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Background We report follow-up data from an ongoing prospective cohort study of COVID-19 in pediatric kidney transplantation through the Improving Renal Outcomes Collaborative (IROC). Methods Patient-level data from the IROC registry were combined with testing, indication, and outcomes data collected to describe the epidemiology of COVID testing, treatment, and clinical outcomes; determine the incidence of a positive COVID-19 test; describe rates of COVID-19 testing; and assess for clinical predictors of a positive COVID-19 test. Results From September 2020 to February 2021, 21 centers that care for 2690 patients submitted data from 648 COVID-19 tests on 465 patients. Most patients required supportive care only and were treated as outpatients, 16% experienced inpatient care, and 5% experienced intensive care. Allograft complications were rare, with acute kidney injury most common (7%). There was 1 case of respiratory failure and 1 death attributed to COVID-19. Twelve centers that care for 1730 patients submitted complete testing data on 351 patients. The incidence of COVID-19 among patients at these centers was 4%, whereas the incidence among tested patients was 19%. Risk factors to predict a positive COVID-19 test included age > 12 years, symptoms consistent with COVID-19, and close contact with a confirmed case of COVID-19. Conclusions Despite the increase in testing and positive tests over this study period, the incidence of allograft loss or death related to COVID-19 remained extremely low, with allograft loss or death each occurring in < 1% of COVID-19-positive patients and in less than < 0.1% of all transplant patients within the IROC cohort. Graphical abstract A higher resolution version of the Graphical abstract is available as Supplementary information, Author(s): Charles Jr. Varnell [sup.1] [sup.2] , Lyndsay A. Harshman [sup.3] , Chunyan Liu [sup.1] , Laurie Smith [sup.1] , Samhar Al-Akash [sup.4] , Gina-Marie Barletta [sup.5] , Paul Brakeman [...]

Background/Objective: We sought to understand healthcare utilization and barriers to care among youth with chronic illness who interact frequently with the healthcare system. Methods: This was a retrospective analysis of healthcare utilization for youth ≤25 years of age with chronic illness during one calendar year (1 January 2021–31 December 2021) in a single urban academic healthcare system. Inclusion criteria were (1) having at least one healthcare encounter in the calendar year of 2021 and (2) having at least six healthcare encounters over the preceding 3-year period or having a qualifying chronic illness. Demographic and clinical characteristics were collected along with self-reported and derived social determinants of health. Univariable and multivariable regression models were created to identify predictors of missed clinic visits, telehealth use, and activated patient portal accounts. Results: The cohort (N = 14,245) was demographically, clinically, and socioeconomically diverse. The youth had frequent clinic visits (median 9, IQR 4–18), multiple subspecialty care referrals (median 4, 1–8), were prescribed multiple medications (median 6, 3–10), and a high proportion received emergency department (18%) or inpatient treatment (15%). Race and public insurance were significant predictors of missed clinic visits and telehealth use. Primary language was a significant predictor of patient portal activation. Conclusions: Youth with chronic illness who are high users of the healthcare system face a high burden of clinic, emergency room, and hospital visits, referrals, and medications. Systematic efforts to lower the healthcare burden and improve care access should address existing racial and socioeconomic disparities affecting this patient population, who are likely to need frequent healthcare over their lifetime. [ABSTRACT FROM AUTHOR]

Background/Objectives: Hope is a universal, multidimensional, and nuanced concept that may have specific meaning for young people living with chronic health conditions anticipated to last into adulthood. We previously identified definitions of hope for youth living with chronic health conditions derived from young people's and their caregivers' own words. Here, we aimed to develop a hope assessment tool to facilitate the future evaluation of interventions to support wellness and health for young people growing up with chronic health conditions; Methods: We developed Likert-type scale questions using the young people's and caregivers' definitions of hope and applied the think-aloud cognitive interview method to assess understanding and to inform sequential iteration. Interviews were recorded and insights from participant interviews were analyzed thematically. Results: In total, 11 youth (age 12–16 years) with various chronic health conditions completed surveys and interviews over three iteration cycles. Responses to the six-point Likert-scale questions ranged from 1 (none of the time) to 6 (all of the time) (median 5). All of the young people (n = 11) reported that they do things they enjoy, either all of the time or most of the time. In contrast, only 36% felt energetic, either all or most of the time. Three themes were identified: my body and hope; my identity, self-image, and hope; and my world and hope. Conclusions: In addition to gaining important feedback that allowed us to improve item word choice to maximize assessment tool understanding, we gained valuable insights into the multidimensional construct of hope. Thematic analysis revealed the importance of physical symptoms and identity to the meaning of hope in the context of a young person's life. Our new hope assessment tool derived from the young people's own definition of hope has face and content validity for use in clinical and research settings to evaluate hope among pediatric patients living with chronic health conditions. [ABSTRACT FROM AUTHOR]

Background: Coronavirus disease of 2019 (COVID-19) has disproportionately affected adults with kidney disease. Data regarding outcomes among children with kidney disease are limited. The North American Pediatric Renal Trials Collaborative Studies Registry (NAPRTCS) has followed children with chronic kidney disease (CKD) since 1987 at 87 participating centers. This study aimed to evaluate the impact of COVID-19 among participants enrolled in the three arms of the registry: CKD, dialysis, and transplant. Methods: This was a retrospective cohort study of COVID-19 among participants in the NAPRTCS CKD, dialysis, and transplant registries from 2020 to 2022. Where appropriate, t-tests, chi-square analyses, and univariate logistic regression were used to evaluate the data. Results: The cohort included 1505 NAPRTCS participants with recent data entry; 260 (17%) had documented COVID-19. Infections occurred in all three registry arms, namely, 10% (n = 29) in CKD, 11% (n = 67) in dialysis, and 26% (n = 164) in transplant. The majority of participants (75%) were symptomatic. Hospitalizations occurred in 17% (n = 5) of participants with CKD, 27% (n = 18) maintenance dialysis participants, and 26% (n = 43) of transplant participants. Fourteen percent (n = 4) of CKD participants and 10% (n = 17) of transplant participants developed acute kidney injury (AKI), and a total of eight participants (one CKD, seven transplant) required dialysis initiation. Among transplant participants with moderate to severe illness, 40–43% developed AKI and 29–40% required acute dialysis. There were no reported deaths. Conclusions: COVID-19 was documented in 17% of active NAPRTCS participants. While there was no documented mortality, the majority of participants were symptomatic, and a quarter required hospitalization. [ABSTRACT FROM AUTHOR]

Our objective was to examine serum ferritin trends after conversion to permanent vascular access (PVA) among children who started hemodialysis (HD) using tunneled cuffed catheters (TCC). Retrospective chart reviews were completed on 98 subjects from 20 pediatric HD centers. Serum ferritin levels were collected at the creation of PVA and for two years thereafter. There were 11 (11%) arteriovenous grafts (AVG) and 87 (89%) arteriovenous fistulae (AVF). Their mean TCC use was 10.4 ± 17.3 months. Serum ferritin at PVA creation was elevated at 562.64 ± 492.34 ng/mL, increased to 753.84 ± 561.54 ng/mL (p = < 0.001) in the first year and remained at 759.60 ± 528.11 ng/mL in the second year (p = 0.004). The serum ferritin levels did not show a statistically significant linear association with respective serum hematocrit values. In a multiple linear regression model, there were three predictors of serum ferritin during the first year of follow-up: steroid-resistant nephrotic syndrome as primary etiology (p = 0.035), being from a center that enrolled >10 cases (p = 0.049) and baseline serum ferritin level (p = 0.017). Increasing serum ferritin after conversion to PVA is concerning. This increase is not associated with serum hematocrit trends. Future studies should investigate the correlation of serum transferrin saturation and ferritin levels in pediatric HD patients. [ABSTRACT FROM AUTHOR]

Development of the nephron requires conversion of the metanephric mesenchyme into tubular epithelial structures with specifically organized intercellular junctions. The nectin proteins area family of transmembrane proteins that dimerize to form intercellular junctional complexes between epithelial cells. In this study, we demonstrate that nectin junctions appear during the earliest stages of epithelial cell morphogenesis in the murine nephron concurrently with the transition of mesenchymal cells into epithelial cells. We have defined the role of nectin during epithelial cell morphogenesis by studying nectin in a three-dimensional culture of Madin-Darby canine kidney (MDCK) cells. In a three-dimensional culture of MDCK cells grown in purified type 1 collagen, expression of a dominant negative form of nectin causes disruption of the formation of cell polarity and disruption of tight junction (TJ) formation, as measured by zonula occludens-1 (ZO-1) localization. In MDCK cells cultured in Matrigel, exogenous expression of nectin-1 causes disruption of normal epithelial cell cyst formation and decreased apoptosis. These data demonstrate that nectins play an important role in normal epithelial cell morphogenesis and may play a role in mesenchyrnal-to-epithelial transition during nephrogenesis by providing an antiapoptotic signal and promoting the formation of TJs and cell polarity. cell polarity; three-dimensional cell culture: PAR-3

Epithelial cells are characterized by the ability to form sheets of cells that surround fluid-filled lumens. Cells in these sheets exhibit a characteristic subcellular polarity, with an apical pole that faces the lumen and a basolateral pole that is in contact with other cells and the extracellular matrix (ECM). To investigate the signaling events required for polarization and lumen formation, we have taken advantage of the ability of Madin-Darby canine kidney (MDCK) cells to dynamically remodel their polarity in response to changes in ECM cues. When MDCK cells are grown in suspension culture, they form multicellular 'inside-out' cysts with apical proteins found on the peripheral surface and basolateral markers on the interior surface. When these inside-out cysts are embedded in ECM, they rapidly reorient their polarity: apical proteins become localized to the inside surface, and basolateral proteins are found on the surface that contacts ECM. Here we have characterized the signaling requirements for these early molecular reorientation events. Specifically, expression of a dominant-negative form of Rac1 (DN-Rac1) blocks the reorientation of polarity. Phosphoinositide 3'-kinase is required for apical membrane protein remodeling from the initial apical membrane surface. Cells expressing DN-Rac1 fail to detectably activate the PI 3-kinase/protein kinase B pathway. Last, we found that atypical protein kinase C (aPKC) is also required for reorientation of polarity, since an inhibitor of atypical PKC blocks reorientation. This effect cannot be overcome by constitutively active Rac1, demonstrating that both Rac1 and atypical PKC are required for reorientation of cellular polarity. cell polarity; three-dimensional cell culture; Rac1; phosphoinositide 3-kinase; atypical protein kinase C

Background: Dialysis in children as well as adults is prescribed to achieve a target spKt/Vurea, where Vurea is the volume of distribution of urea. Waste solute production may however be more closely correlated with body surface area (BSA) than Vurea which rises in proportion with body weight. Plasma levels of waste solutes may thus be higher in smaller patients when targeting spKt/Vurea since they have higher BSA relative to body weight. This study measured levels of pseudouridine (PU), a novel marker solute whose production is closely proportional to BSA, to test whether prescription of dialysis to a target spKt/Vurea results in higher plasma levels of PU in smaller children. Methods: PU and urea nitrogen (ureaN) were measured in plasma and dialysate at the midweek hemodialysis session in 20 pediatric patients, with BSA ranging from 0.65–1.87m2. Mathematical modeling was employed to estimate solute production rates and average plasma solute levels. Results: The dialytic clearance (Kd) of PU was proportional to that of ureaN (average KdPU/KdUreaN 0.69 ± 0.13, r2 0.84, p < 0.001). Production of PU rose in proportion with BSA (r2 0.57, p < 0.001). The pretreatment plasma level of PU was significantly higher in smaller children (r2 0.20, p = 0.051) while the pretreatment level of ureaN did not vary with size. Conclusions: Prescribing dialysis based on urea kinetics may leave uremic solutes at higher levels in small children. Measurement of a solute produced proportional to BSA may provide a better index of dialysis adequacy than measurement of urea. [ABSTRACT FROM AUTHOR]

In many types of tubules, continuity of the lumen is paramount to tubular function, yet how tubules generate lumen continuity in vivo is not known. We recently found that the F-actin-binding protein afadin is required for lumen continuity in developing renal tubules, though its mechanism of action remains unknown. Here, we demonstrate that afadin is required for lumen continuity by orienting the mitotic spindle during cell division. Using an in vitro 3D cyst model, we find that afadin localizes to the cell cortex adjacent to the spindle poles and orients the mitotic spindle. In tubules, cell division may be oriented relative to two axes: longitudinal and apical-basal. Unexpectedly, in vivo examination of early-stage developing nephron tubules reveals that cell division is not oriented in the longitudinal (or planar-polarized) axis. However, cell division is oriented perpendicular to the apicalbasal axis. Absence of afadin in vivo leads to misorientation of apicalbasal cell division in nephron tubules. Together, these results support a model whereby afadin determines lumen placement by directing apical-basal spindle orientation, resulting in a continuous lumen and normal tubule morphogenesis. [ABSTRACT FROM AUTHOR]

Most current microfluidic cell culture systems are integrated single use devices. This can limit throughput and experimental design options, particularly for epithelial cells, which require significant time in culture to obtain a fully differentiated phenotype. In addition, epithelial cells require a porous growth substrate in order to fully polarize their distinct apical and basolateral membranes. We have developed a modular microfluidic system using commercially available porous culture inserts to evaluate polarized epithelial cells under physiologically relevant fluid flow conditions. The cell-support for the bioreactor is a commercially available microporous membrane that is ready to use in a 6-well format, allowing for cells to be seeded in advance in replicates and evaluated for polarization and barrier function prior to experimentation. The reusable modular system can be easily assembled and disassembled using these mature cells, thus improving experimental throughput and minimizing fabrication requirements. The bioreactor consists of an apical microfluidic flow path and a static basolateral chamber that is easily accessible from the outside of the device. The basolateral chamber acts as a reservoir for transport across the cell layer. We evaluated the effect of initiation of apical shear flow on short-term intracellular signaling and mRNA expression using primary human renal epithelial cells (HRECs). Ten min and 5 h after initiation of apical fluid flow over a stable monolayer of HRECs, cells demonstrated increased phosphorylation of extracellular signal-related kinase and increased expression of interleukin 6 (IL-6) mRNA, respectively. This bioreactor design provides a modular platform with rapid experimental turn-around time to study various epithelial cell functions under physiologically meaningful flow conditions. [ABSTRACT FROM AUTHOR]

The formation of epithelial tissues requires both the generation of apical-basal polarity and the coordination of this polarity between neighbouring cells to form a central lumen. During de novo lumen formation, vectorial membrane transport contributes to the formation of a singular apical membrane, resulting in the contribution of each cell to only a single lumen. Here, from a functional screen for genes required for three-dimensional epithelial architecture, we identify key roles for synaptotagmin-like proteins 2-a and 4-a (Slp2-a/4-a) in the generation of a single apical surface per cell. Slp2-a localizes to the luminal membrane in a PtdIns(4,5)P2-dependent manner, where it targets Rab27-loaded vesicles to initiate a single lumen. Vesicle tethering and fusion is controlled by Slp4-a, in conjunction with Rab27/Rab3/Rab8 and the SNARE syntaxin-3. Together, Slp2-a/4-a coordinate the spatiotemporal organization of vectorial apical transport to ensure that only a single apical surface, and thus the formation of a single lumen, occurs per cell. [ABSTRACT FROM AUTHOR]

Group I metabotropic glutamate receptors (mGluRs), including mGluR1 and mGluR5, are G protein-coupled receptors (GPCRs) that are expressed at excitatory synapses in brain and spinal cord. GPCRs are often negatively regulated by specific G protein-coupled receptor kinases and subsequent binding of arrestin-like molecules. Here we demonstrate an alternative mechanism in which group I mGluRs are negatively regulated by proline-directed kinases that phosphorylate the binding site for the adaptor protein Homer, and thereby enhance mGluR-Homer binding to reduce signaling. This mechanism is dependent on a multidomain scaffolding protein, Preso1, that binds mGluR, Homer and proline-directed kinases and that is required for their phosphorylation of mGluR at the Homer binding site. Genetic ablation of Preso1 prevents dynamic phosphorylation of mGluR5, and Preso1?/? mice exhibit sustained, mGluR5-dependent inflammatory pain that is linked to enhanced mGluR signaling. Preso1 creates a microdomain for proline-directed kinases with broad substrate specificity to phosphorylate mGluR and to mediate negative regulation. [ABSTRACT FROM AUTHOR]

The article investigates the cellular and molecular mechanisms of renal repair and recovery after acute kidney injury (AKI) using data from published research articles. Findings indicate that proliferation of tubular epithelial cells and stem cell populations are involved in renal repair in animal models of AKI. It was also found out that growth factors play significant role in renal repair process in animals but not in human, and that endothelium plays a critical role in AKI pathogenesis.

Defects in the development or maintenance of tubule diameter correlate with polycystic kidney disease. Here, we report that absence of the cadherin regulator p120 catenin (p120ctn) from the renal mesenchyme prior to tubule formation leads to decreased cadherin levels with abnormal morphologies of early tubule structures and developing glomeruli. In addition, mutant mice develop cystic kidney disease, with markedly increased tubule diameter and cellular proliferation, and detached luminal cells only in proximal tubules. The p120ctn homolog Arvcf is specifically absent from embryonic proximal tubules, consistent with the specificity of the proximal tubular phenotype. p120ctn knockdown in renal epithelial cells in 3D culture results in a similar cystic phenotype with reduced levels of E-cadherin and active RhoA. We find that E-cadherin knockdown, but not RhoA inhibition, phenocopies p120ctn knockdown. Taken together, our data show that p120ctn is required for early tubule and glomerular morphogenesis, as well as control of luminal diameter, probably through regulation of cadherins. [ABSTRACT FROM AUTHOR]

Epithelial cells are polarized, with an apical surface facing a lumen or outer surface and a basolateral surface facing other cells and extracellular matrix (ECM). Hallmarks of epithelial carcinogenesis include loss of polarity, as well as uncontrolled proliferation and resistance to apoptosis. Are these features controlled by a common molecular mechanism? The partitioning-defective 3 (PAR3)-PAR6-atypical PKC (aPKC) complex is a master regulator that controls polarization in many animal cells. Here we show that PAR6 is involved in apoptosis by regulating aPKC and glycogen synthase kinase 3β(GSK-3β) activity. During epithelial morphogenesis in 3D culture of Madin-Darby canine kidney (MDCK) cells, expression of an N-terminally deleted PAR6 (PAR6 δ N) leads to a significant increase in caspase-dependent cell death by downregulating aPKC activity. Accordingly, inhibition of aPKC in wild-type (WT) MDCK cells with either a cell-permeable PKCζ pseudosubstrate or RNAi promotes apoptosis, which suggests that PAR6 regulates apoptosis via an aPKC-mediated pathway. GSK-3β, a substrate of aPKC, is hyper- activated by expressing PAR6 δ N. GSK-3β inhibitors block PAR6 δ N-induced apoptosis while expression of constitutively active GSK- 3β S9A) promotes apoptosis, which is rescued by ectopic expression of aPKC. We conclude that a PAR6-aPKC-GSK-3β mechanism links cell polarity and apoptosis. [ABSTRACT FROM AUTHOR]