3D bio-printing: A medical revolution?

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As medicine advances, technology is playing an ever-increasing role. The development of CT and MRI scanners to see inside patients, pacemakers to keep hearts beating, and prosthetic limbs that interact with the nervous system, have proved how valuable technology can be for our health. Has technology got our backs again, this time with an organ transplant crisis?

There is a severe need for new organs for transplantation around the world. In the last decade, nearly 49,000 people have had to wait for a life-saving organ transplant, in the UK alone. Of those, over 6,000 people have died whilst waiting – all possibly preventable if organs had been available. The issue is, with an ageing population and a safer environment, there are fewer organs available for transplant, and more organ failures requiring a transplant. The vast majority of the demand is for kidneys, with over 5,400 on the current UK waiting list.

Bio-printing of tissues is not exactly new – it has been around since the early 2000s when it was discovered that cells could be sprayed out of printer nozzles without being damaged. Today, the most common method of bio-printing is by using a scaffold of printed biomaterial, which can be made of synthetic and natural polymers and usually dissolves over time. This scaffold can form the main shape of the organ or structure required, from computer modelling and 3D scans. Meanwhile, cells from a human are removed, separated, grown outside the body, and then coated onto the scaffold structure. The scaffold, complete with living cells, can then be incubated and the cells take the form of the scaffold as it degrades.

Another more recent method has been to not use the scaffold structure at all, but instead a bio-ink, which can then be used just as plastic would in a 3D-printer. The bio-ink contains hydrogel (99% water), to help maintain integrity and shape whilst the cells fuse to form living tissue. Different layers are built up to form three-dimensional shapes, and different inkjets can lay different cells. The cells can self-organise and, eventually, after incubation and washing the gel away, form the organ or structure required.

The main challenge with printing organs is creating a blood supply to the organs. Normally, thousands of tiny capillaries provide every cell in an organ with oxygen and nutrients, and remove the waste or excreted products, keeping the cells alive. Without the vascularisation of the organs, they cannot survive or grow to large, transplantable organs. However, a new approach has been taken with recent research, using tiny fibres, coated with cells, as a mould for new capillaries. Once removed, the fibres leave behind a network of capillaries, within the cell structure of the organ.

Whilst it seems the use of 3D-printing live tissue is confined to synthetic organs for transplant, there are already many applications of this technology. Major skin care companies have already started to use printed human skin in tests for new products such as sun cream, as the live tissue provides an unparalleled opportunity for clinical trials. Additionally, the use of 3D-printed tissues reduces the requirement of animals and volunteers for pharmaceutical and cosmetic testing, avoiding danger and harm to both.

The bio-printing of human organs not only would reduce waiting times for donor organs, and thus reduce the number of preventable deaths, but also the organs or tissue could be specifically created for the individual (printing with cells taken from biopsies). This would eliminate the issue of organ rejection, which currently affects about 15% of kidney transplants.  In the future, doctors could print human bone using scans of the patient to perfectly replace missing or damaged bones, in hip replacement for example, without the need for metal structures.

An even more far-fetched example of how beneficial bio-printing in medicine could be is in the treatment of severe skin burns. The layers of skin for grafts could be printed, reducing the need for skin grafts from existing tissue which produce additional wounds and scars. The synthetic skin could overcome the issue of not having sufficient epidermal tissue from live samples, and help limit scars and healing time.

However, whilst there are promising opportunities for the use of bio-printing, the concept of printing live tissue also raises some serious ethical questions. We are still in very early stages of development, but scientists are already pushing over the limit of what is “natural”.

It is possible that, in the future, this technology could be used for human enhancement. Surely if bio-printing can be used in “replacing” body parts, we could use it for creating a human with abnormal capabilities? Imagine stronger, more flexible bones; and muscles with more fast-twitch fibres. The difficulty is that developing the technology for positive purposes – such as helping sufferers of diseases like osteoporosis to live normal lives – can lead to misuse and abuse of it. For example, athletes could start using bio-printing to give themselves these “upgrades”. In current society, it is unacceptable to “dope” to improve performance, but could the future hold sport with artificially-aided humans, and include an increasingly-important technological race, reminiscent of Formula 1 style?

Another major hurdle is the safety of actually combining naturally-grown tissue with the 3D-printed tissue. The risks are unknown. As with most developing or developed technologies in medicine, the disadvantages can often not be found until after many years (or decades) of implementation. How can we test the safety of using bio-printed material without exposing people to the unknown, yet potential, risks?

Many could argue that using 3D-printed organs and tissues is “unnatural” and morally incorrect; that we should not be intervening with the “normal” development and life cycle. But the whole role of physicians is based on the idea of treating illnesses – increasingly using new technology. If we can replace a faulty heart valve with a mechanical one, or have a pacemaker implanted, then why not just print a fully functioning heart for transplantation? Where and what is the limit of human intervention?

Clearly, 3D-printing human tissue and organs has huge potential to save many unnecessary deaths, and completely transform the treatment of many patients. However, this exciting technology poses a question: to what extent we should interfere with the human body?