Immunology

Platelets suppress T cell immunity against cancer

Blood platelets help disguise cancer from the immune system by suppressing T cells, report scientists at the Medical University of South Carolina (MUSC) in the May 5, 2017 issue of Science Immunology. In extensive preclinical ...

Medical research

Surprising new role for lungs—making blood

Using video microscopy in the living mouse lung, UC San Francisco scientists have revealed that the lungs play a previously unrecognized role in blood production. As reported online March 22, 2017 in Nature, the researchers ...

Cardiology

Antioxidant reduces risk for second heart attack, stroke

Doctors have long known that in the months after a heart attack or stroke, patients are more likely to have another attack or stroke. Now, a paper in the Journal of the American College of Cardiology explains what happens ...

Medical research

New methods reveal the biomechanics of blood clotting

Platelets are cells in the blood whose job is to stop bleeding by sticking together to form clots and plug up a wound. Now, for the first time, scientists have measured and mapped the key molecular forces on platelets that ...

Medical research

Single drug, soft environment can increase platelet production

(Medical Xpress) -- Humans produce billions of clot-forming platelets every day, but there are times when there aren’t enough of them, such as with certain diseases or during invasive surgery. Now, University of Pennsylvania ...

Medical research

Blood holds key to liver regeneration

The liver is the only organ in the body that can regenerate. But some patients who undergo a liver resection, a surgery that removes a diseased portion of the organ, end up needing a transplant because the renewal process ...

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Platelet

Platelets, or thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are small, irregularly shaped clear cell fragments (i.e. cells that do not have a nucleus containing DNA), 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes.  The average lifespan of a platelet is normally just 5 to 9 days. Platelets are a natural source of growth factors. They circulate in the blood of mammals and are involved in hemostasis, leading to the formation of blood clots.

If the number of platelets is too low, excessive bleeding can occur. However, if the number of platelets is too high, blood clots can form (thrombosis), which may obstruct blood vessels and result in such events as a stroke, myocardial infarction, pulmonary embolism or the blockage of blood vessels to other parts of the body, such as the extremities of the arms or legs.  An abnormality or disease of the platelets is called a thrombocytopathy, which could be either a low number of platelets (thrombocytopenia), a decrease in function of platelets (thrombasthenia), or an increase in the number of platelets (thrombocytosis). There are disorders that reduce the number of platelets, such as heparin-induced thrombocytopenia (HIT) or thrombotic thrombocytopenic purpura (TTP) that typically cause thromboses, or clots, instead of bleeding.

Platelets release a multitude of growth factors including Platelet-derived growth factor (PDGF), a potent chemotactic agent, and TGF beta, which stimulates the deposition of extracellular matrix.  Both of these growth factors have been shown to play a significant role in the repair and regeneration of connective tissues.  Other healing-associated growth factors produced by platelets include basic fibroblast growth factor, insulin-like growth factor 1, platelet-derived epidermal growth factor, and vascular endothelial growth factor.  Local application of these factors in increased concentrations through Platelet-rich plasma (PRP) has been used as an adjunct to wound healing for several decades.

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