The diaphragm is a parachute-shaped muscle that separates the thoracic cavity from the abdominopelvic cavity and facilitates breathing. Contraction of the diaphragm increases the volume of the lungs, thus dropping the pressure in the lungs below the pressure of the surrounding air and causing air to rush into the lungs (inhalation). Relaxation of the diaphragm decreases the volume of the lungs and increases the pressure in the lungs so that it exceeds the pressure of the air, and air leaves the lungs (exhalation). The diaphragm is also important for swallowing. One in 2,500 babies are born with malformations or perforations in their diaphragms, and this condition is usually fatal.
The usual treatment for this condition involves the construction of an artificial patch that properly covers the lesion, but has no ability to grow with the infant and is not composed of contractile tissue. Therefore, it does not assist in contraction of the diaphragm to assist in breathing.
A new study might change the prospects for these newborn babies. Tissue engineering teams from laboratories in Sweden, Russia and the United States have successfully grown new diaphragm tissue in rats by applying a mixture of stem cells embedded in a 3D scaffold made from donated diaphragm tissue. Transplantation of this stem cell/diaphragm matrix concoction into rats allowed the animals to regrow new diaphragm tissue that possessed the same biological characteristics as diaphragm muscle.
The techniques designed by this study might provide the means for repairing defective diaphragms or even hearts.
Doris Taylor, who serves as the director of regenerative medicine research at the Texas Heart Institute and participated in this revolutionary study, said: “So far, attempts to grow and transplant such new tissues have been conducted in the relatively simple organs of the bladder, windpipe and esophagus. The diaphragm, with its need for constant muscle contraction and relaxation puts complex demands on any 3D scaffold. Until now, no one knew whether it would be possible to engineer.”
Paolo Macchiarini, the director of the Advanced Center for Regenerative Medicine and senior scientist at Karolinska Institutet, who also participated in this study, said: “This bioengineered muscle tissue is a truly exciting step in our journey towards regenerating whole and complex organs. You can see the muscle contracting and doing its job as well as any naturally grown tissue.”
To make their tissue engineered diaphragms, the team used diaphragm tissue that had been taken from donor rats. They stripped these diaphragms of all their cells, but maintained all the connective tissue. This removed anything in these diaphragms that might cause the immune systems of recipient animals to reject the implanted tissue, while at the same time keeping all the things that give the diaphragm its shape and form. In the laboratory, the decellularized diaphragms had lost all their elasticity. However, once these diaphragm matrices were seeded with bone marrow-derived stem cells and transplanted into recipient laboratory animals, the diaphragm scaffolds began to function as well as normal, undamaged diaphragms.
If this new technique can be successfully adapted to human patients, it could replace the damaged diaphragm tissue of the patient with tissue that would constantly contract and grow with the child. Additionally, the diaphragm could be repaired by utilizing a child’s own stem cells. As a bonus, this technique might also provide a new way to
Next, the team must test this technique on larger animals before it can be tested in a human clinical trial.
The study was published in the journal Biomaterials.