3-D Printed Blood Vessels Made of Sugar Help Grow Artificial Liver
Medical advancements in the 21st Century are taking new shapes, and in some cases, those shapes are coming out of 3-D printers. A research team from the Massachusetts Technology Institute and the University of Pennsylvania have created entire networks of blood vessels printed from a mixture of sugars using the RepRap 3-D printer.
Tissue engineering could one day advance regenerative medicine to include making replacement organs from a patient's own cells. And though 2-D structures of many tissues have already been made in the lab, 3-D versions have eluded scientists.
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"The big challenge in understanding how to grow large artificial tissue is how to keep all the cells alive in these engineered tissues, because when you put a lot of cells together, they end up taking nutrients and oxygen from neighboring cells and end up suffocating and dying," Jordan Miller from University of Pennsylvania, told BBC News.
In order to mimic the complicated networks of natural organs and keep the cells within them alive, three dimensions are crucial. That's where 3-D printing comes in.
The researchers set about creating the hollow channels that run between the layers of thicker tissues in the body. The pressure of fluid running through the channels can sometimes force apart the seams created by traditional 3-D printing, in which single layers of cells are laid down one drop at a time.
To get around this problem, the team worked from the inside out.
Instead of printing tissue and leaving gaps for the vasculature layer by layer, the team designed 3-D networks in the shape of a vascular system and laid them in a mold using a sugar mixture of glucose, sucrose and dextran. Once the sugar mold is printed, living cells are introduced around the template of the vascular network, creating solid tissue. The sugar taking up the space of blood vessels then dissolves, leaving channels for fluid to flow through. To see the printer in action, check out this video:
The method harkens back to lost-wax casting, a technique used to make sculptures for millennia.
"Sometimes the simplest solutions come from going back to basics," Miller said. "I got the first hint at this solution when I visited a Body Worlds exhibit, where you can see plastic casts of free-standing, whole organ vasculature."
Once they had successfully created a vascular network with the 3-D printer, they tested the artificial organ to see if human blood vessels would survive the lab-grown environment. And just as blood vessels in the body naturally grow, they found that the cells injected into the artificial vascular network spontaneously generated new capillary sprouts to increase the network's reach.
They also pumped a nutrient-rich substance through the system and found that the liver cells within boosted production of albumin and urea, natural components of blood and urine which are important measures of liver-cell function and health.
"This new platform technology, from the cell's perspective, makes tissue formation a gentle and quick journey, because cells are only exposed to a few minutes of manual pipetting and a single step of being poured into the molds before getting nourished by our vascular network," said lead researcher Christopher Chen, according to Medical News Today.
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