3D tissue-printing company Prellis Biologics Inc. announced it has printed human tissue with viable capillaries, bringing their goal of printing human replacement organs closer to reality. "A major goal in tissue engineering is to create viable human organs, but nobody could print tissue with the speed and resolution needed to form capillaries," said Melanie Matheu, CEO and co-founder of Prellis Biologics. "At Prellis, we've now developed that technology, paving the way for important medical advances and, ultimately, functional organ replacements." Prellis' holographic 3D-printing technology can create the complex microvascular and scaffolding that allows human tissue to survive. Printing speed is crucial, since cells can only survive for a limited amount of time without a blood supply. And tissue that is densely packed with cells will die in less than 30 min unless oxygen and nutrients can be supplied immediately through capillaries. Fine printing resolution is as vital as speed, since capillaries are microscopic in size — about 5 to 10 μm in diameter. Prellis' technology can print with resolutions as small as 0.5 μm. Until now, it would take weeks or more to print just a centimeter cube of human tissue with microvasculature. Prellis' technology can print high-resolution tissue structures up to 1000× faster, with the vasculature in place. "The speed we can achieve is limited only by the configuration of the optical system," Matheu said. "We are now exploring custom optical system development, which will dramatically increase our capabilities. Our ultimate goal is to print the entire vascular system of a kidney in 12 hours or less." Prellis Biologics is a developer of 3D printing and stem cell technology for tissue engineering.