Harvard researchers are developing new 3D techniques for creating human organs

For many years, scientists worldwide have been striving to advance organ cultivation. A major challenge lies in lab-grown organs, which are often too small for human application and lack the complexity needed to ensure adequate oxygen delivery within the body. However, progress is underway. A significant breakthrough came when a team of 3D researchers in Israel successfully printed a small human heart, showcasing the remarkable potential of bioprinting technologies in this field. While bioprinting holds immense promise for creating human organs, it is important to acknowledge that this area of research is still in its infancy.

A group of Harvard researchers is developing a solution that can bioprint blood vessels on living tissue. Their paper “Biomanufacturing of organ-specific tissues with high cell density and embedded vascular channels” published in Science Advances, highlights a new technique called SWIFT (Sacrificial Writing Into Functional Tissue). Their solution could enable the creation of larger organs that can deliver oxygen efficiently.

SWIFT technique

SWIFT is a technique by which vascular channels are 3D printed into living matrices composed of stem cell-derived organ blocks (OBBs). To explain the importance of this new process, co-author Mark Skylar-Scott says: “Rather than trying to 3D print the cells of an entire organ, SWIFT focuses only on printing the vessels needed to support a living tissue construct containing large amounts of OBB, which can ultimately be used therapeutically to repair and replace human organs with lab-grown versions containing patients’ own cells.”

In other words, this technique consists in the formation of a dense living matrix of OBB. “The formation of a dense matrix from these OBBs kills two birds with one stone: not only does it achieve a high cell density similar to that of human organs, but the viscosity of the matrix also allows a ubiquitous network of perfusion channels to be printed within it to mimic the blood vessels that support human organs,” explains co-author Sébastien Uzel.

At cold temperatures the matrix has a perfect consistency. It is soft enough to handle without damaging the cells, but thick enough to hold its shape, making it a perfect medium for sacrificial 3D printing. In this technique, a thin nozzle moves across this matrix depositing a strand of jelly-like ink that pushes cells away without damaging them. Then, when the cold matrix is ​​heated to 37°C, it begins to vaporize to become more solid. On the other hand, gelatin ink dissolves and can be washed off. This leaves behind a network of channels embedded in the tissue structure. The diameter of the channels can vary between 400 micrometers and 1 millimeter. The key is that these channels can be perfused with oxygenated media to nourish the cells.

When the scientists tested this, they noticed that organ-specific tissues that had been printed with embedded vascular channels using SWIFT remained viable, while tissues cultured without these channels experienced cell death within 12 hours. One of the most promising tests was to see whether tissues showed organ-specific functions. The team printed, evacuated and perfused a network of channels in a matrix composed of heart-derived cells and media that flowed through the channels for over a week. During that time, cardiac OBBs fused to form firmer heart tissue whose contractions became more synchronous and 20 times stronger, mimicking key characteristics of the human heart.