Researchers say they have used a 3D printing technique to arrange human embryonic stem cells (hESCs) for the first time. The team from Heriot-Watt University in Scotland says that this will allow three-dimensional tissues and structures to be created using hESCs. They note that this is important because although advances have been made in 3D printing of organs and tissues, studies thus far have largely used animal cells.

“To the best of our knowledge, this is the first time that hESCs have been printed,” says co-author of the study, Will Wenmiao Shu, Ph.D. “The generation of 3D structures from hESCs will allow us to create more accurate human tissue models, which are essential for in vitro drug development and toxicity-testing. Since the majority of drug discovery is targeting human disease, it makes sense to use human tissues.”

In the longer term, this new method of printing may also pave the way for incorporating hESCs into artificially created organs and tissues ready for transplantation into patients suffering from a variety of diseases.

The scientists, in collaboration with Roslin Cellab, used a valve-based printing technique tailored to account for the delicate properties of hESCs. The hESCs were loaded into two separate reservoirs in the printer and were then deposited onto a plate in a preprogrammed, uniformed pattern. The cells were used to make spheroids by overprinting two opposing gradients of bio-ink; one of hESCs in medium and the other of medium alone. The resulting array of uniform sized droplets with a gradient of cell concentrations was inverted to allow cells to aggregate and form spheroids via gravity.

After printing, the researchers evaluated the effectiveness of their method. For example, they tested to see if the hESCs remained alive after printing and whether they maintained their ability to differentiate into different types of cells. They also examined the concentration, characterization, and distribution of the printed hESCs to assess the accuracy of the valve-based method.

“Using this valve-based method, the printed cells are driven by pneumatic pressure and controlled by the opening and closing of a microvalve,” explains Dr. Shu. “The amount of cells dispensed can be precisely controlled by changing the nozzle diameter, the inlet air pressure, or the opening time of the valve.

“We found that the valve-based printing is gentle enough to maintain high stem cell viability, accurate enough to produce spheroids of uniform size, and, most importantly, the printed hESCs maintained their pluripotency.”

Roslin Cellab will take the lead in developing 3D stem cell printing for commercial uses. “This is a scientific development which we believe will have immensely valuable long-term implications for reliable, animal-free drug-testing and, in the longer term, to provide organs for transplant on demand, without the need for donation and without the problems of immune suppression and potential organ rejection,” says Jason King, business development manager of Roslin Cellab.

The study is published today in the journal Biofabrication in a paper titled “Development of a valve-based cell printer for the formation of human embryonic stem cell spheroid aggregates”. This study includes the first analysis of the response of human embryonic stem cells to the printing process using this valve-based printing setup. For more on Dr. Shu’s recent research and the valve-based printer, read “Organ Printing from Stem Cells” from GEN’s July 2012 issue.

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