Nine months of Lactobacillus paracasei L9 supplementation (4×10⁹ CFU/mL) reduced collagen-I deposition by 61% in aged mice with pulmonary fibrosis by blocking the JNK-HSF1 signaling pathway and decreasing HSP47 expression. The probiotic increased SCFA-producing bacteria like Blautia, boosting serum propionic acid by 97% and butyric acid by 193%, which suppressed inflammatory Th17 cells and IL-17A in lung tissue.
This gut-lung axis mechanism represents a compelling new therapeutic avenue for idiopathic pulmonary fibrosis, a devastating age-related condition with few effective treatments. The finding that systemic SCFAs can modulate pulmonary immune responses without direct lung presence suggests sophisticated inter-organ communication networks. However, the nine-month treatment duration raises questions about clinical feasibility, and translation from mouse models to human IPF remains uncertain given species differences in microbiome composition and immune responses. The specificity for collagen-I over collagen-III also warrants investigation, as both contribute to fibrotic pathology. While promising as adjuvant therapy, this represents incremental progress requiring human validation before clinical application.