We’ve all suffered wounds before. For lesser wounds, scrapes and scratches, our bodies will manage to heal in days or weeks. Healing is done in stages. The body’s first response is inflammation; the blood vessels contract to promote clotting, the area warms up, and your immune system mounts an assault with neutrophils and macrophages against the insult.
After inflammation, the tissue is rebuilt during the proliferation phase. Collagen and extracellular matrix are formed to promote angiogenesis, the reconstruction of blood vessels. The tissue reddens, indicative of healthy granulation; dark granulation is a result of poor perfusion or infection. The final stage is maturation. The collagen in the wound is remodeled and the cellular activity reduces to its basal functions. The blood vessels regress and the pink color fades.
The real challenge comes in trying to regrow appendages. Regenerative medicine focuses on tissue engineering and molecular biology to restore function to damaged cells, organs, and biological systems. By studying lizards, scientists have taken steps on determining the genes involved in tail regeneration. Theses clues may be important in helping humans regenerate limbs. The process takes 60 days for the lizard to regrow a fully functioning tail. There are also other challenges to overcome, like growing bones.
Ears, on the other hand, do not have bones; the exterior is cartilaginous tissue while the bones are housed in the skull. Loss of an ear can occur as a result of many circumstances: e.g., accidents, disease, or basal cell carcinomas. Prosthetic ears require a fastening system attached to the head to hold an ear in position, but a common complaint is that they don’t look or feel natural; they also have a tendency to wear out. Researchers are now focusing on growing ears from a patient’s own cartilage, making the new tissue both biocompatible and indistinguishable from surrounding tissue. The tissue grown in this manner uses a titanium support embedded in the ear. Researchers at the NTNU and SINTEF are now trying to develop a cell matrix to promote tissue growth without a support system.
Alginate, or alginic acid, is an anionic polysaccharide derived from brown algae and seaweed. After isolation, it forms a viscous gum with water. The polysaccharides are long chains of sugar molecules; what is unique about alginate is that the sugar rings also bear acidic side chains that are ionizable, and able to form salt bridges. When mixed with calcium, the alginate hydrogel is water-insoluble.
Alginate is biocompatible and has found uses as hemostatic wound dressings, drug delivery systems, protein delivery, and a cell culture medium, which is strategic for tissue regeneration. The ideal cell growth conditions are inside our body, but alginate can serve as a surrogate. The alginate can form a workable hydrogel that is ideal for 3D printing. The ear can be reconstructed as an alginate-cellulose matrix that is seeded with cells from the host. They regrown ear can then be transplanted to the host.
The matrix attenuates the immune response to increase the successful transplantation of cells.
With clever use of cell biology, this form of regenerative medicine is not exclusive to growing ears. The researchers are trying to expand this to other tissues, tendons, and organs. In an example given by the NTNU and SINTEF, worn cartilage in the knee can be transplanted from another part of the body to repair the damage that makes it difficult to move. The researchers also discuss the potential for growing new organs. Due to shortages of organ donors, lab-grown organs may soon become a necessity. The nose is another cartilaginous structure that can benefit from this technology. Many of these treatments would be welcomed not only by the general population but also military personnel that engaged in combat and were wounded. Reconstructive surgeries may soon be rebranded as regenerative surgeries
Top image: Seaweed texture (CC BY-NC-ND 2.0)