Commentary on: “Tissue engineering: How to build a heart”

Decellularization and recellularization of hearts from newly dead donors is the latest fashion in cardiac tissue engineering. The first paper came out in 2008 in Nature Medicine (Ott et al., 2008), and news has been recently published in Nature again in July 2013 (Maher, 2013). Brendan Maher in this paper summarizes and comments on the latest important results on decellularization of a human heart and explains the steps that are necessary to build a heart from a decellularized organ. Two sources may be used to obtain a decellularized heart: human and pig heart. Another issue to resolve is the time of decellularization, since the detergents used may also destroy the architecture of the organ and adhesion molecules useful for the colonization of the newly introduced cells. The author also highlights two main problems, which cell type to introduce to the decellularized organ and how to establish and maintain the organ's ability to beat. Many researchers use a mixture of stem and progenitor cells from the blood vessels and from the heart; Ott and colleagues use induced Pluripotent Stem (iPS) cells. After having chosen the best progenitor cell, another problem is to let the introduced cells distribute uniformly in the decellularized scaffold, and to let them grow as they are in a natural environment. A way to improve cell growth in these scaffolds is to use bioreactors that electrically stimulate the heart and mimic forces of a beating heart. The most difficult step in implanting decellularized/recellularized organs is to connect them to the host body. The first problem is to connect vascularization of the new organ with the one of the host living animal. Ott's team and others have implanted reconstructed hearts into rats in parallel with other organs, but even if researchers have fed the organs with blood and get them to beat for a while, none of the hearts has been able to continue for long. At the moment researchers are able to implant recellularized hearts only in small animals. In the last 6 years many research groups tried to remove cells from a dead organ and to repopu-late it with stem cells or multipotent cells, immunologically matched to the patients, or decellularize the entire organ preserving chemotactic and pro-angiogenic properties, so that they can be successfully used for clinical tissue engineered airway clinical replacements in infants (Baiguera et al., 2010). It looks simple for tubular structures as the …