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A vision of the future: whole-heart tissue engineering

Scientists from the Department of Cardiac Surgery at the Heidelberg University Hospital have developed a bioreactor to produce a new heart from a patient’s own heart cells. The reactor mirrors the internal conditions of the human body. For example, the medium with the patient’s cells is pumped into the developing organ via small pulses that mirror the human heartbeat.

Cardiac surgeon Dr. Alexander Weymann standing next to the bioreactor which he and his team hope to use to grow human hearts. © University Hospital Heidelberg

The objective of a team of researchers from the Department of Cardiac Surgery at the Heidelberg University Hospital (Medical Director: Prof. Dr. Matthias Karck) is to grow a new and functional heart from a patient’s own heart cells. The technical conditions needed are now in place: In February 2011, a team led by Dr. Alexander Weymann and Dr. Bastian Schmack started operating a novel bioreactor that is big enough to house the new organ and that provides optimal growth conditions. The device was designed by the team of Weymann and Schmack.

The number of severely ill cardiac patients, whose lives can only be saved by a transplant, is constantly increasing. However, the number of donated hearts is far too low: According to the German Foundation for Organ Transplantation, 377 hearts were transplanted in 2010 and 16 combined heart-lung transplantations were carried out. Over the same period, almost twice as many people were added to the list of those awaiting heart transplants due to life-threatening heart diseases. “We need to develop new and innovative strategies for the treatment of cardiac patients in particular, and reduce our dependence on donated organs,” said Dr. Weymann who moved from the Charité in Berlin to Heidelberg University Hospital in 2009 where he established the “Whole Heart Tissue Engineering” work group.

The patients’ own cells colonise a fibre scaffold

Weymann’s idea is the following: the heart of a pig, which is similar to the human heart in terms of structure and size, is depleted of all cells in the laboratory using a method that was developed by Weymann’s team. The removal of all porcine cells prevents rejection reactions from occurring when the scaffold is transplanted into a patient. Once all cells are removed, the only thing that remains is a collagen-containing fibre scaffold. This scaffold is placed into a special culture chamber (a bioreactor), flushed with the patient’s cells that will eventually grow on the fibre scaffold. The method has already been successfully used for the cultivation of cardiac valves. “In the USA, the method has been used to grow functional rat hearts, but has so far not yet proved suitable for growing larger hearts,” said Weymann.

What the researchers need is a bioreactor that is large enough to house a human heart. Existing models have been designed for research on small rodents and the growth of cardiac valves. The cardiac surgeon thus sought industrial cooperation partners; in 2010, the Göttingen-based company Sartorius Stedum Biotech agreed to work with Weymann. The cooperation led to the development of a transparent reactor with internal conditions that mirror those of the human body. For example, the medium with the patient’s cells is pumped into the developing organ via small pulses that mirror the human heartbeat. All parameters can be controlled by Internet.

“Research is still in its early days"

The researchers still have a long way to go before they can engineer a whole heart substitute that is specifically tailored to human patients. It will very probably be quite a few years before this is achieved. A functional heart consists of several cell types that fulfil different tasks and are closely connected with each other. “The research in this field is just starting out. The process is highly complex. For example, we do not know the factors that guide the cells to the correct site in the tissue or those that make the heart beat,” said Weymann.

The researchers, who are part of the “Experimental Cardiac Surgery” research team headed up by Professor Dr. Gábor Szabó, now hope to find answers to these questions. Initial experiments will involve the cardiac cells of newborn rats. In future, the researchers also foresee using umbilical cord stem cells, removed and deep-frozen immediately after birth, for growing new hearts for cardiac patients.

Further information:
Dr. Alexander Weymann
University Hospital Heidelberg
Im Neuenheimer Feld 110
69120 Heidelberg
Tel.: +49 (0)6221 / 56 36 511
E-mail: Alexander.Weymann(at)med.uni-heidelberg.de
Website address: https://www.gesundheitsindustrie-bw.de/en/article/press-release/a-vision-of-the-future-whole-heart-tissue-engineering