Artificial Red Blood Cells and Platelets from Stem Cells!

By |January 11th, 2011

There’s hematology news today, x 2 (at least):

flexible hydrogel particles resembling RBCs in size and shape (Credit: Timothy Merkel and Joseph DeSimone, University of North Carolina at Chapel Hill)

1. Progress in developing synthetic red blood cells -

A University of North Carolina, Chapel Hill-based research group has created hydrogel particles that mimic the size, shape and flexibility of red blood cells (RBCs). The researchers used PRINT® (Particle Replication in Non-wetting Templates) technology to generate the fake RBCs, which are said to have a relatively long half-life. The findings were reported on-line yesterday in PNAS (abstract available, subscription required for full text). According to a PR-ish but interesting post on Futurity, a website put forth by a consortium of major research universities, tests of the particles’ ability to perform functions such as transporting oxygen or carrying therapeutic drugs have not yet been conducted.

Developing competent, artificial RBCs is a hematologist’s holy grail of sorts, because with that you might alleviate anemia without the risks of transfusion.

2. Progress in using human stem cells to generate lots of platelets -

In an exciting paper published today in Cell Research, investigators stimulated human embryonic stem cells to become platelet-producing cells, called megakaryocytes. According to the article (open-text at Nature PG), the platelets were produced in abundance, appeared typical and clotted appropriately in response to stimuli in vitro. The researchers injected them into mice, used high-speed video microscopy for imaging, and demonstrated that the stem cell-derived human platelets contributed to clot formation in mice, in vivo (i.e., they seem to work).

The research team includes scientists at Harvard Medical School, the University of Illinois and Cha University in Seoul. Several authors are affiliated with either or both of two biotech companies: Stem Cell and Regenerative Medicine International (address in Marlborough, MA) and Advanced Cell Technology (headquarters in Santa Monica, CA; lab in Marlborough, MA).

Platelets are tiny blood cells essential in wound repair and clotting upon injury. For some patients with bone marrow disorders, such as leukemia, or chemotherapy-induced thrombocytopenia (low platelets) with bleeding, there’s a significant transfusion demand for this blood component. If safe, functional human platelets could be manufactured from self-replicating stem cells in a lab, that would significantly reduce the need for platelets in the blood supply.

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Blood Matters

By |January 23rd, 2010

January, the coldest season in my vicinity, turns out to be National Blood Donor Month. This designation, a legacy of the Nixon administration (see Proclamation 3952 of December 31, 1969), I learned last week.

Besides, blood’s hot.

HBO’s True Blood received an invigorating, early renewal notice last summer; a third season will come out in June. And on film 2009 witnessed a quick, hungry revisit from Twilight, among others vampire flicks. Just this month, Ethan Hawke revealed himself in Daybreakers as Hollywood’s first hematologist-protagonist.

So it seems that now’s the perfect time to talk about it -

Blood, always my favorite Aristotelian humor, comprises two elements – plasma (a hazy yellowish fluid) and cells. The plasma bathes the blood cells in a mixture of salts and proteins as they travel within the walls of blood vessels throughout the body (the circulation) and in the chambers of the heart. Plasma proteins include some hormones, enzymes, clotting factors and antibodies.

Let’s start with some basics on the cellular components of blood: white blood cells, red blood cells and platelets:

neutrophil as seen in a peripheral blood smear, Wikimedia Commons (WC)

White Blood Cells

White blood cells (WBCs), physically larger than the rest, serve as warriors against infection. These include a cast of various types, each with a distinct role in battling germs. The most familiar white cells in the “peripheral blood” – as doctors refer to fluid passing through arteries and veins – are neutrophils, lymphocytes and monocytes. Two other forms, eosinophils and basophils, emerge from the bone marrow and typically travel in lesser numbers.

scanning micrograph, red blood cells, WC, adapted NIH image

Red Blood Cells

Red blood cells (RBCs), the most abundant and usually uniform blood cells, carry and deliver oxygen throughout the body. Mature, circulating red cells are disc-like in shape, indented on each side, and lack nuclei. They’re loaded with hemoglobin, a complex, iron-laden molecule that binds oxygen and turns blood red.

When someone receives a transfusion, that’s usually a unit of packed red blood cells, concentrated red cells from which most of the donor’s white cells, platelets and plasma have been removed.

Platelets

Platelets are tiny, blood clotting cells. Like red cells, these cells circulate without nuclei, but they’re irregular in shape and sticky, loaded inside with plug-forming proteins and on their surfaces with adhesive receptors, ready to clump at the nick of a chin or a pinprick.

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Both cancer and its treatments can affect the bone marrow, where blood cells are formed. Some tumors, like leukemia and lymphoma, arise from blood cells. Other medical conditions cause blood cell problems, too. For example, chronic kidney disease causes anemia, and HIV infection leads to reduced T-lymphocyte counts.

For all these reasons, I think it’s helpful for everyone to have some understanding of blood and blood cells – any discussion of stem cells, bone marrow and transplantation presupposes some knowledge of these basics.

More to follow!

Meanwhile, if you’re searching for more blood info on the Web, I suggest these sites:

American Society of Hematology – Blood: the Vital Connection

America’s Blood Centers – What is Blood?

American Society of Clinical Oncology (Cancer.Net) – Understanding Blood Test Results

MedlinePlus – Blood and Blood Disorders

National Heart Lung and Blood Institute – Blood Diseases and Resources Information

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