Stories about: blood stem cells

Medical milestone: Making blood stem cells in the lab

blood stem cells
The gradation of pink-to-blue cells illustrates the transition from hemogenic endothelial cells to blood progenitor cells during normal embryonic blood development. Daley, Sugimura and colleagues recreated this process in the lab, then added genetic factors to produce a mix of blood stem and progenitor cells. (O’Reilly Science Art)

Pluripotent stem cells can make virtually every cell type in the body.  But until now, one type has remained elusive: blood stem cells, the source of our entire complement of blood cells.

Since human embryonic stem cells (ES cells) were isolated in 1998, scientists have tried to get them to make blood stem cells. In 2007, the first induced pluripotent stem (iPS) cells were made from human skin cells, and have since been used to generate multiple cell types, such as neurons and heart cells.

But no one has been able to make blood stem cells. A few have have been isolated, but they’re rare and can’t be made in enough numbers to be useful.

Now, the lab of George Daley, MD, PhD, part of Boston Children’s Stem Cell Research program as finally hit upon a way to create blood stem cells in quantity, reported today in Nature.

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Supercharged marrow transplant: Zebrafish reveal drugs that aid engraftment

Zebrafish stem cell engraftment bone marrow
(Jonathan Henninger and Vera Binder)

Bone marrow transplantation, a.k.a. stem cell transplantation, can offer a cure for certain cancers, blood disorders, immune deficiencies and even metabolic disorders. But it’s a highly toxic procedure, especially when a closely matched marrow donor can’t be found. Using stem cells from umbilical cord blood banked after childbirth could open up many more matching possibilities, making transplantation safer.

Except for one problem. “Ninety percent of cord blood units can’t be used because they’re too small,” says Leonard Zon, MD, who directs the Stem Cell Research Program at Boston Children’s.

But what if the blood stem cells in those units could be supercharged to engraft more efficiently in the bone marrow and grow their numbers faster? That’s been the quest of the Zon lab for the past seven years, in partnership with a see-through zebrafish called Casper.

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Live imaging captures how blood stem cells take root in the body

For years, the lab of Leonard Zon, MD, director of the Stem Cell Research Program at Boston Children’s Hospital, has sought ways to enhance bone marrow transplants for patients with cancer, serious immune deficiencies and blood disorders. Using zebrafish as a drug-screening platform, the lab has found a number of promising compounds, including one called ProHema that is now in clinical trials.

But truthfully, until now, Zon and his colleagues have largely been flying blind.

“Stem cell and bone marrow transplants are still very much a black box: cells are introduced into a patient and later on we can measure recovery of their blood system, but what happens in between can’t be seen,” says Owen Tamplin, PhD, in the Zon Lab. “Now we have a system where we can actually watch that middle step.”

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Seeding medical innovation: The Technology Development Fund

Monique Yoakim Turk Technology Development FundMonique Yoakim-Turk, PhD, is a partner of the Technology Development Fund and associate director of the Technology and Innovation Development Office at Boston Children’s Hospital

Since 2009, Boston Children’s Hospital has committed $6.2 million to support 58 hospital innovations ranging from therapeutics, diagnostics, medical devices and vaccines to regenerative medicine and healthcare IT projects. What a difference six years makes.

The Technology Development Fund (TDF) was proposed to Boston Children’s senior leadership in 2008 after months of research. As a catalyst fund, the TDF is designed to transform seed-stage academic technologies at the hospital into independently validated, later-stage, high-impact opportunities sought by licensees and investors. In addition to funds, investigators get access to mentors, product development experts and technical support through a network of contract research organizations and development partners. TDF also provides assistance with strategic planning, intellectual property protection, regulatory requirements and business models.

Seeking some “metrics of success” beyond licensing numbers and royalties (which can come a decade or so after a license), I asked recipients of past TDF awards to report back any successes that owed at least in part to data generated with TDF funds. While we expected some of the results, we would have never anticipated such a large impact.

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Can blood cells be rebooted into blood stem cells?

Hematopoietic hierarchy blood development stem cells
The classic hematopoietic hierarchy. What if we could turn those arrows around?

Think, for a moment, of a cell as a computer, with its genome as its software, working to give cells particular functions. One set of genetic programs turns a cell into a heart cell, another set creates a neuron, still another a lymphocyte and so on.

The job of controlling which programs get booted up, and when, falls in part to transcription factors—genes that act like molecular switches to turn other genes on and off.

Derrick Rossi, PhD, spends a lot of his time thinking about transcription factors. A stem cell and blood development researcher in Boston Children’s Hospital’s Program in Cellular and Molecular Medicine, Rossi believes that transcription factors hold the power to achieve one of the most sought-after goals in regenerative medicine: producing, from other cell types, transplantable hematopoietic stem cells (HSCs).

“There are about 50,000 HSC transplants every year,” Rossi explains, noting that the success of a transplant is highly dependent on the number of cells a patient receives from her donor. “But HSCs only comprise about one in every 20,000 cells in the bone marrow.

“If we could generate autologous HSCs from a patient’s other cells,” he continues, “it could be transformative for transplant medicine and for our ability to model diseases of blood development.”

As they reported April 24 in Cell, Rossi and his collaborators have taken a significant step toward that goal: Using a cocktail of eight transcription factors, they reprogrammed mature mouse blood cells into what they have dubbed induced HSCs (iHSCs).

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