New York, March 25 (IANS): Scientists have grown the first 3D mini lungs from stem cells. The 3D structures bear greater similarity to the human lung than previously made 2D structures, researchers said.

The scientists succeeded in growing structures resembling both the large proximal airways and the small distal airways, according to the study published in eLife.

"We expected different cells types to form, but their organisation into structures resembling human airways surprised us and is a very exciting result," said lead author Jason Spence from the University of Michigan.

The scientists used embryonic stem cells, proteins involved in lung development, growth factors and protein mixture in a Petri dish.

"First, we added protein ActivinA to stem cells and left for four days. A type of tissue called endoderm formed. Endoderm is found in early embryos and gives rise to the lung, liver and several other internal organs.

"Then we added Noggin, another protein, and a transforming growth factor. It was left for another four days.

"The endoderm is induced to form 3D spherical structures called the foregut spheroids," the researchers detailed the method of growing the mini lungs.

The next challenge was to make these structures expand and develop into lung tissue by exposing the cells to proteins involved in lung development.

"The lung organoids are self-organising, and do not require further manipulation to generate 3-dimensional tissues," Spence explained.

However, since these structures were developed in a dish, they are lacking several components of the native lung, including the blood vessels.

"We hope to build on our initial findings to build increasingly complex mini-lungs by adding these components, eventually forming tiny organs able to perform functions related to breathing," Spence said.