Polycystic Kidney Disease Rats Research Articles

Detection of Inflammatory Signaling in Individuals with Bardet-Biedl Syndrome Presenting Symptoms of Polycystic Kidney Disease

Context: Bardet-Biedl syndrome is a rare genetic disorder with variable prevalence rates across populations, characterized by symptoms such as retinal degeneration and intellectual disability. In this study, researchers investigated renal cystic epithelia from patients with PKD1 mutations. This study identified the upregulation of genes related to the Jak-STAT pathway and NF-κB signaling in these renal cells. These pathways appear to be crucial in regulating immune responses within cystic epithelial and renal cell types in PKD-affected kidneys. Evidence Acquisition: This study was carried out through a literature search with the keywords of polycystic kidney disease (PKD), Newborn, and Bardet-Biedl syndrome (BBS), combined with Drug Therapy in Scopes, PubMed, and Web of Science. This study included relevant articles (i.e., randomized controlled trials, observational studies, guidelines, and reviews) written in English and published between 2000 and 2023. Results: Recent genome-wide expression analyses have provided valuable insights into the molecular mechanisms associated with PKD. The Jak-STAT system, essential for immune signaling, can be activated by cytokines, such as interleukin 6 (IL-6) and interferon-gamma (IFN-γ). Conclusions: Promising developments in the treatment of PKD have emerged from studies involving immune-modulating drugs in animal models. Glucocorticoids and rosmarinic acid exhibited positive effects, reducing cystic indices and preserving renal function in PKD mice and rats. Mycophenolate mofetil, an immunosuppressive drug, showed effectiveness in reducing cyst area, inflammation, and fibrosis in rat models. Additionally, COX-2 inhibitors, PPARγ agonists, and vasopressin V2 receptor antagonists demonstrated potential in slowing cystic disease progression.

Pinostrobin inhibits renal CFTR-mediated Cl− secretion and retards cyst growth in cell-derived cyst and polycystic kidney disease rats

Cystic fibrosis transmembrane conductance regulator (CFTR) plays crucial role in renal cyst expansion via increase in fluid accumulation. Inhibition of CFTR has been proposed to retard cyst development and enlargement in polycystic kidney disease (PKD). Pinostrobin, a bioactive natural flavonoid, possesses several pharmacological effects. The present study investigated pharmacological effects of pinostrobin on CFTR-mediated Cl− secretion and renal cyst expansion in in vitro and in vivo models. Pinostrobin (10 and 50 μM) reduced number of MDCK cell-derived cyst colonies and inhibited cyst expansion via inhibition of cell proliferation and CFTR-mediated Cl− secretion. The inhibitory effect of pinostrobin was not due to the decrease in cell viability and activity of Na+-K+-ATPase. We also investigated the natural analogue pinocembrin as well as the synthetic analogue pinostrobin oxime. Both pinocembrin and pinostrobin oxime did not reduce CFTR-mediated Cl− secretion. In PKD rats, oral administration of pinostrobin (40 mg/kg/day) exhibited a decreasing in cystic area compared to vehicle-treated rats. Pinostrobin treatment inhibited renal expression of CFTR protein in PKD rats. Our findings highlighted the potential therapeutic application of pinostrobin in PKD.

Impaired Hedgehog-Gli1 Pathway Activity Underlies the Vascular Phenotype of Polycystic Kidney Disease.

Polycystic kidney disease (PKD) has been linked to abnormal structure/function of ciliary proteins, leading to renal dysfunction. Recently, attention has been focused in the significant vascular abnormalities associated with PKD, but the mechanisms underlying this phenomenon remain elusive. Here, we seek to define the molecular events regulating the angiogenic imbalance observed in PKD. Using micro computed tomography (n=7) and protein expression analysis (n=5), we assessed the vascular density and the angiogenic profile of noncystic organs in a well-established PKD rat model (Polycystic Kidney-PCK rat). Heart and lungs of PCK rats have reduced vascular density and decreased expression of angiogenic factors compared with wild type. Similarly, PCK-vascular smooth muscle cells (VSMCs; n=4) exhibited lower levels of vascular markers. Then, using small interfering RNA (n=4), we determined the role of the ciliary protein fibrocystin in wild type-VSMCs, a critical component/regulator of vascular structure and function. Reduction of fibrocystin in wild type-VSMCs (n=4) led to an abnormal angiogenic potential similar to that observed in PCK-VSMCs. Furthermore, we investigated the involvement of the hedgehog signaling, a pathway closely linked to the primary cilium and associated with vascular development, in PKD. Mechanistically, we demonstrated that impairment of the hedgehog signaling mediates, in part, this abnormal angiogenic phenotype. Lastly, overexpression of Gli1 in PCK-VSMCs (n=4) restored the expression levels of proangiogenic molecules. Our data support a critical role of fibrocystin in the abnormal vascular phenotype of PKD and indicate that a dysregulation of hedgehog may be responsible, at least in part, for these vascular deficiencies.

Protective effect of Soluble Epoxide Hydrolase Inhibition in Retinal Vasculopathy associated with Polycystic Kidney Disease.

Rationale: Vasoregression secondary to glial activation develops in various retinal diseases, including retinal degeneration and diabetic retinopathy. Photoreceptor degeneration and subsequent retinal vasoregression, characterized by pericyte loss and acellular capillary formation in the absence diabetes, are also seen in transgenic rats expressing the polycystic kidney disease (PKD) gene. Activated Müller glia contributes to retinal vasodegeneration, at least in part via the expression of the soluble epoxide hydrolase (sEH). Given that an increase in sEH expression triggered vascular destabilization in diabetes, and that vasoregression is similar in diabetic mice and PKD rats, the aim of the present study was to determine whether sEH inhibition could prevent retinal vasoregression in the PKD rat.Methods: One-month old male homozygous transgenic PKD rats were randomly allocated to receive vehicle or a sEH inhibitor (sEH-I; Sar5399, 30 mg/kg) for four weeks. Wild-type Sprague-Dawley (SD) littermates received vehicle as controls. Retinal sEH expression and activity were measured by Western blotting and LC-MS, and vasoregression was quantified in retinal digestion preparations. Microglial activation and immune response cytokines were assessed by immunofluorescence and quantitative PCR, respectively. 19,20-dihydroxydocosapentaenoic acid (19,20-DHDP) mediated Notch signaling, microglial activation and migration were assessed in vivo and in vitro.Results: This study demonstrates that sEH expression and activity were increased in PKD retinae, which led to elevated production of 19,20-DHDP and the depression of Notch signaling. The latter changes elicited pericyte loss and the recruitment of CD11b+/CD74+ microglia to the perivascular region. Microglial activation increased the expression of immune-response cytokines, and reduced levels of Notch3 and delta-like ligand 4 (Dll4). Treatment with Sar5399 decreased 19,20-DHDP generation and increased Notch3 expression. Sar5399 also prevented vasoregression by reducing pericyte loss and suppressed microglial activation as well as the expression of immune-response cytokines. Mechanistically, the activation of Notch signaling by Dll4 maintained a quiescent microglial cell phenotype, i.e. reduced both the surface presentation of CD74 and microglial migration. In contrast, in retinal explants, 19,20-DHDP and Notch inhibition both promoted CD74 expression and reversed the Dll4-induced decrease in migration.Conclusions: Our data indicate that 19,20-DHDP-induced alterations in Notch-signaling result in microglia activation and pericyte loss and contribute to retinal vasoregression in polycystic kidney disease. Moreover, sEH inhibition can ameliorate vasoregression through reduced activity of inflammatory microglia. sEH inhibition is thus an attractive new therapeutic approach to prevent retinal vasoregression.

Ketosis Ameliorates Renal Cyst Growth in Polycystic Kidney Disease

Mild reduction in food intake was recently shown to slow polycystic kidney disease (PKD) progression in mouse models, but whether the effect was due to solely reduced calories or some other aspect of the diet has been unclear. We now show that the benefit is due to the induction of ketosis. Time-restricted feeding, without caloric reduction, strongly inhibits mTOR signaling, proliferation, and fibrosis in the affected kidneys in a PKD rat model. A ketogenic diet had a similar effect and led to regression of renal cystic burden. Acute fasting in rat, mouse, and feline models of PKD results in rapid reduction of cyst volume, while oral administration of the ketone β-hydroxybutyrate (BHB) in rats strongly inhibits PKD progression. These results suggest that cystic cells in PKD are metabolically inflexible, which could be exploited by dietary interventions or supplementation with BHB, representing a new therapeutic avenue to treat PKD.

Crystal deposition triggers tubule dilation that accelerates cystogenesis in polycystic kidney disease.

The rate of disease progression in autosomal-dominant (AD) polycystic kidney disease (PKD) exhibits high intra-familial variability suggesting that environmental factors may play a role. We hypothesized that a prevalent form of renal insult may accelerate cystic progression and investigated tubular crystal deposition. We report that calcium oxalate (CaOx) crystal deposition led to rapid tubule dilation, activation of PKD-associated signaling pathways, and hypertrophy in tubule segments along the affected nephrons. Blocking mTOR signaling blunted this response and inhibited efficient excretion of lodged crystals. This mechanism of "flushing out" crystals by purposefully dilating renal tubules has not previously been recognized. Challenging PKD rat models with CaOx crystal deposition, or inducing calcium phosphate deposition by increasing dietary phosphorous intake, led to increased cystogenesis and disease progression. In a cohort of ADPKD patients, lower levels of urinary excretion of citrate, an endogenous inhibitor of calcium crystal formation, correlated with increased disease severity. These results suggest that PKD progression may be accelerated by commonly occurring renal crystal deposition which could be therapeutically controlled by relatively simple measures.

Renal Denervation Mitigates Hypertension and Improves Glomerular Filtration Rate in an Adult Rat Model of Polycystic Kidney Disease

Polycystic kidney disease (PKD) remains the most common form of inherited chronic kidney disease failure, and the only cure is renal transplantation. PKD is also strongly associated with increased arterial pressure (AP) and peripheral sympathetic nerve activity (SNA). Recent studies have shown ablation of renal nerves, or renal denervation (RDN), may be effective treatment for varying forms of HTN and renal disease; however, the role and mechanism for renal nerves in preexisting, PKD‐associated renal dysfunction and HTN remain unclear. Therefore, the aim of study was investigate the role of renal nerves in adult PKD, where we hypothesized RDN would reduce AP, lower peripheral sympathetic tone, and improve glomerular filtration rate (GFR) in the adult PKD rat.To test this hypothesis, 6‐month‐old male and female PKD rats underwent bilateral surgical RDN or sham surgery (Total n=18; 9/group; 3M/6F). RDN was achieved by surgical dissection followed by perivascular application of 10%(v/v) phenol. Cardiovascular parameters were recorded by radiotelemetry which was implanted two weeks prior to experimental treatment. Peripheral sympathetic tone was estimated by depressor response to acute ganglionic blockade (GB). GFR was assessed in unrestrained, conscious rats by acute FITC‐sinistrin clearance. Two weeks following RDN/Sham, rats were euthanized and tissues were collected for further analysis. Data was analyzed by a two‐way ANOVA, across sex and treatment groups (α=0.05). Data presented as mean+SEM.At baseline, no differences in 24‐hour mean AP (132 ± 2 vs. 129 ± 3mmHg), acute GB response (39 ± 3 vs. 42 ± 4ΔmmHg), nor GFR (0.93 ± 0.06 vs. 0.91 ± 0.04 mL/min/100g) were detected between treatment groups. No sex differences at baseline were detected at baseline. Two weeks following treatment, 24‐hour mean AP was lowered in RDN (121 ± 1.5mmHg) vs. sham (130 ± 2.8ΔmmHg), and no effect of sex was observed. Similarly, depressor response to GB was halved in RDN (−16 ± 2 ΔmmHg) compared to sham (−32 ± 3 ΔmmHg), and no effect of sex was detected. GFR was significantly increased in RDN vs. sham (1.18 ± 0.06 vs. 0.84 ± 0.08 mL/min/100g), and no effect of sex was detected. Lastly, no difference in renal cystic index was detected between RDN and sham (8.27 ± 1.39 vs. 8.74 ± 0.90%), and differences between male and female groups were observed.Together, these data support our initial hypothesis, where RDN effectively lowered AP and peripheral sympathetic tone in the PKD rat. This was paired with a significant increase in GFR in these animals, indicating an improvement in renal function despite no observable effect on renal cystic index Of note, the efficacy of RDN was similar across male and female groups. Further studies are underway to determine if the cardiovascular and renal effects observed in this study are primarily mediated by the ablation of the efferent or afferent nerves.Support or Funding InformationThis project was supported in part by NIH 1K99HL141650 (CTB) and R01HL116476 (JWO).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Abstract P119: Hypertension and Renal Dysfunction Are Mitigated by Surgical Renal Denervation in an Adult Rat Model of Polycystic Kidney Disease

Polycystic kidney disease (PKD) is the most common form of inherited chronic kidney disease failure. PKD is also associated with hypertension (HTN) and increased peripheral sympathetic activity (SNA). Recent studies have shown ablation of renal nerves may be effective treatment for varying forms of HTN and renal disease; however, the role and mechanism for renal nerves in PKD-associated renal dysfunction and HTN are unclear. Therefore, this study was conducted to test the hypothesis that renal denervation (RDN) would reduce AP, lower peripheral SNA, and improve renal function in the adult PKD rat. To test this hypothesis, 6-month-old male and female PKD rats underwent bilateral surgical RDN or sham surgery (Total n=18; 9/group; 3M/6F). Cardiovascular parameters were monitored by implanted radiotelemeter. Peripheral sympathetic tone was estimated by depressor response to acute ganglionic blockade (GB). Renal function was assessed by measuring glomerular filtration rate (GFR) by FITC-sinistrin clearance. Two weeks following treatment, rats were euthanized and tissues were collected for further analysis. Data was analyzed by a two-way ANOVA, across sex and treatment groups (α=0.05). Data presented as mean+SEM. At baseline, no differences in mean AP (132±2 vs. 129±3 mmHg), GB response (39±3vs. 42±4 ΔmmHg), nor GFR (0.93±0.06 vs. 0.91±0.04 mL/min/100g) were detected between RDN vs. sham. Two weeks following treatment, AP was lower in RDN (120±2mmHg) vs. sham (128±3mmHg). Similarly, GB was halved in RDN (-16±2 ΔmmHg) compared to sham (-32±3 ΔmmHg). GFR was increased in RDN rats vs. sham (1.18±0.06 vs. 0.84±0.08 mL/min/100g). Lastly, no difference in renal cystic area was detected between RDN and sham (8.27±1.39 vs. 8.74±0.90 %). No effect of sex was detected in any of the reported measurements. Altogether, these data support our initial hypothesis, where RDN effectively lowered AP and peripheral sympathetic tone in the PKD rat. Interestingly, we also observed a substantial increase in GFR in these animals, indicating an improvement in renal function despite no observable effect on cystic area. Of note, RDN was effective in both males and female rats. Further studies using repeated measurements are required to elucidate the order in which these effects occur.

Afferent renal nerves mediate hypertension and renal cystogenesis in a preclinical model of polycystic kidney disease

Polycystic kidney disease (PKD) remains a debilitating and chronic condition, and a common cause of end‐stage renal disease. In addition to renal pathology, hypertension is often presented. Renal sympathetic nerves are well‐known to contribute to renal function and arterial pressure homeostasis, which in turn, may be a novel therapeutic target for hypertension in PKD. Moreover, ablation of the renal sympathetic nerves purportedly mitigates cystic development in a preclinical model of PKD; however, the contribution of efferent of afferent renal nerves in this effect remains unknown. We recently developed a novel method to specifically ablate afferent renal nerves, leaving efferent nerves intact. In this study, we aimed to elucidate the role of renal sympathetic nerves in PKD‐induced hypertension and cystic development, as well as reveal the contribution of the individual efferent and afferent renal nerve populations. We hypothesized efferent renal nerves mediate renal cystogenesis and hypertension in the PKD rat, whereas afferent renal nerves play no role in this disease. To test this hypothesis, we performed a bilateral renal denervation (RDx), afferent‐specific RDx (ADx), or sham surgery on four‐week‐old male and female PKD rats (total n=36; 12/group; 6M/6F). Arterial pressure was measured by radiotelemetry. At 10 weeks of age, rodents were euthanized, and renal samples were collected for blinded histological analysis of cystic development. Renal function was estimated by plasma creatinine (PC) and blood urea nitrogen (BUN). Data was analyzed by a two‐way ANOVA, across sex and treatment groups (α=0.05). Data presented as mean+SEM. At 10 weeks of age, 24‐hour mean systolic arterial pressure (SBP) was lower (p<.05) in RDx (125±2) and ADx (123±3) vs. Sham (132±3 mmHg). Renal cystic index (%cyst/total area) was also reduced (p<.05) in both RDx (9.6±2.1%) and ADx (10.1±1.6%) compared to Sham (14.7±1.9%). No influence of sex was observed in either SBP or cystic index. No effect of treatment or sex was observed on indirect measurements of renal function (i.e. PC and BUN). Based on these findings, we reject our original hypothesis, as ADx mirrored the arterial pressure and cystogenesis effects observed with ablation of both efferent and afferent nerves (i.e. RDx). We conclude that afferent renal nerves contribute to the renal cystogenesis and hypertension in this model of PKD, in which either targeted ablation of afferent renal nerves may be a novel and effective therapeutic approach to PKD treatment. Though the mechanism of ADx treatment remains unclear, we hypothesize that afferent renal nerves mediate cystogenesis and arterial pressure through the suppression vasopressin (AVP), as AVP release is mediated in part by afferent renal nerve activation. Additionally, pharmacological antagonism of AVP activity (i.e. V2 receptor inhibition) in the collecting ducts is an effective clinical therapy to suppress PKD cystogenesis. Further studies are currently underway to elucidate the role of AVP regulation as a potential mechanism by which afferent nerves mediate renal cystogenesis and hypertension in this model.Support or Funding InformationThis project was supported in part by NIH HL116476 (JWO) and AHA 17POST33661003 (CTB).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of dimethyl fumarate on renal disease progression in a genetic ortholog of nephronophthisis.

Dimethyl fumarate is an FDA-approved oral immunomodulatory drug with anti-inflammatory properties that induces the upregulation of the anti-oxidant transcription factor, nuclear factor erythroid-derived factor 2. The aim of this study was to determine the efficacy of dimethyl fumarate on interstitial inflammation and renal cyst growth in a preclinical model of nephronophthisis. Four-week-old female Lewis polycystic kidney disease (a genetic ortholog of human nephronophthisis-9) rats received vehicle (V), 10 mg/kg (D10) or 30 mg/kg (D30) ( n = 8-9 each) dimethyl fumarate in drinking water for eight weeks. Age-matched Lewis control rats were also studied ( n = 4 each). Nuclear factor erythroid-derived factor 2 was quantified by whole-slide image analysis of kidney sections. Renal nuclear factor erythroid-derived factor 2 activation was partially reduced in vehicle-treated Lewis polycystic kidney disease rats compared to Lewis control (21.4 ± 1.7 vs. 27.0 ± 1.6%, mean ± SD; P < 0.01). Dimethyl fumarate upregulated nuclear factor erythroid-derived factor 2 in both Lewis Polycystic Kidney Disease (D10: 35.9 ± 3.8; D30: 33.6 ± 3.4%) and Lewis rats (D30: 34.4 ± 1.3%) compared to vehicle-treated rats ( P < 0.05). Dimethyl fumarate significantly reduced CD68+ cell accumulation in Lewis polycystic kidney disease rats (V: 31.7 ± 2.4; D10: 23.0 ± 1.1; D30: 21.5 ± 1.9; P < 0.05). In Lewis polycystic kidney disease rats, dimethyl fumarate did not alter the progression of kidney enlargement (V: 6.4 ± 1.6; D10: 6.9 ± 1.2; D30: 7.3 ± 1.3%) and the percentage cystic index (V: 59.1 ± 2.7; D10: 55.7 ± 3.5; D30: 58.4 ± 2.9%). Renal dysfunction, as determined by the serum creatinine (Lewis + V: 26 ± 4 vs. LPK + V: 60 ± 25 P < 0.01; LPK + D10: 47 ± 7; LPK + D30: 47 ± 9 µmol/L), and proteinuria were also unaffected by dimethyl fumarate treatment. In conclusion, the upregulation of nuclear factor erythroid-derived factor 2 by dimethyl fumarate reduced renal macrophage infiltration in nephronophthisis without adverse effects, suggesting that it could potentially be used in combination with other therapies that reduce the rate of renal cyst growth. Impact statement This is the first study to investigate the effects of dimethyl fumarate in a model of cystic kidney disease. The study assessed the therapeutic efficacy of dimethyl fumarate in upregulating renal nuclear factor erythroid-derived factor 2 expression, reducing macrophage accumulation and cyst progression in a Lewis polycystic kidney disease rat model. This study demonstrates that dimethyl fumarate significantly upregulated renal nuclear factor erythroid-derived factor 2 expression and attenuates renal macrophage infiltration, but had no effect on renal cyst progression, cardiac enlargement, and improving renal function.

Can Ferumoxytol be Used as a Contrast Agent to Differentiate Between Acute and Chronic Inflammatory Kidney Disease?: Feasibility Study in a Rat Model.

Ferumoxytol, an intravenous iron supplement, can be used in off-label mode as a contrast agent in magnetic resonance imaging. The aim of this study was to assess whether ferumoxytol can be used as a marker of inflammation in animal models of acute and chronic inflammatory kidney diseases. The institutional animal care committee approved this study. A total of 18 rats were examined: 6 healthy Sprague Dawley rats as a control group; 6 rats with polycystic kidney disease (PKD) as a model for chronic inflammatory disease; Thy-1, an antibody triggering glomerulonephritis, was injected in 6 rats as a model for acute inflammation. Each rat was examined directly before and 24 hours after intravenous administration of ferumoxytol at a dose of 30 mg Fe/kg body weight. T2* times of renal tissue were approximated using a multiecho sequence. Changes in relative T2* times and T2 signal intensity after ferumoxytol injection were calculated. Statistically significant differences between the 3 groups were found: the T2* times of both, Thy-1 and PKD rats were statistically significant different compared with the control group (T2* time ratio after/before: Thy-1, 0.21; PKD, 0.19, control, 0.28; P = 0.002). The highest T2 signal loss in the renal cortex was observed in the Thy-1 rats (T2 signal intensity ratio after/before: Thy-1, 0.49; PKD, 0.79; control, 0.78; P = 0.0005). Ferumoxytol-enhanced magnetic resonance imaging allows detection and differentiation of acute and chronic inflammatory kidney disease based on different patterns of parenchymal ferumoxytol depositions. Ferumoxytol thus might help to differentiate between different types of inflammation in various kidney diseases.

Constitutive renal Rel/nuclear factor-κB expression in Lewis polycystic kidney disease rats.

To determine the temporal expression and pattern of Rel/nuclear factor (NF)-κB proteins in renal tissue in polycystic kidney disease (PKD). The renal expression of Rel/NF-κB proteins was determined by immunohistochemistry, immunofluorescence and immunoblot analysis in Lewis polycystic kidney rats (LPK, a genetic ortholog of human nephronopthsis-9) from postnatal weeks 3 to 20. At each timepoint, renal disease progression and the mRNA expression of NF-κB-dependent genes (TNFα and CCL2) were determined. NF-κB was also histologically assessed in human PKD tissue. Progressive kidney enlargement in LPK rats was accompanied by increased renal cell proliferation and interstitial monocyte accumulation (peaking at weeks 3 and 10 respectively), and progressive interstitial fibrosis (with α smooth muscle actin and Sirius Red deposition significantly increased compared to Lewis kidneys from weeks 3 to 6 onwards). Rel/NF-κB proteins (phosphorylated-p105, p65, p50, c-Rel and RelB) were expressed in cystic epithelial cells (CECs) of LPK kidneys as early as postnatal week 3 and sustained until late-stage disease at week 20. From weeks 10 to 20, nuclear p65, p50, RelB and cytoplasmic IκBα protein levels, and TNFα and CCL2 expression, were upregulated in LPK compared to Lewis kidneys. NF-κB proteins were consistently expressed in CECs of human PKD. The DNA damage marker γ-H2AX was also identified in the CECs of LPK and human polycystic kidneys. Several NF-κB proteins are consistently expressed in CECs in human and experimental PKD. These data suggest that the upregulation of both the canonical and non-canonical pathways of NF-κB signaling may be a constitutive and early pathological feature of cystic renal diseases.

Systemic treatment with erythropoietin protects the neurovascular unit in a rat model of retinal neurodegeneration.

Rats expressing a transgenic polycystic kidney disease (PKD) gene develop photoreceptor degeneration and subsequent vasoregression, as well as activation of retinal microglia and macroglia. To target the whole neuroglialvascular unit, neuro- and vasoprotective Erythropoietin (EPO) was intraperitoneally injected into four –week old male heterozygous PKD rats three times a week at a dose of 256 IU/kg body weight. For comparison EPO-like peptide, lacking unwanted side effects of EPO treatment, was given five times a week at a dose of 10 µg/kg body weight. Matched EPO treated Sprague Dawley and water-injected PKD rats were held as controls. After four weeks of treatment the animals were sacrificed and analysis of the neurovascular morphology, glial cell activity and pAkt localization was performed. The number of endothelial cells and pericytes did not change after treatment with EPO or EPO-like peptide. There was a nonsignificant reduction of migrating pericytes by 23% and 49%, respectively. Formation of acellular capillaries was significantly reduced by 49% (p<0.001) or 40% (p<0.05). EPO-treatment protected against thinning of the central retina by 10% (p<0.05), a composite of an increase of the outer nuclear layer by 12% (p<0.01) and in the outer segments of photoreceptors by 26% (p<0.001). Quantification of cell nuclei revealed no difference. Microglial activity, shown by gene expression of CD74, decreased by 67% (p<0.01) after EPO and 36% (n.s.) after EPO-like peptide treatment. In conclusion, EPO safeguards the neuroglialvascular unit in a model of retinal neurodegeneration and secondary vasoregression. This finding strengthens EPO in its protective capability for the whole neuroglialvascular unit.

Dietary n-3 polyunsaturated fatty acids or soy protein isolate did not attenuate disease progression in a female rat model of autosomal recessive polycystic kidney disease

Polycystic kidney disease (PKD) is an incurable genetic disorder that is characterized by multiple benign cysts. As PKD advances, cyst growth increases kidney volume, decreases renal function, and may lead to end-stage renal disease; however, in a PKD rat model, feeding soy protein isolate (SPI) reduced cyst proliferation and growth. The n-3 polyunsaturated fatty acids (PUFAs) are noted for their anti-inflammatory actions. Therefore, diet therapy could offer a potentially efficacious, safe, and cost-effective strategy for treating PKD. The objective of this study was to investigate the role of soy protein and/or n-3 PUFAs on PKD progression and severity in the rat model of autosomal recessive PKD. We hypothesized that the antiproliferative and anti-inflammatory actions associated with soy protein and n-3 PUFA supplementation will attenuate PKD progression in female PCK rats. For 12weeks, young (age, 28 days) female PCK rats were randomly assigned (n=12/group) to 4 different diets: casein±corn oil, casein±soybean oil, SPI±soybean oil, or SPI±1:1 soybean/salmon oil (SPI±SB). The feeding of the different protein and lipid sources had no significant effect on relative kidney weight. Histologic evaluation showed no significant differences in cortical or medullary cyst size, interstitial inflammation, and fibrosis among diet groups. However, rats fed SPI±SB diet had cortical cyst obstruction and the highest (P<.01) serum blood urea nitrogen concentration. Rats fed SPI±SB diet had the highest (P<.001) renal docosahexaeonic acid, but there were no significant differences in renal tissue inflammation and proliferation gene expression among the diet groups. Based on these results, dietary soy protein and/or n-3 PUFAs did not attenuate disease progression or severity in the female PCK rat model of autosomal recessive PKD.

Effect of denervation on viscoelastic properties of large arteries in polycystic kidney disease rats

Effect of denervation on viscoelastic properties of large arteries in polycystic kidney disease rats

Polycystic Kidneys Have Decreased Vascular Density: A Micro‐CT Study

Polycystic kidney disease (PKD) is a common cause of end-stage renal failure and many of these patients suffer vascular dysfunction and hypertension. It remains unclear whether PKD is associated with abnormal microvascular structure. Thus, this study examined the renovascular structure in PKD. PKD rats (PCK model) and controls were studied at 10 weeks of age, and mean arterial pressure (MAP), renal blood flow, and creatinine clearance were measured. Microvascular architecture and cyst number and volume were assessed using micro-computed tomography, and angiogenic pathways evaluated. Compared with controls, PKD animals had an increase in MAP (126.4 ± 4.0 vs. 126.2 ± 2.7 mmHg) and decreased clearance of creatinine (0.39 ± 0.09 vs. 0.30 ± 0.05 mL/min), associated with a decrease in microvascular density, both in the cortex (256 ± 22 vs. 136 ± 20 vessels per cm2) and medullar (114 ± 14 vs. 50 ± 9 vessels/cm2) and an increase in the average diameter of glomeruli (104.14 ± 2.94 vs. 125.76 ± 9.06 mm). PKD animals had increased fibrosis (2.2 ± 0.2 fold vs. control) and a decrease in the cortical expression in hypoxia inducible factor 1-α and vascular endothelial growth factor. PKD animals have impaired renal vascular architecture, which can have significant functional consequences. The PKD microvasculature could represent a therapeutic target to decrease the impact of this disease.

Alzheimer’s Disease and Retinal Neurodegeneration Share a Consistent Stress Response of the Neurovascular Unit

Background: The pathogenesis of Alzheimer’s disease (AD) is characterized by neuronal injury, activation of microglia and astrocytes, deposition of amyloid-β and secondary vessel degeneration. In the polycystic kidney disease (PKD) rat model, we observed neuronal injury, microglial activation and vasoregression. We speculated that this neuroretinal degeneration shares important pathogenetic steps with AD. Therefore, we determined the activation of astrocytes and the accumulation of amyloid-β in PKD retinae. Methods: Immunohistochemistry of PKD retinae for vimentin, carboxymethyllysin, beta-Amyloid 1-42, High-Mobility-Group- Protein B1 and amyloid protein precursor was performed. Results: Adjunct to astrocyte activation, accumulation of beta-Amyloid 1-42 and High-Mobility-Group-Protein B1 in astrocytes and around vessels of the superficial network was found in PKD retinae prior to the onset of vasoregression. Amyloid precursor protein was localized adjacent to the outer segment of photoreceptors in PKD and control rats. The parallel appearance of AD-related peptides indicates an alarmine based response to photoreceptor degeneration and secondary vasoregression. Conclusion: The model has broad overlap with AD and may be suitable to study beneficial pharmacological concepts.

Metabolomic profiling of the autosomal dominant polycystic kidney disease rat model

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited systemic disease characterized by renal cyst expansion, resulting in renal failure. With the progression of renal damage, the accumulation of uremic compounds is recently reported to subsequently cause further renal damage and hypertension. Finding uremic toxins and sensitive markers for detecting the early stage of ADPKD is necessary to clarify its pathophysiological process and to prevent its progression. The aim of this study was to analyze the profile of uremic retention solutes of ADPKD by capillary electrophoresis-mass spectrometry (CE-MS) using the Han:SPRD rat model. Two hundred and ninety-seven cations and 190 anions were comprehensively analyzed by CE-MS in Han:SPRD rats and control rats. We found 21 cations and 19 anions that accumulated significantly in the heterozygous (Cy/+) ADPKD rat model compared with control rats. Among the compounds, increases in 5-methyl-2'-deoxycytidine, glucosamine, ectoine, allantoate, α-hydroxybenzoate, phenaceturate and 3-phenylpropionate and decreases in 2-deoxycytidine, decanoate and 10-hydroxydecanoate were newly identified in the ADPKD Cy/+ rats. We identified uremic retention solutes in ADPKD Cy/+ rats. Compounds related to ADPKD could be useful markers for detecting the early stage of ADPKD.

Early Cyst Growth Is Associated with the Increased Nuclear Expression of Cyclin D1/Rb Protein in an Autosomal-Recessive Polycystic Kidney Disease Rat Model

Background: In this study we hypothesised that proliferation, and the increased expression of G₁-phase cyclins (D1, E) and phosphorylated retinoblastoma protein (p-Rb) is restricted to the early period of synchronized cyst growth in autosomal-recessive polycystic kidney disease (ARPKD). Methods: Lewis polycystic kidney disease (lpk) rats (model of ARPKD; postnatal weeks 1, 3, 6, 12 and 24; n = 6 each) as well as human juvenile cystic renal disease tissue (n = 2) were examined. Results: Between weeks 1 and 3, the percentage cyst area increased 6-fold in lpk rats, followed by a more progressive rise (1.5-fold increase) until week 24. The number of Ki-67-, cyclin D1- and p-Rb-positive cells increased in lpk rats and peaked at week 3, declining thereafter. By serial sections, cysts co-expressed Ki-67, cyclin D1 and p-Rb. The expression of cyclin E was variable, and peaked at week 24. In human tissue, small cysts had a higher expression of p-Rb. Conclusion: Proliferation and the increased nuclear expression of cyclin D1 and p-Rb coincide with the early phase of cyst growth in rats and humans, suggesting that there might be a therapeutic window in which cyclin-dependent kinase inhibitors are most effective in preventing kidney enlargement in ARPKD.

What Drives Cyst Formation in PKD?

Polycystic kidney disease (PKD) is the most common genetic cause of chronic kidney disease, with an incidence of 1:400 to 1:1000.1 PKD is characterized by many large fluid-filled cysts in the kidney and often leads to end-stage renal failure. Intensive work from numerous international teams has succeeded in identifying three genes that account for almost all cases of PKD: polycystin-1 ( PC-1 ), polycystin-2 ( PC-2 ), and polycystic kidney and hepatic disease 1 ( Pkhd1 ).2–4 Autosomal dominant PKD is caused by mutations in PC-1 or PC-2. PC-1 encodes a protein with a large extracellular domain, 11 transmembrane domains, and a cytoplasmic tail . PC-2 encodes a transient receptor potential channel with six transmembrane domains that resembles PC-1. Autosomal recessive PKD is caused by mutations in Pkhd1, another protein with a large extracellular domain, a single transmembrane domain, and a cytoplasmic domain. Although the loci responsible for PKD are known, it is still poorly understood why mutations in PC-1 , PC-2 , and Pkhd1 result in cyst formation. Numerous models have been proposed to account for the development of cysts.1 Recent notions, which raise a great deal of interest, are that ciliary function and/or planar cell polarity (PCP) is disrupted during cyst formation. The primary cilium is an antenna-like structure that emerges from the apical surface of kidney epithelial cells, which has been found to be a key signaling center for many developmental pathways.5 A role for …