Using 3D printing, medical researchers have been able to create artificial blood vessels based on the human circulatory system.
According to the international team of researchers from the University of Sydney, Harvard and Stanford universities, and the Massachusetts Institute of Technology, the technique is fundamental for growing large, complex tissues, and is a step toward printing transplantable tissues and organs.
Blood vessels form an intricate network, transporting nutrients and oxygen throughout the body and disposing of waste, keeping organs working properly. Cells die without an adequate supply of oxygenated blood. The intricacy involved in growing blood vessels and capillaries has typically posed a challenge for medical researchers trying to move toward the engineering of large tissues and organs.
Ali Khademhosseini, a biomedical engineer and director of the Brigham and Women’s Hospital Biomaterials Innovation Research Center, explains:
Engineers have made incredible strides in making complex artificial tissues such as those of the heart, liver and lungs. […] However, creating artificial blood vessels remains a critical challenge in tissue engineering. We’ve attempted to address this challenge by offering a unique strategy for vascularization of hydrogel constructs that combine advances in 3-D bioprinting technology and biomaterials.
Template for Vessels
Their technique for constructing the network of blood vessels is based on 3D printing, which enabled them to make a template of numerous interconnected fibers. This fiber structure was used as a mold for the artificial blood vessels. The mold was created using agarose, a sugar-based molecule fiber and natural hydrogel-producing polymer.
The mold was covered with a protein-based material known as a hydrogel and reinforced with photocrosslinks, a means of forming bonds between molecules. Several common hydrogels were tested by the researchers, including methacrylated gelatin, a material often used in tissue engineering, and poly(ethylene glycol)-based hydrogels.
The agarose templates, when physically removed from the structure, leave a network of tiny channels. This material does not have to be dissolved, which has the potential to affect any cells encased in the gel. These channels are coated with human endothelial cells — the same cells that line human blood vessels — that have a range of functions, including creating new blood vessels.
These new bioprinted vascular networks, say the researchers, “promoted significantly better [endothelial] cell survival, differentiation and proliferation compared to cells that received no nutrient supply.” In other words, they work.
University of Sydney researcher Dr. Luiz Bertassoni explained the need this technology fills:
Thousands of people die each year due to a lack of organs for transplantation. […] Many more are subjected to the surgical removal of tissues and organs due to cancer, or they’re involved in accidents with large fractures and injuries. While recreating little parts of tissues in the lab is something that we have already been able to do, the possibility of printing three-dimensional tissues with functional blood capillaries in the blink of an eye is a game changer.
Although tissues can be replicated in the lab now, what these researchers are ultimately striving to do is regenerate complex, functional organs through a marriage of engineering and medicine. Perhaps one day, they theorize, a patient would be able to walk into a hospital and have an organ printed according to their specific needs. This bioprinting technique could be used to properly print all the cells, proteins, and blood vessels needed from a prompt on a computer screen.
They consider the printed structures they are now making to be prototypes that will evolve as the technique is improved and refined.
In the future, 3D printing technology may be used to develop transplantable tissues customized to each patient’s needs or be used outside the body to develop drugs that are safe and effective.
The researchers published their work — “Hydrogel Bioprinted Microchannel Networks for Vascularization of Tissue Engineering Constructs” — in the online journal Lab on a Chip.
Image by blueringmedia/123RF.
Source: “Hydrogel Bioprinted Microchannel Networks for Vascularization of Tissue Engineering Constructs,” by L.E. Bertassoni, A. Khademhosseini, et al., Lab on a Chip, Issue 13, 2014, DOI: 10.1039/C4LC00030G.
Source: “3-D Printing Breakthrough: Researcher Calls Ability to Bioprint Blood Vessels a ‘Game Changer,’ ” by Punditty, AllVoices, July 1, 2014.
Source: Brigham and Women’s Hospital.
Source: “A Step Closer to Bio-Printing Transplantable Tissues and Organs,” University of Sydney, July 2, 2014.
Video: “3D Printing at BWH,” by BWH Public Affairs.