Using tissue engineering, researchers at Children's Hospital Boston have developed pulmonary-valve replacements for infants and children which could grow as the child grows older, thus removing the need for multiple replacement operations.

The researchers [snip] first isolated endothelial progenitor cells (precursors of the cells that line blood vessel walls) from the blood of laboratory animals. They then "seeded" the cells onto tiny, valve-shaped biodegradable molds and pre-coated with proteins found in the natural "matrix" that surrounds and supports cells.

Experimenting with different matrix proteins and growth factors, they were able to make pulmonary valve leaflets that had the right mechanical properties - sturdy yet pliable. Tests showed the original cells had differentiated to form both endothelial cells and smooth-muscle-like cells and added to the surrounding matrix to hold them together.

The technique has been published in the September 11 issue of Circulation.