Most of us have somewhere around a trillion tiny platelets zooming around our bloodstreams. Joseph Italiano, PhD, of Boston Children’s Hospital’s Vascular Biology Program, calls them the “Swiss Army knives of the blood.” In addition to their key role in clotting, platelets are important in immunity, wound healing, chemical delivery, blood vessel development and more.
At healthcare facilities, platelets are in constant demand for patients with blood diseases, or those receiving radiation or chemotherapy for cancer. But unlike other blood products, platelets can’t be stored for more than a few days. If there’s a snowstorm or other emergency preventing donors from giving platelets, a hospital can easily run out. So researchers have been trying to make platelets in a lab setting.
Two teams at Boston Children’s Hospital are tackling the problem in slightly different ways. …
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Looking down at my bandaged finger—a souvenir of a kitchen accident a few nights prior—Joseph Italiano, PhD, smiles and says to me, “You should have come by, we could’ve given you some platelets for that.”
The problem is that Italiano really couldn’t; he needs every platelet his lab can put its hands on. A platelet biologist in Boston Children’s Hospital’s Vascular Biology Program, Italiano is trying to find ways to manufacture platelets at a clinically useful scale.
To do that, he needs to develop a deep understanding of the science of how the body produces platelets, something that no one has at the moment.
The path by which blood stem cells develop into megakaryocytes—the bone marrow cells that produce and release platelets into the bloodstream—is already known, Italiano says. We also know that platelets are essentially fragments of megakaryocytes that break off in response to some signal.
But that’s where our knowledge of platelet production largely ends. “Megakaryocytes themselves are something of a black box,” Italiano explains. “If you microinject the cytoplasm of an active megakaryocyte into a resting megakaryocyte, it will start to produce platelets as well. But we don’t know what factor or factors cause them to start platelet production.”
As Italiano and his laboratory peer into that black box, they know the stakes are big. Because in the end, they want to greatly reduce doctors’ and patients’ dependence on donated platelets. …
Grab a garden hose. Put your thumb over the end, but not all the way, and turn the water on. What happens? The water coming out of the hose gets squeezed as it tries to push past your thumb, putting a lot of force on the molecules in the water and making a big spray.
Now do the same thing with an artery: Partially block it with a clot and let blood flow through it. In this case, the force you’ve created in the artery could be lethal—creating fertile ground for blood clots that could lead to a stroke or heart attack.
The platelet – a crucial cog in our blood’s clotting machinery – is in high demand. Trauma, chemotherapy, and surgery patients often need platelet transfusions to keep their blood working properly. So too do people with genetic disorders like Wiskott-Aldrich syndrome that prevent them from producing enough platelets on their own and cause thrombocytopenia.
However, platelets are in short supply compared to other blood products, in part due to their short shelf life.
“Platelets only last in the body for about 10 days at a time,” explains Jonathan Thon, a fellow in the laboratory of Joe Italiano, a member of Children’s Vascular Biology Program. “In a blood bank, red blood cells can be stored in a refrigerator for 42 days, and plasma can be frozen for years. But platelets need to be stored at room temperature, and only for a short time for fear of bacterial contamination.” Which means that few platelets are available for those who need them – a situation that screams for a means of artificial platelet production. …