Uraemic extracellular vesicles augment osteogenic transdifferentiation of vascular smooth muscle cells via enhanced AKT signalling and PiT-1 expression.

Extracellular vesicles (EV) function as messengers between endothelial cells (EC) and vascular smooth muscle cells (VSMC). Since chronic kidney disease (CKD) increases the risk for vascular calcifications, we investigated whether EV derived from uraemic milieu-stimulated EC and derived from uraemic rats impact the osteogenic transdifferentiation/calcification of VSMC. For that purpose, human EC were treated with urea and indoxyl sulphate or left untreated. Experimental uraemia in rats was induced by adenine feeding. 'Uraemic' and control EV (EVUR ; EVCTRL ) were isolated from supernatants and plasma by using an exosome isolation reagent. Rat VSMC were treated with a pro-calcifying medium (CM) with or without EV supplementation. Gene expressions, miRNA contents and protein expressions were determined by qPCR and Western blots, respectively. Calcifications were determined by colorimetric assays. Delivery of miRNA inhibitors/mimics to EV and siRNA to VSMC was achieved via transfection. EVCTRL and EVUR differed in size and miRNA contents. Contrary to EVCTRL , EC- and plasma-derived EVUR significantly increased the pro-calcifying effects of CM, including altered gene expressions of osterix, runx2, osteocalcin and SM22α. Further, EVUR enhanced the protein expression of the phosphate transporter PiT-1 in VSMC and induced a phosphorylation of AKT and ERK. Knock down of PiT-1 and individual inhibition of AKT and ERK signalling in VSMC blocked the pro-calcifying effects of EVUR . Similar effects were achieved by inhibition of miR-221/-222 and mimicking of miR-143/-145 in EVUR . In conclusion, EVUR might represent an additional puzzle piece of the complex pathophysiology of vascular calcifications in CKD.

Skeletal myopathy in CKD: a comparison of adenine-induced nephropathy and 5/6 nephrectomy models in mice.

Preclinical animal models of chronic kidney disease (CKD) are critical to investigate the underlying mechanisms of disease and to evaluate the efficacy of novel therapeutics aimed to treat CKD-associated pathologies. The objective of the present study was to compare the adenine diet and 5/6 nephrectomy (Nx) CKD models in mice. Male and female 10-wk-old C57BL/6J mice (n = 5-9 mice/sex/group) were randomly allocated to CKD groups (0.2-0.15% adenine-supplemented diet or 5/6 Nx surgery) or the corresponding control groups (casein diet or sham surgery). Following the induction of CKD, the glomerular filtration rate was reduced to a similar level in both adenine and 5/6 Nx mice (adenine diet-fed male mice: 81.1 ± 41.9 µL/min vs. 5/6 Nx male mice: 160 ± 80.9 µL/min, P = 0.5875; adenine diet-fed female mice: 112.9 ± 32.4 µL/min vs. 5/6 Nx female mice: 107.0 ± 45.7 µL/min, P = 0.9995). Serum metabolomics analysis indicated that established uremic toxins were robustly elevated in both CKD models, although some differences were observed between CKD models (i.e., p-cresol sulfate). Dysregulated phosphate homeostasis was observed in the adenine model only, whereas Ca2+ homeostasis was disturbed in male mice with both CKD models. Compared with control mice, muscle mass and myofiber cross-sectional areas of the extensor digitorum longus and soleus muscles were ∼18-24% smaller in male CKD mice regardless of the model but were not different in female CKD mice (P > 0.05). Skeletal muscle mitochondrial respiratory function was significantly decreased (19-24%) in CKD mice in both models and sexes. These findings demonstrate that adenine diet and 5/6 Nx models of CKD have similar levels of renal dysfunction and skeletal myopathy. However, the adenine diet model demonstrated superior performance with regard to mortality (∼20-50% mortality for 5/6 Nx vs. 0% mortality for the adenine diet, P < 0.05 for both sexes) compared with the 5/6 Nx surgical model.NEW & NOTEWORTHY Numerous preclinical models of chronic kidney disease have been used to evaluate skeletal muscle pathology; however, direct comparisons of popular models are not available. In this study, we compared adenine-induced nephropathy and 5/6 nephrectomy models. Both models produced equivalent levels of muscle atrophy and mitochondrial impairment, but the adenine model exhibited lower mortality rates, higher consistency in uremic toxin levels, and dysregulated phosphate homeostasis compared with the 5/6 nephrectomy model.

Apixaban Downregulates Endothelial Inflammatory and Prothrombotic Phenotype in an In Vitro Model of Endothelial Dysfunction in Uremia.

PURPOSE: Chronic kidney disease (CKD) associates with inflammatory and prothrombotic phenotypes, resulting in higher cardiovascular risk. Factor Xa displays functions beyond coagulation, exhibiting proinflammatory effects. The aim of the present study was to investigate whether a direct FXa inhibitor protects from the endothelial dysfunction (ED) caused by uremia. METHODS: Macro (HUVEC) and microvascular (HMEC) endothelial cells (ECs) were exposed to serum from uremic patients or healthy donors, in absence and presence of apixaban (60 ng/ml). We evaluated changes in surface VCAM-1 and ICAM-1, intracellular eNOS, reactive oxygen species (ROS), and von Willebrand Factor (VWF) production by immunofluorescence, reactivity of the extracellular matrix (ECM) towards platelets, and intracellular signaling. RESULTS: ECs exposed to uremic serum triggered dysregulation of all the parameters. Presence of apixaban resulted in decreased expression of VCAM-1 (178 ± 14 to 89 ± 2% on HMEC and 324 ± 71 to 142 ± 25% on HUVEC) and ICAM-1 (388 ± 60 to 111 ± 10% on HMEC and 148 ± 9% to 90 ± 7% on HUVEC); increased eNOS (72 ± 8% to 95 ± 10% on HMEC); normalization of ROS levels (173 ± 21 to 114 ± 13% on HMEC and 165 ± 14 to 127 ± 7% on HUVEC); lower production of VWF (168 ± 14 to 92 ± 4% on HMEC and 151 ± 22 to 99 ± 11% on HUVEC); and decreased platelet adhesion onto ECM (134 ± 22 to 93 ± 23% on HMEC and 161 ± 14 to 117 ± 7% on HUVEC). Apixaban inhibited p38MAPK and p42/44 activation in HUVEC (139 ± 15 to 48 ± 15% and 411 ± 66 to 177 ± 57%, respectively) (p < 0.05 vs control for all parameters). CONCLUSION: Anti-FXa strategies, such as apixaban, prevented ED caused by the uremic milieu, exhibiting anti-inflammatory and antioxidant properties and modulating the reactivity of the ECM.

Kidney Disease and Epilepsy.

Chronic kidney disease and seizures often co-exist. When seizures are provoked in patients with kidney disease, their treatment poses a particular challenge. Seizures may be provoked in the context of uremia, and toxic substances associated with uremic encephalopathy. In that case, the mainstay of therapy is to treat the uremia before consideration for anticonvulsant therapy. Treatment of seizures in the setting of chronic kidney disease requires special attention to selection of anticonvulsant medications and knowledge of the altered pharmacokinetics of these medications, which may require special titration schedule in that setting. The purpose of this review is to summarize the current knowledge about inter-relation of seizures and kidney disease. The review will also help practitioners who treat patients with renal failure and coexisting seizures in choosing the best treatment options.

Chronic and End-Stage Kidney Disease in the Neurological Intensive Care Unit.

Patients with renal disease have increased rates of admission to the neurological intensive care unit related to overlapping risk factors for renal and cerebrovascular disease as well as unique risks associated with renal dysfunction alone. Management of acute neurological injury in these patients requires individualized attention to diagnostic and management factors as they relate to coagulopathy, disorders of immune function, encephalopathy and renal replacement modalities. Careful consideration of these brain-kidney interactions is necessary to optimize care for this special patient population and improve neurological and renal outcomes.

Effect of High-Density Lipoprotein from Healthy Subjects and Chronic Kidney Disease Patients on the CD14 Expression on Polymorphonuclear Leukocytes.

In uremic patients, high-density lipoprotein (HDL) loses its anti-inflammatory features and can even become pro-inflammatory due to an altered protein composition. In chronic kidney disease (CKD), impaired functions of polymorphonuclear leukocytes (PMNLs) contribute to inflammation and an increased risk of cardiovascular disease. This study investigated the effect of HDL from CKD and hemodialysis (HD) patients on the CD14 expression on PMNLs. HDL was isolated using a one-step density gradient centrifugation. Isolation of PMNLs was carried out by discontinuous Ficoll-Hypaque density gradient centrifugation. CD14 surface expression was quantified by flow cytometry. The activity of the small GTPase Rac1 was determined by means of an activation pull-down assay. HDL increased the CD14 surface expression on PMNLs. This effect was more pronounced for HDL isolated from uremic patients. The acute phase protein serum amyloid A (SAA) caused higher CD14 expression, while SAA as part of an HDL particle did not. Lipid raft disruption with methyl-ß-cyclodextrin led to a reduced CD14 expression in the absence and presence of HDL. HDL from healthy subjects but not from HD patients decreased the activity of Rac1. Considering the known anti-inflammatory effects of HDL, the finding that even HDL from healthy subjects increased the CD14 expression was unexpected. The pathophysiological relevance of this result needs further investigation.

Reducing the Risk of Stroke in Patients with Impaired Renal Function: Nutritional Issues.

Patients with renal failure have extremely high cardiovascular risk; in dialysis patients the risk of stroke is increased approximately 10-fold over that in the general population. Reasons include not only a high prevalence of traditional risk factors such as diabetes, hypertension and dyslipidemia, but also the accumulation of toxic substances that are eliminated by the kidneys, so have very high levels in patients with renal failure. These include plasma total homocysteine, asymmetric dimethylarginine, thiocyanate, and toxic products of the intestinal microbiome (Gut-Derived Uremic Toxins; GDUT), which include trimethylamine N- oxide (TMAO), produced from phosphatidylcholine (largely from egg yolk) and carnitine (largely from red meat). Other GDUT are produced from amino acids, largely from meat consumption. Deficiency of vitamin B12 is very common, raises plasma tHcy, and is easily treated. However, cyanocobalamin is toxic in patients with renal failure. To reduce the risk of stroke in renal failure it is important to limit the intake of meat, avoid egg yolk, and use methylcobalamin instead of cyanocobalamin, in addition to folic acid.

Osteoblastic differentiation of bone marrow mesenchymal stem cells in uremic rats.

Severe secondary hyperparathyroidism (SHPT) represents a high turnover bone disease, osteitis fibrosa, but the pathogenesis of osteitis fibrosa remains to be fully elucidated. We examined the characteristics of the differentiation of bone marrow mesenchymal stem cells (BMSCs) into osteoblasts in uremic rats. We bred 5/6 nephrectomized (Nx) rats with a high phosphorus (P) diet to induce SHPT (Nx + HP), or Nx (Nx + ND) and normal rats (Nc + ND) fed a standard diet (ND). After 8 weeks, BMSCs were isolated from the femur and serum were analyzed. BMSCs underwent flow cytometric examination for the expression patterns of cell surface markers (CD90+, CD29+, CD45-, and CD31-). Serum creatinine (Cre) levels were significantly elevated in the Nx + NP rats compared with the Nc + NP rats. Cre levels in the Nx + HP rats were levels to those in the Nx + ND rats. Serum P and PTH levels were significantly elevated in the Nx + HP rats compared with the Nx + ND rats. Bone morphometrical analysis showed increases in both osteoid volume and eroded surfaces in the Nx + HP but not in the Nx + ND rats. The populations of harvested BMSCs were similar between all three groups. Alp, Runx2, Pth1r and Cyclin D1 mRNA expression in the BMSCs from the Nx + ND rats were significantly suppressed compared with those isolated from the Nc + ND groups. Alizarin red staining tended to be similar to the expression of these mRNA. These results suggest that the BMSCs differentiation into osteoblasts was disturbed in the uremic rats.

The systemic microcirculation in dialysis populations.

In a rapidly expanding population of patients with chronic kidney disease, including 2 million people requiring renal replacement therapy, cardiovascular mortality is 15 times greater than the general population. In addition to traditional cardiovascular risk factors, more poorly defined risks related to uremia and its treatments appear to contribute to this exaggerated risk. In this context, the microcirculation may play an important early role in cardiovascular disease associated with chronic kidney disease. Experimentally, the uremic environment and dialysis have been linked to multiple pathways causing microvascular dysfunction. Coronary microvascular dysfunction is reflected in remote and more easily studied vascular beds such as the skin. There is increasing evidence for a correlation between systemic microvascular dysfunction and adverse cardiovascular outcomes. Systemic microcirculatory changes have not been extensively investigated across the spectrum of chronic kidney disease. Recent advances in non-invasive techniques studying the microcirculation in vivo in man are increasing the data available particularly in patients on hemodialysis. Here, we review current knowledge of the systemic microcirculation in dialysis populations, explore whether non-invasive techniques to study its function could be used to detect early stage cardiovascular disease, address challenges faced in studying this patient cohort and identify potential future avenues for research.

Perspiration interventions for conservative management of kidney disease and uremia.

PURPOSE OF REVIEW: There has been an increasing interest in developing novel technologies to treat patients with chronic kidney disease as evidenced by KidneyX, the public-private partnership between government and industry. Perhaps a simple technology for treating kidney failure would be to utilize perspiration. It is a physiological process, and when used properly it might not be an unpleasant experience. This review will explore the current state of knowledge regarding perspiration therapy in the setting of far advanced kidney failure. RECENT FINDINGS: A literature review using the PubMed database was conducted between 1 April 2019 and 3 September 2019. Search terms are shown in Table 1. Major themes of the results include diaphoresis therapy for patients with chronic kidney disease, excessive perspiration causing kidney disease, analysis of sweat to diagnose cystic fibrosis, and analysis of sweat to replenish lost electrolytes. This review will focus on intentional perspiration for the treatment of patients with end-stage renal disease (ESRD). Studies have shown that perspiration, or sweat-based therapies, can provide some of the most important currently recognized therapeutic goals in treating ESRD. These goals include decreased interdialytic weight gain, reduced serum potassium levels, and benefits to cardiovascular status. Research has shed light on some of the mechanisms, both molecular and clinical, that may be involved in induced perspiration therapy in ESRD. SUMMARY: There is a long history of humans using perspiration for both recreation and therapy. Perspiration therapy for ESRD experienced a surge in the United States in the 1960s but does not have much modern momentum. With the continued growth of the ESRD population worldwide this could be considered an appropriate time to conduct more research into this promising therapy.

Haemodiafiltration does not lower protein-bound uraemic toxin levels compared with haemodialysis in a paediatric population.

BACKGROUND: Haemodiafiltration (HDF) is accepted to effectively lower plasma levels of middle molecules in the long term, while data are conflicting with respect to the additive effect of convection on lowering protein-bound uraemic toxins (PBUTs). Here we compared pre-dialysis ß2-microglobulin (ß2M) and PBUT levels and the percentage of protein binding (%PB) in children on post-dilution HDF versus conventional high- (hf) or low-flux (lf) haemodialysis (HD) over 12 months of treatment. METHODS: In a prospective multicentre, non-randomized parallel-arm intervention study, pre-dialysis levels of six PBUTs and ß2M were measured in children (5-20 years) on post-HDF (n = 37), hf-HD (n = 42) and lf-HD (n = 18) at baseline and after 12 months. Analysis of variance was used to compare levels and %PB in post-HDF versus conventional hf-HD and lf-HD cross-sectionally at 12 months and longitudinal from baseline to 12 months. RESULTS: For none of the PBUTs, no difference was found in either total and free plasma levels or %PB between post-HDF versus the hf-HD and lf-HD groups. Children treated with post-HDF had lower pre-dialysis ß2M levels [median 23.2 (21.5; 26.6) mg/dL] after 12 months versus children on hf-HD [P<0.01; 35.2 (29.3; 41.2) mg/dL] and children on lf-HD [P<0.001; 47.2 (34.3; 53.0) mg/dL]. While ß2M levels remained steady in the hf-HD and lf-HD group, a decrease in ß2M was demonstrated for children on post-HDF (P<0.01). CONCLUSIONS: While post-HDF successfully decreased ß2M, no additive effect on PBUT over 12 months of treatment was found. PBUT removal is complex and hampered by several factors. In children, these factors might be different from adults and should be explored in future research.

Movement Disorders Due to Selective Basal Ganglia Lesions with Uremia.

BACKGROUND: Basal ganglia (BG) lesions are rarely reported in patients with uremia and may manifest by movement disorders. However, their exact incidence and pathogenesis have not been extensively studied. This study aimed to determine the frequency, types, risk variables (clinical, laboratory, and imaging), and manifestations of BG lesions with uremia and patients' neurologic outcomes. METHODS: This observational study included 70 adults (mean age: 45.87 ± 3.36 years; duration of uremia: 5.5 ± 1.5 years). They underwent extensive evaluations (clinical, laboratory, and neuroimaging) and had prospectively evaluated clinically every 3 months for 2 years. Repeated magnetic resonance imaging (MRI) brains were done to patients with movement disorders and correlated with their neurologic outcomes. RESULTS: BG lesions were found in 15 patients (21.4%) and 6 (8.6%) had movement disorders [Parkinsonism (n = 4), choreo-dystonia (n = 1) and dystonia (n = 1)] after the onset of uremia (mean = 10 months). There were no characteristic risk variables that distinguished patients with movement disorders from those without. Five developed movement disorders prior to the period of the study and one was de novo. The majority was females and had diabetes and higher frequencies of abnormal renal dysfunction, metabolic derangements, and white matter hyperintensities in MRIs. Movement disorders persisted in all patients despite the resolution of neuroimaging in three patients. CONCLUSIONS: There is no clear threshold for renal failure to result in movement disorders due to BG lesions. The clinical outcome is variables depending on each patient's comorbidities and complications. Persistent neuronal damage (due to uremic toxins/metabolic/nutritional and ischemic/microvascular factors) has been suggested as the cause of poor neurologic outcomes.

Resveratrol Reduces Kidney Injury in a Rat Model of Uremia and is Associated with Increased Expression of Heat Shock Protein 70 (Hsp70).

BACKGROUND This study aimed to investigate the effects of resveratrol on kidney function in a rat model of uremia and the expression of heat shock proteins. MATERIAL AND METHODS The rat model of uremia was developed by 5/6 nephrectomy of Sprague-Dawley rats. The Hsp70 inhibitor MKT-077, a rhodacyanine dye, was used. The study groups included rats with sham surgery (the sham group), the rat model of uremia (the model group), the solvent-treated control group (the control group), the rat model treated with resveratrol group (the resveratrol group), the rat model treated with MKT-077 (the MKT-077 group), and the resveratrol+MKT-077 group. Kidney tissues were studied histologically. Renal cell apoptosis was detected by the TUNEL method. Expression of p53, Bax, and Bcl-2 mRNA and protein were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and immunohistochemistry, respectively. RESULTS Compared with the sham group, the expression levels of heat shock proteins Hsp70, Hsp90, Hsp27, Hsp25, Hsp40, and Hsp60 in the kidney of the rat model group increased to different degrees. Compared with the model group, the Hsp70 levels in the resveratrol group were significantly increased (p<0.05). Compared with the model group, treatment with MKT-077 reduced the survival rate of rats, which was increased following resveratrol treatment. Compared with the resveratrol group, renal function in the resveratrol+MKT-077 group was significantly reduced (p<0.05). CONCLUSIONS In a rat model of uremia, resveratrol reduced renal injury and improved both renal function and survival, which were associated with increased expression of Hsp70.

[Uremic Toxins in Cognitive Impairment].

Patients with uremia can suffer from decreased renal function and endocrine and metabolism disorders,which can lead to the accumulation of toxins in the body.Accumulation of uremic toxins is a major cause of cognitive dysfunction in uremic patients.This article summarizes some of the cognitive dysfunction-related uremic toxins and their possible mechanisms.

Chronic kidney disease and the gut microbiome.

The gut microbiome is composed of a diverse population of bacteria that have beneficial and adverse effects on human health. The microbiome has recently gained attention and is increasingly noted to play a significant role in health and a number of disease states. Increasing urea concentration during chronic kidney disease (CKD) leads to alterations in the intestinal flora that can increase production of gut-derived toxins and alter the intestinal epithelial barrier. These changes can lead to an acceleration of the process of kidney injury. A number of strategies have been proposed to interrupt this pathway of injury in CKD. The purpose of this review is to summarize the role of the gut microbiome in CKD, tools used to study this microbial population, and attempts to alter its composition for therapeutic purposes.

Accumulation of uremic solutes in the cerebrospinal fluid in experimental acute renal failure.

The accumulation of uremic solutes in kidney failure may impair mental function. The present study profiled the accumulation of uremic solutes in the cerebrospinal fluid (CSF) in acute renal failure. CSF and plasma ultrafiltrate were obtained from rats at 48 h after sham operation (control; n = 10) or bilateral nephrectomy (n = 10) and analyzed using an established metabolomic platform. Two hundred forty-eight solutes were identified as uremic based on their accumulation in the plasma ultrafiltrate of nephrectomized compared with control rats. CSF levels of 124 of these solutes were sufficient to allow calculation of CSF-to-plasma ultrafiltrate concentration ratios. Levels of many of the uremic solutes were normally lower in the CSF than in the plasma ultrafiltrate, indicating exclusion of these solutes from the brain. CSF levels of the great majority of the uremic solutes increased in renal failure. The increase in the CSF was, however, relatively less than in the plasma ultrafiltrate for most solutes. In particular, for the 31 uremic solutes with CSF-to-plasma ultrafiltrate ratios of <0.25 in control rats, the average CSF-to-plasma ultrafiltrate ratio decreased from 0.13 ± 0.07 in control rats to 0.09 ± 0.06 in nephrectomized rats, revealing sustained ability to exclude these solutes from the brain. In summary, levels of many uremic solutes are normally kept lower in the CSF than in the plasma ultrafiltrate by the action of the blood-brain and blood-CSF barriers. These barriers remain functional but cannot prevent accumulation of uremic solutes in the CSF when the kidneys fail.

Synaptic plasticity in hippocampal CA1 neurons and learning behavior in acute kidney injury, and estradiol replacement in ovariectomized rats.

BACKGROUND: Neurological complications may occur in patients with acute or chronic renal failure; however, in cases of acute renal failure, the signs and symptoms are usually more pronounced, and progressed rapidly. Oxidative stress and nitric oxide in the hippocampus, following kidney injury may be involved in cognitive impairment in patients with uremia. Although many women continue taking hormone therapy for menopausal symptom relief, but there are also some controversies about the efficacy of exogenous sex hormones, especially estrogen therapy alone, in postmenopausal women with kidney injury. Herein, to the best of our knowledge for the first time, spatial memory and synaptic plasticity at the CA1 synapse of a uremic ovariectomized rat model of menopause was characterized by estradiol replacement alone. RESULTS: While estradiol replacement in ovariectomized rats without uremia, promotes synaptic plasticity, it has an impairing effect on spatial memory through hippocampal oxidative stress under uremic conditions, with no change on synaptic plasticity. It seems that exogenous estradiol potentiated the deleterious effect of acute kidney injury (AKI) with increasing hippocampal oxidative stress. CONCLUSIONS: Although, estrogen may have some positive effects on cognitive function in healthy subjects, but its efficacy in menopause subjects under uremic states such as renal transplantation, needs to be further investigated in terms of dosage and duration.

Seizures, Antiepileptic Drugs, and CKD.

There are 2 major categories of patients with seizures and chronic kidney disease (CKD): patients who develop acute symptomatic seizures in the setting of CKD and patients with epilepsy who at some point develop CKD. The incidence of uremic seizures with kidney failure is ∼10%. These seizures are often nonconvulsive and may mimic uremic encephalopathy. Recognition and management of such situations may be challenging for treating physicians who are non-neurologists. Furthermore, practitioners caring for patients with seizures with or without an established diagnosis of epilepsy in the setting of CKD frequently encounter challenges in the selection, loading, titration, and maintenance of antiepileptic drugs (AEDs) due to potentially altered pharmacokinetics of the AEDs. We review the pathophysiology of uremia, uremic seizures, and other neurologic complications of kidney failure; management approaches to the treatment of such complications; the relevant mechanisms of action and pharmacokinetics of AEDs with their use in CKD; and in particular, the management of AEDs in patients requiring hemodialysis therapy.

Numerical simulations of the microvascular fluid balance with a non-linear model of the lymphatic system.

Fluid homeostasis is required for life. Processes involved in fluid balance are strongly related to exchanges at the microvascular level. Computational models have been presented in the literature to analyze the microvascular-interstitial interactions. As far as we know, none of those models consider a physiological description for the lymphatic drainage-interstitial pressure relation. We develop a computational model that consists of a network of straight cylindrical vessels and an isotropic porous media with a uniformly distributed sink term acting as the lymphatic system. In order to describe the lymphatic flow rate, a non-linear function of the interstitial pressure is defined, based on literature data on the lymphatic system. The proposed model of lymphatic drainage is compared to a linear one, as is typically used in computational models. To evaluate the response of the model, the two are compared with reference to both physiological and pathological conditions. Differences in the local fluid dynamic description have been observed using the non-linear model. In particular, the distribution of interstitial pressure is heterogeneous in all the cases analyzed. The resulting averaged values of the interstitial pressure are also different, and they agree with literature data when using the non-linear model. This work highlights the key role of lymphatic drainage and its modeling when studying the fluid balance in microcirculation for both to physiological and pathological conditions, e.g. uremia.

High calcium, phosphate and calcitriol supplementation leads to an osteocyte-like phenotype in calcified vessels and bone mineralisation defect in uremic rats.

A link between vascular calcification and bone anomalies has been suggested in chronic kidney disease (CKD) patients with low bone turnover disease. We investigated the vascular expression of osteocyte markers in relation to bone microarchitecture and mineralization defects in a model of low bone turnover CKD rats with vascular calcification. CKD with vascular calcification was induced by 5/6 nephrectomy followed by high calcium and phosphate diet, and vitamin D supplementation (Ca/P/VitD). CKD + Ca/P/VitD group (n = 12) was compared to CKD + normal diet (n = 12), control + normal diet (n = 8) and control + Ca/P/VitD supplementation (n = 8). At week 6, tibia, femurs and the thoracic aorta were analysed by Micro-Ct, histomorphometry and for expression of osteocyte markers. High Ca/P/VitD treatment induced vascular calcification only in CKD rats, suppressed serum parathyroid hormone levels and led to higher sclerostin, DKK1 and FGF23 serum levels. Expression of sclerostin, DKK1 and DMP1 but not FGF23 were increased in calcified vessels from CKD + Ca/P/VitD rats. Despite low parathyroid hormone levels, tibia bone cortical thickness was significantly lower in CKD + Ca/P/VitD rats as compared to control rats fed a normal diet, which is likely the result of radial growth impairment. Finally, Ca/P/VitD treatment in CKD rats induced a bone mineralization defect, which is likely explained by the high calcitriol dose. In conclusion, Ca/P/VitD supplementation in CKD rats induces expression of osteocyte markers in vessels and bone mineralisation anomalies. Further studies should evaluate the mechanisms of high dose calcitriol-induced bone mineralisation defects in CKD.