Identification of kidney injury released circulating osteopontin as causal agent of respiratory failure

The role of osteopontin in chronic kidney disease-mineral bone disorder

PURPOSE OF REVIEW

Chronic kidney disease-mineral bone disorder (CKD-MBD) is associated with several adverse outcomes, including bone fragility and sarcopenia. Identification of new agents mitigating systemic damage related to uremia is critical and needed to unveil pathways implicated in CKD-MBD.

RECENT FINDINGS

Osteopontin (OPN) is involved in different physiological and pathological processes and works as a bridge connecting several systems. It may serve as a biomarker for many diseases, including human cancers, neurodegenerative disorders and autoimmune diseases. OPN has been implicated in disturbances of bone mineralization and remodeling, and has an interplay with parathyroid hormone and FGF23 in experimental models. In patients with CKD and severe hyperparathyroidism, OPN expression in muscle tissue has been linked to worse functionality and local inflammation, which is partially reverted after parathyroidectomy.

SUMMARY

Future studies could confirm the role of OPN as a biomarker in nephrology. Greater understanding of its role in CKD-MBD will help us define a better therapeutic strategy in patients with CKD.

Protein Ubiquitination Modification in Pulmonary Fibrosis

Pulmonary fibrosis (PF) is a chronic, progressive fibrotic interstitial lung disease characterized by a high incidence and mortality rate, which encompasses features, such as diffuse alveolar inflammation, invasive fibroblast activation, and uncontrolled extracellular matrix (ECM) deposition. Beyond the local pathological processes, PF can be better understood in light of interorgan communication networks that are involved in its progression. Notably, pulmonary inflammation can affect cardiovascular, renal, hepatic, and neural functions, highlighting the importance of understanding these systemic interactions. Posttranslational modifications play a crucial role in regulating protein function, localization, stability, and activity. Specifically, protein ubiquitination modifications are involved in PF induced by various stimuli, involving a range of ubiquitin-modifying enzymes and substrates. In this review, we provide an overview of how E3 ubiquitin ligases and deubiquitinating enzymes (DUBs) modulate PF through several signaling pathways, such as TGF-β, Wnt, metabolic activity, aging, ferroptosis, endoplasmic reticulum stress, and inflammatory responses. This perspective includes the role of ubiquitin-proteasome systems in interorgan communication, affecting the progression of PF and related systemic conditions. Additionally, we also summarize the currently available therapeutic compounds targeting protein ubiquitination-related enzymes or ubiquitination substrates for the treatment of PF. Understanding the interplay between ubiquitination and interorgan communication may pave the way for novel therapeutic strategies.

Acute kidney injury triggers hypoxemia by lung intravascular neutrophil retention that reduces capillary blood flow

Sterile acute kidney injury (AKI) is common in the clinic and frequently associated with unexplained hypoxemia that does not improve with dialysis. AKI induces remote lung inflammation with neutrophil recruitment in mice and humans, but which cellular cues establish neutrophilic inflammation and how it contributes to hypoxemia is not known. Here we report that AKI induced rapid intravascular neutrophil retention in lung alveolar capillaries without extravasation into tissue or alveoli, causing hypoxemia by reducing lung capillary blood flow in the absence of substantial lung interstitial or alveolar edema. In contrast to direct ischemic lung injury, lung neutrophil recruitment during remote lung inflammation did not require cues from intravascular nonclassical monocytes or tissue-resident alveolar macrophages. Instead, lung neutrophil retention depended on the neutrophil chemoattractant CXCL2 released by activated classical monocytes. Comparative single-cell RNA-Seq analysis of direct and remote lung inflammation revealed that alveolar macrophages were highly activated and produced CXCL2 only in direct lung inflammation. Establishing a CXCL2 gradient into the alveolus by intratracheal CXCL2 administration during AKI-induced remote lung inflammation enabled neutrophils to extravasate. We thus discovered important differences in lung neutrophil recruitment in direct versus remote lung inflammation and identified lung capillary neutrophil retention that negatively affected oxygenation by causing a ventilation-perfusion mismatch as a driver of AKI-induced hypoxemia.

Traffic jam in lung capillaries: inter-organ communication impedes gas exchange after acute kidney injury

Acute kidney injury (AKI) is a frequent complication in critically ill patients and triggers a systemic inflammatory response that can contribute to lung injury, ultimately worsening clinical outcomes. However, diagnostic and therapeutic strategies remain unavailable. In this issue of the JCI, Komaru et al. explored leukocyte trafficking and vascular pooling following AKI in mice as an underlying mechanism of acute lung injury. Using intravital microscopy, the authors observed rapid accumulation of neutrophils in pulmonary capillaries within minutes of AKI onset. These neutrophils followed monocytes and slowed blood flow. Notably, disruption of this process improved oxygenation. The findings provide insights into this complex inter-organ crosstalk and open avenues for future research.

Deficiency of Secreted Phosphoprotein 1 Alleviates Hyperoxia-induced Bronchopulmonary Dysplasia in Neonatal Mice

Bronchopulmonary dysplasia (BPD) is a common chronic lung disorder characterized by impaired proximal airway and bronchoalveolar development in premature births. Secreted phosphoprotein 1 (SPP1) is involved in lung development and lung injury events, while its role was not explored in BPD. For establishing the in vivo models of BPD, a mouse model of hyperoxia-induced lung injury was generated by exposing neonatal mice to hyperoxia for 7 days after birth. Alveolar myofibroblasts (AMYFs) were treated with hyperoxia to establish the in vitro models of BPD. Based on the scRNA-seq analysis of lungs of mice housed under normoxia or hyperoxia conditions, mouse macrophages and fibroblasts were main different cell clusters between the two groups, and differentially expressed genes in fibroblasts were screened. Further GO and KEGG enrichment analysis revealed that these differentially expressed genes were mainly enriched in the pathways related to cell proliferation, apoptosis as well as the PI3K-AKT and ERK/MAPK pathways. SPP1 was found up-regulated in the lung tissues of hyperoxia mice. We also demonstrated the up-regulation of SPP1 in the BPD patients, the mouse model of hyperoxia-induced lung injury, and hyperoxia-induced cells. SPP1 deficiency was revealed to reduce the hyperoxia-induced apoptosis, oxidative stress and inflammation and increase the viability of AMYFs. In the mouse model of hyperoxia induced lung injury, SPP1 deficiency was demonstrated to reverse the hyperoxia-induced alveolar growth disruption, oxidative stress and inflammation. Overall, SPP1 exacerbates BPD progression in vitro and in vivo by regulating oxidative stress and inflammatory response via the PI3K-AKT and ERK/MAPK pathways, which might provide novel therapeutic target for BPD therapy.

Circadian clock communication during homeostasis and ageing

Maintaining homeostasis is essential for continued health, and the progressive decay of homeostatic processes is a hallmark of ageing. Daily environmental rhythms threaten homeostasis, and circadian clocks have evolved to execute physiological processes in a manner that anticipates, and thus mitigates, their effects on the organism. Clocks are active in almost all cell types; their rhythmicity and functional output are determined by a combination of tissue-intrinsic and systemic inputs. Numerous inputs for a specific tissue are produced by the activity of circadian clocks of other tissues or cell types, generating a form of crosstalk known as clock communication. In mammals, the central clock in the hypothalamus integrates signals from external light-dark cycles to align peripheral clocks elsewhere in the body. This regulation is complemented by a tissue-specific milieu of external, systemic and niche inputs that modulate and cooperate with the cellular circadian clock machinery of a tissue to tailor its functional output. These mechanisms of clock communication decay during ageing, and growing evidence suggests that this decline might drive ageing-related morbidities. Dietary, behavioural and pharmacological interventions may offer the possibility to overcome these changes and in turn improve healthspan.

Microvascular aberrations found in human polycystic kidneys are an early feature in a Pkd1 mutant mouse model

Therapies targeting blood vessels hold promise for autosomal dominant polycystic kidney disease (ADPKD), the most common inherited disorder causing kidney failure. However, the onset and nature of kidney vascular abnormalities in ADPKD are poorly defined. Accordingly, we employed a combination of single-cell transcriptomics; three-dimensional imaging with geometric, topological and fractal analyses; and multimodal magnetic resonance imaging with arterial spin labelling to investigate aberrant microvasculature in ADPKD kidneys. Within human ADPKD kidneys with advanced cystic pathology and excretory failure, we identified a molecularly distinct blood microvascular subpopulation, characterised by impaired angiogenic signalling and metabolic dysfunction, differing from endothelial injury profiles observed in non-cystic human kidney diseases. Next, Pkd1 mutant mouse kidneys were examined postnatally, when cystic pathology is well established, but before excretory failure. An aberrant endothelial subpopulation was also detected, concurrent with reduced cortical blood perfusion. Disorganised kidney cortical microvasculature was also present in Pkd1 mutant mouse fetal kidneys when tubular dilation begins. Thus, aberrant features of cystic kidney vasculature are harmonised between human and mouse ADPKD, supporting early targeting of the vasculature as a strategy to ameliorate ADPKD progression.

The immune duality of osteopontin and its therapeutic implications for kidney transplantation

Osteopontin (OPN) is a multifunctional glycoprotein with various structural domains that enable it to perform diverse functions in both physiological and pathological states. This review comprehensively examines OPN from multiple perspectives, including its protein structure, interactions with receptors, interactions with immune cells, and roles in kidney diseases and transplantation. This review explores the immunological duality of OPN and its significance and value as a biomarker and therapeutic target in kidney transplantation. In cancer, OPN typically promotes tumor evasion by suppressing the immune system. Conversely, in immune-related kidney diseases, particularly kidney transplantation, OPN activates the immune system by enhancing the migration and activation of immune cells, thereby exacerbating kidney damage. This immunological duality may stem from different OPN splice variants and the exposure, after cleavage, of different structural domains, which play distinct biological roles in cellular interactions. Additionally, OPN has a significant biological impact posttransplantation and on chronic kidney disease and, highlighting its importance as a biomarker and potential therapeutic target. Future research should further explore the specific mechanisms of OPN in kidney transplantation to improve treatment strategies and enhance patient quality of life.

Acute kidney injury triggers hypoxemia by inducing intravascular neutrophil retention that reduces lung capillary blood flow

Sterile acute kidney injury (AKI) is common in the clinic and frequently associated with hypoxemia that does not improve with dialysis and remains incompletely understood. AKI induces remote lung inflammation with neutrophil recruitment in mice and humans, but which cellular cues establish neutrophilic inflammation and how it contributes to hypoxemia is not known. Here we report that AKI induces rapid intravascular neutrophil retention in lung alveolar capillaries without any significant extravasation into tissue or alveoli, causing hypoxemia by reducing lung capillary blood flow in the absence of any significant lung interstitial or alveolar edema. In contrast to direct ischemic lung injury, lung neutrophil recruitment during remote lung inflammation did not require cues from intravascular non-classical monocytes or tissue-resident alveolar macrophages. Instead, lung neutrophil retention depended on neutrophil chemoattractant CXCL2 released by activated intravascular classical monocytes. Comparative single-cell RNA-sequencing analysis of direct and remote lung inflammation revealed that alveolar macrophages are highly activated and produce the neutrophil chemoattractant CXCL2 only in direct lung inflammation. Establishing a CXCL2 gradient into the alveolus by intratracheal administration of CXCL2 during AKI-induced remote lung inflammation enabled neutrophils to extravasate. We thus discovered important differences in lung neutrophil recruitment in direct versus remote lung inflammation and identified lung capillary neutrophil retention that negatively affects oxygenation by causing a ventilation-perfusion mismatch as a novel driver of AKI-induced hypoxemia.

Targeting senescence to prevent diabetic kidney disease: Exploring molecular mechanisms and potential therapeutic targets for disease management

BACKGROUND/AIMS

As a microvascular complication, diabetic kidney disease is the leading cause of chronic kidney disease and end-stage renal disease worldwide. While the underlying pathophysiology driving transition of diabetic kidney disease to renal failure is yet to be fully understood, recent studies suggest that cellular senescence is central in disease development and progression. Consequently, understanding the molecular mechanisms which initiate and drive senescence in response to the diabetic milieu is crucial in developing targeted therapies that halt progression of renal disease.

METHODS

To understand the mechanistic pathways underpinning cellular senescence in the context of diabetic kidney disease, we reviewed the literature using PubMed for English language articles that contained key words related to senescence, inflammation, fibrosis, senescence-associated secretory phenotype (SASP), autophagy, and diabetes.

RESULTS

Aberrant accumulation of metabolically active senescent cells is a notable event in the progression of diabetic kidney disease. Through autocrine- and paracrine-mediated mechanisms, resident senescent cells potentiate inflammation and fibrosis through increased expression and secretion of pro-inflammatory cytokines, chemoattractants, recruitment of immune cells, myofibroblast activation, and extracellular matrix remodelling. Compounds that eliminate senescent cells and/or target the SASP - including senolytic and senomorphics drugs - demonstrate promising results in reducing the senescent cell burden and associated pro-inflammatory effect.

CONCLUSIONS

Here we evidence the link between senescence and diabetic kidney disease and highlight underlying molecular mechanisms and potential therapeutic targets that could be exploited to delay disease progression and improve outcomes for individuals with the disease. Trials are now required to translate their therapeutic potential to a clinical setting.

Multiomics Analysis Reveals Therapeutic Targets for Chronic Kidney Disease With Sarcopenia

BACKGROUND

The presence of sarcopenia in patients with chronic kidney disease (CKD) is associated with poor prognosis. The mechanism underlying CKD-induced muscle wasting has not yet been fully explored. This study investigates the influence of renal secretions on muscles using multiomics sequencing.

METHODS

The kidney transcriptome analysis by RNA-seq and protein profiling by tandem mass tag (TMT), serum TMT and muscle TMT were performed in CKD established using 0.2% adenine and control mice. Spp1 recombinant protein was used to study its effect on myotube atrophy in vitro. In animal experiments on CKD, pharmacological inhibition of Spp1 was used to explore the role of Spp1 in skeletal muscle wasting. Transcriptome analysis was performed to identify differentially expressed genes (DEGs) in the gastrocnemius muscle following Spp1 pharmacological inhibition.

RESULTS

In the renal transcriptome and TMT, 503 and 377 proteins/genes respectively were co-upregulated and co-downregulated. In the serum TMT of CKD and normal control (NC) mice, 22 upregulated and 7 downregulated differentially expressed proteins (DEPs) showed the same expression patterns as those in the kidney transcriptome and TMT analysis. Based on bioinformatics analysis and reported studies, we selected Spp1 for further validation. Spp1 recombinant protein was added to C2C12 myotubes in vitro, and the results indicated that Spp1 significantly increased the protein levels of the muscle atrophy marker (Murf-1) and promoted the smaller myotubes (all p < 0.05). Compared with NC mice, Spp1 mRNA and protein levels were significantly upregulated in the kidneys of CKD mice, and the serum concentration of Spp1 was also markedly increased (all p < 0.05). In animal experiments, pharmacological inhibition of Spp1 increased the weights of gastrocnemius and tibialis anterior muscles (p < 0.05) and improved muscle atrophy phenotype. Transcriptome analysis showed that DEGs in the gastrocnemius muscle following Spp1 pharmacological inhibition were enriched in protein digestion and absorption, glucagon signalling pathway, apelin signalling pathway and ECM-receptor interaction pathway.

CONCLUSIONS

Our study is the first to establish a regulatory network of kidney-muscle crosstalk to explore the potential mechanism of CKD-related sarcopenia. Employing multiomics analysis, cellular assessment and animal experiments, we have identified that Spp1 could potentialy serve as a promising therapeutic target for CKD patients with sarcopenia.

Permanent defects in renal medullary structure and function after reversal of urinary obstruction

Urinary obstruction causes injury to the renal medulla, impairing the ability to concentrate urine and increasing the risk of progressive kidney disease. However, the regenerative capacity of the renal medulla after reversal of obstruction is poorly understood. To investigate this, we developed a mouse model of reversible urinary obstruction. Despite robust regeneration and complete histological recovery of the renal medulla, these mice exhibited a permanent defect in urinary concentrating capacity. However, there were lasting changes in the composition, organization, and transcriptional profiles of epithelial, endothelial, and interstitial cells. Persistent inflammatory responses were also seen in patients with renal stone disease, but there were also adaptive responses to the increasingly hypoxic environment of the renal medulla that occurred only after reversal of obstruction. These findings indicate that while partial repair occurs after reversal of urinary obstruction, there are lasting structural and functional changes across all major cellular compartments of the renal medulla. These changes reflect shared and distinct responses to different renal medullary injuries in humans and mice.

Immune mediators in heart-lung communication

It is often the case that serious, end-stage manifestations of disease result from secondary complications in organs distinct from the initial site of injury or infection. This is particularly true of diseases of the heart-lung axis, given the tight anatomical connections of the two organs within a common cavity in which they collectively orchestrate the two major, intertwined circulatory pathways. Immune cells and the soluble mediators they secrete serve as effective, and targetable, messengers of signals between different regions of the body but can also contribute to the spread of pathology. In this review, we discuss the immunological basis of interorgan communication between the heart and lung in various common diseases, and in the context of organ crosstalk more generally. Gaining a greater understanding of how the heart and lung communicate in health and disease, and viewing disease progression generally from a more holistic, whole-body viewpoint have the potential to inform new diagnostic approaches and strategies for better prevention and treatment of comorbidities.

CCR7/DUSP1 signaling Axis mediates iCAF to regulates head and neck squamous cell carcinoma growth

OBJECTIVE

C-C motif chemokine receptor 7 (CCR7) significantly influences tumors onset and progression, yet its impact on the tumor microenvironment (TME) and specific mechanisms remain elusive. Inflammatory Cancer-Associated Fibroblasts (iCAF), a vital subtype of Cancer-Associated Fibroblasts (CAF), play a critical role in regulating the TME and tumor growth, though the underlying molecular mechanisms are not fully understood. This study aims to determine whether CCR7 participates in tumor regulation by iCAF and to elucidate the specific mechanisms involved.

METHODS

Differential gene analysis of CAF subtypes in CCR7 knockout and wild-type groups was conducted using single-cell data. Animal models facilitated the extraction of primary iCAF cells via flow cytometry sorting. Changes in DUSP1 expression and the efficiency of lentivirus-mediated knockdown and overexpression were examined through qPCR and Western Blot. MOC1 and MOC2 cells were co-cultured with iCAF, with subsequent validation of changes in tumor cell proliferation, migration, and invasion using CCK8, EdU, and wound healing assays. ELISA was employed to detect changes in TGF-β1 concentration in the iCAF supernatant.

RESULTS

CAF was categorized into three subtypes-myCAF, iCAF, and apCAF-based on single-cell data. Analysis revealed a significant increase in DUSP1 expression in iCAF from the CCR7 knockout group, confirmed by in vitro experiments. Co-culturing MOC1 and MOC2 cells with iCAF exhibiting lentivirus-mediated DUSP1 knockdown resulted in inhibited tumor cell proliferation, invasion, and migration. In contrast, co-culture with iCAF overexpressing DUSP1 enhanced these capabilities. Additionally, the TGF-β1 concentration in the supernatant increased in the DUSP1 knockdown iCAF group, whereas it decreased in the DUSP1 overexpression group.

CONCLUSION

The CCR7/DUSP1 signaling axis regulates tumor growth by modulating TGF-β1 secretion in iCAF.

Partial repair causes permanent defects in papillary structure and function after reversal of urinary obstruction

Urinary obstruction causes injury to the renal papilla and leads to defects in the ability to concentrate urine which predisposes to progressive kidney injury. However, the regenerative capacity of the papilla after reversal of obstruction is poorly understood. To address this, we developed a mouse model of reversible urinary obstruction which is characterized by extensive papillary injury, followed by a robust regeneration response and complete histological recovery over a 3- month period. However, these mice have a pronounced defect in urinary concentrating capacity. We now show that this is due to permanent changes in the composition, organization, and transcriptional signatures of epithelial, endothelial, and interstitial cell lineages in the papilla. There are persistent inflammatory responses that are also seen in patients with renal stone disease but are associated with cell-specific adaptive responses to the increasingly hypoxic environment of the papilla after reversal of obstruction. Taken together, our analysis of a new model of reversible urinary obstruction reveals that partial repair leads to permanent changes in the structure and function of all of the major cellular compartments in the papilla that include both shared and distinct responses to different types of renal papillary injury in humans and mice.

Summary

Partial repair after reversal of urinary obstruction leads to permanent changes in structure and function of all major cellular compartments in the renal papilla.

Gene expression profile of human placental villous pericytes in the first trimester - An analysis by single-cell RNA sequencing

Mesenchymal cells within theplacental villi play a crucial role in shaping the morphology of branching structures and driving the development of blood vessels. However, the markers and functions of placental villous pericytes (PVPs) as distinct subgroups of placental villous mesenchymal cells, remain unclear. Therefore, in this study, the markers and functions of PVPs were investigated. Single-cell sequencing data from the first-trimester placental villi was obtained and the Seurat tool was used to identify PVP markers. Gene Ontology (GO) analysis of specific genes was performed using the DAVID database. The Cellchat tool was employed to investigate the interaction signals between the PVPs and other cells. Expression of the PVP markers was confirmed using immunofluorescence. Presence of extracellular vesicles in the placental villous mesenchyme and PVPs was examined by transmission electron microscopy. Our findings revealed that renin (REN) and amphiregulin (AREG)-positive fibroblasts in the placental villi specifically expressed several classic pericyte markers. In the first trimester, certain conserved functions of pericytes were observed and they displayed tissue-specific functions such as in the integrin-mediated signaling pathway and extracellular exosomes. Moreover, the placental villous mesenchyme was found to be rich in extracellular vesicles. AREG is specifically transcribed in the first trimester PVPs, however, its protein was located in syncytiotrophoblasts. These insights contribute to a comprehensive understanding of early placental development and offer new therapeutic targets for placenta-derived pregnancy complications.

A Single-Cell Transcriptome Profiling of Triptolide-Induced Nephrotoxicity in Mice

Triptolide (TP), an active component isolated from the traditional Chinese herb Tripterygium wilfordii Hook F (TWHF), shows great promise for treating inflammation-related diseases. However, its potential nephrotoxic effects remain concerning. The mechanism underlying TP-induced nephrotoxicity is inadequately elucidated, particularly at single-cell resolution. Hence, single-cell RNA sequencing (scRNA-seq) of kidney tissues from control and TP-treated mice is performed to generate a thorough description of the renal cell atlas upon TP treatment. Heterogeneous responses of nephron epithelial cells are observed after TP exposure, attributing differential susceptibility of cell subtypes to excessive reactive oxygen species and increased inflammatory responses. Moreover, TP disrupts vascular function by activating endothelial cell immunity and damaging fibroblasts. Severe immune cell damage and the activation of pro-inflammatory Macro_C1 cells are also observed with TP treatment. Additionally, ligand-receptor crosstalk analysis reveals that the SPP1 (osteopontin) signaling pathway targeting Macro_C1 cells is triggered by TP treatment, which may promote the infiltration of Macro_C1 cells to exacerbate renal toxicity. Overall, this study provides comprehensive information on the transcriptomic profiles and cellular composition of TP-associated nephrotoxicity at single-cell resolution, which can strengthen the understanding of the pathogenesis of TP-induced nephrotoxicity and provide valuable clues for the discovery of new therapeutic targets to ameliorate TP-associated nephrotoxicity.

Plasma proteomics of acute tubular injury

The kidney tubules constitute two-thirds of the cells of the kidney and account for the majority of the organ's metabolic energy expenditure. Acute tubular injury (ATI) is observed across various types of kidney diseases and may significantly contribute to progression to kidney failure. Non-invasive biomarkers of ATI may allow for early detection and drug development. Using the SomaScan proteomics platform on 434 patients with biopsy-confirmed kidney disease, we here identify plasma biomarkers associated with ATI severity. We employ regional transcriptomics and proteomics, single-cell RNA sequencing, and pathway analysis to explore biomarker protein and gene expression and enriched biological pathways. Additionally, we examine ATI biomarker associations with acute kidney injury (AKI) in the Kidney Precision Medicine Project (KPMP) (n = 44), the Atherosclerosis Risk in Communities (ARIC) study (n = 4610), and the COVID-19 Host Response and Clinical Outcomes (CHROME) study (n = 268). Our findings indicate 156 plasma proteins significantly linked to ATI with osteopontin, macrophage mannose receptor 1, and tenascin C showing the strongest associations. Pathway analysis highlight immune regulation and organelle stress responses in ATI pathogenesis.

Cellular dynamics in pig-to-human kidney xenotransplantation

BACKGROUND

Xenotransplantation of genetically engineered porcine organs has the potential to address the challenge of organ donor shortage. Two cases of porcine-to-human kidney xenotransplantation were performed, yet the physiological effects on the xenografts and the recipients' immune responses remain largely uncharacterized.

METHODS

We performed single-cell RNA sequencing (scRNA-seq) and longitudinal RNA-seq analyses of the porcine kidneys to dissect xenotransplantation-associated cellular dynamics and xenograft-recipient interactions. We additionally performed longitudinal scRNA-seq of the peripheral blood mononuclear cells (PBMCs) to detect recipient immune responses across time.

FINDINGS

Although no hyperacute rejection signals were detected, scRNA-seq analyses of the xenografts found evidence of endothelial cell and immune response activation, indicating early signs of antibody-mediated rejection. Tracing the cells' species origin, we found human immune cell infiltration in both xenografts. Human transcripts in the longitudinal bulk RNA-seq revealed that human immune cell infiltration and the activation of interferon-gamma-induced chemokine expression occurred by 12 and 48 h post-xenotransplantation, respectively. Concordantly, longitudinal scRNA-seq of PBMCs also revealed two phases of the recipients' immune responses at 12 and 48-53 h. Lastly, we observed global expression signatures of xenotransplantation-associated kidney tissue damage in the xenografts. Surprisingly, we detected a rapid increase of proliferative cells in both xenografts, indicating the activation of the porcine tissue repair program.

CONCLUSIONS

Longitudinal and single-cell transcriptomic analyses of porcine kidneys and the recipient's PBMCs revealed time-resolved cellular dynamics of xenograft-recipient interactions during xenotransplantation. These cues can be leveraged for designing gene edits and immunosuppression regimens to optimize xenotransplantation outcomes.

FUNDING

This work was supported by NIH RM1HG009491 and DP5OD033430.

MMP-3 mediates copper oxide nanoparticle-induced pulmonary inflammation and fibrosis

BACKGROUND

The increasing production and usage of copper oxide nanoparticles (Nano-CuO) raise human health concerns. Previous studies have demonstrated that exposure to Nano-CuO could induce lung inflammation, injury, and fibrosis. However, the potential underlying mechanisms are still unclear. Here, we proposed that matrix metalloproteinase-3 (MMP-3) might play an important role in Nano-CuO-induced lung inflammation, injury, and fibrosis.

RESULTS

Exposure of mice to Nano-CuO caused acute lung inflammation and injury in a dose-dependent manner, which was reflected by increased total cell number, neutrophil count, macrophage count, lactate dehydrogenase (LDH) activity, and CXCL1/KC level in bronchoalveolar lavage fluid (BALF) obtained on day 3 post-exposure. The time-response study showed that Nano-CuO-induced acute lung inflammation and injury appeared as early as day 1 after exposure, peaked on day 3, and ameliorated over time. However, even on day 42 post-exposure, the LDH activity and macrophage count were still higher than those in the control group, suggesting that Nano-CuO caused chronic lung inflammation. The Nano-CuO-induced pulmonary inflammation was further confirmed by H&E staining of lung sections. Trichrome staining showed that Nano-CuO exposure caused pulmonary fibrosis from day 14 to day 42 post-exposure with an increasing tendency over time. Increased hydroxyproline content and expression levels of fibrosis-associated proteins in mouse lungs were also observed. In addition, Nano-CuO exposure induced MMP-3 overexpression and increased MMP-3 secretion in mouse lungs. Knocking down MMP-3 in mouse lungs significantly attenuated Nano-CuO-induced acute and chronic lung inflammation and fibrosis. Moreover, Nano-CuO exposure caused sustained production of cleaved osteopontin (OPN) in mouse lungs, which was also significantly decreased by knocking down MMP-3.

CONCLUSIONS

Our results demonstrated that short-term Nano-CuO exposure caused acute lung inflammation and injury, while long-term exposure induced chronic pulmonary inflammation and fibrosis. Knocking down MMP-3 significantly ameliorated Nano-CuO-induced pulmonary inflammation, injury, and fibrosis, and also attenuated Nano-CuO-induced cleaved OPN level. Our study suggests that MMP-3 may play important roles in Nano-CuO-induced pulmonary inflammation and fibrosis via cleavage of OPN and may provide a further understanding of the mechanisms underlying Nano-CuO-induced pulmonary toxicity.

The mouse multi-organ proteome from infancy to adulthood

The early-life organ development and maturation shape the fundamental blueprint for later-life phenotype. However, a multi-organ proteome atlas from infancy to adulthood is currently not available. Herein, we present a comprehensive proteomic analysis of ten mouse organs (brain, heart, lung, liver, kidney, spleen, stomach, intestine, muscle and skin) at three crucial developmental stages (1-, 4- and 8-weeks after birth) acquired using data-independent acquisition mass spectrometry. We detect and quantify 11,533 protein groups across the ten organs and obtain 115 age-related differentially expressed protein groups that are co-expressed in all organs from infancy to adulthood. We find that spliceosome proteins prevalently play crucial regulatory roles in the early-life development of multiple organs, and detect organ-specific expression patterns and sexual dimorphism. This multi-organ proteome atlas provides a fundamental resource for understanding the molecular mechanisms underlying early-life organ development and maturation.

Bidirectional pressure: a mini review of ventilator-lung-kidney interactions

Acute kidney injury and respiratory failure that requires mechanical ventilation are both common complications of critical illnesses. Failure of either of these organ systems also increases the risk of failure to the other. As a result, there is a high incidence of patients with concomitant acute kidney injury and the need for mechanical ventilation, which has a devasting impact on intensive care unit outcomes, including mortality. Despite decades of research into the mechanisms of ventilator-lung-kidney interactions, several gaps in knowledge remain and current treatment strategies are primarily supportive. In this review, we outline our current understanding of the mechanisms of acute kidney injury due to mechanical ventilation including a discussion of; 1) The impact of mechanical ventilation on renal perfusion, 2) activation of neurohormonal pathways by positive pressure ventilation, and 3) the role of inflammatory mediators released during ventilator induced lung injury. We also provide a review of the mechanisms by which acute kidney injury increases the risk of respiratory failure. Next, we outline a summary of the current therapeutic approach to preventing lung and kidney injury in the critically ill, including fluid and vasopressor management, ventilator strategies, and treatment of acute kidney injury. Finally, we conclude with a discussion outlining opportunities for novel investigations that may provide a rationale for new treatment approaches.

Systematic Review of Kidney Injury Biomarkers for the Evaluation of CKD of Uncertain Etiology

Introduction

Chronic kidney disease of uncertain etiology (CKDu) is an incompletely defined phenotype of chronic kidney disease (CKD) affecting young individuals mostly in agricultural communities in Central America and South Asia. CKDu is a diagnosis of exclusion made in individuals from endemic regions.

Methods

We conducted a systematic review of the primary literature on urinary and plasma kidney injury biomarkers measured in the setting of CKDu (through February 2023). The literature was identified via a Web of Science search and hand search of the references of previously identified literature. Search terms included "CKDu," "Mesoamerican Nephropathy," "CKD of unknown etiology," "Chronic Interstitial Nephritis in Agricultural Communities," "biomarker," "urin∗," and/or "plasma."

Results

A total of 25 papers were included. The 2 most frequently measured biomarkers were urinary kidney injury molecule-1 (KIM-1) and urinary neutrophil gelatinase-associated lipocalin (NGAL). There was substantial variability in study design, laboratory assay methods, and statistical methodology, which prohibited meta-analysis.

Conclusion

Biomarkers that identify tubulointerstitial disease early and accurately may substantially accelerate progress in the study of CKDu and facilitate public health approaches that eventually lead to its prevention and elimination. To date, the literature is limited by relatively small sample sizes and methodological limitations which should be addressed in future studies.

Single-cell RNA sequencing reveals the evolution of the immune landscape during perihematomal edema progression after intracerebral hemorrhage

BACKGROUND

Perihematomal edema (PHE) after post-intracerebral hemorrhage (ICH) has complex pathophysiological mechanisms that are poorly understood. The complicated immune response in the post-ICH brain constitutes a crucial component of PHE pathophysiology. In this study, we aimed to characterize the transcriptional profiles of immune cell populations in human PHE tissue and explore the microscopic differences between different types of immune cells.

METHODS

9 patients with basal ganglia intracerebral hemorrhage (hematoma volume 50-100 ml) were enrolled in this study. A multi-stage profile was developed, comprising Group1 (n = 3, 0-6 h post-ICH, G1), Group2 (n = 3, 6-24 h post-ICH, G2), and Group3 (n = 3, 24-48 h post-ICH, G3). A minimal quantity of edematous tissue surrounding the hematoma was preserved during hematoma evacuation. Single cell RNA sequencing (scRNA-seq) was used to map immune cell populations within comprehensively resected PHE samples collected from patients at different stages after ICH.

RESULTS

We established, for the first time, a comprehensive landscape of diverse immune cell populations in human PHE tissue at a single-cell level. Our study identified 12 microglia subsets and 5 neutrophil subsets in human PHE tissue. What's more, we discovered that the secreted phosphoprotein-1 (SPP1) pathway served as the basis for self-communication between microglia subclusters during the progression of PHE. Additionally, we traced the trajectory branches of different neutrophil subtypes. Finally, we also demonstrated that microglia-produced osteopontin (OPN) could regulate the immune environment in PHE tissue by interacting with CD44-positive cells.

CONCLUSIONS

As a result of our research, we have gained valuable insight into the immune-microenvironment within PHE tissue, which could potentially be used to develop novel treatment modalities for ICH.

Histopathological evaluation of the lungs in experimental autoimmune encephalomyelitis

IMPORTANCE

Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis characterized by inflammation within the central nervous system. However, inflammation in non-neuronal tissues, including the lungs, has not been fully evaluated.

OBJECTIVE

This study evaluated the inflammatory response in lungs of EAE mice by immunohistochemistry and histochemistry.

METHODS

Eight adult C57BL/6 mice were injected with myelin oligodendrocyte glycoprotein35-55 to induce the EAE. Lungs and spinal cords were sampled from the experimental mice at the time of sacrifice and used for the western blotting, histochemistry, and immunohistochemistry.

RESULTS

Histopathological examination revealed inflammatory lesions in the lungs of EAE mice, characterized by infiltration of myeloperoxidase (MPO)- and galectin-3-positive cells, as determined by immunohistochemistry. Increased numbers of collagen fibers in the lungs of EAE mice were confirmed by histopathological analysis. Western blotting revealed significantly elevated level of osteopontin (OPN), cluster of differentiation 44 (CD44), MPO and galectin-3 in the lungs of EAE mice compared with normal controls (p < 0.05). Immunohistochemical analysis revealed both OPN and CD44 in ionized calcium-binding adapter molecule 1-positive macrophages within the lungs of EAE mice.

CONCLUSIONS AND RELEVANCE

Taken together, these findings suggest that the increased OPN level in lungs of EAE mice led to inflammation; concurrent increases in proinflammatory factors (OPN and galectin-3) caused pulmonary impairment.

Targeted Macrophage CRISPR-Cas13 mRNA Editing in Immunotherapy for Tendon Injury

CRISPR-Cas13 holds substantial promise for tissue repair through its RNA editing capabilities and swift catabolism. However, conventional delivery methods fall short in addressing the heightened inflammatory response orchestrated by macrophages during the acute stages of tendon injury. In this investigation, macrophage-targeting cationic polymers are systematically screened to facilitate the entry of Cas13 ribonucleic-protein complex (Cas13 RNP) into macrophages. Notably, SPP1 (OPN encoding)-producing macrophages are recognized as a profibrotic subtype that emerges during the inflammatory stage. By employing ROS-responsive release mechanisms tailored for macrophage-targeted Cas13 RNP editing systems, the overactivation of SPP1 is curbed in the face of an acute immune microenvironment. Upon encapsulating this composite membrane around the tendon injury site, the macrophage-targeted Cas13 RNP effectively curtails the emergence of injury-induced SPP1-producing macrophages in the acute phase, leading to diminished fibroblast activation and mitigated peritendinous adhesion. Consequently, this study furnishes a swift RNA editing strategy for macrophages in the inflammatory phase triggered by ROS in tendon injury, along with a pioneering macrophage-targeted carrier proficient in delivering Cas13 into macrophages efficiently.

Proteomic analysis of multiple organ dysfunction induced by rhabdomyolysis

Rhabdomyolysis (RM) leads to dysfunction in the core organs of kidney, lung and heart, which is an important reason for the high mortality and disability rate of this disease. However, there is a lack of systematic research on the characteristics of rhabdomyolysis-induced injury in various organs and the underlying pathogenetic mechanisms, and especially the interaction between organs. We established a rhabdomyolysis model, observed the structural and functional changes in kidney, heart, and lung. It is observed that rhabdomyolysis results in significant damage in kidney, lung and heart of rats, among which the pathological damage of kidney and lung was significant, and of heart was relatively light. Meanwhile, we analyzed the differentially expressed proteins (DEPs) in the kidney, heart and lung between the RM group and the sham group based on liquid chromatography-tandem mass spectrometry (LC-MS/MS). In our study, Serpina3n was significantly up-regulated in the kidney, heart and lung. Serpina3n is a secreted protein and specifically inhibits a variety of proteases and participates in multiple physiological processes such as complement activation, inflammatory responses, apoptosis pathways, and extracellular matrix metabolism. It is inferred that Serpina3n may play an important role in multiple organ damage caused by rhabdomyolysis and could be used as a potential biomarker. This study comprehensively describes the functional and structural changes of kidney, heart and lung in rats after rhabdomyolysis, analyzes the DEPs of kidney, heart and lung, and determines the key role of Serpina3n in multiple organ injury caused by rhabdomyolysis. SIGNIFICANCE: This study comprehensively describes the functional and structural changes of kidney, heart and lung in rats after rhabdomyolysis, analyzes the DEPs of kidney, heart and lung, and determines the key role of Serpina3n in multiple organ injury caused by rhabdomyolysis.

The importance of translational science within the respiratory field

The Translational Science Working Group at the European Respiratory Society (ERS) aims to bridge the gap between basic and clinical science by providing a platform where scientists, clinicians and experts in the respiratory field can actively shape translational research. For the 2023 Congress, dedicated translational science sessions were created and sessions of interest to many assemblies from the clinical and the scientific point of view were tagged as translational sessions, attracting clinical and scientific experts to the same room to discuss relevant topics and strengthening translational efforts among all ERS assemblies.

Metabolic Rewiring and Communication: An Integrative View of Kidney Proximal Tubule Function

The kidney proximal tubule is a key organ for human metabolism. The kidney responds to stress with altered metabolite transformation and perturbed metabolic pathways, an ultimate cause for kidney disease. Here, we review the proximal tubule's metabolic function through an integrative view of transport, metabolism, and function, and embed it in the context of metabolome-wide data-driven research. Function (filtration, transport, secretion, and reabsorption), metabolite transformation, and metabolite signaling determine kidney metabolic rewiring in disease. Energy metabolism and substrates for key metabolic pathways are orchestrated by metabolite sensors. Given the importance of renal function for the inner milieu, we also review metabolic communication routes with other organs. Exciting research opportunities exist to understand metabolic perturbation of kidney and proximal tubule function, for example, in hypertension-associated kidney disease. We argue that, based on the integrative view outlined here, kidney diseases without genetic cause should be approached scientifically as metabolic diseases.

Interorgan communication networks in the kidney-lung axis

The homeostasis and health of an organism depend on the coordinated interaction of specialized organs, which is regulated by interorgan communication networks of circulating soluble molecules and neuronal connections. Many diseases that seemingly affect one primary organ are really multiorgan diseases, with substantial secondary remote organ complications that underlie a large part of their morbidity and mortality. Acute kidney injury (AKI) frequently occurs in critically ill patients with multiorgan failure and is associated with high mortality, particularly when it occurs together with respiratory failure. Inflammatory lung lesions in patients with kidney failure that could be distinguished from pulmonary oedema due to volume overload were first reported in the 1930s, but have been largely overlooked in clinical settings. A series of studies over the past two decades have elucidated acute and chronic kidney-lung and lung-kidney interorgan communication networks involving various circulating inflammatory cytokines and chemokines, metabolites, uraemic toxins, immune cells and neuro-immune pathways. Further investigations are warranted to understand these clinical entities of high morbidity and mortality, and to develop effective treatments.

Osteopontin: A Novel Therapeutic Target for Respiratory Diseases

Osteopontin (OPN) is a multifunctional phosphorylated protein that is involved in physiological and pathological events. Emerging evidence suggests that OPN also plays a critical role in the pathogenesis of respiratory diseases. OPN can be produced and secreted by various cell types in lungs and overexpression of OPN has been found in acute lung injury/acute respiratory distress syndrome (ALI/ARDS), pulmonary hypertension (PH), pulmonary fibrosis diseases, lung cancer, lung infection, chronic obstructive pulmonary disease (COPD), and asthma. OPN exerts diverse effects on the inflammatory response, immune cell activation, fibrosis and tissue remodeling, and tumorigenesis of these respiratory diseases, and genetic and pharmacological moudulation of OPN exerts therapeutic effects in the treatment of respiratory diseases. In this review, we summarize the recent evidence of multifaceted roles and underlying mechanisms of OPN in these respiratory diseases, and targeting OPN appears to be a potential therapeutic intervention for these diseases.

High Plasma Osteopontin Levels Are Associated with Serious Post-Acute-COVID-19-Related Dyspnea

COVID-19 survivors commonly report persistent symptoms. In this observational study, we investigated the link between osteopontin (OPN) and post-acute COVID-19 symptoms and lung functional/imaging abnormalities. We recorded symptoms and lung imaging/functional data from previously hospitalized COVID-19 patients, who were followed for 4-84 weeks (122 patients/181 visits) post-symptom onset at our outpatient clinic. Circulating OPN was determined using ELISA. Plasma OPN levels were higher in symptomatic patients (compared with the asymptomatic ones); those with dyspnea (compared with those without dyspnea);those with a combination of serious symptoms, i.e., the presence of at least one of the following: dyspnea, fatigue and muscular weakness (compared with those with none of these symptoms); and those with dyspnea and m-MRC > 1 (compared with those with m-MRC = 0-1). Plasma OPN levels were inversely correlated with EQ-VAS (visual analog scale of the EQ-5D-5L health-related quality-of-life questionnaire) values. High-resolution CT or diffusion lung capacity (DLCO) findings were not related to circulating OPN. In the multiple logistic regression, the presence of symptoms, dyspnea, or the combination of serious symptoms were linked to female gender, increased BMI and pre-existing dyspnea (before the acute disease), while increased plasma OPN levels, female gender and pre-existing dyspnea with m-MRC > 1 were independently associated with severe post-COVID-19 dyspnea (m-MRC > 1). Using a correlation matrix to investigate multiple correlations between EQ-VAS, OPN and epidemiological data, we observed an inverse correlation between the OPN and EQ-VAS values. Increased circulating OPN was linked to the persistence of severe exertional dyspnea and impaired quality of life in previously hospitalized COVID-19 patients.

Gut microbiota and neonatal acute kidney injury biomarkers

One of the most frequent issues in newborns is acute kidney injury (AKI), which can lengthen their hospital stay or potentially raise their chance of dying. The gut-kidney axis establishes a bidirectional interplay between gut microbiota and kidney illness, particularly AKI, and demonstrates the importance of gut microbiota to host health. Since the ability to predict neonatal AKI using blood creatinine and urine output as evaluation parameters is somewhat constrained, a number of interesting biomarkers have been developed. There are few in-depth studies on the relationships between these neonatal AKI indicators and gut microbiota. In order to gain fresh insights into the gut-kidney axis of neonatal AKI, this review is based on the gut-kidney axis and describes relationships between gut microbiota and neonatal AKI biomarkers.

Acute Kidney Injury-Induced Circulating TNFR1/2 Elevations Correlate with Persistent Kidney Injury and Progression to Fibrosis

Elevated levels of circulating tumor necrosis factor receptors 1 and 2 (cTNFR1/2) predict chronic kidney disease (CKD) progression; however, the mechanisms of their release remain unknown. Whether acute kidney injury (AKI) drives cTNFR1/2 elevations and whether they predict disease outcomes after AKI remain unknown. In this study, we used AKI patient serum and urine samples, mouse models of kidney injury (ischemic, obstructive, and toxic), and progression to fibrosis, nephrectomy, and related single-cell RNA-sequencing datasets to experimentally test the role of kidney injury on cTNFR1/2 levels. We show that TNFR1/2 serum and urine levels are highly elevated in all of the mouse models of kidney injury tested, beginning within one hour post injury, and correlate with its severity. Consistent with this, serum and urine TNFR1/2 levels are increased in AKI patients and correlate with the severity of kidney failure. Kidney tissue expression of TNFR1/2 after AKI is only slightly increased and bilateral nephrectomies lead to strong cTNFR1/2 elevations, suggesting the release of these receptors by extrarenal sources. The injection of the uremic toxin indoxyl sulfate in healthy mice induces moderate cTNFR1/2 elevations. Moreover, TNF neutralization does not affect early cTNFR1/2 elevations after AKI. These data suggest that cTNFR1/2 levels in AKI do not reflect injury-induced TNF activity, but rather a rapid response to loss of kidney function and uremia. In contrast to traditional disease biomarkers, such as serum creatinine or BUN, cTNFR1/2 levels remain elevated for weeks after severe kidney injury. At these later timepoints, cTNFR1/2 levels positively correlate with remaining kidney injury. During the AKI-to-CKD transition, elevations of TNFR1/2 kidney expression and of cTNFR2 levels correlate with kidney fibrosis levels. In conclusion, our data demonstrate that kidney injury drives acute increases in cTNFR1/2 serum levels, which negatively correlate with kidney function. Sustained TNFR1/2 elevations after kidney injury during AKI-to-CKD transition reflect persistent tissue injury and progression to kidney fibrosis.

The Role of Osteopontin in Respiratory Health and Disease

The biological functions of osteopontin (OPN) are diverse and specific to physiological and pathophysiological conditions implicated in inflammation, biomineralization, cardiovascular diseases, cellular viability, cancer, diabetes, and renal stone disease. We aimed to present the role of OPN in respiratory health and disease. OPN influences the immune system and is a chemo-attractive protein correlated with respiratory disease severity. There is evidence that OPN can advance the disease stage associated with its fibrotic, inflammatory, and immune functions. OPN contributes to eosinophilic airway inflammation. OPN can destroy the lung parenchyma through its neutrophil influx and fibrotic mechanisms, linking OPN to at least one of the two major chronic obstructive pulmonary disease phenotypes. Respiratory diseases that involve irreversible lung scarring, such as idiopathic pulmonary disease, are linked to OPN, with protein levels being overexpressed in individuals with severe or advanced stages of the disorders and considerably lower levels in those with less severe symptoms. OPN plays a significant role in lung cancer progression and metastasis. It is also implicated in the pathogenesis of pulmonary hypertension, coronavirus disease 2019, and granuloma generation.

Regulatory roles of Osteopontin in lung epithelial inflammation and epithelial-telocyte interaction

BACKGROUND

Lung epithelial cells play important roles in lung inflammation and injury, although mechanisms remain unclear. Osteopontin (OPN) has essential roles in epithelial damage and repair and in lung cancer biological behaviours. Telocyte (TC) is a type of interstitial cell that interacts with epithelial cells to alleviate acute inflammation and lung injury. The present studies aim at exploring potential mechanisms by which OPN regulates the epithelial origin lung inflammation and the interaction of epithelial cells with TCs in acute and chronic lung injury.

METHODS

The lung disease specificity of OPN and epithelial inflammation were defined by bioinformatics. We evaluated the regulatory roles of OPN in OPN-knockdown or over-expressed bronchial epithelia (HBEs) challenged with cigarette smoke extracts (CSE) or in animals with genome OPN knockout (gKO) or lung conditional OPN knockout (cKO). Acute lung injury and chronic obstructive pulmonary disease (COPD) were induced by smoking or lipopolysaccharide (LPS). Effects of OPN on PI3K subunits and ERK were assessed using the inhibitors. Spatialization and distribution of OPN, OPN-positive epithelial subtypes, and TCs were defined by spatial transcriptomics. The interaction between HBEs and TCs was assayed by the co-culture system.

RESULTS

Levels of OPN expression increased in smokers, smokers with COPD, and smokers with COPD and lung cancer, as compared with healthy nonsmokers. LPS and/or CSE induced over-production of cytokines from HBEs, dependent upon the dysfunction of OPN. The severity of lung inflammation and injury was significantly lower in OPN-gKO or OPN-cKO mice. HBEs transferred with OPN enhanced the expression of phosphoinositide 3-kinase (PI3K)CA/p110α, PIK3CB/p110β, PIK3CD/p110δ, PIK3CG/p110γ, PIK3R1, PIK3R2 or PIK3R3. Spatial locations of OPN and OPN-positive epithelial subtypes showed the tight contact of airway epithelia and TCs. Epithelial OPN regulated the epithelial communication with TCs, and the down-regulation of OPN induced more alterations in transcriptomic profiles than the up-regulation.

CONCLUSION

Our data evidenced that OPN regulated lung epithelial inflammation, injury, and cell communication between epithelium and TCs in acute and chronic lung injury. The conditional control of lung epithelial OPN may be an alternative for preventing and treating epithelial-origin lung inflammation and injury.

Subcutaneous Tocilizumab May Be Effective in Refractory Fibromyalgia Patients

INTRODUCTION

Fibromyalgia (FM) is a chronic disorder characterized by widespread pain with an enormous symptom burden. Its treatment efficacy is limited. Its pathogenesis involves immune dysregulation, which includes interleukin-6 (IL-6) production.

METHODS

We herein reported a case series of FM patients receiving subcutaneous tocilizumab at our institution. FM symptoms were evaluated by the revised Fibromyalgia Impact Questionnaire (FIQR), which included pain level, and the fibromyalgianess scale based on the 2016 criteria of the American College of Rheumatology (ACR). FM symptoms were compared using the Wilcoxon signed-rank test. Neutrophils from primary FM patients and matched healthy controls were also isolated for transcriptome analysis.

RESULTS

We presented a total of two primary and four secondary FM patients who had received subcutaneous tocilizumab for a minimum of 12 weeks. All patients had severe symptoms despite standard treatments. Patients' FIQR and fibromyalgianess both dropped at 4 and 12 weeks. Four (67%) of them reached a pain reduction of ≥30% at 4 weeks, and three (50%) reached a pain reduction of ≥30% at 12 weeks. Possible differentially expressed genes were identified in primary FM patients when compared with controls and after tocilizumab treatment.

CONCLUSIONS

FM patients likely benefited from subcutaneous tocilizumab therapy. A randomized controlled trial is needed to verify its efficacy.

TNF or EGFR inhibition equally block AKI-to-CKD transition: opportunities for etanercept treatment

BACKGROUND

Inflammation is a key driver of the transition of acute kidney injury to progressive fibrosis and chronic kidney disease (AKI-to-CKD transition). Blocking a-disintegrin-and-metalloprotease-17 (ADAM17)-dependent ectodomain shedding, in particular of epidermal growth factor receptor (EGFR) ligands and of the type 1 inflammatory cytokine tumor necrosis factor (TNF), reduces pro-inflammatory and pro-fibrotic responses after ischemic AKI or unilateral ureteral obstruction (UUO), a classical fibrosis model. Metalloprotease or EGFR inhibition show significant undesirable side effects in humans. In retrospective studies anti-TNF biologics reduce the incidence and progression of CKD in humans. Whether TNF has a role in AKI-to-CKD transition and how TNF inhibition compares to EGFR inhibition is largely unknown.

METHODS

Mice were subjected to bilateral renal ischemia-reperfusion injury or unilateral ureteral obstruction. Kidneys were analyzed by histology, immunohistochemistry, qPCR, western blot, mass cytometry, scRNA sequencing, and cytokine profiling.

RESULTS

Here we show that TNF or EGFR inhibition reduce AKI-to-CKD transition and fibrosis equally by about 25%, while combination has no additional effect. EGFR inhibition reduced kidney TNF expression by about 50% largely by reducing accumulation of TNF expressing immune cells in the kidney early after AKI, while TNF inhibition did not affect EGFR activation or immune cell accumulation. Using scRNAseq data we show that TNF is predominantly expressed by immune cells in AKI but not in proximal tubule cells (PTC), and PTC-TNF knockout did not affect AKI-to-CKD transition in UUO. Thus, the anti-inflammatory and anti-fibrotic effects of the anti-TNF biologic etanercept in AKI-to-CKD transition rely on blocking TNF that is released from immune cells recruited or accumulating in response to PTC-EGFR signals.

CONCLUSION

Short-term anti-TNF biologics during or after AKI could be helpful in the prevention of AKI-to-CKD transition.

Renal-Clearable Probe with Water Solubility and Photostability for Biomarker-Activatable Detection of Acute Kidney Injuries via NIR-II Fluorescence and Optoacoustic Imaging

Acute kidney injuries (AKI) have serious short-term or long-term complications with high morbidity and mortality rate, thus posing great health threats. Developing high-performance NIR-II probes for noninvasive in situ detection of AKI via NIR-II fluorescent and optoacoustic dual-mode imaging is of great significance. Yet NIR-II chromophores often feature long conjugation and hydrophobicity, which prevent them from being renal clearable, thus limiting their applications in the detection and imaging of kidney diseases. To fully exploit the advantageous features of heptamethine cyanine dye, while overcoming its relatively poor photostability, and to strive to design a NIR-II probe for the detection and imaging of AKI with dual-mode imaging, herein, we have developed the probe PEG3-HC-PB, which is renal clearable, water soluble, and biomarker activatable and has good photostability. As for the probe, its fluorescence (900-1200 nm) is quenched due to the existence of the electron-pulling phenylboronic group (responsive element), and it exhibits weak absorption with a peak at 830 nm. Meanwhile, in the presence of the overexpressed H₂O₂ in the renal region in the case of AKI, the phenylboronic group is converted to the phenylhydroxy group, which enhances NIR-II fluorescent emission (900-1200 nm) and absorption (600-900 nm) and eventually produces conspicuous optoacoustic signals and NIR-II fluorescent emission for imaging. This probe enables detection of contrast-agent-induced and ischemia/reperfusion-induced AKI in mice using real-time 3D-MSOT and NIR-II fluorescent dual-mode imaging via response to the biomarker H₂O₂. Hence, this probe can be used as a practicable tool for detecting AKI; additionally, its design strategy could provide insight into the design of other large-conjugation NIR-II probes with multifarious biological applications.

Acute kidney injury and distant organ dysfunction-network system analysis

Acute kidney injury (AKI) occurs in about half of critically ill patients and associates with high in-hospital mortality, increased long-term mortality post-discharge and subsequent progression to chronic kidney disease. Numerous clinical studies have shown that AKI is often complicated by dysfunction of distant organs, which is a cause of the high mortality associated with AKI. Experimental studies have elucidated many mechanisms of AKI-induced distant organ injury, which include inflammatory cytokines, oxidative stress and immune responses. This review will provide an update on evidence of organ crosstalk and potential therapeutics for AKI-induced organ injuries, and present the new concept of a systemic organ network to balance homeostasis and inflammation that goes beyond kidney-crosstalk with a single distant organ.

Increased Circulating Osteopontin Levels Promote Primary Tumour Growth, but Do Not Induce Metastasis in Melanoma

Osteopontin (OPN) is a phosphoprotein with diverse functions in various physiological and pathological processes. OPN expression is increased in multiple cancers, and OPN within tumour tissue has been shown to promote key stages of cancer development. OPN levels are also elevated in the circulation of cancer patients, which in some cases has been correlated with enhanced metastatic propensity and poor prognosis. However, the precise impact of circulating OPN (cOPN) on tumour growth and progression remains insufficiently understood. To examine the role of cOPN, we used a melanoma model, in which we stably increased the levels of cOPN through adeno-associated virus-mediated transduction. We found that increased cOPN promoted the growth of primary tumours, but did not significantly alter the spontaneous metastasis of melanoma cells to the lymph nodes or lungs, despite an increase in the expression of multiple factors linked to tumour progression. To assess whether cOPN has a role at later stages of metastasis formation, we employed an experimental metastasis model, but again could not detect any increase in pulmonary metastasis in animals with elevated levels of cOPN. These results demonstrate that increased levels of OPN in the circulation play distinct roles during different stages of melanoma progression.

Proteomics and transcriptomics profiling reveals distinct aspects of kidney stone related genes in calculi rats

BACKGROUNDS

Kidney stone also known as urolithiasis or nephrolithiasis, is one of the oldest diseases known to medicine, however, the gene expression changes and related kidney injury remains unclear.

METHODS

A calculi rat model was developed via ethylene glycol- and ammonium chloride-induction. Integrated proteomic and transcriptomic analysis was performed to characterize the distinct gene expression profiles in the kidney of calculi rat. Differential expressed genes (DEGs) were sub-clustered into distinct groups according to the consistency of transcriptome and proteome. Gene Ontology and KEGG pathway enrichment was performed to analyze the functions of each sub-group of DEGs. Immunohistochemistry was performed to validated the expression of identified proteins.

RESULTS

Five thousand eight hundred ninety-seven genes were quantified at both transcriptome and proteome levels, and six distinct gene clusters were identified, of which 14 genes were consistently dysregulated. Functional enrichment analysis showed that the calculi rat kidney was increased expression of injured & apoptotic markers and immune-molecules, and decreased expression of solute carriers & transporters and many metabolic related factors.

CONCLUSIONS

The present proteotranscriptomic study provided a data resource and new insights for better understanding of the pathogenesis of nephrolithiasis, will hopefully facilitate the future development of new strategies for the recurrence prevention and treatment in patients with kidney stone disease.

Lung cancer-kidney cross talk induces kidney injury, interstitial fibrosis, and enhances cisplatin-induced nephrotoxicity

Patients with cancer represent a unique patient population with increased susceptibility to kidney disease. Drug-induced acute kidney injury (AKI) in patients with cancer is a common problem. Cisplatin is a highly effective treatment used in many solid-organ cancers and causes AKI in 30% of patients, increasing the risk of chronic kidney disease development. Most preclinical cisplatin toxicity studies have been completed in mice without cancer. We believe that the physiology of patients with cancer is not adequately represented in preclinical models, and the objective of this study was to determine how lung cancer will alter the nephrotoxicity of cisplatin. A genetically engineered mouse model and a syngeneic xenograft model of lung cancer were used. Mice were divided into the following four groups: 1) noncancer/vehicle, 2) noncancer/cisplatin, 3) cancer/vehicle, and 4) cancer/cisplatin. Mice were administered cisplatin via intraperitoneal injection once a week for 4 wk. Animals were euthanized 72 h following their final cisplatin injection. Mice with lung cancer had increased renal toxicity, injury, and fibrosis following repeated low doses of cisplatin. In addition, lung cancer alone induced kidney injury and fibrosis in the kidney before cisplatin treatment. In conclusion, this is the first study that we are aware of that assesses the impact of cancer on the kidney in conjunction with the nephrotoxicity of cisplatin. We believe that cancer is providing the first hit to the kidney and the subsequent damage from repeated doses of cisplatin becomes unsurmountable, leading to AKI and progression to chronic kidney disease.NEW & NOTEWORTHY Patients with cancer have impaired kidney function and increased susceptibility to nephrotoxic agents. Cisplatin is a commonly used chemotherapeutic with nephrotoxicity as the dose-limiting side effect. Cisplatin nephrotoxicity is almost exclusively studied in mice without cancer. Our current preclinical models do not adequately represent the complexity of patients with cancer. This study demonstrates increased renal toxicity, injury, and fibrosis in mice with lung cancer, which is exacerbated with cisplatin treatment. These results highlight the necessity of using preclinical models that more accurately capture the altered physiology of patients with cancer treated with cisplatin.

Mineral bone disorders and kidney disease in hospitalized children with sickle cell anemia

Background

Mineral bone disorders (MBD) are common in sickle cell anemia (SCA). Frequent vaso-occlusive crises (VOC) further impact MBD in children with SCA. We evaluated the prevalence of markers of SCA-related MBD (sMBD) in hospitalized children and assessed the relationship between sMBD and individual mineral abnormalities with kidney disease.

Methods

We prospectively recruited 185 children with SCA hospitalized with a VOC. Serum measures of mineral bone metabolism (calcium, phosphate, parathyroid hormone, 25-hydroxy vitamin D, FGF23, osteopontin) were measured at enrollment. The primary outcome was markers of sMBD defined as a composite of hypocalcemia, hyperphosphatemia, hyperparathyroidism, or deficiency in 25-OH vitamin D. Secondary outcomes included individual abnormalities in mineral metabolism. The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines were used to define SCA-associated acute kidney injury (AKI). AKI was further assessed using urine NGAL as a marker of tubular injury. Acute kidney disease (AKD) was defined as a composite of AKI, an eGFR < 90 ml/min per 1.73 m2 using the Cystatin C GFR equation, or evidence of structural injury (positive biomarker test or albuminuria).

Results

The mean age of children was 8.9 years and 41.6% were female. The prevalence of sMBD was 47.6%, with hypocalcemia the most frequent abnormality (29.9%, 55/184) followed by hyperphosphatemia (20.7%, 38/184), hyperparathyroidism (8.7%, 16/185), and vitamin D deficiency (5.4%, 10/185). There was no association between sMBD and sKDIGO-defined AKI using serial changes in creatinine or when incorporating biomarkers to define AKI. However, the presence of AKD was associated with a 2.01-fold increased odds of sMBD (95% CI 1.05 to 3.83) and was driven by a decrease in eGFR (OR, 2.90 95% CI: 1.59 to 5.29). When evaluating individual mineral abnormalities, hypocalcemia was associated with AKD and low eGFR while hyperparathyroidism was associated with low eGFR, AKI and structural injury. Vitamin D deficiency was associated with structural kidney injury. Vitamin D deficiency, hyperparathryoidism, and increases in FGF23 and osteopontin predicted mortality (p < 0.05 for all).

Conclusion

MBD is common among children with SCA hospitalized with VOC. Biomarkers of kidney injury and bone health may help risk stratify children at risk of sMBD. Routine evaluation of sMBD in children with SCA may improve long-term bone health.

The Molecular Mechanism and Therapeutic Strategy of Cardiorenal Syndrome Type 3

Cardiorenal syndrome type 3 (CRS3) is defined as acute kidney injury (AKI)-induced acute cardiac dysfunction, characterized by high morbidity and mortality. CRS3 often occurs in elderly patients with AKI who need intensive care. Approximately 70% of AKI patients develop into CRS3. CRS3 may also progress towards chronic kidney disease (CKD) and chronic cardiovascular disease (CVD). However, there is currently no effective treatment. Although the major intermediate factors that can mediate cardiac dysfunction remain elusive, recent studies have summarized the AKI biomarkers, identified direct mechanisms, including mitochondrial dysfunction, inflammation, oxidative stress, apoptosis and activation of the sympathetic nervous system (SNS) and renin-angiotensin-aldosterone system (RAAS), inflammasome, as well as indirect mechanisms such as fluid overload, electrolyte imbalances, acidemia and uremic toxins, which are involved in the pathophysiological changes of CRS3. This study reviews the main pathological characteristics, underlying molecular mechanisms, and potential therapeutic strategies of CRS3. Mitochondrial dysfunction and inflammatory factors have been identified as the key initiators and abnormal links between the impaired heart and kidney, which contribute to the formation of a vicious circle, ultimately accelerating the progression of CRS3. Therefore, targeting mitochondrial dysfunction, antioxidants, Klotho, melatonin, gene therapy, stem cells, exosomes, nanodrugs, intestinal microbiota and Traditional Chinese Medicine may serve as promising therapeutic approaches against CRS3.

Updates in the chronic kidney disease-mineral bone disorder show the role of osteocytic proteins, a potential mechanism of the bone-Vascular paradox, a therapeutic target, and a biomarker

The chronic kidney disease-mineral bone disorder (CKD-MBD) is a complex multi-component syndrome occurring during kidney disease and its progression. Here, we update progress in the components of the syndrome, and synthesize recent investigations, which suggest a potential mechanism of the bone-vascular paradox. The discovery that calcified arteries in chronic kidney disease inhibit bone remodeling lead to the identification of factors produced by the vasculature that inhibit the skeleton, thus providing a potential explanation for the bone-vascular paradox. Among the factors produced by calcifying arteries, sclerostin secretion is especially enlightening. Sclerostin is a potent inhibitor of bone remodeling and an osteocyte specific protein. Its production by the vasculature in chronic kidney disease identifies the key role of vascular cell osteoblastic/osteocytic transdifferentiation in vascular calcification and renal osteodystrophy. Subsequent studies showing that inhibition of sclerostin activity by a monoclonal antibody improved bone remodeling as expected, but stimulated vascular calcification, demonstrate that vascular sclerostin functions to brake the Wnt stimulation of the calcification milieu. Thus, the target of therapy in the chronic kidney disease-mineral bone disorder is not inhibition of sclerostin function, which would intensify vascular calcification. Rather, decreasing sclerostin production by decreasing the vascular osteoblastic/osteocytic transdifferentiation is the goal. This might decrease vascular calcification, decrease vascular stiffness, decrease cardiac hypertrophy, decrease sclerostin production, reduce serum sclerostin and improve skeletal remodeling. Thus, the therapeutic target of the chronic kidney disease-mineral bone disorder may be vascular osteoblastic transdifferentiation, and sclerostin levels may be a useful biomarker for the diagnosis of the chronic kidney disease-mineral bone disorder and the progress of its therapy.

Comprehensive single-cell transcriptional profiling defines shared and unique epithelial injury responses during kidney fibrosis

The underlying cellular events driving kidney fibrogenesis and metabolic dysfunction are incompletely understood. Here, we employed single-cell combinatorial indexing RNA sequencing to analyze 24 mouse kidneys from two fibrosis models. We profiled 309,666 cells in one experiment, representing 50 cell types/states encompassing epithelial, endothelial, immune, and stromal populations. Single-cell analysis identified diverse injury states of the proximal tubule, including two distinct early-phase populations with dysregulated lipid and amino acid metabolism, respectively. Lipid metabolism was defective in the chronic phase but was transiently activated in the very early stages of ischemia-induced injury, where we discovered increased lipid deposition and increased fatty acid β-oxidation. Perilipin 2 was identified as a surface marker of intracellular lipid droplets, and its knockdown in vitro disrupted cell energy state maintenance during lipid accumulation. Surveying epithelial cells across nephron segments identified shared and unique injury responses. Stromal cells exhibited high heterogeneity and contributed to fibrogenesis by epithelial-stromal crosstalk.

Total terpenoids of Inula japonica activated the Nrf2 receptor to alleviate the inflammation and oxidative stress in LPS-induced acute lung injury

BACKGROUND

Acute lung injury (ALI) is a life-threatening lung disease and characterized by pulmonary edema and atelectasis. Inula japonica Thunb. is a commonly used traditional Chinese medicine for the treatment of lung diseases. However, the potential effect and mechanism of total terpenoids of I. japonica (TTIJ) on ALI remain obscure.

PURPOSE

This study focused on the protective effect of TTIJ on lipopolysaccharide (LPS)-induced ALI in mice and its potential mechanism.

STUDY DESIGN AND METHODS

A mouse model of ALI was established by intratracheal instillation of LPS to investigate the protective effect of TTIJ. RNA-seq and bioinformatics were then performed to reveal the underlying mechanism. Finally, western blot and real-time qPCR were used to verify the effects of TTIJ on the inflammation and oxidative stress.

RESULTS

TTIJ notably attenuated LPS-induced histopathological changes of lung. The RNA-seq result suggested that the protective effect of TTIJ on LPS-induced ALI were associated with the Toll-like receptor 4 (TLR4) and nuclear factor-erythroid 2-related factor 2 (Nrf2) signaling pathways. Pretreatment with TTIJ significantly reduced the inflammation and oxidative stress via regulating levels of pro-inflammatory and anti-oxidative cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), superoxide dismutase (SOD), and glutathione (GSH), in LPS-induced ALI mice. TTIJ treatment could suppress the cyclooxygenase-2 (COX-2) expression level and the phosphorylation of p65, p38, ERK, and JNK through the inactivation of the MAPK/NF-κB signaling pathway in a TLR4-independent manner. Meanwhile, TTIJ treatment upregulated expression levels of proteins involved in the Nrf2 signaling pathway, such as heme oxygenase-1 (HO-1), NAD(P)H: quinoneoxidoreductase-1 (NQO-1), glutamate-cysteine ligase catalytic subunit (GCLC), and glutamate-cysteine ligase modifier subunit (GCLM), via activating the Nrf2 receptor, which was confirmed by the luciferase assay.

CONCLUSION

TTIJ could activate the Nrf2 receptor to alleviate the inflammatory response and oxidative stress in LPS-induced ALI mice, which suggested that TTIJ could serve as the potential agent in the treatment of ALI.