Heart Valve Engineered from Human Progenitors

Tissue engineering has made rapid strides in the past decade. One of its success stories is the artificial skin that can be used clinically in the management of patients with extensive burns or other situations with skin loss. Researchers are working on to make tissue engineered replacements for most of the organs and tissues in the human body including engineering artificial pancreas to synthesize insulin, artificial heart tissue and heart valves.

Tissue engineered heart valves may have significant clinical applications as many of the congenital heart diseases, which account for a significant percentage of the heart ailments in the children and the adults require heart valve replacements. Currently the heart valve replacements are done with the prosthetic valves made of synthetic materials. Risks in having prosthetic valves include infections and thromboembolism. To avoid thromboembolism, the patients with the heart valve replacement have to be on life-long anti-coagulation. Furthermore as child\'s heart grows in size, the prosthetic valves need to be replaced to match the growth, necessitating several repeat operations. The problems associated with the prosthetic valves can be minimized if the valves are made of human tissue which is antigenically similar to the patient and can grow along with the patient\'s heart. In this direction tissue engineering can help in designing better and biocompatible heart valves, with decreased incidence of the adverse effects of the prosthetic valves.

A group of researchers based in Europe have discovered a new concept of using human prenatal progenitor cells as an exclusive cell source to generate heart valves. The extra embryonically situated progenitor cells are obtained by a procedure called the prenatal ultrasound guided percutaneous umbilical cord blood sampling. This test is commonly done as a diagnostic test to determine the genetic make up of the baby. The progenitor cells were seeded into synthetic biodegradable leaflet scaffolds and placed in a bioreactor, which is conditioned to provide ideal environment for cell growth and differentiation. The heart valve thus obtained was compared with the normal heart valves and was found to have similarities in cellular organization, cell phenotypes and DNA content.

Most importantly the mechanical properties, considered vital due to the dynamic nature of the valves were found to be comparable to the native heart valves. The stress-strain pattern showed non-linear mechanical behavior similar to the native valves. The results were published in Circulation, the journal of the American Heart Association.Many of the congenital heart defects need to be repaired as soon as after birth, to prevent secondary damage to the newborns immature heart. The defects can be detected before birth by means of ultrasound. So the present idea of taking the cells quite early and fabrication of heart valve replacements ready for use in the early neonatal period is very helpful.

Reference: DOI: 10.1161/CIRCULATIONAHA.105.001040