Loss of endothelial barrier integrity in mice with conditional ablation of podocalyxin (Podxl) in endothelial cells

Immune-endothelial cell crosstalk in hepatic endothelial injury of liver fibrotic mice

INTRODUCTION

Liver fibrosis is a common pathological process in chronic liver disease, reflecting the advanced stage of the disease. Liver endothelial cells (ECs), especially liver sinusoidal endothelial cells (LSECs), are recognized as critical modulators of liver homeostasis and play essential roles in the recruitment and function of liver immune cells. In this study, we aimed to explore the mechanism of hepatic EC injury and the potential regulatory pathways of intercellular communication in liver fibrosis.

METHODS

In this study, C57BL/6 male mice were treated with CCl4 for 6 weeks to establish a liver fibrosis model. Masson staining and immunohistochemistry were performed to assess the extent of liver fibrosis. Hepatic endothelial injury was detected by using scanning electron microscopy (SEM) and PCR technology. Single-cell RNA sequencing (scRNA-seq) was performed to analyze phenotypic changes in nonparenchymal cells and dissect intercellular crosstalk.

RESULTS

A total of 24,534 cells were clustered into 10 main cell subsets. The LSEC fenestrae and surface receptor expression were reduced, and the expression of Cd34 was upregulated. Liver ECs exhibited dense cellular crosstalk with immune cells (macrophages, T and B cells). The analysis of intercellular signaling pathways revealed that immune cells targeted liver ECs through the Ptprc-Mrc1 and Sell-Podxl signaling pathways to maintain cellular interactions during liver fibrosis.

CONCLUSION

We revealed apparent damage and capillarization of liver ECs and demonstrated the cell-cell communications among liver immune cells and ECs during the development of liver fibrosis. The Ptprc-Mrc1 and Sell-Podxl signaling pathways exerted prominent roles in liver immune cell-EC interactions.

Plasma Proteomic Signature as a Predictor of Age Advancement in People Living With HIV

Due to the increased burden of non-AIDS-related comorbidities in people living with HIV (PLHIV), identifying biomarkers and mechanisms underlying premature aging and the risk of developing age-related comorbidities is a priority. Evidence suggests that the plasma proteome is an accurate source for measuring biological age and predicting age-related clinical outcomes. To investigate whether PLHIV on antiretroviral therapy (ART) exhibit a premature aging phenotype, we profiled the plasma proteome of two independent cohorts of virally suppressed PLHIV (200HIV and 2000HIV) and one cohort of people without HIV (200FG) using O-link technology. Next, we built a biological age-prediction model and correlated age advancement (the deviation of the predicted age from the chronological age) with HIV-related factors, comorbidities, and cytokines secreted by immune cells. We identified a common signature of 77 proteins associated with chronological age across all cohorts, most of which were involved in inflammatory and senescence-related processes. PLHIV showed increased age advancement compared to people without HIV. In addition, age advancement in the 2000HIV cohort was positively associated with prior hepatitis C and cytomegalovirus (CMV) infections, non-AIDS-related comorbidities, ART duration, cumulative exposure to the protease inhibitor Ritonavir, as well as higher production of monocyte-derived proinflammatory cytokines and chemokines and lower secretion of T-cell derived cytokines. Our proteome-based predictive model is a promising approach for calculating the age advancement in PLHIV. This will potentially allow for further characterization of the pathophysiological mechanisms linked to accelerated aging and enable monitoring the effectiveness of novel therapies aimed at reducing age-related diseases in PLHIV.

Novel Truncating Variants in PODXL Represent a New Entity to Be Explored Among Podocytopathies

BACKGROUND/OBJECTIVES

Podocalyxin is a sialoprotein mainly expressed in the kidney cortex and lung tissue, which has been described as a component of the podocyte glycocalyx. This protein promotes the reorganization of the podocyte cytoskeleton, as well as the morphogenesis and differentiation of nascent podocytes, actively participating in glomerular filtration. Previous research has suggested that PODXL haploinsufficiency leads to podocytopathy with development of focal segmental glomerulosclerosis, a disorder that has been demonstrated in Podxl-deficient animal models and proposed as a primary cause in human families affected by this condition. However, only a few families have been reported, which limits the understanding about the spectrum of phenotype and prognosis of the disease.

METHODS

We performed high-throughput sequencing in a cohort of young adults with CKD, describing the clinical scenario of those who harbored truncating variants in the PODXL gene and testing the families for detected variants.

RESULTS

The PODXL gene exhibited a slight deviation in loss intolerance probability and moderate deviation in the observed/expected ratio of variation, which is typically observed in dominant genes with age-dependent incomplete penetrance or variable expression. We reported four novel truncating variants in the PODXL gene, along with a collection of previously published monoallelic truncating variants.

CONCLUSIONS

These findings further support evidence about genetic defects in the PODXL gene associated with a new molecular entity of podocytopathy with adult onset. Additionally, the nucleotide sequence of PODXL contains particularities that require careful analysis to interpret the effect of the variants detected in this gene.

Serum podocalyxin levels in patients with obesity and carbohydrates disorders

Background: Podocalyxin is expressed not only in glomerular podocytes but also on the endothelial cell surface outside the kidney. The aim of this cross-sectional study is to evaluate the role of serum podocalyxin as an early marker for vascular injury in patients with obesity and carbohydrate disturbances.

Subjects and methods: The study group consisted of 163 patients with a mean age of 52.5 ± 11.3 years.

Results: Levels of podocalyxin were significantly higher in healthy controls compared to patients with obesity, prediabetes, and newly diagnosed diabetes. Correlation analysis revealed that podocalyxin correlates negatively with BMI, waist circumference, waist-to-hip ratio, waist to stature ratio, fasting insulin, and one hour after the oral glucose tolerance test. ROC analyses determined that circulating podocalyxin levels are valuable for differentiating subjects with prediabetes and obesity.

Conclusion: This study is the first to assess the role of podocalyxin in the entire spectrum of metabolic disorders.

Establishment and characterization of a kidney cell line from hybrid snakehead (male Channa argus × female Channa maculata) and its susceptibility to hybrid snakehead rhabdovirus (HSHRV)

Hybrid snakehead (male Channa argus × female Channa maculata) is an emerging fish breed with increasing production levels. However, infection with hybrid snakehead rhabdovirus (HSHRV) critically affects hybrid snakehead farming. In this study, a fish cell line called CAMK, derived from the kidneys of hybrid snakehead, was established and characterized. CAMK cells exhibited the maximum growth rate at 28 °C in Leibovitz's-15 medium supplemented with 10% fetal bovine serum(FBS). Karyotyping revealed diploid chromosomes in 54% of the cells at the 50th passage (2n = 66), and 16S rRNA sequencing validated that CAMK cells originated fromhybrid snakehead, and the detection of kidney-specific antibodies suggested that it originated from kidney. .The culture was free from mycoplasma contamination, and the green fluorescent protein gene was effectively transfected into CAMK cells, indicating their potential use for in vitro gene expression investigations. Furthermore, qRT-PCR and immunofluorescence analysis revealed that HSHRV could replicate in CAMK cells, indicating that the cells were susceptible to the virus. Transmission electron microscopy revealed that the viral particles had bullet-like morphology. The replication efficiency of HSHRV was 107.33 TCID50/mL. Altogether, we successfully established and characterized a kidney cell line susceptible to the virus. These findings provide a valuable reference for further genetic and virological studies.

Network analysis of the proteome and peptidome sheds light on human milk as a biological system

Proteins and peptides found in human milk have bioactive potential to benefit the newborn and support healthy development. Research has been carried out on the health benefits of proteins and peptides, but many questions still need to be answered about the nature of these components, how they are formed, and how they end up in the milk. This study explored and elucidated the complexity of the human milk proteome and peptidome. Proteins and peptides were analyzed with non-targeted nanoLC-Orbitrap-MS/MS in a selection of 297 milk samples from the CHILD Cohort Study. Protein and peptide abundances were determined, and a network was inferred using Gaussian graphical modeling (GGM), allowing an investigation of direct associations. This study showed that signatures of (1) specific mechanisms of transport of different groups of proteins, (2) proteolytic degradation by proteases and aminopeptidases, and (3) coagulation and complement activation are present in human milk. These results show the value of an integrated approach in evaluating large-scale omics data sets and provide valuable information for studies that aim to associate protein or peptide profiles from biofluids such as milk with specific physiological characteristics.

Kidney injury molecule-1 and podocalyxin dysregulation in an arginine vasopressin induced rodent model of preeclampsia

OBJECTIVE

To assess renal injury in an arginine vasopressin (AVP) rodent model of preeclampsia.

STUDY DESIGN

Urinary expression of kidney injury molecule-1 (KIM-1), urinary protein and creatinine was determined in rodents (n = 24; pregnant AVP, pregnant saline, non-pregnant AVP and non-pregnant saline), which received a continuous dose of either AVP or saline via subcutaneous mini osmotic pumps for 18 days, using a Multiplex kidney toxicity immunoassay. Renal morphology was assessed using haematoxylin and eosin staining and transmission electron microscopy. The immunolocalization of KIM-1 and podocalyxin was qualitatively evaluated using immunohistochemistry.

RESULTS

Urinary KIM-1 and urinary protein levels were significantly increased in treated vs. untreated rats on gestational days 8 (p < 0.05), 14 (p < 0.001) and 18 (p < 0.001). The pregnant rats displayed a lower trend of creatinine compared to the non-pregnant groups, albeit non-significantly. KIM-1 was immunolocalized in the proximal convoluted tubules in AVP treated vs. untreated groups. In contrast, podocalyxin was weakly immunostained within glomeruli of pregnant AVP treated vs. pregnant untreated rats. Histological evaluation revealed reduced Bowman's space, with some tubular and blood vessel necrosis in the pregnant treated group. Ultrastructural observations included effacement and fusion of podocyte foot processes, glomerular basement membrane abnormalities, podocyte nuclear crenations, mitochondrial oedema and cristae degeneration with cytoplasmic lysis within treated tissue.

CONCLUSION

Our findings demonstrate region-specific kidney injury particularly glomerular impairment and endothelial injury in AVP-treated rats. The findings highlight the utility of this model in studying the mechanisms driving renal damage in a rodent model of preeclampsia.

Actin cytoskeleton in angiogenesis

Actin, one of the most abundant intracellular proteins in mammalian cells, is a critical regulator of cell shape and polarity, migration, cell division, and transcriptional response. Angiogenesis, or the formation of new blood vessels in the body is a well-coordinated multi-step process. Endothelial cells lining the blood vessels acquire several new properties such as front-rear polarity, invasiveness, rapid proliferation and motility during angiogenesis. This is achieved by changes in the regulation of the actin cytoskeleton. Actin remodelling underlies the switch between the quiescent and angiogenic state of the endothelium. Actin forms endothelium-specific structures that support uniquely endothelial functions. Actin regulators at endothelial cell-cell junctions maintain the integrity of the blood-tissue barrier while permitting trans-endothelial leukocyte migration. This review focuses on endothelial actin structures and less-recognised actin-mediated endothelial functions. Readers are referred to other recent reviews for the well-recognised roles of actin in endothelial motility, barrier functions and leukocyte transmigration. Actin generates forces that are transmitted to the extracellular matrix resulting in vascular matrix remodelling. In this review, we attempt to synthesize our current understanding of the roles of actin in vascular morphogenesis. We speculate on the vascular bed specific differences in endothelial actin regulation and its role in the vast heterogeneity in endothelial morphology and function across the various tissues of our body.

Trafficking in blood vessel development

Blood vessels demonstrate a multitude of complex signaling programs that work in concert to produce functional vasculature networks during development. A known, but less widely studied, area of endothelial cell regulation is vesicular trafficking, also termed sorting. After moving through the Golgi apparatus, proteins are shuttled to organelles, plugged into membranes, recycled, or degraded depending on the internal and extrinsic cues. A snapshot of these protein-sorting systems can be viewed as a trafficking signature that is not only unique to endothelial tissue, but critically important for blood vessel form and function. In this review, we will cover how vesicular trafficking impacts various aspects of angiogenesis, such as sprouting, lumen formation, vessel stabilization, and secretion, emphasizing the role of Rab GTPase family members and their various effectors.

Single-Cell RNA Sequencing of Human Corpus Cavernosum Reveals Cellular Heterogeneity Landscapes in Erectile Dysfunction

PURPOSE

To assess the diverse cell populations of human corpus cavernosum in patients with severe erectile dysfunction (ED) at the single-cell level.

METHODS

Penile tissues collected from three patients were subjected to single-cell RNA sequencing using the BD Rhapsody™ platform. Common bioinformatics tools were used to analyze cellular heterogeneity and gene expression profiles from generated raw data, including the packages Seurat, Monocle, and CellPhoneDB.

RESULTS

Disease-related heterogeneity of cell types was determined in the cavernous tissue such as endothelial cells (ECs), smooth muscle cells, fibroblasts, and immune cells. Reclustering analysis of ECs identified an arteriole ECs subcluster and another one with gene signatures of fibroblasts. The proportion of fibroblasts was higher than the other cell populations and had the most significant cellular heterogeneity, in which a distinct subcluster co-expressed endothelial markers. The transition trajectory of differentiation from smooth muscle cells into fibroblasts was depicted using the pseudotime analysis, suggesting that the expansion of corpus cavernosum is possibly compromised as a result of fibrosis. Cell-cell communications among ECs, smooth muscle cells, fibroblasts, and macrophages were robust, which indicated that inflammation may also have a crucial role in the development of ED.

CONCLUSIONS

Our study has demonstrated a comprehensive single-cell atlas of cellular components in human corpus cavernosum of ED, providing in-depth insights into the pathogenesis. Future research is warranted to explore disease-specific alterations for individualized treatment of ED.

Cardiac forces regulate zebrafish heart valve delamination by modulating Nfat signaling

In the clinic, most cases of congenital heart valve defects are thought to arise through errors that occur after the endothelial–mesenchymal transition (EndoMT) stage of valve development. Although mechanical forces caused by heartbeat are essential modulators of cardiovascular development, their role in these later developmental events is poorly understood. To address this question, we used the zebrafish superior atrioventricular valve (AV) as a model. We found that cellularized cushions of the superior atrioventricular canal (AVC) morph into valve leaflets via mesenchymal–endothelial transition (MEndoT) and tissue sheet delamination. Defects in delamination result in thickened, hyperplastic valves, and reduced heart function. Mechanical, chemical, and genetic perturbation of cardiac forces showed that mechanical stimuli are important regulators of valve delamination. Mechanistically, we show that forces modulate Nfatc activity to control delamination. Together, our results establish the cellular and molecular signature of cardiac valve delamination in vivo and demonstrate the continuous regulatory role of mechanical forces and blood flow during valve formation.

Why do developing zebrafish atrioventricular heart valves become hyperplastic under certain hemodynamic conditions? This study suggests that part of the answer lies in how the mechanosensitive Nfat pathway regulates the valve mesenchymal-to-endothelial transition.

The Glomerular Endothelium Restricts Albumin Filtration

Inflammatory activation and/or dysfunction of the glomerular endothelium triggers proteinuria in many systemic and localized vascular disorders. Among them are the thrombotic microangiopathies, many forms of glomerulonephritis, and acute inflammatory episodes like sepsis and COVID-19 illness. Another example is the chronic endothelial dysfunction that develops in cardiovascular disease and in metabolic disorders like diabetes. While the glomerular endothelium is a porous sieve that filters prodigious amounts of water and small solutes, it also bars the bulk of albumin and large plasma proteins from passing into the glomerular filtrate. This endothelial barrier function is ascribed predominantly to the endothelial glycocalyx with its endothelial surface layer, that together form a relatively thick, mucinous coat composed of glycosaminoglycans, proteoglycans, glycolipids, sialomucins and other glycoproteins, as well as secreted and circulating proteins. The glycocalyx/endothelial surface layer not only covers the glomerular endothelium; it extends into the endothelial fenestrae. Some glycocalyx components span or are attached to the apical endothelial cell plasma membrane and form the formal glycocalyx. Other components, including small proteoglycans and circulating proteins like albumin and orosomucoid, form the endothelial surface layer and are bound to the glycocalyx due to weak intermolecular interactions. Indeed, bound plasma albumin is a major constituent of the endothelial surface layer and contributes to its barrier function. A role for glomerular endothelial cells in the barrier of the glomerular capillary wall to protein filtration has been demonstrated by many elegant studies. However, it can only be fully understood in the context of other components, including the glomerular basement membrane, the podocytes and reabsorption of proteins by tubule epithelial cells. Discovery of the precise mechanisms that lead to glycocalyx/endothelial surface layer disruption within glomerular capillaries will hopefully lead to pharmacological interventions that specifically target this important structure.

Endothelial Recovery in Bare Metal Stents and Drug-Eluting Stents on a Single-Cell Level

[Figure: see text].

Atypical focal segmental glomerulosclerosis associated with a new PODXL nonsense variant

Background

Podocalyxin (PODXL) is a highly sialylated adhesion glycoprotein that plays an important role in podocyte's physiology. Recently, missense and nonsense dominant variants in the PODXL gene have been associated with focal segmental glomerulosclerosis (FSGS), a leading cause of nephrotic syndrome and kidney failure. Their histologic description, however, was superficial or absent.

Methods

We performed exome sequencing on a three‐generation family affected by an atypical glomerular nephropathy and characterized the disease by light and electron microscopy.

Results

The disease was characterized by FSGS features and glomerular basement membrane duplication. Six family members displayed chronic proteinuria, ranging from mild manifestations without renal failure, to severe forms with end‐stage renal disease. Exome sequencing of affected twin sisters, their affected mother, healthy father, and healthy maternal uncle revealed a new nonsense variant cosegregating with the disease (c.1453C>T, NM_001018111) in the PODXL gene, which is known to be expressed in the kidney and to cause nephropathy when mutated. The variant is predicted to lead to a premature stop codon (p.Q485*) that results in the loss of the intracytoplasmic tail of the protein.

Conclusion

This is the first description of a peculiar association combining a PODXL stop‐gain variant and both FSGS and membranoproliferative glomerulonephritis features, described by light and electron microscopy.

Spatiotemporal single-cell RNA sequencing of developing chicken hearts identifies interplay between cellular differentiation and morphogenesis

Single-cell RNA sequencing is a powerful tool to study developmental biology but does not preserve spatial information about tissue morphology and cellular interactions. Here, we combine single-cell and spatial transcriptomics with algorithms for data integration to study the development of the chicken heart from the early to late four-chambered heart stage. We create a census of the diverse cellular lineages in developing hearts, their spatial organization, and their interactions during development. Spatial mapping of differentiation transitions in cardiac lineages defines transcriptional differences between epithelial and mesenchymal cells within the epicardial lineage. Using spatially resolved expression analysis, we identify anatomically restricted expression programs, including expression of genes implicated in congenital heart disease. Last, we discover a persistent enrichment of the small, secreted peptide, thymosin beta-4, throughout coronary vascular development. Overall, our study identifies an intricate interplay between cellular differentiation and morphogenesis.

The role of serum podocalyxin levels in recurrent pregnancy loss

OBJECTIVE

To measure serum levels of podocalyxin (PODXL) in recurrent miscarriages as a marker of vascular endothelial dysfunction.

STUDY DESIGN

In this case-control study, women who were hospitalized for singleton first-trimester pregnancy terminations due to missed abortion, anembryonic pregnancy, and inevitable abortion were included. There were 24 patients who were admitted for the first pregnancy termination, 39 patients who were admitted for recurrent pregnancy loss (RPL), and 25 fetal cardiac activity positive patients as the control group. Demographic features, medical and obstetric histories were recorded. The measurements of serum PODXL were done by a human enzyme-linked immunosorbent assay kit.

RESULTS

Serum PODXL levels were found to be significantly higher in the RPL group than the control group and the first time miscarriage group (13.82 [10.09-113.54] vs. 11.78 [9.25-48.80], p = 0.016 and 13.82 [10.09-113.54] vs. 11.99 [8.20-20.47], p = 0.003; respectively). Serum PODXL levels were not statistically significantly different between the first miscarriage and the control group (p = 0.62). There were positive correlation between serum PODXL levels and the number of gravida and the number of miscarriages (r = 0.217, p = 0.042, and r = 0.291, p = 0.006; respectively).

CONCLUSION

Recurrent miscarriage patients had higher serum levels of PODXL than both normal pregnancies and first-time miscarriages. Our results suggest that maternal endothelial dysfunction might have a role in recurrent pregnancy losses.

PODO447: a novel antibody to a tumor-restricted epitope on the cancer antigen podocalyxin

Background

The success of new targeted cancer therapies has been dependent on the identification of tumor-specific antigens. Podocalyxin (Podxl) is upregulated on tumors with high metastatic index and its presence is associated with poor outcome, thus emerging as an important prognostic and theragnostic marker in several human cancers. Moreover, in human tumor xenograft models, Podxl expression promotes tumor growth and metastasis. Although a promising target for immunotherapy, the expression of Podxl on normal vascular endothelia and kidney podocytes could hamper efforts to therapeutically target this molecule. Since pathways regulating post-translational modifications are frequently perturbed in cancer cells, we sought to produce novel anti-Podxl antibodies (Abs) that selectively recognize tumor-restricted glycoepitopes on the extracellular mucin domain of Podxl.

Methods

Splenic B cells were isolated from rabbits immunized with a Podxl-expressing human tumor cell line. Abs from these B cells were screened for potent reactivity to Podxl⁺ neoplastic cell lines but not Podxl⁺ primary endothelial cells. Transcripts encoding heavy and light chain variable regions from promising B cells were cloned and expressed as recombinant proteins. Tumor specificity was assessed using primary normal tissue and an ovarian cancer tissue microarray (TMA). Mapping of the tumor-restricted epitope was performed using enzyme-treated human tumor cell lines and a glycan array.

Results

One mAb (PODO447) showed strong reactivity with a variety of Podxl+ tumor cell lines but not with normal primary human tissue including Podxl+ kidney podocytes and most vascular endothelia. Screening of an ovarian carcinoma TMA (219 cases) revealed PODO447 reactivity with the majority of tumors, including 65% of the high-grade serous histotype. Subsequent biochemical analyses determined that PODO447 reacts with a highly unusual terminal N-acetylgalactosamine beta-1 (GalNAcβ1) motif predominantly found on the Podxl protein core. Finally, Ab–drug conjugates showed specific efficacy in killing tumor cells in vitro.

Conclusions

We have generated a novel and exquisitely tumor-restricted mAb, PODO447, that recognizes a glycoepitope on Podxl expressed at high levels by a variety of tumors including the majority of life-threatening high-grade serous ovarian tumors. Thus, tumor-restricted PODO447 exhibits the appropriate specificity for further development as a targeted immunotherapy.

Flow-Induced Transcriptomic Remodeling of Endothelial Cells Derived From Human Induced Pluripotent Stem Cells

The vascular system is essential for the development and function of all organs and tissues in our body. The molecular signature and phenotype of endothelial cells (EC) are greatly affected by blood flow-induced shear stress, which is a vital component of vascular development and homeostasis. Recent advances in differentiation of ECs from human induced pluripotent stem cells (hiPSC) have enabled development of in vitro experimental models of the vasculature containing cells from healthy individuals or from patients harboring genetic variants or diseases of interest. Here we have used hiPSC-derived ECs and bulk- and single-cell RNA sequencing to study the effect of flow on the transcriptomic landscape of hiPSC-ECs and their heterogeneity. We demonstrate that hiPS-ECs are plastic and they adapt to flow by expressing known flow-induced genes. Single-cell RNA sequencing showed that flow induced a more homogenous and homeostatically more stable EC population compared to static cultures, as genes related to cell polarization, barrier formation and glucose and fatty acid transport were induced. The hiPS-ECs increased both arterial and venous markers when exposed to flow. Interestingly, while in general there was a greater increase in the venous markers, one cluster with more arterial-like hiPS-ECs was detected. Single-cell RNA sequencing revealed that not all hiPS-ECs are similar even after sorting, but exposing them to flow increases their homogeneity. Since hiPS-ECs resemble immature ECs and demonstrate high plasticity in response to flow, they provide an excellent model to study vascular development.

PODXL might be a new prognostic biomarker in various cancers: a meta-analysis and sequential verification with TCGA datasets

ABSRACT

BACKGROUND: Several studies have investigated the associations between the podocalyxin-like protein (PODXL) expression quantity or locations and cancers survival, but the results were far from conclusive. Therefore, we proceeded a meta-analysis on PODXL in various human cancers to find its prognostic value and followed confirmation using the TCGA datasets.

METHODS

We performed a systematic search, and 18 citations, including 5705 patients were pooled in meta-analysis. The results were verified with TCGA datasets.

RESULTS

Total eligible studies comprised 5705 patients with 10 types of cancer. And the result indicated that PODXL high-expression or membrane-expression were significantly related to poor overall survival (OS). However, subgroup analysis showed a significant association between high expressed PODXL and poor OS in the colorectal cancer, pancreatic cancer, urothelial bladder cancer, renal cell carcinoma and glioblastoma multiforme. Then, we validated the inference using TCGA datasets, and the consistent results were demonstrated in patients with pancreatic cancer, glioblastoma multiforme, gastric cancer, esophageal cancer and lung adenocarcinoma.

CONCLUSION

The result of meta-analysis showed that high expressed PODXL was significantly linked with poor OS in pancreatic cancer and glioblastoma multiforme, but not in gastric cancer, esophageal cancer or lung adenocarcinoma. And the membrane expression of PODXL might also associate with poor OS. PODXL may act as tumor promotor and may serve as a potential target for antitumor therapy.

Association of serum podocalyxin levels with peripheral arterial disease in patients with type 2 diabetes

OBJECTIVE

Renal podocalyxin is a marker for kidney diseases. Previous studies have shown the expression of serum podocalyxin (s-Podxl) in the endothelial cells of blood vessels. We aimed to investigate the association between s-podxl levels and peripheral arterial disease (PAD) in subjects with type 2 diabetes (T2DM).

SUBJECTS AND METHODS

Serum Podxl levels were analyzed in 69 subjects with normal glucose tolerance and PAD (NGT-PAD), 120 subjects with T2DM and PAD (D-PAD) and 36 subjects with T2DM without PAD (D-NPAD).

RESULTS

In D-PAD Patients, s-Podxl was significantly higher (17.67 ± 20.7 ng/mL) than in D-NPAD subjects (9.97 ± 5.34 ng/mL; P < 0.001). Subjects with NGT-PAD had significantly higher s-Podxl levels (15.34 ± 18.21 ng/mL), than D-NPAD patients (P < 0.001). Subjects with D-PAD and medial calcific sclerosis (MCS) had significantly higher s-Podxl levels compared to the same group but without MCS (P < 0.02). In D-PAD patients, MCS (P = 0.003) and glycosylated hemoglobin (P < 0.001) were the two variables that had the strongest prediction for s-Podxl as revealed by regression analysis. Multivariate regression showed that an increase of one standard deviation in s-Podxl was associated with an odds ratio of 3.4 (95% confidence interval = 2.2-4.6, P < 0.001) for the prevalence of PAD.

CONCLUSIONS

This is the first study showing an association between s-Podxl and PAD in patients with T2DM. S-Podxl was higher in D-PAD patients than in D-NPAD subjects. In NGT-PAD patients, s-Podxl was also higher than in D-NPAD patients. In patients with D-PAD, s-Podxl was positively associated with MCS.

Podocalyxin is required for maintaining blood-brain barrier function during acute inflammation

Podocalyxin (Podxl) is broadly expressed on the luminal face of most blood vessels in adult vertebrates, yet its function on these cells is poorly defined. In the present study, we identified specific functions for Podxl in maintaining endothelial barrier function. Using electrical cell substrate impedance sensing and live imaging, we found that, in the absence of Podxl, human umbilical vein endothelial cells fail to form an efficient barrier when plated on several extracellular matrix substrates. In addition, these monolayers lack adherens junctions and focal adhesions and display a disorganized cortical actin cytoskeleton. Thus, Podxl has a key role in promoting the appropriate endothelial morphogenesis required to form functional barriers. This conclusion is further supported by analyses of mutant mice in which we conditionally deleted a floxed allele of Podxl in vascular endothelial cells (vECs) using Tie2Cre mice (Podxl ^ΔTie2Cre). Although we did not detect substantially altered permeability in naïve mice, systemic priming with lipopolysaccharide (LPS) selectively disrupted the blood-brain barrier (BBB) in Podxl ^ΔTie2Cre mice. To study the potential consequence of this BBB breach, we used a selective agonist (TFLLR-NH₂) of the protease-activated receptor-1 (PAR-1), a thrombin receptor expressed by vECs, neuronal cells, and glial cells. In response to systemic administration of TFLLR-NH₂, LPS-primed Podxl ^ΔTie2Cre mice become completely immobilized for a 5-min period, coinciding with severely dampened neuroelectric activity. We conclude that Podxl expression by CNS tissue vECs is essential for BBB maintenance under inflammatory conditions.

ClampFISH detects individual nucleic acid molecules using click chemistry-based amplification

Methods for detecting single nucleic acids in cell and tissues, such as fluorescence in situ hybridization (FISH), are limited by relatively low signal intensity and nonspecific probe binding. Here we present click-amplifying FISH (clampFISH), a method for fluorescence detection of nucleic acids that achieves high specificity and high-gain (>400-fold) signal amplification. ClampFISH probes form a 'C' configuration upon hybridization to the sequence of interest in a double helical manner. The ends of the probes are ligated together using bio-orthogonal click chemistry, effectively locking the probes around the target. Iterative rounds of hybridization and click amplify the fluorescence intensity. We show that clampFISH enables the detection of RNA species with low-magnification microscopy and in RNA-based flow cytometry. Additionally, we show that the modular design of clampFISH probes allows multiplexing of RNA and DNA detection, that the locking mechanism prevents probe detachment in expansion microscopy, and that clampFISH can be applied in tissue samples.

Podocalyxin-like protein as a predictive biomarker for benefit of neoadjuvant chemotherapy in resectable gastric and esophageal adenocarcinoma

BACKGROUND

We have previously shown that podocalyxin-like protein (PODXL) is a prognostic biomarker for poor survival in gastric and esophageal adenocarcinoma treated with surgery up-front. The aim of the present study was to assess PODXL expression in tumors from patients treated with neoadjuvant ± adjuvant (i.e. preoperative with or without postoperative) chemotherapy, with regard to histopathologic response, time to recurrence (TTR) and overall survival (OS).

METHODS

The neoadjuvant cohort encompasses 148 consecutive patients who received neoadjuvant ± adjuvant chemotherapy for resectable gastric or esophageal adenocarcinoma between 2008 and 2014. Immunohistochemical expression of PODXL was assessed in pre-neoadjuvant biopsies, resected primary tumors and lymph node metastases. Histopathologic response was evaluated using the Chirieac grading. TTR and OS were estimated using Kaplan-Meier and Cox regression analyses. To investigate a potential predictive role for PODXL, the neoadjuvant cohort was pooled with the previously reported surgery up-front cohort.

RESULTS

The majority (> 95%) of the patients were treated with fluoropyrimidine- and oxaliplatin-based chemotherapy. Patients with high PODXL expression in their pre-neoadjuvant biopsies had a superior histopathologic response (notably 36% with no residual cancer cells) compared to those with negative or low PODXL expression, and were all recurrence-free at last follow-up. In the pooled cohort, no benefit of chemotherapy could be shown for PODXL negative cases, whereas PODXL positive (low or high) cases had a prolonged TTR and OS when treated with neoadjuvant ± adjuvant chemotherapy compared to surgery alone. The potential predictive role of PODXL was further strengthened for TTR in Cox regression analyses, especially for patients treated with neoadjuvant fluoropyrimidine and oxaliplatin for a minimum of 8 weeks, with a significant interaction term in both unadjusted (p = 0.006) and adjusted (p = 0.024) analyses. The interaction term was not statistically significant for overall survival.

CONCLUSIONS

Patients with resectable gastric or esophageal adenocarcinoma with high PODXL expression in their diagnostic biopsies have an excellent prognosis when treated with neoadjuvant ± adjuvant fluoropyrimidine- and oxaliplatin-based chemotherapy. If the suggested predictive role of PODXL for benefit of chemotherapy can be confirmed, patients with PODXL negative tumors could be spared chemotherapy and treated with surgery alone.

A Single-Cell Transcriptome Atlas of the Mouse Glomerulus

Background Three different cell types constitute the glomerular filter: mesangial cells, endothelial cells, and podocytes. However, to what extent cellular heterogeneity exists within healthy glomerular cell populations remains unknown.Methods We used nanodroplet-based highly parallel transcriptional profiling to characterize the cellular content of purified wild-type mouse glomeruli.Results Unsupervised clustering of nearly 13,000 single-cell transcriptomes identified the three known glomerular cell types. We provide a comprehensive online atlas of gene expression in glomerular cells that can be queried and visualized using an interactive and freely available database. Novel marker genes for all glomerular cell types were identified and supported by immunohistochemistry images obtained from the Human Protein Atlas. Subclustering of endothelial cells revealed a subset of endothelium that expressed marker genes related to endothelial proliferation. By comparison, the podocyte population appeared more homogeneous but contained three smaller, previously unknown subpopulations.Conclusions Our study comprehensively characterized gene expression in individual glomerular cells and sets the stage for the dissection of glomerular function at the single-cell level in health and disease.

Leukocyte-endothelial cell interaction is enhanced in podocalyxin-deficient mice

The highly sialoglycosylated extracellular domain of podocalyxin (Podxl) is a constituent of the endothelial glycocalyx of most blood vessels but it is unknown if Podxl plays a prominent role in the function of the glycocalyx as a regulator of leukocyte-endothelial adhesion. We have recently found that mice lacking Podxl in the vascular endothelium develop histological lesions compatible with severe vasculitis resulting in organ failure and premature death. In this work, we show that these mice have an increased quantity of resident leukocytes within the peritoneal cavity in both basal and inflammatory conditions. Adhesion of macrophagic cells to lung endothelial cells from Podxl-deficient mice was increased under inflammatory stimuli. Both, chemokine binding and chemokine-mediated adhesion of immune cells were significantly higher in Podxl-deficient endothelial cells. Moreover, glycocalyx function assessed by measuring the anticoagulant capacity of endothelial cell monolayers to inactivate thrombin was significantly altered in the absence of Podxl. Overall, the results suggest that Podxl is an essential component of the glycocalyx and has an important so far unknown role in preventing leukocyte-endothelial cell adhesion under resting and inflammatory conditions.

Promotion of Vascular Morphogenesis of Endothelial Cells Co-Cultured with Human Adipose-Derived Mesenchymal Stem Cells Using Polycaprolactone/Gelatin Nanofibrous Scaffolds

New blood vessel formation is essential for tissue regeneration to deliver oxygen and nutrients and to maintain tissue metabolism. In the field of tissue engineering, in vitro fabrication of new artificial vessels has been a longstanding challenge. Here we developed a technique to reconstruct a microvascular system using a polycaprolactone (PCL)/gelatin nanofibrous structure and a co-culture system. Using a simple electrospinning process, we fabricated three-dimensional mesh scaffolds to support the sprouting of human umbilical vein endothelial cells (HUVECs) along the electrospun nanofiber. The co-culture with adipose-derived mesenchymal stem cells (ADSCs) supported greater sprouting of endothelial cells (ECs). In a two-dimensional culture system, angiogenic cell assembly produced more effective direct intercellular interactions and paracrine signaling from ADSCs to assist in the vascular formation of ECs, compared to the influence of growth factor. Although vascular endothelial growth factor and sphingosine-1-phosphate were present during the culture period, the presence of ADSCs was the most important factor for the construction of a cell-assembled structure in the two-dimensional culture system. On the contrary, HUVECs co-cultured on PCL/gelatin nanofiber scaffolds produced mature and functional microvessel and luminal structures with a greater expression of vascular markers, including platelet endothelial cell adhesion molecule-1 and podocalyxin. Furthermore, both angiogenic factors and cellular interactions with ADSCs through direct contact and paracrine molecules contributed to the formation of enhanced engineered blood vessel structures. It is expected that the co-culture system of HUVECs and ADSCs on bioengineered PCL/gelatin nanofibrous scaffolds will promote robust and functional microvessel structures and will be valuable for the regeneration of tissue with restored blood vessels.

Serum podocalyxin levels correlate with carotid intima media thickness, implicating its role as a novel biomarker for atherosclerosis

Podocalyxin is a cell surface sialomucin, which is expressed in not only glomerular podocytes but also vascular endothelial cells. Urinary podocalyxin is used as a marker for glomerular disease. However, there are no reports describing serum podocalyxin (s-Podxl) levels. Therefore, the association between s-Podxl levels and clinical parameters were examined with 52 patients. s-Podxl level was evaluated using enzyme-linked immunosorbent assay. The median s-Podxl level was 14.2 ng/dL (interquartile range: 10.8–22.2 ng/dL). There were significant correlations (correlation coefficient: r > 0.2) of s-Podxl levels with carotid intima media thickness (IMT) (r = 0.30, p = 0.0307). Multiple logistic regression analysis showed that s-Podxl levels remained significantly associated with carotid IMT > 1 mm (OR: 1.15; 95% CI 1.02–1.31, p = 0.026) after adjustments for traditional cardiovascular risk factors such as age, sex, current smoking status, hypertension, dyslipidemias, and diabetes. In conclusion, s-Podxl is independently associated with carotid IMT and might be used as a novel biomarker for cardiovascular disease.

Mind the gap: mechanisms regulating the endothelial barrier

The endothelial barrier consists of intercellular contacts localized in the cleft between endothelial cells, which is covered by the glycocalyx in a sievelike manner. Both types of barrier-forming junctions, i.e. the adherens junction (AJ) serving mechanical anchorage and mechanotransduction and the tight junction (TJ) sealing the intercellular space to limit paracellular permeability, are tethered to the actin cytoskeleton. Under resting conditions, the endothelium thereby builds a selective layer controlling the exchange of fluid and solutes with the surrounding tissue. However, in the situation of an inflammatory response such as in anaphylaxis or sepsis intercellular contacts disintegrate in post-capillary venules leading to intercellular gap formation. The resulting oedema can cause shock and multi-organ failure. Therefore, maintenance as well as coordinated opening and closure of interendothelial junctions is tightly regulated. The two principle underlying mechanisms comprise spatiotemporal activity control of the small GTPases Rac1 and RhoA and the balance of the phosphorylation state of AJ proteins. In the resting state, junctional Rac1 and RhoA activity is enhanced by junctional components, actin-binding proteins, cAMP signalling and extracellular cues such as sphingosine-1-phosphate (S1P) and angiopoietin-1 (Ang-1). In addition, phosphorylation of AJ components is prevented by junction-associated phosphatases including vascular endothelial protein tyrosine phosphatase (VE-PTP). In contrast, inflammatory mediators inhibiting cAMP/Rac1 signalling cause strong activation of RhoA and induce AJ phosphorylation finally leading to endocytosis and cleavage of VE-cadherin. This results in dissolution of TJs the outcome of which is endothelial barrier breakdown.

Loss of podocalyxin causes a novel syndromic type of congenital nephrotic syndrome

Many cellular structures directly imply specific biological functions. For example, normal slit diaphragm structures that extend from podocyte foot processes ensure the filtering function of renal glomeruli. These slits are covered by a number of surface proteins, such as nephrin, podocin, podocalyxin and CD2AP. Here we report a human patient presenting with congenital nephrotic syndrome, omphalocele and microcoria due to two loss-of-function mutations in PODXL, which encodes podocalyxin, inherited from each parent. This set of symptoms strikingly mimics previously reported mouse Podxl^−/− embryos, emphasizing the essential function of PODXL in mammalian kidney development and highlighting this patient as a human PODXL-null model. The results underscore the utility of current genomics approaches to provide insights into the genetic mechanisms of human disease traits through molecular diagnosis.

Gene-Edited Human Kidney Organoids Reveal Mechanisms of Disease in Podocyte Development

A critical event during kidney organogenesis is the differentiation of podocytes, specialized epithelial cells that filter blood plasma to form urine. Podocytes derived from human pluripotent stem cells (hPSC-podocytes) have recently been generated in nephron-like kidney organoids, but the developmental stage of these cells and their capacity to reveal disease mechanisms remains unclear. Here, we show that hPSC-podocytes phenocopy mammalian podocytes at the capillary loop stage (CLS), recapitulating key features of ultrastructure, gene expression, and mutant phenotype. hPSC-podocytes in vitro progressively establish junction-rich basal membranes (nephrin⁺ podocin⁺ ZO-1⁺ ) and microvillus-rich apical membranes (podocalyxin⁺ ), similar to CLS podocytes in vivo. Ultrastructural, biophysical, and transcriptomic analysis of podocalyxin-knockout hPSCs and derived podocytes, generated using CRISPR/Cas9, reveals defects in the assembly of microvilli and lateral spaces between developing podocytes, resulting in failed junctional migration. These defects are phenocopied in CLS glomeruli of podocalyxin-deficient mice, which cannot produce urine, thereby demonstrating that podocalyxin has a conserved and essential role in mammalian podocyte maturation. Defining the maturity of hPSC-podocytes and their capacity to reveal and recapitulate pathophysiological mechanisms establishes a powerful framework for studying human kidney disease and regeneration. Stem Cells 2017;35:2366-2378.