Stem cells make new heart valves

Researchers have coaxed adult stem cells into forming artificial heart valves that could one day mean fewer surgeries for children suffering from heart defects.

The scientists, at Harvard-affiliated Boston Children’s Hospital, grew the valves from a type of stem cell that normally gives rise to the inner lining of blood vessels. They used a biodegradable scaffold to give the cells shape and a mix of proteins and growth factors to stimulate the cells to grow into the proper tissue type.

Instructor in Medicine Virna Sales, a researcher in Boston Children’s Department of Cardiac Surgery, said the work, which used the tissue of laboratory animals, builds on research conducted over the past decade by Professor of Surgery John Mayer.

Mayer, also in Boston Children’s Department of Cardiac Surgery, was the senior investigator of the study. His research over the past 10 years has focused on helping the 25,000 to 30,000 children born each year with heart defects.

Today, Sales said, the defects are corrected using prosthetics made from artificial materials and tissue from pigs. The problem with those materials, she said, is that they don’t grow. Depending on the defect type and the age of the child at the time of surgery, the child may (and often does) need additional surgeries as his or her heart gets larger.

Researchers hope to be able to screen the blood-vessel stem cells, called endothelial progenitor cells, from a child’s blood and use them to make valves out of a child’s own tissue. Since the valves would be made from living tissue, they would grow, sparing the child additional surgery.

The research, published in the journal Circulation, is still five to 10 years away from being used in humans, Sales said.

The body has two major types of stem cells. Embryonic stem cells are present at the very early stages of life and have the ability to change into any type of cell in the body. More limited are adult stem cells, which give rise to different cells within a particular tissue type. Blood stem cells, for example, are found in the bone marrow and are constantly growing and differentiating, replacing cells in the bloodstream as they are needed.

Prior research has sought both the right cells to start with and the proper mix of proteins and growth factors to coax the cells to differentiate into the right kind of tissue.

The body uses these growth factors and proteins to signal stem cells to divide, grow, and change into the type of tissue needed.

Though the natural process may seem straightforward, the mix of factors, including dosage, and timing, are delicately balanced in nature and provide researchers a significant challenge to reproduce.

As researchers learn to fine-tune the process, Sales said, they can use multiple coatings on the scaffold to expose the tissues to different factors at different times. That way, she said, it may be possible to “customize” one’s heart valve.

Now that they’ve successfully grown the valves from animal tissue, researchers are working to refine the technology. They’re testing the mechanical properties of the engineered valves in a bioreactor, a device designed to mimic the never-ending motion of the heart. They’re also experimenting with a different mix of the growth factors and proteins to see if they can get the valves to grow more naturally, without the supporting scaffold.

“I’m going back to the basics,” Sales said, “[We’re] going to mimic mother nature.”

Source: Harvard University

Related stories:

Landmark study unlocks stem cell, DNA secrets to speed therapies
In a groundbreaking study led by an eminent molecular biologist at Florida State University, researchers have discovered that as embryonic stem cells turn into different cell types, there are dramatic corresponding changes to the order in which DNA is replicated and reorganized.
Fat-regenerating 'stem cells' found in mice
Researchers have identified stem cells with the capacity to build fat, according to a report in the October 17th issue of the journal Cell, a Cell Press publication. Although they have yet to show that the cells can renew themselves, transplants of the progenitor cells isolated from the fat tissue of normal mice can restore normal fat tissue in animals that are otherwise lacking it.
A link between mitochondria and tumor formation in stem cells
Researchers report on a previously unknown relationship between stem cell potency and the metabolic rate of their mitochondria –a cell's energy makers. Stem cells with more active mitochondria also have a greater capacity to differentiate and are more likely to form tumors.
Stem cells from testicles an option to embryos
(AP) -- Cells taken from men's testicles seem as versatile as the stem cells derived from embryos, researchers reported Wednesday in what may be yet another new approach in a burgeoning scientific field.
Breast stem cell fate is regulated by 'notch'
A normal developmental protein that sometimes goes awry has been implicated in breast cancer. This discovery indicates the mechanism by which inappropriate expression of the Notch pathway may contribute to breast cancer.
Can stem cells heal damaged hearts? No easy answers, but some signs of hope
Recent studies indicate that infusing hearts with stem cells taken from bone marrow could improve cardiac function after myocardial infarction (tissue damage that results from a heart attack). But in a recent systematic review, Cochrane Researchers concluded that more clinical trials are needed to assess the effectiveness of stem cell therapies for heart patients, as well as studies to establish how these treatments work.
Healthy blood vessels may prevent fat growth
The cells lining blood vessels are known to be important for maintaining health, but researchers at the Indiana University School of Medicine believe these cells may perform an unsuspected task – controlling the development of fat cells. Their findings are reported in the September issue of the journal Stem Cells.
'Baby' fat cells may be key to treating obesity
Immature, or "baby," fat cells lurk in the walls of the blood vessels that nourish fatty tissue, just waiting for excess calories to help them grow into the adult monsters responsible for packing on the extra pounds, researchers at UT Southwestern Medical Center have found in mice.

News discussion:

Medicine & Health news