Claudia Castillo’s brand new, tailor-made windpipe, which European scientists created last year by lining the cartilage of a donated trachea with her own stem cells, has been heralding a new “cells into organs” era. Potentially, research could now improve radically “the ability of adult stem cells to treat patients with serious diseases”, said Professor Martin Birchall, one of the scientists involved in the pivotal surgery in Spain, whose spectacular success made the world’s headlines last November. Similar treatments, the same scientists anticipate, could soon be tried on transplants of other hollow organs, such as bowel, bladder and reproductive tract. No immunosuppressant drugs would be needed for a transplanted organ to be accepted by the body anymore. Professor Paolo Macchiarini, the Barcelona Hospital Clinic surgeon who operated on the 30-year old Colombian mother-of-two, admitted he had been very afraid: “Before this, we had been doing this work only on pigs. But as soon as the donor trachea came out of the bioreactor it was a very positive surprise.” Professor Birchall from the University of Bristol, who helped to grow the woman’s bone marrow cells into the cells that surround the windpipe, added that in 20 years’ time, virtually any transplant organ could be made this way. Their team, which included Italian scientists from the University of Padua and the Polytechnic of Milan, aims to go on doing windpipe and voice box transplants in cancer patients, which brings the dream of made-to-order spare body parts a little closer. In the meantime, many other techniques are being tested, such as joining clusters of cells to build larger tissues. Two American chemists, for instance, have just proved that they can assemble cells into microtissues that can perform functions such as secreting hormones and responding to them. Professor Carolyn Bertozzi from Berkeley University and Assistant Professor Zev Gartner believe that “people used to think of the cell as the fundamental unit. But the truth is, there are collections of cells that can do things no individual cell could ever be programmed to do. We are trying to achieve the properties of organs now, though not yet organisms”. Bertozzi and Gartner, who built a little gland similar to a lymph node, are convinced these 3-D cell arrangements introduce “a whole new level of cellular behavior”. Eventually, clusters could be built on yet more clusters into an artificial organ. But it remains to be seen which kinds of tissue their method may allow scientists to assembly from the bottom up. In the meantime, some bioengineers are working on another technique called bioprinting, which they hope may enable replacement limbs or organs to be “printed to order”. Such an approach involves taking a solution of cells called “bioink” and squirting it into an inkjet printer to make layers of cells on the microscale, which scientists could try to use to cover a 3-D scaffold of cells in order to see whether they can grow into any shape.
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