Polyploid tubular cells initiate a TGF-ß1 controlled loop that sustains polyploidization and fibrosis after acute kidney injury.

Polyploidization of tubular cells (TC) is triggered by acute kidney injury (AKI) to allow survival in the early phase after AKI, but in the long run promotes fibrosis and AKI-chronic kidney disease (CKD) transition. The molecular mechanism governing the link between polyploid TC and kidney fibrosis remains to be clarified. In this study, we demonstrate that immediately after AKI, expression of cell cycle markers mostly identifies a population of DNA-damaged polyploid TC. Using transgenic mouse models and single-cell RNA sequencing we show that, unlike diploid TC, polyploid TC accumulate DNA damage and survive, eventually resting in the G1 phase of the cell cycle. In vivo and in vitro single-cell RNA sequencing along with sorting of polyploid TC shows that these cells acquire a profibrotic phenotype culminating in transforming growth factor (TGF)-ß1 expression and that TGF-ß1 directly promotes polyploidization. This demonstrates that TC polyploidization is a self-sustained mechanism. Interactome analysis by single-cell RNA sequencing revealed that TGF-ß1 signaling fosters a reciprocal activation loop among polyploid TC, macrophages, and fibroblasts to sustain kidney fibrosis and promote CKD progression. Collectively, this study contributes to the ongoing revision of the paradigm of kidney tubule response to AKI, supporting the existence of a tubulointerstitial cross talk mediated by TGF-ß1 signaling produced by polyploid TC following DNA damage.NEW & NOTEWORTHY Polyploidization in tubular epithelial cells has been neglected until recently. Here, we showed that polyploidization is a self-sustained mechanism that plays an important role during chronic kidney disease development, proving the existence of a cross talk between infiltrating cells and polyploid tubular cells. This study contributes to the ongoing revision of kidney adaptation to injury, posing polyploid tubular cells at the center of the process.

Doubts and concerns about COVID-19 uncertainties on imaging data, clinical score, and outcomes.

BACKGROUND: COVID-19 is a pandemic disease affecting predominantly the respiratory apparatus with clinical manifestations ranging from asymptomatic to respiratory failure. Chest CT is a crucial tool in diagnosing and evaluating the severity of pulmonary involvement through dedicated scoring systems. Nonetheless, many questions regarding the relationship of radiologic and clinical features of the disease have emerged in multidisciplinary meetings. The aim of this retrospective study was to explore such relationship throughout an innovative and alternative approach. MATERIALS AND METHODS: This study included 550 patients (range 25-98 years; 354 males, mean age 66.1; 196 females, mean age 70.9) hospitalized for COVID-19 with available radiological and clinical data between 1 March 2021 and 30 April 2022. Radiological data included CO-RADS, chest CT score, dominant pattern, and typical/atypical findings detected on CT examinations. Clinical data included clinical score and outcome. The relationship between such features was investigated through the development of the main four frequently asked questions summarizing the many issues arisen in multidisciplinary meetings, as follows 1) CO-RADS, chest CT score, clinical score, and outcomes; 2) the involvement of a specific lung lobe and outcomes; 3) dominant pattern/distribution and severity score for the same chest CT score; 4) additional factors and outcomes. RESULTS: 1) If CT was suggestive for COVID, a strong correlation between CT/clinical score and prognosis was found; 2) Middle lobe CT involvement was an unfavorable prognostic criterion; 3) If CT score < 50%, the pattern was not influential, whereas if CT score > 50%, crazy paving as dominant pattern leaded to a 15% increased death rate, stacked up against other patterns, thus almost doubling it; 4) Additional factors usually did not matter, but lymph-nodes and pleural effusion worsened prognosis. CONCLUSIONS: This study outlined those radiological features of COVID-19 most relevant towards disease severity and outcome with an innovative approach.

Role of Sex Hormones in Prevalent Kidney Diseases.

Chronic kidney disease (CKD) is a constantly growing global health burden, with more than 840 million people affected worldwide. CKD presents sex disparities in the pathophysiology of the disease, as well as in the epidemiology, clinical manifestations, and disease progression. Overall, while CKD is more frequent in females, males have a higher risk to progress to end-stage kidney disease. In recent years, numerous studies have highlighted the role of sex hormones in the health and diseases of several organs, including the kidney. In this review, we present a clinical overview of the sex-differences in CKD and a selection of prominent kidney diseases causing CKD: lupus nephritis, diabetic kidney disease, IgA nephropathy, and autosomal dominant polycystic kidney disease. We report clinical and experimental findings on the role of sex hormones in the development of the disease and its progression to end-stage kidney disease.

SGLT2 inhibition requires reconsideration of fundamental paradigms in chronic kidney disease, 'diabetic nephropathy', IgA nephropathy and podocytopathies with FSGS lesions.

In 2020, the Dapagliflozin and Prevention of Adverse Outcomes in Chronic Kidney Disease (DAPA-CKD) trial first demonstrated that inhibition of the sodium-glucose transporter-2 (SGLT2) with dapagliflozin attenuates the progression of chronic kidney disease (CKD) with proteinuria in patients with or without diabetes at an unprecedented effect size. These results have far-reaching implications for a series of traditional concepts in Nephrology. It now became obvious that CKD with and without diabetes involves a predominant SGLT2-driven pathophysiology compared with the other pathogenic pathways currently under consideration. As SGLT2 inhibition is similarly efficacious in diabetic and non-diabetic CKD with proteinuria, treating CKD rather than 'diabetic nephropathy' becomes the central paradigm. Indeed, in older adults with type 2 diabetes, CKD is rather of multifactorial origin. As the DAPA-CKD trial included more patients with immunoglobulin A nephropathy (IgAN) than any of the previous IgAN trials, dual renin-angiotensin/SGLT2 inhibition may become the new standard. The same applies for patients with podocytopathy-related focal segmental glomerulosclerosis lesions. From now on, IgAN and podocytopathy trials without SGLT2 inhibition as background therapy and without glomerular filtration rate decline as primary outcome criterion will be of limited value. These and other potential implications will trigger broad discussions and secondary research activities with conclusions difficult to predict today. However, one is for sure: Nephrology after the DAPA-CKD trial will be not the same as it was before. Finally!

From kidney injury to kidney cancer.

Epidemiologic studies document strong associations between acute or chronic kidney injury and kidney tumors. However, whether these associations are linked by causation, and in which direction, is unclear. Accumulating data from basic and clinical research now shed light on this issue and prompt us to propose a new pathophysiological concept with immanent implications in the management of patients with kidney disease and patients with kidney tumors. As a central paradigm, this review proposes the mechanisms of kidney damage and repair that are active during acute kidney injury but also during persistent injuries in chronic kidney disease as triggers of DNA damage, promoting the expansion of (pre-)malignant cell clones. As renal progenitors have been identified by different studies as the cell of origin for several benign and malignant kidney tumors, we discuss how the different types of kidney tumors relate to renal progenitors at specific sites of injury and to germline or somatic mutations in distinct signaling pathways. We explain how known risk factors for kidney cancer rather represent risk factors for kidney injury as an upstream cause of cancer. Finally, we propose a new role for nephrologists in kidney cancer (i.e., the primary and secondary prevention and treatment of kidney injury to reduce incidence, prevalence, and recurrence of kidney cancer).

Edema-like marrow signal intensity: a narrative review with a pictorial essay.

The term edema-like marrow signal intensity (ELMSI) represents a general term describing an area of abnormal signal intensity at MRI. Its appearance includes absence of clear margins and the possibility of exceeding well-defined anatomical borders (for example, physeal scars). We can define "ELMSI with unknown cause" an entity where the characteristic MR appearance is associated with the absence of specific signs of an underlying condition. However, it is more often an important finding indicating the presence of an underlying disease, and we describe this case as "ELMSI with known cause." It presents a dynamic behavior and its evolution can largely vary. It initially corresponds to an acute inflammatory response with edema, before being variably replaced by more permanent marrow remodeling changes such as fibrosis or myxomatous connective tissue that can occur over time. It is important to study ELMSI variations over time in order to evaluate the activity state and therapeutic response of an inflammatory chronic joint disease, the resolution of a trauma, and the severity of an osteoarthritis. We propose a narrative review of the literature dealing with various subjects about this challenging topic that is imaging, temporal evolution, etiology, differential diagnoses, and possible organization, together with a pictorial essay.

Telomerase activated thymidine analogue pro-drug is a new molecule targeting hepatocellular carcinoma.

BACKGROUND & AIMS: Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. Although hepatectomy and transplantation have significantly improved survival, there is no effective chemotherapeutic treatment for HCC and its prognosis remains poor. Sustained activation of telomerase is essential for the growth and progression of HCC, suggesting that telomerase is a rational target for HCC therapy. Therefore, we developed a thymidine analogue pro-drug, acycloguanosyl-5'-thymidyltriphosphate (ACV-TP-T), which is specifically activated by telomerase in HCC cells and investigated its anti-tumour efficacy. METHODS: First, we verified in vitro whether ACV-TP-T was a telomerase substrate. Second, we evaluated proliferation and apoptosis in murine (Hepa1-6) and human (Hep3B, HuH7, HepG2) hepatic cancer cells treated with ACV-TP-T. Next, we tested the in vivo treatment efficacy in HBV transgenic mice that spontaneously develop hepatic tumours, and in a syngeneic orthotopic murine model where HCC cells were implanted directly in the liver. RESULTS: In vitro characterization provided direct evidence that the pro-drug was actively metabolized in liver cancer cells by telomerase to release the active form of acyclovir. Alterations in cell cycle and apoptosis were observed following in vitro treatment with ACV-TP-T. In the transgenic and orthotopic mouse models, treatment with ACV-TP-T reduced tumour growth, increased apoptosis, and reduced the proliferation of tumour cells. CONCLUSIONS: ACV-TP-T is activated by telomerase in HCC cells and releases active acyclovir that reduces proliferation and induces apoptosis in human and murine liver cancer cells. This pro-drug holds a great promise for the treatment of HCC.

Modeled microgravity unravels the roles of mechanical forces in renal progenitor cell physiology.

BACKGROUND: The glomerulus is a highly complex system, composed of different interdependent cell types that are subjected to various mechanical stimuli. These stimuli regulate multiple cellular functions, and changes in these functions may contribute to tissue damage and disease progression. To date, our understanding of the mechanobiology of glomerular cells is limited, with most research focused on the adaptive response of podocytes. However, it is crucial to recognize the interdependence between podocytes and parietal epithelial cells, in particular with the progenitor subset, as it plays a critical role in various manifestations of glomerular diseases. This highlights the necessity to implement the analysis of the effects of mechanical stress on renal progenitor cells. METHODS: Microgravity, modeled by Rotary Cell Culture System, has been employed as a system to investigate how renal progenitor cells respond to alterations in the mechanical cues within their microenvironment. Changes in cell phenotype, cytoskeleton organization, cell proliferation, cell adhesion and cell capacity for differentiation into podocytes were analyzed. RESULTS: In modeled microgravity conditions, renal progenitor cells showed altered cytoskeleton and focal adhesion organization associated with a reduction in cell proliferation, cell adhesion and spreading capacity. Moreover, mechanical forces appeared to be essential for renal progenitor differentiation into podocytes. Indeed, when renal progenitors were exposed to a differentiative agent in modeled microgravity conditions, it impaired the acquisition of a complex podocyte-like F-actin cytoskeleton and the expression of specific podocyte markers, such as nephrin and nestin. Importantly, the stabilization of the cytoskeleton with a calcineurin inhibitor, cyclosporine A, rescued the differentiation of renal progenitor cells into podocytes in modeled microgravity conditions. CONCLUSIONS: Alterations in the organization of the renal progenitor cytoskeleton due to unloading conditions negatively affect the regenerative capacity of these cells. These findings strengthen the concept that changes in mechanical cues can initiate a pathophysiological process in the glomerulus, not only altering podocyte actin cytoskeleton, but also extending the detrimental effect to the renal progenitor population. This underscores the significance of the cytoskeleton as a druggable target for kidney diseases.

Differentiation of crescent-forming kidney progenitor cells into podocytes attenuates severe glomerulonephritis in mice.

Crescentic glomerulonephritis is characterized by vascular necrosis and parietal epithelial cell hyperplasia in the space surrounding the glomerulus, resulting in the formation of crescents. Little is known about the molecular mechanisms driving this process. Inducing crescentic glomerulonephritis in two Pax2Cre reporter mouse models revealed that crescents derive from clonal expansion of single immature parietal epithelial cells. Preemptive and delayed histone deacetylase inhibition with panobinostat, a drug used to treat hematopoietic stem cell disorders, attenuated crescentic glomerulonephritis with recovery of kidney function in the two mouse models. Three-dimensional confocal microscopy and stimulated emission depletion superresolution imaging of mouse glomeruli showed that, in addition to exerting an anti-inflammatory and immunosuppressive effect, panobinostat induced differentiation of an immature hyperplastic parietal epithelial cell subset into podocytes, thereby restoring the glomerular filtration barrier. Single-cell RNA sequencing of human renal progenitor cells in vitro identified an immature stratifin-positive cell subset and revealed that expansion of this stratifin-expressing progenitor cell subset was associated with a poor outcome in human crescentic glomerulonephritis. Treatment of human parietal epithelial cells in vitro with panobinostat attenuated stratifin expression in renal progenitor cells, reduced their proliferation, and promoted their differentiation into podocytes. These results offer mechanistic insights into the formation of glomerular crescents and demonstrate that selective targeting of renal progenitor cells can attenuate crescent formation and the deterioration of kidney function in crescentic glomerulonephritis in mice.

Tubular cell polyploidy protects from lethal acute kidney injury but promotes consequent chronic kidney disease.

Acute kidney injury (AKI) is frequent, often fatal and, for lack of specific therapies, can leave survivors with chronic kidney disease (CKD). We characterize the distribution of tubular cells (TC) undergoing polyploidy along AKI by DNA content analysis and single cell RNA-sequencing. Furthermore, we study the functional roles of polyploidization using transgenic models and drug interventions. We identify YAP1-driven TC polyploidization outside the site of injury as a rapid way to sustain residual kidney function early during AKI. This survival mechanism comes at the cost of senescence of polyploid TC promoting interstitial fibrosis and CKD in AKI survivors. However, targeting TC polyploidization after the early AKI phase can prevent AKI-CKD transition without influencing AKI lethality. Senolytic treatment prevents CKD by blocking repeated TC polyploidization cycles. These results revise the current pathophysiological concept of how the kidney responds to acute injury and identify a novel druggable target to improve prognosis in AKI survivors.

Molecular Mechanisms of Renal Progenitor Regulation: How Many Pieces in the Puzzle?

Kidneys of mice, rats and humans possess progenitors that maintain daily homeostasis and take part in endogenous regenerative processes following injury, owing to their capacity to proliferate and differentiate. In the glomerular and tubular compartments of the nephron, consistent studies demonstrated that well-characterized, distinct populations of progenitor cells, localized in the parietal epithelium of Bowman capsule and scattered in the proximal and distal tubules, could generate segment-specific cells in physiological conditions and following tissue injury. However, defective or abnormal regenerative responses of these progenitors can contribute to pathologic conditions. The molecular characteristics of renal progenitors have been extensively studied, revealing that numerous classical and evolutionarily conserved pathways, such as Notch or Wnt/ß-catenin, play a major role in cell regulation. Others, such as retinoic acid, renin-angiotensin-aldosterone system, TLR2 (Toll-like receptor 2) and leptin, are also important in this process. In this review, we summarize the plethora of molecular mechanisms directing renal progenitor responses during homeostasis and following kidney injury. Finally, we will explore how single-cell RNA sequencing could bring the characterization of renal progenitors to the next level, while knowing their molecular signature is gaining relevance in the clinic.

Magnetic resonance imaging of salivary gland tumours: Key findings for imaging characterisation.

Salivary gland tumours are rare, representing only 3% of all head and neck neoplasms, with the parotid gland being the most common site (80 %). The risk of malignancy is inversely proportional to the size of the gland: lesions arising in the sublingual or minor salivary glands are more likely to be malignant, whereas parotid gland neoplasms are mostly benign. Fine needle aspiration cytology and core needle biopsy are considered the most accurate modalities for the diagnosis of a salivary gland neoplasm; however, they are not always conclusive due to procedural sampling errors and for the presence of a cytological / histological overlap between benign and malignant tumours. Moreover, they cannot be easily performed for parotid deep portion localisation. The role of magnetic resonance imaging (MRI) is growing and advanced techniques (diffusion-weighted and dynamic contrast-enhanced perfusion-weighted imaging) can provide useful additional information for the assessment of salivary gland neoplasms. The aim of this review is to present the main MRI and clinical features of salivary gland tumours to improve their comprehensive evaluation and characterisation.

Sex and Gender Differences in Kidney Cancer: Clinical and Experimental Evidence.

Sex and gender disparities have been reported for different types of non-reproductive cancers. Males are two times more likely to develop kidney cancer than females and have a higher death rate. These differences can be explained by looking at genetics and genomics, as well as other risk factors such as hypertension and obesity, lifestyle, and female sex hormones. Examination of the hormonal signaling pathways bring further insights into sex-related differences. Sex and gender-based disparities can be observed at the diagnostic, histological and treatment levels, leading to significant outcome difference. This review summarizes the current knowledge about sex and gender-related differences in the clinical presentation of patients with kidney cancer and the possible biological mechanisms that could explain these observations. Underlying sex-based differences may contribute to the development of sex-specific prognostic and diagnostic tools and the improvement of personalized therapies.

Bioengineering strategies for nephrologists: kidney was not built in a day.

Introduction: The number of patients with end-stage kidney disease is increasing worldwide, creating an unprecedented organ shortage. The kidney is a highly complex structure performing many crucial functions. Dialysis replaces filtration but not all other kidney functions and transplant is limited by kidney availability. Numerous innovative ways are being explored to obtain new kidneys for disease modeling and potentially replace lost kidney functions.Areas covered: In this review, we will go through the different approaches that have been developed over the years to build kidneys. We will first present the current advances in xenotransplantation and generation of interspecies chimeras. Next, we will examine the attempts to create bioengineered kidneys with hemodialysis-derived implantable devices and decellularized organs. Finally, we will examine how organoids and microfluidic devices could answer important pathophysiological questions and model the path toward creating in vitro functional organs, for example through 3D bioprinting.Expert opinion: While all the aforementioned approaches to create new kidneys are promising, their translation into clinical practice seems a long way off, except xenotransplantation. Nonetheless, these novel technologies already consent disease modeling and drug testing at 3D level. We will review the stages of progress toward patient therapy and advantages/drawbacks of the various strategies.

Acute kidney injury promotes development of papillary renal cell adenoma and carcinoma from renal progenitor cells.

Acute tissue injury causes DNA damage and repair processes involving increased cell mitosis and polyploidization, leading to cell function alterations that may potentially drive cancer development. Here, we show that acute kidney injury (AKI) increased the risk for papillary renal cell carcinoma (pRCC) development and tumor relapse in humans as confirmed by data collected from several single-center and multicentric studies. Lineage tracing of tubular epithelial cells (TECs) after AKI induction and long-term follow-up in mice showed time-dependent onset of clonal papillary tumors in an adenoma-carcinoma sequence. Among AKI-related pathways, NOTCH1 overexpression in human pRCC associated with worse outcome and was specific for type 2 pRCC. Mice overexpressing NOTCH1 in TECs developed papillary adenomas and type 2 pRCCs, and AKI accelerated this process. Lineage tracing in mice identified single renal progenitors as the cell of origin of papillary tumors. Single-cell RNA sequencing showed that human renal progenitor transcriptome showed similarities to PT1, the putative cell of origin of human pRCC. Furthermore, NOTCH1 overexpression in cultured human renal progenitor cells induced tumor-like 3D growth. Thus, AKI can drive tumorigenesis from local tissue progenitor cells. In particular, we find that AKI promotes the development of pRCC from single progenitors through a classical adenoma-carcinoma sequence.

Substrate Stiffness Modulates Renal Progenitor Cell Properties via a ROCK-Mediated Mechanotransduction Mechanism.

Stem cell (SC)-based tissue engineering and regenerative medicine (RM) approaches may provide alternative therapeutic strategies for the rising number of patients suffering from chronic kidney disease. Embryonic SCs and inducible pluripotent SCs are the most frequently used cell types, but autologous patient-derived renal SCs, such as human CD133+CD24+ renal progenitor cells (RPCs), represent a preferable option. RPCs are of interest also for the RM approaches based on the pharmacological encouragement of in situ regeneration by endogenous SCs. An understanding of the biochemical and biophysical factors that influence RPC behavior is essential for improving their applicability. We investigated how the mechanical properties of the substrate modulate RPC behavior in vitro. We employed collagen I-coated hydrogels with variable stiffness to modulate the mechanical environment of RPCs and found that their morphology, proliferation, migration, and differentiation toward the podocyte lineage were highly dependent on mechanical stiffness. Indeed, a stiff matrix induced cell spreading and focal adhesion assembly trough a Rho kinase (ROCK)-mediated mechanism. Similarly, the proliferative and migratory capacity of RPCs increased as stiffness increased and ROCK inhibition, by either Y27632 or antisense LNA-GapmeRs, abolished these effects. The acquisition of podocyte markers was also modulated, in a narrow range, by the elastic modulus and involved ROCK activity. Our findings may aid in 1) the optimization of RPC culture conditions to favor cell expansion or to induce efficient differentiation with important implication for RPC bioprocessing, and in 2) understanding how alterations of the physical properties of the renal tissue associated with diseases could influenced the regenerative response of RPCs.

Renal Cancer Stem Cells: Characterization and Targeted Therapies.

Renal cell carcinoma (RCC) is a major neoplasm with high incidence in western countries. Tumors are heterogeneous and are composed of differentiated cancer cells, stromal cells, and cancer stem cells (CSCs). CSCs possess two main properties: self-renewal and proliferation. Additionally, they can generate new tumors once transplanted into immunodeficient mice. Several approaches have been described to identify them, through the expression of cell markers, functional assays, or a combination of both. As CSCs are involved in the resistance mechanisms to radio- and chemotherapies, several new strategies have been proposed to directly target CSCs in RCC. One approach drives CSCs to differentiate into cancer cells sensitive to conventional treatments, while the other proposes to eradicate them selectively. A series of innovative therapies aiming at eliminating CSCs have been designed to treat other types of cancer and have not been experimented with on RCC yet, but they reveal themselves to be promising. In conclusion, CSCs are an important player in carcinogenesis and represent a valid target for therapy in RCC patients.

Mesenchymal Stem Cell-Based Therapy for Kidney Disease: A Review of Clinical Evidence.

Mesenchymal stem cells form a population of self-renewing, multipotent cells that can be isolated from several tissues. Multiple preclinical studies have demonstrated that the administration of exogenous MSC could prevent renal injury and could promote renal recovery through a series of complex mechanisms, in particular via immunomodulation of the immune system and release of paracrine factors and microvesicles. Due to their therapeutic potentials, MSC are being evaluated as a possible player in treatment of human kidney disease, and an increasing number of clinical trials to assess the safety, feasibility, and efficacy of MSC-based therapy in various kidney diseases have been proposed. In the present review, we will summarize the current knowledge on MSC infusion to treat acute kidney injury, chronic kidney disease, diabetic nephropathy, focal segmental glomerulosclerosis, systemic lupus erythematosus, and kidney transplantation. The data obtained from these clinical trials will provide further insight into safety, feasibility, and efficacy of MSC-based therapy in renal pathologies and allow the design of consensus protocol for clinical purpose.

Retinoids and glomerular regeneration.

Retinoids are essential in the development and function of several organs, exerting potent effects on stem cell systems. All-trans retinoic acid, through binding to the retinoic acid response elements, alters transcription of numerous genes in stem cells, leading to an exit from the self-renewing state and promoting differentiation. In the kidney, retinoids protect against injury and ameliorate function in multiple experimental models of disease. Recent evidence suggests that retinoids act on renal progenitors by promoting their differentiation into mature podocytes and retinoic acid-induced podocyte differentiation is impaired by proteinuria because of sequestration of retinoic acid by albumin. However, retinoic acid administration can revert renal progenitor differentiation and promote podocyte regeneration. A more complete understanding of retinoid-dependent renal progenitor differentiation into podocytes should reward us with new insights into the mechanisms of progression toward glomerulosclerosis.