Oxalate Crystal Deposition Research Articles

Therapeutic Applications of Oxalate-degrading Bacteria in Kidney Stone Prevention

Urolithiasis is a condition where kidney stones exit through the renal pelvis, causing chronic pain. Kidney stones are usually formed due to the deposition of calcium and oxalate crystals. It is known to be a prevalent health condition that affects a large portion of the global human population. Inopportunely, no medications that show effective prevention of urolithiasis are currently available. Extensive research has highlighted the significant role of commensal microbes in regulating host oxalate homeostasis and oxalate-associated pathological conditions. However, limited knowledge of the pathophysiology of urolithiasis poses difficulties in designing target-based therapeutics. Growing evidence suggests the role of gut microbiota and probiotics in helping reduce the disease burden. Understanding the intricate relationship between gut-associated microbiota and its host symbiosis reveals the therapeutic potential of specific bacteria to prevent and/or treat such metabolic diseases. Oxalobacter formigenes, a bacterium, is considered crucial for degrading dietary oxalates through the oxalyl-CoA decarboxylase enzyme. The absence of this enzyme leads to hyperoxaluria and calcium oxalate urolithiasis, underscoring the impact of microbiota on kidney stone formation. Studies on the urinary microbiome, including those focusing on Oxalobacter formigenes, Lactobacillus, Bifidobacterium, Eubacterium lentum, Enterococcus faecalis, and Escherichia coli, elucidate the metabolism of dietary oxalates, providing a novel approach to kidney stone management. This review aims to consolidate the present information on the urinary microbiome, aetiology, pathogenesis, and disease prevention.

UHRF1 promotes calcium oxalate-induced renal fibrosis by renal lipid deposition via bridging AMPK dephosphorylation.

Nephrolithiasis, a common urinary system disorder, exhibits high morbidity and recurrence rates, correlating with renal dysfunction and the increased risk of chronic kidney disease. Nonetheless, the precise role of disrupted cellular metabolism in renal injury induced by calcium oxalate (CaOx) crystal deposition is unclear. The purpose of this study is to investigate the involvement of the ubiquitin-like protein containing PHD and RING finger structural domain 1 (UHRF1) in CaOx-induced renal fibrosis and its impacts on cellular lipid metabolism. Various approaches, including snRNA-seq, transcriptome RNA-seq, immunohistochemistry, and western blot analyses, were employed to assess UHRF1 expression in kidneys of nephrolithiasis patients, hyperoxaluric mice, and CaOx-induced renal tubular epithelial cells. Subsequently, knockdown of UHRF1 in mice and cells corroborated its effect of UHRF1 on fibrosis, ectopic lipid deposition (ELD) and fatty acid oxidation (FAO). Rescue experiments using AICAR, ND-630 and Compound-C were performed in UHRF1-knockdown cells to explore the involvement of the AMPK pathway. Then we confirmed the bridging molecule and its regulatory pathway in vitro. Experimental results were finally confirmed using AICAR and chemically modified si-UHRF1 in vivo of hyperoxaluria mice model. Mechanistically, UHRF1 was found to hinder the activation of the AMPK/ACC1 pathway during CaOx-induced renal fibrosis, which was mitigated by employing AICAR, an AMPK agonist. As a nuclear protein, UHRF1 facilitates nuclear translocation of AMPK and act as a molecular link targeting the protein phosphatase PP2A to dephosphorylate AMPK and inhibit its activity. This study revealed that UHRF1 promotes CaOx -induced renal fibrosis by enhancing lipid accumulation and suppressing FAO via inhibiting the AMPK pathway. These findings underscore the feasible therapeutic implications of targeting UHRF1 to prevent renal fibrosis due to stones.

Sulfated Undaria pinnatifida polysaccharides inhibit kidney stone formation through crystalline modulation and relieving cellular oxidative damage and inflammation

Abstracts: Background: Calcium oxalate (CaOx) crystal deposition and its resultant cellular oxidative damage and inflammation are important causes of renal stone formation. It is clinically important to conduct research on...

A mouse model for the study of diet-induced changes in intestinal microbiome composition on renal calcium oxalate crystal formation.

Currently available animal models for calcium oxalate kidney stones are limited in their translational potential. Particularly with increasing interest in gut microbiota involvement in kidney stone disease, there are limited animal models which can be used. As such, we have developed a novel diet-induced hyperoxaluria murine model which addresses some of the shortcomings of other currently available models. Mice C57BL/6 mice were fed a 1.5% sodium oxalate supplemented chow for two weeks and showed no morbidity or mortality. Mice fed the sodium oxalate diet consistently had renal calcium oxalate crystal deposits as confirmed by polarized light microscopy, and energy-dispersive X-ray spectroscopy. We developed a isotope dilution high-performance liquid chromatography/mass spectrometry protocol which confirmed that our model produced both urinary and enteric hyperoxaluria. 16S ribosomal RNA sequencing of stool samples and cecal contents showed that sodium oxalate is a disruptor of the gut microbiome, and may interfere with commensal microbes in the gut microbiome. With consistent results this mouse model is superior to other models of kidney stone disease, as this model can be applied to investigate topics of oxalate absorption, transport, metabolism, excretion, crystal formation, the gut microbiome and testing of various therapeutic agents for translation to early stages of renal crystal formation in kidney stone disease.

Based on network pharmacology, the mechanism of Dioscin in alleviating renal tubular epithelial cell injury induced by calcium oxalate crystals was explored.

The commencement of kidney stone formation involves a crucial initial phase characterized by injury to renal tubular cells caused by calcium oxalate (CaOx). Dioscin (Dio) has been acknowledged for its potent anti-inflammation and anti-apoptotic properties; nevertheless, the impact and underlying Investigation into the molecular basis underlying the action of Dioscin in mitigating inflammation and apoptotic induced by exposure to calcium oxalate crystals in renal tissues remain unexplored.To comprehend the precise mechanism of Dioscin in the treatment of crystalline nephropathy, we conducted experiments utilizing a murine model of CaOx crystal deposition, induced by intraperitoneal administration of glyoxylate. An in vitro model was constructed using HK-2 cells exposed to calcium oxalate monohydrate (COM). To evaluate the effect of Dioscin on calcium oxalate crystal deposition by ROS assay, Western blotting, immunohistochemistry, Periodic Acid-Schiff staining (PAS) staining, hematoxylin-eosin (H&E) staining. Using network pharmacology and molecular docking methods, we explored the molecular mechanism of Dioscin in the treatment of CaOx-induced renal tubular epithelial cell injury. Subsequently, we conducted experiments to verify our findings.We observed a significant protective effect of Dioscin treatment against kidney oxidative stress and inflammation induced by CaOx. Then we predicted through network pharmacology that Dioscin exerts its anti-apoptotic effect through the NF-kappa B signaling pathway. Then we verified in vitro and in vivo that administration of Dioscin can alleviate the elevation of TLR4 and activation of the NF-kappa B signaling pathway induced by calcium oxalate, as well as attenuate renal apoptosis. Instead, the beneficial impact of this protection of Dioscin was reversed after overexpression of the TLR4.Dioscin has the potential to alleviate the activation of the NF-kappa B signaling pathway through TLR4, thereby exerting anti-inflammatory and anti-apoptotic effects. This study provides new ideas for the prevention and treatment of kidney stones.

Bidirectional Impact of Varying Severity of Acute Kidney Injury on Calcium Oxalate Stone Formation

Introduction: Acute kidney injury (AKI) is a prevalent renal disorder. The occurrence of AKI may promote the formation of renal calcium oxalate stones by exerting continuous effects on renal tubular epithelial cells (TECs). We aimed to delineate the molecular interplay between AKI and nephrolithiasis. Methods: A mild (20 min) and severe (30 min) renal ischemia-reperfusion injury model was established in mice. Seven days after injury, calcium oxalate stones were induced using glyoxylate (Gly) to evaluate the impact of AKI on the formation of kidney stones. Transcriptome sequencing was performed on TECs to elucidate the relationship between AKI severity and kidney stones. Key transcription factors (TFs) regulating differential gene transcription levels were identified using motif analysis, and pioglitazone, ginkgetin, and fludarabine were used for targeted therapy to validate key TFs as potential targets for kidney stone treatment. Results: Severe AKI led to increased deposition of calcium oxalate crystals in renal, impaired kidney function, and upregulation of kidney stone-related gene expression. In contrast, mild AKI was associated with decreased crystal deposition, preserved kidney function, and downregulation of similar gene expression. Transcriptomic analysis revealed that genes associated with inflammation and cell adhesion pathways were significantly upregulated after severe AKI, while genes related to energy metabolism pathways were significantly upregulated after mild AKI. An integrative bioinformatic analysis uncovered a TF regulatory network within TECs, pinpointing that PKNOX1 was involved in the upregulation of inflammation-related genes after severe AKI, and inhibiting PKNOX1 function with pioglitazone could simultaneously reduce the increase of calcium oxalate crystals after severe AKI in kidney. On the other hand, motif analysis also revealed the protective role of STAT1 in the kidneys after mild AKI, enhancing the function of STAT1 with ginkgetin could reduce kidney stone formation, while the specific inhibitor of STAT1, fludarabine, could eliminate the therapeutic effects of mild AKI on kidney stones. Conclusion: Inadequate repair of TECs after severe AKI increases the risk of kidney stone formation, with the upregulation of inflammation-related genes regulated by PKNOX1 playing a role in this process. Inhibiting PKNOX1 function can reduce kidney stone formation. Conversely, after mild AKI, effective cell repair through upregulation of STAT1 expression can protect TEC function and reduce stone formation, and activating STAT1 function can also achieve the goal of treating kidney stones.

NINJ1-mediated Macrophage Plasma Membrane Rupture and Neutrophil Extracellular Trap Formation Contribute to Oxalate Nephropathy.

Oxalate nephropathy is characterized by calcium oxalate crystals deposition, which triggers necrosis of renal tubular epithelial cells, initiates an inflammatory cascade characterized by neutrophil and macrophage activation within the renal microenvironment. Despite the close association of immune cells with acute oxalate nephropathy, the underlying mechanisms still remain unclear. Nerve injury-induced protein 1 (NINJ1) plays an essential role in the induction of plasma membrane rupture (PMR), leading to damage-associated molecular patterns (DAMPs) release and triggering inflammation. We hypothesize that NINJ1-mediated high mobility group box 1 (HMGB1) release from macrophage PMR and neutrophil extracellular traps (NETs) formation synergistically contribute to the progression of acute oxalate nephropathy. Using a murine model of acute oxalate nephropathy, myeloid cell-specific deletion of Ninj1 mice (Ninj1fl/flvavcre) and their wild-type littermate control mice (Ninj1wt/wtvavcre) were administered intraperitoneal injection of 100 mg/kg sodium oxalate followed by drinking water with 3% sodium oxalate. Evaluation was conducted on tubular injury and inflammatory cell infiltration. In vitro studies involved isolation and culture of renal proximal tubular epithelial cells (RTECs), bone marrow-derived macrophages, and neutrophils to investigate NETs formation and HMGB1 release. Targeted deletion of Ninj1 in myeloid cells significantly mitigated oxalate-induced acute kidney injury by suppressing both HMGB1 release and NETs formation in vivo. In vitro investigations demonstrated that HMGB1 release from macrophage PMR and NETs formation in neutrophils mediated by NINJ1 oligomerization, which consequently coordinated to enhance renal tubular epithelial cell death. Our findings elucidate the pivotal role of NINJ1-dependent macrophage PMR and NETs formation in the progression of acute oxalate nephropathy, providing novel insights for its prevention and therapeutic targets.

Role of Z-DNA Binding Protein 1 Sensing Mitochondrial Z-DNA and Triggering Necroptosis in Oxalate-Induced Acute Kidney Injury.

Calcium oxalate-induced acute kidney injury is a severe condition in which the kidneys suffer rapid damage due to the deposition of oxalate crystals. Known factors contributing to cell death induced by calcium oxalate include receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) protein dependent necroptosis, as well as necrosis involving peptidylprolyl isomerase F (PPIF) mediated mitochondrial permeability transition. However, the detailed molecular mechanisms linking mitochondrial dysfunction to RIPK3 activation are not fully understood. Mice with gene knock-out of Zbp1, Ripk3, or Mlkl and mice with mutations in the Z-nucleic acid sensing domain of ZBP1 or deletion of Zα1 were used in an oxalate-induced AKI model. Proximal renal tubule cells were isolated and cultured for further investigation. Human oxalate nephropathy biopsy samples were analyzed. Specific gene deletions of Zbp1, Ripk3, or Mlkl in proximal renal tubules significantly reduced the severity of oxalate-induced AKI by preventing necroptosis and subsequent inflammation. Notably, mice with mutations in the Z-nucleic acid sensing domain of ZBP1 or deletion of Zα1 were protected from AKI. In cultured proximal tubular cells, calcium oxalate damaged mitochondria, accompanied by an increase in Bax and a decrease in BCL2 and TAFM, leading to the release of mitochondrial Z-DNA. ZBP1 sensed this mitochondrial Z-DNA and then recruited RIPK3 via the RIP homotypic interaction motifs (RHIM), which in turn activated MLKL through RIPK3 phosphorylation, leading to necroptosis and contributing to AKI. ZBP1 plays a critical role in sensing mitochondrial Z-DNA and initiating RIPK3/MLKL-mediated necroptosis, contributing to the development of oxalate-induced AKI.

Efficient and safe in vivo treatment of primary hyperoxaluria type 1 via LNP-CRISPR-Cas9-mediated glycolate oxidase disruption

Primary hyperoxaluria type 1 (PH1) is a severe genetic metabolic disorder caused by mutations in the AGXT gene, leading to defects in enzymes crucial for glyoxylate metabolism. PH1 is characterized by severe, potentially life-threatening manifestations due to excessive oxalate accumulation, which leads to calcium oxalate crystal deposits in the kidneys and, ultimately, renal failure and systemic oxalosis. Existing substrate reduction therapies, such as inhibition of liver-specific glycolate oxidase (GO) encoded by HAO1 using siRNA or CRISPR/Cas9 delivered by adeno-associated virus (AAV), either require repeated dosing or have raised safety concerns. To address these limitations, our study employed lipid nanoparticles (LNPs) for CRISPR/Cas9 delivery to rapidly generate a PH1 mouse model and validate the therapeutic efficacy of LNP-CRISPR/Cas9 targeting the Hao1 gene. The LNP-CRISPR/Cas9 system exhibited efficient editing of the Hao1 gene, significantly reducing GO expression and lowering urinary oxalate levels in treated PH1 mice. Notably, these effects persisted for 12 months with no significant off-target effects, liver-induced toxicity, or substantial immune responses, highlighting the approach's safety and specificity. Furthermore, the developed humanized mouse model validated the efficacy of our therapeutic strategy. These findings support LNP-CRISPR/Cas9 targeting HAO1 as a promising and safer alternative for PH1 treatment with a single administration.

Puerarin alleviates apoptosis and inflammation in kidney stone cells via the PI3K/AKT pathway: Network pharmacology and experimental verification.

Puerarin(PUE), an isoflavonoid extracted from Pueraria root, has anti-apoptotic effects. The objective of this research is to examine the impact of PUE on renal apoptosis and inflammation resulting from renal calculi and to elucidate its mechanism. The approach of network pharmacology and molecular docking was employed to discover potential targets and pathways of PUE. An animal model of calcium oxalate crystal deposition by intraperitoneal injection of glyoxylate and a model of COM-induced human renal tubular epithelial cells (HK2) were used to investigate the pharmacological mechanisms of PUE against apoptosis and inflammation. We used haematoxylin-eosin (H&E) and Periodic Acid-Schiff staining (PAS) to assess the effect of PUE on crystal deposition and damage. The mechanism of PUE was elucidated and validated using Western blotting, histology and immunohistochemical staining. Network pharmacology findings indicated that the PI3K/AKT pathway plays a crucial role in PUE. We experimentally demonstrate that PUE alleviated COM-induced changes in apoptotic proteins, increased inflammatory indicators and changes in oxidative stress-related indicators in HK2 cells by activating the PI3K/AKT pathway, reduced serum creatinine and urea nitrogen levels in mice caused by CaOx, alleviated crystal deposition and damage, and alleviated apoptosis, oxidative stress and inflammation. Puerarin attenuates renal apoptosis and inflammation caused by kidney stones through the PI3K/AKT pathway.

Isovaleramide attenuates ethylene glycol poisoning-induced acute kidney injury and reduces mortality by inhibiting alcohol dehydrogenase activity in rats.

We explored the potential value of the alcohol dehydrogenase (ADH) inhibitor isovaleramide (ISO) in the treatment of acute ethylene glycol (EG) poisoning-induced acute kidney injury. Sprague-Dawley rats were divided into the control, EG, EG + ISO (10mg/kg) and EG + ISO (20 mg/kg) groups. It is found that ISO intervention significantly reduced the ADH activity in liver tissue by using visible spectrophotometry, inhibited the in vivo metabolism of EG by using gas chromatography, lowered the levels of toxic metabolites glycolic acid and oxalic acid by using high-performance liquid chromatography and decreased the expression of kidney injury markers serum creatinine (sCr), KIM-1, neutrophil gelatinase-associated lipocalin (NGAL) and liver fatty acid-binding protein (L-FABP) by ELISA. Additionally, Western blotting results showed that ISO down-regulated the expression of apoptotic factors Bax and cleaved caspase-3 in the kidneys and upregulated the expression of antiapoptotic factor Bcl-2. Pizzolato staining and polarized light microscopy results revealed the reduced deposition of calcium oxalate crystals in the kidney tubules. Using haematoxylin and eosin (H&E), periodic acid-Schiff (PAS) and Masson staining, we found attenuated kidney tissue pathological injury. Finally, ISO significantly reduced the mortality rate. In conclusion, ISO has the potential to be a valuable drug for the treatment of EG poisoning-induced acute kidney injury.

MOF-818 Nanozyme Suppresses Calcium Oxalate Kidney Stones by Alleviating Oxidative Stress and Inflammatory Injury.

There remains a lack of effective drugs to alleviate the kidney stones caused by oxidative stress and inflammatory damage. The MOF-818 nanozyme is utilized to lessen the generation of reactive oxygen species (ROS) effectively, restore the membrane potential of mitochondria, regulate the cell cycle, decrease cell death, hinder the recruitment of macrophages, and mitigate the release of inflammatory factors in macrophages. These effects are attributed to the nanozyme's ability to mimic the enzyme properties of catalase (CAT) and superoxide dismutase (SOD). It is demonstrated that this nanozyme can reduce kidney calcium oxalate crystal deposition by reducing the renal injury caused by high concentration oxalate, upregulate the expression levels of SOD and CAT in tissues, downregulate adhesion proteins and inflammatory factor IL-6 and TNF-α, and promote the polarization of macrophages from M1 to M2 phenotype in the rat model induced by ethylene glycol. Overall, MOF-818 has the potential to effectively suppress oxidative stress and inflammatory harm caused by high levels of oxalate, hence lowering the likelihood of stone formation. MOF-818 nanozyme is also expected to be used as an alternative drug for the treatment of calcium oxalate kidney stones and provide an experimental theoretical basis for the development of new nanomedicines.

Mitochondrial dysfunction in kidney stones and relief of kidney stones after reducing mtROS.

Mitochondria are essential organelles because they generate the energy required for cellular functions. Kidney stones, as one of the most common urological diseases, have garnered significant attention. In this study, we first collected peripheral venous blood from patients with kidney stones and used qRT-PCR to detect mitochondrial DNA (mtDNA) copy number as a means of assessing mitochondrial function in these patients. Subsequently, through Western blotting, qPCR, immunofluorescence, immunohistochemistry, and transmission electron microscopy, we examined whether calcium oxalate crystals could cause mitochondrial dysfunction in the kidney in both in vitro and in vivo. We then examined the intersection of the DEGs obtained by transcriptome sequencing of the mouse kidney stone model with mitochondria-related genes, and performed KEGG and GO analyses on the intersecting genes. Finally, we administered the mitochondrial ROS scavenger Mito-Tempo in vivo and observed its effects. Our findings revealed that patients with kidney stones had a reduced mtDNA copy number in their peripheral venous blood compared to the control group, suggesting mitochondrial dysfunction in this population. This conclusion was further validated through in vitro and in vivo experiments. Enrichment analyses revealed that the intersecting genes were closely related to metabolism. We observed that after mitochondrial function was preserved, the deposition of calcium oxalate crystals decreased, and the kidney damage and inflammation caused by them were also alleviated. Our research indicates that kidney stones can cause mitochondrial dysfunction. After clearing mtROS, the damage and inflammation caused by kidney stones are reversed, providing new insights into the prevention and treatment of kidney stones.

Clinical manifestations and renal pathology of ethylene glycol.

Ethylene glycol (EG) poisoning is a critical medical emergency often associated with suicide attempts in adults. EG is metabolized by alcohol dehydrogenase, leading to the formation of toxic metabolites that cause metabolic acidosis, renal failure, hypocalcemia, aciduria, and disorders of the central nervous and cardiovascular systems. Calcium oxalate, a metabolite of EG, contributes to acute tubular necrosis. Despite limited reports on human renal pathology, we present a case detailing renal pathology following EG ingestion. A 44-year-old male, admitted due to loss of consciousness, had ingested a lethal dose of EG. Blood tests indicated metabolic acidosis, while urinary examination revealed calcium oxalate crystals. Continuous renal replacement therapy corrected the acidosis; however, nephrogenic diabetes insipidus subsequently developed. A renal biopsy on day 31 revealed calcium oxalate crystal deposition and tubulointerstitial damage. Notably, various stages of crystal deposition, adherence, and degradation were observed. This case underscores the importance of considering EG poisoning in cases of unexplained metabolic acidosis and renal dysfunction, with renal biopsy serving as a valuable diagnostic tool. Understanding the renal effects of EG is essential for timely intervention and effective management of poisoning cases.

Severe acute kidney injury due to oxalate crystal induced severe interstitial nephritis: A case report

BACKGROUND Acute kidney injury (AKI) due to interstitial nephritis is a known condition primarily attributed to various medications. While medication-induced interstitial nephritis is common, occurrences due to non-pharmacological factors are rare. This report presents a case of severe AKI triggered by intratubular oxalate crystal deposition, leading to interstitial nephritis. The aim is to outline the case and its management, emphasizing the significance of recognizing uncommon causes of interstitial nephritis. CASE SUMMARY A 71-year-old female presented with stroke-like symptoms, including weakness, speech difficulties, and cognitive impairment. Chronic hypertension had been managed with hydrochlorothiazide (HCTZ) for over two decades. Upon admission, severe hypokalemia and AKI were noted, prompting discontinuation of HCTZ and initiation of prednisolone for acute interstitial nephritis. Further investigations, including kidney biopsy, confirmed severe acute interstitial nephritis with oxalate crystal deposits as the underlying cause. Despite treatment, initial renal function showed minimal improvement. However, with prednisolone therapy and supportive measures, her condition gradually improved, highlighting the importance of comprehensive management. CONCLUSION This case underscores the importance of a thorough diagnostic approach in identifying and addressing uncommon causes of interstitial nephritis. The occurrence of interstitial nephritis due to oxalate crystal deposition, especially without typical risk factors, emphasizes the need for vigilance in clinical practice.

#1846 Oxalate nephropathy in diabetic kidney disease: another factor to take into account?

Abstract Background and Aims Patients with diabetes mellitus (DM) have an increased urinary excretion of oxalate. Around 40% of patients with oxalate nephropathy have DM. The aim of this study was to describe the prevalence of tubular deposits of calcium oxalate (CaOx) crystals in patients with diabetic kidney disease (DKD) and investigate its association with renal survival. Method We performed an observational retrospective study that included patients with DKD in renal biopsies performed at our centre between January 1999 and December 2021. We revised the biopsy specimens for the presence of intratubular CaOx crystals. We excluded patients with a histological findings of non-diabetic kidney disease and those lost to follow-up. Renal survival was defined as a state free from developing end-stage kidney disease (ESKD) requiring renal replacement therapy. Results The study included 87 patients with a mean age of 63.1 ± 13 years, 73.5% were male, and 88.5% had type 2 DM (11.5% type 1 DM). Baseline GFR at the moment of kidney biopsy was 38.5 ± 23 ml/min, and baseline median proteinuria was 3.46 (1.35-5.70) g/day. We found intratubular CaOx deposits in 11 biopsies (12.6%). These findings were only found in patients with type 2 DM (14.3% vs 0%), and was more frequently present in patients with a history of renal stones (33.3% vs 11.1%). There were no differences in baseline GFR, proteinuria or vintage of DM between patients with intratubular CaOx deposits and those with no signs of oxalte nephropathy. CaOx deposition was not associated with other histological lesions such as percentage of glomerular sclerosis, grade of interstitial fibrosis and/or tubular atrophy, interstitial inflammation, arterial hyalinosis or arteriosclerosis. After a median follow-up of 41 months, 49.4% of patients developed ESKD while 26.4% died without progressing to ESKD. The patients who progressed to ESKD had a higher baseline serum creatinine (2.56 ± 1.45 vs 1.98 ± 1.07 ml/min, p = 0.037) and lower serum albumin (3.08 ± 0.70 vs 3.57 ± 0.74 g/dl, p = 0.003). In the regression analysis there was no association between intratubular CaOx deposits and progression to ESKD (OR = 2.96, 95% CI 0.73-12.03). In the adjusted model, no histological lesions were associated with renal survival. In the survival analysis, the presence of intratubular CaOx deposits was not associated with neither renal nor patient survival. Conclusion Oxalate nephropathy, defined as the presence of intratubular CaOx deposits in kidney biopsies, may be found in patients with DKD. In our cohort, 14.3% of type 2 DM patients with DKD had concomitant oxalate nephropathy. Its presence was not associated with a worse renal or patient survival.

Porous Se@SiO2 nanocomposites play a potential inhibition role in hyperoxaluria associated kidney stone by exerting antioxidant effects.

Nephrolithiasis seriously affects people's health with increasing prevalence and high recurrence rates. However, there is still a lack of effective interventions for the clinical prevention of kidney stones. Hyperoxaluria-induced renal tubular epithelial cell (TEC) injury is a known key factor in kidney stone formation. Thus, developing new drugs to inhibit the hyperoxaluria-induced TEC injury may be the best way. We synthesized the Se@SiO2 nanocomposites as described in Zhu's study. The size and morphology of the Se@SiO2 nanocomposites were captured by transmission electron microscopy. Cell viability was measured by a Cell Counting Kit-8 (CCK-8) assay. The mice were randomly divided into the following four groups: (I) the control group (n=6); (II) the Se@SiO2 group (n=6); (III) the glyoxylic acid monohydrate (GAM) group; and (IV) the GAM + Se@SiO2 group (n=6). The concentration of Se in the mice was quantified using inductively coupled plasma atomic emission spectroscopy. The CCK-8 assays showed that Se@SiO2 nanocomposites had almost no obvious cytotoxicity on the Transformed C3H Mouse Kidney-1 (TCMK-1) cell. The mice kidney Se concentration levels in the Se@SiO2 groups (Se@SiO2 6.905±0.074 mg/kg; GAM + Se@SiO2 7.673±2.85 mg/kg) (n=6) were significantly higher than those in the control group (Control 0.727±0.072 mg/kg; GAM 0.747±0.074 mg/kg) (n=6). The Se@SiO2 nanocomposites reduced kidney injury, calcium oxalate crystal deposition, and the osteoblastic-associated proteins in the hyperoxaluria mice models. Se@SiO2 nanocomposites appear to protect renal TECs from hyperoxaluria by reducing reactive oxygen species production, suggesting the potential role of preventing kidney stone formation and recurrence.

Determinants and impact of calcium oxalate crystal deposition on renal outcomes in acute kidney injury patients

Objectives Calcium oxalate (CaOx) crystal deposition in acute kidney injury (AKI) patients is under recognized but impacts renal outcomes. This study investigates its determinants and effects. Methods We studied 814 AKI patients with native kidney biopsies from 2011 to 2020, identifying CaOx crystal deposition severity (mild: <5, moderate: 5–10, severe: >10 crystals per section). We assessed factors like urinary oxalate, citrate, urate, electrolytes, pH, tubular calcification index, and SLC26A6 expression, comparing them with creatinine-matched AKI controls without oxalosis. We analyzed how these factors relate to CaOx severity and their impact on renal recovery (eGFR < 15 mL/min/1.73 m2 at 3-month follow-up). Results CaOx crystal deposition was found in 3.9% of the AKI cohort (32 cases), with 72% due to nephrotoxic medication-induced tubulointerstitial nephritis. Diuretic use, higher urinary oxalate-to-citrate ratio induced by hypocitraturia, and tubular calcification index were significant contributors to moderate and/or severe CaOx deposition. Poor baseline renal function, low urinary chloride, high uric acid and urea nitrogen, tubular SLC26A6 overexpression, and glomerular sclerosis were also associated with moderate-to-severe CaOx deposition. Kidney recovery was delayed, with 43.8%, 31.2%, and 18.8% of patients having eGFR < 15 mL/min/1.73 m2 at 4, 12, and 24-week post-injury. Poor outcomes were linked to high urinary α1-microglobulin-to-creatinine (α1-MG/C) ratios and active tubular injury scores. Univariate analysis showed a strong link between this ratio and poor renal outcomes, independent of oxalosis severity. Conclusions In AKI, CaOx deposition is common despite declining GFR. Factors worsening tubular injury, not just oxalate-to-citrate ratios, are key to understanding impaired renal recovery.

In vivo base editing rescues primary hyperoxaluria type 1 in rats

Primary hyperoxaluria type 1 (PH1) is a childhood-onset autosomal recessive disease, characterized by nephrocalcinosis, multiple recurrent urinary calcium oxalate stones, and a high risk of progressive kidney damage. PH1 is caused by inherent genetic defects of the alanine glyoxylate aminotransferase (AGXT) gene. The invivo repair of disease-causing genes was exceedingly inefficient before the invention of base editors which can efficiently introduce precisely targeted base alterations without double-strand DNA breaks. Adenine base editor (ABE) can precisely convert A·T to G·C with the assistance of specific guide RNA. Here, we demonstrated that systemic delivery of dual adeno-associated virus encoding a split-ABE8e could artificially repair 13% of the pathogenic allele in AgxtQ84X rats, a model of PH1, alleviating the disease phenotype. Specifically, ABE treatment partially restored the expression of alanine-glyoxylate-aminotransferase (AGT), reduced endogenous oxalate synthesis and alleviated calcium oxalate crystal deposition. Western blot and immunohistochemistry confirmed that ABE8e treatment restored AGT protein expression in hepatocytes. Moreover, the precise editing efficiency in the liver remained stable six months after treatment. Thus, our findings provided a prospect of invivo base editing as a personalized and precise medicine for PH1 by directly correcting the mutant Agxt gene.

The Clinical and Pathological Characteristics of Patients with Oxalate Nephropathy.

Key PointsOxalate nephropathy is an underrecognized cause of CKD and ESKDWe present one of the largest native oxalate nephropathy cohorts to date from a tertiary care institution in the United StatesOxalate nephropathy has multiple etiologies and given its clinical course and poor prognosis, attention must be paid to screening for risk factors to guide prompt diagnosis and managementBackgroundOxalate nephropathy (ON) is characterized by deposition of calcium oxalate crystals in the kidney and is commonly under-recognized. Causes of ON include primary hyperoxaluria, enteric hyperoxaluria, and ingestion of excess oxalate or its precursors.MethodsWe report the clinical and pathological characteristics of one of the largest series of native kidney ON to date, from January 2015 to March 2023 at the Cleveland Clinic.ResultsWe identified 60 native biopsies with oxalate deposits and excluded patients with clinically insignificant biopsies (n=12) or lack of data (n=17). Thirty-one patients with native ON were described. The mean age at diagnosis was 66.2 years (±12.1), and 58.1% were female. 87.1% had hypertension, 58.1% had diabetes, 42% had nephrolithiasis, and 77.4% had underlying CKD, with a mean baseline creatinine of 1.8 mg/dl ±1.3.The mean creatinine at biopsy was 5.2 mg/dl ±1.7. Kidney biopsies showed abundant calcium oxalate crystal deposits, and 27 of 31 biopsies had additional diagnoses, the most common of which were acute tubular injuryn=17 (54.8%) and diabetic glomerulosclerosisn=7 (22.6%). Severe and moderate interstitial fibrosis was present in 38.7% (n=12) and 51.6% (n=16) of biopsies, respectively. Ten had a single etiology of ON, ten had a multifactorial etiology (both enteric hyperoxaluria and high precursor intake), and 11 had an unclear etiology. Notably, only seven patients had a history of gastric bypass.The mean duration of follow-up was 26.8 months, and 26 patients had follow-up data &gt;1 year. Of these, 21 required dialysis, and five were dialysis-free at presentation. Five of the 26 were deceased at 1 year, with 12 patients (38.7%) deceased at last follow-up. Seventeen patients received targeted management, while nine patients did not receive targeted treatment, and all nine required hemodialysis. More patients (31.6%) had vitamin C intake after the coronavirus disease 2019 pandemic (2020–2023) versus 16.7% before 2020.ConclusionsON presents as AKI or acute on CKD. The prognosis is poor with most patients requiring dialysis at presentation with high morbidity and mortality. Clinicians need to be aware of the risk factors associated with ON to aid prompt diagnosis and management.PodcastThis article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/K360/2024_01_26_KID0000000000000340.mp3