A magnified view of a CD34+ stem cell.
(photo credit: REUTERS)
Researchers at the Weizmann Institute of Science in Rehovot have suggested that embryonic stem cells could be used to repair damaged lung tissue.
Lung disease affects more than 35 million Americans alone and is the third leading cause of death in the US.
The research began with an insight. Bone marrow transplants are based on two main principles: The ability of stem cells to find their way through the bloodstream to the appropriate compartment, and the prior clearing out of the compartment to make room for the transplanted stem cells. In each organ, rather than being distributed throughout the tissue, stem cells concentrate in special “compartments” that contain all the provisions they need.
Prof. Yair Reisner of the institute’s immunology department said this understanding “suggested to us that we might be able to apply our knowledge of techniques for transplanting bone marrow stem cells to repairing lung tissue.”
The study recently appeared in the journal Nature Medicine.
Certain stem cells that normally reside in the lungs are highly similar to those in the bone marrow, the researchers realized. Reisner and his colleagues thought it might be possible to apply these principles to introducing new stem cells into the lungs. But before they could do this, they needed to find a source of lung stem cells suitable for transplanting.
This was a problem, as they are quite rare.
The group overcame this obstacle by using embryonic stem cells from the 20th to 22nd week after their creation.
The research showed that this is the ideal time frame in which to harvest the cells. Younger cells have not completed the process of differentiation, while older cells are less capable of lung regeneration.
The team then conducted a series of experiments in which they cleared the lung’s stem cell compartments with a method they had developed, and then introduced the new stem cells by injecting them into the mouse models of lung damage.
The embryonic lung stem cells managed to find their way through the blood into the lungs where they settled into the proper compartment.
By six weeks, these cells were differentiating into normal lung tissue. The damaged lungs healed in the mice, and their breathing improved significantly.
Next, Reisner intends to determine the correct dosage of drugs that would be needed to prevent rejection of the transplanted cells, which would be necessary following such a procedure.
“But our real vision, bolstered by this success,” he said, “is to create a bank of lung tissue that will be a resource for embryonic lung stem cells.”
This bank could mean that there is a ready source of cells for repairing the damage in those with severe respiratory disease.