CFTR dysfunction in smooth muscle drives TGFβ dependent airway hyperreactivity.

Area of Science:

• Pulmonary Medicine
• Cell Biology
• Genetics

Background:

• Cystic Fibrosis (CF) involves disrupted ion transport, but the cause of airway symptoms like airway hyperreactivity (AHR) and increased airway smooth muscle (ASM) volume remains unclear.
• Transforming Growth Factor beta 1 (TGFβ) is a known genetic modifier of CF lung disease and influences ASM function.
• Previous studies showed CF mice exhibit increased AHR, goblet cell hyperplasia, and ASM hypertrophy after TGFβ exposure, but the specific role of CFTR loss in ASM was unknown.

Purpose of the Study:

• To investigate the direct contribution of CFTR loss in ASM to CF lung disease.
• To determine if TGFβ-induced AHR and lung pathology in CF are mediated by CFTR dysfunction specifically within ASM.

Main Methods:

• Utilized mice with smooth muscle-specific CFTR loss (Cftr^fl/fl; SM-Cre).
• Exposed these mice to pulmonary TGFβ.
• Assessed lung mechanics, Western blot, and pulmonary histology to evaluate the impact on lung pathology and physiology.

Main Results:

• Mice with smooth muscle-specific CFTR loss (Cftr^fl/fl; SM-Cre) exposed to TGFβ showed increased methacholine-induced AHR compared to controls.
• However, these mice did not exhibit increased inflammation, ASM area, or goblet cell hyperplasia post-TGFβ exposure.

Conclusions:

• Demonstrated a direct role for ASM in CF airway obstruction, mediated by TGFβ.
• Highlighted the importance of considering non-epithelial tissue dysfunction, particularly ASM, in developing CF therapeutics, including genetic therapies.