Microscaffolds: A new strategy in tissue engineering

Date:
April 12, 2022
Source:
Vienna University of Technology
Summary:
A new strategy in tissue engineering has been developed:
Tiny spherical microscaffolds are created in a high precision
3D printer. They are cultivated with living cells and then
assembled. The cells keep multiplying, creating a tissue, the
scaffolds are eventually degraded.



FULL STORY ==========================================================================
It is an age old dream of medicine: if arbitrary kinds of tissue could
be produced artificially from stem cells, then injuries could be healed
with the body's own cells, and one day it might even be possible to
produce artificial organs. However, it is difficult to get cells into
the desired shape. The methods that have existed so far can be divided
into two fundamentally different categories: Either one first creates
small tissue building blocks, such as round cell agglomerates or flat
cell sheets, and then assembles them, or one initially creates a fine,
porous scaffold that is then cultivated with cells. Both approaches have advantages and disadvantages.


==========================================================================
At TU Wien (Vienna), a third approach has now been developed: Using
a special laser-based 3D printing technique, micro-scaffolds with a
diameter of less than a third of a millimetre can be produced, which
can accommodate thousands of cells. In this way, a high cell density
is present from the start, but one still has the flexibility adapt the
shape and mechanical properties of the structure.

With scaffold or without? "The scaffold-based approaches that have
been developed so far have great advantages: If you first make a porous scaffold, you can precisely define its mechanical properties," says Dr
Olivier Guillaume, lead author of the current study, who is researching
at TU Wien in the team of Prof Aleksandr Ovsianikov at the Institute of Materials Science and Technology. "The scaffold can be soft or hard as
needed, it consists of biocompatible materials that are degraded in the
body. They can even be equipped with special biomolecules that promote
tissue formation." The downside, however, is that it is difficult to
quickly and completely populate such a scaffold with cells. A lot of
manual work is still needed here today, even though research is already
being done on automated processes.

Especially with large scaffolds, it takes a long time for the cells
to migrate into the interior of the structure; often the cell density
remains very low and inhomogeneous.

The situation is completely different if no such scaffold is used. It
is also possible to simply grow small cell agglomerates, which are then
joined together in the desired shape so that they eventually merge. With
this technique, the number of cells is large from the start, but there
are hardly any possibilities to intervene in the process. For example,
it can happen that the cell spheres change their size or shape and the
tissue ends up with different properties than desired.



========================================================================== Living cells meet high-resolution 3D printing process "We have now
succeeded in combining the advantages of both approaches -- using an
extremely high-resolution 3D printing method that we have been researching
here at TU Wien for years," says Prof. Aleksandr Ovsianikov.

This technique, two-photon polymerisation, uses a light-sensitive material
that is cured with a laser beam exactly at the desired positions. In
this way, structures can be produced with an accuracy in the range of
less than one micrometre.

This laser method is now used to create filigree, highly porous scaffolds
with a diameter of just under a third of a millimetre. The design of
these micro- scaffolds enables the rapid generation of cell agglomerates inside. At the same time, the cells are protected from external mechanical damage, similar to the way a rally driver is protected by a race car
roll cage.

"These cell-filled scaffolds are relatively easy to handle and can
coalesce," explains Aleksandr Ovsianikov. "When many of them are brought
into direct contact, it is possible to create large tissue constructs
with a high initial cell density in a short time. Still, we can control
the mechanical properties of the structure well." Cartilage and
bone as first target tissues The underlying concept of this novel
tissue engineering strategy was already presented in detail by the
research group in 2018. Now, for the first time, it has been possible
to show that this method actually works: "We were able to show that the
method actually delivers the benefits we were hoping for," says Aleksandr Ovsianikov. "We used stem cells for our experiments, which can be induced
to produce either cartilage or bone tissue. We were able to show that
the cells from neighbouring scaffold units do indeed merge and actually
form a single tissue. In doing so, the structure retains its shape. In
the future, these scaffold units could even be made injectable for use
in minimally invasive surgery."

========================================================================== Story Source: Materials provided by Vienna_University_of_Technology. Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
* The_micro_scaffold_under_the_microscope ========================================================================== Journal Reference:
1. Olivier Guillaume, Oliver Kopinski-Gru"nwald, Gregor Weisgrab,
Theresia
Baumgartner, Aysu Arslan, Karin Whitmore, Sandra Van Vlierberghe,
Aleksandr Ovsianikov. Hybrid spheroid microscaffolds as
modular tissue units to build macro-tissue assemblies
for tissue engineering. Acta Biomaterialia, 2022; DOI:
10.1016/j.actbio.2022.03.010 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220412095332.htm

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