All eyes on bioprinting

3D printing is in fashion. Clothes, prosthetic limbs, guns and even pizza, you name it—just about anything can be printed these days. Even living cells.

Bioprinting is an emerging technology that promises to revolutionise the field of regenerative medicine. The idea is simple: you load a printer cartridge with cells removed from a patient or grown in the lab, and then print a brand new tissue or organ ready for transplantation. Alternatively, you could print healthy tissue directly onto a patient’s wound in the operating room. For now, scientists and biotech companies have managed to print several cell types, and there has been some progress in making cartilage, skin and heart muscle tissue. Printed tissues like these could be invaluable for drug testing in preclinical studies and for regenerative medicine. Imagine if we could replace damaged brain tissue in people suffering from neurodegenerative diseases like Alzheimers, or treat blindness with transplanted eye tissue. But how does bioprinting work?

By a lucky coincidence, the size of the nozzles of inkjet printers is roughly the same of an average animal cell, so scientists can use or adapt commercial printers for bioprinting. Just like a conventional 3D printer, which creates objects by laying down liquefied material (like plastic, metal or even chocolate) in layers, bioprinters work by spitting out cell after cell onto a surface to, in theory, build a 3D-shaped living tissue. But there is a caveat. Some cells are not happy to be squeezed through a printhead, like neural cells for example, which have a limited ability to survive and grow in culture. 

Now, researchers from the University of Cambridge (UK) report that they have successfully printed two types of rat neural cells from the retina, the light-sensitive tissue at the back of the eye: ganglion cells, which transmit visual information to the brain, and glial cells, which insulate, support, protect and feed neurons.

Barbara Lorber and colleagues pushed a gel containing the cells through a piezoelectric inkjet printer and then tried to grow them in culture to test their survival rate. Piezoelectric printers are not commonly used for bioprinting because they use an electrical pulse to eject the ink drops, and this was thought to break cell membranes. But this is not what the team found. The large majority of printed ganglion and glial cells were able to survive and grow in culture. They also seemed to retain their function—glial cells released growth-promoting molecules, and in turn ganglion cells responded to these signals by growing more of the tiny processes that carry messages to neurons.

In recent years, stem cells transplants and electronic retina implants were shown to partially restore sight in patients with retinal degeneration, but these improvements were modest. Although preliminary, the new results by the Cambridge team provide the proof-of-principle that the production of functional retinal tissue by bioprinting could one day become a reality.

Reference:

Lorber B., Hsiao W.K., Hutchings I.M. & Martin K.R. (2014). Adult rat retinal ganglion cells and glia can be printed by piezoelectric inkjet printing, Biofabrication, 6 (1) 015001. DOI: 10.1088/1758-5082/6/1/015001

This article was published in Lab Times on the 10-02-2014 (print). 

Image credit: namida K/Everystockphoto