Hydrogel-Mediated Local Delivery of Induced Nephron Progenitor Cell-Sourced Molecules as a Cell-Free Approach for Acute Kidney Injury.

Acute kidney injury (AKI) constitutes a severe condition characterized by a sudden decrease in kidney function. Utilizing lineage-restricted stem/progenitor cells, directly reprogrammed from somatic cells, is a promising therapeutic option in personalized medicine for serious and incurable diseases such as AKI. The present study describes the therapeutic potential of induced nephron progenitor cell-sourced molecules (iNPC-SMs) as a cell-free strategy against cisplatin (CP)-induced nephrotoxicity, employing hyaluronic acid (HA) hydrogel-mediated local delivery to minimize systemic leakage and degradation. iNPC-SMs exhibited anti-apoptotic effects on HK-2 cells by inhibiting CP-induced ROS generation. Additionally, the localized biodistribution facilitated by hydrogel-mediated iNPC-SM delivery contributed to enhanced renal function, anti-inflammatory response, and renal regeneration in AKI mice. This study could serve as a 'proof of concept' for injectable hydrogel-mediated iNPC-SM delivery in AKI and as a model for further exploration of the development of cell-free regenerative medicine strategies.

Going with the flow: New insights regarding flow induced K+ secretion in the distal nephron.

K+ secretion in the distal nephron has a critical role in K+ homeostasis and is the primary route by which K+ is lost from the body. Renal K+ secretion is enhanced by increases in dietary K+ intake and by increases in tubular flow rate in the distal nephron. This review addresses new and important insights regarding the mechanisms underlying flow-induced K+ secretion (FIKS). While basal K+ secretion in the distal nephron is mediated by renal outer medullary K+ (ROMK) channels in principal cells (PCs), FIKS is mediated by large conductance, Ca2+/stretch activated K+ (BK) channels in intercalated cells (ICs), a distinct cell type. BK channel activation requires an increase in intracellular Ca2+ concentration ([Ca2+]i), and both PCs and ICs exhibit increases in [Ca2+]i in response to increases in tubular fluid flow rate, associated with an increase in tubular diameter. PIEZO1, a mechanosensitive, nonselective cation channel, is expressed in the basolateral membranes of PCs and ICs, where it functions as a mechanosensor. The loss of flow-induced [Ca2+]i transients in ICs and BK channel-mediated FIKS in microperfused collecting ducts isolated from mice with IC-specific deletion of Piezo1 in the CCD underscores the importance of PIEZO1 in the renal regulation of K+ transport.

A Case of Primary Ewing Sarcoma of the Kidney: Robotic-Assisted Nephron-Sparing Surgery, a Feasible Alternative in Treatment of Localized Disease.

Extra-skeletal Ewing sarcoma (EWS) occurs in about 12% of EWS patients; at the same time, primary involvement of the kidneys remains extremely rare. Since it was first described in 1975, only a small case series have been reported worldwide. About 95% of surgically treated patients with EWS of the kidney described in the literature underwent nephrectomy, and the remaining patients only had a tumor biopsy. Nephron-sparing surgery (NSS) has not been sufficiently investigated as an alternative in the local surgical treatment of localized disease, mostly as a result of technically unfeasible provisions of negative surgical margins. In this report, we present a unique case of primary EWS of the kidney with an asymptomatic course without radiographic signs that suggest a highly aggressive disease, successfully locally treated with robotic-assisted NSS. This report showcases that robotic-assisted NSS could be a feasible alternative in treatment of localized disease yielding equally good oncological results while, at the same time, creating better prerequisites for necessary adjuvant chemotherapy.

Measurement of adhesion and traction of cells at high yield reveals an energetic ratchet operating during nephron condensation.

Developmental biology-inspired strategies for tissue-building have extraordinary promise for regenerative medicine, spurring interest in the relationship between cell biophysical properties and morphological transitions. However, mapping gene or protein expression data to cell biophysical properties to physical morphogenesis remains challenging with current techniques. Here, we present multiplexed adhesion and traction of cells at high yield (MATCHY). MATCHY advances the multiplexing and throughput capabilities of existing traction force and cell-cell adhesion assays using microfabrication and a semiautomated computation scheme with machine learning-driven cell segmentation. Both biophysical assays are coupled with serial downstream immunofluorescence to extract cell type/signaling state information. MATCHY is especially suited to complex primary tissue-, organoid-, or biopsy-derived cell mixtures since it does not rely on a priori knowledge of cell surface markers, cell sorting, or use of lineage-specific reporter animals. We first validate MATCHY on canine kidney epithelial cells engineered for rearranged during transfection (RET) tyrosine kinase expression and quantify a relationship between downstream signaling and cell traction. We then use MATCHY to create a biophysical atlas of mouse embryonic kidney primary cells and identify distinct biophysical states along the nephron differentiation trajectory. Our data complement expression-level knowledge of adhesion molecule changes that accompany nephron differentiation with quantitative biophysical information. These data reveal an "energetic ratchet" that accounts for spatial trends in nephron progenitor cell condensation as they differentiate into early nephron structures, which we validate through agent-based computational simulation. MATCHY offers semiautomated cell biophysical characterization at >10,000-cell throughput, an advance benefiting fundamental studies and new synthetic tissue strategies for regenerative medicine.

Dose-dependent responses to canonical Wnt transcriptional complexes in the regulation of mammalian nephron progenitors.

In vivo and in vitro studies argue that concentration-dependent Wnt signaling regulates mammalian nephron progenitor cell (NPC) programs. Canonical Wnt signaling is regulated through the stabilization of ß-catenin, a transcriptional co-activator when complexed with Lef/Tcf DNA-binding partners. Using the GSK3ß inhibitor CHIR99021 (CHIR) to block GSK3ß-dependent destruction of ß-catenin, we examined dose-dependent responses to ß-catenin in mouse NPCs, using mRNA transduction to modify gene expression. Low CHIR-dependent proliferation of NPCs was blocked on ß-catenin removal, with evidence of NPCs arresting at the G2-M transition. While NPC identity was maintained following ß-catenin removal, mRNA-seq identified low CHIR and ß-catenin dependent genes. High CHIR activated nephrogenesis. Nephrogenic programming was dependent on Lef/Tcf factors and ß-catenin transcriptional activity. Molecular and cellular features of early nephrogenesis were driven in the absence of CHIR by a mutated stabilized form of ß-catenin. Chromatin association studies indicate low and high CHIR response genes are likely direct targets of canonical Wnt transcriptional complexes. Together, these studies provide evidence for concentration-dependent Wnt signaling in the regulation of NPCs and provide new insight into Wnt targets initiating mammalian nephrogenesis.

Practical Approach to Congenital Anomalies of the Kidneys: Focus on Anomalies With Insufficient or Abnormal Nephron Development: Renal Dysplasia, Renal Hypoplasia, and Renal Tubular Dysgenesis.

Congenital anomalies of the kidney and urinary tract (CAKUT) accounts for up to 30% of antenatal congenital anomalies and is the main cause of kidney failure in children worldwide. This review focuses on practical approaches to CAKUT, particularly those with insufficient or abnormal nephron development, such as renal dysplasia, renal hypoplasia, and renal tubular dysgenesis. The review provides insights into the histological features, pathogenesis, mechanisms, etiologies, antenatal and postnatal presentation, management, and prognosis of these anomalies. Differential diagnoses are discussed as several syndromes may include CAKUT as a phenotypic component and renal dysplasia may occur in some ciliopathies, tumor predisposition syndromes, and inborn errors of metabolism. Diagnosis and genetic counseling for CAKUT are challenging, due to the extensive variability in presentation, genetic and phenotypic heterogeneity, and difficulties to assess postnatal lung and renal function on prenatal imaging. The review highlights the importance of perinatal autopsy and pathological findings in surgical specimens to establish the diagnosis and prognosis of CAKUT. The indications and the type of genetic testing are discussed. The aim is to provide essential insights into the practical approaches, diagnostic processes, and genetic considerations offering valuable guidance for pediatric and perinatal pathologists.

Evolving Approach in Nephron-Sparing Surgery: Has Anything Changed from Open Surgery to Laparoscopy?

OBJECTIVE: This study aimed to provide valuable insights into the comparative efficacy of different surgical approaches for nephron-sparing surgery (NSS) and contribute to the existing literature in this field. MATERIALS AND METHODS: This study included patients who underwent NSS for small renal masses between January 2016 and March 2024. A total of 97 patients (41 in the open approach group, 56 in the laparoscopic approach group) with demographic, radiological, intraoperative, renal functional, and oncological follow-up data were included. Three different anatomical scoring systems (R.E.N.A.L. nephrometry score, PADUA score and C-index) were utilised to assess tumour location and estimate proximity to the hilum and collecting system. RESULTS: In the open nephron-sparing surgery (ONSS) and laparoscopic nephron-sparing surgery (LNSS) groups, the mean kidney tumour diameters (SD) were 5.20 ± 2.30 and 4.90 ± 2.10, which were similar in both surgical method groups (p = 0.061). However, tumours treated with ONSS had significantly more adverse morphometric features (p < 0.05). For ONSS and LNSS groups, the mean R.E.N.A.L. nephrometry scores (SD) were 6.15 ± 2.04 and 5.2 ± 1.4 (p = 0.032), respectively; The mean PADUA scores (SD) were 7.46 ± 1.14 and 6.8 ± 1.0 (p = 0.049), respectively; And the mean C-index (SD) scores were 1.39 ± 0.4 and 1.37 ± 0.5 (p = 0.062), respectively. No significant differences were found in the mean tumour diameter (cm) (Inter Quantile Range (IQR)) distribution of both groups (p = 0.058). Despite the slight increase in transfusion rate in the LNSS group, estimated blood loss (EBL), transfusion rates, and length of hospital stay were similar in both groups. CONCLUSIONS: Although LNSS does not appear superior in terms of intraoperative blood loss, length of hospital stay and transfusion rate, it provides comparable long-term outcomes to ONSS. Our study suggests that when matched with nephrometry scores, LNSS can achieve similar outcomes to ONSS.

[Application value of domestic single-port robot in nephron sparing surgery].

Objective: To explore the application value of the domestic precision ®single-port robotic system in nephron sparing surgery. Methods: The clinical data of patients with renal masses underwent nephron sparing surgery using the domestic precision ®single-port robotic system at the PLA General Hospital, Gulou Hospital Affiliated to Nanjing University School of Medicine, Zhongnan Hospital of Wuhan University and the First Affiliated Hospital of Nanchang University from September to November 2023 were retrospectively included. Perioperative clinical data, pathological examination results, and postoperative complications were summarized. Results: A total of 12 patients were included, including 8 males and 4 females, with 26-75 (56±16) years. Body mass index (BMI) was (25.1±2.7) kg/m2. There were 6 cases on the left side and 6 case on the right side. The surgical approach was transabdominal in 9 cases and retroperitoneal in 3 case. The maximum diameter of the lesions was (2.7±0.7) cm, the warm ischemia time [M (Q1, Q3)] was 19 (15, 26) minutes, the surgical time was 180 (149, 216) minutes, and the intraoperative blood loss was 50 (28, 100) ml. Postoperative visual analogue scale (VAS) was (2.9±1.5) points. Postoperative pathology revealed malignant renal clear cell carcinoma in 9 cases, with nuclear grading of 3 cases for Grade 1, 3 cases for Grade 2, and 3 cases for Grade 3. Eight cases of pathological TNM staging were pT1aN0M0 and 1 case was pT3aN0M0, with no cancer at the resection margin. Three cases showed benign renal vascular smooth muscle lipoma. There were no postoperative blood transfusions and no complications such as fever, urine leakage and poor wound healing. Conclusion: The prliminary experience reveals that the domestic precision ®single-port laparoscopic robotic system has good clinical application value in urological nephron sparing surgery.

Cadherin adhesion complexes direct cell aggregation in the epithelial transition of Wnt-induced nephron progenitor cells.

In the developing mammalian kidney, nephron formation is initiated by a subset of nephron progenitor cells (NPCs). Wnt input activates a ß-catenin (Ctnnb1)-driven, transcriptional nephrogenic program and the mesenchymal to epithelial transition (MET) of NPCs. Using an in vitro mouse NPC culture model, we observed that activation of the Wnt pathway results in the aggregation of induced NPCs, which is an initiating step in the MET program. Genetic removal showed aggregation was dependent on ß-catenin. Modulating extracellular Ca2+ levels showed cell-cell contacts were Ca2+ dependent, suggesting a role for cadherin (Cdh)-directed cell adhesion. Molecular analysis identified Cdh2, Cdh4 and Cdh11 in NPCs, and the ß-catenin directed upregulation of Cdh3 and Cdh4 accompanying the MET of induced NPCs. Mutational analysis of ß-catenin supported a role for a Lef/Tcf-ß-catenin-mediated transcriptional response in the cell aggregation process. Genetic removal of all four cadherins, and independent removal of α-catenin or of ß-catenin-α-catenin interactions, abolished aggregation, but not the inductive response to Wnt pathway activation. These findings, and data in an accompanying article highlight the role of ß-catenin in linking transcriptional programs to the morphogenesis of NPCs in mammalian nephrogenesis.

Identification of countercurrent tubule-vessel arrangements in the early development of mouse kidney based on immunohistochemistry and computer-assisted 3D visualization.

Nephron loop-vessel countercurrent arrangement in the medulla provides the structural basis for the formation of concentrated urine. To date, the morphogenesis of it and relevant water and solutes transportation has not been fully elucidated. In this study, with immunohistochemistry for aquaporins (AQP) and Na-K-2Cl co-transporter (NKCC2), as well as 3D visualization, we noticed in embryonic day 14.5 kidneys that the countercurrent arrangement of two pairs of loop-vessel was established as soon as the loop and vessel both extended into the medulla. One pair happened between descending limb and ascending vasa recta, the other occurred between thick ascending limb and descending vasa recta. Meanwhile, the immunohistochemical results showed that the limb and vessel expressing AQP-1 such as descending thick and thin limb and descending vasa recta was always accompanied with AQP-1 negative ascending vasa recta or capillaries and thick ascending limb, respectively. Moreover, the thick ascending limb expressing NKCC2 closely contacted with descending vasa recta without expressing NKCC2. As kidney developed, an increasing number of loop-vessels in countercurrent arrangement extended into the interstitium of the medulla. In addition, we observed that the AQP-2 positive ureteric bud and their branches were separated from those pairs of tubule-vessels by a relatively large and thin-walled veins or capillaries. Thus, the present study reveals that the loop-vessel countercurrent arrangement is formed at the early stage of nephrogenesis, which facilitates the efficient transportation of water and electrolytes to maintain the medullary osmolality and to form a concentrated urine.

Nephron specific ATP6AP2 knockout increases urinary excretion of fatty acids and decreases renal cortical megalin expression.

ATP6AP2 knockout in the renal nephron impairs receptor-mediated endocytosis, increasing urinary albumin and glucose excretion and impairing weight gain. Nonesterified fatty acids (NEFA) in urine are bound to albumin and reabsorbed in the proximal tubule through receptor-mediated endocytosis by the megalin-cubilin complex. We hypothesized that ATP6AP2 knockout increases urinary NEFA excretion through a reduction in megalin. Ten-week-old male C57BL/6 mice with nephron specific inducible ATP6AP2 knockout and noninduced controls were fed either normal diet (ND 12% fat) or high fat diet (HFD 45% fat) for 6 months. ATP6AP2 knockout significantly increased urine albumin:creatinine ratio in both ND and HFD fed mice while normalized urine NEFA concentration increased 489% and 259% in ND and HFD knockout mice compared to respective controls. Knockout decreased renal cortical megalin mRNA by 47% on ND and 49% on HFD while megalin protein expression decreased by 36% and 44% respectively. At the same time, markers of mTOR activity were increased while autophagy was impaired. Our results indicate that nephron specific ATP6AP2 knockout increases urinary NEFA excretion in the setting of impaired receptor-mediated endocytosis. Further investigation should determine whether ATP6AP2 contributes to obesity related ectopic lipid deposition in the proximal tubule.

Microplastics exposure disrupts nephrogenesis and induces renal toxicity in human iPSC-derived kidney organoids.

Microplastics (MPs) have emerged as a pervasive environmental pollutant of global concern. Their detection within the human placenta and fetal organs has prompted apprehension regarding the potential hazards of MPs during early organogenesis. The kidney, a vital multifunctional organ, is susceptible to damage from MPs in adulthood. However, the precise adverse effects of MP exposure on human nephrogenesis remain ambiguous due to the absence of a suitable model. Here, we explore the potential impact of MPs on early kidney development utilizing human kidney organoids in vitro. Human kidney organoids were subjected to polystyrene-MPs (PS-MPs, 1 µm) during the nephron progenitor cell (NPC) stage, a critical phase in early kidney development and patterning. We delineate the effects of PS-MPs on various stages of nephrogenesis, including NPC, renal vesicle, and comma-shaped body, through sequential examination of kidney organoids. PS-MPs were observed to adhere to the surface of cells during the NPC stage and accumulate within glomerulus-like structures within kidney organoids. Moreover, both short- and long-term exposure to PS-MPs resulted in diminished organoid size and aberrant nephron structure. PS-MP exposure heightened reactive oxygen species (ROS) production, leading to NPC apoptosis during early kidney development. Increased apoptosis, diminished cell viability, and NPC reduction likely contribute to the observed organoid size reduction under PS-MP treatment. Transcriptomic analysis at both NPC and endpoint stages revealed downregulation of Notch signaling, resulting in compromised proximal and distal tubular structures, thereby disrupting normal nephron patterning following PS-MP exposure. Our findings highlight the significant disruptive impact of PS-MPs on human kidney development, offering new insights into the mechanisms underlying PS-MP-induced nephron toxicity.

Recurrences after nephron-sparing treatments of renal cell carcinoma: a competing risk analysis.

PURPOSE: To examine associations between ablative therapy (AT) and partial nephrectomy (PN) and the occurrence of local recurrence (LR), distant metastatic recurrence (DMR) and all-cause mortality in a nation-wide real-world population-based cohort of patients with nonmetastatic renal cell carcinoma (nmRCC). METHODS: Data on 2751 AT- or PN-treated nmRCC tumours diagnosed during 2005-2018, representing 2701 unique patients, were obtained from the National Swedish Kidney Cancer Register. Time to LR/DMR or death with/without LR/DMR was analysed using Cox regression models. RESULTS: During a mean of 4.8 years follow-up, LR was observed for 111 (4.0%) tumours, DMR for 108 (3.9%) tumours, and death without LR/DMR for 206 (7.5%) tumours. AT-treated tumours had a 4.31 times higher risk of LR (P < 0.001) and a 1.91 times higher risk of DMR (P = 0.018) than PN-treated, with no significant differences in risk of death without LR/DMR. During a mean of 3.2 and 2.5 years of follow-up after LR/DMR, respectively, 24 (21.6%) of the LR cases and 56 (51.9%) of the DMR cases died, compared to 7.5% in patients without LR/DMR. There were no significant differences between AT- and PN-treated regarding risks of early death after occurrence of LR or DMR. CONCLUSION: AT treatment of patients with nmRCC implied significantly higher risks of LR and DMR compared with PN treatment. To minimize the risks of LR and DMR, these results suggest that PN is preferred over AT as primary treatment, supporting the EAU guidelines to recommended AT mainly to frail and/or comorbid patients.

Nephron-Specific Lin28A Overexpression Triggers Severe Inflammatory Response and Kidney Damage.

The RNA-binding proteins LIN28A and LIN28B contribute to a variety of developmental biological processes. Dysregulation of Lin28A and Lin28B expression is associated with numerous types of tumors. This study demonstrates that Lin28A overexpression in the mouse nephrons leads to severe inflammation and kidney damage rather than to tumorigenesis. Notably, Lin28A overexpression causes inflammation only when expressed in nephrons, but not in the stromal cells of the kidneys, highlighting its cell context-dependent nature. The nephron-specific Lin28A-induced inflammatory response differs from previously described Lin28B-mediated inflammatory feedback loops as it is IL-6 independent. Instead, it is associated with the rapid upregulation of cytokines like Cxcl1 and Ccl2. These findings suggest that the pathophysiological effects of Lin28A overexpression extend beyond cell transformation. Our transgenic mouse model offers a valuable tool for advancing our understanding of the pathophysiology of acute kidney injury, where inflammation is a key factor.

Highly parallel production of designer organoids by mosaic patterning of progenitors.

Organoids derived from human stem cells are a promising approach for disease modeling, regenerative medicine, and fundamental research. However, organoid variability and limited control over morphological outcomes remain as challenges. One open question is the extent to which engineering control over culture conditions can guide organoids to specific compositions. Here, we extend a DNA "velcro" cell patterning approach, precisely controlling the number and ratio of human induced pluripotent stem cell-derived progenitors contributing to nephron progenitor (NP) organoids and mosaic NP/ureteric bud (UB) tip cell organoids within arrays of microwells. We demonstrate long-term control over organoid size and morphology, decoupled from geometric constraints. We then show emergent trends in organoid tissue proportions that depend on initial progenitor cell composition. These include higher nephron and stromal cell representation in mosaic NP/UB organoids vs. NP-only organoids and a "goldilocks" initial cell ratio in mosaic organoids that optimizes the formation of proximal tubule structures.

Single-cell multiomics reveals ENL mutation perturbs kidney developmental trajectory by rewiring gene regulatory landscape.

How disruptions to normal cell differentiation link to tumorigenesis remains incompletely understood. Wilms tumor, an embryonal tumor associated with disrupted organogenesis, often harbors mutations in epigenetic regulators, but their role in kidney development remains unexplored. Here, we show at single-cell resolution that a Wilms tumor-associated mutation in the histone acetylation reader ENL disrupts kidney differentiation in mice by rewiring the gene regulatory landscape. Mutant ENL promotes nephron progenitor commitment while restricting their differentiation by dysregulating transcription factors such as Hox clusters. It also induces abnormal progenitors that lose kidney-associated chromatin identity. Furthermore, mutant ENL alters the transcriptome and chromatin accessibility of stromal progenitors, resulting in hyperactivation of Wnt signaling. The impacts of mutant ENL on both nephron and stroma lineages lead to profound kidney developmental defects and postnatal mortality in mice. Notably, a small molecule inhibiting mutant ENL's histone acetylation binding activity largely reverses these defects. This study provides insights into how mutations in epigenetic regulators disrupt kidney development and suggests a potential therapeutic approach.

Regulating distal nephron functions and salt sensitivity.

This review highlights the molecular basis of salt sensitivity in hypertension, with a focus on the regulation of sodium transport in the distal nephron. Sodium reabsorption in this region is often linked to the actions of aldosterone, although in recent years numerous findings have been reported on the aldosterone-independent pathway of acquiring salt sensitivity by potassium deficiency or potassium loading. The key to this discussion is the interplay, through extracellular potassium concentration, between the first part of the tubules expressing the Na+-Cl- cotransporter (NCC) and the second part expressing the epithelial Na+ channel (ENaC). The molecular pathways such as with-no-lysine 1 (WNK)-STE20/SPS1-related proline-alanine-rich kinase (SPAK)/oxidative stress-responsive kinase 1 (OSR1) signaling, Kelch-like family member 3 (KLHL3)-cullin 3 (CUL3) complex, protein phosphatases, and mechanistic target of rapamycin complex 2 (mTORC2)-Nedd4L pathway are described as the mechanism by which salt sensitivity on blood pressure is acquired in response to changes in physiological conditions including potassium depletion or loading. This review highlights the potential for targeting these molecular pathways to develop novel therapeutic strategies for the treatment of salt-sensitive hypertension, the mechanism of which remains to be elucidated.