovarian cancer.

Spatial and biochemical interactions between bone marrow adipose tissue and hematopoietic stem and progenitor cells in rhesus macaques

Recent developments in in situ microscopy have enabled unparalleled resolution of the architecture of the bone marrow (BM) niche for murine hematopoietic stem and progenitor cells (HSPCs). However, the extent to which these observations can be extrapolated to human BM remains unknown. In humans, adipose tissue occupies a significant portion of the BM medullary cavity, making quantitative immunofluorescent analysis difficult due to lipid-mediated light scattering. In this study, we employed optical clearing, confocal microscopy and nearest neighbor analysis to determine the spatial distribution of CD34+ HSPCs in the BM in a translationally relevant rhesus macaque model. Immunofluorescent analysis revealed that femoral BM adipocytes are associated with the branches of vascular sinusoids, with half of HSPCs localizing in close proximity of the nearest BM adipocyte. Immunofluorescent microscopy and flow cytometric analysis demonstrate that BM adipose tissue exists as a multicellular niche consisted of adipocytes, endothelial cells, granulocytes, and macrophages. Analysis of BM adipose tissue conditioned media using liquid chromatography-tandem mass spectrometry revealed the presence of multiple bioactive proteins involved in regulation of hematopoiesis, inflammation, and bone development, with many predicted to reside inside microvesicles. Pretreatment of purified HSPCs with BM adipose tissue conditioned media, comprising soluble and exosomal/microvesicle-derived factors, led to enhanced proliferation and an increase in granulocyte-monocyte differentiation potential ex vivo. Our work extends extensive studies in murine models, indicating that BM adipose tissue is a central paracrine regulator of hematopoiesis in nonhuman primates and possibly in humans.

Roles of angiopoietin-like proteins in regulation of stem cell activity

Various types of stem cells reside in the body and self-renew throughout an organism's lifetime. Such self-renewal is essential for maintenance of tissue homeostasis and is co-ordinately regulated by stem cell-intrinsic signals and signals from stem cell niche. Angiopoietin is a niche-derived signalling molecule well known to contribute to maintenance of haematopoietic stem cells (HSCs). Angiopoietin-like proteins (ANGPTLs) are structurally similar to angiopoietin, and recent studies reveal that they function in angiogenesis, lipid and energy metabolism and regulation of inflammation. However, unlike angiopoietins, activities of ANGPTLs in stem cell maintenance have remained unclear. Recently, several studies have reported an association of ANGPTL signalling with stem cell maintenance. Here, we summarize those findings with a focus on HSCs, intestinal stem cells, neural stem cells and cancer stem cells and discuss mechanisms underlying ANGPTL-mediated stem cell maintenance.

Effect of combined sublethal X-ray irradiation and cyclosporine A treatment in NOD scid gamma (NSG) mice

Cyclosporine A (CsA) is used in hematopoietic stem cell transplantations (HSCT) to prevent graft-versus-host disease (GvHD). GvHD is the most severe side effect of allogeneic HSCT and efficient therapies are lacking. Mouse models are an essential tool for assessing potential new therapeutic strategies. Our aim is to mimic a clinical setting as close as possible using CsA treatment after sublethal irradiation in NSG mice and thereby evaluate the feasibility of this mouse model for GvHD studies. The effect of CsA (7.5 mg/kg body weight) on sublethally X-ray irradiated (2 Gy) and non-irradiated NSG mice was tested. CsA was administered orally every twelve hours for nine days. Animals irradiated and treated with CsA showed a shorter survival (n=3/10) than irradiated animals treated with NaCl (n=10/10). Furthermore, combined therapy resulted in severe weight loss (82 ± 6% of initial weight, n=7, day 8), with weight recovery after the CsA application was ceased. A high number of apoptotic events in the liver was observed in these mice (0.431 ± 0.371 apoptotic cells/cm², n=2, compared to 0.027 ± 0.034 apoptotic cells/cm², n=5, in the non-irradiated group). Other adverse effects, including a decrease in white blood cell counts were non-CsA-specific manifestations of irradiation. The combination of CsA treatment with irradiation has a hepatotoxic and lethal effect on NSG mice, whereas the treatment without irradiation is tolerated. Therefore, when using in vivo models of GvHD in NSG mice, a combined treatment with CsA and X-ray irradiation should be avoided or carefully evaluated.

ANGPTL3: a novel biomarker and promising therapeutic target

Angiopoietin-like protein 3 (ANGPTL3) belongs to a multifunctional secreted protein that mainly expresses in the liver, and is regulated by numerous post-translational modifications, including multiple cleavage and glycosylation. Accumulating evidences have revealed that ANGPTL3 plays a critical role in both biological processes, such as lipid metabolism, angiogenesis and haematopoietic function and pathological changes, including atherosclerosis, carcinogenesis, nephrotic syndrome, diabetes, liver diseases and so on. Thus, ANGPTL3 may serve as a potential biomarker in these diseases. Furthermore, ANGPTL3 signalling pathways including LXR/ANGPTL3, thyroid hormone/ANGPTL3, insulin/ANGPTL3 and leptin/ANGPTL3 are also involved in physiological and pathological processes. Some biological ANGPTL3 inhibitors, chemical drugs and traditional Chinese medicine exert beneficial effects by targeting ANGPTL3 directly or indirectly. Therefore, elucidating the effects and underlying mechanisms of ANGPTL3 is essential to develop promising strategies in the diagnosis and treatment of related diseases.

Inflammation-Associated Cytokines IGFBP1 and RANTES Impair the Megakaryocytic Potential of HSCs in PT Patients after Allo-HSCT

Prolonged isolated thrombocytopenia (PT) is a severe complication in patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Whether the megakaryoctic potential of hematopoietic stem cells (HSCs) in bone marrow is intact and what factors drive the pathological process of PT remain elusive. A retrospective study in patients (n = 285) receiving HSCT revealed that the occurrence of PT was approximately 8% and the number of platelets and megakaryocytes in PT patients is much lower compared with control subjects. To test whether the deficiency of thrombopoiesis was caused by the activities of HSCs, the megakaryocytic differentiation potential of HSCs before or after transplantation was assessed. Interestingly, a substantial decrease of megakaryocytic differentiation was observed 2 weeks after transplantation of HSCs in all of the allo-HSCT recipients. However, 4 weeks after transplantation, the ability of HSCs to generate CD41⁺CD42b⁺ megakaryocytes in successful platelet engraftment patients recovered to the same level as those of HSCs before implantation. In contrast, HSCs derived from PT patients throughout the postimplantation period exhibited poor survival and failed to differentiate properly. A protein array analysis demonstrated that multiple inflammation-associated cytokines were elevated in allo-HSCT recipients with PT. Among them, insulin-like growth factor-binding protein 1 and regulated on activation, normal T cell expressed and secreted were found to significantly suppress the proliferation and megakaryocytic differentiation of HSCs in vitro. Our results suggested that the occurrence of PT may be attributed, at least partially, to the damage to HSC function caused by inflammation-associated cytokines after HSCT. These findings shed light on the mechanism underlying HSC megakaryocytic differentiation in PT patients and may provide potential new strategies for treating PT patients after HSCT.

Spheroid Coculture of Hematopoietic Stem/Progenitor Cells and Monolayer Expanded Mesenchymal Stem/Stromal Cells in Polydimethylsiloxane Microwells Modestly Improves In Vitro Hematopoietic Stem/Progenitor Cell Expansion

While two-dimensional (2D) monolayers of mesenchymal stem/stromal cells (MSCs) have been shown to enhance hematopoietic stem/progenitor cell (HSPC) expansion in vitro, expanded cells do not engraft long term in human recipients. This outcome is attributed to the failure of 2D culture to recapitulate the bone marrow (BM) niche signal milieu. Herein, we evaluated the capacity of a novel three-dimensional (3D) coculture system to support HSPC expansion in vitro. A high-throughput polydimethylsiloxane (PDMS) microwell platform was used to manufacture thousands of uniform 3D multicellular coculture spheroids. Relative gene expression in 3D spheroid versus 2D adherent BM-derived MSC cultures was characterized and compared with literature reports. We evaluated coculture spheroids, each containing 25-400 MSCs and 10 umbilical cord blood (CB)-derived CD34⁺ progenitor cells. At low exogenous cytokine concentrations, 2D and 3D MSC coculture modestly improved overall hematopoietic cell and CD34⁺ cell expansion outcomes. By contrast, a substantial increase in CD34⁺CD38^- cell yield was observed in PDMS microwell cultures, regardless of the presence or absence of MSCs. This outcome indicated that CD34⁺CD38^- cell culture yield could be increased using the microwell platform alone, even without MSC coculture support. We found that the increase in CD34⁺CD38^- cell yield observed in PDMS microwell cultures did not translate to enhanced engraftment in NOD/SCID gamma (NSG) mice or a modification in the relative human hematopoietic lineages established in engrafted mice. In summary, there was no statistical difference in CD34⁺ cell yield from 2D or 3D cocultures, and MSC coculture support provided only modest benefit in either geometry. While the high-throughput 3D microwell platform may provide a useful model system for studying cells in coculture, further optimization will be required to generate HSPC yields suitable for use in clinical applications.

3D models of the hematopoietic stem cell niche under steady-state and active conditions

Hematopoietic stem cells (HSCs) in the bone marrow are able to differentiate into all types of blood cells and supply the organism each day with billions of fresh cells. They are applied to cure hematological diseases such as leukemia. The clinical need for HSCs is high and there is a demand for being able to control and multiply HSCs in vitro. The hematopoietic system is highly proliferative and thus sensitive to anti-proliferative drugs such as chemotherapeutics. For many of these drugs suppression of the hematopoietic system is the dose-limiting toxicity. Therefore, biomimetic 3D models of the HSC niche that allow to control HSC behavior in vitro and to test drugs in a human setting are relevant for the clinics and pharmacology. Here, we describe a perfused 3D bone marrow analog that allows mimicking the HSC niche under steady-state and activated conditions that favor either HSC maintenance or differentiation, respectively, and allows for drug testing.

Impact of osteoblast maturation on their paracrine growth enhancing activity on cord blood progenitors

BACKGROUND

Osteoblasts possess strong growth modulatory activity on haematopoietic stem cells and progenitors. We sought to characterise the growth and differentiation modulatory activities of human osteoblasts at distinct stages of maturation on cord blood (CB) progenitors in the context of osteoblast conditioned medium (OCM).

METHODS

OCM was produced from MSC-derived osteoblasts (M-OST) at distinct stages of maturation. The growth modulatory activities of the OCM were tested on CB CD34⁺ cells using different functional assays.

RESULTS

OCMs raised the growth of CB cells and expansion of CD34⁺ cells independently of the maturation status of M-OST. However, productions of immature CB cells including committed and multipotent progenitors were superior with OCM produced with immature osteoblasts. Osteogenic differentiation was accompanied by the upregulation of IGFBP-2, by several members of the Angpt-L family of growth factor, and by the Notch ligands Dll-1 and Dll-4. However, the growth activity of OCM and the in vivo engraftment properties of OCM-expanded CB cells were retained after IGFBP-2 neutralisation. Similarly, OCM-mediated expansion of CB myeloid progenitors was largely independent of Notch signalling.

CONCLUSIONS

These results demonstrate that immature osteoblasts possess greater regulatory activity over haematopoietic progenitors, and that this activity is not entirely dependent on Notch signalling.

Clinical Studies of Ex Vivo Expansion to Accelerate Engraftment After Umbilical Cord Blood Transplantation: A Systematic Review

Cell dose limits greater use of umbilical cord blood (UCB) in hematopoietic cell transplantation. The clinical benefits of ex vivo expansion need clarity to understand its potential impact. A systematic search of studies addressing UCB ex vivo expansion was conducted. Fifteen clinical studies (349 transplanted patients) and 13 registered trials were identified. The co-infusion of an expanded unit and a second unmanipulated unit (8 studies), the fractional expansion of 12% to 60% of a single unit (5 studies), and the infusion of a single expanded unit (2 studies) were reported. More recently, published studies and 12 of 13 ongoing trials involve the use of novel small molecules in addition to traditional cytokine cocktails. Higher total cell number was closely associated with faster neutrophil engraftment. Compared with historical controls, neutrophil engraftment was significantly accelerated in more recent studies using small molecules or mesenchymal stromal cells (MSC) co-culture, and in some cases, platelet recovery was also statistically improved. Recent studies using nicotinamide and StemRegenin-1 reported long-term chimerism of the expanded unit. No significant improvement in survival or other transplant-related outcomes was demonstrated for any of the strategies. Ex vivo expansion of UCB can accelerate initial neutrophil engraftment after transplant. More recent studies suggest that long-term engraftment of ex vivo expanded cord blood units is achievable. Results of larger randomized controlled trials are needed to understand the impact on patient outcomes and health care costs.

Endothelial Cells Promote Expansion of Long-Term Engrafting Marrow Hematopoietic Stem and Progenitor Cells in Primates

Successful expansion of bone marrow (BM) hematopoietic stem and progenitor cells (HSPCs) would benefit many HSPC transplantation and gene therapy/editing applications. However, current expansion technologies have been limited by a loss of multipotency and self-renewal properties ex vivo. We hypothesized that an ex vivo vascular niche would provide prohematopoietic signals to expand HSPCs while maintaining multipotency and self-renewal. To test this hypothesis, BM autologous CD34⁺ cells were expanded in endothelial cell (EC) coculture and transplanted in nonhuman primates. CD34⁺ C38^- HSPCs cocultured with ECs expanded up to 17-fold, with a significant increase in hematopoietic colony-forming activity compared with cells cultured with cytokines alone (colony-forming unit-granulocyte-erythroid-macrophage-monocyte; p < .005). BM CD34⁺ cells that were transduced with green fluorescent protein lentivirus vector and expanded on ECs engrafted long term with multilineage polyclonal reconstitution. Gene marking was observed in granulocytes, lymphocytes, platelets, and erythrocytes. Whole transcriptome analysis indicated that EC coculture altered the expression profile of 75 genes in the BM CD34⁺ cells without impeding the long-term engraftment potential. These findings show that an ex vivo vascular niche is an effective platform for expansion of adult BM HSPCs. Stem Cells Translational Medicine 2017;6:864-876.

Human Lung Spheroids as In Vitro Niches of Lung Progenitor Cells with Distinctive Paracrine and Plasticity Properties

Basic and translational research on lung biology has discovered multiple progenitor cell types, specialized or facultative, responsible for turnover, renewal, and repair. Isolation of populations of resident lung progenitor cells (LPCs) has been described by multiple protocols, and some have been successfully applied to healthy human lung tissue. We aimed at understanding how different cell culture conditions may affect, in vitro, the phenotype of LPCs to create an ideal niche‐like microenvironment. The influence of different substrates (i.e., fibronectin, gelatin, laminin) and the impact of a three‐dimensional/two‐dimensional (3D/2D) culture switch on the biology of LPCs isolated as lung spheroids (LSs) from normal adult human lung biopsy specimens were investigated. We applied a spheroid culture system as the selective/inductive step for progenitor cell culture, as described in many biological systems. The data showed a niche‐like proepithelial microenvironment inside the LS, highly sensitive to the 3D culture system and significantly affecting the phenotype of adult LPCs more than culture substrate. LSs favor epithelial phenotypes and LPC maintenance and contain cells more responsive to specific commitment stimuli than 2D monolayer cultures, while secreting a distinctive set of paracrine factors. We have shown for the first time, to our knowledge, how culture as 3D LSs can affect LPC epithelial phenotype and produce strong paracrine signals with a distinctive secretomic profile compared with 2D monolayer conditions. These findings suggest novel approaches to maintain ex vivo LPCs for basic and translational studies. Stem Cells Translational Medicine2017;6:767–777

An Overview on Human Umbilical Cord Blood Stem Cell-Based Alternative In Vitro Models for Developmental Neurotoxicity Assessment

The developing brain is found highly vulnerable towards the exposure of different environmental chemicals/drugs, even at concentrations, those are generally considered safe in mature brain. The brain development is a very complex phenomenon which involves several processes running in parallel such as cell proliferation, migration, differentiation, maturation and synaptogenesis. If any step of these cellular processes hampered due to exposure of any xenobiotic/drug, there is almost no chance of recovery which could finally result in a life-long disability. Therefore, the developmental neurotoxicity (DNT) assessment of newly discovered drugs/molecules is a very serious concern among the neurologists. Animal-based DNT models have their own limitations such as ethical concerns and lower sensitivity with less predictive values in humans. Furthermore, non-availability of human foetal brain tissues/cells makes job more difficult to understand about mechanisms involve in DNT in human beings. Although, the use of cell culture have been proven as a powerful tool for DNT assessment, but many in vitro models are currently utilizing genetically unstable cell lines. The interpretation of data generated using such terminally differentiated cells is hard to extrapolate with in vivo situations. However, human umbilical cord blood stem cells (hUCBSCs) have been proposed as an excellent tool for alternative DNT testing because neuronal development from undifferentiated state could exactly mimic the original pattern of neuronal development in foetus when hUCBSCs differentiated into neuronal cells. Additionally, less ethical concern, easy availability and high plasticity make them an attractive source for establishing in vitro model of DNT assessment. In this review, we are focusing towards recent advancements on hUCBSCs-based in vitro model to understand DNTs.

Angiopoietin-like proteins stimulate HSPC development through interaction with notch receptor signaling

Angiopoietin-like proteins (angptls) are capable of ex vivo expansion of mouse and human hematopoietic stem and progenitor cells (HSPCs). Despite this intriguing ability, their mechanism is unknown. In this study, we show that angptl2 overexpression is sufficient to expand definitive HSPCs in zebrafish embryos. Angptl1/2 are required for definitive hematopoiesis and vascular specification of the hemogenic endothelium. The loss-of-function phenotype is reminiscent of the notch mutant mindbomb (mib), and a strong genetic interaction occurs between angptls and notch. Overexpressing angptl2 rescues mib while overexpressing notch rescues angptl1/2 morphants. Gene expression studies in ANGPTL2-stimulated CD34(+) cells showed a strong MYC activation signature and myc overexpression in angptl1/2 morphants or mib restored HSPCs formation. ANGPTL2 can increase NOTCH activation in cultured cells and ANGPTL receptor interacted with NOTCH to regulate NOTCH cleavage. Together our data provide insight to the angptl-mediated notch activation through receptor interaction and subsequent activation of myc targets.

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.