New therapies for polycystic kidney disease

Supervisors: Dr David Long, Professor Peter Scambler and Professor Adrian Woolf

Background: In the UK, there are over 40,000 people with kidney failure who need long-term dialysis and renal transplantation. One of the most commonest diagnosis is polycystic kidney disease (PKD)1 which causes morbidity, renal failure and death from before birth through adulthood. Many cellular processes are implicated in cyst formation including altered adhesion, planar cell polarity, dysregulated cell cycle and aberrant structure/function of the primary cilium1. The commonest form of PKD in adults is autosomal dominant (AD) PKD affecting 1 in 600 people, whilst the recessive inherited form (ARPKD, 1:50,000 births) is an important cause of renal failure during childhood with collecting duct cystogenesis in the second half of gestation1. Diverse approaches have been proposed to reduce cyst development including cyclin-dependent kinase inhibitors and supressing the vasopressin system which are undergoing trials in adults with ADPKD. However, it is unclear whether they are practical in babies and children with ARPKD; therefore there remains a need to design new therapies for this disease.

Recent studies in our laboratory have identified the hedgehog pathway as a potential target for novel ARPKD therapies. The three hedgehog ligands; Sonic (Shh), Indian (Ihh) and Desert (Dhh) predominately bind to the receptor Patched 1 (Ptch1) leading to derepression of Smoothened (Smo) which accumulates in the primary cilia leading to the activation of the Gli transcription factors2. Our previous work examined renal developmental gene expression in an in-vitro explant model replicating features of ARPKD. In this model, Ihh was the most markedly deregulated transcript and Ptch1 was modestly upregulated3. Furthermore, addition of the generic hedgehog inhibitor cyclopamine prevented cystogenesis3. These observations provide a rationale for examining and manipulating hedgehog signalling in ARPKD in-vivo; which will be the focus of this proposal. We hypothesise that inhibition of the hedgehog pathway may slow the progression of ARPKD.

Aims and methods:
The student will:

1) Undertake a detailed examination of hedgehog pathway components in two animal models of ARPKD4,5.
2) Determine if pharmacological inhibition of the hedgehog pathway alters the progression of ARPKD in-vivo.
3) Investigate whether haploinsufficiency of Ihh alters the progression of ARPKD.

The student will gain a broad experience in the following fields and techniques: understanding mechanisms of kidney developmental and cell biology; working with animal models; explant organ culture of developing kidneys; histology; expression analyses at the protein and mRNA levels (in-situ hybridisation, immunohistochemistry, western blotting and quantitative RT-PCR.

References:
1) Wilson PD. Int J Biochem Cell Biol 2004 36: 1868-1873.
2) Winyard P, Jenkins D. Biochim Biophys Acta 2011 1812: 1256-1262.
3) Chan SK et al. Am J Physiol Renal Physiol 2010 298: F346-F356.
4) Chiu MG et al. Am J Pathology 2006 169:1925-1938.
5) Kerecuk L et al. Pediatr Nephrol. 2012 27:991-998.