When a blood vessel is diseased, damaged, or blocked, a vascular graft is often used to replace it in order to allow blood to flow normally again, in turn permitting adequate oxygen and nutrients to reach the heart. Placing a vascular prosthesis of this sort is a delicate task in and of itself and is further complicated by the lack of suitable synthetic alternatives. Currently, there are no vascular prostheses available for use in clinical settings that have a diameter of less than 4 mm. In addition, there are a number of purposes for which it would be extremely beneficial to have the use of synthetic prosthetics but for which there are currently no available options.
Even in the case of availability of these synthetic prosthetics, they are less than ideal because they lack antithrombotic properties, are not biocompatible, and do not offer sufficient resistance to infection. In an effort to address this absence, researchers, mostly from the Faculty of Medicine at Saga University in Japan, examined the possibilities for using a bio-printer to create vascular prostheses that would be printed from the cells of the patient receiving the implant. The results of this ongoing research were recently released in an article published in the journal PLOS ONE.
This builds on research being conducted in other areas of tissue engineering that have explored the possibilities for the creation of non-scaffolded tissue generation. The concept behind the non-scaffolded tissue printing has been advanced as key to the creation of a number of biological implant components and uses cells’ natural tendency to clump together and form a spheroidal structure. Among the authors of this paper is Koichi Nakayama from the Fusion Graduate School of Science and Engineering at Saga University who developed a Bio-3D printer system that would use these spheroids as if they were components of a filament and print them on to each other to create a three-dimensional structure.
Using this technique would allow for the loading of the bioprinter with these multicellular spheroids (MCS) and print out a structure that had been designed with 3D modeling software. In the experiment conducted for this paper, a total of 500 MCS were assembled into a single 3D structure supported by a needle array, as directed by the pre-designed computer model. It took a total of 1.3 hours to complete the print and after four days the needle array was removed without disturbing the stability of the structure.
Unfortunately, portions of this experiment involved both the use of ‘nude rats’ as subjects and then their euthanization. From the experimentation on the rats, the researchers were able to gauge the success of their efforts as they described in their paper, “Scaffold-Free Tubular Tissues Created by a Bio-3D Printer Undergo Remodeling and Endothelialization when Implanted in Rat Aortae“:
“We developed a novel method to create scaffold-free small caliber tubular tissue from MCSs using a ‘Bio-3D printer’-based system. We successfully implanted the tubular tissue into rats and showed that the inner luminal surface of the structure was covered with endothelial cells after implantation. Although several studies have attempted to use MCSs for tissue-engineered scaffold-free artificial vessels, to the best of our knowledge, this is the first report to show endothelial cells which cover the inner surface of the tubular tissue fabricated with a technology of regeneration and tissue-engineering when implanted in vivo.”
In other words, they have experienced some success with this method, enough to make its continued exploration a valuable opportunity. This could lead to the production of vascular prosthesis that would not only be more easily accepted by the body but could also be far more stable than other methods currently available. In the end what it really means is that it could not only improve lives, it could also save them.
So, next time you see a rat, you might just want to thank it; their species has made possible a number of advances in medical technology.
Discuss these findings in the 3D Printed Vascular Prostheses Research forum thread over at 3DPB.com.