Growing fully-functioning specialized tissues, in the laboratory, is an ongoing project, in biomedical engineering, that promises easier and more efficient organ transplantation and repair. In the past, scientists have built contracting heart tissues as well as skeletal muscle tissues, from human stem cells. Recently, a team of researchers, at the University of Toronto, has developed an innovative biocompatible polymer scaffold that enables sheets of heart cells to stick together like Velcro.
When it comes to lab-grown heart cells, a common problem is that these cells often do not resemble the kind found inside our body. Naturally-developed heart cells require protein scaffolding and support cells for proper functioning. By contrast, artifical cardiac muscle cells usually lack these supports, and are consequently weaker and more amorphous. Led by Milica Radisic, the team has built two-dimensional honeycomb-shaped meshes of protein scaffolds that closely mimic the body’s natural environment. Speaking about the project, Radisic said:
One of the main advantages is the ease of use. We can build larger tissue structures immediately before they are needed, and disassemble them just as easily. I don’t know of any other technique that gives this ability.
In the study, recently published in the Science Advances journal, Radisic and her colleagues have used a highly-specialized polymer called POMaC, or poly(octamethylene maleate (anhydride) citrate), to construct a flexible 2D mesh for cells and tissues to grow around. Possessing a slightly asymmetrical honeycomb shape, the mesh provides a framework, around which the cells arrange themselves in a linear alignment. Furthermore, two sheets of heart cells are held together by means of specially-engineered T-shaped posts that act like tiny hooks, twisting through the holes in the mesh and snapping them together into place, like Velcro. Applying electric current to the set-up actually causes the heart cells to contract together, while also bending the polymer supports in the process. Radisic added:
As soon as you click them together, they start beating. And when we apply electrical field stimulation, we see that they beat in synchrony.
Using the technology, the scientists have successfully created two and even three-sheet-thick scaffolds, in a number of different configurations. Unlike similar breakthroughs, however, the incredibly organic behavior of the polymer framework actually makes the heart cells stronger and more robust. Radisic believes, the technology could one day be used to create artificial tissue for easier and safer cardiac repair. Being fully biodegradable, the scaffold would take only a few months to disintegrate and get absorbed by the body. Radisic explained:
If you had these little building blocks, you could build the tissue right at the surgery time to be whatever size that you require.
What is more, the technology can be used to create layered scaffolds that imitate other types of tissues, such as the kind found in liver as well as lungs. In addition to drug testing, it could help scientists acquire in-depth information about specific cell responses in a realistic environment. The researchers are looking for ways to implant the system inside the human body and check its efficiency in performing the said tasks. The team said:
We use three different cell types in this paper; cardiomyocytes, fibroblasts and endothelial cells, but conceptually there is really no limitation.. You could take middle layer out, to see what the cells look like. Then you could apply a molecule that will cause differentiation or proliferation or whatever you want, to just that layer. Then you could put it back into the tissue, to see how it interacts with the remaining layers.