Engineering Life: 3D-printed Organs Are Moving from Labs to Clinical Trials

Imagine entering a hospital with a failing liver and leaving with a new one — not from a donor, but engineered specifically for you, layer by microscopic layer, using your own cells. This isn’t a science fiction novel, but the new promise of bioprinting technology that stands to transform modern medicine.

Bioprinting is similar to building a complex LEGO structure — except we use living cells instead of plastic blocks. Just as a traditional 3D printer deposits material layer by layer to create physical objects, bioprinters carefully position living cells suspended in bio-inks (cell-friendly materials) to construct living tissues and, eventually, entire organs. Like following the LEGO manual, each cell must be precisely positioned and properly connected with the layers above and below. However, unlike LEGO, these layers contain living cells that need to communicate and function together.

The field has already demonstrated significant accomplishments. Research teams have successfully printed functional skin grafts for burn patients, cartilage for joint repairs, and experimental cardiac tissues with spontaneous contractile properties. A notable advancement occurred in 2022 when Harvard University's Wyss Institute researchers developed the SWIFT (Sacrificial Writing Into Functional Tissue) technique, enabling the creation of vascular channels within bioprinted tissues. This innovation allowed the team to produce cardiac tissue containing embedded blood vessels that maintained synchronised contractions for over seven days.

However, bio-printing remains in its early stages, with significant developments yet to be made. The primary objective remains the development of complex vital organs — kidneys, livers, and hearts. These organs present formidable challenges due to their multiple specialised cell types arranged in complex architectures. Any form of bio-printing has to account for the minute sophistication, such as intricate vascular networks, essential for nutrient and oxygen delivery.

The current research is encouraging and has exciting implications beyond organ replacement therapies. Bioprinted human tissues offer a potential revolution in pharmaceutical development by providing more physiologically relevant testing platforms than conventional cell cultures or animal models. Testing new compounds on bioprinted human tissues yields results that more accurately predict clinical outcomes, potentially reducing development timelines and costs.

Think of a bioprinted organ like a city. The biggest challenge is creating tiny blood vessels — similar to alleyways and footpaths — that transport oxygen and nutrients to cells deep inside the organ. Without these pathways, cells in the centre quickly die from starvation, just as neighbourhoods without supply routes would collapse. While we can build the organ's main structures, creating this intricate network of life-supporting vessels remains a significant hurdle, especially for larger organs like kidneys or livers. Additional technical hurdles include ensuring printed cells maintain their specialised functions and developing bio-inks that provide structural integrity and an optimal environment for cellular growth.

Industry experts project that relatively simple bioprinted tissues could achieve widespread clinical application within five years, with more complex organs potentially following within the next decade. This advancement could eliminate transplant waiting lists and reduce the need for immunosuppressive therapy, as organs would be manufactured using patient-derived cells. With approximately seventeen individuals dying daily while awaiting organ transplants, bioprinting offers a promising solution. The development of customised printed organ replacements marks the beginning of a new era in personalised regenerative medicine.

Illustration by Holly Ward