A novel gene therapy for Autosomal Recessive Polycystic Kidney Disease based on CFTR

Autosomal recessive polycystic kidney disease (ARPKD) is caused by mutations in the PKHD1 gene, which encodes a large 4,074-amino acid protein, fibrocystin/polyductin (FPC. The disease is already apparent in utero, with massively enlarged, echogenic kidneys and oligohydramnios occurring in the fetus. The mortality among newborns is ~30%. Those who survive have serious liver and kidney disease. In the ARPKD-affected liver, dilation of the biliary ducts caused by abnormalities in the ductal plate lead to grossly enlarged and malformed bile ducts and portal hypertension. At present, there is no treatment that targets this disease specifically. Given that the liver disease in ARPKD is associated with cysts derived from abnormal bile ducts, the goal here was to develop a gene therapy vector for ARPKD that targets the abnormal bile ducts based on CFTR. Our previously published work has shown that in FPC-null (ARPKD) cholangiocytes, steady-state levels of CFTR are dramatically lower than in wild-type (WT) mice, suggesting that reduced CFTR contributes to the pathophysiology associated with ARPKD. Indeed, we showed that treating ARPKD mice with the CFTR modulator, VX-809 reduced cyst size. To delineate the effect of CFTR from that of the CFTR modulator, VX-809, that could have off-target effects, we injected mice with AAV1- Δ27-264-CFTR. To establish a gene therapy for ARPKD, we studied transduction of the ARPKD liver with Δ27-264-CFTR a truncated form of CFTR known to affect endogenous CFTR via a process called transcomplementation(2). AAV1- Δ27-264-CFTR is a mini gene that binds directly to endogenous CFTR and increases its trafficking and processing. We injected 1-month-old, Pkhd1 del3-4/del3-4 mice intraperitoneally with 2 x 10 12 particles/kg of AAV1 containing either a GFP vector or a truncated CFTR vector, Δ27-264-CFTR, or left them untreated. Two months after treatment, the cyst area and size in the liver were lower and proliferation reduced in the CFTR vector-treated mice compared to the mice receiving the GFP vector. We detected vector genomes and mRNA expression only in mice receiving the corresponding CFTR or GFP vector. We observed abundant GFP immunofluorescence in the cholangiocytes of the cysts and also saw expression of GFP and CFTR proteins above background levels in the correspondingly treated mice. CFTR immunofluorescence was predominately apically located in the ARPKD cholangiocytes, but after CFTR vector installation, it increased in the basolateral membrane. We stained mouse livers with Maackia amurensis lectin (MAL) or Sambucus nigra lectin (SNA), specific for α2,3- and α2,6-N-linked sialic acid, respectively, to detect the presence of sialic acid moieties contributing to AAV1 binding. Although immunofluorescent SNA was detected in the wild-type bile ducts, MAL 1 was not. MAL immunofluorescence was present in remarkably high levels on the apical surfaces of the cysts in cholangiocytes, offering an excellent target for AAV1 gene therapy. Conclusion: Importantly, increasing CFTR using AAV1- Δ27-264-CFTR rescues the ARPKD liver phenotype. Thus, a gene therapy using an AAV1-based vector containing a truncated CFTR could be therapeutic in ARPKD. DK125272 to LC This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.