Loss of CA12 drive proliferation and fibrosis in type i congenital pulmonary airway malformation via promoting abnormal activation of SHH signaling

Congenital pulmonary airway malformation (CPAM), especially type I, is an uncommon developmental lung defect marked by abnormal proliferation of pseudostratified ciliated columnar epithelium (PCCE) and the presence of cystic lesions. Recent studies indicate that Sonic Hedgehog (SHH) signaling and carbonic anhydrase 12 (CA12) play essential roles in CPAM pathogenesis. This study investigates the interaction between SHH and CA12 in PCCE proliferation and fibrosis in type I CPAM. Cystic and surrounding healthy lung tissues were obtained from 10 pediatric patients with CPAM, and primary pseudostratified ciliated columnar epithelial cells were extracted. CA12 and SHH expressions were manipulated through overexpression and knockdown techniques, followed by detection of cell proliferation, cell cycle, and fibrosis. Results revealed that CA12 expression is significantly reduced, whereas SHH was overexpressed in type I CPAM cysts. CA12 overexpression inhibited PCCEC proliferation, fibrosis, and SHH signaling, as indicated by decreased Cyclin D1, Cyclin E1, and fibrosis marker (α-smooth muscle actin, Collagen I, and Collagen III) levels. Conversely, SHH knockdown suppressed proliferation and fibrosis, whereas SHH overexpression enhanced these processes. Mechanistically, CA12 modulated intracellular pH balance through transporters sodium bicarbonate cotransporter 1 (NBCn1) and monocarboxylate transporter 4 (MCT4), influencing SHH expression. Lactic acid treatment stimulated SHH signaling, increasing Gli-1, Gli-2, and fibrosis markers, and enhancing PCCEC proliferation. NBCn1 or MCT4 overexpression reversed the effects of CA12 knockdown, restoring pH balance and inhibiting SHH signaling. In conclusion, CA12 deficiency and SHH overexpression enhance PCCE proliferation and fibrosis in type I CPAM, with CA12 modulating SHH signaling by regulating intracellular acid-base equilibrium. These findings highlight CA12 and SHH as prospective therapeutic targets for CPAM management.