Dr. Sian E. Harding
The heart is arguably the greatest challenge for tissue engineers because of the extreme and repetitive forces and high metabolic demands (as well as the very low margin for error!). Importantly, the heart does not comprise a single cell type or function, and there is therefore not a single solution. This session aimed to break down the problem into its constituent parts: contracting muscle, pacemakers and vessels.
Wolfram Zimmermann from Hamburg began the session with thoughts about the source of muscle cells, with contributions from the chairs: Pieter Doevendans and myself. Human embryonic stem cells are now recognised as a reliable source of beating cardiomyocytes, but data presented showed that cardiac progenitor cells found in human atrium could also be used. Both these integrated into spontaneously beating grafts, and video evidence showed impressive contractile activity. New alternatives to the controversial embryonic stem cells were also presented, including exceptionally exciting data on cells derived by parthenogenesis from a mouse oocyte without embryo generation. There was a discussion of the alternative methods of application for these cells, to overcome the poor efficiency of injection into the myocardium. Both the spontaneously beating grafts, and composites of cells with smart materials gave advantages. Scale-up to produce the substantial quantity of cardiomyocytes needed was again discussed. While muscle function requires large numbers of cells, Hong-Fat Tse demonstrated that pacemakers could be generated from very small quantities of implanted or gene-transfected cells by modifying ion channel function. A pig model of sick sinus syndrome and its reversal by this strategy took implementation encouragingly close to a potential clinical application. An imaginative source of new vessels described by Dr Hoenicka was human umbilical cord, with its lining removed and the patients own blood used to reseed the vessel. This has the potential to provide a living tissue which will not be rejected: the production of immunologically compatible tissue was a theme throughout the session.
Clearly, tissue engineering for the heart is moving slowly but surely towards the clinic, with imaginative combinations of cells with natural and synthetic materials being designed. Perhaps the most encouraging message from this session is that it will not be necessary to build the myocardium in its entirety, but that clinically useful solutions can arise from these focussed efforts on the different functionalities that make up the heart.
Progress in cardiac and vascular tissue engineering
This congress report accompanies a presentation given at the ESC Congress 2008. Written by the author himself/herself, this report does not necessarily reflect the opinion of the European Society of Cardiology.
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