Heart Valves Fashioned From Stem Cells in Umbilical Cord Blood
MONDAY Nov. 10, 2008 -- Stem cells collected at birth from the umbilical cord may help doctors fashion new heart valves for children born with heart valve defects.
The tissue-engineered valves would have the advantage of growing with the child, the German researchers said.
"If we replace a valve in a child, they will need surgery several times in their lifetime, because they will grow out of the devices, so the ultimate goal is to have a construct which is able to grow with the child and only have to do the surgery once," said study author Dr. Ralf Sodian, a cardiac surgeon at University Hospital of Munich. "Earlier is better, if it's possible."
Presenting Monday at the American Heart Association's annual scientific sessions in New Orleans, Sodian reported that his team took stem cells from umbilical cord blood, stored them for 12 weeks, then seeded them on to eight heart valve scaffolds.
The stem cells went on to form a layer of tissue which included several characteristics of the "extracellular matrix," or the section of tissue outside of cells.
The engineered valves had almost 78 percent as much collagen as human tissue from pulmonary heart valves; 85 percent as much glycosaminoglycan as human tissue; and 67 percent as much elastin. Collagen and elastin are proteins in connective tissue, and glycosaminoglycan is a carbohydrate in connective tissue.
The valves also contained other proteins found in the human body.
"The whole idea of building a scaffold is a unique idea," said AHA spokesman Dr. Russell V. Luepker, the Mayo professor of epidemiology and community health at the University of Minnesota in Minneapolis. "We generally put progenitor cells in the heart and try to get them to grow muscle cells, and they're sitting in the middle of other cells."
"But to build a scaffold that looks like a heart valve then hope and anticipate that the cord blood cells will take that hint and differentiate, I think is very innovative," he added.
Still, the research is a long way from clinical practice.
"I don't think anyone has any idea if [these valves] would grow," Luepker said. "One may not know until it is put into a child, and the child grows. There are obviously a lot of hurdles to overcome."
Malfunctioning heart valves in babies that can't be surgically repaired are replaced with valves made from animal tissue, other human tissue or man-made materials.
Because these valves don't grow with the child, more surgeries for new valves are often needed.
There is also a possibility that the child's body will reject the artificial valve, although this is not so common, Luepker said.
A bigger issue is the sheer work that a heart valve has to perform. "The stresses on a heart valve are enormous," Luepker said. "They have to hold the blood back with each beat. The wear and tear on them which we see with metal and plastic valves is an issue, and those are fairly hard substances."
Cincinnati Children's Hospital has more on pediatric heart problems.
Posted: November 2008