RNA Therapy Reverses Lung Scarring by Reactivating Telomerase in Human Tissue

Pulmonary fibrosis (PF) is a progressive, fatal lung disease with a median survival of only 4–6 years after diagnosis. Current FDA-approved drugs—pirfenidone and nintedanib—slow progression but cannot reverse or cure the disease. Telomere attrition is now recognized as a central driver of PF, particularly in alveolar type II (ATII) pneumocytes, which are stem-like cells critical for lung repair. Shortened telomeres trigger DNA damage responses, cellular senescence, and secretion of pro-fibrotic signals, fueling the disease cycle. This study asked whether delivering hTERT transiently via modified mRNA could break that cycle safely.

The team in vitro transcribed hTERT mRNA using modified nucleosides (modRNA) to reduce innate immune recognition. In MRC-5 fibroblasts and, crucially, in primary human ATII cells from healthy donors, modRNA hTERT restored telomerase activity in a dose-dependent manner. Cell proliferation increased, γH2AX-marked DNA damage foci decreased, and telomere length measurably extended. Immune activation, assessed by interferon and cytokine profiling, was detectable only at the highest dose tested and normalized within 48 hours, suggesting an acceptable safety window for a transient therapeutic approach.

To extend the expression duration—potentially beneficial for a chronic disease—the authors also generated circularized, exonuclease-resistant circular RNA (circRNA) encoding hTERT. This format sustained telomerase activity longer than linear modRNA, demonstrating that the expression profile can be tuned for clinical need without resorting to viral vectors or permanent genomic integration.

The most clinically compelling data came from organotypic 3D precision-cut lung slices (PCLS) prepared from lungs of end-stage PF patients (diagnosed with usual interstitial pneumonia pattern). A single treatment with modRNA hTERT significantly lowered senescence-associated β-galactosidase activity, reduced pro-inflammatory cytokines IL-6 and IL-8, and markedly decreased TGF-β and COL1A1—the master fibrosis mediator and a primary extracellular matrix component, respectively. The circRNA hTERT produced comparable anti-fibrotic effects, validating both formats in human diseased tissue.

These findings position RNA-based hTERT therapy as a safer alternative to AAV-mediated gene therapy, which carries risks of constitutive TERT overexpression and potential tumorigenesis. The transient, dose-controllable nature of modRNA limits oncogenic risk while still achieving meaningful telomere maintenance. Remaining hurdles include optimizing pulmonary delivery (inhaled lipid nanoparticles are a likely route), determining dosing frequency in vivo, and confirming safety in longer-term animal models before human trials.