Name: how new blood vessels grow
Uploaded: 2023-04-30T10:36:51.000Z
Duration: 1 min 10 s
Channel: JoVE

In angiogenesis, new blood vessels are formed from pre-existing ones during growth or in response to a stimulus, such as an injury or inflammation.
Following a stimulus, angiogenesis initiating proteins, such as vascular endothelial growth factors or VEGFs, are released.
VEGF activates surrounding endothelial cells to differentiate into specialized tip cells and release matrix metalloproteases that degrade their basement membrane.
These tip cells signal neighboring endothelial cells to differentiate into stalk cells.
As tip cells migrate along the VEGF concentration gradient, capillaries sprout from the walls of the existing vessel.
At the same time, stalk cells behind the endothelial tip multiply to form the body of the new vessel while their intracellular vacuoles merge into a continuous lumen.
The tip cells finally connect the newly formed vessels with the pre-existing ones to create a closed functional network of blood vessels.

mechanism of angiogenesis

Mechanism of Angiogenesis

Blood vessel formation starts early during embryonic development, around day 7. In the extraembryonic yolk sac, mesodermal precursor cells called hemangioblast proliferate and differentiate into angioblast. Angioblasts express vascular endothelial growth factor receptor 2 or VEGFR2, which binds VEGF-A, a proangiogenic factor, guiding blood vessel formation. VEGF signaling promotes angioblasts to form a blood island in the developing embryo. Angioblasts further differentiate, giving rise to endothelial cells, which aggregate and form the primitive vascular network called the vascular plexus.
&#160;&#160;&#160; Following vasculogenesis, the vascular plexus or the preexisting blood vessels guide new blood vessel formation through angiogenesis. Angiogenesis occurs by two distinct mechanisms: sprouting angiogenesis and intussusceptive angiogenesis.
<ol>
	<li>Sprouting angiogenesis:</li>
</ol>
In sprouting angiogenesis, angiogenic stimuli such as injury or growth spurt induce VEGF secretion from surrounding endothelial cells. VEGF binds VEGFR on these cells and signals them to produce matrix metalloproteases, which helps in basement membrane degradation following the detachment of pericytes from the vessel wall. VEGF and other angiogenic signals also stimulate endothelial cells to differentiate into tip and stalk cells. The tip cells extend filopodial structures resembling blind end tubes called sprouts. Tip cells migrate towards the angiogenic stimulus following the VEGF gradient. The stalk cells behind the angiogenic tip proliferate, elongating the tubular structure. Next, the newly formed blood vessel develops a lumen by one of the two processes: cell hollowing and cord hollowing. In the cell hollowing method, intracellular vacuoles fuse and connect adjacent cells, forming a continuous lumen. In the cord hollowing method, endothelial cells forming the tube change their shape to develop a central tubular lumen towards their extracellular side.
<ol>
	<li value="2">&#160;Intussusceptive angiogenesis:</li>
</ol>
Intussusceptive angiogenesis involves splitting a vessel into two, also called splitting angiogenesis. It is a faster way of new blood vessel formation. The newly formed vessels join the existing vessels and complete the vascular network. Pericytes and smooth muscles surround the newly formed vessel stabilizing them as blood flows through them.

Blood vessel formation starts early during embryonic development, around day 7. In the extraembryonic yolk sac, mesodermal precursor cells called ...

Education

JoVE Core

Cell Biology

Unit 1

A Hierarchical Stem-Cell System: Blood Cell Formation

a-hierarchical-stem-cell-system-blood-cell-formation

KEY TERMS AND CONCEPTS

how new blood vessels grow

How new blood vessels grow through angiogenesis is a key part of early development and tissue repair. Blood vessel formation begins around day 7 of embryonic development. In the extraembryonic yolk sac, mesodermal precursor cells called hemangioblasts multiply and become angioblasts.

Angioblasts express vascular endothelial growth factor receptor 2, or VEGFR2. This receptor binds VEGF-A, a proangiogenic factor that helps guide vessel formation. VEGF signaling pushes angioblasts to form a blood island in the developing embryo. The angioblasts then become endothelial cells, which gather to make the primitive vascular network called the vascular plexus.

After vasculogenesis, new vessels can form from the vascular plexus or from preexisting blood vessels through angiogenesis. The two main forms are sprouting angiogenesis and intussusceptive angiogenesis. Sprouting angiogenesis often begins after injury or during a growth spurt when angiogenic signals trigger VEGF release from nearby endothelial cells.

In sprouting angiogenesis, VEGF binds VEGFR on endothelial cells and causes them to make matrix metalloproteases. These enzymes help break down the basement membrane after pericytes detach from the vessel wall. VEGF and other signals also drive endothelial cells to become tip cells and stalk cells. Tip cells extend filopodia, which are thin finger-like projections, and form sprouts. They move toward the angiogenic signal along the VEGF gradient, while stalk cells behind them divide and lengthen the tube.

The new vessel then forms a lumen, or inner space, by cell hollowing or cord hollowing. In cell hollowing, intracellular vacuoles fuse and join neighboring cells to make one continuous lumen. In cord hollowing, the endothelial cells change shape to create a central tube on the extracellular side.

Intussusceptive angiogenesis forms new vessels in a different way. It splits one vessel into two, so it is also called splitting angiogenesis. This method is faster than sprouting angiogenesis. The new vessels then connect with existing vessels and complete the vascular network. Pericytes and smooth muscle surround the new vessel and help stabilize it as blood flows through.

How New Blood Vessels Grow

overview of the vascular system

Blood and Lymphatic Vessel Layers

The vascular system includes blood vessels and lymphatic vessels. It forms a large network of arteries, capillaries, and veins. In the body, this system is divided into the blood system and the lymphatic system. Blood vessels have three main histological layers. These layers are the tunica intima, tunica media, and tunica adventitia. The tunica intima is the inner layer. It has a single layer of endothelial cells attached to the basal lamina. Beneath that is a connective tissue layer and an...

How new blood vessels grow through angiogenesis is a key part of early development and tissue repair. Blood vessel formation begins around day 7 of embryonic development. In the extraembryonic yolk sac, mesodermal precursor cells called hemangioblasts multiply and become angioblasts. Angioblasts express vascular endothelial growth factor receptor 2, or VEGFR2. This receptor binds VEGF-A, a proangiogenic factor that helps guide vessel formation. VEGF signaling pushes angioblasts to form a blood...

regulation of angiogenesis and blood supply

regulation-of-angiogenesis-and-blood-supply

Hypoxia Triggers Angiogenesis Signaling

Hypoxia, or low oxygen, can trigger angiogenesis signaling in tissues that need more blood supply. Rapidly dividing tumors, embryos, and wounded tissues all use more oxygen than usual. As oxygen levels fall, cells switch on a pathway that helps form new blood vessels. A key oxygen sensor in this pathway is hypoxia-inducible factor 1, or HIF1. HIF1 has two parts, an alpha subunit and a beta subunit. Under normal oxygen conditions, HIF1 beta is in the nucleus, while HIF1 alpha stays in the...

hematopoiesis

Blood Cell Formation and Stem Cell Migration

Blood cell formation, or hematopoiesis, begins early in development. Around the seventh day of embryogenesis, the primitive wave starts in the extraembryonic yolk sac. In this early stage, a common precursor called a hemangioblast gives rise to erythroid cells and endothelial cells. The erythroid cells help carry oxygen and support the fast growth of the embryo. Hemangioblasts later develop into hematopoietic stem cells, or HSCs. These stem cells are multipotent, which means they can produce...

multipotency of hematopoietic stem cells

HSC Quiescence and Blood Cell Renewal

Hematopoietic stem cells (HSCs) help the body make blood and immune cells. These stem cells are multipotent, which means they can develop into many cell types in the blood system. They usually stay in a quiescent, or resting, state until an outside signal starts them moving toward differentiation. HSCs are grouped into two main populations: long-term repopulating cells (LTRCs) and short-term repopulating cells (STRCs). These groups differ in surface markers, or receptors on the cell surface,...

lineage commitment

Blood Stem Cell Fate Decisions

Blood stem cell fate decisions guide how hematopoietic stem cells become specific blood and immune cells. During commitment, stem cells lose the ability to form all cell types and change irreversibly into a more limited fate. Multipotent hematopoietic stem cells, or HSCs, first differentiate into multipotent hematopoietic progenitor cells, or HPCs. These HPCs express many lineage-specific cytokine receptors. Each receptor binds a specific cytokine, turns on a distinct signaling pathway, and...

erythropoiesis

How Red Blood Cells Are Replenished

Red blood cells, or RBCs, carry oxygen to body tissues and must be replaced after about 120 days. The body keeps this supply steady through erythropoiesis, the process of making new red blood cells. When oxygen levels drop after blood loss or injury, this process increases to restore oxygen delivery. Problems in erythropoiesis can lead to anemia, thalassemia, or polycythemia. Erythropoietin, also called Epo, starts this process. Before birth, the fetal liver makes Epo. After birth,...

differentiation of common myeloid progenitor cells

differentiation-of-common-myeloid-progenitor-cells

CSF Signals That Guide Myeloid Cells

Common myeloid progenitors are blood-forming cells in the bone marrow that can become granulocytes or macrophages. These immune cells protect the body against bacterial, viral, and fungal infections. They leave the bone marrow, travel in the blood, and move into tissues where they help with immune surveillance. These cells do not last long. They survive for only a few days, so the body must keep making them to maintain a strong immune system. During injury or infection, many immune cells are...

regulation of hematopoietic stem cells

How HSC Signals Control Blood Cell Supply

Hematopoietic stem cells, or HSCs, make blood and immune cells through hematopoiesis. These cells are replaced often because many have short life spans. They are also used up during immune surveillance, injury, or infection. This makes blood one of the most regenerative tissues in the body. Hematopoiesis must stay tightly controlled. If too many blood or immune cells are made, the cells can become cancerous or trigger autoimmune responses. Regulation helps HSCs stay quiescent, which means...

key terms and concepts

Learn how angiogenesis builds new blood vessels through sprouting and splitting, from VEGF signaling and tip cells to lumen formation and vessel stabilization.

How New Blood Vessels Grow | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

How New Blood Vessels Grow

Description

Transcript

Tags