From Vision to Mission in Myocardial Restoration

Abstract

What do myocardial restoration and hyperspace theory have in common? The usual perception of tissue engineering, the fl edgling new science, is of an art in 3 dimensions aimed at the reproduction of natural tissue in terms of structure and function. However, in the case of the heart, more than 3 dimensions need to be realized: the 4 th is the heart rhythm, and the 5 th is the contractile action and mechanics. Any ambitious attempt to manufacture cardiac muscle will have to address some unique issues if the product is to be one of high fi delity to nature. In the following, some important aspects of myocardial restoration will be discussed. Some 10 years ago, aspiring tissue engineers and heart surgeons such as us, stood up and stated that Homo sapiens would be producing the fi rst bioartifi cial left heart chamber within the decade. Unfortunately this prediction has proven premature, if not naive. This is for obvious reasons. First, the heart is a highly asymmetric organ. The architecture of the diverse portions of the heart differs from site to site. The left ventricle is built differently from the right, and fulfi lls its function on a different scale. Furthermore, the form of the heart is not that of a simple sphere. Would it be so, then the maximal possible ejection fraction would not exceed 15%. The heart comprises a helix of uniquely arranged muscular bands (Torrent-Guasp bands), overlaying each other at an angle of approximately 60°. 1 During systole, the heart functions as a vortex, thereby exploiting the maximal power possible from the muscular elements. These unique properties have not even been addressed so far by tissue engineering. All constructs without exception have been built in a symmetric fashion. With the available technology, it may be possible to produce a 3-dimensional graft that is shaped with 3 overlying layers and can be excited to twist as a vortex, but the idea has not been approached systematically so far. What has been achieved in the recent past is a mixture of collagen scaffolds and cells, and some 2-dimensional mechanical training of the constructs. 2