Researchers at Yale University have successfully implanted tissue-engineered lungs, cultured in vitro, into adult rats, an important first step in regenerating fully functional lung tissue that can exchange gas. The paper has been published in Science Express.
Lung tissue is difficult to regenerate because it does not generally repair or regenerate beyond the microscopic level. Currently, the only way to replace damaged adult lung tissue is to perform lung transplantation, which is highly susceptible to organ rejection and infection and achieves only 10% to 20% survival at 10 years.
The researchers took adult rat lungs and first removed their existing cellular components, preserving the extracellular matrix and hierarchical branching structures of the airways and vascular system to use later as scaffolds for the growth of new lung cells. They then cultured a combination of lung-specific cells on the extracellular matrix, using a novel bioreactor designed to mimic some aspects of the fetal lung environment.
Under the fetal-like conditions of the bioreactor, the cells repopulated the decellularized matrix with functional lung cells. When implanted into the rats for short intervals of time (45 to 120 minutes), the engineered lungs exchanged oxygen and carbon dioxide similarly to natural lungs.
“W succeeded in engineering an implantable lung in our rat model that could efficiently exchange oxygen and carbon dioxide, and could oxygenate hemoglobin in the blood,” said Laura Niklason, MD, PhD, lead author of the study and professor and vice-chair of the departments of anesthesiology and biomedical engineering at Yale. “This is an early step in the regeneration of entire lungs for larger animals and, eventually, for humans.”
The team found that the mechanical characteristics of the engineered lungs were similar to those of native tissues and, when implanted, were capable of participating in gas exchange.
While this is an important first step, the researchers maintain that a great deal more research must be done to see if fully functional lungs can be regenerated in vitro, implanted, and sustained in their functioning. According to Niklason, for this technology to be applicable to patients, years of research with adult stem cells likely will be needed to repopulate lung matrices and produce fully functional lungs.
Source: Medical News Today
