Some of the most exciting news in medical research involves the 3D printing of body parts. Researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University and the Harvard School of Engineering and Applied Sciences (SEAS) have developed a bioprinting method that creates intricately patterned 3D tissue constructs with multiple types of cells and tiny blood vessels. This work is a major step toward a longstanding goal of tissue engineers: creating human tissue constructs realistic enough to test drug safety and effectiveness.
The method also represents an early but important step toward building fully functional replacements for injured or diseased tissue that can be designed from CAT scan data using computer-aided design (CAD), printed in 3D at the push of a button, and used by surgeons to repair or replace damaged tissue. This is the foundational step toward creating 3D living tissue, said Jennifer Lewis, Ph.D., senior author of the study, who is a Core Faculty Member of the Wyss Institute for Biologically Inspired Engineering at Harvard University, and the Hansjörg Wyss Professor of Biologically Inspired Engineering at Harvard SEAS.
One of the biggest hurdles tissue engineers have struggled with is in producing lab-grown vascularized human tissues robust enough to serve as replacements for damaged human tissue. Scientists have printed human tissue before, but they have been limited to thin slices about a third as thick as a dime. When they attempt to print thicker layers of tissue, cells on the interior starve for oxygen and nutrients and are unable to remove carbon dioxide and other waste, so they suffocate and die.
In the past, Lewis and her partner, David Kolesky, a graduate student in SEAS and the Wyss Institute, pioneered a broad range of novel inks that solidify into materials with useful electrical and mechanical properties. But, the researchers needed functional inks containing key ingredients of living tissues, so they developed two “bio-inks” – tissue-friendly inks, one containing extracellular matrix (biological material that knits cells into tissues), and another ink that contained both extracellular matrix and living cells. To create blood vessels, they developed a third ink that melts as it cools rather than as it warms. This allowed the scientists to first print an interconnected network of filaments, then melt them by chilling the material and suctioning the liquid out to create a network of hollow tubes, or vessels. The Harvard team printed 3D tissue constructs with a variety of architectures, culminating in a structure approaching the complexity of solid tissues.
In How 3-D Printing Body Parts will Revolutionize Medicine, the evolution of the process now referred to as bioprinting is discussed. Dean Kamen, founder of DEKA Research and Development which holds more than 440 patents, believes we are at a tipping point in this research. In labs across the country, bioengineers have begun to print prototype body parts: heart valves, ears, artificial bone, joints, meniscus, vascular tubes, and skin grafts. “When you get better tools, you start thinking in different ways. We now have the ability to play at a level we couldn’t play at before,” says Kamen.