On average, 22 people in America die each day because a vital organ is unavailable to them.1 However, recent advances in 3D printing have made manufacturing organs feasible for combating the growing problem of organ donor shortages.
3D printing utilizes additive manufacturing, a process in which successive layers of material are laid down in order to make objects of various shapes and geometries.2 It was first described in 1986, when Charles W. Hull introduced his method of ‘stereolithography,’ in which thin layers of materials were added by curing ultraviolet light lasers. In the past few decades, 3D printing has driven innovations in many areas, including engineering and art by allowing rapid prototyping of various structures.2 Over time, scientists have further developed 3D printing to employ biological materials as a modeling medium. Early iterations of this process utilized a spotting system to deposit cells into organized 3D matrices, allowing the engineering of human tissues and organs. This method, known as 3D bioprinting, required layer-by-layer precision and the exact placement of 3D components. The ultimate goal of 3D biological modeling is to assemble human tissue and organs that have the correct biological and mechanical properties for proper functioning to be used for clinical transplantation. In order to achieve this goal, modern 3D organ printing is usually accomplished using either biomimicry, autonomous self-assembly, and mini-tissues. Typically, a combination of all three techniques is utilized to achieve bioprinting with multiple structural and functional properties.
The first approach, biomimicry, involves the manufacture of identical components of cells and tissues. The goal of this process is to use the cells and tissues of the organ recipient to duplicate the structure of organs and the environment in which they reside. Ongoing research in engineering, biophysics, cell biology, imaging, biomaterials, and medicine is very important for this approach to prosper, as a thorough understanding of the microenvironment of functional and supporting cell types is needed to assemble organs that can survive.3
3D bioprinting can also be accomplished through autonomous self-assembly, a technique that uses the same mechanisms as embryonic organ development. Developing tissues have cellular components that produce their own extracellular matrix in order to create the structures of the cell. Through this approach, researchers hope to utilize cells themselves to create fully functional organs. Cells are the driving force of this process, as they ultimately determine the functional and structural properties of the tissues.3
The final approach used in 3D bioprinting involves mini-tissues and combines the processes of both biomimicry and self-assembly. Mini-tissues are the smallest structural units of organs and tissues. They are replicated and assembled into macro-tissue through self-assembly. Using these smaller, potentially undamaged portions of the organs, fully functional organs can be made. This approach is similar to autonomous self-assembly in that the organs are created by the cells and tissues themselves.
As modern technology makes it possible, techniques for organ printing continue to advance. Although successful clinical implementation of printed organs is currently limited to flat organs such as skin and blood vessels and hollow organs such as the bladder,3 current research is ongoing for more complex organs such as the heart, pancreas, or kidneys.
Despite the recent advances in bioprinting, issues still remain. Since cell growth occurs in an artificial environment, it is hard to supply the oxygen and nutrients needed to keep larger organs alive. Additionally, moral and ethical debates surround the science of cloning and printing organs.3 Some camps assert that organ printing manipulates and interferes with nature. Others feel that, when done morally, 3D bioprinting of organs will benefit mankind and improve the lives of millions. In addition to these debates, there is also concern about who will control the production and quality of bioprinted organs. There must be some regulation of the production of organs, and it may be difficult to decide how to distribute this power. Finally, the potential expense of 3D printed organs may limit access to lower socioeconomic classes. 3D printed organs, at least in their early years, will more likely than be expensive to produce and to buy.
Nevertheless, there is widespread excitement surrounding the current uses of 3D bioprinting. While clinical trials may be in the distant future, organ printing can currently act as an in vitro model for drug toxicity, drug discovery, and human disease modeling.4 Additionally, organ printing has applications in surgery, as doctors may plan surgical procedures with a replica of a patient’s organ made with information from MRI and CT images. Future implementation of 3D printed organs can help train medical students and explain complicated procedures to patients. Additionally, 3D printed tissue of organs can be utilized to repair livers and other damaged organs. Bioprinting is still young, but its widespread application is quickly becoming a possibility. With further research, 3D printing has the potential to save the lives of millions in need of organ transplants.
References
- U.S. Department of Health and Human Services. Health Resources and Services Information. http://www.organdonor.gov/about/data.html (accessed Sept. 15, 2015)
- Hull, C.W. et al. Method of and apparatus for forming a solid three-dimensional article from a liquid medium. WO 1991012120 A1 (Google Patents, 1991).
- Atala, A. and Murphy, S. 3D Bioprinting of Tissues and Organs. Nat. Biotechnol. [Online] 2013, 32, 773-785. http://nature.com/nbt/journal/v32/n8/full/nbt.2958.html (accessed Sept. 15, 2015)
- Drake, C. Kasyanov, V., et al. Organ printing: Promises and Challenges. Regen. Med. 2008, 3, 1-11.