Ano1 Antisense Therapy Improves Enamel Properties in Molars but not Amelogenesis in a Murine Model of Cystic Fibrosis

Cystic fibrosis (CF) is a life-shortening inherited disorder caused by mutations in the gene encoding the Cystic Fibrosis Transmembrane conductance Regulator (CFTR), a protein that controls the transport of chloride ions across cell membranes. Defects in CFTR cause thick mucus, leading to chronic infections and inflammation in multiple organs. Severe mutations, such as G542X, that completely abolish the function of CFTR present major therapeutic challenges. One potential approach is to stimulate an alternative chloride channel, ANO1, which is repressed in patients by the small regulatory molecule microRNA-9. We recently showed that an antisense oligonucleotide (ASO) designed to restore ANO1 activity (Ano1 ASO) improved respiratory and digestive functions in a CF mouse model carrying the pathogenic G542X variant. As patients with severe forms of CF often display enamel defects, we aimed to investigate the impact of Ano1 ASO on enamel of G542X CF mice. Combining multiproxy imaging approaches, our data showed that Ano1 ASO initiated at postnatal day 8 partially rescued the enamel properties in molars, which have mainly formed before the onset of treatment. However, it did not correct enamel maturation in the continuously growing incisor. In contrast to CFTR, there was no significant increase in ANO1 expression in maturation-stage ameloblasts compared to secretion ameloblasts. These findings suggest that while stimulating ANO1 cannot compensate for the absence of CFTR during enamel maturation, it enhances the mechanical properties of the erupted teeth, likely by improving salivary properties. This work identifies a potential avenue for mitigating dental complications in patients with severe CF mutations.