What the 3D printer can do
Teeth, hips and bone replacements from a 3D printer: The production of implants has already made great strides in routine clinical practice. However, there are still many unanswered questions when it comes to vital organs.
Replacement parts from 3D printers are already being used in orthopaedic and plastic surgery, and also in dentistry. The prosthetics required in these fields can be constructed layer by layer in a 3D printing process so that they exactly match the patient’s anatomy. The blueprint for this is provided by three-dimensional, scans of sections of the body generated by modern computer tomography or magnetic resonance imaging. A series of images is created, which are converted by a software application into layer-by-layer printing instructions for the 3D printer. Using a special plastic, the printer then builds a three-dimensional implant particle by particle into a shape that is an exact replica of the body part to be replaced, such as a tooth or the femoral head of a hip joint. The method is also already in use in plastic surgery, for instance for patients whose facial bone structure has been partially destroyed in an accident. The missing structures can be precisely replicated using the new technology and then implanted.
The vision: Fully functional organs from a 3D printer
However, behind these research activities in the field of tissue engineering lies a much greater vision: In the future, it is believed that innovative 3D cell printers will be able to reproduce human tissue structures and entire organs. The functional principle of these bioprinters is similar to that of the 3D printers sold today in retail stores. The only difference is that they do not use layers of plastic materials to generate a defined, three-dimensional object, but instead a mixture of living cells and biocompatible matrices. So far only small, and in most cases relatively simple cell structures such as cartilage, have been produced using this method. In some cases, artificial tracheas have already been successfully transplanted, but on closer examination, we can see that this is not such an astonishing achievement. The human trachea basically consists of simple cartilage. The individual structure of the trachea was reproduced by a 3D printer, the implants printed using a pulverised, biocompatible plastic and (in one case at least) additionally covered with some stem cells from the patient’s bone marrow. The advantage: Unlike in human-to-human organ transplants, the risk of rejection is likely to be significantly lower.
The arguments today against 3D organs
We will doubtless see dynamic advances in the areas of imaging processes and bioprinters, and, in conjunction with progress in regenerative medicine and bioengineering, this will open up entirely new possibilities. From a present perspective,however, the following reasons argue against the use of organs from a 3D printer in the near future:
- Complexity of organs: Nearly all organs and tissue structures are complex and multi-layered. Bioprinters would have to be capable of processing different cell types simultaneously to imitate the shape and texture of organic structures. This has still not been fully successful, even with compounds with a relatively simple structure, such as cartilage, which consists primarily of collagen and fibre materials.
- Integration into the body: It is not enough to have just anatomical copies, because organs and tissue do not have autonomous functions in the body. Instead, they need a functioning connection to an organism's cardiovascular and nervous systems to allow them to receive innumerable signals every second from other regions of the body and to fulfill their functions. In other words, regenerative medicine must find ways and means of fully , and above all successfully, integrating "printed organs" into an organism (with a connection to the cardiovascular and nervous systems and the metabolism).
- Rejection possible: At present, it is impossible to predict how the body will react to organs that have been reproduced using biotechnology. Even if cell material from the body's own stem cells is used exclusively for 3D printing, some risk still remains due to contamination with pathogens and antigens. While adverse reactions of the immune system could be suppressed with existing drugs, this would greatly diminish one of the greatest advantages of organ printing.
The forecast: Mature products in one or two decades at the earliest
It will be at least another one or two decades before artificial organs and tissue structures can be reproduced by bioprinters for transplantation purposes, and become established in routine clinical practice. On a smaller scale, however, bioprinters could come into routine use in the short to medium term – for instance, for directly printing cells onto wounds or replacing sections of bone and skin.