Science sub-journal: 3D printing plant cells

A new study from North Carolina State University demonstrates a replicable way to "bioprint" these cells through a 3D printer to study cellular communication
between different types of plant cells.
Learning more about how plant cells communicate with each other — and how they communicate with the environment — is key to understanding the function of plant cells and may ultimately lead to the creation of better crop varieties and optimal growing environments
.

The researchers bioprinted cells from the model plants Arabidopsis thaliana and soybeans, not only to study whether plant cells would survive — and for how long — after being bioprinted — but also to study how they acquired and altered their properties and functions
.

"Plant roots have many different types of cells that have special functions," said Lisa Van den Broeck, a postdoctoral researcher at North Carolina State University who is the first author
of the paper describing the work.
"There are also different genes that are expressed; Some are specific.

We want to know what happens after you bioprint living cells and put them into the environment you designed: Are they alive and doing what they're supposed to do?"

Van den Broeck said: "Instead of 3D printing ink or plastic, we use 'bioink' or living plant cells
.
The mechanisms of the two processes are the same, but there are some significant differences for plant cells: a UV filter is used to keep the environment sterile, and multiple printheads (instead of one) can print different bioinks
at the same time.
”

Living plant cells or protoplasts without a cell wall are bioprinted along with nutrients, growth hormone, and a thickener called agarose
, a seaweed compound.
Agarose helps provide cellular strength and scaffolding, similar to the mortar
that supports the bricks of a building's walls.

"We found that using the right scaffolds was critical," said Ross Sozzani, a professor of plant and microbial biology at North Carolina State University and co-corresponding author
of the paper.
"When you print bioink, you need it to be liquid, but when it comes out, it needs to be solid
.
Mimicking the natural environment helps keep cell signals and cues happening
as they do in soil.
"Studies have shown that more than half of the 3D bioprinted cells are alive and divide over time to form microcalluses, or small cell colonies
.

Van den Broeck said: "We expected good viability the day the cells were bioprinted, but we never kept the cells for a few hours after they were bioprinted, so we didn't know what would happen
a few days later.
A similar range of viability is shown after artificially pipetting the cells, so the 3D printing process does not appear to cause any harm
to the cells.
”

Sozzani said: "This is a process that is difficult to do manually, and 3D bioprinting controls the pressure of the droplets and the speed of
the droplet printing.
Bioprinting offers better opportunities for high-throughput processing and control of cell structures after bioprinting, such as layers or hive shapes
.
The researchers also bioprinted individual cells to test whether they were able to regenerate, or divide and multiply
.
The results suggest that Arabidopsis root and blast cells require different nutrient combinations and scaffolds for optimal viability
.
Meanwhile, more than 40 percent of soybean embryonic cells are still alive two weeks after bioprinting and divide over time to form microcalluses
.

Sozzani said: "This shows that 3D bioprinting technology can be used to study cell regeneration
in crops.
" Finally, the researchers studied the cellular properties
of bioprinted cells.
Arabidopsis root cells and embryonic soybean cells are known for
their high proliferation rate and lack of fixed properties.
In other words, just like animal or human stem cells, these cells can turn into different cell types
.

"We found that bioprinted cells can obtain the identity of stem cells; They divide, grow and express specific genes," says
Van den Broeck.
"When you bioprint, you print populations
of entire cell types.
We were able to examine the genes expressed by individual cells after 3D bioprinting to understand any changes in
cell identity.
The researchers plan to continue studying cellular communication after 3D bioprinting, including at the
single-cell level.

"Overall, this study shows the powerful potential
of using 3D bioprinting to identify the best compounds needed to support plant cell viability and communication in a controlled environment," Sozzani said.

Establishing a reproducible approach to study cellular functions of plants cells with 3D bioprinting