Secondary and tertiary structure modeling reveals effects of novel mutations in polycystic liver disease genes PRKCSH and SEC63

Benign liver lesions 2022: Guideline for clinical practice of Associazione Italiana Studio del Fegato (AISF), Società Italiana di Radiologia Medica e Interventistica (SIRM), Società Italiana di Chirurgia (SIC), Società Italiana di Ultrasonologia in Medicina e Biologia (SIUMB), Associazione Italiana di Chirurgia Epatobilio-Pancreatica (AICEP), Società Italiana Trapianti d'Organo (SITO), Società Italiana di Anatomia Patologica e Citologia Diagnostica (SIAPEC-IAP) - Part I - Cystic lesions

Benign liver lesions are increasingly diagnosed in daily clinical practice due to the growing use of imaging techniques for the study of the abdomen in patients who have non-specific symptoms and do not have an increased risk of hepatic malignancy. They include simple or parasitic cysts and solid benign tumors which differ widely in terms of prevalence, clinical relevance, symptoms and natural history and often lead to significant clinical problems relating to diagnosis and clinical management. Following the need to have updated guidelines on the management of benign focal liver lesions, the Scientific Societies mainly involved in their management have promoted the drafting of a new dedicated document. This document was drawn up according to the present Italian rules and methodologies necessary to produce clinical, diagnostic, and therapeutic guidelines based on evidence. Here we present the first part of the guideline, concerning the characterization of focal hepatic lesions detected by ultrasound, and the diagnosis and clinical management of simple and parasitic hepatic cysts, and of polycystic liver disease.

Molecular Mechanisms of Isolated Polycystic Liver Diseases

Polycystic liver disease (PLD) is a rare autosomal dominant disorder including two genetically and clinically distinct forms: autosomal dominant polycystic kidney disease (ADPKD) and isolated polycystic liver disease (PCLD). The main manifestation of ADPKD is kidney cysts, while PCLD has predominantly liver presentations with mild or absent kidney cysts. Over the past decade, PRKCSH, SEC63, ALG8, and LRP5 have been candidate genes of PCLD. Recently, more candidate genes such as GANAB, SEC61B, and ALR9 were also reported in PCLD patients. This review focused on all candidate genes of PCLD, including the newly established novel candidate genes. In addition, we also discussed some other genes which might also contribute to the disease.

PRKCSH Alternative Splicing Involves in Silica-Induced Expression of Epithelial-Mesenchymal Transition Markers and Cell Proliferation

Background:

Mounting evidence suggests that alternative splicing is one of the ways for cells to adapt to environmental stress insults. The aim of this study was firstly to examine the effect of silica on the alternative splicing of lung fibrosis–associated genes.

Methods:

Microarray analysis was used to construct the alternative splicing profile. Functional experiments were conducted using Cell Counting Kit-8, cell cycle, apoptosis, and epithelial–mesenchymal transition (EMT) analyses. Alternative splicing variants were verified by quantitative real-time polymerase chain reaction (qRT-PCR) polymerase chain reaction method.

Results:

A total of 1850 genes that have alternative splices in response to silica insult were identified. PCDHB11, MALAT1, MT2A, RP11-126D17.1, and RP11-415I12.2 are the top 5 upregulated genes with occurrence of alternative splice, whereas NDE1, RNPEPL1, TREML2, CSF2RB, and PRKCSH are the top 5 downregulated genes with occurrence of alternative splice. Bioinformatic analysis showed these genes with the occurrence of alternative splice mainly are associated with EMT pathway, N-Glycan biosynthesis, and leukocyte transendothelial migration. Further study indicated that PRKCSH-2 knockdown promotes A549 cell proliferation potential by partially promoting EMT signals.

Conclusions:

Significant changes in alternative splicing of silicosis-associated genes occur in patients with silicosis in silica conditions. Our study provides basic founding for further investigation into the detail molecular mechanisms underlying silica-induced silicosis.

A Case Report of a Ventral Hernia Containing a Liver Cyst in a Patient with Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most commonly inherited renal disorder and the fourth most common cause of end-stage renal disease. ADPKD is a systemic disease with multiple extrarenal manifestations, including cystic involvement of other organs, such as the liver and pancreas, and connective tissue abnormalities. The prevalence of hernias is higher in patients with ADPKD. It has been hypothesized that these hernias are the result of abnormal extracellular matrix production and/or increased intra-abdominal pressure from the cyst burden. We present a case of a 56-year-old female with polycystic kidney disease who was admitted for an incarcerated ventral hernia. The patient presented with obstructive symptoms concerning for bowel impingement. The patient underwent operative management, and during the procedure, an incarcerated liver cyst was identified in the hernia sac. This was successfully reduced, and the hernia was repaired with mesh.

Clinical management of polycystic liver disease

A 41-year old female underwent a computed tomography (CT) scan in 2010 because of symptoms suggestive of appendicitis. Incidentally, multiple liver lesions characterised as cysts were detected. The presence of small to medium sized liver cysts (diameter between <1 cm and 4 cm) in all liver segments (>100 cysts) and absence of kidney cysts in the context of normal renal function led to the clinical diagnosis of autosomal dominant polycystic liver disease (ADPLD). Five years later she was referred to the outpatient clinic with increased abdominal girth, pain in the right upper abdomen and right flank, and early satiety. She had difficulties bending over and could neither cut her toenails nor tie her shoe laces. In her early twenties she had used oral contraception for five years. She has been pregnant twice. Clinical examination showed an enlarged liver reaching into the right pelvic region and crossing the midline of the abdomen. Laboratory testing demonstrated increased gamma-glutamyl transferase (80 IU/L, normal <40 IU/L) and alkaline phosphatase (148 IU/L, normal <100 IU/L) levels. Bilirubin, albumin and coagulation times were within the normal range. A new CT scan in 2015 was compatible with an increased number and size of liver cysts. The diameter of cysts varied between <1 cm and 6 cm (anatomic distribution shown [Fig. 2B]). There were no signs of hepatic venous outflow obstruction, portal hypertension or compression on the biliary tract. Height-adjusted total liver volume (htTLV) increased from 2,667 ml/m in 2012 to 4,047 ml/m in 2015 (height 172 cm). The case we present here is not uncommon, and prompts several relevant questions.

Waitlisted Candidates With Polycystic Liver Disease Are More Likely to be Transplanted Than Those With Chronic Liver Failure

BACKGROUND

Polycystic liver disease (PCLD) is characterized by cystic replacement of the hepatic parenchyma, leading to hepatic dysfunction, portal hypertension, and hepatomegaly. Patients with liver dysfunction and/or symptomatic disease are eligible for liver transplantation. However, little is known about these patients' waitlist outcomes relative to others with chronic liver disease.

METHODS

We used Organ Procurement and Transplantation Network/United Network for Organ Sharing data from February 27, 2002 to December 31, 2015 to compare waitlist outcomes of adult patients with PCLD to those with chronic liver failure (CLF) and hepatocellular carcinoma.

RESULTS

The study cohort included 620 patients with PCLD, 18 240 patients with hepatocellular carcinoma, and 98 567 patients with CLF. Compared with CLF patients, PCLD patients had significantly lower bilirubin and international normalized ratio at waitlisting, and less ascites and encephalopathy. However, they were significantly more likely to have severe chronic kidney disease. Moreover, patients with PCLD were more than 70% more likely to be transplanted compared with patients with CLF (odds ratio, 1.72; 95% confidence interval, 1.46-2.02) and had significantly longer posttransplant survival (P < 0.001). PCLD patients with exceptions were 5.7 times more likely to be transplanted than those without (odds ratio, 5.67; 95% confidence interval, 3.95-8.15) and measures of hepatic/renal dysfunction were inversely associated with the receipt of exceptions.

CONCLUSIONS

Despite having more preserved liver synthetic function than patients with CLF on the waitlist, patients with PCLD are preferentially transplanted because they frequently receive exception points in an unstandardized fashion.

Genetics and mechanisms of hepatic cystogenesis

Polycystic liver disease (PLD) is a heterogeneous genetic condition. PKD1 and PKD2 germline mutations are found in patients with autosomal dominant polycystic kidney disease (ADPKD). Autosomal dominant polycystic liver disease (ADPLD) is associated with germline mutations in PRKCSH, SEC63, LRP5, and recently ALG8 and SEC61. GANAB mutations are found in both patient groups. Loss of heterozygosity of PLD-genes in cyst epithelium contributes to the development of hepatic cysts. A genetic interaction network is implied in hepatic cystogenesis that connects the endoplasmic glycoprotein control mechanisms and polycystin expression and localization. Wnt signalling could be the major downstream signalling pathway that results in hepatic cyst growth. PLD in ADPLD and ADPKD probably results from changes in one common final pathway that initiates cyst growth. This article is part of a Special Issue entitled: Cholangiocytes in Health and Diseaseedited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

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.

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.

CYP1A1 and GSTP1 gene variations in breast cancer: a systematic review and case-control study

In first part of this study, a systematic review was designed to explore the involvement of CYP1A1 and GSTP1 genes in breast cancerogenesis. Based on systematic review, we designed a study to screen CYP1A1 and GSTP1 genes for mutation and their possible association with breast carcinogenesis. A total of 400 individuals were collected and analyzed by PCR-SSCP. After sequence analysis of coding region of CYP1A1 we identified eleven mutations in different exons of respective gene. Among these eleven mutations, ~3 folds increased breast cancer risk was found associated with Asp82Glu mutation (OR 2.99; 95% CI 1.26-7.09), with Ser83Thr mutation (OR 2.99; 95% CI 1.26-7.09) and with Glu86Ala mutation (OR 3.18; 95% CI 1.27-7.93) in cancer patients compared to controls. Furthermore, ~4 folds increase in breast cancer risk was found associated with Asp347Glu, Phe398Tyr and 5178delT mutations (OR 3.92; 95% CI 1.35-11.3) in patients compared to controls. The sequence analysis of GSTP1 resulted in identification of total five mutations. Among these five mutations, ~3 folds increase in breast cancer risk was observed associated with 1860G>A mutation, with 1861-1876delCAGCCCTCTGGAGTGG mutation (OR 2.70; 95% CI 1.10-6.62) and with 1861C>A mutation (OR 2.97; 95% CI 1.01-8.45) in cancer patients compared to controls. Furthermore, ~5 folds increase in breast cancer risk was associated with 1883G>T mutation (OR 4.75; 95% CI 1.46-15.3) and ~6 folds increase in breast cancer risk was found associated with Iso105Val mutation (OR 6.43; 95% CI 1.41-29.3) in cancer patients compared to controls. Our finding, based on systematic review and experimental data suggest that the polymorphic CYP1A1 and GSTP1 genes may contribute to risk of developing breast cancer.

Severe Polycystic Liver Disease Is Not Caused by Large Deletions of the PRKCSH Gene

BACKGROUND

Isolated polycystic liver disease (ADPLD) is an autosomal dominant Mendelian disorder. Heterozygous PRKCSH (where PRKCSH is protein kinase C substrate 80K-H (80 kDa protein, heavy chain; MIM*177060) mutations are the most frequent cause. Routine molecular testing using Sanger sequencing identifies pathogenic variants in the PRKCSH (15%) and SEC63 (where SEC63 is Saccharomyces cerevisiae homolog 63 (MIM*608648); 6%) genes, but about approximately 80% of patients meeting the clinical ADPLD criteria carry no PRKCSH or SEC63 mutation. Cyst tissue often shows somatic deletions with loss of heterozygosity that was recently recognized as a general mechanism in ADPLD. We hypothesized that germline deletions in the PRKCSH gene may be responsible for hepatic cystogenesis in a significant number of mutation-negative ADPLD patients.

METHODS

In this study, we designed a multiplex ligation-dependent probe amplification (MLPA) assay to screen for deletions of PRKCSH exons. Genomic DNA from 60 patients with an ADPLD phenotype was included.

RESULTS

MLPA analysis detected no exon deletions in mutation-negative ADPLD patients.

CONCLUSION

Large copy number variations on germline level are not present in patients with a clinical diagnosis of ADPLD. MLPA analysis of the PRKCSH gene should not be considered as a diagnostic method to explain hepatic cystogenesis.

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.

Polycystic liver disease: an overview of pathogenesis, clinical manifestations and management

Polycystic liver disease (PLD) is the result of embryonic ductal plate malformation of the intrahepatic biliary tree. The phenotype consists of numerous cysts spread throughout the liver parenchyma. Cystic bile duct malformations originating from the peripheral biliary tree are called Von Meyenburg complexes (VMC). In these patients embryonic remnants develop into small hepatic cysts and usually remain silent during life. Symptomatic PLD occurs mainly in the context of isolated polycystic liver disease (PCLD) and autosomal dominant polycystic kidney disease (ADPKD). In advanced stages, PCLD and ADPKD patients have massively enlarged livers which cause a spectrum of clinical features and complications. Major complaints include abdominal pain, abdominal distension and atypical symptoms because of voluminous cysts resulting in compression of adjacent tissue or failure of the affected organ. Renal failure due to polycystic kidneys and non-renal extra-hepatic features are common in ADPKD in contrast to VMC and PCLD. In general, liver function remains prolonged preserved in PLD. Ultrasonography is the first instrument to assess liver phenotype. Indeed, PCLD and ADPKD diagnostic criteria rely on detection of hepatorenal cystogenesis, and secondly a positive family history compatible with an autosomal dominant inheritance pattern. Ambiguous imaging or screening may be assisted by genetic counseling and molecular diagnostics. Screening mutations of the genes causing PCLD (PRKCSH and SEC63) or ADPKD (PKD1 and PKD2) confirm the clinical diagnosis. Genetic studies showed that accumulation of somatic hits in cyst epithelium determine the rate-limiting step for cyst formation. Management of adult PLD is based on liver phenotype, severity of clinical features and quality of life. Conservative treatment is recommended for the majority of PLD patients. The primary aim is to halt cyst growth to allow abdominal decompression and ameliorate symptoms. Invasive procedures are required in a selective patient group with advanced PCLD, ADPKD or liver failure. Pharmacological therapy by somatostatin analogues lead to beneficial outcome of PLD in terms of symptom relief and liver volume reduction.

microRNA biomarkers in cystic diseases

microRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by targeting the 3’-untranslated region of multiple target genes. Pathogenesis results from defects in several gene sets; therefore, disease progression could be prevented using miRNAs targeting multiple genes. Moreover, recent studies suggest that miRNAs reflect the stage of the specific disease, such as carcinogenesis. Cystic diseases, including polycystic kidney disease, polycystic liver disease, pancreatic cystic disease, and ovarian cystic disease, have common processes of cyst formation in the specific organ. Specifically, epithelial cells initiate abnormal cell proliferation and apoptosis as a result of alterations to key genes. Cysts are caused by fluid accumulation in the lumen. However, the molecular mechanisms underlying cyst formation and progression remain unclear. This review aims to introduce the key miRNAs related to cyst formation, and we suggest that miRNAs could be useful biomarkers and potential therapeutic targets in several cystic diseases. [BMB Reports 2013; 46(7):338-345]

Polycystin-1: a master regulator of intersecting cystic pathways

Autosomal dominant polycystic kidney disease (ADPKD) is the most common potentially lethal monogenic disorder, with more than 12 million cases worldwide. The two causative genes for ADPKD, PKD1 and PKD2, encode protein products polycystin-1 (PC1) and polycystin-2 (PC2 or TRPP2), respectively. Recent data have shed light on the role of PC1 in regulating the severity of the cystic phenotypes in ADPKD, autosomal recessive polycystic kidney disease (ARPKD), and isolated autosomal dominant polycystic liver disease (ADPLD). These studies showed that the rate for cyst growth was a regulated trait, a process that can be either sped up or slowed down by alterations in functional PC1. These findings redefine the previous understanding that cyst formation occurs as an 'on-off' process. Here, we review these and other related studies with an emphasis on their translational implications for polycystic diseases.

Current management of noninfectious hepatic cystic lesions: A review of the literature

Nonparasitic hepatic cysts consist of a heterogeneous group of disorders, which differ in etiology, prevalence, and manifestations. With improving diagnostic techniques, hepatic cysts are becoming more common. Recent advancements in minimally invasive technology created a new Era in the management of hepatic cystic disease. Herein, the most current recommendations for management of noninfectious hepatic cysts are described, thereby discussing differential diagnosis, new therapeutic modalities and outcomes.

Evaluation of hepatic cystic lesions

Hepatic cysts are increasingly found as a mere coincidence on abdominal imaging techniques, such as ultrasonography (USG), computed tomography (CT) and magnetic resonance imaging (MRI). These cysts often present a diagnostic challenge. Therefore, we performed a review of the recent literature and developed an evidence-based diagnostic algorithm to guide clinicians in characterising these lesions. Simple cysts are the most common cystic liver disease, and diagnosis is based on typical USG characteristics. Serodiagnostic tests and microbubble contrast-enhanced ultrasound (CEUS) are invaluable in differentiating complicated cysts, echinococcosis and cystadenoma/cystadenocarcinoma when USG, CT and MRI show ambiguous findings. Therefore, serodiagnostic tests and CEUS reduce the need for invasive procedures. Polycystic liver disease (PLD) is arbitrarily defined as the presence of > 20 liver cysts and can present as two distinct genetic disorders: autosomal dominant polycystic kidney disease (ADPKD) and autosomal dominant polycystic liver disease (PCLD). Although genetic testing for ADPKD and PCLD is possible, it is rarely performed because it does not affect the therapeutic management of PLD. USG screening of the liver and both kidneys combined with extensive family history taking are the cornerstone of diagnostic decision making in PLD. In conclusion, an amalgamation of these recent advances results in a diagnostic algorithm that facilitates evidence-based clinical decision making.

Diagnosis and management of polycystic liver disease

Polycystic liver disease (PLD) is arbitrarily defined as a liver that contains >20 cysts. The condition is associated with two genetically distinct diseases: as a primary phenotype in isolated polycystic liver disease (PCLD) and as an extrarenal manifestation in autosomal dominant polycystic kidney disease (ADPKD). Processes involved in hepatic cystogenesis include ductal plate malformation with concomitant abnormal fluid secretion, altered cell-matrix interaction and cholangiocyte hyperproliferation. PLD is usually a benign disease, but can cause debilitating abdominal symptoms in some patients. The main risk factors for growth of liver cysts are female sex, exogenous oestrogen use and multiple pregnancies. Ultrasonography is very useful for achieving a correct diagnosis of a polycystic liver and to differentiate between ADPKD and PCLD. Current radiological and surgical therapies for symptomatic patients include aspiration-sclerotherapy, fenestration, segmental hepatic resection and liver transplantation. Medical therapies that interact with regulatory mechanisms controlling expansion and growth of liver cysts are under investigation. Somatostatin analogues are promising; several clinical trials have shown that these drugs can reduce the volume of polycystic livers. The purpose of this Review is to provide an update on the diagnosis and management of PLD with a focus on literature published in the past 4 years.

Mutation of sec63 in zebrafish causes defects in myelinated axons and liver pathology

Mutations in SEC63 cause polycystic liver disease in humans. Sec63 is a member of the endoplasmic reticulum (ER) translocon machinery, although it is unclear how mutations in SEC63 lead to liver cyst formation in humans. Here, we report the identification and characterization of a zebrafish sec63 mutant, which was discovered in a screen for mutations that affect the development of myelinated axons. Accordingly, we show that disruption of sec63 in zebrafish leads to abnormalities in myelinating glia in both the central and peripheral nervous systems. In the vertebrate nervous system, segments of myelin are separated by the nodes of Ranvier, which are unmyelinated regions of axonal membrane containing a high density of voltage-gated sodium channels. We show that sec63 mutants have morphologically abnormal and reduced numbers of clusters of voltage-gated sodium channels in the spinal cord and along peripheral nerves. Additionally, we observed reduced myelination in both the central and peripheral nervous systems, as well as swollen ER in myelinating glia. Markers of ER stress are upregulated in sec63 mutants. Finally, we show that sec63 mutants develop liver pathology. As in glia, the primary defect, detectable at 5 dpf, is fragmentation and swelling of the ER, indicative of accumulation of proteins in the lumen. At 8 dpf, ER swelling is severe; other pathological features include disrupted bile canaliculi, altered cytoplasmic matrix and accumulation of large lysosomes. Together, our analyses of sec63 mutant zebrafish highlight the possible role of ER stress in polycystic liver disease and suggest that these mutants will serve as a model for understanding the pathophysiology of this disease and other abnormalities involving ER stress.

Loss of heterozygosity is present in SEC63 germline carriers with polycystic liver disease

Polycystic liver disease (PCLD) is an autosomal dominant disorder characterised by multiple fluid filled cysts in the liver. This rare disease is caused by heterozygous germline mutations in PRKCSH and SEC63. We previously found that, in patients with a PRKCSH mutation, over 76% of the cysts acquired a somatic 'second-hit' mutation in the wild type PRKCSH allele. We hypothesise that somatic second-hit mutations are a general mechanism of cyst formation in PCLD which also plays a role in PCLD patients carrying a SEC63 germline mutation. We collected cyst epithelial cells from 52 liver cysts from three different SEC63 patients using laser microdissection. DNA samples were sequenced to identify loss of heterozygosity (LOH) mutations and other somatic mutations in cyst epithelial DNA. We discovered somatic SEC63 mutations in patient 3 (1/14 cysts), but not in patient 1 and 2 (38 cysts). Upon review we found that the germline mutation of patient 1 and 2 (SEC63 c.1703_1705delAAG) was present in the same frequency in DNA samples from healthy controls, suggesting that this variant is not causative of PCLD. In conclusion, as somatic second-hit mutations also play a role in cyst formation in patients with a SEC63 germline mutation, this appears to be a general mechanism of cyst formation in PCLD.

Polycystic liver disease: a clinical review

Polycystic liver disease rarely occurs in isolation as part of autosomal dominant polycystic liver disease, but more commonly, it exists as an extra-renal manifestation of autosomal dominant polycystic kidney disease. The pathogenesis of polycystic liver disease involves defects in the primary cilium of the cholangiocyte, with genetic mutations that impair key proteins integral to the complex functioning of cilia. While most patients are asymptomatic and require no intervention aside from reassurance and genetic counseling, in a minority of patients, polycystic liver disease creates a myriad of symptoms from the compressive effects of enlarged cysts, and can even cause malnutrition and liver decompensation in the severest of cases. In patients with symptomatic disease, a variety of interventional radiology or surgical techniques can be considered, including aspiration with sclerotherapy of a dominant cyst, fenestration, segmental hepatic resection, and even liver transplantation. Although there are no curative medical options for polycystic liver disease, somatostatin analogs hold promise and have shown minimal efficacy in human studies. However, further research is needed to develop more efficacious medical treatments.

Boy with autosomal recessive polycystic kidney and autosomal dominant polycystic liver disease

BACKGROUND

Autosomal recessive polycystic kidney disease (ARPKD) shows a great phenotypic variability between patients, ranging from perinatal demise to mildly affected adults. Autosomal dominant polycystic liver disease (PCLD) does not manifest in childhood.

CASE-DIAGNOSIS/TREATMENT

A boy was reported with the co-occurrence of ARPKD and PCLD. He presented at the age of 16 days with pyelonephritis and urosepsis. Subsequent investigations showed enlarged kidneys and hyperechogenic renal medulla and liver parenchyma. Genetic analysis revealed compound heterozygous mutations in the PKHD1 gene (p.Arg496X and p.Ser1862Leu). After his mother was diagnosed with PCLD, the finding of a liver cyst on ultrasound prompted analysis of the PRKCSH gene, revealing a missense mutation (p.Arg139His). At the most recent follow-up at 13 years of age, the patient's course and clinical examination was uneventful with normal renal and liver function without evidence of portal hypertension.

CONCLUSIONS

The patient with ARPKD and PCLD has so far demonstrated a benign clinical outcome, consistent with the great phenotypic variability of ARPKD and, apart from the liver cyst, asymptomatic manifestation of PCLD in childhood. However, close long-term follow-up is mandatory.

Secondary, somatic mutations might promote cyst formation in patients with autosomal dominant polycystic liver disease

BACKGROUND & AIMS

Heterozygous germline mutations in PRKCSH cause autosomal dominant polycystic liver disease (PCLD), but it is not clear how they lead to cyst formation. We investigated whether mutations in cyst epithelial cells and corresponding loss of the PRKCSH gene product (hepatocystin) contributed to cyst development.

METHODS

Liver cyst material was collected through laparoscopic cyst fenestration from 8 patients with PCLD who had a heterozygous germline mutation in PRKCSH. Tissue sections from 71 cysts (2-14 per patient) were obtained for hepatocystin staining and mutation analysis. Cyst epithelium was acquired using laser microdissection; DNA was isolated and analyzed for loss of heterozygosity (LOH) and somatic mutations using restriction analysis and sequencing. Common single nucleotide polymorphisms (SNPs) in a 70-kilobase region surrounding the germline mutation were used to determine variations in the genomic region with LOH.

RESULTS

The wild-type allele of PRKCSH was lost (LOH) in 76% of cysts (54/71). Hepatocystin was not detected in cyst epithelia with LOH, whereas heterozygous cysts still expressed hepatocystin. The variation observed in the LOH region analysis indicates that cysts develop independently. We also detected somatic mutations in PRKCSH in 17% (2/12) of the cysts without LOH. Trans-heterozygous mutations in SEC63 were not observed.

CONCLUSIONS

Among patients with PCLD who have a heterozygous germline mutation in PRKCSH, we found secondary, somatic mutations (second hits) in more than 76% of the liver cyst epithelia. PCLD is recessive at the cellular level, and loss of functional PRKCSH is an important step in cystogenesis.

Systematic review: the pathophysiology and management of polycystic liver disease

BACKGROUND

Polycystic liver diseases (PCLD) represent a group of genetic disorders in which cysts occur solely in the liver, or together with renal cysts. Most of the patients with PCLD are asymptomatic, however, in some patients, expansion of liver cysts causes invalidating abdominal symptoms.

AIM

To provide a systemic review on the pathophysiology and management of PCLD.

METHODS

A PubMed search was undertaken to identify relevant literature using search terms including polycystic liver disease, pathophysiology, surgical and medical management.

RESULTS

The most common complication in patients with PCLD is extensive hepatomegaly, which may lead to malnutrition and can be lethal. Conservative surgical approaches are only partially effective and do not change the natural course of the disease. Liver transplantation has been successfully performed in PCLD, however, in an era of organ shortage, medical management needs to be evaluated. A better understanding of the pathophysiology and the availability of animal models have already identified promising drugs. Abnormalities in cholangiocyte proliferation/apoptosis and enhanced fluid secretion are key factors in the pathophysiology. It has been demonstrated in rodents and in humans that somatostatin analogues diminish liver volume. The role of the inhibitors of the mammalian target of rapamycin (mTOR) in the management of PCLD is still under investigation.

CONCLUSIONS

The exact pathophysiology of polycystic liver disease still remains unclear. In symptomatic patients, none of the currently available surgical options except liver transplantation have been shown to change the natural course of the disease. The use of somatostatin analogues has been shown to diminish liver volume.

Somatostatin analogues for treatment of polycystic liver disease

PURPOSE OF REVIEW

The present review summarizes the existing knowledge on polycystic liver disease (PCLD) and highlights the progress made in medical treatment for this condition in the past year.

RECENT FINDINGS

PCLD is associated with autosomal dominant polycystic kidney disease (ADPKD) and autosomal dominant PCLD. Signaling pathways of adenosine 3',5'-cyclic monophosphate (cAMP) and mammalian target of rapamycin (mTOR) are aberrantly regulated in polycystic livers and promote hepatic cystogenesis. Somatostatin analogues reduce intracellular cAMP, and this might prevent fluid accumulation in hepatic cysts. Several clinical trials published over the last year now show that somatostatin analogues when given for 6-12 months in patients with ADPKD and PCLD decrease total liver volume, attenuate polycystic kidney volume, and improve perception of health. In two recent studies mTOR inhibitors failed to halt the progression of ADPKD. It is still too early to recommend to start somatostatin analogues in PCLD and definitive answers should come from future clinical trials.

SUMMARY

Somatostatin analogues are promising new medical drug options in the treatment of PCLD. However, more needs to be elucidated with regard to molecular mechanisms in hepatic cystogenesis, the uncertainty who will respond to therapy and long-term outcomes.

Patients with isolated polycystic liver disease referred to liver centres: clinical characterization of 137 cases

BACKGROUND AND AIM

Isolated polycystic liver disease (PCLD) is characterized by the presence of multiple cysts in the liver in the absence of polycystic kidneys. The clinical profile of PCLD is poorly defined and we set up a study for the clinical characteristics of PCLD.

METHODS

We collected clinical data on 188 PCLD patients (defined as >10 liver cysts) from five tertiary referral centres, and 137 patients were selected for the purpose of this study. We performed molecular analysis of the PCLD associated genes PRKCSH and SEC63 in 91 patients.

RESULTS

A total of 118 (86%) patients were female. The majority of patients (88%) had >20 cysts. The median age at diagnosis was 47 years (range 23-84). 37 (41%) patients carried a mutation. Clinical symptoms at presentation were present in 111 (84%) patients. γ-glutamyl transferase was elevated to 1.4 times upper limit of normal (interquartile range 1.0-2.7). The presence of a mutation and female gender predicted a more severe course: female patients were 9 years younger at the time of diagnosis (47 years; range 23-84) and 91% had symptoms (P<0.01); likewise, mutation carriers were younger at presentation (39 years; range 35-48) and 95% of this cohort had symptoms (P<0.01). During follow-up [median 8.2 years (range 0-35)], 10% of untreated and 51% of treated patients developed complications. Mortality in this cohort was 8%, but only 2% died of PCLD-related causes. 58% of patients were treated a median of 2 years (range 0-25) after diagnosis.

CONCLUSION

Symptomatic PCLD patients are mainly females. Females and mutation carriers were younger at diagnosis and had a more severe course of disease.