Transplanted stem cells used to grow fully functional lungs in mice

Illustration of a human lung

According to organ donation statistics from the Health Resources & Services Administration, over 113,000 men, women, and children are on the national transplant waiting list as of July 2019. Another person is added to the waiting list every 10 minutes and 20 people die each day waiting for a transplant.

As these statistics highlight, there is a tremendous need for obtaining viable organs for people that are in need of a transplant. It is because of this, that scientists and researchers are exploring ways of using stem cells to potentially grow fully functional organs.

Dr. Hiromitsu Nakauchi, Stanford University

In a CIRM-supported study, Dr. Hiromitsu Nakauchi at Stanford University, in collaboration with Dr. Wellington Cardoso at Columbia University, were able to grow fully functional lungs in mouse embryos using transplanted stem cells. The full study, published in Nature Medicine, suggests that it may be possible to grow human lungs in animals and use them for patients in dire need of transplants or to study new lung treatments.

In the study, the researchers took stem cells and implanted them into modified mouse embryos that either lacked the stem cells necessary to form a lung or were not able to produce enough cells to make a lung. It was found that the implanted stem cells formed fully functional lungs that allowed the mice to live well into adulthood. Additionally, there were no signs of the mouse’s body rejecting the lung tissue composed of donor stem cells.

In a press release, Dr. Cardoso expressed optimism for the study and the potential the results hold:

“Millions of people worldwide who suffer from incurable lung diseases die without treatment due to the limited supply of donor lungs for transplantation. Our study shows that it may eventually be possible to develop new strategies for generating human lungs in animals for transplantation as an alternative to waiting for donor lungs.”

Stanford and University of Tokyo researchers crack the code for blood stem cells

Blood stem cells grown in lab

Blood stem cells offer promise for a variety of immune and blood related disorders such as sickle cell disease and leukemia. Like other stem cells, blood stem cells have the ability to generate additional blood stem cells in a process called self-renewal. Additionally, they are able to generate blood cells in a process called differentiation. These newly generated blood cells have the potential to be utilized for transplantations and gene therapies.

However, two limitations have hindered the progress made in this field. One problem relates to the amount of blood stem cells needed to make a potential transplantation or gene therapy viable. Unfortunately, it has been challenging to isolate and grow blood stem cells in large quantity needed for these approaches. A part of this reason relates to getting the blood stem cells to self-renew rather than differentiate.

The second problem involves the existing blood stem cells in the patient’s body prior to transplantation. In order for the procedure to work, the patient’s own blood stem cells must be eliminated to make space for the transplanted blood stem cells. This is done through a process known as conditioning, which typically involves chemotherapy and/or radiation. Unfortunately, chemotherapy and radiation can cause life-threatening side effects due to its toxicity, particularly in pediatric patients, such as growth retardation, infertility and secondary cancer in later life. Very sick or elderly patients are unable to tolerate this conditioning process, making them ineligible for transplants.

A CIRM funded study by a team at Stanford and the University of Tokyo has unlocked the code related to the generation of blood stem cells.

The collaborative team was able to modify the components used to grow blood stem cells. By making these modifications, which effects the growth and physical conditions of blood stem cells, the researchers have shown for the first time that it’s possible to get blood stem cells from mice to renew themselves hundreds or even thousands of times within a period of just 28 days. 

Furthermore, the team showed that when they transplanted the newly grown cells into mice that had not undergone conditioning, the donor cells had engrafted and remained functional.

The team also found that gene editing technology such as CRISPR could be used while growing an adequate supply of blood stem cells for transplantation. This opens the possibility of obtaining a patient’s own blood stem cells, correcting the problematic gene, and reintroducing these back to the patient.

The complete study was published in Nature.

In a news release, Dr. Hiromitsu Nakauchi, a senior author of the study, is quoted as saying,

“For 50 years, researchers from laboratories around the world have been seeking ways to grow these cells to large numbers. Now we’ve identified a set of conditions that allows these cells to expand in number as much as 900-fold in just one month. We believe this approach could transform how [blood] stem cell transplants and gene therapy are performed in humans.”