A novel gene therapy for ARPKD based on CFTR

Autosomal recessive polycystic kidney disease (ARPKD) is associated with cysts derived from abnormal bile ducts. We focused on targeting the cysts and show that a gene therapy for ARPKD that targets the abnormal bile ducts is feasible. We injected 1-mo-old, Pkhd1^{del3-4/del3-4} mice intraperitoneally with 2 × 10¹² particles/kg of adeno-associated virus (AAV1) containing either a GFP vector or a truncated cystic fibrosis transmembrane conductance regulator (CFTR) vector, Δ27-264-CFTR, or left them untreated. Two months after treatment, the cyst area and size in the liver were lower in the CFTR vector-treated mice than in 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 corresponding treated mice. CFTR immunofluorescence was predominantly 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 a good target for AAV gene therapy. A gene therapy using an AAV1-based vector containing a truncated CFTR could be therapeutic in ARPKD.NEW & NOTEWORTHY Autosomal recessive polycystic kidney disease (ARPKD) causes severe disease in babies in the womb. Those who survive the neonatal period face chronic kidney and liver disease throughout their life. The overall goal of our study here is to develop a gene therapy to treat ARPKD.