The only treatment for patients who have suffered from irreparable damage to internal organs or body tissue is donor organs or synthetic implants. But, these are quite often rejected. Implants based on autologous cells (cells obtained from the same individual) are more likely to be accepted but, these cells require a compatible structural framework in order to grow. Researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart, in collaboration with the university hospital in Tübingen and the University of California, Los Angeles (UCLA), are on a project to develop suitable substrates.

They have come up with cell-free substrates, known as scaffolds, containing proteins to which autologous cells can bind and grow after implantation. The main process involved in creating this would be electrospinning, in which an electric charge is used to spin synthetic and biodegradable polymers such as polylactides, into fibres. A three-dimensional non-woven fabric is then created using these fibres.

During electrospinning, proteins are added to the polymeric material and become incorporated as hair-thin fibres. This material now serves as a substrate to which the patient’s own cells will bind after it has been implanted. Dr. Svenja Hinderer, one of the research scientists working on this project at Fraunhofer IGB in Stuttgart, explained that each type of protein attracts specific cells, which adhere to the scaffold and grow there. By selecting the appropriate protein, heart tissue can be built or other damaged organs regenerated.

The substrate is spun into a fine sheet. Required sizes can be cut out and used. For example, to repair a damaged heart muscle, a scaffold of the same size as the damaged area is placed like a blanket over the muscular tissue. The polymeric fibers gradually degrade in the body over a period of 48 months. During this time, the cells bind to the proteins and find an environment that is favourable for their growth. They construct their own matrix and restore the functions of the original tissue.

The researchers will be presenting samples of the polymeric scaffolds at the Medtec expo in Stuttgart from April 21 to 23, in the joint Fraunhofer booth.

Advantages of the new and unique substrate

• The results of initial laboratory experiments and bioreactor tests turned out positive. Cells which are difficult to culture in-vitro, like Esophageal and tracheal cells, are capable of binding to decorin protein fibers in the substrate and grow. Another protein — the stromal-cell derived growth factor SDF-1 — binds with progenitor cells, a special type of stem cell necessary for constructing heart valves and for regenerating heart muscle cells after an infarction. The implants fabricated using electrospinning have demonstrated the same mechanical and structural properties as a normal heart valve. Next, they are to be tested in animal models.
• The substrate is a rapidly implementable alternative to conventional heart valve replacements and the IGB team is working to bring it to the market.
• The hybrid materials composed of polymeric and protein fibers can be produced and stored in large quantities.
• Cell-free implants are classified as medical devices and not as novel therapeutic drugs, which means less time waiting for approval but, the process of obtaining approval for medical devices that are populated with human cells prior to implantation is still very long and expensive.

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