Human haemato-endothelial precursors: cord blood CD34+ cells produce haemogenic endothelium

Spatiotemporal expression profiles of c-Mpl mRNA in the tooth germ: Comparative expression dynamics of vascularization-related genes

BACKGROUND

Vascularization is an essential event for both embryonic organ development and tissue repair in adults. During mouse tooth development, endothelial cells migrate into dental papilla during the cap stage, and form blood vessels through angiogenesis. Megakaryocytes and/or platelets, as other hematopoietic cells, express angiogenic molecules and can promote angiogenesis in adult tissues. However, it remains unknown which cells are responsible for attracting and leading blood vessels through the dental papilla during tooth development.

METHODS

Here we analyzed the spatiotemporal expression of c-Mpl mRNA in developing molar teeth of fetal mice. Expression patterns were then compared with those of several markers of hematopoietic cells as well as of angiogenic elements including CD41, erythropoietin receptor, CD34, angiopoietin-1 (Ang-1), Tie-2, and vascular endothelial growth factor receptor2 (VEGFR2) through in situ hybridization or immunohistochemistry.

RESULTS

Cells expressing c-Mpl mRNA was found in several parts of the developing tooth germ, including the peridental mesenchyme, dental papilla, enamel organ, and dental lamina. This expression occurred in a spatiotemporally controlled fashion. CD41-expressing cells were not detected during tooth development. The spatiotemporal expression pattern of c-Mpl mRNA in the dental papilla was similar to that of Ang-1, which preceded invasion of endothelial cells. Eventually, at the early bell stage, the c-Mpl mRNA signal was detected in morphologically differentiating odontoblasts that accumulated in the periphery of the dental papilla along the inner enamel epithelium layer of the future cusp region.

CONCLUSION

During tooth development, several kinds of cells express c-Mpl mRNA in a spatiotemporally controlled fashion, including differentiating odontoblasts. We hypothesize that c-Mpl-expressing cells appearing in the forming dental papilla at the cap stage are odontoblast progenitor cells that migrate to the site of odontoblast differentiation. There they attract vascular endothelial cells into the forming dental papilla and lead cells toward the inner enamel epithelium layer through production of angiogenic molecules (e.g., Ang-1) during migration to the site of differentiation. C-Mpl may regulate apoptosis and/or proliferation of expressing cells in order to execute normal development of the tooth.

Cells coexpressing both myeloid and endothelial markers are detectable in the spleen and bone marrow of patients with primary myelofibrosis

Different bodies of evidence support the existence of a common origin of hematopoietic and endothelial lineages; moreover, recent studies have indicated the presence of a hemogenic endothelium and a common hemato-endothelial precursor both in the embryo and in the cord blood. Conversely, to our knowledge, there is no evidence of such bipotential cells in human postnatal tissues or blood. In this study, we investigated the presence and phenotype of "transitional" cells in different tissues of patients with primary myelofibrosis (PMF). Using confocal microscopy and flow cytometry, we identified a rare cell population in the bone marrow and spleen of patients with PMF, which coexpresses the endothelial marker CD144 (vascular endothelial (VE)-cadherin), the pan-hematopoietic marker CD45, the early myeloid marker CD33, and CD34, a common endothelial and hematopoietic antigen.

Chrysin promotes angiogenesis in rat hindlimb ischemia: Impact on PI3K/Akt/mTOR signaling pathway and autophagy

Limb ischemia occurs due to obstruction of blood perfusion to lower limbs, a manifestation that is associated with peripheral artery disease (PAD). Angiogenesis is important for adequate oxygen delivery. The present study investigated a potential role for chrysin, a naturally occurring flavonoid, in promoting angiogenesis in hindlimb ischemia (HLI) rat model. Rats were allocated into four groups: (1) sham-operated control, (2) HLI: subjected to unilateral femoral artery ligation, (3) HLI + chrysin: received 100 mg/kg, i.p. chrysin immediately after HLI, and (4) HLI + chrysin + rapamycin: received 6 mg/kg/day rapamycin i.p. for 5 days then subjected to HLI and dosed with 100 mg/kg chrysin, i.p. Rats were killed 18 h later and gastrocnemius muscles were collected and divided into parts for (1) immunohistochemistry detection of CD31 and CD105, (2) qRT-PCR analysis of eNOS and VEGFR2, (3) colorimetric analysis of NO, (4) ELISA estimation of TGF-β, VEGF, ATG5 and Beclin-1, and (5) Western blot analysis of p-PI3K, PI3K, p-Akt, Akt, p-mTOR, mTOR, and HIF-1α. Chrysin significantly enhanced microvessels growth in HLI muscles as indicated by increased CD31 and CD105 levels and decreased TGF-β. Chrysin's proangiogenic effect is potentially mediated by increased VEGF, VEGFR2 and activation of PI3K/AKT/mTOR pathway, which promoted eNOS and NO levels as it was reversed by the mTOR inhibitor, rapamycin. Chrysin also inhibited autophagy as it decreased ATG5 and Beclin-1. The current study shows that chrysin possesses a proangiogenic effect in HLI rats and might be useful in patients with PAD.

Mesenchymal Stem Cells Derived from Umbilical Cord Blood having Excellent Stemness Properties with Therapeutic Benefits - a New Era in Cancer Treatment

Mesenchymal stem cells (MSCs) are the most promising candidates for cellular therapies, and most therapeutic applications have focused on MSCs produced from adult bone marrow, despite mounting evidence that MSCs are present in a wide range of conditions. Umbilical cord blood (UCB) is a valuable source of hematopoietic stem cells, but its therapeutic potential extends beyond the hematopoietic component, which also suggests solid organ regenerative potential. With potential ranging from embryonic-like to lineage-committed progenitor cells, many different stems and progenitor cell populations have been postulated. MSC is currently inferred by numerous clinical applications for human UCB. aAs stem cell therapy kicks off some new research and these cells show such a boon to stem cell therapy, it is nevertheless characteristic that the prospect of UCB conservation is gaining momentum. Taken together, the experience described here shows that MSCs derived from UCB are seen as attractive therapeutic candidates for various human disorders including cancer. It is argued that a therapeutic stem cell transplant, using stem cells from UCB, provides a reliable repository of early precursor cells that can be useful in a large number of different conditions, considering issues of safety, availability, transplant methodology, rejection, and side effects. In particular, we focus on the concept of isolation and expansion, comparing the phenotype with MSC derived from the UCB, describing the ability to differentiate, and lastly, the therapeutic potential concerning stromal support, stemness characteristic, immune modulation, and cancer stem cell therapy. Thus it is an overview of the therapeutic application of UCB derived MSCs, with a special emphasis on cancer. Besides, the current evidence on the double-edged sword of MSCs in cancer treatment and the latest advances in UCB-derived MSC in cancer research will be discussed.

Targeting RUNX1 as a novel treatment modality for pulmonary arterial hypertension

AIMS

Pulmonary arterial hypertension (PAH) is a fatal disease without a cure. Previously, we found that transcription factor RUNX1-dependent haematopoietic transformation of endothelial progenitor cells may contribute to the pathogenesis of PAH. However, the therapeutic potential of RUNX1 inhibition to reverse established PAH remains unknown. In the current study, we aimed to determine whether RUNX1 inhibition was sufficient to reverse Sugen/hypoxia (SuHx)-induced pulmonary hypertension (PH) in rats. We also aimed to demonstrate possible mechanisms involved.

METHODS AND RESULTS

We administered a small molecule specific RUNX1 inhibitor Ro5-3335 before, during, and after the development of SuHx-PH in rats to investigate its therapeutic potential. We quantified lung macrophage recruitment and activation in vivo and in vitro in the presence or absence of the RUNX1 inhibitor. We generated conditional VE-cadherin-CreERT2; ZsGreen mice for labelling adult endothelium and lineage tracing in the SuHx-PH model. We also generated conditional Cdh5-CreERT2; Runx1(flox/flox) mice to delete Runx1 gene in adult endothelium and LysM-Cre; Runx1(flox/flox) mice to delete Runx1 gene in cells of myeloid lineage, and then subjected these mice to SuHx-PH induction. RUNX1 inhibition in vivo effectively prevented the development, blocked the progression, and reversed established SuHx-induced PH in rats. RUNX1 inhibition significantly dampened lung macrophage recruitment and activation. Furthermore, lineage tracing with the inducible VE-cadherin-CreERT2; ZsGreen mice demonstrated that a RUNX1-dependent endothelial to haematopoietic transformation occurred during the development of SuHx-PH. Finally, tissue-specific deletion of Runx1 gene either in adult endothelium or in cells of myeloid lineage prevented the mice from developing SuHx-PH, suggesting that RUNX1 is required for the development of PH.

CONCLUSION

By blocking RUNX1-dependent endothelial to haematopoietic transformation and pulmonary macrophage recruitment and activation, targeting RUNX1 may be as a novel treatment modality for pulmonary arterial hypertension.

Regulation of Hemogenic Endothelial Cell Development and Function

Embryonic definitive hematopoiesis generates hematopoietic stem and progenitor cells (HSPCs) essential for establishment and maintenance of the adult blood system. This process requires the specification of a subset of vascular endothelial cells to become blood-forming, or hemogenic, and the subsequent endothelial-to-hematopoietic transition to generate HSPCs therefrom. The mechanisms that regulate these processes are under intensive investigation, as their recapitulation in vitro from human pluripotent stem cells has the potential to generate autologous HSPCs for clinical applications. In this review, we provide an overview of hemogenic endothelial cell development and highlight the molecular events that govern hemogenic specification of vascular endothelial cells and the generation of multilineage HSPCs from hemogenic endothelium. We also discuss the impact of hemogenic endothelial cell development on adult hematopoiesis.

Early Human Hemogenic Endothelium Generates Primitive and Definitive Hematopoiesis In Vitro

The differentiation of human embryonic stem cells (hESCs) to hematopoietic lineages initiates with the specification of hemogenic endothelium, a transient specialized endothelial precursor of all blood cells. This in vitro system provides an invaluable model to dissect the emergence of hematopoiesis in humans. However, the study of hematopoiesis specification is hampered by a lack of consensus in the timing of hemogenic endothelium analysis and the full hematopoietic potential of this population. Here, our data reveal a sharp decline in the hemogenic potential of endothelium populations isolated over the course of hESC differentiation. Furthermore, by tracking the dynamic expression of CD31 and CD235a at the onset of hematopoiesis, we identified three populations of hematopoietic progenitors, representing primitive and definitive subsets that all emerge from the earliest specified hemogenic endothelium. Our data establish that hemogenic endothelium populations endowed with primitive and definitive hematopoietic potential are specified simultaneously from the mesoderm in differentiating hESCs.

Building Blood Vessels with Vascular Progenitor Cells

Vascular progenitor cells have been identified from perivascular cell fractions and peripheral blood and bone marrow mononuclear fractions. These vascular progenitors share the ability to generate some of the vascular lineages, including endothelial cells, smooth muscle cells, and pericytes. The potential therapeutic uses for vascular progenitor cells are broad and relate to stroke, ischemic disease, and to the engineering of whole organs and tissues that require a vascular component. This review summarizes the best-characterized sources of vascular progenitor cells and discusses advances in 3D printing and electrospinning using blended polymers for the creation of biomimetic vascular grafts. These advances are pushing the field of regenerative medicine closer to the creation of small-diameter vascular grafts with long-term clinical utility.

Behavior of multipotent stem cells isolated in mobilized peripheral blood from sheep after culture with human chondrogenic medium

Today, regenerative medicine requires new sources of multipotent stem cells for their differentiation to chondrocytes using the mediums of differentiation available in the market. This study aimed to determine whether the Mesenchymal Stem Cells (MSCs) isolated from Mobilized Peripheral Blood (MPB) in sheep using the Granulocyte Colony-Stimulating Factor (G-CSF), have the ability of first acquire a fibroblast-like morphology after being forced out of the bone marrow niche by G-CSF and second, if the cells have the capacity to express collagen type-II α I in primary culture using a human commercial media of differentiation. Six Suffolk male sheep with age of 2 years were mobilized using G-CSF. One subcutaneous injection of 10 mcg per kilogram of bodyweight were administered every 24 h during three consecutive days. At day four, a sample of 20 mL of peripheral blood was harvested, afterwards, monocytes cells were separated by ficoll gradient. The mobilized MSCs were expanded in primary culture in DMEM medium supplemented with 10% adult sheep serum for three weeks and characterized by an antibody panel for surface markers: CD105, CD90, CD73, CD34, and CD45, before and after primary culture. Subsequently, an aliquot of cells in the first pass were cultured in a commercial human chondrogenic medium for three weeks. As a result, the percentage of surface markers for MSCs (CD105, CD90, CD73) in expanded cells in primary culture significantly increased, at the same time a decrease in the markers for hematopoietic cells (CD34 and CD45) was observed and the cells morphology was fibroblast-like. After three weeks of differentiation culture, the immunofluorescence analysis evidenced the expression of collagen-type-II. It was concluded that Mesenchymal Stem Cells isolated from mobilized peripheral blood in sheep have the ability to pre-differentiate into chondral like cells and express collagen type-II when are stimulated with a human commercial chondrogenic medium in monolayer culture.

The role of endoglin in post-ischemic revascularization

Following arterial occlusion, blood vessels respond by forming a new network of functional capillaries (angiogenesis), by reorganizing preexisting capillaries through the recruitment of smooth muscle cells to generate new arteries (arteriogenesis) and by growing and remodeling preexisting collateral arterioles into physiologically relevant arteries (collateral development). All these processes result in the recovery of organ perfusion. The importance of endoglin in post-occlusion reperfusion is sustained by several observations: (1) endoglin expression is increased in vessels showing active angiogenesis/remodeling; (2) genetic endoglin haploinsufficiency in humans causes deficient angiogenesis; and (3) the reduction of endoglin expression by gene disruption or the administration of endoglin-neutralizing antibodies reduces angiogenesis and revascularization. However, the precise role of endoglin in the several processes associated with revascularization has not been completely elucidated and, in some cases, the function ascribed to endoglin by different authors is controversial. The purpose of this review is to organize in a critical way the information available for the role of endoglin in several phenomena (angiogenesis, arteriogenesis and collateral development) associated with post-ischemic revascularization.

High-Efficiency Serum-Free Feeder-Free Erythroid Differentiation of Human Pluripotent Stem Cells Using Small Molecules

This article describes a highly efficient, fully feeder-free, serum-free method for erythroid differentiation of induced pluripotent stem cells and human embryonic stem cells, including a clinical-grade line, that is amenable to scale-up and as such will be of significant value for basic and translational studies of hematopoiesis and erythropoiesis.

This article describes a good manufacturing practice (GMP)-compatible, feeder-free and serum-free method to produce large numbers of erythroid cells from human pluripotent stem cells (hPSCs), either embryonic or induced. This multistep protocol combines cytokines and small molecules to mimic and surpass the early stages of development. It produces, without any selection or sorting step, a population of cells in which 91.8% ± 5.4% express CD34 at day 7, 98.6% ± 1.3% express CD43 at day 10, and 99.1% ± 0.95% of cells are CD235a positive by day 31 of the differentiation process. Moreover, this differentiation protocol supports extensive expansion, with a single hPSC producing up to 150 hematopoietic progenitor cells by day 10 and 50,000–200,000 erythroid cells by day 31. The erythroid cells produced exhibit a definitive fetal hematopoietic type, with 90%–95% fetal globin and variable proportion of embryonic and adult globin at the protein level. The presence of small molecules during the differentiation protocol has quantitative and qualitative effects; it increases the proportion of adult globin and decreases the proportion of embryonic globin. Given its level of definition, this system provides a powerful tool for investigation of the mechanisms governing early hematopoiesis and erythropoiesis, including globin switching and enucleation. The early stages of the differentiation protocol could also serve as a starting point for the production of endothelial cells and other hematopoietic cells, or to investigate the production of long-term reconstituting hematopoietic stem cells from hPSCs.

Significance

This differentiation protocol allows the production of a large amount of erythroid cells from pluripotent stem cells. Its efficiency is compatible with that of in vitro red blood cell production, and it can be a considerable asset for studying developmental erythropoiesis and red blood cell enucleation, thereby aiding both basic and translational research. In addition to red cells, the early stages of the protocol could also be used as a starting point for the large-scale production of other hematopoietic cell types, including the ultimate goal of generating long-term reconstituting hematopoietic stem cells.

Specification and function of hemogenic endothelium during embryogenesis

Hemogenic endothelium is a specialized subset of developing vascular endothelium that acquires hematopoietic potential and can give rise to multilineage hematopoietic stem and progenitor cells during a narrow developmental window in tissues such as the extraembryonic yolk sac and embryonic aorta-gonad-mesonephros. Herein, we review current knowledge about the historical and developmental origins of hemogenic endothelium, the molecular events that govern hemogenic specification of vascular endothelial cells, the generation of multilineage hematopoietic stem and progenitor cells from hemogenic endothelium, and the potential for translational applications of knowledge gained from further study of these processes.

Development of hematopoietic stem and progenitor cells from human pluripotent stem cells

Human pluripotent stem cells (hPSCs), including human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), provide a new cell source for regenerative medicine, disease modeling, drug discovery, and preclinical toxicity screening. Understanding of the onset and the sequential process of hematopoietic cells from differentiated hPSCs will enable the achievement of personalized medicine and provide an in vitro platform for studying of human hematopoietic development and disease. During embryogenesis, hemogenic endothelial cells, a specified subset of endothelial cells in embryonic endothelium, are the primary source of multipotent hematopoietic stem cells. In this review, we discuss current status in the generation of multipotent hematopoietic stem and progenitor cells from hPSCs via hemogenic endothelial cells. We also review the achievements in direct reprogramming from non-hematopoietic cells to hematopoietic stem and progenitor cells. Further characterization of hematopoietic differentiation in hPSCs will improve our understanding of blood development and expedite the development of hPSC-derived blood products for therapeutic purpose.

Safety and feasibility for pediatric cardiac regeneration using epicardial delivery of autologous umbilical cord blood-derived mononuclear cells established in a porcine model system

Congenital heart diseases (CHDs) requiring surgical palliation mandate new treatment strategies to optimize long-term outcomes. Despite the mounting evidence of cardiac regeneration, there are no long-term safety studies of autologous cell-based transplantation in the pediatric setting. We aimed to establish a porcine pipeline to evaluate the feasibility and long-term safety of autologous umbilical cord blood mononuclear cells (UCB-MNCs) transplanted into the right ventricle (RV) of juvenile porcine hearts. Piglets were born by caesarean section to enable UCB collection. Upon meeting release criteria, 12 animals were randomized in a double-blinded fashion prior to surgical delivery of test article (n=6) or placebo (n=6). The UCB-MNC (3×10(6) cells per kilogram) or control (dimethyl sulfoxide, 10%) products were injected intramyocardially into the RV under direct visualization. The cohorts were monitored for 3 months after product delivery with assessments of cardiac performance, rhythm, and serial cardiac biochemical markers, followed by terminal necropsy. No mortalities were associated with intramyocardial delivery of UCB-MNCs or placebo. Two animals from the placebo group developed local skin infection after surgery that responded to antibiotic treatment. Electrophysiological assessments revealed no arrhythmias in either group throughout the 3-month study. Two animals in the cell-therapy group had transient, subclinical dysrhythmia in the perioperative period, likely because of an exaggerated response to anesthesia. Overall, this study demonstrated that autologous UCB-MNCs can be safely collected and surgically delivered in a pediatric setting. The safety profile establishes the foundation for cell-based therapy directed at the RV of juvenile hearts and aims to accelerate cell-based therapies toward clinical trials for CHD.

Protective effects of HGF gene-expressing human mesenchymal stem cells in acetaminophen-treated hepatocytes

Mesenchymal stem cells (MSC) secrete a great variety of cytokines that have beneficial paracrine actions. Hepatocyte growth factor (HGF) promotes proliferation in several cell types. The aim of the present study was to investigate the protective effect of HGF gene-transfected MSC (HGF-MSC) in acetaminophen (AAP)-treated hepatocytes. We transfected the HGF gene into MSCs and confirmed HGF expression by RT-PCR and western blot. The concentration of HGF in HGF-MSC conditioned media (HGFCM) was upregulated compared with that in control MSCCM samples. Cell viability was increased in HGFCM-treated hepatocytes. Expression of Mcl-1, an anti-apoptosis protein, was increased and expression of pro-apoptosis proteins (Bad, Bik and Bid) was decreased in HGFCM-treated hepatocytes. HGF-MSC had protective effects on AAP-induced hepatocyte damage by enhancing proliferation. These results suggest that HGF-expressing MSCs may provide regenerative potential for liver cell damage.

Quantitative and functional characteristics of endothelial progenitor cells in newly diagnosed hypertensive patients

Populations of peripheral blood CD34(+) cells comprise precursors of endothelial cells. These precursors are crucial to cardiovascular homeostasis. Hypertension, as one of the main risk factors for cardiovascular disease, is associated with the loss of endothelium structural integrity and its functional impairment. The aim of our study was to evaluate the subsets of endothelial precursor cells in patients with newly diagnosed arterial hypertension. Twenty-four newly diagnosed, previously untreated hypertensive patients aged 59.5 ± 12.5 years, were enrolled into the study group, whereas the control group comprised 45 healthy subjects, 55.5±10.0 years old. Endothelial progenitor cells (EPCs) were analysed by flow cytometry. The results showed that hypertensive patients were characterized by a significantly higher percentage and number of the CD34(+) cells and simultaneously less differentiated CD34(+)CD45(dim/neg)CD133(+) progenitors. The percentage and number of CD34(+)CD45(neg)VEGFR2(+) and CD34(+)CD45(neg)CD133(+)VEGFR2(+) cells were not different from the control group. Moreover, patients had a significantly lower percentage and number of the CD34(+)CD45(neg)VEGFR2(+)CXCR4(+) and CD34(+)CD45(neg)VEGFR2(+)ICAM-1(+) cells than healthy individuals. These changes were paralleled by early symptoms of nephropathy, that is, lower glomerular filtration rate (GFR) values and borderline micro albuminuria. Our results indicate that an elevation in the number of less differentiated progenitors may be a mechanism compensating for defects of migration and adhesion, present in a more differentiated subset.

Comparative study of autophagy inhibition by 3MA and CQ on Cytarabine‑induced death of leukaemia cells

BACKGROUND

As the molecular mechanisms of Cytarabine,one of the most important drugs used in the leukaemia’s treatment, are only partially understood and the role of autophagy on leukaemia development and treatment is only recently being investigated, in this study, by using Chloroquine (CQ) and 3-methyladenine (3MA) as autophagy inhibitors, we aim to evaluate the contribution of an autophagic mechanism to Cytarabine (AraC)-induced death of HL60 leukaemia cells.

METHODS

Trypan blue exclusion and AnnexinV/PI assays were used to evaluate HL60 cell death under AraC treatment in the presence or absence of 3MA and CQ. Western blotting and immunofluorescence experiments were performed to show the involvement of apoptosis and autophagy protein expressions. Phenotypic characterization of HL60-treated cells was performed by using immunophenotyping. Clonogenic assays were applied to analyse clonal function of HL60-treated cells.

RESULTS

We observed that although autophagy inhibition by 3MA, but not CQ, increased the death of HL60 AraC cells after 24 h of treatment, no significant differences between AraC and AraC + 3MA-treated groups were observed by using clonogenic assay. In addition, increased number of immature (CD34(+)/CD38(−)Lin(−/low)) HL60 cells was found in AraC and AraC-3MA groups when compared with control untreated cells.

CONCLUSIONS

Although AraC anti-leukaemia effects could be potentiated by 3MA autophagy inhibition after 24 h of exposure, leukaemia cell resistance, the main causes of treatment failure, is also promoted by autophagy initial stage impairment by 3MA, denoting the complex role of autophagy in leukaemia cells’ response to chemotherapy.