X-Linked Hereditary Nephropathy in Navasota Dogs: Clinical Pathology, Morphology, and Gene Expression During Disease Progression

Bayesian mixed model analysis uncovered 21 risk loci for chronic kidney disease in boxer dogs

Chronic kidney disease (CKD) affects 10% of the human population, with only a small fraction genetically defined. CKD is also common in dogs and has been diagnosed in nearly all breeds, but its genetic basis remains unclear. Here, we performed a Bayesian mixed model genome-wide association analysis for canine CKD in a boxer population of 117 canine cases and 137 controls, and identified 21 genetic regions associated with the disease. At the top markers from each CKD region, the cases carried an average of 20.2 risk alleles, significantly higher than controls (15.6 risk alleles). An ANOVA test showed that the 21 CKD regions together explained 57% of CKD phenotypic variation in the population. Based on whole genome sequencing data of 20 boxers, we identified 5,206 variants in LD with the top 50 BayesR markers. Following comparative analysis with human regulatory data, 17 putative regulatory variants were identified and tested with electrophoretic mobility shift assays. In total four variants, three intronic variants from the MAGI2 and GALNT18 genes, and one variant in an intergenic region on chr28, showed alternative binding ability for the risk and protective alleles in kidney cell lines. Many genes from the 21 CKD regions, RELN, MAGI2, FGFR2 and others, have been implicated in human kidney development or disease. The results from this study provide new information that may enlighten the etiology of CKD in both dogs and humans.

Potential Renal Damage Biomarkers in Alport Syndrome—A Review of the Literature

Alport syndrome (AS) is the second most common cause of inherited chronic kidney disease. This disorder is caused by genetic variants on COL4A3, COL4A4 and COL4A5 genes. These genes encode the proteins that constitute collagen type IV of the glomerular basement membrane (GBM). The heterodimer COL4A3A4A5 constitutes the majority of the GBM, and it is essential for the normal function of the glomerular filtration barrier (GFB). Alterations in any of collagen type IV constituents cause disruption of the GMB structure, allowing leakage of red blood cells and albumin into the urine, and compromise the architecture of the GFB, inducing inflammation and fibrosis, thus resulting in kidney damage and loss of renal function. The advances in DNA sequencing technologies, such as next-generation sequencing, allow an accurate diagnose of AS. Due to the important risk of the development of progressive kidney disease in AS patients, which can be delayed or possibly prevented by timely initiation of therapy, an early diagnosis of this condition is mandatory. Conventional biomarkers such as albuminuria and serum creatinine increase relatively late in AS. A panel of biomarkers that might detect early renal damage, monitor therapy, and reflect the prognosis would have special interest in clinical practice. The aim of this systematic review is to summarize the biomarkers of renal damage in AS as described in the literature. We found that urinary Podocin and Vascular Endothelial Growth Factor A are important markers of podocyte injury. Urinary Epidermal Growth Factor has been related to tubular damage, interstitial fibrosis and rapid progression of the disease. Inflammatory markers such as Transforming Growth Factor Beta 1, High Motility Group Box 1 and Urinary Monocyte Chemoattractant Protein- 1 are also increased in AS and indicate a higher risk of kidney disease progression. Studies suggest that miRNA-21 is elevated when renal damage occurs. Novel techniques, such as proteomics and microRNAs, are promising.

Small RNA sequencing evaluation of renal microRNA biomarkers in dogs with X-linked hereditary nephropathy

Dogs with X-linked hereditary nephropathy (XLHN) are an animal model for Alport syndrome in humans and progressive chronic kidney disease (CKD). Using mRNA sequencing (mRNA-seq), we have characterized the gene expression profile affecting the progression of XLHN; however, the microRNA (miRNA, miR) expression remains unknown. With small RNA-seq and quantitative RT-PCR (qRT-PCR), we used 3 small RNA-seq analysis tools (QIAGEN OmicSoft Studio, miRDeep2, and CPSS 2.0) to profile differentially expressed renal miRNAs, top-ranked miRNA target genes, and enriched biological processes and pathways in CKD progression. Twenty-three kidney biopsies were collected from 5 dogs with XLHN and 4 age-matched, unaffected littermates at 3 clinical time points (T1: onset of proteinuria, T2: onset of azotemia, and T3: advanced azotemia). We identified up to 23 differentially expressed miRNAs at each clinical time point. Five miRNAs (miR-21, miR-146b, miR-802, miR-142, miR-147) were consistently upregulated in affected dogs. We identified miR-186 and miR-26b as effective reference miRNAs for qRT-PCR. This study applied small RNA-seq to identify differentially expressed miRNAs that might regulate critical pathways contributing to CKD progression in dogs with XLHN.

Clinical and Histopathological Features of Renal Maldevelopment in Boxer Dogs: A Retrospective Case Series (1999-2018)

Simple Summary

This study describes clinical findings in Boxer dogs with renal maldevelopment and proposes a possible mode of inheritance. Medical records of 9 female Boxer dogs, older than 5 months and with a clinical diagnosis of proteinuric chronic kidney disease prior to one year of age, showed the presence of polyuria and polydipsia, decreased appetite, weight loss, lethargy and weakness in all affected dogs. Common laboratory findings were proteinuria and diluted urine, non-regenerative anemia, azotemia, hyperphosphatemia, hypoalbuminemia and hypercholesterolemia. Histopathology of the kidneys identified the presence of immature glomeruli in all dogs. In 7 out of 9 related dogs, the pedigree analysis showed that a simple autosomal recessive trait may be a possible mode of inheritance. Renal glomerular immaturity should be suspected in Boxer dogs with a history of polyuria, polydipsia, decreased appetite, weight loss, lethargy, weakness and proteinuria. A prompt diagnosis of renal maldevelopment, potentially hereditary, may help to evaluate if relatives of the affected dogs might be at risk, thus assisting clinicians in reaching an early diagnosis. A routine clinical renal screening evaluation in this breed, especially when this disease is suspected, should be strongly recommended.

Abstract

Renal maldevelopment (RM) has been proposed to replace the old and sometimes misused term “renal dysplasia” in dogs. Although renal dysplasia has been described in Boxers, hereditary transmission has only been hypothesized. This study reports clinical and renal histological findings in Boxer dogs with RM, proposing a possible mode of inheritance. Medical records of 9 female Boxer dogs, older than 5 months and with a clinical diagnosis of chronic kidney disease prior to one year of age, were retrospectively reviewed. Polyuria and polydipsia (PU/PD), decreased appetite, weight loss, lethargy and weakness were described in all affected dogs. Common laboratory findings were proteinuria, diluted urine, non-regenerative anemia, azotemia, hyperphosphatemia, hypoalbuminemia and hypercholesterolemia. Histopathology of the kidneys revealed the presence of immature glomeruli in all dogs, which is consistent with RM. In 7 related dogs, the pedigree analysis showed that a simple autosomal recessive trait may be a possible mode of inheritance. Renal maldevelopment should be suspected in young Boxer dogs with a history of PU/PD, decreased appetite, weight loss, lethargy, weakness and proteinuria. Due to its possible inheritance, an early diagnosis of RM may allow clinicians to promptly identify other potentially affected dogs among the relatives of the diagnosed case.

Diffuse leiomyomatosis with circumferential thickening of the gastrointestinal wall, resembling human diffuse leiomyomatosis, in a young miniature dachshund

Leiomyoma is the most common mesenchymal tumor in the gastrointestinal (GI) tract. Leiomyomas usually have a single or multinodular mass of various sizes, and affected animals can develop alimentary symptoms depending on the location and size. A 3-year old female miniature dachshund died after a history of refractory rectal prolapse, esophagectasis and aspiration pneumonia. At necropsy, the GI wall at the gastroesophageal and anorectal junctions was circumferentially thickened. Histologically, both GI lesions were composed of bundles of well-differentiated smooth muscles without mass formation or invasive growth. The neoplastic cells had little cellular atypia and low proliferative activity, and were positive for α-smooth muscle actin. The lesions were diagnosed as diffuse leiomyomatosis with circumferential thickening of the GI wall and has not been described in the veterinary literature.

Transplantation of umbilical cord mesenchymal stem cells into mice with focal segmental glomerulosclerosis delayed disease manifestation

Background

Familial focal segmental glomerulosclerosis (fFSGS) is difficult to treat, and stem cell transplantation is one of the most promising approaches for treating this condition. According to the novel mutation site found in our FSGS family, we established a novel animal model of FSGS to explore the application of stem cell therapy in FSGS.

Methods

The animal model used in this experiment was p.Gly1617Valfs X15 (C57BL/6) mutant mice. This mutation was first found in a focal segmental glomerulosclerosis (FSGS) family undergoing renal biopsy in our department. The mouse model was then constructed via CRISPR/Cas9 genomic editing technology. Then, the animals were injected with human umbilical cord mesenchymal stem cells (UCMSC) through the tail vein and regularly followed up to determine phenotypic changes in urine protein quantities, serum creatinine and histological outcomes.

Results

Compared with the positive control group, the levels of urinary protein and serum creatine were decreased significantly after UCMSC transplantation. HE staining images revealed a delay in glomerular sclerosis. Moreover, the secretion of the type IV collagen α3 chain was significantly increased compared with the positive control group, as shown by using immunofluorescence microscopic observation, and electron microscopy proved that the podocytes and basement membrane recovered well from the damage. The intervention also resulted in enhanced IL-22 expression.

Conclusions

UCMSC transplantation may be a potential treatment for FSGS, and IL-22 may play an important role in this process. Further studies are needed to reveal the underlying mechanism.

Abnormal Expression of miR-21 in Kidney Tissue of Dogs With X-Linked Hereditary Nephropathy: A Canine Model of Chronic Kidney Disease

MicroRNAs (miRNAs) are a group of small noncoding RNAs that act as regulators of posttranslational gene/protein expression and are known to play a key role in physiological and pathological processes. The objective of our study was to compare expression of miR-21 in renal tissue from dogs affected with chronic kidney disease (CKD) caused by X-linked hereditary nephropathy (XLHN), a disease equivalent to human Alport syndrome, to that from unaffected dogs. Additionally, we sought to characterize changes in relative mRNA expression of various genes associated with miR-21 function. miRNA was isolated from kidney tissue collected from both affected dogs and unaffected, age-matched littermates at defined milestones of disease progression, including end-stage renal disease (ESRD). Additionally, autopsy samples from affected dogs at ESRD and corresponding unaffected dogs were evaluated. Samples were scored based on histological changes, and relative expression of miR-21 and kidney disease-related genes was determined using quantitative real-time polymerase chain reaction. In affected dogs, significant upregulation of kidney miR-21 was first detected at the milestone corresponding with increased serum creatinine. Furthermore, miR-21 expression correlated significantly with urine protein: urine creatinine ratio, serum creatinine concentration, glomerular filtration rate, and histologic lesions (glomerular damage, tubular damage, chronic inflammation, and fibrosis). At end-stage disease, COL1A1, TGFB1 and its receptor, TGFB2, and Serpine1 were upregulated, while PPARA, PPARGC1A, ACADM, SOD1, and EGF were downregulated. In conclusion, miR-21 is abnormally upregulated in the kidneys of dogs with CKD caused by XLHN, which may play an important pathologic role in the progression of disease by dysregulating multiple pathways.

Observational Study Design in Veterinary Pathology, Part 1: Study Design

Observational studies are the basis for much of our knowledge of veterinary pathology and are highly relevant to the daily practice of pathology. However, recommendations for conducting pathology-based observational studies are not readily available. In part 1 of this series, we offer advice on planning and conducting an observational study with examples from the veterinary pathology literature. Investigators should recognize the importance of creativity, insight, and innovation in devising studies that solve problems and fill important gaps in knowledge. Studies should focus on specific and testable hypotheses, questions, or objectives. The methodology is developed to support these goals. We consider the merits and limitations of different types of analytic and descriptive studies, as well as of prospective vs retrospective enrollment. Investigators should define clear inclusion and exclusion criteria and select adequate numbers of study subjects, including careful selection of the most appropriate controls. Studies of causality must consider the temporal relationships between variables and the advantages of measuring incident cases rather than prevalent cases. Investigators must consider unique aspects of studies based on archived laboratory case material and take particular care to consider and mitigate the potential for selection bias and information bias. We close by discussing approaches to adding value and impact to observational studies. Part 2 of the series focuses on methodology and validation of methods.

Urinary epidermal growth factor as a prognostic marker for the progression of Alport syndrome in children

BACKGROUND

Alport syndrome is a rare hereditary kidney disease manifested with progressive renal failure. Considerable variation exists in terms of disease progression among patients with Alport syndrome. Identification of patients at high risk of rapid progression remains an unmet need. Urinary epidermal growth factor (uEGF) has been shown to be independently associated with risk of progression to adverse kidney outcome in multiple independent adult chronic kidney disease (CKD) cohorts. In this study, we aim to assess if uEGF is associated with kidney impairment and its prognostic value for children with Alport syndrome.

METHODS

One hundred and seventeen pediatric patients with Alport syndrome and 146 healthy children (3-18 years old) were included in this study. uEGF was measured in duplicates in baseline urine samples using ELISA (R&D) and concentration was normalized by urine creatinine (uEGF/Cr). In patients with longitudinal follow-up data (n = 38), progression was defined as deteriorated kidney function (CKD stage increase) during follow-up period (follow-up length is about 31 months in average). The association of baseline uEGF/Cr level with estimated glomerular filtration rate (eGFR) slope and Alport syndrome patients' progression to a more advanced CKD stage during the follow-up period was used to evaluate the prognostic value of the marker.

RESULTS

We found that uEGF/creatinine (uEGF/Cr) decreases with age in pediatric patients with Alport syndrome with a significantly faster rate than in healthy children of the same age group. uEGF/Cr is significantly correlated with eGFR (r = 0.75, p < 0.001), after adjustment for age. In 38 patients with longitudinal follow-up, we observed a significant correlation between uEGF/Cr and eGFR slope (r = 0.58, p < 0.001). Patients with lower uEGF/Cr level were at increased risk of progression to a higher CKD stage. uEGF/Cr was able to distinguish progressors from non-progressors with an AUC of 0.88, versus 0.77 by eGFR and 0.81 by 24-h urinary protein (24-h UP).

CONCLUSIONS

Our study suggests that uEGF/Cr is a promising biomarker for accelerated kidney function decline in pediatric patients with Alport syndrome. It may help to identify patients at high risk of progression for targeted clinical care and improve the patients' stratification in interventional trials.

RNA-seq of serial kidney biopsies obtained during progression of chronic kidney disease from dogs with X-linked hereditary nephropathy

Dogs with X-linked hereditary nephropathy (XLHN) have a glomerular basement membrane defect that leads to progressive juvenile-onset renal failure. Their disease is analogous to Alport syndrome in humans, and they also serve as a good model of progressive chronic kidney disease (CKD). However, the gene expression profile that affects progression in this disease has only been partially characterized. To help fill this gap, we used RNA sequencing to identify differentially expressed genes (DEGs), over-represented pathways, and upstream regulators that contribute to kidney disease progression. Total RNA from kidney biopsies was isolated at 3 clinical time points from 3 males with rapidly-progressing CKD, 3 males with slowly-progressing CKD, and 2 age-matched controls. We identified 70 DEGs by comparing rapid and slow groups at specific time points. Based on time course analysis, 1,947 DEGs were identified over the 3 time points revealing upregulation of inflammatory pathways: integrin signaling, T cell activation, and chemokine and cytokine signaling pathways. T cell infiltration was verified by immunohistochemistry. TGF-β1 was identified as the primary upstream regulator. These results provide new insights into the underlying molecular mechanisms of disease progression in XLHN, and the identified DEGs can be potential biomarkers and therapeutic targets translatable to all CKDs.