Retinal stem cells

Neuroscientists at the University of Cambridge, a hotbed of medical 3D printing technology, have arrived at a method of printing new cells onto cells extracted from the eyes of rats, and they say this novel technique may well lead to artificial tissue grafts which might halt oncoming blindness.

Dr. Barbara Lorber, of the Cambridge Department of Clinical Neurosciences

"The loss of nerve cells in the retina is a feature of many blinding eye diseases," said Dr. Barbara Lorber of Cambridge. "The retina is an exquisitely organized structure where the precise arrangement of cells in relation to one another is critical for effective visual function."

Lorber's work in general is focused on examining the role of activated retinal glia and identifying the mechanisms which underlie what she calls a "repair response." Her work is aimed at developing clinical therapies for the treatment of blindness and the repair of damaged CNS tracts following injuries to the spinal cord and brain.

While it may only be a "proof-of-concept" at this point, the findings published by Lorber and her team in the journal Biofabrication show promise in the real world.

To make it happen, Lorber and her team use two different types of cells found in the retinas of adult rats. One of those types, ganglion cells, transmit visual signals from the light-sensing cells of the retina. The other, glial cells, act as support and protective structures for neurons.

The team then uses a "piezoelectric" inkjet printer to "print" onto the cells without causing them damage or inhibiting their growth.

It's an old school technology used to a bleeding edge purpose. Piezoelectric technology is roughly the same process used in some commercial inkjet printers. Piezoelectric printers generate pressure electrically and then force ink out through a nozzle onto a substrate.

According to Lorber, cell printing requires a delicate balance. The viscosity and surface tension of the printing materials must be properly controlled to allow the introduction of often delicate cells in the process.

And as for worries that the violence of piezoelectric process itself might prove harmful to cell structures, the Cambridge team found "no significant distortion of the cell structures has been observed either immediately before or after cell ejection."

After assessing the effects of the printing process on cell number and viability, while the study found that cell numbers of both retinal glial cells and dissociated retinal cells were decreased – there were something like 57% fewer glial cells and 33% fewer retinal cells present after printing – the team say they believe "cell sedimentation" is at fault rather than actual destruction of the cells caused by the  printing process itself.

Professor Keith Martin, the co-author of the Cambridge paper, says this may well be just the start of what the technique can do.

"We plan to extend this study to print other cells of the retina. and to investigate if light-sensitive photoreceptors can be successfully printed using inkjet technology," Martin said. "We would like to further develop our printing process to be suitable for commercial, multi-nozzle print heads."