Scientists discover why deadly lung scarring from IPF refuses to heal

Idiopathic pulmonary fibrosis slowly turns the lungs stiff and scarred, but researchers may have found why the damage keeps building. Their work points to a survival signal inside key cells, and to a treatment approach that could help the lungs recover.

Every breath depends on millions of tiny air sacs inside the lungs working smoothly. In people with idiopathic pulmonary fibrosis, or IPF, that delicate system slowly breaks down. Healthy lung tissue becomes stiff and scarred. Oxygen struggles to move into the bloodstream. Even simple activities can leave patients exhausted and gasping for air.

Doctors have long known that scar-forming cells called fibroblasts play a major role in the disease. These cells normally help repair injured tissue. Once healing is complete, many fibroblasts die through a natural process called apoptosis, which acts like the body’s cleanup system. In pulmonary fibrosis, that process fails.

A new study from researchers at National Jewish Health and collaborating institutions may finally explain why. The research, published in Nature Communications, found that a protein called BCL-2 helps harmful fibroblasts avoid death, allowing them to build up inside the lungs and drive persistent scarring.

The findings also revealed something hopeful. When scientists blocked BCL-2 with a targeted therapy, they reduced scarring, improved oxygen levels and partially restored healthy lung structure in preclinical models.

“Our findings show that BCL-2 plays a central role in allowing harmful fibroblasts to survive and sustain fibrosis,” said David Riches, PhD, senior author of the study and head of the Division of Cell Biology at National Jewish Health. “By therapeutically inhibiting this pathway, we were able to promote the clearance of these cells and restore key aspects of normal lung architecture. This opens an important new avenue for potential treatment strategies.”

Pulmonary fibrosis develops after repeated injury to the cells lining the lungs’ air sacs. In healthy repair, fibroblasts briefly activate to rebuild damaged tissue. Afterward, many disappear through apoptosis.

In IPF, fibroblasts refuse to die. They continue producing collagen and other scar-forming material long after the original injury ends. Over time, thick scar tissue replaces flexible lung tissue.

Researchers focused on BCL-2 because it acts as an anti-apoptotic protein. In simple terms, it blocks signals that normally tell damaged or unneeded cells to self-destruct.

Earlier studies hinted that BCL-2 levels rise in fibrotic lungs, but scientists did not fully understand how the protein affected disease progression. To investigate, researchers engineered mice so BCL-2 could activate specifically inside fibroblasts.

When the protein switched on, fibroblasts became highly resistant to cell death. Even when exposed to strong death signals, these cells survived.

To trigger fibrosis, researchers exposed mice to bleomycin, a chemical commonly used to model lung scarring. In normal mice, fibrosis peaked after a few weeks and gradually resolved as fibroblasts died off.

The genetically modified mice showed a completely different pattern.

At first, both groups developed similar levels of fibrosis. But over time, healthy mice began recovering. Fibroblast numbers dropped. Collagen levels decreased. Lung tissue slowly repaired itself.

In the BCL-2 mice, fibroblasts remained elevated for up to 12 weeks. The scarring persisted. Lung structure became distorted.

Microscopic analysis showed collapsed air sacs, thickened tissue and cyst-like damage. Researchers also found abnormal epithelial cells accumulating in scarred regions, similar to patterns seen in human IPF.

The team measured collagen using hydroxyproline assays. By six weeks, collagen levels had dropped significantly in healthy mice, signaling recovery. In the BCL-2 mice, collagen stayed high.

These findings showed that BCL-2 alone was enough to block healing and sustain fibrosis.

The study uncovered another important clue. The surviving fibroblasts did not simply remain active, they became senescent.

Senescence refers to a state of cellular aging in which cells stop dividing but continue releasing inflammatory and damaging molecules. Senescent cells can worsen disease by constantly signaling nearby tissue.

Researchers performed RNA sequencing on fibroblasts from injured lungs. In healthy mice, fibroblasts eventually shifted toward repair-related programs tied to wound healing and tissue remodeling.

The BCL-2 fibroblasts never made that transition.

Instead, they remained locked in a pro-fibrotic state. Genes linked to senescence became highly active, including markers such as p16 and p21. Additional testing confirmed elevated levels of senescence-associated beta-galactosidase, another hallmark of aged cells.

“This study provides compelling evidence that resistance to cell death and the development of senescence are tightly linked in driving persistent fibrosis,” said Elizabeth Redente, PhD, professor of medicine at National Jewish Health and first author of the study. “Targeting BCL-2 not only addresses fibroblast survival but also helps disrupt the underlying biology that sustains disease progression.”

To confirm that the same process occurs in people, researchers analyzed lung tissue from patients with pulmonary fibrosis using spatial transcriptomics, a method that maps gene activity inside tissue samples.

The results closely matched the mouse findings.

Fibrotic regions in human lungs contained fibroblasts expressing high levels of BCL-2. These same cells also carried strong senescence signatures.

Compared to neighboring cells, BCL-2-positive fibroblasts showed greater activity of genes tied to fibrosis, inflammation and cellular aging. Protein staining further confirmed elevated p16, p21 and beta-galactosidase in diseased tissue.

Healthy lungs showed very little of these markers.

This link between mouse models and human tissue strengthened the study’s relevance for future therapies.

The researchers then tested whether inhibiting BCL-2 could reverse established fibrosis.

They used a drug called ABT-199, also known as Venetoclax. The U.S. Food and Drug Administration already approves the medication for certain blood cancers because it blocks BCL-2 activity.

Treatment began after fibrosis was already well established.

The results were striking.

Fibroblast numbers dropped sharply. Collagen levels decreased. Lung oxygenation improved. Imaging scans showed less non-aerated lung tissue, meaning more areas could exchange oxygen properly.

Microscopic examination revealed partial restoration of healthy lung structure. Scar tissue lessened. Air sacs reopened. Senescence markers also declined significantly after treatment.

Importantly, the therapy appeared to specifically target harmful fibroblasts while sparing other support cells.

The findings suggest that fibrosis may not be as irreversible as once believed.

Idiopathic pulmonary fibrosis remains one of the most devastating lung diseases. Most patients survive only three to five years after diagnosis. Current treatments may slow progression but cannot fully reverse scarring.

This study offers a new approach by targeting the very cells that refuse to die.

Instead of only slowing fibrosis, BCL-2 inhibition may help the lungs clear harmful fibroblasts naturally. That could allow normal repair processes to restart.

Researchers caution that more studies are needed before the therapy can be widely tested in people with IPF. Scientists still need to confirm long-term safety and determine which patients may benefit most.

Still, the work marks a major step forward in understanding why fibrosis persists and how it might one day be reversed.

For patients living with a disease that steadily steals breath and energy, that possibility carries enormous weight.

This research could reshape how scientists approach pulmonary fibrosis treatment. Current therapies mainly focus on slowing lung damage. By targeting BCL-2, future treatments may actively remove harmful fibroblasts and help damaged lungs heal more effectively.

The findings also deepen understanding of how senescence contributes to chronic disease. Since senescent cells appear in many age-related conditions, this work may influence research beyond pulmonary fibrosis, including studies involving heart disease, kidney fibrosis and chronic inflammatory disorders.

Because Venetoclax already exists as an approved drug for blood cancers, researchers may be able to move more quickly toward clinical testing in fibrosis patients. That could shorten the timeline for translating laboratory discoveries into human therapies.

Most importantly, the study provides new hope for people facing a disease with limited treatment options. It suggests that even advanced scarring may not be permanent if scientists can remove the cells driving the damage.

Research findings are available online in the journal Nature Communications.

The original story "Scientists discover why deadly lung scarring from IPF refuses to heal" is published in The Brighter Side of News.

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