Human parietal epithelial cells (PECs) and proteinuria in lupus nephritis: a role for ClC-5, megalin, and cubilin?

BACKGROUND

Parietal epithelial cells are a heterogeneous population of cells located on Bowman's capsule. These cells are known to internalize albumin with a still undetermined mechanism, although albumin has been shown to induce phenotypic changes in parietal epithelial cells. Proximal tubular cells are the main actors in albumin handling via the macromolecular complex composed by ClC-5, megalin, and cubilin. This study investigated the role of ClC-5, megalin, and cubilin in the parietal epithelial cells of kidney biopsies from proteinuric lupus nephritis patients and control subjects and identified phenotypical changes occurring in the pathological milieu.

METHODS

Immunohistochemistry and immunofluorescence analyses for ClC-5, megalin, cubilin, ANXA3, podocalyxin, CD24, CD44, HSA, and LTA marker were performed on 23 kidney biopsies from patients with Lupus Nephritis and 9 control biopsies (obtained from nephrectomies for renal cancer).

RESULTS

Two sub-populations of hypertrophic parietal epithelial cells ANXA3+/Podocalyxin-/CD44-, both expressing ClC-5, megalin, and cubilin and located at the tubular pole, were identified and characterized: the first one, CD24+/HSA-/LTA- had characteristics of human adult parietal epithelial multipotent progenitors, the second one, CD24-/LTA+/HSA+ committed to become phenotypically proximal tubular cells. The number of glomeruli presenting hypertrophic parietal epithelial cells positive for ClC-5, megalin, and cubilin were significantly higher in lupus nephritis patients than in controls.

CONCLUSIONS

Our results may provide further insight into the role of hypertrophic parietal epithelial cells located at the tubular pole and their possible involvement in protein endocytosis in lupus nephritis patients. These data also suggest that the presence of hypertrophic parietal epithelial cells in Bowman's capsule represents a potential resource for responding to protein overload observed in other glomerulonephritis.

Emerging Perspectives on the Rare Tubulopathy Dent Disease: Is Glomerular Damage a Direct Consequence of ClC-5 Dysfunction?

Dent disease (DD1) is a rare tubulopathy caused by mutations in the CLCN5 gene. Glomerulosclerosis was recently reported in DD1 patients and ClC-5 protein was shown to be expressed in human podocytes. Nephrin and actin cytoskeleton play a key role for podocyte functions and podocyte endocytosis seems to be crucial for slit diaphragm regulation. The aim of this study was to analyze whether ClC-5 loss in podocytes might be a direct consequence of the glomerular damage in DD1 patients. Three DD1 kidney biopsies presenting focal global glomerulosclerosis and four control biopsies were analyzed by immunofluorescence (IF) for nephrin and podocalyxin, and by immunohistochemistry (IHC) for ClC-5. ClC-5 resulted as down-regulated in DD1 vs. control (CTRL) biopsies in both tubular and glomerular compartments (p < 0.01). A significant down-regulation of nephrin (p < 0.01) in DD1 vs. CTRL was demonstrated. CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats/Caspase9) gene editing of CLCN5 in conditionally immortalized human podocytes was used to obtain clones with the stop codon mutation p.(R34Efs*14). We showed that ClC-5 and nephrin expression, analyzed by quantitative Reverse Transcription/Polymerase Chain Reaction (qRT/PCR) and In-Cell Western (ICW), was significantly downregulated in mutant clones compared to the wild type ones. In addition, F-actin staining with fluorescent phalloidin revealed actin derangements. Our results indicate that ClC-5 loss might alter podocyte function either through cytoskeleton disorganization or through impairment of nephrin recycling.

The lesson learned from the new c.2547-1G>T mutation combined with p.R854Q:when a type 2N mutation reveals a quantitative von Willebrand factor defect

Type 2N is a rare von Willebrand disease (VWD) variant involving an impairment in the FVIII carrier function of von Willebrand factor (VWF). It has a phenotype that mimics hemophilia A, and FVIII binding to VWF (VWF:FVIIIB) is tested to differentiate between the two disorders. Type 2N VWF defects may also be associated with quantitative VWF mutations (type 2N/type 1), further complicating the identification of cases. We report on a new quantitative VWF mutation (c.2547-1G>T) revealed by a p.R854Q type 2N mutation acting as homozygous despite being carried as a heterozygous defect. The proband had near-normal VWF levels (initially ruling out a defective VWF synthesis) and slightly reduced FVIII levels, while a VWF:FVIIIB test showed significantly reduced binding. Routine tests on type 2N homozygotes or heterozygotes combined with quantitative VWF defects in our cohort showed reduced FVIII levels in both groups, but it was only in the former that the FVIII/VWF:Ag ratio was always significantly reduced. The two tests are therefore not enough to identify all forms of type 2N VWD. While relatives of type 2N homozygotes usually have normal FVIII levels and FVIII/VWF:Ag ratios, relatives of type 2N/type 1 may have high FVIII/VWF:Ag ratios, but their VWF:FVIIIB and/or VWF:FVIIIB/VWF:Ag ratios are always low. Measuring FVIII and VWF levels may therefore suggest type 2N VWD in patients carrying type 2N mutations alone, but not in type 2N combined with quantitative VWF defects. The VWF:FVIIIB test should consequently always be included when exploring VWF function, whatever VWD patient’s phenotype.

Genotype Phenotype Correlation in Dent Disease 2 and Review of the Literature: OCRL Gene Pleiotropism or Extreme Phenotypic Variability of Lowe Syndrome?

Dent disease is a rare X-linked renal tubulopathy due to CLCN5 and OCRL (DD2) mutations. OCRL mutations also cause Lowe syndrome (LS) involving the eyes, brain and kidney. DD2 is frequently described as a mild form of LS because some patients may present with extra-renal symptoms (ESs). Since DD2 is a rare disease and there are a low number of reported cases, it is still unclear whether it has a clinical picture distinct from LS. We retrospectively analyzed the phenotype and genotype of our cohort of 35 DD2 males and reviewed all published DD2 cases. We analyzed the distribution of mutations along the OCRL gene and evaluated the type and frequency of ES according to the type of mutation and localization in OCRL protein domains. The frequency of patients with at least one ES was 39%. Muscle findings are the most common ES (52%), while ocular findings are less common (11%). Analysis of the distribution of mutations revealed (1) truncating mutations map in the PH and linker domain, while missense mutations map in the 5-phosphatase domain, and only occasionally in the ASH-RhoGAP module; (2) five OCRL mutations cause both DD2 and LS phenotypes; (3) codon 318 is a DD2 mutational hot spot; (4) a correlation was found between the presence of ES and the position of the mutations along OCRL domains. DD2 is distinct from LS. The mutation site and the mutation type largely determine the DD2 phenotype.

MO073HISTOLOGICAL PREDICTORS OF PROTEINURIA AND RENAL OUTCOMES IN PRIMARY MEMBRANOUS NEPHROPATHY: IS INTERSTITIAL FIBROSIS THE MAIN CHARACTER?

Background and Aims

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome in older white adults, with an incidence of 12 cases per millions of people per year. Primary MN (PMN, 75%-80% of MNs) is an organ-specific autoimmune disease caused by antibodies anti-PLA2R and anti-THSD7A. Regardless of treatment one third of patients progresses to end-stage renal disease and two third develop non-progressive chronic kidney disease. Renal biopsy is the gold standard for MN diagnosis. Several clinical and biochemical markers have been associated with the risk of progressive loss of kidney function while contrasting results have been obtained by the few studies which have examined the prognostic value of histologic findings.

In this study the clinical outcome of patients with PMN has been considered based on the prognostic value of histological findings.

Method

Forty-nine patients with PMN of our Nephrology Unit at Padova University Hospital from 2003 to 2018 were considered. 16 patients were excluded from the study due to missing data. Age, comorbidities, proteinuria (g/day) and renal function (eGFR, CKD-EPI) were collected. eGFR decline and decrease of proteinuria were used as clinical outcomes. The follow-up was considered from renal biopsy to the last visit (in absence of GFR decline or decrease in proteinuria).

Histological grading (0-3) was assigned to parameters (glomerulosclerosis (GS), tubular atrophy (TA), interstitial fibrosis (IF), vascular hyalinosis (VH)) and were evaluated separately or in combination (as GSTIV score). Morphometric analysis was used to quantify IF and expressed in percentage as the mean of area covered by pixel. Statistical analysis was performed using Fisher’s exact test and Mann-Whitney U-test where appropriate. Cox regression analyses (univariate and multivariate) were performed to identify variables associated with both renal outcomes and p&lt;0.05 was considered as significant.

ROC curves were used to determine interstitial fibrosis cut-off values predictive for both outcomes. Area under the curve (AUC) between 0.8 and 1.0 was considered as significant. Diagnostic accuracy was assessed by Specificity (Sp), Sensibility (Se), positive (PPV) and negative (NPV) predictive values and positive (LR+) and negative (LR-) likelihood ratios.

Results

Patients with no decrease of proteinuria had a greater degree of IF vs those with a full response (p=0.006).

Univariate Cox analyses identified age ≥65 years (HR 4.92), pre-existing CKD (HR 12.98) and IF (HR3.05) as significant predictors of renal function decline in all patients. Multivariate Cox analysis confirmed these variables (age ≥65 years HR 3.05, CKD HR 6.35, IF HR 3.03). In patients without CKD only IF was significantly associated with eGFR decline in both Cox univariate and multivariate analysis (HR 4.34 and 5.05 respectively).

ROC analysis showed that IF threshold of 17.80% identified patients with eGFR reduction (AUC 0.65, Se 0.50, Sp 0.79, PPV 0.75, NPV 0.45, LR+ 2.38, LR-0.63) and IF threshold of 18.04% the lack of proteinuria reduction (AUC 0.78, Se 0.70, Sp 0.83, PPV 0.67, NPV 0.80, LR+ 4.12, LR- 0.36).

Conclusion

Our study shows that IF could be used as a histologic predictor of renal and proteinuria outcomes. Biopsy report should therefore also include quantitative IF data that could be helpful for the choice of a more appropriate therapeutic approach.

MO012ACE2 AND SARS-COV-2 INFECTION RISK: INSIGHTS FROM PATIENTS WITH TWO RARE GENETIC TUBULOPATHIES, GITELMAN‘S AND BARTTER’S SYNDROMES

Background and Aims

COVID-19 is spreading globally with Angiotensin Converting Enzyme (ACE)-2 serving as the entry point of SARS-CoV-2 virus. This raised concerns how ACE2 and Renin-Angiotensin (Ang)-System (RAS) are to be dealt with given their involvement in COVID-19’s morbidity and mortality. Specifically, increased ACE2 expression in response to treatment with ACE inhibitors (ACEi) and Ang II receptor blockers (ARBs) might theoretically increase COVID-19 risk by increasing SARS-CoV-2 binding sites. However, ACE2 is part of the protective counter‐regulatory ACE2‐Ang1‐7-MasR axis, which opposes the classical ACE-AngII-AT1R regulatory axis. We used Gitelman’s and Bartter’s syndromes (GS/BS) patients, rare genetic tubulopathies, who have endogenously increased levels of ACE2, to provide more insight on these issues.

Method

128 genetically confirmed GS/BS patients, living in Lombardia, Emilia Romagna and Veneto, the Northern Italy hot spots for COVID-19, were surveyed via telephone survey regarding COVID-19.

Results

The survey found no COVID-19 infection and absence of COVID-19 symptoms in any patient. Comparison analysis with the prevalence of COVID-19 in those Regions [8.96% (95% CI 8.96-8.99% vs 0.00% (95% IC 0.00-3.62%)] showed statistical significance (p<0.01).

Conclusion

The results of the study contribute to suggest that increased ACE2 does not increase risk of COVID-19 and that ACEi and ARBs by blocking excessive AT1R-mediated Ang II activation, might favour the increase of ACE2-derived Ang 1-7. The GS/BS patients’ increased ACE2 and Ang 1-7 levels and their characteristic chronic metabolic alkalosis might suggest for SARS-COV-2 a mechanism similar to that of chloroquine/hydroxychloroquine effect altering ACE2 glycosylation which resulted, in previous studies, in SARS-COV binding inhibition and block/inhibition of viral entry. Studies from our laboratory are ongoing to explore in GS/BS ACE2 glycosylation.

ACE2 and SARS-CoV-2 Infection Risk: Insights From Patients With Two Rare Genetic Tubulopathies, Gitelman's and Bartter's Syndromes

COVID-19 is spreading globally with the angiotensin converting enzyme (ACE)-2 serving as the entry point of SARS-CoV-2 virus. This raised concerns how ACE2 and the Renin-Angiotensin (Ang)-System (RAS) are to be dealt with given their roles in hypertension and their involvement in COVID-19's morbidity and mortality. Specifically, increased ACE2 expression in response to treatment with ACE inhibitors (ACEi) and Ang II receptor blockers (ARBs) might theoretically increase COVID-19 risk by increasing SARS-CoV-2 binding sites. However, ACE2 is part of the protective counter-regulatory ACE2-Ang1-7-MasR axis, which opposes the classical ACE-AngII-AT1R regulatory axis. We used Gitelman's and Bartter's syndromes (GS/BS) patients, rare genetic tubulopathies that have endogenously increased levels of ACE2, to explore these issues. Specifically, 128 genetically confirmed GS/BS patients, living in Lombardia, Emilia Romagna and Veneto, the Northern Italy hot spots for COVID-19, were surveyed via telephone survey regarding COVID-19. The survey found no COVID-19 infection and absence of COVID-19 symptoms in any patient. Comparison analysis with the prevalence of COVID-19 in those regions showed statistical significance (p < 0.01). The results of the study strongly suggest that increased ACE2 does not increase risk of COVID-19 and that ACEi and ARBs by blocking excessive AT1R-mediated Ang II activation might favor the increase of ACE2-derived Ang 1-7. GS/BS patients' increased ACE2 and Ang 1-7 levels and their characteristic chronic metabolic alkalosis suggest a mechanism similar to that of chloroquine/hydroxychloroquine effect on ACE2 glycosylation alteration with resulting SARS-COV-2 binding inhibition and blockage/inhibition of viral entry. Studies from our laboratory are ongoing to explore GS/BS ACE2 glycosylation and other potential beneficial effects of BS/GS. Importantly, the absence of frank COVID-19 or of COVID-19 symptoms in the BS/GS patients cohort, given no direct ascertainment of COVID-19 status, suggest that elevated ACE2 levels as found in GS/BS patients at a minimum render COVID-19 infection asymptomatic and thus that COVID-19 symptoms are driven by ACE2 levels.

Genetics and phenotypic heterogeneity of Dent disease: the dark side of the moon

Dent disease is a rare genetic proximal tubulopathy which is under-recognized. Its phenotypic heterogeneity has led to several different classifications of the same disorder, but it is now widely accepted that the triad of symptoms low-molecular-weight proteinuria, hypercalciuria and nephrocalcinosis/nephrolithiasis are pathognomonic of Dent disease. Although mutations on the CLCN5 and OCRL genes are known to cause Dent disease, no such mutations are found in about 25–35% of cases, making diagnosis more challenging. This review outlines current knowledge regarding Dent disease from another perspective. Starting from the history of Dent disease, and reviewing the clinical details of patients with and without a genetic characterization, we discuss the phenotypic and genetic heterogeneity that typifies this disease. We focus particularly on all those confounding clinical signs and symptoms that can lead to a misdiagnosis. We also try to shed light on a concealed aspect of Dent disease. Although it is a proximal tubulopathy, its misdiagnosis may lead to patients undergoing kidney biopsy. In fact, some individuals with Dent disease have high-grade proteinuria, with or without hematuria, as in the clinical setting of glomerulopathy, or chronic kidney disease of uncertain origin. Although glomerular damage is frequently documented in Dent disease patients’ biopsies, there is currently no reliable evidence of renal biopsy being of either diagnostic or prognostic value. We review published histopathology reports of tubular and glomerular damage in these patients, and discuss current knowledge regarding the role of CLCN5 and OCRL genes in glomerular function.

Letter: ACE2, Rho kinase inhibition and the potential role of vitamin D against COVID-19

LINKED CONTENT This article is linked to Panarese et al and Kumar et al papers. To view these articles, visit https://doi.org/10.1111/apt.15752 and https://doi.org/10.1111/apt.15801.

P0084DIGENIC INHERITANCE: TWO RARE CASES OF GITELMAN SYNDROME

Background and Aims

The clinical implementation of whole-exome sequencing (WES) as molecular diagnostic tool allows investigation of the pathogenic variants interplay in multiple genes resulting in complex spectrum of phenotypes in a same patient. The phenotypic complexity of genetic disease in patients with multiple molecular diagnoses is a challenge. The blending of two distinct disease phenotypes in a same patient may suggest an apparently new clinical phenotype, while molecular diagnoses with two overlapping disease phenotypes may result in phenotypic expansion of a single disease. We present two autosomal recessive Gitelman syndrome (GS) patients whose pathogenic variants in two different genes challenged us for clinical interpretation and therapeutic intervention.

Method

Case 1: GS diagnosis at 4 years of age, severe clinical phenotype (appearance at unusual early age, hypochloremia, borderline hypomagnesemia resembling Bartter syndrome (BS), need of more complex therapy. Case 2: The diagnosis of GS was made at the age of 45 years. The patient presented classical signs of GS, with less marked metabolic alkalosis and unusual chronic renal insufficiency (CRI). Exome sequencing panel was used for mutational screening of Bartter (BS) and GS genes. Sanger sequencing and Multiplex Ligation-dependent Probe Amplification (MLPA) were also applied.

Results

Case 1: We detected in the SLC12A3 gene the frameshift p.(Thr7Arfs) and the missense p.(Gly264Ala) variants, the first a known disease-causing mutation, the second associated with a severe form of GS in a patient. Another known disease-causing mutation p.(Met357Thr) was detected in the KCNJ1 gene encoding renal outer medullary K+ channel, ROMK1. It is one BS gene and was never associated with GS. The SLC12A3 p.(Gly264Ala) variant’s high frequency makes it uncommon polymorphism although functional because it alters NCC activity but makes questionable its causative effect on GS phenotype. Our patient severe GS phenotype may be determined by the mutations in either SLC12A3 and KCNJ1 genes inherited respectively from mother and father. If the hypomorphic SLC12A3 variant is causative, hence the heterozygous KCNJ1 pathogenic variant might be a modifier allele responsible of the GS severe presentation. Case 2: We detected two novel variants in the SLC12A3 gene [p.(Lys894fs):p.(Pro331Leu)]. Both are pathogenic according to ACMG guidelines. Another very rare missense variant p.(Val245Met) was identified in the SLC4A1 gene, whose mutations cause distal tubular acidosis type I (dRTA). The missense mutation, never associated with dRTA, is predicted pathogenic by in silico tools. Its presence questions on phenotype interpretation: blended phenotype due to a concomitant presence of a dual molecular diagnosis? Or an expansion of a single phenotype (GS) due to the presence of a modifier gene variant? dRTA and GS have overlapping features such as hypokalemia, hypercalciuria. In the patient the less marked metabolic alkalosis, and the presence of CRF points to the latter.

Conclusion

Digenic inheritance in GS was reported in only one other instance. These two cases demonstrate how our understanding of the complexity of genetic heterogeneity of rare diseases is far to be completed. It becomes essential to shed light on how combinations of variants in different genes are responsible for a disease phenotype

From protein uptake to Dent disease: An overview of the CLCN5 gene

Proteinuria is a well-known risk factor, not only for renal disorders, but also for several other problems such as cardiovascular diseases and overall mortality. In the kidney, the chloride channel Cl^-/H⁺ exchanger ClC-5 encoded by the CLCN5 gene is actively involved in preventing protein loss. This action becomes evident in patients suffering from the rare proximal tubulopathy Dent disease because they carry a defective ClC-5 due to CLCN5 mutations. In fact, proteinuria is the distinctive clinical sign of Dent disease, and mainly involves the loss of low-molecular-weight proteins. The identification of CLCN5 disease-causing mutations has greatly improved our understanding of ClC-5 function and of the ClC-5-related physiological processes in the kidney. This review outlines current knowledge regarding the CLCN5 gene and its protein product, providing an update on ClC-5 function in tubular and glomerular cells, and focusing on its relationship with proteinuria and Dent disease.

CLCN5 5'UTR isoforms in human kidneys: differential expression analysis between controls and patients with glomerulonephritis

ClC-5, the electrogenic chloride/proton exchanger strongly expressed in renal proximal tubules, belongs to the endocytic macromolecular complex responsible for albumin and low-molecular-weight protein uptake. ClC-5 was found to be overexpressed in glomeruli of glomerulonephritis and in cultured human podocytes under albumin overload. The transcriptional regulation of human ClC-5 is not fully understood. Three functional promoters of various strengths and 11 different 5' untranslated region (5'UTR) isoforms of CLCN5 messenger RNA (mRNA) were detected in the human kidney (variants 1-11). The aim of this study was to investigate the expression pattern of CLCN5 5'UTR variants and the CLCN5 common translated region in glomerulonephritis. The 5'UTR ends and the translated region of CLCN5 mRNA were analyzed using quantitative relative real-time PCR or quantitative comparative endpoint PCR with GAPDH as housekeeping gene in 8 normal kidneys and 12 renal biopsies from patients with glomerulonephritis. The expression profile for all variants in normal and glomerulonephritis biopsies was similar, and variant 3 and alternative variant 4 were the most abundantly expressed in both sets. In glomerulonephritis biopsies, isoforms under the control of a weak promoter (variants 4, 6 and 7) showed an increased expression leading to an increase in the CLCN5 translated region, underscoring their importance in kidney pathophysiology. Since weak promoters can be turned on by different stimuli, these data support the hypothesis that proteinuria could be one of the stimuli capable of starting a signaling pathway that induces an increase in CLCN5 transcription.

Genetic Analyses in Dent Disease and Characterization of CLCN5 Mutations in Kidney Biopsies

Dent disease (DD), an X-linked renal tubulopathy, is mainly caused by loss-of-function mutations in CLCN5 (DD1) and OCRL genes. CLCN5 encodes the ClC-5 antiporter that in proximal tubules (PT) participates in the receptor-mediated endocytosis of low molecular weight proteins. Few studies have analyzed the PT expression of ClC-5 and of megalin and cubilin receptors in DD1 kidney biopsies. About 25% of DD cases lack mutations in either CLCN5 or OCRL genes (DD3), and no other disease genes have been discovered so far. Sanger sequencing was used for CLCN5 gene analysis in 158 unrelated males clinically suspected of having DD. The tubular expression of ClC-5, megalin, and cubilin was assessed by immunolabeling in 10 DD1 kidney biopsies. Whole exome sequencing (WES) was performed in eight DD3 patients. Twenty-three novel CLCN5 mutations were identified. ClC-5, megalin, and cubilin were significantly lower in DD1 than in control biopsies. The tubular expression of ClC-5 when detected was irrespective of the type of mutation. In four DD3 patients, WES revealed 12 potentially pathogenic variants in three novel genes (SLC17A1, SLC9A3, and PDZK1), and in three genes known to be associated with monogenic forms of renal proximal tubulopathies (SLC3A, LRP2, and CUBN). The supposed third Dent disease-causing gene was not discovered.

Dent disease: A window into calcium and phosphate transport

This review examines calcium and phosphate transport in the kidney through the lens of the rare X-linked genetic disorder Dent disease. Dent disease type 1 (DD1) is caused by mutations in the CLCN5 gene encoding ClC-5, a Cl^- /H⁺ antiporter localized to early endosomes of the proximal tubule (PT). Phenotypic features commonly include low molecular weight proteinuria (LMWP), hypercalciuria, focal global sclerosis and chronic kidney disease; calcium nephrolithiasis, nephrocalcinosis and hypophosphatemic rickets are less commonly observed. Although it is not surprising that abnormal endosomal function and recycling in the PT could result in LMWP, it is less clear how ClC-5 dysfunction disturbs calcium and phosphate metabolism. It is known that the majority of calcium and phosphate transport occurs in PT cells, and PT endocytosis is essential for calcium and phosphorus reabsorption in this nephron segment. Evidence from ClC-5 KO models suggests that ClC-5 mediates parathormone endocytosis from tubular fluid. In addition, ClC-5 dysfunction alters expression of the sodium/proton exchanger NHE3 on the PT apical surface thus altering transcellular sodium movement and hence paracellular calcium reabsorption. A potential role for NHE3 dysfunction in the DD1 phenotype has never been investigated, either in DD models or in patients with DD1, even though patients with DD1 exhibit renal sodium and potassium wasting, especially when exposed to even a low dose of thiazide diuretic. Thus, insights from the rare disease DD1 may inform possible underlying mechanisms for the phenotype of hypercalciuria and idiopathic calcium stones.

Human proximal tubular cells can form calcium phosphate deposits in osteogenic culture: role of cell death and osteoblast-like transdifferentiation

Nephrocalcinosis is a clinicopathological entity characterized by microscopic calcium crystals in the renal parenchyma, within the tubular lumen or in the interstitium. Crystal binding to tubular cells may be the cause underlying nephrocalcinosis and nephrolithiasis. Pathological circumstances, such as acute cortical necrosis, may induce healthy cells to acquire a crystal-binding phenotype. The present study aimed to investigate whether human renal proximal tubular cells (HK-2 cells) can form calcium phosphate deposits under osteogenic conditions, and whether apoptosis and/or osteogenic-like processes are involved in cell calcification. HK-2 cells were cultured in standard or osteogenic medium for 1, 5, and 15 days. Von Kossa staining and ESEM were used to analyze crystal deposition. Apoptosis was investigated, analyzing caspase activation by in-cell Western assay, membrane translocation of phosphotidylserine by annexin V-FITC/propidium iodide staining, and DNA fragmentation by TUNEL assay. qRT/PCR, immunolabeling and cytochemistry were performed to assess osteogenic activation (Runx2, Osteonectin, Osteopontin and ALP), and early genes of apoptosis (BAX, Bcl-2). HK-2 cell mineralization was successfully induced on adding osteogenic medium. Calcium phosphate deposition increased in a time-dependent manner, and calcified cell aggregates exhibited characteristic signs of apoptosis. At 15 days, calcifying HK-2 cells revealed osteogenic markers, such as Runx2, ALP, osteonectin and osteopontin. Monitoring the processes at 1, 5, and 15 days showed apoptosis starting already after 5 days of osteogenic induction, when the first small calcium phosphate crystals began to appear on areas where cell aggregates were in apoptotic conditions. The cell death process proved caspase-dependent. The importance of apoptosis was reinforced by the time-dependent increase in BAX expression, starting from day 1. These findings strongly support the hypothesis that apoptosis triggered HK-2 calcification even before any calcium phosphate crystal deposition or acquisition of an osteogenic phenotype.

Circulating miRNA-375 as a potential novel biomarker for active Kaposi's sarcoma in AIDS patients

The aim of this study was to identify circulating microRNAs (miRNAs) that could be used as biomarkers in patients at risk for or affected by AIDS‐Kaposi's sarcoma (KS). Screening of 377 miRNAs was performed using low‐density arrays in pooled plasma samples of 10 HIV/human herpesvirus 8 (HHV8)‐infected asymptomatic and 10 AIDS‐KS patients before and after successful combined antiretroviral therapy (cART). MiR‐375 was identified as a potential marker of active KS, being the most down‐regulated in AIDS‐KS patients after cART and the most up‐regulated in naïve AIDS‐KS patients compared to naïve asymptomatic subjects. Validation on individual plasma samples confirmed that miR‐375 levels were higher in AIDS‐KS compared to asymptomatic patients, decreased after cART‐induced remission in most AIDS‐KS patients and increased in patients with active KS. In asymptomatic patients miR‐375 was up‐regulated after cART in both screening and validation. Statistical analyses revealed an association between miR‐375 changes and CD4 cell counts, which could explain the discordant cases and the opposite trend between asymptomatic and AIDS‐KS patients. These data suggest that circulating miR‐375 might be a good indicator of active AIDS‐KS. Moreover, changes in miR‐375 levels may have a prognostic value in HIV/HHV8‐infected patients undergoing treatment. Further large‐scale validation is needed.

Caspase-independent programmed cell death triggers Ca2PO4 deposition in an in vitro model of nephrocalcinosis

Nephrocalcinosis involves the deposition of microscopic crystals in the tubular lumen or interstitium. While the clinical, biochemical, and genetic aspects of the diseases causing nephrocalcinosis have been elucidated, little is known about the cellular events in this calcification process. We previously reported a phenomenon involving the spontaneous formation of Ca2PO4 nodules in primary papillary renal cells from a patient with medullary nephrocalcinosis harboring a rare glial cell-derived neurotrophic factor (GDNF) gene variant. We also demonstrated that cultivating GDNF-silenced human kidney-2 (HK-2) cells in osteogenic conditions for 15 days triggered Ca2PO4 deposits. Given the reportedly close relationship between cell death and pathological calcification, aim of the present study was to investigate whether apoptosis is involved in the calcification of GDNF-silenced HK-2 cells under osteogenic conditions. Silenced and control cells were cultured in standard and osteogenic medium for 1, 5, and 15 days, and any Ca2PO4 deposition was identified by means of von Kossa staining and environmental SEM (ESEM) analyses. Based on the results of annexin V and propidium iodide (PI) analysis, and terminal deoxynucleotidyl transferase dUTP-biotin nick end labeling (TUNEL) assay, the silenced cells in the osteogenic medium showed a significant increase in the percentage of cells in the late phase of apoptosis and an increased Ca2PO4 deposition at 15 days. The results of quantitative real-time PCR (qRT-PCR) of BAX and BCL2, and in-cell Western analysis of caspases indicated that the cell death process was independent of caspase-3, -6, -7, and -9 activation, however. Using this model, we provide evidence of caspase-independent cell death triggering the calcification process in GDNF-silenced HK-2 cells.

Albumin uptake in human podocytes: a possible role for the cubilin-amnionless (CUBAM) complex

Albumin re-uptake is a receptor-mediated pathway located in renal proximal tubuli. There is increasing evidence of glomerular protein handling by podocytes, but little is known about the mechanism behind this process. In this study, we found that human podocytes in vitro are committed to internalizing albumin through a receptor-mediated mechanism even after exposure to low doses of albumin. We show that these cells express cubilin, megalin, ClC-5, amnionless and Dab2, which are partners in the tubular machinery. Exposing human podocytes to albumin overload prompted an increase in CUBILIN, AMNIONLESS and CLCN5 gene expression. Inhibiting cubilin led to a reduction in albumin uptake, highlighting its importance in this mechanism. We demonstrated that human podocytes are committed to performing endocytosis via a receptor-mediated mechanism even in the presence of low doses of albumin. We also disclosed that protein overload first acts on the expression of the cubilin-amnionless (CUBAM) complex in these cells, then involves the ClC-5 channel, providing the first evidence for a possible role of the CUBAM complex in albumin endocytosis in human podocytes.

Crosstalk between the mesothelium and lymphomatous cells: insight into the mechanisms involved in the progression of body cavity lymphomas

The peculiar localization of body cavity lymphomas implies a specific contribution of the intracavitary microenvironment to the pathogenesis of these tumors. In this study, primary effusion lymphoma (PEL) was used as a model of body cavity lymphoma to investigate the role of mesothelial cells, which line the serous cavities, in lymphoma progression. The crosstalk between mesothelial and lymphomatous cells was studied in cocultures of primary human mesothelial cells (HMC) with PEL cells and a xenograft mouse model of peritoneal PEL. PEL cells were found to induce type 2 epithelial–mesenchymal transition (EMT) in HMC, which converted into a myofibroblastic phenotype characterized by loss of epithelial markers (pan cytokeratin and E-cadherin), expression of EMT-associated transcriptional repressors (Snail1, Slug, Zeb1, Sip1), and acquisition of α-smooth muscle actin (α-SMA), a mesenchymal protein. A progressive thickening of serosal membranes was observed in vivo, accompanied by loss of cytokeratin staining and appearance of α-SMA-expressing cells, confirming that fibrosis occurred during intracavitary PEL development. On the other hand, HMC were found to modulate PEL cell turnover in vitro, increasing their resistance to apoptosis and proliferation. This supportive activity on PEL cells was retained after transdifferentiation, and was impaired by interferon-α₂b treatment. On the whole, our results indicate that PEL cells induce type 2 EMT in HMC, which support PEL cell growth and survival, providing a milieu favorable to lymphoma progression. Our findings provide new clues into the mechanisms involved in lymphoma progression and may indicate new targets for effective treatment of malignant effusions growing in body cavities.

Reversal of profound and "deep" residual rocuronium-induced neuromuscular blockade by sugammadex: a neurophysiological study

BACKGROUND

Sugammadex is the first of a new class of selective relaxant binding drugs developed for the rapid and complete reversal of neuromuscular blockade (NMB) induced by the aminosteroid neuromuscular blocking drugs rocuronium and vecuronium. Neuromuscular blocking drugs block the transmission from the peripheral nerve to the muscle units, with reduction and disappearance of the evoked electromyographic activity. Usually, neuromuscular monitoring for the investigational reversal drug is performed by calibrated acceleromyography. The efficacy of sugammadex in reversing profound and "deep" residual rocuronium-induced NMB using myogenic motor evoked potentials (mMEPs) monitoring was evaluated.

METHODS

In this prospective trial, 30 consenting patients undergoing propofol-remifentanil anesthesia for spine surgery were enrolled and divided into two groups: Group 1, reversal of profound NMB (sugammadex 16 mg/Kg, 3 minutes after rocuronium 1.2 mg/Kg) and Group 2, reversal of "deep" residual NMB (sugammadex 4 mg/Kg, 15 minutes after rocuronium 0.6 mg/Kg). Myogenic MEPs registrations of upper and lower limbs and the diaphragm were performed, as well as TOF monitoring.

RESULTS

After injection of 4 mg/Kg of sugammadex, the means of recovery time of the basal mMEPs amplitudes (diaphragm, and lower limbs and upper limbs) were 124±9.6, 143±163, 151±207 sec, respectively whereas after 16 mg/Kg of sugammadex the times were 109±13.8, 124±0.6, and 135±14.1 sec. Times to TOF ratio 0.9 were 114±75 and 186±105 sec in Group 1 and 2, respectively. No serious adverse effects related to sugammadex and to electrical stimulation were reported. No reoccurrence of neuromuscular block was observed.

CONCLUSION

Neurophysiological monitoring using mMEPs confirmed that sugammadex provided a complete recovery from profound and "deep" residual rocuronium-induced neuromuscular blockade.

Ultrasound identification of nerve cords in the infraclavicular fossa: a clinical study

BACKGROUND

This study aimed to analyze nerve trunk anatomy in the infraclavicular fossa and to correlate these data with the most common anthropometric parameters.

METHODS

A Mylab 30 Gold (Esaote) and the linear transducer LA523 (7.5 MHz frequency) were used. The probe was oriented according to a parasagittal plane, parallel to the lateral chest wall and immediately medial to the coracoid process underneath the clavicle. Measurements included the distance between the artery and the cutaneous surface (mm) and the apical corner of the ultrasound image (mm), the number of identified nervous cords and their position related to the axillary artery, and the position and number of axillary veins. Sex, age, height, weight, body mass index (BMI), biceps girth, and breast size were recorded. Statistical analysis included calculation of linear Pearson correlation coefficient and Student's t test.

RESULTS

Two hundred and two consecutive patients were enrolled. The position of the three cords was highly variable around the artery. In a small but significant percentage of patients (8.9%), the medial and the lateral cords were located together at the top of the artery. The visibility of the trunks and the distance between the upper part of the artery and the apical corner of the ultrasound image correlated with anthropometric characteristics. The vein position with respect to the artery and nerves was markedly variable.

CONCLUSION

Sono-anatomic study of the infraclavicular region adds important data that is useful when conducting nerve blocks to improve safety and likelihood of success.

Profiling insulin like factor 3 (INSL3) signaling in human osteoblasts

BACKGROUND

Young men with mutations in the gene for the INSL3 receptor (Relaxin family peptide 2, RXFP2) are at risk of reduced bone mass and osteoporosis. Consistent with the human phenotype, bone analyses of Rxfp2(-/-) mice showed decreased bone volume, alterations of the trabecular bone, reduced mineralizing surface, bone formation, and osteoclast surface. The aim of this study was to elucidate the INSL3/RXFP2 signaling pathways and targets in human osteoblasts.

METHODOLOGY/PRINCIPAL FINDINGS

Alkaline phosphatase (ALP) production, protein phosphorylation, intracellular calcium, gene expression, and mineralization studies have been performed. INSL3 induced a significant increase in ALP production, and Western blot and ELISA analyses of multiple intracellular signaling pathway molecules and their phosphorylation status revealed that the MAPK was the major pathway influenced by INSL3, whereas it does not modify intracellular calcium concentration. Quantitative Real Time PCR and Western blotting showed that INSL3 regulates the expression of different osteoblast markers. Alizarin red-S staining confirmed that INSL3-stimulated osteoblasts are fully differentiated and able to mineralize the extracellular matrix.

CONCLUSIONS/SIGNIFICANCE

Together with previous findings, this study demonstrates that the INSL3/RXFP2 system is involved in bone metabolism by acting on the MAPK cascade and stimulating transcription of important genes of osteoblast maturation/differentiation and osteoclastogenesis.

Effects of type 5-phosphodiesterase inhibition on energy metabolism and mitochondrial biogenesis in human adipose tissue ex vivo

OBJECTIVE

An excess of adipose tissue (AT) in obese individuals is linked to increased cardiovascular risk and mitochondria have been shown to be defective in the muscle and AT of patients with metabolic disorders such as obesity and Type 2 diabetes. Nitric oxide (NO) generated by endothelial NO synthase (eNOS) plays a role in mitochondrial biogenesis through cyclic-GMP (cGMP). AT harbors the whole molecular signaling pathway of NO, together with type 5-phosphodiesterase (PDE- 5), the main cGMP catabolising enzyme.

AIM

Our aim was to evaluate the effect of the modulation of NO pathway, through PDE-5 inhibition, on energy metabolism and mitochondria biogenesis in human omental AT.

METHODS AND MEASUREMENTS

Cultured human omental AT was stimulated with PDE-5 inhibitor, vardenafil, at different concentration for 24 and 72 h. Analysis of the expression of both key-regulator genes of adipocyte metabolism and mitochondria-biogenesis markers was performed.

RESULTS

We found an increased gene expression of peroxisome proliferator-activated receptor-γ (PPAR-γ), adiponectin, and proliferator- activated receptor gamma coactivator-1 α (PGC-1α) after a 24-h stimulation with vardenafil at the lowest concentration employed compared to controls (p<0.05). After 72 h of stimulation, a significant increase of mitochondrial DNA was found compared to control samples (p<0.05).

CONCLUSION

Our data suggest that PDE-5 inhibition could have an impact on mitochondrial content of human AT suggesting a positive effect on energy metabolism and adding new elements in the comprehension of AT pathophysiology.

Effect of relaxin on human sperm functions

Relaxin is a circulating hormone with functions in pregnancy, parturition, and other aspects of female reproduction. It is also secreted from the prostate gland into the seminal fluid; however, the role of relaxin in male reproduction is debated. Studies conducted in the past have suggested possible actions on human spermatozoa, but the data were contrasting. Here, we show that the relaxin receptor RXFP1 (Relaxin Family Peptide Receptor 1) is expressed in human spermatozoa, and it mainly localizes in the astrodome. In vitro studies on human sperm demonstrated that this hormone attenuates the natural decline in sperm motility and maintains higher mitochondrial activity and lower apoptosis level. Furthermore, relaxin induced an increase in sperm hyperactivation, intracellular calcium and cAMP, and acrosome reaction. These effects were abolished by the use of the specific anti-RXFP1 antibody. Relaxin concentrations were low in the blood (x ± SD, 0.16 ± 0.03 nM) and very high in the seminal plasma (x ± SD, 10.3 ± 4.0 nM), confirming its secretion mainly by the prostate. Taken together, these data demonstrate that relaxin influences positively many sperm functions linked to fertilizing ability, and it preserves sperm functionality, with possible practical value in assisted reproduction techniques.

Androgens modulate osteocalcin release by human visceral adipose tissue

OBJECTIVE

Androgens inhibit adipogenic differentiation through an androgen receptor (AR)-mediated pathway, increase lipolysis and reduce lipid accumulation in adipocytes. Undercarboxylated osteocalcin (ucOCN) regulates insulin and adiponectin secretion and is released by adipose tissue (AT). Our objective was to investigate, ex vivo and in vivo, the role of androgens on osteocalcin (OCN) modulation in human AT. DesiGN, PATIENTS, SETTING: Omental AT (OAT) for in vitro study and blood samples from 91 male patients of Padova University Hospital were used.

MEASUREMENTS

Omental AT was treated with dihydrotestosterone (DHT) in presence and in absence of flutamide. cOCN and ucOCN release by AT in a simple growth medium was evaluated by ELISA. OCN, both undercarboxylated (ucOCN) and carboxylated (cOCN) forms, was measured in serum by ELISA.

RESULTS

After 24-h DHT stimulation, the release of both cOCN and ucOCN by OAT was statistically increased (P < 0·05). Co-incubation with flutamide blunted OCN production. Overweight and obese patients had lower total and free testosterone (T), associated with lower ucOCN and ucOCN/OCN ratio. Free T was negatively correlated to BMI (ρ = -0·706, P < 0·05) and positively correlated to ucOCN/OCN ratio (ρ = 0·223, P < 0·05).

CONCLUSIONS

Our data suggest that androgens modulate OCN release by OAT in vitro. In addition to the anti-adipogenic role of androgens, they support a novel mechanism by which androgens could exert a protective effect in energy metabolism. This hypothesis appears even more significant considering that sexual hormones' levels are greatly altered in obesity and that AT is both highly involved in their clearance and able to produce OCN.

Evidence for osteocalcin production by adipose tissue and its role in human metabolism

CONTEXT

The adipose tissue (AT), which is an endocrine organ, is linked to several metabolic abnormalities. Undercarboxylated osteocalcin (ucOCN) regulates insulin and adiponectin secretion.

OBJECTIVE

Our objective was to investigate the involvement of OCN in obesity and to evaluate, in vitro and ex vivo, the role of AT in the modulation of this endocrine circuit.

DESIGN, PATIENTS, AND SETTING

This transversal study involved 83 male subjects, divided according to the World Health Organization body mass index classification, evaluated at Padova's Obesity Outpatient Clinic.

METHODS

OCN, both undercarboxylated (ucOCN) and carboxylated (cOCN) forms, was measured in serum by ELISA. OCN mRNA expression and protein production were measured by quantitative RT-PCR and immunohistochemistry during in vitro adipogenesis and in sc AT (SAT) and omental AT (OAT) from normal adult men. cOCN and ucOCN release by AT in a simple growth medium was verified by ELISA.

RESULTS

Overweight and obese patients had a lower ucOCN and ucOC/OCN ratio. In the whole cohort, ucOCN/OCN ratio was negatively correlated to body mass index (rho = -0.233; P < 0.05). OCN mRNA was present in SAT and OAT and during all stages of adipogenesis, with higher expression in the first steps. Immunohistochemistry confirmed the expression of OCN protein. Both SAT and OAT were able to release cOCN and ucOCN.

CONCLUSIONS

Our data support a pathophysiological link between ucOCN and cOCN balance and obesity. OCN is present in the first phases of adipogenesis but also in human AT ex vivo. AT releases, in vitro, both ucOCN and cOCN, suggesting a possible link between AT and OCN in the regulation of metabolism.

Relaxin stimulates osteoclast differentiation and activation

Relaxin is a pleiotropic hormone with actions in reproductive and non-reproductive tissues, and has a role in tumor biology. It can promote growth, differentiation and invasiveness of different tumors, especially those that give bone metastases, and relaxin serum concentrations are increased in patients with bone metastasis. In osteolytic metastasis the destruction of bone is mediated by osteoclasts that are multinucleated cells derived from hematopoietic progenitors. We found that human hematopoietic precursors and mature osteoclasts express the relaxin receptor RXFP1. Then, we investigated the effects of relaxin on the differentiation, activation and gene expression of osteoclasts during in vitro osteoclastogenesis from human hematopoietic progenitor cells. Relaxin alone was able to induce the multistep differentiation process of human osteoclastogenesis with timing similar to that obtained with the classical stimulators of osteoclastogenesis RANKL, M-CSF and PTH. The expression profile of several osteoclast genes was studied with quantitative RT-PCR during the entire process of osteoclastogenesis. This analysis showed that relaxin induced genes that are implicated in the differentiation, survival and activation of osteoclasts. Relaxin-induced osteoclasts were fully differentiated, positive for tartrate resistant acid phosphatase and vitronectin receptor, expressing a typical F-actin ring and able to resorb the bone. Furthermore, relaxin induced the expression of its specific receptor RXFP1 in osteoclasts. This study demonstrates for the first time that relaxin is a potent stimulator of osteoclastogenesis from hematopoietic precursors and regulates the activity of mature osteoclasts, opening new perspectives on the role of this hormone in bone physiology, diseases and metastasis.

Mitral valve endocarditis in a severe burn patient

The authors describe the case of a 40-year-old female with severe burns (85% of total body surface area including the thorax) caused by thermal injury who presented mitral valve endocarditis during intensive care unit stay. Bacterial endocarditis represents a rare cause of fatal septicemia complicating thermal injury. The authors focus on diagnosis and on timing of surgical treatment.

New roles for INSL3 in adults

Insulin-like factor 3 (INSL3) is produced primarily by testicular Leydig cells and acts by binding to its specific G-protein-coupled receptor, RXFP2 (relaxin family peptide 2). INSL3 is involved in testicular descent during fetal development, and mutations in the INSL3 and RXFP2 genes cause cryptorchidism. The physiological role of INSL3 in adults is not known, although substantial INSL3 circulating levels are present. After extensive clinical, biochemical, and hormonal investigations, including bone densitometry with dual energy X-ray absorptiometry, on 25 young men (age, 27-41 years) who have the well-characterized T222P mutation in the RXFP2 gene, we found that 16 of them (64%) had significantly reduced bone density. No other cause of osteoporosis was evident in these subjects, whose testosterone and gonadal function were normal. Expression analysis of INSL3 and RXFP2 on human bone biopsy and human and mouse osteoblast cell cultures performed by reverse transcription-PCR and immunohistochemistry showed the presence of RXFP2 in these cells. Real-time cAMP imaging analysis and proliferation assays under the stimulus of INSL3 showed a dose- and time-dependent increase in cAMP and cell proliferation, and specific osteoblast gene activation was observed by real-time PCR after INSL3 stimulation. Lumbar spine and femoral bone of Rxfp2-deficient mice were studied by static and dynamic histomorphometry and micro-computed tomography, respectively, and showed decreased bone mass, mineralizing surface, bone formation, and osteoclast surface compared to wild-type littermates, compatible with a functional osteoblast impairment. This study identified for the first time a role for INSL3 in adults, demonstrating a modulating effect on bone metabolism and linking RXFP2 gene mutations with human osteoporosis.

T222P mutation of the insulin-like 3 hormone receptor LGR8 is associated with testicular maldescent and hinders receptor expression on the cell surface membrane

Insulin-like 3 (INSL3) hormone plays a crucial role in testicular descent during embryonic development. Genetic ablation of Insl3 or its G protein-coupled receptor (GPCR) Lgr8 causes cryptorchidism in mice. Previously, we identified a nonfunctional T222P mutation of LGR8 in several human patients with testicular maldescent. Using a large population of patients and healthy controls from Italy, we have demonstrated that T222P LGR8 mutation is present only in affected patients (19 T222P/+ of 598 vs. 0/450, P < 0.0001). We have also identified a novel allele of LGR8 (R223K) found in one patient with retractile testes. Both mutations are located in the leucine-rich repeats (LRRs) of GPCR ectodomain. The expression analysis of T222P mutant receptor transfected into 293T cells revealed that the mutation severely compromised GPCR cell membrane expression. The substitution of Thr(222) with the neutral Ser or Ala, or the R223K mutation, did not alter receptor cell membrane expression or ligand-induced cAMP increase. Additional mutations, affecting first leucine in a signature LxxLxLxxN/CxL stretch of LRR (L283F), or the amino acid residues, forming the disulfide bond or coordinating calcium ion in the LDLa module (C71Y and D70Y), also rendered proteins with reduced cell surface expression. The structural alterations of both LRRs and LDLa of the ligand-binding part of LGR8 cause the inability of receptor to express on the cell surface membrane and might be responsible for the abnormal testicular phenotype in patients.

Insulin-like factor 3 gene mutations in testicular dysgenesis syndrome: clinical and functional characterization

Insulin-like factor 3 (INSL3) plays a crucial role in testicular descent. Genetic ablation of Insl3 or its G protein-coupled receptor, leucine-rich repeat-containing G-protein-coupled receptor (Lgr8), causes cryptorchidism in mice. Mutation analyses of INSL3 in humans showed an association with cryptorchidism but led to non-conclusive data about a causative role. In this study, we explored the hypothesis that mutations in INSL3 may be associated with the signs of testicular dysgenesis syndrome (TDS). We screened for mutations in INSL3 gene in 967 subjects with a history of maldescended testes and/or infertility and/or testicular cancer and in 450 controls. Furthermore, we carried out in vitro functional analysis of three novel mutations by analysis of INSL3-dependent cAMP increase in cells expressing LGR8. We found six INSL3 mutations in 18 of 967 patients (1.9%) and no mutations in controls. Prevalence of mutations was similar in the different groups of patients (cryptorchidism and/or infertility and/testicular cancer). Three mutations were novel findings (R4H, W69R, and R72K); however, their analysis showed normal cAMP increase after the activation of LGR8 receptor. In conclusion, we found a significant association of INSL3 gene mutations in men presenting one or more signs of TDS syndrome. However, a causative role for some of these mutations is not clearly supported by functional analyses. Although a role for mutations of INSL3 and LGR8 genes in cryptorchidism is reasonable, additional studies are needed to establish an association between the disruption of INSL3 pathway and higher risk of infertility or testicular cancer.