Octreotide inhibits hepatic cystogenesis in a rodent model of polycystic liver disease by reducing cholangiocyte adenosine 3',5'-cyclic monophosphate

Pathobiology of biliary epithelia

Cholangiocytes are epithelial cells that line the intra- and extrahepatic biliary tree. They serve predominantly to mediate the content of luminal biliary fluid, which is controlled via numerous signaling pathways influenced by endogenous (e.g., bile acids, nucleotides, hormones, neurotransmitters) and exogenous (e.g., microbes/microbial products, drugs etc.) molecules. When injured, cholangiocytes undergo apoptosis/lysis, repair and proliferation. They also become senescent, a form of cell cycle arrest, which may prevent propagation of injury and/or malignant transformation. Senescent cholangiocytes can undergo further transformation to a senescence-associated secretory phenotype (SASP), where they begin secreting pro-inflammatory and pro-fibrotic signals that may contribute to disease initiation and progression. These and other concepts related to cholangiocyte pathobiology will be reviewed herein. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

Cholangiocyte autophagy contributes to hepatic cystogenesis in polycystic liver disease and represents a potential therapeutic target

Polycystic liver disease (PLD) is a group of genetic disorders with limited treatment options and significant morbidity. Hepatic cysts arise from cholangiocytes exhibiting a hyperproliferative phenotype. Considering that hyperproliferation of many cell types is associated with alterations in autophagy, we hypothesized that autophagy is altered in PLD cholangiocytes, contributes to hepatic cystogenesis, and might represent a potential therapeutic target. We employed functional pathway cluster analysis and next-generation sequencing, transmission electron microscopy, immunofluorescence confocal microscopy, and western blotting to assess autophagy in human and rodent PLD cholangiocytes. A three-dimensional culture model was used to study the effects of molecular and pharmacologic inhibition of autophagy on hepatic cystogenesis in vitro, and the polycystic kidney disease-specific rat, an animal model of PLD, to study the effects of hydroxychloroquine, a drug that interferes with the autophagy pathway, on disease progression in vivo. Assessment of the transcriptome of PLD cholangiocytes followed by functional pathway cluster analysis revealed that the autophagy-lysosomal pathway is one of the most altered pathways in PLD. Direct evaluation of autophagy in PLD cholangiocytes both in vitro and in vivo showed increased number and size of autophagosomes, lysosomes, and autolysosomes; overexpression of autophagy-related proteins (Atg5, Beclin1, Atg7, and LC3); and enhanced autophagic flux associated with activation of the cAMP-protein kinase A-cAMP response element-binding protein signaling pathway. Molecular and pharmacologic intervention in autophagy with ATG7 small interfering RNA, bafilomycin A₁ , and hydroxychloroquine reduced proliferation of PLD cholangiocytes in vitro and growth of hepatic cysts in three-dimensional cultures. Hydroxychloroquine also efficiently inhibited hepatic cystogenesis in the polycystic kidney disease-specific rat.

CONCLUSION

Autophagy is increased in PLD cholangiocytes, contributes to hepatic cystogenesis, and represents a potential therapeutic target for disease treatment. (Hepatology 2018;67:1088-1108).

Combination of a Histone Deacetylase 6 Inhibitor and a Somatostatin Receptor Agonist Synergistically Reduces Hepatorenal Cystogenesis in an Animal Model of Polycystic Liver Disease

Hepatic cystogenesis in polycystic liver disease (PLD) is associated with abnormalities in multiple cellular processes, including elevated cAMP and overexpression of histone deacetylase 6 (HDAC6). Disease progression in polycystic kidney (PCK) rats (an animal model of PLD) is attenuated by inhibition of either cAMP production or HDAC6. Therefore, we hypothesized that concurrent targeting of HDAC6 and cAMP would synergistically reduce cyst growth. Changes in hepatorenal cystogenesis were examined in PCK rats treated with a pan-HDAC inhibitor, panobinostat; three specific HDAC6 inhibitors, ACY-1215, ACY-738, and ACY-241; and a combination of ACY-1215 and the somatostatin receptor analogue, pasireotide. We also assessed effects of ACY-1215 and pasireotide alone and in combination on cell proliferation, cAMP production, and expression of acetylated α-tubulin in vitro in cultured cholangiocytes and the length of primary cilia and the frequency of ciliated cholangiocytes in vivo in PCK rats. Panobinostat and all three HDAC6 inhibitors decreased hepatorenal cystogenesis in PCK rats. ACY-1215 was more effective than other HDAC inhibitors and was chosen for combinational treatment. ACY-1215 + pasireotide combination synergistically reduced cyst growth and increased length of primary cilia in PCK rats. In cultured cystic cholangiocytes, ACY-1215 + pasireotide combination concurrently decreased cell proliferation and inhibited cAMP levels. These data suggest that the combination of drugs that inhibit HDAC6 and cAMP may be an effective therapy for PLD.

TGR5 contributes to hepatic cystogenesis in rodents with polycystic liver diseases through cyclic adenosine monophosphate/Gαs signaling

Hepatic cystogenesis in polycystic liver disease is associated with increased levels of cyclic adenosine monophosphate (cAMP) in cholangiocytes lining liver cysts. Takeda G protein receptor 5 (TGR5), a G protein-coupled bile acid receptor, is linked to cAMP and expressed in cholangiocytes. Therefore, we hypothesized that TGR5 might contribute to disease progression. We examined expression of TGR5 and Gα proteins in cultured cholangiocytes and in livers of animal models and humans with polycystic liver disease. In vitro, we assessed cholangiocyte proliferation, cAMP levels, and cyst growth in response to (1) TGR5 agonists (taurolithocholic acid, oleanolic acid [OA], and two synthetic compounds), (2) a novel TGR5 antagonist (m-tolyl 5-chloro-2-[ethylsulfonyl] pyrimidine-4-carboxylate [SBI-115]), and (3) a combination of SBI-115 and pasireotide, a somatostatin receptor analogue. In vivo, we examined hepatic cystogenesis in OA-treated polycystic kidney rats and after genetic elimination of TGR5 in double mutant TGR5^-/- ;Pkhd1^del2/del2 mice. Compared to control, expression of TGR5 and Gα_s (but not Gα_i and Gα_q ) proteins was increased 2-fold to 3-fold in cystic cholangiocytes in vitro and in vivo. In vitro, TGR5 stimulation enhanced cAMP production, cell proliferation, and cyst growth by ∼40%; these effects were abolished after TGR5 reduction by short hairpin RNA. OA increased cystogenesis in polycystic kidney rats by 35%; in contrast, hepatic cystic areas were decreased by 45% in TGR5-deficient TGR5^-/- ;Pkhd1^del2/del2 mice. TGR5 expression and its colocalization with Gα_s were increased ∼2-fold upon OA treatment. Levels of cAMP, cell proliferation, and cyst growth in vitro were decreased by ∼30% in cystic cholangiocytes after treatment with SBI-115 alone and by ∼50% when SBI-115 was combined with pasireotide.

CONCLUSION

TGR5 contributes to hepatic cystogenesis by increasing cAMP and enhancing cholangiocyte proliferation; our data suggest that a TGR5 antagonist alone or concurrently with somatostatin receptor agonists represents a potential therapeutic approach in polycystic liver disease. (Hepatology 2017;66:1197-1218).

Everolimus halts hepatic cystogenesis in a rodent model of polycystic-liver-disease

AIM

To develop a MRI-based method for accurate determination of liver volume (LV) and to explore the effect of long-term everolimus (EVR) treatment on LV in PCK rats with hepatomegaly.

METHODS

Thirty-one female PCK rats (model for polycystic-liver-disease: PCLD) were randomized into 3 groups and treatment was started at 16 wk, at the moment of extensive hepatomegaly (comparable to what is done in the human disease). Animals received: controls (n = 14), lanreotide (LAN: 3 mg/kg per 2 wk) (n = 10) or everolimus (EVR: 1 mg/kg per day) (n = 7). LV was measured at week 16, 24, 28. At week 28, all rats were sacrificed and liver tissue was harvested. Fibrosis was evaluated using quantitative image analysis. In addition, gene (quantitative RT-PCR) and protein expression (by Western blot) of the PI3K/AkT/mTOR signaling pathway was investigated.

RESULTS

LV determination by MRI correlated excellent with the ex vivo measurements (r = 0.99, P < 0.001). The relative changes in LV at the end of treatment were: (controls) +31.8%; (LAN) +5.1% and (EVR) +8.8%, indicating a significantly halt of LV progression compared with controls (respectively, P = 0.01 and P = 0.04). Furthermore, EVR significantly reduced the amount of liver fibrosis (P = 0.004) thus might also prevent the development of portal hypertension. There was no difference in phosphorylation of Akt (Threonine 308) between LAN-treated PCK rats control PCK rats, whereas S6 was significantly more phosphorylated in the LAN group. Phosphorylation of Akt was not different between controls and EVR treated rats, however, for S6 there was significantly less phosphorylation in the EVR treated rats. Thus, both drugs interact with the PI3K/AkT/mTOR signaling cascade but acting at different molecular levels.

CONCLUSION

Everolimus halts cyst growth comparable to lanreotide and reduces the development of fibrosis. mTOR-inhibition should be further explored in PCLD patients especially those that need immunosuppression.

An update on the pathophysiology and management of polycystic liver disease

Polycystic liver disease (PLD) is characterized by the presence of multiple cholangiocyte-derived hepatic cysts that progressively replace liver tissue. They are classified as an inherited ciliopathy /cholangiopathy as pathology exists at the level of the primary cilia of cholangiocytes. Aberrant expression of the proteins in primary cilia can impair their structures and functions, thereby promoting cystogenesis. Areas covered: This review begins by looking at the epidemiology of PLD and its natural history. It then describes the pathophysiology and corresponding potential treatment strategies for PLD. Expert commentary: Traditionally, therapies for symptomatic PLD have been limited to symptomatic management and surgical interventions. Such techniques are not completely effective, do not alter the natural history of the disease, and are linked with high rate of re-accumulation of cysts. As a result, there has been a push for drugs targeted at abnormal cellular signaling cascades to address deregulated proliferation, cell dedifferentiation, apoptosis and fluid secretion. Currently, the only available drug treatments that halt disease progression and improve quality of life in PLD patients are somatostatin analogues. Numerous preclinical studies suggest that targeting components of the signaling pathways that influence cyst development can ameliorate growth of hepatic cysts.

Beneficial effect of combined treatment with octreotide and pasireotide in PCK rats, an orthologous model of human autosomal recessive polycystic kidney disease

Increased intracellular cyclic AMP (cAMP) in renal tubular epithelia accelerates the progression of polycystic kidney disease (PKD). Thus, decreasing cAMP levels by an adenylyl cyclase inhibitory G protein activator is considered to be an effective approach in ameliorating PKD. In fact, pasireotide (PAS) was effective in reducing disease progression in animal models of PKD. However, hyperglycemia caused by the administration of PAS is an adverse effect in its clinical use. Whereas, co-administration of octreotide (OCT) with PAS did not increase serum glucose in normal rats. In the current study, we examined the efficacy of combined treatment with OCT and PAS in PCK rats, an autosomal recessive PKD model. Four-week-old PCK males were treated with the long-acting release type of OCT, PAS, or a combination of both (OCT/PAS) for 12 weeks. After termination, serum and renal tissue were used for analyses. Kidney weight, kidney weight per body weight, renal cyst area, renal Ki67 expression, and serum urea nitrogen were significantly decreased either in the PAS or OCT/PAS group, compared with vehicle. Renal tissue cAMP content was significantly decreased by PAS or OCT/PAS treatment, but not OCT, compared with vehicle. As a marker of cellular mTOR signaling activity, renal phospho-S6 kinase expression was significantly decreased by OCT/PAS treatment compared with vehicle, OCT, or PAS. Serum glucose was significantly increased by PAS administration, whereas no difference was shown between vehicle and OCT/PAS, possibly because serum glucagon was decreased either by the treatment of OCT alone or co-application of OCT/PAS. In conclusion, since serum glucose levels are increased by the use of PAS, its combination with OCT may reduce the risk of hyperglycemia associated with PAS monotherapy against PKD progression.

Adenylyl cyclase 5 links changes in calcium homeostasis to cAMP-dependent cyst growth in polycystic liver disease

BACKGROUND & AIMS

Genetic defects in polycystin-1 or -2 (PC1 or PC2) cause polycystic liver disease associated with autosomal dominant polycystic kidney disease (PLD-ADPKD). Progressive cyst growth is sustained by a cAMP-dependent Ras/ERK/HIFα pathway, leading to increased vascular endothelial growth factor A (VEGF-A) signaling. In PC2-defective cholangiocytes, cAMP production in response to [Ca²⁺]_ER depletion is increased, while store-operated Ca²⁺ entry (SOCE), intracellular and endoplasmic reticulum [Ca²⁺]_ER levels are reduced. We investigated whether the adenylyl cyclases, AC5 and AC6, which can be inhibited by Ca²⁺, are activated by the ER chaperone STIM1. This would result in cAMP/PKA-dependent Ras/ERK/HIFα pathway activation in PC2-defective cells, in response to [Ca²⁺]_ER depletion.

METHODS

PC2/AC6 double conditional knockout (KO) mice were generated (Pkd2/AC6 KO) and compared to Pkd2 KO mice. The AC5 inhibitor SQ22,536 or AC5 siRNA were used in isolated cholangiocytes while the inhibitor was used in biliary organoid and animals; liver tissues were harvested for histochemical analysis.

RESULTS

When comparing Pkd2/AC6 KO to Pkd2 KO mice, no decrease in liver cyst size was found, and cellular cAMP after [Ca²⁺]_ER depletion only decreased by 12%. Conversely, in PC2-defective cells, inhibition of AC5 significantly reduced cAMP production, pERK1/2 expression and VEGF-A secretion. AC5 inhibitors significantly reduced growth of biliary organoids derived from Pkd2 KO and Pkd2/AC6 KO mice. In vivo treatment with SQ22,536 significantly reduced liver cystic area and cell proliferation in PC2-defective mice. After [Ca²⁺]_ER depletion in PC2-defective cells, STIM1 interacts with AC5 but not with Orai1, the Ca²⁺ channel that mediates SOCE.

CONCLUSION

[Ca²⁺]_ER depletion in PC2-defective cells activates AC5 and results in stimulation of cAMP/ERK1-2 signaling, VEGF production and cyst growth. This mechanism may represent a novel therapeutic target.

LAY SUMMARY

Polycystic liver diseases are characterized by progressive cyst growth until their complications mandate surgery or liver transplantation. In this manuscript, we demonstrate that inhibiting cell proliferation, which is induced by increased levels of cAMP, may represent a novel therapeutic target to slow the progression of the disease.

Regulators of Cholangiocyte Proliferation

Cholangiocytes, a small population of cells within the normal liver, have been the focus of a significant amount of research over the past two decades because of their involvement in cholangiopathies such as primary sclerosing cholangitis and primary biliary cholangitis. This article summarizes landmark studies in the field of cholangiocyte physiology and aims to provide an updated review of biliary pathogenesis. The historical approach of rodent extrahepatic bile duct ligation and the relatively recent utilization of transgenic mice have led to significant discoveries in cholangiocyte pathophysiology. Cholangiocyte physiology is a complex system based on heterogeneity within the biliary tree and a number of signaling pathways that serve to regulate bile composition. Studies have expanded the list of neuropeptides, neurotransmitters, and hormones that have been shown to be key regulators of proliferation and biliary damage. The peptide histamine and hormones, such as melatonin and angiotensin, angiotensin, as well as numerous sex hormones, have been implicated in cholangiocyte proliferation during cholestasis. Numerous pathways promote cholangiocyte proliferation during cholestasis, and there is growing evidence to suggest that cholangiocyte proliferation may promote hepatic fibrosis. These pathways may represent significant therapeutic potential for a subset of cholestatic liver diseases that currently lack effective therapies.

Gastrointestinal Manifestations of Autosomal-Dominant Polycystic Kidney Disease

Autosomal-dominant polycystic kidney disease (ADPKD) is the most commonly inherited kidney disease, and the fourth most common cause of end-stage renal disease. ADPKD is a systemic disorder, associated with numerous extrarenal manifestations, including polycystic liver disease, the most common gastrointestinal manifestation, and diverticular disease, inguinal, and ventral hernias, pancreatic cysts, and large bile duct abnormalities. All of these gastrointestinal manifestations play a significant role in disease burden in ADPKD, particularly in the later decades of life. Thus, as ADPKD becomes more recognized, it is important for gastroenterologists to be knowledgeable of this monogenic disorder's effects on the digestive system.

Evidence for a "Pathogenic Triumvirate" in Congenital Hepatic Fibrosis in Autosomal Recessive Polycystic Kidney Disease

Autosomal recessive polycystic kidney disease (ARPKD) is a severe monogenic disorder that occurs due to mutations in the PKHD1 gene. Congenital hepatic fibrosis (CHF) associated with ARPKD is characterized by the presence of hepatic cysts derived from dilated bile ducts and a robust, pericystic fibrosis. Cyst growth, due to cyst wall epithelial cell hyperproliferation and fluid secretion, is thought to be the driving force behind disease progression. Liver fibrosis is a wound healing response in which collagen accumulates in the liver due to an imbalance between extracellular matrix synthesis and degradation. Whereas both hyperproliferation and pericystic fibrosis are hallmarks of CHF/ARPKD, whether or not these two processes influence one another remains unclear. Additionally, recent studies demonstrate that inflammation is a common feature of CHF/ARPKD. Therefore, we propose a "pathogenic triumvirate" consisting of hyperproliferation of cyst wall growth, pericystic fibrosis, and inflammation which drives CHF/ARPKD progression. This review will summarize what is known regarding the mechanisms of cyst growth, fibrosis, and inflammation in CHF/ARPKD. Further, we will discuss the potential advantage of identifying a core pathogenic feature in CHF/ARPKD to aid in the development of novel therapeutic approaches. If a core pathogenic feature does not exist, then developing multimodality therapeutic approaches to target each member of the "pathogenic triumvirate" individually may be a better strategy to manage this debilitating disease.

Vasopressin regulates the growth of the biliary epithelium in polycystic liver disease

The neurohypophysial hormone arginine vasopressin (AVP) acts by three distinct receptor subtypes: V1a, V1b, and V2. In the liver, AVP is involved in ureogenesis, glycogenolysis, neoglucogenesis and regeneration. No data exist about the presence of AVP in the biliary epithelium. Cholangiocytes are the target cells in a number of animal models of cholestasis, including bile duct ligation (BDL), and in several human pathologies, such as polycystic liver disease characterized by the presence of cysts that bud from the biliary epithelium. In vivo, liver fragments from normal and BDL mice and rats as well as liver samples from normal and ADPKD patients were collected to evaluate: (i) intrahepatic bile duct mass by immunohistochemistry for cytokeratin-19; and (ii) expression of V1a, V1b and V2 by immunohistochemistry, immunofluorescence and real-time PCR. In vitro, small and large mouse cholangiocytes, H69 (non-malignant human cholangiocytes) and LCDE (human cholangiocytes from the cystic epithelium) were stimulated with vasopressin in the absence/presence of AVP antagonists such as OPC-31260 and Tolvaptan, before assessing cellular growth by MTT assay and cAMP levels. Cholangiocytes express V2 receptor that was upregulated following BDL and in ADPKD liver samples. Administration of AVP increased proliferation and cAMP levels of small cholangiocytes and LCDE cells. We found no effect in the proliferation of large mouse cholangiocytes and H69 cells. Increases were blocked by preincubation with the AVP antagonists. These results showed that AVP and its receptors may be important in the modulation of the proliferation rate of the biliary epithelium.

Ursodeoxycholic acid in advanced polycystic liver disease: A phase 2 multicenter randomized controlled trial

BACKGROUND & AIMS

Ursodeoxycholic acid (UDCA) inhibits proliferation of polycystic human cholangiocytes in vitro and hepatic cystogenesis in a rat model of polycystic liver disease (PLD) in vivo. Our aim was to test whether UDCA may beneficially affect liver volume in patients with advanced PLD.

METHODS

We conducted an international, multicenter, randomized controlled trial in symptomatic PLD patients from three tertiary referral centers. Patients with PLD and total liver volume (TLV) ⩾2500ml were randomly assigned to UDCA treatment (15-20mg/kg/day) for 24weeks, or to no treatment. Primary endpoint was proportional change in TLV. Secondary endpoints were change in symptoms and health-related quality of life. We performed a post-hoc analysis of the effect of UDCA on liver cyst volume (LCV).

RESULTS

We included 34 patients and were able to assess primary endpoint in 32 patients, 16 with autosomal dominant polycystic kidney disease (ADPKD) and 16 with autosomal dominant polycystic liver disease (ADPLD). Proportional TLV increased by 4.6±7.7% (mean TLV increased from 6697ml to 6954ml) after 24weeks of UDCA treatment compared to 3.1±3.8% (mean TLV increased from 5512ml to 5724ml) in the control group (p=0.493). LCV was not different after 24weeks between controls and UDCA treated patients (p=0.848). However, UDCA inhibited LCV growth in ADPKD patients compared to ADPKD controls (p=0.049).

CONCLUSIONS

UDCA administration for 24weeks did not reduce TLV in advanced PLD, but UDCA reduced LCV growth in ADPKD patients. Future studies might explore whether ADPKD and ADPLD patients respond differently to UDCA treatment.

LAY SUMMARY

Current therapies for polycystic liver disease are invasive and have high recurrence risks. Our trial showed that the drug, ursodeoxycholic acid, was not able to reduce liver volume in patients with polycystic liver disease. However, a subgroup analysis in patients that have kidney cysts as well showed that liver cyst volume growth was reduced in patients who received ursodeoxycholic acid in comparison to patients who received no treatment. Trial registration number https://www.clinicaltrials.gov/: NCT02021110. EudraCT Number https://www.clinicaltrialsregister.eu/: 2013-003207-19.

Long-term Effects of Octreotide on Liver Volume in Patients With Polycystic Kidney and Liver Disease

BACKGROUND & AIMS

Short-term studies have shown that somatostatin analogues are effective in patients with polycystic kidney and liver disease. We evaluated the long-term effects of long-acting release octreotide (octreotide LAR), a somatostatin inhibitor, vs placebo in these patients.

METHODS

We performed a controlled study of adults with polycystic kidney and liver disease (estimated glomerular filtration rate, 40 mL/min/1.73m(2) or more) at a single center in Italy. We analyzed data from 27 patients randomly assigned to groups given octreotide LAR (40 mg, n = 14) or placebo (n = 13) each month for 3 years. The primary outcome was absolute and percentage change in total liver volume (TLV), which was measured by magnetic resonance imaging at baseline, after 3 years of treatment, and then 2 years after treatment ended.

RESULTS

Baseline characteristics were similar between groups. After 3 years, TLV decreased by 130.2 ± 133.2 mL in patients given octreotide LAR (7.8% ± 7.4%) (P = .003) but increased by 144.3 ± 316.8 mL (6.1% ± 14.1%) in patients given placebo. Change vs baseline differed significantly between groups (P = .004). Two years after treatment ended, TLV had decreased 14.4 ± 138.4 mL (0.8% ± 9.7%) from baseline in patients given octreotide LAR but increased by 224.4 ± 331.7 mL (11.0% ± 14.4%) in patients given placebo. Changes vs baseline still differed significantly between groups (P = .046). Decreases in TLV were similar in each sex; the change in TLV was greatest among subjects with larger baseline TLV. No patient withdrew because of side effects.

CONCLUSIONS

In a placebo-controlled study of patients with polycystic kidney and liver disease, 3 years of treatment with octreotide LAR significantly reduced liver volume; reductions were maintained for 2 years after treatment ended. Octreotide LAR was well-tolerated. ClinicalTrials.gov number: NCT02119052.

Modulation of Polycystic Kidney Disease Severity by Phosphodiesterase 1 and 3 Subfamilies

Aberrant intracellular calcium levels and increased cAMP signaling contribute to the development of polycystic kidney disease (PKD). cAMP can be hydrolyzed by various phosphodiesterases (PDEs). To examine the role of cAMP hydrolysis and the most relevant PDEs in the pathogenesis of PKD, we examined cyst development in Pde1- or Pde3-knockout mice on the Pkd2(-/WS25) background (WS25 is an unstable Pkd2 allele). These PDEs were selected because of their importance in cross-talk between calcium and cyclic nucleotide signaling (PDE1), control of cell proliferation and cystic fibrosis transmembrane conductance regulator (CFTR) -driven fluid secretion (PDE3), and response to vasopressin V2 receptor activation (both). In Pkd2(-/WS25) mice, knockout of Pde1a, Pde1c, or Pde3a but not of Pde1b or Pde3b aggravated the development of PKD and was associated with higher levels of protein kinase A-phosphorylated (Ser133) cAMP-responsive binding protein (P-CREB), activating transcription factor-1, and CREB-induced CRE modulator proteins in kidney nuclear preparations. Immunostaining also revealed higher expression of P-CREB in Pkd2(-/) (WS25);Pde1a(-/-), Pkd2(-) (/WS25);Pde1c(-/-), and Pkd2(-/) (WS25);Pde3a(-/-) kidneys. The cystogenic effect of desmopressin administration was markedly enhanced in Pkd2(-/WS25);Pde3a(-/-) mice, despite PDE3 accounting for only a small fraction of renal cAMP PDE activity. These observations show that calcium- and calmodulin-dependent PDEs (PDE1A and PDE1C) and PDE3A modulate the development of PKD, possibly through the regulation of compartmentalized cAMP pools that control cell proliferation and CFTR-driven fluid secretion. Treatments capable of increasing the expression or activity of these PDEs may, therefore, retard the development of PKD.

Molecular pathways and therapies in autosomal-dominant polycystic kidney disease

Autosomal-dominant polycystic kidney disease (ADPKD) is the most prevalent inherited renal disease, characterized by multiple cysts that can eventually lead to kidney failure. Studies investigating the role of primary cilia and polycystins have significantly advanced our understanding of the pathogenesis of PKD. This review will present clinical and basic aspects of ADPKD, review current concepts of PKD pathogenesis, evaluate potential therapeutic targets, and highlight challenges for future clinical studies.

Nephronophthisis: should we target cysts or fibrosis?

Ciliopathy nephronophthisis (NPHP), a common cause of end-stage renal disease (ESRD) in children and young adults, is characterized by disintegration of the tubular basement membrane accompanied by irregular thickening and attenuation, interstitial fibrosis and tubular atrophy, and occasionally cortico-medullary cyst formation. Pharmacological approaches that delay the development of ESRD could potentially extend the window of therapeutic opportunity for this group of patients, generating time to find an appropriate donor or even for new treatments to mature. In this review we provide an overview of compounds that have been tested to ameliorate kidney cysts and/or fibrosis. We also revisit paclitaxel as a potential strategy to target fibrosis in NPHP. At low dosage this chemotherapy drug shows promising results in rodent models of renal fibrosis. Possible adverse events and safety of paclitaxel treatment in pediatric patients would need to be investigated, as would the efficacy, optimum dose, and administration schedule for the treatment of renal fibrosis in NPHP patients. Paclitaxel is an approved drug for human use with known pharmacokinetics, which could potentially be used in other ciliopathies through targeting the microtubule skeleton.

Kidney Disease Progression in Autosomal Recessive Polycystic Kidney Disease

OBJECTIVE

To define glomerular filtration rate (GFR) decline, hypertension (HTN), and proteinuria in subjects with autosomal recessive polycystic kidney disease (ARPKD) and compare with 2 congenital kidney disease control groups in the Chronic Kidney Disease in Children cohort.

STUDY DESIGN

GFR decline (iohexol clearance), rates of HTN (ambulatory/casual blood pressures), antihypertensive medication usage, left ventricular hypertrophy, and proteinuria were analyzed in subjects with ARPKD (n = 22) and 2 control groups: aplastic/hypoplastic/dysplastic disorders (n = 44) and obstructive uropathies (n = 44). Differences between study groups were examined with the Wilcoxon rank sum test.

RESULTS

Annualized GFR change in subjects with ARPKD was -1.4 mL/min/1.73 m(2) (-6%), with greater decline in subjects age ≥ 10 years (-11.5%). However, overall rates of GFR decline did not differ significantly in subjects with ARPKD vs controls. There were no significant differences in rates of HTN or left ventricular hypertrophy, but subjects with ARPKD had a greater percent on ≥ 3 blood pressure medications (32% vs 0%, P < .0001), more angiotensin-converting enzyme inhibitor use (82% vs 27% vs 36%, P < .0005), and less proteinuria (urine protein: creatinine = 0.1 vs 0.6, P < .005).

CONCLUSIONS

This study reports rates of GFR decline, HTN, and proteinuria in a small but well-phenotyped ARPKD cohort. The relatively slow rate of GFR decline in subjects with ARPKD and absence of significant proteinuria suggest that these standard clinical measures may have limited utility in assessing therapeutic interventions and highlight the need for other ARPKD kidney disease progression biomarkers.

Cell Proliferation and Apoptosis in ADPKD

Increased tubular epithelial cell proliferation with fluid secretion is a key hallmark of autosomal dominant polycystic kidney disease (ADPKD). With disruption of either PKD1 or PKD2, the main causative genes of ADPKD, intracellular calcium homeostasis and cAMP accumulation are disrupted, which in turn leads to altered signaling in the pathways that regulate cell proliferation. These dysregulations finally stimulate the development of fluid-filled cysts originating from abnormally proliferating renal tubular cells. In addition, dysregulated apoptosis is observed in dilated cystic tubules. An imbalance between cell proliferation and apoptosis seems to contribute to cyst growth and renal tissue remodeling in ADPKD. In this section, the mechanisms through which cell proliferation and apoptosis are involved in disease progression, and further, how those signaling pathways impinge on each other in ADPKD will be discussed.

Genetic Mechanisms of ADPKD

Autosomal dominant polycystic kidney disease is caused by mutation of PKD1 (polycystic kidney disease-1) or PKD2 (polycystic kidney disease-2). PKD1 and PKD2 encode PC1 (polycystin-1) and PC2 (polycystin-2), respectively. In addition, the mutation of cilia-associated proteins is also a recognized major factor of pathogenesis, since PC1 and PC2 are located in primary cilium. Abnormalities of PC1 or PC2 lead to aberrant signaling through downstream pathways, such as the negative growth regulation, G protein activation, and canonical and non-canonical Wnt pathways. According to the "second hit" model, an additional somatic mutation results in the expansion of cyst growth. In this chapter we discuss the genetic mechanisms and signaling pathways involved in ADPKD.

Initial evaluation of hepatic T1 relaxation time as an imaging marker of liver disease associated with autosomal recessive polycystic kidney disease (ARPKD)

Autosomal recessive polycystic kidney disease (ARPKD) is a potentially lethal multi-organ disease affecting both the kidneys and the liver. Unfortunately, there are currently no non-invasive methods to monitor liver disease progression in ARPKD patients, limiting the study of potential therapeutic interventions. Herein, we perform an initial investigation of T1 relaxation time as a potential imaging biomarker to quantitatively assess the two primary pathologic hallmarks of ARPKD liver disease: biliary dilatation and periportal fibrosis in the PCK rat model of ARPKD. T1 relaxation time results were obtained for five PCK rats at 3 months of age using a Look-Locker acquisition on a Bruker BioSpec 7.0 T MRI scanner. Six three-month-old Sprague-Dawley (SD) rats were also scanned as controls. All animals were euthanized after the three-month scans for histological and biochemical assessments of bile duct dilatation and hepatic fibrosis for comparison. PCK rats exhibited significantly increased liver T1 values (mean ± standard deviation = 935 ± 39 ms) compared with age-matched SD control rats (847 ± 26 ms, p = 0.01). One PCK rat exhibited severe cholangitis (mean T1  = 1413 ms), which occurs periodically in ARPKD patients. The observed increase in the in vivo liver T1 relaxation time correlated significantly with three histological and biochemical indicators of biliary dilatation and fibrosis: bile duct area percent (R = 0.85, p = 0.002), periportal fibrosis area percent (R = 0.82, p = 0.004), and hydroxyproline content (R = 0.76, p = 0.01). These results suggest that hepatic T1 relaxation time may provide a sensitive and non-invasive imaging biomarker to monitor ARPKD liver disease.

Lanreotide Reduces Liver Volume, But Might Not Improve Muscle Wasting or Weight Loss, in Patients With Symptomatic Polycystic Liver Disease

BACKGROUND & AIMS

Polycystic liver disease (PCLD) can induce malnutrition owing to extensive hepatomegaly and patients might require liver transplantation. Six months of treatment with the somatostatin analogue lanreotide (120 mg) reduces liver volume. We investigated the efficacy of a lower dose of lanreotide and its effects on nutritional status.

METHODS

We performed an 18-month prospective study at 2 tertiary medical centers in Belgium from January 2011 through August 2012. Fifty-nine patients with symptomatic PCLD were given lanreotide (90 mg, every 4 weeks) for 6 months. Patients with reductions in liver volume of more than 100 mL (responders, primary end point) continued to receive lanreotide (90 mg) for an additional year (18 months total). Nonresponders were offered increased doses, up to 120 mg lanreotide, until 18 months. Liver volume and body composition were measured by computed tomography at baseline and at months 6 and 18. Patients also were assessed by the PCLD-specific complaint assessment at these time points.

RESULTS

Fifty-three patients completed the study; 21 patients (40%) were responders. Nineteen of the responders (90%) continued as responders until 18 months. At this time point, they had a mean reduction in absolute liver volume of 430 ± 92 mL. In nonresponders (n = 32), liver volume increased by a mean volume of 120 ± 42 mL at 6 months. However, no further increase was observed after dose escalation in the 24 patients who continued to the 18-month end point. All subjects had decreased scores on all subscales of the PCLD-specific complaint assessment, including better food intake (P = .04). Subjects did not have a mean change in subcutaneous or visceral fat mass, but did have decreases in mean body weight (2 kg) and total muscle mass (1.06 cm(2)/h(2)). Subjects also had a significant mean reduction in their level of insulin-like growth factor 1, from 19% below the age-adjusted normal range level at baseline to 50% at 18 months (P = .002).

CONCLUSIONS

In a prospective study, we observed that low doses of lanreotide (90 mg every 4 weeks) reduced liver volumes and symptoms in patients with PCLD. However, patients continued to lose weight and muscle mass. The effects of somatostatin analogues on sarcopenia require investigation. Clinicaltrials.gov: NCT01315795.

Ursodeoxycholic acid inhibits hepatic cystogenesis in experimental models of polycystic liver disease

BACKGROUND & AIMS

Polycystic liver diseases (PLDs) are genetic disorders characterized by progressive biliary cystogenesis. Current therapies show short-term and/or modest beneficial effects. Cystic cholangiocytes hyperproliferate as a consequence of diminished intracellular calcium levels ([Ca(2+)]i). Here, the therapeutic value of ursodeoxycholic acid (UDCA) was investigated.

METHODS

Effect of UDCA was examined in vitro and in polycystic (PCK) rats. Hepatic cystogenesis and fibrosis, and the bile acid (BA) content were evaluated from the liver, bile, serum, and kidneys by HPLC-MS/MS.

RESULTS

Chronic treatment of PCK rats with UDCA inhibits hepatic cystogenesis and fibrosis, and improves their motor behaviour. As compared to wild-type animals, PCK rats show increased BA concentration ([BA]) in liver, similar hepatic Cyp7a1 mRNA levels, and diminished [BA] in bile. Likewise, [BA] is increased in cystic fluid of PLD patients compared to their matched serum levels. In PCK rats, UDCA decreases the intrahepatic accumulation of cytotoxic BA, normalizes their diminished [BA] in bile, increases the BA secretion in bile and diminishes the increased [BA] in kidneys. In vitro, UDCA inhibits the hyperproliferation of polycystic human cholangiocytes via a PI3K/AKT/MEK/ERK1/2-dependent mechanism without affecting apoptosis. Finally, the presence of glycodeoxycholic acid promotes the proliferation of polycystic human cholangiocytes, which is inhibited by both UDCA and tauro-UDCA.

CONCLUSIONS

UDCA was able to halt the liver disease of a rat model of PLD through inhibiting cystic cholangiocyte hyperproliferation and decreasing the levels of cytotoxic BA species in the liver, which suggests the use of UDCA as a potential therapeutic tool for PLD patients.

Vasopressin and disruption of calcium signalling in polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic kidney disease and is responsible for 5-10% of cases of end-stage renal disease worldwide. ADPKD is characterized by the relentless development and growth of cysts, which cause progressive kidney enlargement associated with hypertension, pain, reduced quality of life and eventual kidney failure. Mutations in the PKD1 or PKD2 genes, which encode polycystin-1 (PC1) and polycystin-2 (PC2), respectively, cause ADPKD. However, neither the functions of these proteins nor the molecular mechanisms of ADPKD pathogenesis are well understood. Here, we review the literature that examines how reduced levels of functional PC1 or PC2 at the primary cilia and/or the endoplasmic reticulum directly disrupts intracellular calcium signalling and indirectly disrupts calcium-regulated cAMP and purinergic signalling. We propose a hypothetical model in which dysregulated metabolism of cAMP and purinergic signalling increases the sensitivity of principal cells in collecting ducts and of tubular epithelial cells in the distal nephron to the constant tonic action of vasopressin. The resulting magnified response to vasopressin further enhances the disruption of calcium signalling that is initiated by mutations in PC1 or PC2, and activates downstream signalling pathways that cause impaired tubulogenesis, increased cell proliferation, increased fluid secretion and interstitial inflammation.

Cholangiocytes derived from human induced pluripotent stem cells for disease modeling and drug validation

The study of biliary disease has been constrained by a lack of primary human cholangiocytes. Here we present an efficient, serum-free protocol for directed differentiation of human induced pluripotent stem cells into cholangiocyte-like cells (CLCs). CLCs show functional characteristics of cholangiocytes, including bile acids transfer, alkaline phosphatase activity, γ-glutamyl-transpeptidase activity and physiological responses to secretin, somatostatin and vascular endothelial growth factor. We use CLCs to model in vitro key features of Alagille syndrome, polycystic liver disease and cystic fibrosis (CF)-associated cholangiopathy. Furthermore, we use CLCs generated from healthy individuals and patients with polycystic liver disease to reproduce the effects of the drugs verapamil and octreotide, and we show that the experimental CF drug VX809 rescues the disease phenotype of CF cholangiopathy in vitro. Our differentiation protocol will facilitate the study of biological mechanisms controlling biliary development, as well as disease modeling and drug screening.

Interventions for preventing the progression of autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited disorder causing kidney disease. Current clinical management of ADPKD focuses primarily on symptom control and reducing associated complications, particularly hypertension. In recent years, improved understanding of molecular and cellular mechanisms involved in kidney cyst growth and disease progression has resulted in new pharmaceutical agents to target disease pathogenesis to prevent progressive disease.

OBJECTIVES

We aimed to evaluate the effects of interventions for preventing ADPKD progression on kidney function, kidney endpoints, kidney structure, patient-centred endpoints (such as cardiovascular events, sudden death, all-cause mortality, hospitalisations, BP control, quality of life, and kidney pain), as well as the general and specific adverse effects related to their use.

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register to 6 June 2015 using relevant search terms.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing any interventions for preventing the progression of ADPKD with other interventions or placebo were considered for inclusion without language restriction.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study risks of bias and extracted data. We summarised treatment effects on clinical outcomes, kidney function and structure and adverse events using random effects meta-analysis. We assessed heterogeneity in estimated treatment effects using the Cochran Q test and I(2) statistic. Summary treatment estimates were calculated as a mean difference (MD) or standardised mean difference (SMD) for continuous outcomes and a risk ratio (RR) for dichotomous outcomes together with their 95% confidence intervals.

MAIN RESULTS

We included 30 studies (2039 participants) that investigated 11 pharmacological interventions (angiotensin-converting enzyme inhibitors (ACEi), angiotensin receptor blockers (ARBs), calcium channel blockers, beta blockers, vasopressin receptor 2 (V2R) antagonists, mammalian target of rapamycin (mTOR) inhibitors, somatostatin analogues, antiplatelet agents, eicosapentaenoic acids, statins and vitamin D compounds) in this review.ACEi significantly reduced diastolic blood pressure (9 studies, 278 participants: MD -4.96 mm Hg, 95% CI -8.88 to -1.04), but had uncertain effects on kidney volumes (MD -42.50 mL, 95% CI -115.68 to 30.67), GFR (MD -3.41 mL/min/1.73 m(2), 95% CI -15.83 to 9.01), and SCr (MD -0.02 mg/dL, 95% CI -0.14 to 0.09), in data largely restricted to children. ACEi did not show different effects on GFR (MD -8.19 mL/min/1.73 m(2), 95% CI -29.46 to 13.07) and albuminuria (SMD -0.19, 95% CI -1.77 to 1.39) when compared with beta-blockers, or SCr (MD 0.00 mg/dL, 95% CI -0.09 to 0.10) when compared with ARBs.Data for effects of V2R antagonists on kidney function and volumes compared to placebo were limited to narrative information within a single study while these agents increased thirst (1444 participants: RR 2.70, 95% CI 2.24 to 3.24) and dry mouth (1455 participants: RR 1.33, 95% CI 1.01 to 1.76).Compared with no treatment, mTOR inhibitors had uncertain effects on kidney function (2 studies, 115 participants: MD 4.45 mL/min/1.73 m(2), 95% CI -3.20 to 12.11) and kidney volume (MD -0.08 L, 95% CI -0.75 to 0.59) but in three studies (560 participants) caused angioedema (RR 13.39, 95% CI 2.56 to 70.00), oral ulceration (RR 6.77, 95% CI 4.42 to 10.38), infections (RR 1.14, 95% CI 1.04 to 1.25) and diarrhoea (RR 1.70, 95% CI 1.26 to 2.29).Somatostatin analogues (6 studies, 138 participants) slightly improved SCr (MD -0.43 mg/dL, 95% CI -0.86 to -0.01) and total kidney volume (MD -0.62 L, 95% CI -1.22 to -0.01) but had no definite effects on GFR (MD 9.50 mL/min, 95% CI -4.45 to 23.44) and caused diarrhoea (RR 3.72, 95% CI 1.43 to 9.68).Data for calcium channel blockers, eicosapentaenoic acids, statins, vitamin D compounds and antiplatelet agents were sparse and inconclusive.Random sequence generation was adequate in eight studies, and in almost half of the studies, blinding was not present or not specified. Most studies did not adequately report outcomes, which adversely affected our ability to assess this bias. The overall drop-out rate was over 10% in nine studies, and few were conducted using intention-to-treat analyses.

AUTHORS' CONCLUSIONS

Although several interventions are available for patients with ADPKD, at present there is little or no evidence that treatment improves patient outcomes in this population and is associated with frequent adverse effects. Additional large randomised studies focused on patient-centred outcomes are needed.

An overview of experimental and early investigational therapies for the treatment of polycystic kidney disease

INTRODUCTION

At present, treatment of autosomal dominant polycystic kidney disease (ADPKD) is essentially supportive as there is still no specific therapy. However, recent advances with ADPKD pathophysiology have stimulated research for new therapeutic strategies.

AREAS COVERED

The aim of this systematic review is to analyze the experimental and early investigational therapies currently under evaluation in this field. Data from completed clinical trials were retrieved from the currently available scientific literature and from the ClinicalTrials.gov website.

EXPERT OPINION

Among the drugs currently being explored, mammalian target of rapamycin inhibitors reduce kidney volume enlargement but their role remains uncertain. The most promising drug is the V2 receptor antagonist tolvaptan, which reduces the increased rate of total kidney volume and slows down glomerular filtration rate decline. The main candidates for the treatment of cysts growth, both in the kidney and in the liver whenever present, are the somatostatin analogues, such as lanreotide and octreotide and more recently pasireotide. As for other therapies, some favorable results have been achieved but data are still not sufficient to establish if these approaches may be beneficial in slowing ADPKD progression in the future.

Proliferation-Independent Initiation of Biliary Cysts in Polycystic Liver Diseases

Biliary cysts in adult patients affected by polycystic liver disease are lined by cholangiocytes that proliferate, suggesting that initiation of cyst formation depends on proliferation. Here, we challenge this view by analyzing cyst-lining cell proliferation and differentiation in Cpk mouse embryos and in livers from human fetuses affected by Autosomal Recessive Polycystic Kidney Disease (ARPKD), at early stages of cyst formation. Proliferation of fetal cholangiocyte precursors, measured by immunostaining in human and mouse livers, was low and did not differ between normal and ARPKD or Cpk livers, excluding excessive proliferation as an initiating cause of liver cysts. Instead, our analyses provide evidence that the polycystic livers exhibit increased and accelerated differentiation of hepatoblasts into cholangiocyte precursors, eventually coalescing into large biliary cysts. Lineage tracing experiments, performed in mouse embryos, indicated that the cholangiocyte precursors in Cpk mice generate cholangiocytes and periportal hepatocytes, like in wild-type animals. Therefore, contrary to current belief, cyst formation in polycystic liver disease does not necessarily depend on overproliferation. Combining our prenatal data with available data from adult livers, we propose that polycystic liver can be initiated by proliferation-independent mechanisms at a fetal stage, followed by postnatal proliferation-dependent cyst expansion.

The Cholangiopathies

Cholangiocytes (ie, the epithelial cells that line the bile ducts) are an important subset of liver cells. They are actively involved in the modification of bile volume and composition, are activated by interactions with endogenous and exogenous stimuli (eg, microorganisms, drugs), and participate in liver injury and repair. The term cholangiopathies refers to a category of chronic liver diseases that share a central target: the cholangiocyte. The cholangiopathies account for substantial morbidity and mortality given their progressive nature, the challenges associated with clinical management, and the lack of effective medical therapies. Thus, cholangiopathies usually result in end-stage liver disease requiring liver transplant to extend survival. Approximately 16% of all liver transplants performed in the United States between 1988 and 2014 were for cholangiopathies. For all these reasons, cholangiopathies are an economic burden on patients, their families, and society. This review offers a concise summary of the biology of cholangiocytes and describes a conceptual framework for development of the cholangiopathies. We also present the recent progress made in understanding the pathogenesis of and how this knowledge has influenced therapies for the 6 common cholangiopathies-primary biliary cirrhosis, primary sclerosing cholangitis, cystic fibrosis involving the liver, biliary atresia, polycystic liver disease, and cholangiocarcinoma-because the latest scientific progress in the field concerns these conditions. We performed a search of the literature in PubMed for published papers using the following terms: cholangiocytes, biliary epithelia, cholestasis, cholangiopathy, and biliary disease. Studies had to be published in the past 5 years (from June 1, 2009, through May 31, 2014), and non-English studies were excluded.

Novel therapeutic approaches to autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited disorder characterized by the progressive growth of renal cysts that, over time, destroy the architecture of the renal parenchyma and typically lead to kidney failure by the sixth decade of life. ADPKD is common and represents a leading cause of renal failure worldwide. Currently, there are no Food and Drug Administration-approved treatments for the disease, and the existing standard of care is primarily supportive in nature. However, significant advances in the understanding of the molecular biology of the disease have inspired investigation into potential new therapies. Several drugs designed to slow or arrest the progression of ADPKD have shown promise in preclinical models and clinical trials, including vasopressin receptor antagonists and somatostatin analogs. This article examines the literature underlying the rationale for molecular therapies for ADPKD and reviews the existing clinical evidence for their indication for human patients with the disease.

Aspiration sclerotherapy combined with pasireotide to improve reduction of large symptomatic hepatic cysts (SCLEROCYST): study protocol for a randomized controlled trial

BACKGROUND

Aspiration sclerotherapy is an effective therapeutic option for large symptomatic hepatic cysts. However, incomplete cyst reduction following aspiration sclerotherapy is frequently reported. Strong post-procedural cyst fluid secretion by cholangiocytes, which line the epithelium of the hepatic cyst, seems to be associated with lower reduction rates. Previous studies showed that somatostatin analogues curtail hepatic cyst fluid production. This trial will evaluate the effect of aspiration sclerotherapy combined with the somatostatin analogue pasireotide on cyst reduction. By combining treatment modalities we aim to improve cyst reduction leading to greater symptomatic relief and reduced rates of cyst recurrence.

METHODS/DESIGN

This single center, randomized, double-blind, placebo-controlled clinical trial evaluates the additional effect of pasireotide when combined with aspiration sclerotherapy in patients with a large (>5 cm) symptomatic hepatic cyst. A total of 34 participants will be randomized in a 1:1 ratio. In the active arm, patients will receive pasireotide (long-acting release, 60 mg injection) two weeks prior to and two weeks following aspiration sclerotherapy. Patients in the control arm will receive placebo injections at corresponding intervals. The primary outcome is proportional cyst diameter reduction four weeks after aspiration sclerotherapy compared to baseline measurements, obtained by ultrasonography. As secondary outcomes, proportional volume reduction, recurrence, symptomatic relief and improvement of health-related quality of life will be assessed. Furthermore, safety and tolerability of the combination of pasireotide and aspiration sclerotherapy will be evaluated.

DISCUSSION

This trial aims to improve efficacy of aspiration sclerotherapy by a combined approach of two treatment modalities. We hypothesize that pasireotide will decrease fluid re-accumulation after aspiration sclerotherapy, leading to effective hepatic cyst reduction and symptomatic relief.

TRIALS REGISTRATION

This trial is registered with ClinicalTrials.gov (identifier: NCT02048319 ; registered on 6 January 2014) and EudraCT (identifier: 2013-003168-29; registered on 16 August 2013).

TGR5 in the Cholangiociliopathies

A plasma membrane-bound G protein-coupled receptor, TGR5, that transmits bile acid signaling into a cellular response primarily via the cAMP pathway is expressed in human and rodent cholangiocytes and is localized to multiple, diverse subcellular compartments, including primary cilia. Ciliary-associated TGR5 plays an important role in cholangiocyte physiology and may contribute to a group of liver diseases referred to as the 'cholangiociliopathies', which include polycystic liver disease (PLD) and, possibly, cholangiocarcinoma and primary sclerosing cholangitis. Based on our observations that (1) ciliated and nonciliated cholangiocytes respond to TGR5 activation differently (i.e. the level of cAMP increases in nonciliated cholangiocytes but decreases in ciliated cells) and (2) hepatic cysts are derived from cholangiocytes that are characterized by both malformed cilia and increased cAMP levels, we hypothesized that TGR5-mediated cAMP signaling in cystic cholangiocytes contributes to hepatic cystogenesis. Indeed, our studies show that TGR5 is overexpressed and mislocalized in cystic cholangiocytes, and when activated by ligands, results in increased intracellular cAMP levels, cholangiocyte hyperproliferation and cyst growth. Our studies also show that genetic elimination of TGR5 in an animal model of PLD inhibits hepatic cystogenesis. Collectively, these data suggest the involvement of TGR5 in PLD and that TGR5 targeting in cystic cholangiocytes may have therapeutic potential.

Tolvaptan plus pasireotide shows enhanced efficacy in a PKD1 model

Autosomal dominant polycystic kidney disease (ADPKD) is a leading cause of ESRD. A central defect associated with ADPKD pathology is elevated levels of 3', 5'-cyclic AMP (cAMP). Compounds such as tolvaptan and pasireotide, which indirectly reduce adenylyl cyclase 6 (AC6) activity, have hence proven effective in slowing cyst progression. Here, we tested the efficacy of these compounds individually and in combination in a hypomorphic PKD1 model, Pkd1(R3277C/R3277C) (Pkd1(RC/RC)), in a 5-month preclinical trial. Initially, the Pkd1(RC/RC) model was inbred into the C57BL/6 background, minimizing disease variability, and the pathogenic effect of elevating cAMP was confirmed by treatment with the AC6 stimulant desmopressin. Treatment with tolvaptan or pasireotide alone markedly reduced cyst progression and in combination showed a clear additive effect. Furthermore, combination treatment significantly reduced cystic and fibrotic volume and decreased cAMP to wild-type levels. We also showed that Pkd1(RC/RC) mice experience hepatic hypertrophy that can be corrected by pasireotide. The observed additive effect reinforces the central role of AC6 and cAMP in ADPKD pathogenesis and highlights the likely benefit of combination therapy for patients with ADPKD.

Polycystic liver diseases: advanced insights into the molecular mechanisms

Polycystic liver diseases are genetic disorders characterized by progressive bile duct dilatation and/or cyst development. The large volume of hepatic cysts causes different symptoms and complications such as abdominal distension, local pressure with back pain, hypertension, gastro-oesophageal reflux and dyspnea as well as bleeding, infection and rupture of the cysts. Current therapeutic strategies are based on surgical procedures and pharmacological management, which partially prevent or ameliorate the disease. However, as these treatments only show short-term and/or modest beneficial effects, liver transplantation is the only definitive therapy. Therefore, interest in understanding the molecular mechanisms involved in disease pathogenesis is increasing so that new targets for therapy can be identified. In this Review, the genetic mechanisms underlying polycystic liver diseases and the most relevant molecular pathways of hepatic cystogenesis are discussed. Moreover, the main clinical and preclinical studies are highlighted and future directions in basic as well as clinical research are indicated.

Safety study of somatostatin analogue octreotide for autosomal dominant polycystic kidney disease in Japan

BACKGROUND

The total kidney volume (TKV) and total liver volume (TLV) increase and renal function decreases progressively in patients with autosomal dominant polycystic kidney disease (ADPKD). Somatostatin analogues, such as octreotide, reduce these increases in TKV and TLV. The aim of this study was to examine the safety of the short-term administration of octreotide long-acting release (octreotide-LAR) in a small number of cases.

METHODS

Four ADPKD patients with an estimated glomerular filtration rate (eGFR) > 45 mL/min/1.73 m(2), TKV > 1,000 mL, and TLV > 3,000 mL were enrolled. Two 20-mg octreotide-LAR intramuscular injections were repeated every 4 weeks for 24 weeks. Laboratory and clinical assessments were repeated every 4 weeks, and TKV and TLV were measured by magnetic resonance imaging before and after the study.

RESULTS

In the laboratory tests, there was no abnormal variable except for a significant decrease of alanine aminotransferase. The means of TKV and TLV decreased from 2,007 to 1,903 mL and from 9,197 to 8,866 mL, respectively, but the changes were not significant. eGFR did not change significantly. Adverse events involved loose stools in two patients, as well as injection site granuloma and abdominal pain in one patient each, which resolved spontaneously.

CONCLUSION

Octreotide-LAR may be safe and effective for preventing TKV and TLV increases (UMIN000009214).

The defects of cholangiocyte primary cilia in patients with graft cholangiopathies

PURPOSE

To observe the morphologic changes in intrahepatic bile ducts and the defects of cholangiocyte primary cilia in patients with graft cholangiopathies.

METHODS

Four patients who were diagnosed as graft cholangiopathies and underwent retransplantation were chosen as the study group; another four patients who underwent liver transplantation during the same period and recovered normally six months after the operation were the control group. The serum levels of biochemical indicators were measured, the morphologic changes in intrahepatic bile ducts and cholangiocyte primary cilia were observed, and the ciliary marker (α-tubulin) and membrane proteins (polycystin-1, TPPV4) were detected by immunofluorescence analysis and Western blot.

RESULTS

In the study group, biliary structures were vague and some bile ducts disappeared in portal areas; some epithelial cells were lost; lots of collagen was deposited and many phlogocytes infiltrated; microliths were found in some ductal lumens; partial biliary epithelial cells were necrosed; primary cilia and microvilli disappeared. In the control group, the structures of intrahepatic bile ducts and biliary epithelial cells were integrated and the primary cilia were present.

CONCLUSIONS

The morphologic changes in biliary epithelial cells and the defects of cholangiocyte primary cilia have a close correlation with graft cholangiopathies in liver transplantation.

Restoring multidrug resistance-associated protein 3 attenuates cell proliferation in the polycystic kidney

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by abnormal proliferation of renal tubular epithelial cells, resulting in the loss of renal function. Despite identification of the genes responsible for ADPKD, few effective drugs are currently available for the disease. Thus finding additional effective drug targets is necessary. The functions of multidrug- resistance-associated protein 3 (MRP3) have been reported only in the field of drug resistance, and the renal functions of MRP3 are mostly unknown. In this study, we found that MRP3 was significantly downregulated in kidneys of human patients with ADPKD and polycystic kidney disease (PKD) mouse models. Our results suggest that downregulated MRP3 stimulated renal epithelial cell proliferation through the B-Raf/MEK/ERK signaling pathway. In contrast, we found that restoring MRP3 reduced cell proliferation and cystogenesis in vitro. These results suggest that the renal function of MRP3 is related to renal cell proliferation and cyst formation and that restoring MRP3 may be an effective therapeutic approach for PKD.

New treatments for autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease and results from mutations in PKD1 or PKD2. Cyst initiation and expansion arise from a combination of abnormal cell proliferation, fluid secretion and extracellular matrix defects and results in kidney enlargement and interstitial fibrosis. Since its first description over 200 years ago, ADPKD has been considered an untreatable condition and its management is limited to blood pressure reduction and symptomatic treatment of disease complications. Results of the recently reported TEMPO 3/4 trial thus represent a paradigm shift in demonstrating for the first time that cystic disease and loss of renal function can be slowed in humans. In this paper, we review the major therapeutic strategies currently being explored in ADPKD including a range of novel approaches in preclinical models. It is anticipated that the clinical management of ADPKD will undergo a revolution in the next decade with the translation of new treatments into routine clinical use.

Effects of combined administration of rapamycin, tolvaptan, and AEZ-131 on the progression of polycystic disease in PCK rats

Both experimental and clinical studies have suggested that any potential treatment of polycystic kidney disease (PKD) should start early and last for a long time to be effective, with unavoidable side reactions and considerable costs. The aim of the present study was to test how low doses of rapamycin (RAPA; 0.15 mg/kg ip for 4 days/wk), tolvaptan (TOLV; 0.005% in diet), or AEZ-131 (AEZ; a novel ERK inhibitor, 30 mg/kg for 3 days/wk by gavage), alone and in association, affect the progression of polycystic renal disease in PCK rats. Rats were treated for 8 wk starting at 4-6 wk of age. The efficacy of low doses of such drugs in inhibiting their respective targets was confirmed by immunoblot experiments. Compared with rats in the control (CON) group, RAPA treatment caused a significant reduction in cyst volume density (CVD; -19% vs. the CON group) and was numerically similar to that in TOLV-treated rats (-18%, not significiant), whereas AEZ treatment was not effective. RAPA + TOLV treatment resulted in a significantly lower CVD (-49% vs. the CON group) and was associated with a striking decrease in cAMP response element-binding protein phosphorylation, and similar data were detected in RAPA + AEZ-treated rats (-42%), whereas TOLV + AEZ treatment had virtually no effect. RAPA administration significantly lessened body weight gain, whereas TOLV administration resulted a mild increase in diuresis and a significant increase in cAMP urinary excretion. Histological data of tubular proliferation were in full agreement with CVD data. In conclusion, this study demonstrates that the association of low doses of RAPA, TOLV, and AEZ slows the progression of PKD with limited side effects, suggesting the use of combined therapies also in clinical trials.

Rationale and design of the DIPAK 1 study: a randomized controlled clinical trial assessing the efficacy of lanreotide to Halt disease progression in autosomal dominant polycystic kidney disease

BACKGROUND

There are limited therapeutic options to slow the progression of autosomal dominant polycystic kidney disease (ADPKD). Recent clinical studies indicate that somatostatin analogues are promising for treating polycystic liver disease and potentially also for the kidney phenotype. We report on the design of the DIPAK 1 (Developing Interventions to Halt Progression of ADPKD 1) Study, which will examine the efficacy of the somatostatin analogue lanreotide on preservation of kidney function in ADPKD.

STUDY DESIGN

The DIPAK 1 Study is an investigator-driven, randomized, multicenter, controlled, clinical trial.

SETTING & PARTICIPANTS

We plan to enroll 300 individuals with ADPKD and estimated glomerular filtration rate (eGFR) of 30-60 mL/min/1.73 m(2) who are aged 18-60 years.

INTERVENTION

Patients will be randomly assigned (1:1) to standard care or lanreotide, 120 mg, subcutaneously every 28 days for 120 weeks, in addition to standard care.

OUTCOMES

Main study outcome is the slope through serial eGFR measurements starting at week 12 until end of treatment for lanreotide versus standard care. Secondary outcome parameters include change in eGFR from pretreatment versus 12 weeks after treatment cessation, change in kidney volume, change in liver volume, and change in quality of life.

MEASUREMENTS

Blood and urine will be collected and questionnaires will be filled in following a fixed scheme. Magnetic resonance imaging will be performed for assessment of kidney and liver volume.

RESULTS

Assuming an average change in eGFR of 5.2 ± 4.3 (SD) mL/min/1.73 m(2) per year in untreated patients, 150 patients are needed in each group to detect a 30% reduction in the rate of kidney function loss between treatment groups with 80% power, 2-sided α = 0.05, and 20% protocol violators and/or dropouts.

LIMITATIONS

The design is an open randomized controlled trial and measurement of our primary end point does not begin at randomization.

CONCLUSIONS

The DIPAK 1 Study will show whether subcutaneous administration of lanreotide every 4 weeks attenuates disease progression in patients with ADPKD.

Polycystic liver disease: ductal plate malformation and the primary cilium

Polycystic livers are found in autosomal dominant polycystic kidney disease (ADPKD), caused by polycystic kidney disease (PKD)1 and PKD2 mutations in virtually all cases, and in isolated polycystic liver disease (PCLD), where 20% of cases are caused by mutations in Protein kinase C substrate 80K-H (PRKCSH) or SEC63. Loss of heterozygosity in single hepatoblasts leads to underlying cystogenic ductal plate malformations. Crucially, actual components driving this development remain elusive. Recent advances have unraveled the roles of transforming growth factor (TGF)-β, Notch and Wnt signaling, transcriptional regulators such as hepatocyte nuclear factor (HNF)6 and HNF1β, as well as cilium function in hepatobiliary organogenesis. In polycystic liver disease, mutation or defective co-translational processing of key elements required for primary cilium formation have been implicated. This review recapitulates liver patterning factors in hepatobiliary development and extracts molecular players in hepatic cystogenesis.

The use of lanreotide in polycystic kidney disease: a single-centre experience

The secretion of large volumes of fluid into cysts and changes in the structure and mobility of the cilia of the renal tubular epithelium can lead to nephromegaly. This in turn often causes a deterioration of kidney function and arterial hypertension. In recent clinical studies, somatostatin analogues have demonstrated efficacy in isolated polycystic liver disease and, to a lesser extent, in polycystic kidney disease. Since the publication of these clinical studies, several patients have been referred to us for somatostatin analogue treatment. Here, we report our experience with 6 patients who were treated with lanreotide autogel 120 mg every 4 weeks over 6, 12 or 18 months and were longitudinally followed using CT scans without contrast agents, to evaluate the total bilateral kidney volume. We observed a mean decrease in volume of 4%, with mild to moderate side effects.

HDAC6 is overexpressed in cystic cholangiocytes and its inhibition reduces cystogenesis

Polycystic liver disease (PLD) is a member of the cholangiopathies, a group of liver diseases in which cholangiocytes, the epithelia lining of the biliary tree, are the target cells. PLDs are caused by mutations in genes involved in intracellular signaling pathways, cell cycle regulation, and ciliogenesis, among others. We previously showed that cystic cholangiocytes have abnormal cell cycle profiles and malfunctioning cilia. Because histone deacetylase 6 (HDAC6) plays an important role in both cell cycle regulation and ciliary disassembly, we examined the role of HDAC6 in hepatic cystogenesis. HDAC6 protein was increased sixfold in cystic liver tissue and in cultured cholangiocytes isolated from both PCK rats (an animal model of PLD) and humans with PLD. Furthermore, pharmacological inhibition of HDAC6 by Tubastatin-A, Tubacin, and ACY-1215 decreased proliferation of cystic cholangiocytes in a dose- and time-dependent manner, and inhibited cyst growth in three-dimensional cultures. Importantly, ACY-1215 administered to PCK rats diminished liver cyst development and fibrosis. In summary, we show that HDAC6 is overexpressed in cystic cholangiocytes both in vitro and in vivo, and its pharmacological inhibition reduces cholangiocyte proliferation and cyst growth. These data suggest that HDAC6 may represent a potential novel therapeutic target for cases of PLD.

Osmoregulation, vasopressin, and cAMP signaling in autosomal dominant polycystic kidney disease

PURPOSE OF REVIEW

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent inherited nephropathy. This review will focus on the vasopressin and 3'-5'-cyclic adenosine monophosphate (cAMP) signaling pathways in ADPKD and will discuss how these insights offer new possibilities for the follow-up and treatment of the disease.

RECENT FINDINGS

Defective osmoregulation is an early manifestation of ADPKD and originates from both peripheral (renal effect of vasopressin) and central (release of vasopressin) components. Copeptin, which is released from the vasopressin precursor, may identify ADPKD patients at risk for rapid disease progression. Increased levels of cAMP in tubular cells, reflecting modifications in intracellular calcium homeostasis and abnormal stimulation of the vasopressin V2 receptor (V2R), play a central role in cystogenesis. Blocking the V2R lowers cAMP in cystic tissues, slows renal cystic progression and improves renal function in preclinical models. A phase III clinical trial investigating the effect of the V2R antagonist tolvaptan in ADPKD patients has shown that this treatment blunts kidney growth, reduces associated symptoms and slows kidney function decline when given over 3 years.

SUMMARY

These advances open perspectives for the understanding of cystogenesis in ADPKD, the mechanisms of osmoregulation, the role of polycystins in the brain, and the pleiotropic action of vasopressin.