scholarly journals Differential Expression of CD49f Discriminates the Independently Emerged Hematopoietic Stem Cells and Erythroid-Biased Progenitors

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3700-3700
Author(s):  
Ai-Ning Xu ◽  
Dan Liu ◽  
Yu-Ting Dai ◽  
Fan Zhang ◽  
Jian Shen ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cells ◽  
Endothelial Cells ◽  
Differential Expression ◽  
Regulatory Mechanism ◽  
Erythroid Progenitors ◽  
Hematopoietic Stem ◽  
In Vitro System

While hematopoietic stem cells (HSCs) can sustain the production of all types of mature blood cells throughout the life, there also exists HSC-independent hematopoiesis, which partially supports embryonic hematopoiesis and generation of specific types of adult hematopoietic cells (e.g., macrophages). Examples of the HSC-independent hematopoiesis include (i) the primitive wave of hematopoiesis that produces unipotent progenitors for erythrocytes, megakaryocytes or macrophages, and (ii) the "pro-definitive" hematopoiesis that produces multipotent erythro-myeloid progenitors (EMPs). Given that HSCs and HSC-independent progenitors are both derived from endothelial cells in distinct or overlapping hematopoietic sites, tracing their developmental origins and clarifying the regulatory mechanism will enhance our understanding of the profound difference between them and may improve in vitro generation of HSCs. Human HSCs have been refined based on the expression of CD49f (ITGA6). In combination with other HSC markers (CD34+CD38-CD45RA-CD43+CD90+), high expression of CD49f identifies long-term multilineage engrafting HSCs, whereas the cells with low CD49f represent a subtype of hematopoietic progenitor cells (HPCs) that possess transient engrafting activity. Meanwhile, CD49f has also been shown to be heterogeneously expressed in hemogenic endothelial cells (HECs), which give rise to both HSCs and EMPs via endothelial-to-hematopoietic transition (EHT). Thus, determining the changes (i.e., persistence, gain or loss) of CD49f expression during EHT is a key step in tracing the origins of HSCs and HSC-independent HPCs. In this study, using an in vitro system of HSC differentiation from human embryonic stem cells (hESCs), we observed that, while CD49f is highly expressed in all hESCs, only a portion of HECs express CD49f. Importantly, live cell imaging analysis revealed that CD49f expression persists during EHT, which is accompanied by initiating CD43 expression. To test whether the differential CD49f expression is associated with HSC versus HPC functions, we sorted the CD49fhigh and CD49flow cells and performed colony forming assay and gene expression profiling. The results showed that the CD49fhigh cells have multilineage potential, whereas the CD49flow cells lack lymphoid potential but show a strong erythroid preference. Gene expression analysis confirmed that the CD49fhigh and CD49flow cells represent HSCs and erythroid-biased HPCs, respectively, and that the Wnt and Notch signaling pathways may play a role in their functions. Collectively, these observations suggest that the CD49fhigh and the CD49flow cells are concurrently derived from the CD49fhigh and CD49flow HECs, thus modeling the in vivo generation of HSCs and HSC-independent HPCs. Based on the in vitro observations, we proposed that CD49f in vivo may also specify the distinct HSPCs emerged at different developmental stages/sites. To test this hypothesis, we isolated mouse primitive HPCs, EMPs and definitive HSCs, as well as their parental HECs, from yolk sac, embryo, and aorta-gonad-mesonephros (AGM) of different embryonic stages and determined their CD49f expression. The results showed that the primitive erythroid progenitors have lowest, whereas the definitive AGM HSCs have highest, CD49f levels; this trend was also observed in the related HECs isolated from various stages/sites. Thus, it is likely that the embryonic hematopoiesis is recapitulated, at least partially, by the in vitro system in terms of the sequential emergence of HSPCs ranging from unipotent erythroid progenitors to multipotent definitive HSCs, and this may also underlie the situation that EMPs and HSCs can be produced at the same stage/site but independently from different HECs. In summary, using the in vitro HSC differentiation system, we found that the differential expression of CD49f discriminates HSCs and HSC-independent progenitors, which are concurrently emerged from HECs. The persistent CD49f expression during EHT suggests that the fates of HSCs and HSC-independent HPCs are pre-defined in their parental HECs. Combining our in vivo data, the differential expression of CD49f also provide a possible regulatory mechanism for the multi-wave hematopoiesis. Further exploring the function and mechanism of CD49f in these regulations should be important for fully understanding the precisely regulated HSC generation and activities. Disclosures No relevant conflicts of interest to declare.

LYL1, Class II Basic Helix-Loop-Helix Transcription Factor, Induces the Differentiation of Common Marmoset Embryonic Stem Cells to Hematopoietic Stem Cells

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2348-2348
Author(s):  
Hirotaka Kawano ◽  
Tomotoshi Marumoto ◽  
Michiyo Okada ◽  
Tomoko Inoue ◽  
Takenobu Nii ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cells ◽  
Lymphoblastic Leukemia ◽  
Embryonic Stem ◽  
Common Marmoset ◽  
Hematopoietic Stem ◽  
Helix Loop Helix ◽  
Cd34 Cells

Abstract Abstract 2348 Since the successful establishment of human embryonic stem cells (ESCs) in 1998, transplantation of functional cells differentiated from ESCs to the specific impaired organ has been expected to cure its defective function [Thomson JA et al., Science 282:1145–47, 1998]. For the establishment of the regenerative medicine using ESCs, the preclinical studies utilizing animal model systems including non-human primates are essential. We have demonstrated that non-human primate of common marmoset (CM) is a suitable experimental animal for the preclinical studies of hematopoietic stem cells (HSCs) therapy [Hibino H et al., Blood 93:2839–48, 1999]. Since then we have continuously investigated the in vitro and in vivo differentiation of CM ESCs to hematopoietic cells by the exogenous hematopoietic gene transfer. In earlier study, we showed that the induction of CD34+ cells having a blood colony forming capacity from CM ESCs is promoted by lentiviral transduction of TAL1 cDNA [Kurita R et al., Stem Cells 24:2014-22,2006]. However those CD34+ cells did not have a bone marrow reconstituting ability in irradiated NOG (NOD/Shi-scid/IL-2Rγnull) mice, suggesting that transduction of TAL1 gene is not enough to induce functional HSCs which have self-renewal capability and multipotency. Thus we tried to find other hematopoietic genes being able to promote hematopoietic differetiation more efficiently than TAL1. We selected 6 genes (LYL1, HOXB4, BMI1, GATA2, c-MYB and LMO2) as candidates for factors that induce the differentiation from ESCs to HSCs, based on the comparison of gene expression level between human ESCs and HSCs by Digital Differential Display from the Uni-Gene database at the NCBI web site (http://www.ncbi.nlm.nih.gov/UniGene/). Then, we transduced the respective candidate gene in CM ESCs (Cj11), and performed embryoid body (EB) formation assay to induce their differentiation to HSCs for 9 days. We found that lentiviral transduction of LYL1, a basic helix-loop-helix transcription factor, in EBs derived from Cj11, one of CM ESC lines, markedly increased the number of cells positive for CD34, a marker for hematopoietic stem/progenitors. The lymphoblastic leukemia 1 (LYL1) was originally identified as the factor of a chromosomal translocation, resulting in T cell acute lymphoblastic leukemia [Mellentin JD et al., Cell 58:77-83.1989]. These class II bHLH transcription factors regulate gene expression by binding to target gene sequences as heterodimers with E-proteins, in association with Gata1 and Gata2 [Goldfarb AN et al., Blood 85:465-71.1995][Hofmann T et al., Oncogene 13:617-24.1996][Hsu HL et al., Proc Natl Acad Sci USA 91:5947-51.1994]. The Lyl1-deficient mice display the reduction of B cells and impaired long-term hematopoietic reconstitution capacity [Capron C et al., Blood 107:4678-4686. 2006]. And, overexpression of Lyl1 in mouse bone marrow cells induced the increase of HSCs, HPCs and lymphocytes in vitro and in vivo [Lukov GL et al., Leuk Res 35:405-12. 2011]. These information indicate that LYL1 plays important roles in hematopoietic differentiation in primate animals including human and common marmoset. To examine whether overexpression of LYL1 in EBs can promote hematopoietic differentiation in vitro we performed colony-forming unit (CFU) assay, and found that LYL1-overexpressing EBs showed the formation of multi-lineage blood cells consisting of erythroid cells, granulocytes and macrophages. Next, we analyzed gene expression level by RT-PCR, and found that the transduction of LYL1 induced the expression of various hematopoietic genes. These results suggested that the overexpression of LYL1 can promote the differentiation of CM ESCs to HSCs in vitro. Furthermore we found that the combined overexpression of TAL1 and LYL1 could enhance the differentiation of CD34+ cells from CM ESCs than the respective overexrpession of TAL1 or LYL1. Collectively, our novel technology to differentiate hematopoietic cells from ESCs by the transduction of specific transcription factors is novel, and might be applicable to expand human hematopoietic stem/progenitor cells in vitro for future regenerative medicine to cure human hematopoietic cell dyscrasias. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Influence of the endothelial cells on the erythroid differentiation of umbilical cord blood hematopoietic stem cells in vitro

2020 ◽  
Vol 17 (1) ◽  
pp. 78-86
Author(s):  
A. S. Voytehovich ◽  
E. V. Vasina ◽  
V. S. Kastsiunina ◽  
I. N. Seviaryn ◽  
N. V. Petyovka
Keyword(s):  
Stem Cells ◽  
Endothelial Cells ◽  
Cord Blood ◽  
Umbilical Cord ◽  
Umbilical Cord Blood ◽  
Erythroid Differentiation ◽  
Erythroid Progenitors ◽  
Hematopoietic Stem ◽  
Vascular Niche

The objective is to study the effect of umbilical cord blood endothelial cells on the hematopoietic cells growth and the maturation in the erythroid direction in co-culture, as well as the expression of adult and fetal hemoglobin genes during erythroid differentiation under the conditions of vascular niche modeling in vitro. We used the following research methods: cultural, flow cytometry, real-time PCR and morphological analysis. We have developed the method of hematopoietic cord blood stem cells erythroid differentiation in co-culture using cord blood endothelial cell progenitors. CD34+CD31+CD144+CD105+CD90–CD45– progenitors of endothelial cells stimulate the erythroid differentiation of hematopoietic CD34+ cord blood cells and the growth of erythroid progenitors in co-culture from the 4th to 11th day in the presence of the stem cell factor, the erythropoietin and the fibroblast growth factor-2. The in vitro modeling of the vascular niche increases the mature CD36–CD235a+ erythroid cells 2.5 times higher than those in the liquid culture. The microenvironment of endothelial cells does not affect the level and expression ratio of fetal and adult hemoglobin during the erythroid differentiation in vitro.

Novel Method to Study Mouse Bone Marrow Endothelial Cells in Vivo and in Vitro

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 617-617 ◽  
Author(s):  
Yuxin Feng ◽  
Ming Liu ◽  
Fukun Guo ◽  
Wei Liu ◽  
Leesa Sampson ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Endothelial Cells ◽  
Culture System ◽  
Assay Method ◽  
Mouse Bone Marrow ◽  
Hematopoietic Stem ◽  
Egfp Reporter

Abstract Abstract 617 Self-renewal, differentiation, and proliferation of hematopoietic stem cells (HSCs) and leukemia stem cells (LSCs) are maintained in a complex microenvironment of the adult bone marrow (BM). BM endothelial cells (ECs) have been proposed to be a key component of HSC and LSC niche. However, in contrast to the well-developed culture system of human ECs, current work of murine BM endothelial cells is hindered by a lack of mouse bone marrow endothelial cell primary culture and suitable assay methods to clearly define murine BMEC functionality in vivo and in vitro, which limits genetic and mechanistic studies by using mouse models. To establish an in vivo approach to study the EC function in adult mice, a strain of Tie2-CreER transgenic mice was generated to allow conditional and inducible manipulation of BMECs by Cre recombinase expression under the Tie2 promoter. In vivo lineage tracing was achieved in a Tie2-CreER/TD-tomato or -EGFP reporter mouse strain. Upon a four day Tamoxifen injection regimen, TD-tomato or EGFP reporter was readily visualized in bone marrow vasculature that colocalizes with CD31+ ECs as determined by immunostaining. FACS analysis of Tie2-CreER/EGFP reporter mice showed that the EGFP+ cells in the BM were exclusively in the CD45- VEGFR2+ and CD31+ cell fraction, with no EGFP+ cells being detectable in the CD45+ hematopoietic lineages or osteoblast/stroma cell fractions, suggesting that the Tie2-driven CreER expression is limited to the endothelial lineage in the adult BM. Next, we developed an in vitro method to culture and assay the mouse BMECs functionally. An in vitro selection process allowed us to establish a primary BM cell culture condition that permitted functional expansion and maintenance of mouse BMECs in long-term tissue culture, yielding homogenous CD45- cells expressing endothelial markers CD31, CD34 and VEGFR2. These cells formed capillary-like structures in 2-demensional and 3-demensional tubes/capillaries, and showed TD-tomato reporter color when derived from the Tamoxifen induced Tie2-CreER/TD-tomato mouse BM. They showed expected adhesion and migration activities and morphology of ECs. Lineage chasing assays using isolated CD45+ and CD45- BM cells from the Tie2-CreER/Td-tomato mice demonstrated that the BMECs in our culture system, bearing the Tie2-promoter driven TD-tomato color and CD31+ marker, were exclusively derived from CD45- non-hematopoietic lineage. Taken together, we have established a faithful assay method for studying murine BM EC functions in vivo and in vitro, allowing the tracking and genetic manipulation of adult BM ECs in mice and in culture. The method can be useful for delineating molecular and cellular mechanisms of BMEC regulation and EC-mediated BM niche function, and may have value in testing anti-angiogenic activities of anticancer drugs in animal models. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Distinct Gene Expression Patterns Drive Proliferation of Dominant-Negative RUNX1 Immortalized HSPCs

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1795-1795
Author(s):  
Samantha K Langer ◽  
Alyssa Cull ◽  
Natalie Wossidlo ◽  
Hannes Klump ◽  
Peter A. Horn ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stem Cells ◽  
Bone Marrow ◽  
Tumor Suppressor ◽  
Dominant Negative ◽  
Tumor Suppressor Function ◽  
Self Renewal ◽  
Hematopoietic Stem

Abstract The transcription factor RUNX1 is a master regulator of normal hematopoiesis and is involved in cell fate decisions. RUNX1 mutations have been shown to contribute to the development of myeloid neoplasms, and in myelodysplastic syndromes (MDS) it is one of the most frequently mutated genes. Such mutations lead to RUNX1 proteins that lack transactivation activity or DNA-binding ability resulting in a loss of its tumor suppressor function. The dominant-negative short isoform RUNX1a resembles truncated RUNX1 mutants and inhibits the function of the full-length RUNX1 proteins. Additionally, a recently published study identified overexpression of RUNX1a but not full-length RUNX1 in CD34+-cells from patients with myelodysplastic/myeloproliferative disease, which increased with disease progression. This strongly suggests that truncated RUNX1 plays a pivotal role in myelodysplastic disease. However, the precise molecular functions of mutating RUNX1, particularly with respect to the identity of RUNX1 target genes conferring its tumor suppressor function, remain unclear. Previously, our group reported that overexpression of RUNX1a immortalized murine hematopoietic stem and progenitor cells (HSPCs) in vitro. Immunophenotyping of these cells confirmed the expansion of an immature subpopulation defined as Lin- Sca1+ Kit+ (LSK). This phenotype was reversed upon turning RUNX1a-expression off and led to a loss of Sca1 expression (Lin- Kit+, LK). To further understand the molecular consequences of RUNX1a overexpression we sorted the LK cells and LSK cells before and 36h after RUNX1a-expression was turned off. Next, we performed microarray analysis to assess differential gene expression in these different subpopulations. Gene set enrichment analysis (GSEA) identified upregulation of genes highly expressed in hematopoietic stem cells (HSC) and leukemic stem cells (LSCs) in RUNX1a-expressing LSK cells compared to those LSK cells in which RUNX1a expression was turned off. Conversely, a gene signature associated with stemness and self-renewal was lost in LK-cells when RUNX1a expression was turned off. Among the eleven leading edge genes, we found genes implicated in leukemogenesis, stem cell regulation, or both such as Erg, Meis1 and Bcl11a. To further understand the role of RUNX1a in vivo we transplanted C57Bl6 mice (n=29) with HSPCs expressing RUNX1a in a competitive reconstitution setting. Consistent with the immortalization of HSPCs in vitro, RUNX1a-overexpressing HSPCs expanded in the bone marrow of transplanted mice. We observed significantly higher frequencies of LK (2.9-fold) and LSK cells (5-fold) in the RUNX1a-expressing bone marrow cells compared to transplanted control mice. High frequencies of RUNX1a-expressing cells in the bone marrow were associated with lower frequencies of RUNX1a-expressing cells in the peripheral blood indicating a differentiation block. In addition, we found that 85% of the RUNX1a-expressing cells were committed to the myeloid lineage (CD11b+/Ly6G+) at the expense of the lymphoid lineage (B220 and CD3e). Moreover, RUNX1a expression led to an increased percentage (65%) of immature erythroblasts (Ter119-) in the bone marrow compared to control cells (55%). In summary, we have demonstrated that RUNX1a overexpression immortalized HSPCs by upregulation of genes involved in leukemogenesis, stemness and self-renewal. In vivo such HSPCs showed a competitive advantage that was associated with a block of differentiation. Our study, particularly the gene expression analysis, provides novel insights into genetic drivers contributing to the development of myeloid malignancies in patients with RUNX1 mutations. Disclosures No relevant conflicts of interest to declare.

Identification of in vitro growth conditions for c-Kit–negative hematopoietic stem cells

Blood ◽  
2003 ◽  
Vol 102 (9) ◽  
pp. 3120-3128 ◽  
Author(s):  
Kim Klarmann ◽  
Mariaestela Ortiz ◽  
Meghan Davies ◽  
Jonathan R. Keller
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Growth Conditions ◽  
Hematopoietic Stem ◽  
In Vitro System ◽  
Bone Marrow Cultures ◽  
In Vitro Systems

AbstractOur laboratory recently identified a quiescent class of pluripotent hematopoietic stem cells (PHSCs) that are lineage negative (Linneg), lack c-Kit, and are able to give rise to c-Kit–positive (c-Kitpos) PHSCs in vivo. This population fails to proliferate in vitro but has delayed reconstituting activity in vivo. In this study, we purified these cells to enrich for the PHSCs and we identified in vitro conditions capable of supporting their maturation. The c-Kit–negative (c-Kitneg) cells exhibited differential expression of Sca-1, CD34, CD43, CD45, and Thy 1.2. We purified the cells based on Sca-1, as it is expressed on active PHSCs. We detected pre–colony-forming unit spleen (pre–CFU-s) activity in both the Sca-1neg and Sca-1pos populations, indicating the presence of primitive PHSCs in both populations. However, our in vitro studies suggest that the Sca-1pos population is enriched for PHSCs. The in vitro systems that support the growth of these dormant cells include a modified long-term marrow culture and various stromal cell lines. In modified long-term bone marrow cultures, c-Kitneg cells gave rise to c-Kitpos PHSCs, with long-term reconstitution activity in vivo. Thus we have established an in vitro system to examine PHSC maturation that will allow us to study the mediators of the c-Kitneg to c-Kitpos transition.

Identification of Phospholipase C Gamma 1 As a Key Regulator of Erythropoiesis

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 4744-4744
Author(s):  
Tina M Schnoeder ◽  
Patricia Arreba-Tutusaus ◽  
Inga Griehl ◽  
Daniel B Lipka ◽  
Florian H Heidel ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Fetal Liver ◽  
Erythroid Progenitors ◽  
Hematopoietic Stem ◽  
I 11 ◽  
Erythroid Development

Abstract Abstract 4744 Erythropoiesis is a complex multistage process in which the development of red blood cells occurs through expansion and differentiation of hematopoietic stem cells (HSCs) into more committed progenitors. Regulation of survival, expansion and differentiation of erythroid progenitors is dependent on a well-coordinated cohort of transcription factors and an intricate network of finely tuned regulatory signalling pathways. In vivo and in vitro studies have highlighted erythropoietin receptor (EpoR) signaling through JAK2 tyrosine kinase as a crucial regulator of erythropoiesis. This leads to the subsequent activation of downstream effectors such as STAT5, MAPK, and PI-3K/Akt pathways. However, detailed knowledge about signalling pathways involved in EPO/EpoR induced differentiation of erythroid progenitors remain elusive. Phosphatidylinositol-specific phospholipase C gamma1 (PLCg1) is known to act as key mediator of calcium-signalling that can substitute for PI-3K/AKT signalling in oncogenic models. Moreover, its loss is associated with lack of erythropoiesis in a straight knockout mouse model. As it is tempting to speculate on the role of Plcg1/Ca-signalling downstream of EpoR/JAK in regulation of erythroid development we aimed to investigate its influence on differentiation and proliferation of hematopoietic cells in vitro and in vivo. Using different cellular models (Ba/F3, 32D) stably transfected with EpoR and wildtype JAK2 we could provide evidence that PLCg1 is a downstream target of EpoR/JAK2 signalling. Knockdown of PLCg1 led to a decreased proliferation of PLCg1-deficient cells compared to control cells whereas survival of these cells was not affected. In contrast, other downstream targets of EpoR signalling were not affected by PLCg1 knockdown. In order to assess specifically its role in erythroid development, we used the murine pro-erythroblast cell line I-11 as well as primary fetal liver cells (FLC). The I-11 cell line was isolated from p53-deficient fetal livers and is able to differentiate upon dexamethasone-/stem cell factor-withdrawal combined with erythropoietin stimulation; primary FLC were harvested at E13.5. PLCg1 knockdown by using RNA-interference technology led to a significant delay in erythroid differentiation and accumulation of immature erythroid progenitors (e.g. pro-erythroblasts) as assessed by cytology and flow cytometry technology. In addition, we tested the colony-forming potential of PLCg1-deficient I-11 and fetal liver cells compared to controls. Colony formation was significantly impaired in both - I-11 and primary FLC - when compared to control cells (shRNA-scr). We performed gene-expression analysis by Q-RT-PCR on sorted hematopoietic stem and progenitor cells and found a higher expression in MEP compared to GMP or CMP. To clarify, whether the effects of Plcg1 knockdown are restricted to erythroid development at the stage of MEP or erythroid progenitors, we aimed to investigate adult hematopoietic stem cells in erythroid development. We infected lineage-depleted/erythroid-enriched (Gr1-, B220-, CD3/4/8, CD19-/ IL7Ra- negative) bone marrow cells with either PLCg1 or control shRNA. Using flow cytometry analysis to examine differentiation we could observe a reduction of megakaryocyte/erythroid progenitor cells (MEP) in PLCg1 knockdown cells compared to control cells while development of other lineages (e.g. GMP) remained unaffected. Currently, competitive repopulation assays investigating the repopulation and differentiation capacity of hematopoietic stem cells after Plcg1 knockdown (or scr controls) are under way to explore the role of Plcg1 signalling in hematopoietic and erythroid development in vivo. Taken together, our findings presume PLCg1 to be a key regulator in erythroid development and understanding of its relevance in development and maintenance of normal hematopoiesis will be a crucial prerequisite for targeting this important pathway in myeloproliferative disease. Disclosures: No relevant conflicts of interest to declare.

Strategies to Protect Hematopoietic Stem Cells from Culture-Induced Stress Conditions

2020 ◽  
Vol 15 ◽  
Author(s):  
Fatima Aerts-Kaya
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Ex Vivo ◽  
Stress Conditions ◽  
Stress Factors ◽  
Hematopoietic Stem ◽  
Induced Stress

: In contrast to their almost unlimited potential for expansion in vivo and despite years of dedicated research and optimization of expansion protocols, the expansion of Hematopoietic Stem Cells (HSCs) in vitro remains remarkably limited. Increased understanding of the mechanisms that are involved in maintenance, expansion and differentiation of HSCs will enable the development of better protocols for expansion of HSCs. This will allow procurement of HSCs with long-term engraftment potential and a better understanding of the effects of the external influences in and on the hematopoietic niche that may affect HSC function. During collection and culture of HSCs, the cells are exposed to suboptimal conditions that may induce different levels of stress and ultimately affect their self-renewal, differentiation and long-term engraftment potential. Some of these stress factors include normoxia, oxidative stress, extra-physiologic oxygen shock/stress (EPHOSS), endoplasmic reticulum (ER) stress, replicative stress, and stress related to DNA damage. Coping with these stress factors may help reduce the negative effects of cell culture on HSC potential, provide a better understanding of the true impact of certain treatments in the absence of confounding stress factors. This may facilitate the development of better ex vivo expansion protocols of HSCs with long-term engraftment potential without induction of stem cell exhaustion by cellular senescence or loss of cell viability. This review summarizes some of available strategies that may be used to protect HSCs from culture-induced stress conditions.

Abstract 558: Microchanneled Polysaccharide Hydrogel Laden With Endothelial Cells and Mesenchymal Stem Cells With VEGF Facilitate Formation of Vascular Structures and Are Effective for Repairing Tissue Ischemia

2014 ◽  
Vol 34 (suppl_1) ◽  
Author(s):  
Sangho Lee ◽  
Min Kyung Lee ◽  
Hyunjoon Kong ◽  
Young-sup Yoon
Keyword(s):  
Stem Cells ◽  
Endothelial Cells ◽  
Mesenchymal Stem Cells ◽  
Cell Survival ◽  
Vascular Structure ◽  
Hindlimb Ischemia ◽  
Alginate Hydrogel ◽  
Vessel Formation

Various hydrogels are used to create vascular structure in vitro or to improve cell engraftment to overcome low cell survival in vivo, a main hurdle for bare cell therapy Recently we developed a modified alginate hydrogel within which microchannels are aligned to guide the direction and spatial organization of loaded cells. We investigated whether these cell constructs in which HUVECs and human mesenchymal stem cells (hMSCs) are co-loaded in this novel microchanneled hydrogel facilitate formation of vessels in vitro and in vivo, and enhance recovery of hindlimb ischemia. We crafted a modified alginate hydrogel which has microchannels, incorporates a cell adhesion peptide RGD, and was encapsulated with VEGF. We then compared vascular structure formation between the HUVEC only (2 x 105 cells) group and the HUVEC plus hMSC group. In the HUVEC+hMSC group, we mixed HUVECs and hMSCs at the ratio of 3:1. For cell tracking, we labeled HUVECs with DiO, a green fluorescence dye. After loading cells into the microchannels of the hydrogel, these constructs were cultured for seven days and were examined by confocal microscopy. In the HUVEC only group, HUVECs stands as round shaped cells without forming tubular structures within the hydrogel. However, in the HUVEC+hMSC group, HUVECs were stretched out and connected with each other, and formed vessel-like structure following pre-designed microchannels. These results suggested that hMSCs play a critical role for vessel formation by HUVECs. We next determined their in vivo effects using a mouse hindlimb ischemia model. We found that engineered HUVEC+hMSC group showed significantly higher perfusion over 4 weeks compared to the engineered HUVEC only group or bare cell (HUVEC) group. Confocal microscopic analysis of harvested tissues showed more robust vessel formation within and outside of the cell constructs and longer term cell survival in HUVEC+hMSC group compared to the other groups. In conclusion, this novel microchanneled alginate hydrogel facilitates aligned vessel formation of endothelial cells when combined with MSCs. This vessel-embedded hydrogel constructs consisting of HUVECs and MSCs contribute to perfusable vessel formation, prolong cell survival in vivo, and are effective for recovering limb ischemia.

Endothelial stroma programs hematopoietic stem cells to differentiate into regulatory dendritic cells through IL-10

Blood ◽  
2006 ◽  
Vol 108 (4) ◽  
pp. 1189-1197 ◽  
Author(s):  
Hua Tang ◽  
Zhenhong Guo ◽  
Minghui Zhang ◽  
Jianli Wang ◽  
Guoyou Chen ◽  
...  
Keyword(s):  
Stem Cells ◽  
Dendritic Cells ◽  
T Cell ◽  
Hematopoietic Stem Cells ◽  
Critical Role ◽  
Regulatory Function ◽  
Hematopoietic Stem ◽  
Regulatory Dendritic Cells

Abstract Regulatory dendritic cells (DCs) have been reported recently, but their origin is poorly understood. Our previous study demonstrated that splenic stroma can drive mature DCs to proliferate and differentiate into regulatory DCs, and their natural counterpart with similar regulatory function in normal spleens has been identified. Considering that the spleen microenvironment supports hematopoiesis and that hematopoietic stem cells (HSCs) are found in spleens of adult mice, we wondered whether splenic microenvironment could differentiate HSCs into regulatory DCs. In this report, we demonstrate that endothelial splenic stroma induce HSCs to differentiate into a distinct regulatory DC subset with high expression of CD11b but low expression of Ia. CD11bhiIalo DCs secreting high levels of TGF-β, IL-10, and NO can suppress T-cell proliferation both in vitro and in vivo. Furthermore, CD11bhiIalo DCs have the ability to potently suppress allo-DTH in vivo, indicating their preventive or therapeutic perspectives for some immunologic disorders. The inhibitory function of CD11bhiIalo DCs is mediated through NO but not through induction of regulatory T (Treg) cells or T-cell anergy. IL-10, which is secreted by endothelial splenic stroma, plays a critical role in the differentiation of the regulatory CD11bhiIalo DCs from HSCs. These results suggest that splenic microenvironment may physiologically induce regulatory DC differentiation in situ.

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