scholarly journals The incredible journey: From megakaryocyte development to platelet formation

2013 ◽  
Vol 201 (6) ◽  
pp. 785-796 ◽  
Author(s):  
Kellie R. Machlus ◽  
Joseph E. Italiano
Keyword(s):  
Bone Marrow ◽  
Blood Vessel ◽  
Blood Vessels ◽  
Progenitor Cells ◽  
Branching Processes ◽  
Blood Platelets ◽  
Clinical Applications ◽  
Active Area ◽  
Vessel Injury ◽  
Platelet Formation

Circulating blood platelets are specialized cells that prevent bleeding and minimize blood vessel injury. Large progenitor cells in the bone marrow called megakaryocytes (MKs) are the source of platelets. MKs release platelets through a series of fascinating cell biological events. During maturation, they become polyploid and accumulate massive amounts of protein and membrane. Then, in a cytoskeletal-driven process, they extend long branching processes, designated proplatelets, into sinusoidal blood vessels where they undergo fission to release platelets. Given the need for platelets in many pathological situations, understanding how this process occurs is an active area of research with important clinical applications.

Hemangiogenic Role of ELF4 in Bone Marrow Post Myeloablation.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1783-1783
Author(s):  
Mariela Sivina ◽  
Takeshi Yamada ◽  
Natalie Dang ◽  
H. Daniel Lacorazza
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Endothelial Cells ◽  
Hematopoietic Stem Cells ◽  
Blood Vessels ◽  
Progenitor Cells ◽  
Endothelial Progenitor Cells ◽  
Bone Marrow Cells ◽  
Hematopoietic Stem ◽  
Huvec Cells

Abstract Bone marrow suppression is an important cause of death in patients exposed to radiation or in cancer patients treated with conventional chemotherapeutic agents. Myeloablative treatments (i.e. 5-fluorouracil administration) lead to apoptosis of blood forming cells and to regression of blood vessels in bone marrow. It is well known that hematological recovery post-bone marrow insult depends on the capacity of hematopoietic stem cells to regenerate the entire hematopoietic system, however, the transcriptional machinery involved in the regeneration of sinusoidal blood vessels in bone marrow from endothelial progenitor cells is largely unknown. Endothelial cells express the Tie2 receptor tyrosine kinase (a.k.a. Tek), which is involved in the angiogenic remodeling and vessel stabilization. Gene targeting of Tie2 showed that it is not required for differentiation and proliferation of definitive hematopoietic lineages in the embryo although Tie2 is needed during postnatal bone marrow hematopoiesis. ELF is a subgroup of the ETS family of transcription factors composed by ELF1, ELF2 (a.k.a. NERF), ELF3, ELF4 (a.k.a. MEF) and ELF5. ELF1 and ELF2 have been shown to regulate Tie2 expression in vitro. Recently we showed that ELF4 modulates the exit of hematopoietic stem cells (HSC) from quiescence (Lacorazza et al., Cancer Cell2006, 9:175–187). Given the high homology between ELF1 and ELF4 and the same origin of HSC and endothelial progenitor cells, we hypothesize that ELF4 regulates proliferation and Tie2 expression of endothelial cells. We used a luciferase gene reporter system in COS-7 and HEK cells to examine the capacity of ELF proteins to activate Tie2. ELF4 is the strongest activator of Tie2 expression following the hierarchy ELF4>ELF1>ELF2 variant 1>ELF2 variant 2. Site directed mutagenesis of each of the five ETS-binding sites (EBS) present in the Tie2 promoter shows that ELF4 binds preferentially to EBS 1, 3 and 5. Binding of ELF4 to the Tie2 promoter was confirmed by chromatin immunoprecipitation and EMSA. Although Elf1 gene expression is essentially normal in Elf4−/− bone marrow cells collected after 5-FU treatment, we detected diminished Tie2 expression compared to Elf4+/+ bone marrow cells. The association of this effect to human endothelial cells derived from umbilical cord (HUVEC cells) was investigated. All-trans retinoic acid (ATRA) and vascular-endothelial growth factor (VEGF) induced ELF4 expression in HUVEC cells in a dose and time dependent manner which was followed by increased Tie2 expression, suggesting that expression of ELF4 is modulated by angiogenic signals. Moreover, endothelial cells treated with ATRA showed rapid wound colonization in a wound assay. Expression of the pan-endothelial marker MECA-32 was determined by immunohistochemistry to correlate Tie2 with the regeneration of blood vessels: myeloablated Elf4−/− femurs exhibited a reduction of MECA-32 positive arterioles. Finally, temporal and spatial expression of Tie2 during hematological recovery post ablation was measured in bone marrow using transgenic Tie2-LacZ mice crossed to Elf4−/− mice. Collectively, our data suggests that ELF4 regulates Tie2 expression in endothelial cells but most importantly their proliferative capacity in response to angiogenic signals.

Hematopoietic Functions of the Tumor Supressor Von Hippel Lindau (VHL) in the Etiology of Hemangioblastoma.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2425-2425
Author(s):  
Hannah L Bader ◽  
Tracy Pritchett ◽  
Tien Hsu
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Flow Cytometry ◽  
Mouse Model ◽  
Gall Bladder ◽  
Blood Vessels ◽  
Progenitor Cells ◽  
Liver Lesions ◽  
Endothelial Lining ◽  
Knock Out

Abstract Abstract 2425 Germline heterozygous mutation in the VHL tumor suppressor gene is the underlying genetic defect in VHL disease. Cancer arises when the function of the remaining wildtype allele is lost. VHL patients are prone to develop renal cell carcinoma of the clear cell type (ccRCC) and hemangioblastoma (HB). VHL mutations underlie also the majority of sporadic ccRCC and HB. HB are highly vascularized tumors of the central nervous system. However, it is unclear from which tissue HB arise (reviewed in (1)). Although HB are sometimes described as vascular tumors, inactivation of both VHL alleles has been detected only in the stromal component, suggesting that abnormal angiogenesis is driven by cytokines released from the tumor rather than by VHL inactivation in the endothelium. There is evidence that hematopoietic stem cells or early progenitor cells are involved in the formation of HB. For instance, advanced HB are frequently accompanied by extramedullary erythropoiesis (EME) (2,3). Previously, overgrowth of blood vessels (hemangioma) has been observed in the liver of constitutive heterozygous Vhl knock-out mice, and in a hepatocyte specific Vhl conditional knock-out (albumin-cre) (4). Here, we present a mouse model that may shed light on another aspect of HB, e.g. EME. We used HOXB7-cre for the conditional deletion of VHL in a subset of kidney tubules (HOXB7-Vhl mice). Interestingly, we found that these mice developed not only a kidney phenotype, but also liver lesions. At 2–3 months of age, blood filled bulges developed close to the gall bladder (see Fig. 1A). Superficially, these lesions resembled previously described hemangiomas. However, histology revealed large blood lakunae that were not lined by blood vessels (Fig 1B). Hence, lesions appeared to arise not due to an overgrowth of blood vessels, but due to EME, with massive accumulation of red blood cells surrounding foci of nucleated progenitor cells (Fig. 1C). Fig. 1. Liver lesions in HOXB7-Vhl mice. A: Blood filled bulges form close to the gall bladder (arrowheads). B, C: Histology. Note lakunae of blood (L) without endothelial lining (B), and foci of progenitor cells (arrow in C). Fig. 1. Liver lesions in HOXB7-Vhl mice. A: Blood filled bulges form close to the gall bladder (arrowheads). B, C: Histology. Note lakunae of blood (L) without endothelial lining (B), and foci of progenitor cells (arrow in C). CFU assays with liver cell suspensions confirmed EME: there was a significant increase in the number of liver BFUs in HOXB7-Vhl mice. HOXB7-Vhl mice had also elevated levels of EPO in the serum, and flow cytometry showed an increase in TER119+CD71+ erythrocyte progenitors in the spleen, but not the bone marrow. Despite EME and elevated EPO levels, HOXB7-VHL mice displayed only rarely polycythemia. In this context, it is noteworthy that VHL patients also present frequently with elevated EPO levels, without developing polycythemia. Interestingly, the majority of HoxB7-VHL mice developed thrombocytopenia, possibly due to the leakiness of the blood vasculature in the liver lesions. However, flow cytometry showed also a decrease in megakaryocytes (CD41+) in both bone marrow and spleen, and in addition to an increase of erythrocyte progenitors, an increase in TER119+CD41+ common megakaryocyte-erythrocyte progenitors (MEP) in the spleen. It is therefore possible that differentiation of the MEP is shifted towards the erythrocyte lineage in the HOXB7-Vhl mouse. We found no evidence of Vhl deletion in the liver of HOXB7-Vhl mice using LacZ reporter mice. Our mouse model suggests therefore a systemic etiology of HB. One of the best known functions of VHL is the negative regulation of the hypoxia-inducible factor (HIF). Besides EPO, the chemokine receptor CXCR4 is also a known HIF-responsive gene (5) that could be potentially disregulated by Vhl deletion. Furthermore, preliminary data indicate that constitutive heterozygous VHL mice show 50% mortality in transplantation experiments, irrespective of the genotype of transplanted stem cells (e.g. wt or VHL +/−). Hence, in addition to cell autonomous and systemic mechanisms, defects in the bone marrow environment may underlie hematologic presentations of VHL deficiency. Disclosures: No relevant conflicts of interest to declare.

Negative regulation of activated α2 integrins during thrombopoiesis

Blood ◽  
2009 ◽  
Vol 113 (25) ◽  
pp. 6428-6439 ◽  
Author(s):  
Zhiying Zou ◽  
Alec A. Schmaier ◽  
Lan Cheng ◽  
Patricia Mericko ◽  
S. Kent Dickeson ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Ex Vivo ◽  
Hematopoietic Cells ◽  
Surface Expression ◽  
Wild Type ◽  
Vessel Injury ◽  
Rapid Signaling ◽  
Α2 Receptors

Abstract Circulating platelets exhibit rapid signaling and adhesive responses to collagen that facilitate hemostasis at sites of vessel injury. Because platelets are anuclear, their collagen receptors must be expressed by megakaryocytes, platelet precursors that arise in the collagen-rich environment of the bone marrow. Whether and how megakaryocytes regulate collagen adhesion during their development in the bone marrow are unknown. We find that surface expression of activated, but not wild-type, α2 integrins in hematopoietic cells in vivo results in the generation of platelets that lack surface α2 receptors. Culture of hematopoietic progenitor cells ex vivo reveals that surface levels of activated, but not wild-type, α2 integrin receptors are rapidly down-regulated during cell growth on collagen but reach wild-type levels when cells are grown in the absence of collagen. Progenitor cells that express activated α2 integrins are normally distributed in the bone marrow in vivo and exhibit normal migration across a collagen-coated membrane ex vivo. This migration is accompanied by rapid down-regulation of activated surface integrins. These studies identify ligand-dependent removal of activated α2 receptors from the cell surface as a mechanism by which integrin function can be negatively regulated in hematopoietic cells during migration between the adhesive environment of the bone marrow and the nonadhesive environment of the circulating blood.

Congenital disorders associated with platelet dysfunctions

2008 ◽  
Vol 99 (02) ◽  
pp. 253-263 ◽  
Author(s):  
Paquita Nurden ◽  
Alan T. Nurden
Keyword(s):  
Bone Marrow ◽  
Blood Platelets ◽  
Severe Bleeding ◽  
Spontaneous Bleeding ◽  
Atp Production ◽  
Bleeding Management ◽  
Giant Platelet ◽  
Platelet Morphology ◽  
Vessel Injury ◽  
Adp Receptor

SummaryGenetic defects of the megakaryocyte lineage give rise to bleeding syndromes of varying severity. Blood platelets are unable to fulfill their hemostatic function of preventing blood loss on vessel injury. Spontaneous bleeding is mostly mucocutaneous in nature. Most studied are deficiencies of glycoprotein (GP) mediators of adhesion (Bernard-Soulier syndrome) and aggregation (Glanzmann thrombasthenia) which concern the GPIb-IX-V complex and the integrin αIIbβ3, respectively. Defects of primary receptors for stimuli include the P2Y12 ADP receptor pathology. Agonist-specific deficiencies in the platelet aggregation response and abnormalities of signaling pathways are common and lead to trauma-related bleeding. Inherited defects of secretion from storage organelles, of ATP production, and of the generation of procoagulant activity are also encountered. In some disorders, such as the Chediak-Higashi, Hermansky-Pudlak, Wiskott-Aldrich and Scott syndromes, the molecular lesion extends to other cells. In familial thrombocytopenia (FT), platelets are produced in insufficient numbers to assure haemostasis. Some of these disorders affect platelet morphology and give rise to the so-called ‘giant platelet’ syndromes (MYH9-related diseases) with changes in megakaryocyte maturation within the bone marrow and premature release of platelets. Diseases of platelet production may extend to other cells and in some cases interfere with development. Transfusion of platelets remains the most common treatment of severe bleeding, management with desmopressin is common for mild disorders. Substitute therapies are available including rFVIIa and the potential use of TPO analogues for FT. Stem cell or bone marrow transplanation is being used for severe diseases while gene therapy may be on the horizon.

Morphology of Haemostatic Plugs Before and After Aspirin

1975 ◽  
Author(s):  
J. Wester ◽  
J. van der Veen ◽  
J. J. Sixma
Keyword(s):  
Blood Vessel ◽  
Blood Vessels ◽  
Bleeding Time ◽  
Blood Platelets ◽  
The Other ◽  
Normal Volunteers ◽  
Other Hand ◽  
Before And After

Punch biopsies of bleeding time wounds according to Mielke were taken at 3 minutes in normal volunteers before and 2.5 hours after 2 gr. of aspirin. Haemostatic plugs were found at the end of blood vessels. No plug was encountered that had no relation to a blood vessel. Fibrin on the other hand was found in the wound but not in the blood vessel. Some vessels were occluded by capsule-like haemostatic plugs. In many others an extension into the blood vessel was observed. The extension into the blood vessel showed little or no degranulation. Blood platelets were more degranulated and showed peripheral ballooning before aspirin intake. After aspirin intake much less degranulation was observed and less peripheral ballooning was found.

Maturation of blood vessels by haematopoietic stem cells and progenitor cells: Involvement of apelin/APJ and angiopoietin/Tie2 interactions in vessel caliber size regulation

2009 ◽  
Vol 101 (06) ◽  
pp. 999-1005 ◽  
Author(s):  
Hiroyasu Kidoya ◽  
Nobuyuki Takakura
Keyword(s):  
Stem Cells ◽  
Blood Vessel ◽  
Single Cell ◽  
Blood Vessels ◽  
Progenitor Cells ◽  
De Novo ◽  
Tube Formation ◽  
Haematopoietic Stem Cells ◽  
Molecular Control ◽  
Central Nervous Systems

SummaryApelin is a recently-isolated bioactive peptide from bovine gastric extract. The gene encodes a protein of 77 amino acids, which can generate two active polypeptides, long (42–77) and short (65–77). Both peptides ligate and activate APJ, a G protein-coupled receptor expressed in the cardiovascular and central nervous systems. Although an essential role for the apelin/APJ system in blood vessel formation has been reported in Xenopus, its precise function in mammals is unclear. Blood vessel tube formation is accomplished by two main mechanisms: 1) single cell hollowing, in which a lumen forms within the cytoplasm of a single endothelial cell (EC), and 2) cord hollowing in which a luminal cavity is created de novo between ECs in a thin cylindrical cord. Molecular control of either single cell or cord hollowing has not been precisely determined. Angiopoietin-1 (Ang1) has been reported to induce enlargement of blood vessels. Apelin is produced from ECs upon activation of Tie2, a cognate receptor of Ang1, expressed on ECs. It has been suggested that apelin induces cord hollowing by promoting proliferation and aggregation/assembly of ECs. During angiogenesis, haematopoietic stem cells (HSCs) and progenitor cells (HPCs) are frequently observed in the perivascular region. They produce Ang1 and induce migration of ECs, resulting in a fine vascular network. Moreover, HSCs/HPCs can induce apelin production from ECs. Therefore, this review article posits that HSCs/HPCs regulate caliber size of blood vessels via apelin/APJ and Angiopoietin/Tie2 interactions.

Distinct Bone Marrow Blood Vessels Differentially Regulate Normal and Malignant Hematopoietic Stem and Progenitor Cells

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 664-664
Author(s):  
Tomer Itkin ◽  
Shiri Gur Cohen ◽  
Joel A. Spencer ◽  
Amir Schajnovitz ◽  
Saravana K. Ramasamy ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Blood Plasma ◽  
Blood Vessels ◽  
Progenitor Cells ◽  
Peripheral Blood ◽  
Progenitor Cell ◽  
Leukocyte Trafficking ◽  
Hematopoietic Stem ◽  
Barrier Integrity ◽  
Stem And Progenitor Cells

Abstract Bone marrow (BM) endothelial cells (BMECs) form a network of blood vessels (BVs) that regulate both leukocyte trafficking and hematopoietic stem and progenitor cell (HSPC) maintenance. However, it is not clear how BMECs balance between these dual regulatory roles and if these events occur at the same vascular site. We define the BM architecture of functionally distinct BVs, their spatial localization and association with specific stromal precursors, which cooperatively regulate HSPC fate. BM stem and progenitor cell maintenance in a metabolically non-active state and leukocyte trafficking occur at separate sites and are differentially regulated by specific BVs with distinct permeability properties. BM arteries were found to be mostly encircled by aSMA+ pericytes whereas the ensuing small-diameter endosteal and trabecular arterioles were predominantly surrounded by stem cell-niche supporting stromal precursor cells. Live imaging and flow analysis revealed that endosteal arteriole BVs exhibited high flow rate, low permeability to external plasma from the peripheral blood, and high levels of adhesion- and tight-junction molecules. Primitive HSPCs located in peri-arteriole regions were found in a non-activated, low reactive oxygen species (ROS) state. Exposure of BM HSPCs to peripheral blood plasma, enhanced their metabolic activity, exhibited by enhanced intracellular ROS levels, and glucose uptake. The same was also evident for circulating HSPCs in the blood. Plasma-exposed HSPCs displayed enhanced motility alongside with reduced long-term repopulation potential. Live imaging showed that all immature and mature leukocyte bi-directional trafficking occurred exclusively at the more permeable sinusoids, located downstream to the endosteal arterioles. Of note, BM sinusoids contained a higher prevalence of ROShigh cells in their microenvironment, including HSPCs. Rapid AMD3100-induced HSPC mobilization preferentially affected sinusoidal but not arterial BVs permeability and CXCL12 chemokine release. Endothelial specific in vivo interference with CXCL12-CXCR4 interactions, via conditional CXCR4 genetic deletion, hampered BM barrier integrity resulting in enhanced HSPC egress. In line with these results we found that during conditions favoring BM stem and progenitor cells expansion, endothelial integrity was enhanced along with reduced HSPC bi-directional trafficking. Conversely, conditional endothelial specific induced genetic or pharmacologic disruption of barrier integrity augmented ROS levels in HSPCs, enhancing their bi-directional trafficking and differentiation while reducing their BM pool size and maintenance in a metabolically non-active state. Of note, humanized mice engrafted with pre-B ALL cells exhibited reduced BM barrier permeability most probably due to BM endothelium modification via FGF-2 secretion by the leukemic clone. Interestingly, human pre-B ALL cells displayed hypersensitivity to plasmatic exposure. We hypothesize that malignant cells modify BM endothelium to provide themselves with a supportive and protective microenvironment composed of undifferentiated BM stromal progenitors and tightly sealed endothelial barrier. In conclusion, our study identifies anatomically distinct BM BVs with different barrier functions serving as systemic leukocyte trafficking or HSPC BM maintenance sites with clinical therapeutic relevance. Disclosures Rafii: Angiocrine Bioscience: Consultancy, Equity Ownership.

scholarly journals Blood platelet formation at a glance

2020 ◽  
Vol 133 (20) ◽  
pp. jcs244731
Author(s):  
Julie Boscher ◽  
Ines Guinard ◽  
Anita Eckly ◽  
François Lanza ◽  
Catherine Léon
Keyword(s):  
Bone Marrow ◽  
Blood Platelets ◽  
Blood Platelet ◽  
Main Function ◽  
Formation Processes ◽  
Bona Fide ◽  
Platelet Formation

ABSTRACTThe main function of blood platelets is to ensure hemostasis and prevent hemorrhages. The 1011 platelets needed daily are produced in a well-orchestrated process. However, this process is not yet fully understood and in vitro platelet production is still inefficient. Platelets are produced in the bone marrow by megakaryocytes, highly specialized precursor cells that extend cytoplasmic projections called proplatelets (PPTs) through the endothelial barrier of sinusoid vessels. In this Cell Science at a Glance article and the accompanying poster we discuss the mechanisms and pathways involved in megakaryopoiesis and platelet formation processes. We especially address the – still underestimated – role of the microenvironment of the bone marrow, and present recent findings on how PPT extension in vivo differs from that in vitro and entails different mechanisms. Finally, we recapitulate old but recently revisited evidence that – although bone marrow does produce megakaryocytes and PPTs – remodeling and the release of bona fide platelets, mainly occur in the downstream microcirculation.

scholarly journals A role for fat precursors in the marrow

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Noriaki Ono
Keyword(s):  
Bone Marrow ◽  
Blood Vessels ◽  
Progenitor Cells ◽  
Mesenchymal Progenitor Cells

A group of cells that can become adipocytes controls the formation of blood vessels in the bone marrow, and also regulates the differentiation of resident mesenchymal progenitor cells.

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