The Influence of Spatially Distinct Bone Marrow Niches on HSCs

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3565-3565
Author(s):  
Sali Liu ◽  
Tigue Tozer ◽  
Dilani Rosa ◽  
Cynthia Cunningham ◽  
Alan Tseng ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Stromal Cells ◽  
Fetal Liver ◽  
Long Bone ◽  
Pcr Analysis ◽  
Appendicular Skeleton ◽  
Long Bones ◽  
Hematopoietic Stem ◽  
Flat Bone

Abstract During development, hematopoietic stem cells (HSCs) translocate from the fetal liver to the bone marrow (BM), which remains the site of hematopoiesis throughout adulthood. In the BM the HSCs are located at the endosteal surface, where cells of the osteoblastic lineage comprise a key component of the stem cell niche. While hematopoiesis occurs in many bones, the process of bone formation can actually be split into those bones that develop through endochondral ossification (long bones) and those that form through membranous ossification (flat bones). We examined the role played by the microenvironment in these two distinct bones and whether these microenvironments have differing effects on the HSCs. In vitro analysis of the BM stromal cells isolated from long bones and flat bones has demonstrated that calvaria derived stromal layers can support cobblestone area-forming cells 10-fold greater than stromal layers derived from femurs and tibia. Real-time PCR analysis of gene expression has demonstrated that flat bone stromal cells have 5-fold greater expression of N-cadherin than long bone, while other cadherins such as VE-cadherin show no difference. Correlating with this, we found that calvarial derived HSCs demonstrated increased expression of N-cadherin and also increased expression of other genes associated with cadherin signaling, such as cyclinD1. However, no difference in the cell cycle status of the HSCs derived from long bone and flat bone was noted. Functional assays are being performed in order to assess the function of these distinct BM marrow niches in vivo. It is anticipated that we will be able to begin to define the molecular cues the govern HSC physiology in different locations within the mammalian skeleton and thus provide an understanding not only into the continual migration of HSCs between different HSC niches but also the regression of hematopoiesis that occurs from the appendicular skeleton to the axial skeleton during the adult human lifespan.

A New Approach to Expand Cord Blood Derived Hematopoietic Stem Cells, Using Bioengineered Human Fetal Liver Tissue 3D-Constructs

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 3097-3097
Author(s):  
Saloomeh Mokhtari ◽  
Pedro Baptista ◽  
Dipen Vyas ◽  
Charles Jordan Freeman ◽  
Emma Moran ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Cord Blood ◽  
Stromal Cells ◽  
Culture System ◽  
Fetal Liver ◽  
Rapid Expansion ◽  
Hematopoietic Stem ◽  
3D Cultures

Abstract 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 both long- and short-term repopulating cells, capable of functional engraftment, to enable the treatment of an adolescent or adult patient. We have previously shown that CB-HSPC can be effectively expanded in a 2D serum-free culture system, using a feeder layer of adult human bone marrow-derived stromal cells; still, the percentage of the most primitive stem cells decreased with time. Because, during development, the fetal liver is the main site of HSC expansion and differentiation, we hypothesized that efficient expansion of functional HSPC could be achieved in vitro under more physiologic conditions provided by surrogate fetal liver microenvironments. Therefore, we compared bioengineered liver constructs made from a natural 3D liver extracellular matrix (3DExM) seeded with hepatoblasts (HB), fetal liver-derived stromal cells (FLSC), or bone marrow-derived stromal cells (BMSC), with a 2D culture system using FLSC or BMSC. Overall, 2D culture systems generated a higher yield of mature blood cells by day 14, mostly within the myelomonocytic lineages, with fold increases in total cell number in 2D-HB, 2D-FLSC, and 2D-BMSC cultures of 1145, 16151, and 229, respectively, while 3D cultures generated fold increases of 94.3, 492, and 110, respectively. Nevertheless, the output and expansion of more primitive HSPC was significantly higher in 3D cultures, as determined by flow cytometry and colony-forming assays. Specifically, in 3D-HB cultures, the percentage of CD34+CD38- cells increased by 100% at day 2, while 3D-FLSC and 3D-BMSC cultures each supported a 90% increase in the percentage of CD34+CD38- cells during this period. By contrast, all of the 2D cultures experienced a 30% decrease in the percentage of CD34+CD38- cells during this same time period. In addition, only 3D conditions maintained CD34+CD38- cells until day 12 of culture. Colony-forming assays demonstrated that the CFU-GEMM output was higher in 3D cultures when compared with their 2D counterpart. Among the 3D cultures, the 3D-HB cultures had the highest number of CFU-GEMM at day 2 and day 4. In conclusion, we demonstrate that by integrating biological components in vitro to obtain structures that contain all the necessary elements to mimic the fetal liver microenvironmental niches, which are known to promote rapid expansion of HSC during development, we were able to achieve significant expansion and maintenance of CD34+CD38- cells. In addition, since little is known about fetal liver niches that support HSPC expansion, the 3D constructs will provide, for the first time, a model system in which to dissect the role of the individual cellular and matrix niche components in supporting CB HSPC maintenance, expansion, and differentiation. Disclosures No relevant conflicts of interest to declare.

scholarly journals Bone marrow stromal cells from MDS and AML patients show increased adipogenic potential with reduced Delta-like-1 expression

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marie-Theresa Weickert ◽  
Judith S. Hecker ◽  
Michèle C. Buck ◽  
Christina Schreck ◽  
Jennifer Rivière ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Fate ◽  
Stromal Cells ◽  
Adipogenic Differentiation ◽  
Cell Types ◽  
Bone Marrow Niche ◽  
Differentiation Potential ◽  
Hematopoietic Stem ◽  
Bm Niche

AbstractMyelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are clonal hematopoietic stem cell disorders with a poor prognosis, especially for elderly patients. Increasing evidence suggests that alterations in the non-hematopoietic microenvironment (bone marrow niche) can contribute to or initiate malignant transformation and promote disease progression. One of the key components of the bone marrow (BM) niche are BM stromal cells (BMSC) that give rise to osteoblasts and adipocytes. It has been shown that the balance between these two cell types plays an important role in the regulation of hematopoiesis. However, data on the number of BMSC and the regulation of their differentiation balance in the context of hematopoietic malignancies is scarce. We established a stringent flow cytometric protocol for the prospective isolation of a CD73+ CD105+ CD271+ BMSC subpopulation from uncultivated cryopreserved BM of MDS and AML patients as well as age-matched healthy donors. BMSC from MDS and AML patients showed a strongly reduced frequency of CFU-F (colony forming unit-fibroblast). Moreover, we found an altered phenotype and reduced replating efficiency upon passaging of BMSC from MDS and AML samples. Expression analysis of genes involved in adipo- and osteogenic differentiation as well as Wnt- and Notch-signalling pathways showed significantly reduced levels of DLK1, an early adipogenic cell fate inhibitor in MDS and AML BMSC. Matching this observation, functional analysis showed significantly increased in vitro adipogenic differentiation potential in BMSC from MDS and AML patients. Overall, our data show BMSC with a reduced CFU-F capacity, and an altered molecular and functional profile from MDS and AML patients in culture, indicating an increased adipogenic lineage potential that is likely to provide a disease-promoting microenvironment.

scholarly journals Early megakaryocyte lineage-committed progenitors in adult mouse bone marrow

2021 ◽  
Author(s):  
Zixian Liu ◽  
Jinhong Wang ◽  
Miner Xie ◽  
Peng Wu ◽  
Yao Ma ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Single Cell ◽  
Pcr Analysis ◽  
Mouse Bone Marrow ◽  
Hematopoietic Stem ◽  
Colony Assay ◽  
Megakaryocyte Progenitors ◽  
Cell Colony

Hematopoietic stem cells (HSCs) have been considered to progressively lose their self-renewal and differentiation potentials prior to the commitment to each blood lineage. However, recent studies have suggested that megakaryocyte progenitors are generated at the level of HSCs. In this study, we newly identified early megakaryocyte lineage-committed progenitors (MgPs) in CD201-CD48- cells and CD48+ cells separated from the CD150+CD34-Kit+Sca-1+Lin- HSC population of the bone marrow in C57BL/6 mice. Single-cell transplantation and single-cell colony assay showed that MgPs, unlike platelet-biased HSCs, had little repopulating potential in vivo, but formed larger megakaryocyte colonies in vitro (on average eight megakaryocytes per colony) than did previously reported megakaryocyte progenitors (MkPs). Single-cell RNA-sequencing supported that these MgPs lie between HSCs and MkPs along the megakaryocyte differentiation pathway. Single-cell colony assay and single-cell RT-PCR analysis suggested the coexpression of CD41 and Pf4 is associated with megakaryocyte colony-forming activity. Single-cell colony assay of a small number of cells generated from single HSCs in culture suggested that MgPs are not direct progeny of HSCs. In this study, we propose a differentiation model in which HSCs give rise to MkPs through MgPs.

scholarly journals Heparin Anticoagulant for Human Bone Marrow Does Not Influence In Vitro Performance of Human Mesenchymal Stromal Cells

Cells ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1580
Author(s):  
Yvonne Roger ◽  
Laura Burmeister ◽  
Anika Hamm ◽  
Kirsten Elger ◽  
Oliver Dittrich-Breiholz ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Mesenchymal Stromal Cells ◽  
Stromal Cells ◽  
Mononuclear Cells ◽  
Population Doubling ◽  
Pcr Analysis ◽  
Inhibitory Influence ◽  
In Vitro Differentiation ◽  
Cell Surface Antigens

Mesenchymal stromal cells (MSCs) are a promising cell source for tissue engineering and regenerative medicine. In our lab, we found that MSC preparations from bone marrow of many different donors had a limited capacity of in vitro differentiation into osteogenic and chondrogenic lineages—a capacity claimed to be inherent to MSCs. The current study was designed to test the hypothesis that the amount of heparin used as anticoagulant during bone marrow harvest had an inhibitory influence on the in vitro differentiation capacity of isolated MSCs. Bone marrow was obtained from the femoral cavity of twelve donors during total hip arthroplasty in the absence or presence of heparin. No coagulation was observed in the absence of heparin. The number of mononuclear cells was independent of heparin addition. Isolated MSCs were characterized by morphology, population doubling times, expression of cell surface antigens and in vitro differentiation. Results of these analyses were independent of the amount of heparin. Transcriptome analyses of cells from three randomly chosen donors and quantitative realtime PCR (qRT-PCR) analysis from cells of all donors demonstrated no clear effect of heparin on the transcriptome of the cells. This excludes heparin as a potential source of disparate results.

scholarly journals Molecular Modulation of Fetal Liver Hematopoietic Stem Cell Mobilization into Fetal Bone Marrow in Mice

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Huihong Zeng ◽  
Jiaoqi Cheng ◽  
Ying Fan ◽  
Yingying Luan ◽  
Juan Yang ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Vascular Endothelial Cells ◽  
Fetal Liver ◽  
Bone Marrow Niche ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Fetal Bone

Development of hematopoietic stem cells is a complex process, which has been extensively investigated. Hematopoietic stem cells (HSCs) in mouse fetal liver are highly expanded to prepare for mobilization of HSCs into the fetal bone marrow. It is not completely known how the fetal liver niche regulates HSC expansion without loss of self-renewal ability. We reviewed current progress about the effects of fetal liver niche, chemokine, cytokine, and signaling pathways on HSC self-renewal, proliferation, and expansion. We discussed the molecular regulations of fetal HSC expansion in mouse and zebrafish. It is also unknown how HSCs from the fetal liver mobilize, circulate, and reside into the fetal bone marrow niche. We reviewed how extrinsic and intrinsic factors regulate mobilization of fetal liver HSCs into the fetal bone marrow, which provides tools to improve HSC engraftment efficiency during HSC transplantation. Understanding the regulation of fetal liver HSC mobilization into the fetal bone marrow will help us to design proper clinical therapeutic protocol for disease treatment like leukemia during pregnancy. We prospect that fetal cells, including hepatocytes and endothelial and hematopoietic cells, might regulate fetal liver HSC expansion. Components from vascular endothelial cells and bones might also modulate the lodging of fetal liver HSCs into the bone marrow. The current review holds great potential to deeply understand the molecular regulations of HSCs in the fetal liver and bone marrow in mammals, which will be helpful to efficiently expand HSCs in vitro.

Genetic and Functional Characterization of Isolated Stromal Cell Lines from the Aorta-Gonado-Mesonephros (AGM)-Region.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2328-2328
Author(s):  
Katja C. Weisel ◽  
Ying Gao ◽  
Jae-Hung Shieh ◽  
Lothar Kanz ◽  
Malcolm A.S. Moore
Keyword(s):  
Bone Marrow ◽  
B Cell ◽  
Cell Line ◽  
Cell Lines ◽  
Stromal Cells ◽  
Stromal Cell ◽  
Fetal Liver ◽  
Hematopoietic Stem ◽  
Stromal Cell Line ◽  
Mes Cells

Abstract The aorta-gonads-mesonephros (AGM) region autonomously generates adult repopulating hematopoietic stem cells (HSC) in the mouse embryo and provides its own HSC-supportive microenvironment. Stromal cells from adult bone marrow, yolk sac, fetal liver and AGM have been used in coculture systems for analysing growth, maintenance and differentiation of hematopoietic stem cells. We generated >100 cloned stromal cell lines from the AGM of 10.5 dpc mouse embryos. In previous studies, we tested these for support of murine adult and human cord blood (CB) CD34+ cells. We could demonstrate that 25 clones were superior to the MS5 bone marrow stromal cell line in supporting progenitor cell expansion of adult mouse bone marrow both, in 2ndry CFC and CAFC production. In addition we demonstrated that 5 AGM lines promoted in absence of exogenous growth factors the expansion of human CB cells with progenitor (CFC production for at least 5 weeks) and stem cell (repopulation of cocultured cells in NOD/SCID assay) function. Now, we could show that one of the isolated stromal cell lines (AGM-S62) is capable in differentiating undifferentiated murine embryonic stem (mES) cells into cells of the hematopoietic lineage. A sequential coculture of mES-cells with AGM-S62 showed production of CD41+ hematopoietic progenitor cells at day 10 as well as 2ndry CFC and CAFC production of day 10 suspension cells. Hematopoietic cell differentiation was comparable to standard OP9 differentiation assay. With these data, we can describe for the first time, that a stromal cell line other than OP9 can induce hematopoietic differentiation of undifferentiated mES cells. Hematopoietic support occurs independently of M-CSF deficiency, which is the characteristic of OP9 cells, because it is strongly expressed by AGM-S62. To evaluate genes responsible for hematopoietic cell support, we compared a supporting and a non-supporting AGM stromal cell line by microarray analysis. The cell line with hematopoietic support clearly showed a high expression of mesenchymal markers (laminins, thrombospondin-1) as well as characteristic genes for the early vascular smooth muscle phenotype (Eda). Both phenotypes are described for stromal cells with hematopoietic support generated from bone marrow and fetal liver. In addition, the analysed supporting AGM stromal cell line interestingly expressed genes important in early B-cell differentiation (osteoprotegerin, early B-cell factor 1, B-cell stimulating factor 3), which goes in line with data demonstrating early B-cell development in the AGM-region before etablishing of fetal liver hematopoiesis. Further studies will show the significance of single factors found to be expressed in microarray analyses. This unique source of > 100 various cell lines will be of value in elucidating the molecular mechanisms regulating embryonic and adult hematopoiesis in mouse and man.

The Rho Family GTPase Cdc42 Regulates Multiple Hematopoietic Stem/Progenitor Cell Functions and Erythropoiesis.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 32-32
Author(s):  
Lei Wang ◽  
Linda Yang ◽  
Marie–Dominique Filippi ◽  
David A. Williams ◽  
Yi Zheng
Keyword(s):  
Bone Marrow ◽  
Fetal Liver ◽  
Brdu Incorporation ◽  
Low Density ◽  
Actin Assembly ◽  
Wild Type ◽  
Hematopoietic Stem ◽  
Rho Family

Abstract The Rho family GTPase Cdc42 has emerged as a key signal transducer in cell regulation. To investigate its physiologic function in hematopoiesis, we have generated mice carrying a gene targeted null allele of cdc42gap, a major negative regulatory gene of Cdc42 and mice with conditional targeted cdc42 allele (cdc42flox/flox). Deletion of the respective gene products in mice was confirmed by PCR genotyping and Western blotting. Low-density fetal liver or bone marrow cells from Cdc42GAP−/− mice displayed ~3 fold elevated Cdc42 activity and normal RhoA, Rac1 or Rac2 activity, indicating that cdc42gap deletion has a specific effect on Cdc42 activity. The Cdc42GAP-deficient hematopoietic stem/progenitor cells (HSC/Ps, Lin−c-Kit+) generated from Cdc42GAP−/− E14.5 fetal liver and the Cdc42−/− HSC/Ps derived by in vitro expression of Cre via a retrovirus vector from Cdc42flox/flox low density bone marrow showed a growth defect in liquid culture that was associated with increased apoptosis but normal cell cycle progression. Cdc42GAP-deficient HSC/Ps displayed impaired cortical F-actin assembly with extended actin protrusions upon exposure to SDF–1 in vitro and a punctuated actin structure after SCF stimulation while Cdc42−/− but not wild type HSC/Ps responded to SDF-1 in inducing membrane protrusions. Both Cdc42−/− and Cdc42GAP−/− HSC/Ps were markedly decreased in adhesion to fibronectin. Moreover, both Cdc42−/− and Cdc42GAP−/− HSC/Ps showed impaired migration in response to SDF-1. These results demonstrate that Cdc42 regulation is essential for multiple HSC/P functions. To understand the in vivo hematopoietic function of Cdc42, we have characterized the Cdc42GAP−/− mice further. The embryos and newborns of homozygous showed a ~30% reduction in hematopoietic organ (i.e. liver, bone marrow, thymus and spleen) cellularity, consistent with the reduced sizes of the animals. This was attributed to the increased spontaneous apoptosis associated with elevated Cdc42/JNK/Bid activities but not to a proliferative defect as revealed by in vivo TUNEL and BrdU incorporation assays. ~80% of Cdc42GAP−/− mice died one week after birth, and the surviving pups attained adulthood but were anemic. Whereas Cdc42GAP−/− mice contained small reduction in the frequency of HSC markers and normal CFU-G, CFU-M, and CFU-GM activities, the frequency of BFU-E and CFU-E were significantly reduced. These results suggest an important role of Cdc42 in erythropoiesis in vivo. Taken together, we propose that Cdc42 is essential for multiple HSC/P functions including survival, actin cytoskeleton regulation, adhesion and migration, and that deregulation of its activity can have a significant impact on erythropoiesis. Cdc42 regulates HSC/P functions and erythropoiesis Genotype/phenotype Apoptosis increase Adhesion decrease Migration decrease F-actin assembly HSC frequency decrease BFU-E, CFU-E decrease The numbers were indicated as fold difference compared with wild type. ND:not determined yet. Cdc42GAP−/− 2.43, p<0.005 0.97, p<0.01 1.01, p<0.01 protrusion (SDF-1); punctruated (SCF) 0.34, p<0.05 0.92, p<0.01; 0.38, p<0 Cdc42−/− 3.68, p<0.005 0.98, p<0.001 3.85, p<0.005 protrusion (SDF-1) ND ND

Induction of Adipocyte Differentiation and Reduction of Hematopoesis-Supporting Activity of Mouse Stromal Cells by Suppression of Transcription Factor GATA-2.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1392-1392
Author(s):  
Yoko Okitsu ◽  
Hideo Harigae ◽  
Masanori Seki ◽  
Toru Fujiwara ◽  
Shinichiro Takahashi ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Transcription Factor ◽  
Hematopoietic Stem Cells ◽  
Stromal Cells ◽  
Colony Formation ◽  
Adipocyte Differentiation ◽  
Fetal Liver ◽  
Expression Level ◽  
Hematopoietic Stem

Abstract (Introduction) Aplastic anemia (AA) is characterized by peripheral pancytopenia and fatty bone marrow. An immunological attack to hematopoietic stem cells has been thought to be responsible for the development of the disease. Previously, we reported the expression of transcription factor GATA-2 is significantly decreased in CD34 positive cells in AA. Together with the phenotypes of hematopoietic stem cells in GATA-2 hetero-knockout mice, GATA-2 down-regulation may play a role in the reduction of a stem cell pool observed in AA. On the other hand, GATA-2 has been shown to be essential for the maintenance of immaturity of preadipocytes. If a pathological immune response in AA decreases the level of GATA-2 expression in not only hematopoietic stem cells but also stromal preadipocytes, it may accelerate the maturation of preadipocytes, leading to the formation of fatty bone marrow. To explore this possibility, the phenotypic change of stromal preadipocytes by suppression of GATA-2 was examined in this study. (Method) The GATA-2 expression level was suppressed by using siRNA for GATA-2 in mouse stromal preadipocyte cell lines, TBR9 and TBR343. After the treatment with siRNA, the adipocyte differentiation was induced by the incubation with insulin and dexamethasone for 7days. Then, the maturation level was examined by oil drops formation judged by oil red staining, and by the expression level of adipcin and PPAR-γ mRNA. Supporting activity of hematopoietic colony formation was also evaluated by using mouse fetal liver cells after siRNA treatment. (Results) By using designed siRNA, the GATA-2 expression was suppressed to 30% of control, whereas the expression level of GATA-3, which is co-expressed in preadipocytes, was unchanged. When GATA-2 was suppressed by siRNA, the oil drop formation and adipocyte-specific gene expression was significantly accelerated in both of stromal cells. Furthermore, the number of fetal liver hematopoetic colonies was significantly decreased by suppression of GATA-2, suggesting that GATA-2 down-regulation in stromal preadipocytes results in not only the acceleration of the maturation but also the reduced supporting activity of hematopoietic colony formation (Conclusion) These results suggest that suppression of GATA-2 in hematopoietic tissues induces the characteristic features of AA, i.e., decreased the number of hematopoietic stem cells and increased number of mature adipocytes.

Integrin alpha 6 Is Essential for Fetal Hematopoietic Progenitor, but Not Fetal Stem Cell Homing to Bone Marrow.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1387-1387
Author(s):  
Hong Qian ◽  
Sten Eirik W. Jacobsen ◽  
Marja Ekblom
Keyword(s):  
Bone Marrow ◽  
Stem Cell ◽  
Progenitor Cells ◽  
Progenitor Cell ◽  
Fetal Liver ◽  
Hematopoietic Stem ◽  
Stem And Progenitor Cells ◽  
Integrin Alpha 6

Abstract Homing of transplanted hematopoietic stem cells (HSC) in the bone marrow (BM) is a prerequisite for establishment of hematopoiesis following transplantation. However, although multiple adhesive interactions of HSCs with BM microenviroment are thought to critically influence their homing and subsequently their engraftment, the molecular pathways that control the homing of transplanted HSCs, in particular, of fetal HSCs are still not well understood. In experimental mouse stem cell transplantation models, several integrins have been shown to be involved in the homing and engraftment of both adult and fetal stem and progenitor cells in BM. We have previously found that integrin a6 mediates human hematopoietic stem and progenitor cell adhesion to and migration on its specific ligands, laminin-8 and laminin-10/11 in vitro (Gu et al, Blood, 2003; 101:877). Furthermore, integrin a6 is required for adult mouse HSC homing to BM in vivo (Qian et al., Abstract American Society of Hematology, Blood 2004 ). We have now found that the integrin a6 chain like in adult HSC is ubiquitously (>99%) expressed also in fetal liver hematopoietic stem and progenitor cells (lin−Sca-1+c-Kit+, LSK ). In vitro, fetal liver LSK cells adhere to laminin-10/11 and laminin-8 in an integrin a6b1 receptor-dependent manner, as shown by function blocking monoclonal antibodies. We have now used a function blocking monoclonal antibody (GoH3) against integrin a6 to analyse the role of the integrin a6 receptor for the in vivo homing of fetal liver hematopoietic stem and progenitor cells to BM. The integrin a6 antibody inhibited homing of fetal liver progenitors (CFU-C) into BM of lethally irradiated recipients. The number of homed CFU-C in BM was reduced by about 40% as compared to the cells incubated with an isotype matched control antibody. To study homing of long-term repopulating stem cells, BM cells were first incubated with anti-integrin alpha 6 or anti-integrin alpha 4 or control antibody, and then injected intravenously into lethally irradiated primary recipients. After three hours, BM cells of the primary recipients were analysed by competitive repopulation assay in secondary recipients. Blood analysis up to 16 weeks after transplantation showed that no reduction of stem cell reconstitution from integrin a6 antibody treated cells as compared to cells treated with control antibody. In accordance with this, fetal liver HSC from integrin a6 gene deleted embryos did not show any impairment of homing and engraftment in BM as compared to normal littermates. These results suggest that integrin a6 plays an important developmentally regulated role for homing of distinct hematopoietic stem and progenitor cell populations in vivo.

Sign in / Sign up

Export Citation Format

Share Document