Building organs piece by piece

It might not be long before we see a headline such as: “First tissue‐engineered heart valve saves child's life”. A team of researchers in Switzerland, Germany and the USA have succeeded in engineering a living heart valve that resembles normal valves in both microstructure and mechanical properties. Simon P. Hoerstrup, a group leader at the University Hospital in Zurich, Switzerland, and his colleagues fabricated these heart valves from bioabsorbable polymers that had been seeded with ovine myofibroblasts and endothelial cells, and then grown for 14 days in a bioreactor (Hoerstrup et al , 2000; Hoerstrup et al , 2002). When implanted into juvenile sheep, they behaved like normal heart valves and lasted for up to five months. But any medical benefit for human patients will take more time. “Although a lot has been done regarding tissue engineering of heart valves over the past ten years, we are still not there,” Hoerstrup commented. “Many disciplines are involved and only a longstanding synergic scientific effort will lead to optimized results” (Mol & Hoerstrup, 2004). His comments also apply to tissue engineering in general. Clearly, creating a complex organ, such as a kidney, liver or lung, in vitro presents so many scientific challenges that it is still a thing of the distant future. Nevertheless, tissue engineering has become a multidisciplinary research field, which involves biologists, chemists, materials scientists and clinical researchers, and promising advances have been made over the past two decades, particularly in creating three‐dimensional matrices on which to grow new tissues.> …the main problems for engineering more complex tissues are angiogenesis … and developing three‐dimensional matrices on which to grow the new tissue…The results produced by Hoerstrup and colleagues with artificial heart valves also illustrate the broader social and medical needs for replacement tissues. In 2000, approximately 87,000 heart valves were …