Regenerative medicine: creating a new body?

Regenerative medicine aims to repair the human body after injuries, accidents or major cancer surgery. Unfortunately, we are still not at a stage where this process can achieve optimal results for every conceivable situation. Having said that, various new methods are on the cusp of breakthrough.

Today, there are two options to promote wound healing. One option is to work with the body's own material to treat severe skin injuries over large areas and ligament injuries or to stimulate bone regeneration. In these cases, physicians take material from other parts of the body and implant it after modeling it to the wound. This essentially means two different surgeries for patients and doctors. Another concern is that taking the patient’s own cells and tissue can only be done in a limited scope as each removal always causes further damage to the body.

The second option entails foreign materials such as synthetic or natural implants, but this process also comes with some restrictions. Synthetic materials must not cause an immune reaction that could lead to a rejection of the implant. Examples of this include hydrogels to repair soft tissue injuries or ceramic implants to restore damaged bones. Both of these solutions are designed to fill the damaged area and provide a stimulating environment for cell growth and proliferation. As the body gradually replaces the implant with its own tissue and breaks the implant down, the degradation products must not elicit any harmful effects.

Natural materials refer to tissues that are sourced from dead bodies or animal carcasses and processed before implantation. Cellular components are removed from the material and purified so that only the extracellular matrix remains. It is a scaffold that is designed to support and anchor cells in the body. Once it is implanted, cells grow on it and form new tissue. However, transplantation carries a risk of transmitting allergens and pathogens.

The extracellular matrix consists of collagens, long stable protein chains that make up a large part of our body. The future of regenerative medicine depends on collagen as the most important material. The better and purer the implanted collagen, the better it is suitable for regeneration purposes. If you use collagen from biological sources, you always run the chance that extraction and processing will damage it or decrease its quality.

That’s why future regenerative medicine must focus on materials whose properties specifically promote regeneration. An example of this is "rhCollagen" by the Israeli company CollPlant. "Our proprietary technology is based on the introduction of the five human genes that are essential for the synthesis of Type I collagen into tobacco plants. It is the only commercially viable technology currently available to mass-produce true Type I human collagen," CEO Yehiel Tal explains in an interview with MEDICA-tradefair.com.

rhCollagen is identical to natural human collagen and can be genetically engineered by using plants. During the process, it remains intact and free of pathogens and allergens. Apart from wound care products that are already available on the market, CollPlant also aims to advance the development of its rhCollagen-based pipeline to be used in 3D bioprinting of tissues and organs, implants and dentistry.

However, there is still one caveat even if the raw material has been optimized. When the body heals itself, scars form or there is restricted function as today's materials do not promote the type of growth that equals the natural growth in the body. In fact, the body's own cells grow into the implants from the outside. This only creates structures of limited use such as nerve fibers or blood vessels because you cannot regulate the necessary growth inside the body.

3D bioprinting might be a solution to this problem. This process arranges cells in a carrier material such as hydrogels to promote growth inside the implant. The implant structure is carefully planned, controlled and built layer-by-layer, enabling faster and more consistent tissue colonization of the implant. This requires cells that have been extracted from the patient and cultivated beforehand, as well as a printer with a high resolution to allow for precision cell placement.

Light-guided angiogenesis is yet another approach. Prof. Aránzazu del Campo of the INM – Leibniz Institute for New Materials is an expert in this field and sat down for an interview with MEDICA-tradefair.com. "We aim to use laser light to regulate where and when blood vessels - and possibly down the road neurons - grow in implanted hydrogels," she explains. The idea behind this is to load implantable hydrogels with photoactive molecules. Once they are irradiated by laser, they release the enclosed growth factors that stimulate the growth of endothelial cells. They, in turn, form new blood vessels. In theory, these blood vessels then grow in and through the implant in a controlled manner. When it comes to organs such as the eyes or liver, it is essential that blood vessels grow in certain regions.

For large implants, this method could also ensure that cells inside the implant are adequately supplied with blood to achieve more effective colonization. Del Campo is optimistic when it comes to the next steps of this development and says: "We have shown proof of concept via in vitro studies and demonstrated that we can regulate angiogenesis with light. Animal testing has also been successful."

The future of regenerative medicine lies not just in healing damage to the body, then leaving it to its own devices and hoping for the best. It also has to anticipate the body's reactions and support it as much as possible: processes like bioprinting and light-guided angiogenesis can create implants guided by a blueprint that the body can follow.

More advanced approaches that involve growing organs in the lab using the patient's stem cells or the creation of so-called chimeras by growing human organs in animal embryos are still a long way off. Apart from ethical considerations, it is also yet unclear to what extent these types of organs would be compatible with the human body or whether and how much animal material they still contain. What’s more, growing life-size human body organs takes a long time. This makes the process unsuitable to counteract the consequences of acute injuries or illnesses.

Until such visions can materialize, we still depend on matching donor organs and tissues and on synthetic materials with the included risks and complications.