Endothelial Cell Division Research Articles

Alternating electric fields transform the intricate network of tumour vasculature into orderly parallel capillaries and enhance the anti-angiogenesis effect of bevacizumab.

The search for effective strategies to target tumour angiogenesis remains a critical goal of cancer research. We present a pioneering approach using alternating electric fields to inhibit tumour angiogenesis and enhance the therapeutic efficacy of bevacizumab. Chicken chorioallantoic membrane, cell viability and in vitro endothelial tube formation assays revealed that electric fields with a frequency of 1000 kHz and an electric intensity of 0.6 V/cm inhibited the growth of vascular endothelial cells and suppressed tumour-induced angiogenesis. In an animal U87MG glioma model, 1000 kHz electric fields inhibited tumour angiogenesis and suppressed tumour growth. As demonstrated by 3D vessel analysis, tumour vasculature in the control group was a stout, interwoven network. However, electric fields transformed it into slim, parallel capillaries that were strictly perpendicular to the electric field direction. This architectural transformation was accompanied by apoptosis of vascular endothelial cells and a notable reduction in tumour vessel number. Additionally, we found that the anti-angiogenesis and tumour-suppression effects of electric fields synergised with bevacizumab. The anti-angiogenic mechanisms of electric fields include disrupting spindle formation during endothelial cell division and downregulating environmental angiogenesis-related cytokines, such as interleukin-6, CXCL-1, 2, 3, 5 and 8, and matrix metalloproteinases. In summary, our findings demonstrate the potential of alternating electric fields (AEFs) as a therapeutic modality to impede angiogenesis and restrain cancer growth.

Association of VEGFA polymorphisms with the risk of oesophageal cancer in Punjab, India: A case-control study.

Background & objectives Vascular endothelial growth factor (VEGF) is one of the most important angiogenic factors which stimulates tumour progression induction of endothelial cell migration and division, inhibition of the apoptosis of endothelial cells, induction of serine protease activity and enhancement of vascular permeability. This study aimed to investigate the correlation of VEGF+405G/C,-7C/T and+936C/T polymorphisms with oesophageal cancer risk. Methods DNA samples of 464 subjects (231 sporadic oesophageal cancer affected individuals and 233 controls) were genotyped forVEGF+936C/T,+405G/C and-7C/T polymorphisms. VEGF+936C/T and +405G/C polymorphisms were genotyped by PCR-RFLP method whereas VEGF-7C/T polymorphism was genotyped using Amplification refractory mutation system-polymerase chain reaction (ARMS-PCR). Results CT genotype of VEGF-7C/T polymorphism was significantly associated with reduced risk of oesophageal cancer. VEGF-7C/T polymorphism was significantly associated with reduced risk of oesophageal cancer underdominant, co-dominant, over dominant and log-additive genetic models in total patients and in the female group. C+936G+405T-7 haplotype was significantly associated with decreased risk (P=0.01)of oesophageal cancer in total patients and also in the male group (P=0.02). Interpretation & conclusions In future, replication of the findings of the present study in a larger sample from different ethnic groups, along with functional analysis, may be insightful for the role of VEGFA polymorphisms in the pathogenesis of oesophageal cancer. Identification of the correlation of VEGF variants with specific therapy in oesophageal cancer may help in better selection of patients and monitoring treatment response in VEGF-therapy.

Tea polyphenols (TPP) as a promising wound healing agent: TPP exerts multiple and distinct mechanisms at different phases of wound healing in a mouse model

Polyphenols have been widely used to treat various chronic skin diseases because they are beneficial in wound healing and show anti-inflammatory effects, however, the mechanism of action remains ambiguous. Previously, we reported the wound healing capability of tea polyphenols (TPP), the major functional component of tea, in vivo. The current study aimed to address the mechanisms of TPP in wound healing during different phases (inflammation, proliferation and remodeling). During the inflammation phase, TPP reduced the production of proinflammatory cytokines (IL-1β, IL-6 and TNF-α) and inhibited infiltration of neutrophils; during the proliferation phase, TPP promoted the expression of growth factor VEGF-A, which can promote vascular endothelial cell division and induce angiogenesis; TPP improved the morphology of the wound and restored the ratio of type III/I collagens during the remodeling phase, as determined by Masson-trichrome staining and Sirius red staining assays. By tracking the changes in the wound area, TPP and recombinant human epidermal growth factor (rhEGF), rather than povidone-iodine (PVP-I), were able to promote wound healing. These results suggest that TPP plays a pivotal role in all the key stages of wound healing and displays distinct mechanisms from rhEGF, suggesting clinical significance for the future application of TPP as a natural wound healing agent.

Research Progress of Serum VEGF and FAS in Prognosis of Gastric Cancer

Vascular endothelial growth factor (VEGF) is an important factor to promote endothelial cell division and angiogenesis. In physiological conditions, the expression level of VEGF in human tissues is very low. Ischemia, hypoxia and many tumors can promote the synthesis and secretion of VEGF, and its expression level is related to the degree of vascularization of tumors, the proliferation, growth and metastasis of tumor cells. Fatty acid synthase (FAS) is a key enzyme for endogenous fatty acid synthesis, which is expressed at a low level in normal tissue cells, while FASN in a variety of tumor cells is continuously highly expressed to meet the energy needs of cell proliferation and the excessive demand for rapid proliferation of tumor cells to form cell membrane lipids. A large amount of research shows that VEGF and FAS play an important role in the development and development of many tumors, and the abnormally high expression in tumor tissue cells is positively correlated with serum VEGF and FAS levels, which is closely related to the prognosis of tumors. Gastric cancer (GC) is one of the most common clinical malignant tumors of the digestive tract, and its incidence and mortality have shown an increasing trend in recent years, and the prognosis is poor, seriously endangering human health. The biological properties of GC are related to the level of VEGF and FAS expression in tissues and serum. This article reviews the research progress of VEGF and FAS, their expression in GC and their prognosis.

Multi-scale model of lumen formation via inverse membrane blebbing mechanism during sprouting angiogenesis process

Cancer is one of the leading causes of mortality and morbidity among people worldwide. Cancer appears as solid tumors in many cases. Angiogenesis is the growth of blood vessels from the existing vasculature and is one of the imperative processes in tumor growth. Another vital phenomenon for formation and functionality of this vasculature network is lumen formation. The results of recent studies indicate the importance of blood pressure in this mechanism. Computational modeling can study these processes in different scales. Hence, wide varieties of these models have been proposed during recent years. In this research, a multi-scale model is developed for the angiogenesis process. In the extracellular scale, the growth factor concentration is calculated via the reaction diffusion equation. At the cellular scale, growth, migration, and the adhesion of endothelial cells are modeled by the Potts cellular model. At the intra-cellular scale by considering biochemical signals, a Boolean network model describes migration, division, or apoptosis of endothelial cells. A stochastic model developed for lumen formation via inverse membrane blebbing mechanism. A CFD simulation was also used to investigate the role of pulsated blood pressure in the inverse membrane blebbing mechanism. The lumen formation model shows stochastic behavior in blebs expansion and lumen expansion. Comparing the stochastic model's results with the CFD simulation also shows the vital role of pressure pulse and the topology of the blebs in bleb retraction.

Feasibility of Growth Factor Agent Therapy in Repairing Motor Injury.

Growth factors (GF), with the activity of stimulating cell growth, play a significant role in biology, medicine, and exercise physiology. In the process of exercise, human tissues are impacted, making cells suffer damage. Growth factor can accelerate the repair of damaged cells and regulate the synthesis of protein, so biological preparations of growth factors can be added to traditional therapies. A combination of growth factor biologics and conventional therapies may improve the efficiency of injury repair, but growth factor biologics may not produce any results. The feasibility of growth factor biologics in the treatment of motor injury was discussed. The research have shown that: 1) GF biological agent therapy is a very promising treatment for motor injury, which is based on the power of autologous growth factor (GFs) to accelerate tissue healing, promote muscle regeneration, increase angiogenesis, reduce fibrosis, and make the muscle injury rapid recovery. 2) There are various methods for delivering the higher dose of GF to the injured tissue, but most of them depend on the platelet release of GF. At the site of injury, there are several ways to deliver higher doses of GF to the injured tissue. 3) At present, the inhibition of GF is mainly through signal transduction inhibitors and inhibition of transcription factor production. 4) Pattern of GF during wound repair: GF directly regulates many key steps of normal wound repair, including inflammatory cell chemotaxis, division and proliferation of fibroblasts, keratinocytes and vascular endothelial cells, formation of new blood vessels, and synthesis and degradation of intercellular substances. 5) When GF promotes chronic wound healing, in most cases, certain GF can be used targeted only when in vivo regulation still cannot meet the need for repair.

Corneal endothelial cell sheet bioengineering from neural crest cell-derived adipose stem cells on novel thermo-responsive elastin-mimetic dendrimers decorated with RGD

Due to the limitations in in vivo division of Human Corneal Endothelial Cells (HCECs), and a shortage of cornea donations, there is increasing focus on bioengineering Corneal endothelium (CE) using alternative cells. Cell sheet engineering allows for the maintenance of the cellular junctions necessary for CE function. The aim of this study was to generate CE-like cell sheets on innovative thermo-responsive biopolymer, using hADSC-derived CE-like cells.Thermo-responsive biopolymers were fabricated by conjugating Elastin-like polypeptide (ELP) functionalized with RGD to a G4 dendrimer as a nanoplatform, named elastin-mimetic dendrimer (EMD). The hADSCs were first reprogrammed into neurospheres on Poly-L-lysine, induced by small molecules. Then, neural crest cells (NCCs) were differentiated into CE-like cells on EMD, and cultured until the CE-like cell sheet formed.EMD exhibited excellent biocompatibility improving cell spreading, adhesion, proliferation and NCCs differentiation into CE-like cells, and Lower critical solution temperature (LCST) near physiological temperature ideal for CE-like cell sheet harvesting. NCCs and CE-like cells markers were confirmed by qRT-PCR, immunocytochemistry, and western blot. After 18 days, cell sheets with cellular junctions were harvested by decreasing the temperature. This study thus represents the successful generation of CE-like cell sheets from hADSC-derived CE-like cells on EMD.

A cilium-independent role for intraflagellar transport 88 in regulating angiogenesis

Endothelial cilia are microtubule-based hair-like protrusions in the lumen ofblood vessels that function as fluid mechanosensors to regulate vascular hemodynamics.However, the functions of endothelial cilia in vascular development remain controversial. In this study, depletion of several key proteins responsible for ciliogenesis allows us to identify a cilium-independent role for intraflagellartransport88 (IFT88) in mammalian angiogenesis. Disruption of primary cilia by heat shock does not affect the angiogenic process. However, depletion of IFT88 significantly inhibits angiogenesis both in vitro and in vivo. IFT88 mediates angiogenesis by regulating the migration, polarization, proliferation, and oriented division of vascular endothelial cells. Further mechanistic studies demonstrate that IFT88 interacts with γ-tubulin and microtubule plus-end tracking proteins and promotes microtubule stability. Our findings indicate that IFT88 regulates angiogenesis through its actions in microtubule-based cellular processes, independent of its role in ciliogenesis.

Orientation of the Mitotic Spindle in Blood Vessel Development.

Angiogenesis requires coordinated endothelial cell specification, proliferation, and collective migration. The orientation of endothelial cell division is tightly regulated during the earliest stages of blood vessel formation in response to morphogenetic cues and the controlled orientation of the mitotic spindle. Consequently, oriented cell division is a vital mechanism in vessel morphogenesis, and defective spindle orientation can perturb the spatial arrangement of daughter cells and consequently contribute to several diseases related to vascular development. Many factors affect endothelial cell proliferation and orientation and therefore blood vessel formation, with the relationship between improper spindle orientation in endothelial cells and various diseases extensively studied. Here we review the molecular mechanisms driving the orientation of endothelial cell division, particularly with respect to the mitotic spindle, and how these processes affect vascular development, disease pathogenesis, and their potential as novel targets.

The process of revascularization in the neonatal mouse retina following short-term blockade of vascular endothelial growth factor receptors.

Misdirected vascular growth frequently occurs in the neovascular diseases in the retina. However, the mechanisms are still not fully understood. In the present study, we created capillary-free zones in the central and peripheral retinas in neonatal mice by pharmacological blockade of vascular endothelial growth factor (VEGF) signaling. Using this model, we investigated the process and mechanisms of revascularization in the central and peripheral avascular areas. After the completion of a 2-day treatment with the VEGF receptor tyrosine kinase inhibitor KRN633 on postnatal day (P) 4 and P5, revascularization started on P8 in the central avascular area where capillaries had been dropped out. The expression levels of VEGF were higher in the peripheral than in the central avascular area. However, the expansion of the vasculature in the peripheral avascular retina remained suppressed until revascularization had been completed in the central avascular area. Additionally, we found disorganized endothelial cell division, misdirected blood vessels with irregular diameters, and abnormal fibronectin networks at the border of the vascular front and the avascular retina. In the central avascular area, a slight amount of fibronectin as non-vascular component re-formed to provide a scaffold for revascularization. Mechanistic analysis revealed that higher levels of VEGF attenuated the migratory response of endothelial cells without decreasing the proliferative activity. These results suggest that the presence of concentration range of VEGF, which enhances both migration and proliferation of the endothelial cells, and the structurally normal fibronectin network contribute to determine the proper direction of angiogenesis.

PTEN Inhibition Accelerates Corneal Endothelial Wound Healing through Increased Endothelial Cell Division and Migration.

PurposeTo investigate the role of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in the regulation of corneal endothelial cell (CECs) focusing on proliferation and migration, and to further evaluate the application of PTEN inhibitors in the treatment of corneal endothelial dysfunction in a rat model.MethodsExpression of PTEN in human and rat corneal endothelium was determined by immunocytochemistry, western blotting, and ELISA. A small molecular inhibitor of PTEN, bpV(pic), was applied in the culture of human CEC cell line B4G12 and organ-cultured rat cornea in the presence of transforming growth factor beta 2 (TGF-β2). Cell cycle status was detected by flow cytometry and BrdU staining. Subcellular localization for endogenous p27Kip1 was detected by immunocytochemistry and western blotting. Moreover, exogenous transfected YFP-p27Kip1 was observed under a fluorescent microscope. Cell migration was examined with a wound scratch model and transwell invasion assay. Finally, bpV(pic) was intracamerally injected in a rat corneal endothelial injury model. The wound healing process was evaluated by slit lamp biomicroscopy, optical coherence tomography, histological and scanning electron microscope examination.ResultsThe expression of PTEN in human corneal endothelium was higher compared with rat, which we speculate was mostly responsible for the relatively less proliferation capacity of human CEC than rat. PTEN inhibition by bpV(pic) could reverse TGF-β2-induced CEC G1-arrest by alleviating p27Kip1 nuclear accumulation and decreasing total p27Kip1 expression. In addition, bpV(pic) promoted CEC migration, which acted synergistically with TGF-β2. Finally, intracameral injection of bpV(pic) could promote corneal endothelial wound healing in a rat model.ConclusionsOur study provided experimental basis for the development of therapeutic agent targeting on PTEN for the treatment of corneal endothelial dysfunction.

Nongenomic Actions of Thyroid Hormone: The Integrin Component.

The extracellular domain of plasma membrane integrin αvβ3 contains a cell surface receptor for thyroid hormone analogues. The receptor is largely expressed and activated in tumor cells and rapidly dividing endothelial cells. The principal ligand for this receptor is l-thyroxine (T4), usually regarded only as a prohormone for 3,5,3'-triiodo-l-thyronine (T3), the hormone analogue that expresses thyroid hormone in the cell nucleus via nuclear receptors that are unrelated structurally to integrin αvβ3. At the integrin receptor for thyroid hormone, T4 regulates cancer and endothelial cell division, tumor cell defense pathways (such as anti-apoptosis), and angiogenesis and supports metastasis, radioresistance, and chemoresistance. The molecular mechanisms involve signal transduction via mitogen-activated protein kinase and phosphatidylinositol 3-kinase, differential expression of multiple genes related to the listed cell processes, and regulation of activities of other cell surface proteins, such as vascular growth factor receptors. Tetraiodothyroacetic acid (tetrac) is derived from T4 and competes with binding of T4 to the integrin. In the absence of T4, tetrac and chemically modified tetrac also have anticancer effects that culminate in altered gene transcription. Tumor xenografts are arrested by unmodified and chemically modified tetrac. The receptor requires further characterization in terms of contributions to nonmalignant cells, such as platelets and phagocytes. The integrin αvβ3 receptor for thyroid hormone offers a large panel of cellular actions that are relevant to cancer biology and that may be regulated by tetrac derivatives.

MiR-412-5p targets Xpo1 to regulate angiogenesis in hemorrhoid tissue

Hemorrhoid is a common and recurrent proctological disease, which is often accompanied by angiogenesis and edema. MicroRNAs in the DLK1-DIO3 imprinted clusters are involved in the development and pathogenesis of mammalian hemorrhoids. Results of the present study indicated multiple, differential expression of DLK1-DIO3 imprinted cluster microRNA between hemorrhoid and normal tissues, where miR-412-5p expression in hemorrhoid tissue was significantly decreased. Fluorescein reporter assays showed that miR-412-5p silenced Xpo1 mRNA expression by targeting its 3′-UTR. Overexpression of miR-412-5p in human umbilical vein endothelial cells (HUVECs) indicated that proliferation, migration and formation of vascular structures in HUVECs were inhibited in vitro. In addition, overexpression of miR-412-5p significantly inhibited Xpo1 expression and promoted upregulation of the p53 protein and its retention in the nucleus. Simultaneously, expression of p66SHC and p16 proteins was activated. In summary, downregulation of endogenous miR-412-5p expression in hemorrhoid vascular endothelial cells leads to high expression of the target gene Xpo1 and translocation of the p53 protein out of the nucleus, rendering it unable to activate p66SHC and p16. This ultimately weakens regulation of the vascular endothelial cell cycle, thereby accelerating the division of hemorrhoid vascular endothelial cells, leading to angiogenesis.

Interpretation of Platelets in The Horse

Currently we can consider that, in addition to its role in hemostasis, platelets also participate in other important processes such as thrombosis, inflammation, tissue remodeling and the innate defense mechanisms. The hemostatic activity of platelets includes different events to stop bleeding. Within these functions we can mention the adhesion to the endothelium of the affected blood vessel, the activation, the aggregation, and the release of substances that initiate hemostatic events, and also the providing a phospholipid surface for activation of numerous coagulation factors. Similarly, platelets release multiple growth factors responsible for regulating the growth and division of endothelial cells and fibroblasts. In this way, among other things, angiogenesis and tissue regeneration are favored. Platelets also participate in inflammatory processes by the release of factors that initiate the inflammatory cascade and favor the chemotaxis of neutrophils, monocytes, macrophages, acute phase proteins and target cell signaling. Finally, platelets participate in the immune response by interacting with the complement system and immunoglobulins.

THE ROLE OF MYOKINES INTERSTITIAL INTERACTION AND REGULATION OF METABOLISM: A REVIEW OF LITERATURE

Myokines are hormone-like acting molecules produced in skeletal muscles during and immediately after exercise. They affect both paracrine (inside the muscles themselves) and endocrine manner (in adipose tissue, liver, endothelium, skin, mucosa etc.) implementing different effects on target tissues, mainly through regulation of metabolic processes (such as glucose and lipid metabolism, growth and division of neurons and endothelial cells and others). The examination of myokines is of great interest for researchers of different medicine departments, particularly for endocrinologists, because of myokines’ involvement in pathogenesis of abdominal and visceral obesity, diabetes mellitus type 2 and cardiovascular diseases that are all the components of metabolic syndrome. The most important issue for clinicians is a possibility of future therapeutic implication of the myokine’s signal pathways in treatment of widespread metabolic disorders.

Asymmetric division coordinates collective cell migration in angiogenesis.

The asymmetric division of stem or progenitor cells generates daughters with distinct fates and regulates cell diversity during tissue morphogenesis. However, roles for asymmetric division in other more dynamic morphogenetic processes, such as cell migration, have not previously been described. Here we combine zebrafish in vivo experimental and computational approaches to reveal that heterogeneity introduced by asymmetric division generates multicellular polarity that drives coordinated collective cell migration in angiogenesis. We find that asymmetric positioning of the mitotic spindle during endothelial tip cell division generates daughters of distinct size with discrete 'tip' or 'stalk' thresholds of pro-migratory Vegfr signalling. Consequently, post-mitotic Vegfr asymmetry drives Dll4/Notch-independent self-organization of daughters into leading tip or trailing stalk cells, and disruption of asymmetry randomizes daughter tip/stalk selection. Thus, asymmetric division seamlessly integrates cell proliferation with collective migration, and, as such, may facilitate growth of other collectively migrating tissues during development, regeneration and cancer invasion.

Clonal Proliferation and Stochastic Pruning Orchestrate Lymph Node Vasculature Remodeling

Lymph node (LN) expansion during an immune response relies on the transient remodeling of its vasculature. Although the mechanisms driving LN endothelial cell division are beginning to be understood, a comprehensive view of LN endothelial cell dynamics at the single-cell level is lacking. Here, we used multicolored fluorescent fate-mapping models to track the behavior of blood endothelial cells during LN expansion upon inflammation and subsequent return to homeostasis. We found that expansion of the LN vasculature relied on the sequential assembly of endothelial cell proliferative units. This segmented growth was sustained by the clonal proliferation of high endothelial venule (HEV) cells, which act as local progenitors to create capillaries and HEV neo-vessels at the periphery of the LN. Return to homeostasis was accompanied by the stochastic death of pre-existing and neo-synthesized LN endothelial cells. Thus, ourfate-mapping studies unravel-at a single-cell level-the complex dynamics of vascular-tree remodeling during LN expansion and contraction.

Deficiency in matrix metalloproteinase-2 results in long-term vascular instability and regression in the injured mouse spinal cord

Angiogenesis plays a critical role in wound healing after spinal cord injury. Therefore, understanding the events that regulate angiogenesis has considerable relevance from a therapeutic standpoint. We evaluated the contribution of matrix metalloproteinase (MMP)-2 to angiogenesis and vascular stability in spinal cord injured MMP-2 knockout and wildtype (WT) littermates. While MMP-2 deficiency resulted in reduced endothelial cell division within the lesioned epicenter, there were no genotypic differences in vascularity (vascular density, vascular area, and endothelial cell number) over the first two weeks post-injury. However, by 21days post-injury MMP-2 deficiency resulted in a sharp decline in vascularity, indicative of vascular regression. Complementary in vitro studies of brain capillary endothelial cells confirmed MMP-2 dependent proliferation and tube formation. As deficiency in MMP-2 led to prolonged MMP-9 expression in the injured spinal cord, we examined both short-term and long-term exposure to MMP-9 in vitro. While MMP-9 supported endothelial tube formation and proliferation, prolonged exposure resulted in loss of tubes, findings consistent with vascular regression. Vascular instability is frequently associated with pericyte dissociation and precedes vascular regression. Quantification of PDGFrβ+ pericyte coverage of mature vessels within the glial scar (the reactive gliosis zone), a known source of MMP-9, revealed reduced coverage in MMP-2 deficient animals. These findings suggest that acting in the absence of MMP-2, MMP-9 transiently supports angiogenesis during the early phase of wound healing while its prolonged expression leads to vascular instability and regression. These findings should be considered while developing therapeutic interventions that block MMPs.

Quantifying the Effects of Cell Division on Mass Redistribution Dynamics in Multicellular Clusters using Live Cell Interferometry

Cell division is a biomechanical process that both drives and responds to mechanical perturbations. For example, cell division in a confluent monolayer can induce long-range changes in surrounding cells, and the rate of endothelial cell division rate can be modulated by shear forces imposed by external flow. Conventional optical microscopy methods for measuring cell migration during and in response to cell division quantify these events in terms of length and time, or in terms of rate (change in length over time), using phase contrast or fluorescence microscopy. However, a complete mechanical profile of all biophysical parameters also requires measurement of mass, the third fundamental physical property relevant to intracellular biophysics behind length and time, excluding charge and spin which are not applicable to measurements of cell migration. Live cell interferometry (LCI) uses quantitative phase microscopy to measure cell mass, mass accumulation rate, and mass distribution within single cells or multicellular clusters. In previous work we used LCI to quantify the rate of cell migration within colonies, mass redistribution in daughter cells during mitosis, and the spatial coordination of mass motion in multicellular clusters. Here, we employ temporal autocorrelation, which measures the homogeneity of a time-dependent quantity, to measure the rate of change in colony and cell mass distributions over time. Our data show the dynamic nature of mass redistribution throughout the cell cycle and the dependence of this motion on cell division. Combined with measurements of the mass and distribution of mass within single cells or multicellular clusters, LCI therefore enables quantification of the change in energy dissipation rate due to cell division, and also provides a platform for future studies of the mechanics of cell-cell interactions.

Endothelial cell division in angiogenic sprouts of differing cellular architecture.

ABSTRACTThe vasculature of the zebrafish trunk is composed of tubes with different cellular architectures. Unicellular tubes form their lumen through membrane invagination and transcellular cell hollowing, whereas multicellular vessels become lumenized through a chord hollowing process. Endothelial cell proliferation is essential for the subsequent growth and maturation of the blood vessels. However, how cell division, lumen formation and cell rearrangement are coordinated during angiogenic sprouting has so far not been investigated at detailed cellular level. Reasoning that different tubular architectures may impose discrete mechanistic constraints on endothelial cell division, we analyzed and compared the sequential steps of cell division, namely mitotic rounding, cytokinesis, actin re-distribution and adherence junction formation, in different blood vessels. In particular, we characterized the interplay between cell rearrangement, mitosis and lumen dynamics within unicellular and multicellular tubes. The lumen of unicellular tubes becomes constricted and is ultimately displaced from the plane of cell division, where a de novo junction forms through the recruitment of junctional proteins at the site of abscission. By contrast, the new junctions separating the daughter cells within multicellular tubes form through the alteration of pre-existing junctions, and the lumen is retained throughout mitosis. We also describe variations in the progression of cytokinesis: while membrane furrowing between daughter cells is symmetric in unicellular tubes, we found that it is asymmetric in those multicellular tubes that contained a taut intercellular junction close to the plane of division. Our findings illustrate that during the course of normal development, the cell division machinery can accommodate multiple tube architectures, thereby avoiding disruptions to the vascular network.