Angiopellosis (cell

extravasation __NOTOC__ Extravasation is the leakage of a fluid out of its container into the surrounding area, especially blood or blood cells from vessels. In the case of inflammation, it refers to the movement of white blood cells from the capillaries to th ...

) is the movement of cells out of the

circulatory system The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...

into the surrounding tissue. This process is specific to non-leukocytic cells, as

leukocytes White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...

(white blood cells) utilize

diapedesis Leukocyte extravasation (also commonly known as leukocyte adhesion cascade or diapedesis – the passage of cells through the intact vessel wall) is the movement of leukocytes out of the circulatory system and towards the site of tissue damage or ...

for movement out of circulation. Angiopellosis was discovered by studying how

stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type o ...

s reach damaged tissue when injected or infused into the blood stream. Recently, it was found that

circulating tumor cells A circulating tumor cell (CTC) is a cell that has shed into the vasculature or lymphatics from a primary tumor and is carried around the body in the blood circulation. CTCs can extravasate and become ''seeds'' for the subsequent growth of additional ...

(CTCs) also possess the ability to exit blood vessels through angiopellosis during the

metastasis Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then, ...

process Angiopellosis involves recognition of cells by the blood vessel wall (

endothelial cells The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...

), and then the active remolding of the blood vessel to allow the cell to exit.

Mechanism

Angiopellosis extravasation occurs as a means for cells that are not native to the circulation to exit. This includes adult stem cells that are injected

intravenously Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...

for therapies. Cells that are normally found in circulation (i.e.

blood cell A blood cell, also called a hematopoietic cell, hemocyte, or hematocyte, is a cell produced through hematopoiesis and found mainly in the blood. Major types of blood cells include red blood cells (erythrocytes), white blood cells (leukocytes), ...

s) either extravasate through diapedesis (white blood cells), or do not extravasate and remain in circulation (

red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

s). Angiopellosis was discovered by a group of researchers at

North Carolina State University North Carolina State University (NC State) is a public land-grant research university in Raleigh, North Carolina. Founded in 1887 and part of the University of North Carolina system, it is the largest university in the Carolinas. The universit ...

who were studying the mechanism intravenously injected stem cells utilized to reach damaged tissue. They discovered that the injected stem cells prompted the blood vessel walls to undergo extensive change on the cellular level which results in the removal of the cell from the inside of the vessel ( lumen) into the surrounding area. Below is a brief summary of each of the steps currently thought to be involved in ''angiopellosis'': Upon entering the circulation, the cell(s) travel through the blood vessels and eventually attach or become lodged inside the blood vessel wall. This prompts the series of events that end in the cell(s) exiting circulation. The endothelial cells recognize the cell through membrane-specific recognition. Recognition of cell is important and is thought to be the reason cells native to the circulation to not randomly extravasate through angiopellosis. Once attached or lodged, the exiting cell(s) elicit activity from the endothelial cells of the blood vessel. The endothelial cells extend protrusions and actively remodel themselves around the exiting cells The exiting cell will then be either actively "pushed" from the inside of the blood vessel, or the vascular cells will remodel around the cell so that the cell no longer remains inside the vessel

Differences from Leukocyte Extravasation

The most notable difference is the physical mechanism the cells use to exit. During ''angiopellosis'', the endothelial cells are the most active in the process, while in diapedesis it is the white blood cell that are the most physically active during the process. During angiopellosis the extravasating cell remains round in morphology and only slightly changes shape as a result of the vasculature remodeling around it. However, during diapedesis the white blood cells significantly change shape as they migrate through the blood vessel. Angiopellosis allows for the extravasation of multiple cells during a single event. The blood vessel will actively remodel around a cluster/group of cells and allow the cells to exit in a single event. Diapedesis only allows for a single white blood cell to migrate across the blood vessel wall at a time. Although multiple white blood cells can leave simultaneously, they all elicit separate diapedesis extravasation events. There are also temporal and molecular difference between the two processes

Stem cell infusion therapy

Stem cell infusion therapy is a type of

infusion therapy In medicine, infusion therapy deals with all aspects of fluid and medication infusion, via intravenous or subcutaneous application. A special infusion pump can be used for this purpose. A fenestrated catheter is most frequently inserted into the lo ...

where stem cells are infused into the blood. These stem cells then exit the blood vessels and preferentially migrate to damages tissue for regeneration. ''Angiopellosis'' has been shown to be the method these infused stem cells utilize to extravasate and reach damaged tissue

References

{{reflist Cell movement

Mechanism

Differences from Leukocyte Extravasation

Stem cell infusion therapy

See also

References