Blood vessels are the lifeline of any organ.
The dense web of channels, spread across tissues like a spider web, allow oxygen and nutrients to reach the deepest cores of our hearts, brains, and lungs. Without a viable blood supply, tissues rot from the inside. For any attempt at 3D printing viable organs, scientists have to tackle the problem of embedding millions of delicate blood vessels throughout their creation.
It’s a hideously hard problem. Although blood vessels generally resemble tree-like branches, their distribution, quantity, size, and specific structure vastly differs between people. So far, the easiest approach is to wash out cells from donated organs and repopulate the structure with recipient cells—a method that lowers immune rejection after transplant. Unfortunately, this approach still requires donor organs, and with 20 people in the US dying every day waiting for an organ transplant, it’s not a great solution.
This week, a team from Harvard University took a stab at the impossible. Rather than printing an entire organ, they took a Lego-block-like approach, making organ building blocks (OBBs) with remarkably high density of patient cells, and assembled the blocks into a “living” environment. From there, they injected a “sacrificial ink” into the proto-tissue. Similar to pottery clay, the “ink” hardens upon curing—leaving a dense, interconnected 3D network of channels for blood to run through.
As a proof of concept, the team printed heart tissue using the strategy. Once the block fused, the lab-made chunk of heart could beat in synchrony and remained healthy for at least a week.