Enteric nervous system degeneration in human and murine CLN3 disease, is ameliorated by gene therapy in mice

Severe gastrointestinal (GI) symptoms occur in people with CLN3 disease, a neurodegenerative disorder. If left untreated these GI symptoms compromise life quality and may contribute to death. We hypothesized GI symptoms in CLN3 disease are at least partially due to neurodegeneration in the enteric nervous system (ENS), the master regulator of bowel function. We examined the integrity of the ENS in human CLN3 autopsy small bowel and colon, and in CLN3 deficient (Cln3Δex7/8) mice. We performed detailed immunohistological analyses of enteric neurons and glia and assessed bowel transit times at multiple disease stages. We then tested the therapeutic potential of neonatal intravenous gene therapy (AAV9.hCLN3) to prevent bowel phenotypes in Cln3Δex7/8 mice. Human CLN3 bowel displayed a profound loss of enteric neurons and their neurites, with pathological effects upon enteric glia. Cln3Δex7/8 mice had normal appearing ENS at 1 month of age, but then experienced progressive loss of both enteric neurons and glia accompanied by marked bowel distention, resembling the human CLN3 phenotype. Degenerative changes in Cln3Δex7/8 mouse enteric neurons and glia were largely prevented by systemic neonatal delivery of AAV9.hCLN3 gene therapy, preventing bowel distention at disease endstage. Our findings demonstrate that CLN3 deficiency profoundly damages enteric neurons and glia in both murine and human CLN3 disease, contributing to GI dysfunction. This study provides preclinical evidence that systemic gene therapy may effectively treat multiple aspects of bowel pathology, expanding the therapeutic landscape beyond the CNS.