Phenotypic analysis of conditionally immortalized cells isolated from the BPK model of ARPKD

To study the pathophysiology of autosomal recessive polycystic kidney disea se (ARPKD), we sought to develop conditionally immortalized control and cys tic murine collecting tubule (CT) cell lines. CT cells were isolated from i ntercross breedings between BPK mice (bpk(+/-)), a murine model of ARPKD, a nd the Immorto mice (H-2K(b)- ts-A58(+/+)). Second-generation outbred offsp ring (BPK x Immorto) homozygous for the BPK mutation (bpk(-/-); Im(+/+/-); cystic BPK/H-2K(b)-ts-A58), were phenotypically indistinguishable from inbr ed cystic BPK animals (bpk(-/-)). Cystic BPK/H-2K(b)-ts-A58 mice developed biliary ductal ectasia and massively enlarged kidneys, leading to renal fai lure and death by postnatal day 24. Principal cells (PC) were isolated from outbred cystic and noncystic BPK/H-2K(b)-ts-A58 littermates at specific de velopmental stages. Epithelial monolayers were under nonpermissive conditio ns for markers of epithelial cell polarity and PC function. Cystic and nonc ystic cells displayed several properties characteristic of PCs in vivo, inc luding amiloride-sensitive sodium transport and aquaporin 2 expression. Cys tic cells exhibited apical epidermal growth factor receptor (EGFR) mislocal ization but normal expression of ZO-1 and E-cadherin. Hence, these cell lin es retain the requisite characteristics of PCs, and cystic BPK/H-2K(b)-ts-A 58 PCs retained the abnormal EGFR membrane expression characteristic of ARP KD. These cell lines represent important new reagents for studying the path ogenesis of ARPKD.