Meghan Bialt-DeCelie – ’19

One of the biggest problems with engineered tissues is the lack of a vascular system to transport essential nutrients and oxygen. This is the reason why larger and highly metabolic organs are the most difficult to develop with 3D printing.

Researchers from the University of California printed prevascularized tissues with microarchitectures using the fast and efficient method of microscale continuous optical bioprinting (µCOB). They used a combination of hydrogels GM-HA and GelMa to make channels for the prevascularized tissues. The researchers then developed multiple tissue constructs with the prevascularized systems. Red labeled human umbilical vein endothelial cells marked the location of the channels while the surrounding cells were comprised of green labeled HepG2 liver cells.

The 3D printed prevascularized tissues underwent in vitro testing to determine their viability and degradability. They tested the effectiveness of the µCOB method of printing with a cell viability assay of the tissues resulting in 85% viability, showing that it can perform as well, if not, better than previously used methods used by 3D bioprinters. A hydrogel degradation assay was performed to determine if the hydrogels are safe for in vivo studies. The hydrogels successfully biodegraded with the enzyme hyaluronidase, leaving behind channels.

Prevascularized and non-prevascularized control labeled 3D printed tissues were implanted in mice. After two weeks, prevascularized tissues formed an endothelial system, however unlike its non prevascularized counterparts, it could not maintain the originally printed pattern.

Future studies should test the µCOB printing with other biomaterials to create prevascularized tissues within the wide range possible constructs. The study mentioned the difficulty of replicating a degradation of the tissues in vivo, and this can be further explored before testing in more complex in vivo animal models. Furthermore, the prevascularized tissues are an area of improvement since they could not maintain the pattern originally printed.

References:

1. Zhu, Wei, et al. Direct 3D bioprinting of prevascularized tissue constructs with complex microarchitecture. Biomaterials (2017). doi:10.1016/j.biomaterials.2017.01.042
2. Image retrieved from: https://zh.wikipedia.org/wiki/3D%E6%89%93%E5%8D%B0