Stories about: Regenerative medicine

Could a simple injection fix spina bifida before birth?

Mesenchymal stem cells derived from amniotic fluid (FAUZA LAB / BOSTON CHILDREN’S HOSPITAL)

Ed. note: This is an update of a post that originally appeared in 2014.

The neural tube is supposed to close during the first month of prenatal development, forming the spinal cord and the brain. In children with spina bifida, it doesn’t close completely, leaving the nerves of the spinal cord exposed and subject to damage. The most common and serious form of spina bifida, myelomeningocele, sets a child up for lifelong disability, causing complications such as hydrocephalus, leg paralysis, and loss of bladder and bowel control.

A growing body of research from Boston Children’s Hospital, though still in animal models, suggests that spina bifida could be repaired at least partially early in pregnancy, through intrauterine injections of a baby’s own cells.

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Can we teach heart cells to grow up?

normal and mutant cardiomyocytes
A mutant heart muscle cell (in green) surrounded by normal cells. The mutant cell lacks Srf, a master maturation gene. It is unable to grow in size and lacks the fine membrane invaginations that help coordinate muscle contractions (appearing as vertical striations in the normal cells). (IMAGE: GUO Y; ET AL. NAT COMMS 9 #3837 (2018).]

Scientists around the world have been trying to replace damaged heart tissue using lab-made heart-muscle cells, either injecting them into the heart or applying patches laced with the cells. But results to date have been underwhelming.

“If you make cardiomyocytes in a dish from pluripotent stem cells, they will engraft in the heart and form muscle,” says William Pu, MD, director of Basic and Translational Cardiovascular Research at Boston Children’s Hospital. “But the muscle doesn’t work very well because the myocytes are stuck in an immature stage.”

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Why blood stem cells are in our bones: Evolutionary observation may inform better bone marrow transplants

blood stem cells melanocytes hematopoietic stem cells
In normal zebrafish, blood stem cells in the kidney are protected from sunlight by melanocytes. When this layer is stripped away, stem cell numbers go down. (Image and video below courtesy of the Zon Laboratory and the Howard Hughes Medical Institute.)

Since the late 1970s, biologists have known that blood develops in a specific body location. But they’ve wondered why different creatures house their blood stem cells in different places. In humans and other mammals, they’re in the bone. In fish, they’re in the kidney. Why?

Strange as it seems, the two stem cell “niches” share something in common, say researchers led by Leonard Zon, MD, of Boston Children’s Stem Cell Program, the Harvard Department of Stem Cell and Regenerative Biology (HSCRB) and the Harvard Stem Cell Institute. Both protect blood stem cells from sunlight’s harmful ultraviolet rays. The findings, published today in Nature, may contain lessons for improving blood stem cell transplants for cancer, blood disorders and other conditions.

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Poised pluripotency: A glimpse of the early embryo just as it’s implanting

poised pluripotency - a newly defined stem cell state
Fawn Gracey illustration (click to enlarge)

Stem cell researchers at Boston Children’s Hospital have, for the first time, profiled a highly elusive kind of stem cell in the early embryo – a cell so fleeting that it makes its entrance and exit within a 12-hour span. They describe this “poised pluripotent” cell in the journal Cell Stem Cell.

In mice, poised cells appear 4.75 to 5.25 days after egg and sperm join to form the embryo, right at the time when the embryo stops floating around and implants itself in the uterine wall.

“People have had a hard time capturing the peri-implantation period because it’s really hard to define,” says Richard Gregory, PhD, who led the research. “It’s a very dynamic stage. Everything happens within a few hours, which is quite remarkable considering the extent of the changes occurring in the properties of the cells.”

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Intestine chip models gut function, in disease and in health

villus-like projections growing in gut chip
Villus-like extensions formed by small intestinal cells from patient biopsies, protruding into the Intestine Chip’s luminal channel. (Credit: Wyss Institute at Harvard University)

The small intestine is much more than a digestive organ. It’s a major home to our microbiome, it’s a key site where mucosal immunity develops and it provides a protective barrier against a variety of infections. Animal models don’t do justice to the human intestine in all its complexity.

Attempts to better model human intestinal function began with intestinal “organoids,” created from intestinal stem cells. The cells, from human biopsy samples, form hollowed balls or “mini-intestines” bearing all the cell types of the intestinal lining, or epithelium. Recently, intestinal organoids helped reveal how Clostridium difficile causes such devastating gastrointestinal infections.

But while organoids have all the right cells, they don’t fully replicate the environment of a real small intestine. Real intestines are awash in bacteria and nutrients, are fed by blood vessels and are stretched and compressed by peristalsis, the intestines’ cyclical muscular contractions that push nutrients forward.

Efforts to recreate that environment led to the Intestine Chip. An early version, created by the Wyss Institute for Biologically Inspired Engineering, cultured cells from a human intestinal tumor cell line.

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More surprises about blood development — and a possible lead for making lymphocytes

blood development chart
Blood development in the embryo begins with cells that make myeloid and erythroid cells – but not lymphoid cells. Why? A partial answer is in today’s Nature.

Hematopoietic stem cells (HSCs) have long been regarded as the granddaddy of all blood cells. After we’re born, these multipotent cells give rise to all our cell lineages: lymphoid, myeloid and erythroid cells. Hematologists have long focused on capturing HSCs’ emergence in the embryo, hoping to recreate the process in the lab to provide a source of therapeutic blood cells.

But in the embryo, oddly enough, blood development unfolds differently. The first blood cells to show up are already partly differentiated. These so-called “committed progenitors” give rise only to erythroid and myeloid cells — not lymphoid cells like the immune system’s B and T lymphocytes.

Researchers in the lab of George Q. Daley, MD, PhD, part of Boston Children’s Hospital’s Stem Cell Research program, wanted to know why. Does nature deliberately suppress blood cell multipotency in early embryonic development? And could this offer clues about how to reinstate multipotency and more readily generate different blood cell types?

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‘Pull’ from an implanted robot could help grow stunted organs

Surgeons at Boston Children’s Hospital have long sought a better solution for long-gap esophageal atresia, a rare birth defect in which part of the esophagus is missing. The current state-of-the art operation, called the Foker process, uses sutures anchored to children’s backs to gradually pull the unjoined ends of esophagus until they’re long enough to be stitched together. To keep the esophagus from tearing, children must be paralyzed in a medically induced coma, on mechanical ventilation, for one to four weeks. The lengthy ICU care means high costs, and the long period of immobilization can cause complications like bone fractures and blood clots.

Now, a Boston Children’s Hospital team has created an implantable robot that could lengthen the esophagus — and potentially other tubular organs like the intestine — while the child remains awake and mobile. As described today in Science Roboticsthe device is attached only to the tissue being lengthened, so wouldn’t impede a child’s movement.

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News Note: Cell ‘barcodes’ trace the natural development of blood

in situ blood development
(Credit: Stem Cell Program, Boston Children’s Hospital)

Genetic labels, or “barcodes,” are shedding new light on the natural process of blood development and immune-cell production, finds a study published in Nature this week. It was led by Fernando Camargo, PhD, and first author Alejo Rodriguez Fraticelli, PhD, at Boston Children’s Hospital’s Stem Cell Research Program, the Harvard Department of Stem Cell and Regenerative Biology and the Harvard Stem Cell Institute.

Most of what we know about blood production is through observing what happens when blood stem and progenitor cells are transplanted into an animal. To observe what happens “in the wild,” researchers went in and tagged the blood stem and progenitor cells of mice, using genetic elements called transposons. This allowed them to track how the cells differentiated into five kinds of blood cells (above: megakaryocytes, erythroid cells, granulocytes, monocytes and B-cell progenitors).

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Delivered through amniotic fluid, stem cells could treat a range of birth defects

Transamniotic stem cell therapy, or TRASCET, is like amniocentesis is reverse.
Amniotic fluid is routinely withdrawn for prenatal testing. It could also be a delivery route for fetal cell therapy to treat congenital anomalies, with broader applications than once thought.

The amniotic fluid surrounding babies in the womb contains fetal mesenchymal stem cells (MSCs) that can differentiate into many cell types and tissues. More than a decade ago, Dario Fauza, MD, PhD, a surgeon and researcher at Boston Children’s Hospital, proposed using these cells therapeutically. His lab has been exploring these cells’ healing properties ever since.

Replicated in great quantity in the lab and then reinfused into the amniotic fluid in animal models — a reverse amniocentesis if you will — MSCs derived from amniotic fluid have been shown to repair or mitigate congenital defects before birth. In spina bifida, they have induced skin to grow over the exposed spinal cord; in gastroschisis, they have reduced damage to the exposed bowel. Fauza calls this approach Trans-Amniotic Stem Cell Therapy, or TRASCET.

New research findings, reported this month in the Journal of Pediatric Surgery, could expand TRASCET’s therapeutic potential.

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3D organoids and RNA sequencing reveal the crosstalk driving lung cell formation

lung disease
A healthy lung must maintain two key cell populations: airway cells (left), and alveolar epithelial cells (right). (Joo-Hyeon Lee)

To stay healthy, our lungs have to maintain two key populations of cells: the alveolar epithelial cells, which make up the little sacs where gas exchange takes place, and bronchiolar epithelial cells (also known as airway cells) that are lined with smooth muscle.

“We asked, how does a stem cell know whether it wants to make an airway or an alveolar cell?” says Carla Kim, PhD, of the Stem Cell Research Program at Boston Children’s Hospital.

Figuring this out could help in developing new treatments for such lung disorders as asthma and emphysema, manipulating the natural system for treatment purposes.

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