Rapid cell reprogramming creates lung-like cells to combat COPD

The researchers successfully generated lung cells resembling alveolar epithelial type 2 (AT2) cells from mouse embryonic fibroblasts – without using stem cell technology. This new direct reprogramming approach achieved results in just 7 to 10 days – a major improvement compared to the one-month timeline of traditional stem cell-based methods.

The findings, published in npj Regenerative Medicine, suggest that treating severe respiratory conditions like interstitial pneumonia and chronic obstructive pulmonary disease (COPD), is now a possibility.

The role of AT2 cells in lung health

AT2 cells play a crucial role in lung function by producing surfactant and serve as progenitor cells that enable alveolar repair. In patients suffering from lung diseases, such as interstitial pneumonia, these cells are often lost or damaged, making their regeneration a key focus for developing new therapies.

Moving beyond stem cells

“The advent of the induced pluripotent stem cell (iPSC) technology in 2006 has enabled the generation of AT2 cells in approximately one month, but this method is costly and carries risks of tumour formation and immune rejection,” said Professor Makoto Ishii of Nagoya University Graduate School of Medicine. “To overcome these disadvantages, we focused on direct reprogramming instead. The direct reprogramming approach produces AT2-like cells in just 7 to 10 days, with lower tumour risk and potential for autologous use.”

Unlocking the reprogramming code

Professor Ishii led the research in collaboration with Professor Koichi Fukunaga, Assistant Professor Takanori Asakura and Joint Researcher Atsuho Morita from Keio University School of Medicine. The team aimed to directly reprogram fibroblasts into AT2-like cells – something that has never been achieved in mice.

Starting with 14 genes known to be involved in lung development, they evaluated various combinations  to see which could activate surfactant protein-C (Sftpc) – a marker specific to AT2 cells. They identified a set of  four genes – Nkx2-1, Foxa1, Foxa2 and Gata6 – that proved to be the most effective.

The researchers introduced these genes into a 3D culture of mouse embryonic fibroblasts engineered to produce green fluorescent protein (GFP) when the Sftpc gene was activated. Within 7 to 10 days, about 4 percent of the cells became Sftpc/GFP-positive, showing successful reprogramming. These cells were named induced pulmonary epithelial-like cells (iPULs).

Mimicking native lung cells

The researchers used flow cytometry to isolate GFP-positive iPULs for closer examination. The cells exhibited lamellar body-like structures – distinctive features of AT2 cells. A transcriptomic analysis confirmed that their gene expression profiles closely resembled those of natural AT2 cells.

To test their function in vivo, the iPULs were transplanted into the lungs of mice with interstitial pneumonia. After 42 days, the cells had successfully engrafted in the alveolar region. Some of them had even differentiated into alveolar epithelial type 1 (AT1)-like cells – which are essential for gas exchange and tissue repair.

Toward human applications

The creation of AT2-like lung cells from fibroblasts marks a pivotal moment in regenerative medicine. Having demonstrated the technique in mice, the researchers are now moving forward to translate this approach to human cells.

“In this study, we succeeded in direct reprogramming of fibroblasts into AT2-like cells in mice. We now aim to explore the application of this technology to human cells, with the ultimate goal of developing a safe regenerative therapy using a patient’s own fibroblasts,” said Ishii.