• Recent research has shown that blood platelets are involved in a lot more functions than we thought, according to our partner The Conversation.

  • The body has a trillion circulating platelets that last as little as a week.

    Our bone marrow therefore produces a billion per day.

  • The analysis of this phenomenon was carried out by Patricia Martínez Botía, undergraduate researcher in biomedicine.

Scarring is one of those abilities that are so essential and ubiquitous that we don't even notice it anymore.

At the slightest cut or scrape, at the slightest wound, the blood platelets activate when it heals and, stopping the bleeding there like physiological dressings, prevent us from emptying our blood.

In scientific terms, we speak of "maintenance of hemostasis".

This system has only one drawback: when it works too well, it can work against us and generate thrombi, a kind of moving clot that can lead to heart attacks and strokes.

Despite such an important function, platelets have long been relegated to oblivion.

Little in the midst of the swarm of blood

Blood is, however, one of the most studied (liquid) tissues.

From red blood cells and their well-known function of transporting oxygen to all our tissues and organs, to white blood cells, which constitute the various lines of defense of our system, including plasma and its cohort of proteins, of lipids, nutrients and minerals.

Red blood cell, platelet and white blood cell (by MEB) © National Cancer Institute (via The Conversation)

With such a crowd, it is ultimately not so absurd that its smaller members have been neglected.

Especially since platelets are not only small, but they are not given the rank of cell, being devoid of nucleus and therefore of DNA.

In a way, they are in fact simple fragments of cells, "blood dust", as they were described when they first observed them.

But be careful because, far from being a disadvantage, the absence of a nucleus translates into more space to store all kinds of proteins, both inside and on their surface.

In addition, their small size gives them enough flexibility to be able to slip into the narrowest and most hidden recesses of our body.

A very versatile non-cell

We have over a trillion platelets in circulation, and with their lifespan of just a week, our bone marrow is responsible for producing them at the rate of a billion a day.

Only a few years ago, the scientific community began to wonder how it was possible that platelets, so numerous, were only dedicated to clotting.

The hypothesis that they could play additional roles gradually gained ground and researchers discovered them in situations, both physiological and pathological, with which they had never been associated.

So, while we thought we knew all about them, a myriad of articles showed that we had underestimated them.

That platelets actually had a whole secret life that had eluded us until then.

Immune Patrol Members

For starters, platelets play a major role in inflammation and the immune response.

Thanks to their tireless patrols in the blood, they are among the first to notice if foreign agents (viruses or bacteria, for example) are causing damage.

When this happens, they release a plethora of molecules that induce inflammation in the area and alert the various players in the immune system to the danger.

Ubiquitous, platelets (green) multiply roles © Dennis Kunkel Microscopy, Inc. / Zeiss Microscopy / Flickr (via The Conversation)

In addition, they participate very actively in their elimination, either in collaboration with white blood cells, or alone.

This role is also a double-edged sword, since they have been linked to the origin and course of certain autoimmune diseases, such as atherosclerosis or rheumatoid arthritis.

Their large molecular load is also multifunctional: the approximately 4,000 different proteins that they carry can be released or withdrawn from the bloodstream, according to the needs of the moment.

Perhaps the most popular are growth factors, which are involved in areas as diverse as embryonic development and regenerative medicine, in rebuilding damaged tissue after injury, and even neurologically.

The platelet cargo also includes serotonin, which is involved in promoting regeneration of the liver when it has been damaged or partially eliminated.

It is also the presence of serotonin in platelets, as well as other proteins (reelin, β-amyloid peptide) typically associated with neurons, which was used to establish the hypothesis of a link between the two, the first being the mirror of what happens in the second.

An invisibility cloak for cancer?

Finally, we cannot neglect the possible role of platelets in cancer, more precisely in metastases.

Tumor cells that travel through the blood in search of a new organ to colonize have an extremely low survival rate.

However, our platelets would be ready to lend a helping hand, sticking to them and surrounding them, like a kind of invisibility cloak, preventing the cells of the immune system from detecting and killing them.

Our "BLOOD" file

Not content with this, they would promote their transfer from the blood to a new organ.

In addition to creating a favorable environment for cancer cells after they set in, they may help the growth of new blood vessels (angiogenesis) that supply them with oxygen and nutrients.

In short, in the last few years, studying platelets has allowed us to discover that they are involved in a lot more functions than we thought, both in terms of health and disease.

This not only makes them very important players for research, but also potential targets and therapeutic factors, with the possibility of helping a large and diverse number of patients.

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This analysis was written by Patricia Martínez Botía, pre-doctoral researcher in biomedicine at the Institute for Health Research of the Principality of Asturias (ISPA) and at the University of Oviedo (Spain).


The original article was published on The Conversation website.

Declaration of interests

Patricia Martínez Botía does not work, advise, own shares, receive funds from any organization that could benefit from this article, and has not declared any affiliation other than her research organization.

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