Unfavorable Reduction in the Ratio of Endothelin B to A Receptors in Experimental 5/6 Nephrectomy and Adenine Models of Chronic Renal Insufficiency

Chronic renal insufficiency (CRI) is characterized by increased endothelin 1 (ET-1) synthesis. We studied rat kidney endothelin receptor A (ETA) and receptor B (ETB) expressions after 12 and 27 weeks of 5/6 nephrectomy, and after 12 weeks of 0.3% adenine diet, representing proteinuric and interstitial inflammation models of CRI, respectively. Uric acid and calcium-phosphate metabolism were modulated after 5/6 nephrectomy, while ETA blocker and calcimimetic were given with adenine. Endothelin receptor mRNA levels were measured using RT-qPCR and protein levels using autoradiography (5/6 nephrectomy) or ELISA (adenine model). Both 12 and 27 weeks after 5/6 nephrectomy, kidney cortex ETA protein was increased by similar to 60% without changes in ETB protein, and the ETB:ETA ratio was reduced. However, the ETB:ETA mRNA ratio did not change. In the adenine model, kidney ETA protein was reduced by similar to 70%, while ETB protein was suppressed by similar to 95%, and the ETB:ETA ratio was reduced by similar to 85%, both at the protein and mRNA levels. The additional interventions did not influence the observed reductions in the ETB:ETAratio. To conclude, unfavorable reduction in the ETB:ETA protein ratio was observed in two different models of CRI. Therefore, ETA blockade may be beneficial in a range of diseases that cause impaired kidney function.Peer reviewe

Ultrathin Polyimide Membrane as Cell Carrier for Subretinal Transplantation of Human Embryonic Stem Cell Derived Retinal Pigment Epithelium

In this study, we investigated the suitability of ultrathin and porous polyimide (PI) membrane as a carrier for subretinal transplantation of human embryonic stem cell (hESC) -derived retinal pigment epithelial (RPE) cells in rabbits. The in vivo effects of hESC-RPE cells were analyzed by subretinal suspension injection into Royal College of Surgeons (RCS) rats. Rat eyes were analyzed with electroretinography (ERG) and histology. After analyzing the surface and permeability properties of PI, subretinal PI membrane transplantations with and without hESC-RPE were performed in rabbits. The rabbits were followed for three months and eyes analyzed with fundus photography, ERG, optical coherence tomography (OCT), and histology. Animals were immunosuppressed with cyclosporine the entire follow-up time. In dystrophic RCS rats, ERG and outer nuclear layer (ONL) thickness showed some rescue after hESC-RPE injection. Cells positive for human antigen were found in clusters under the retina 41 days post-injection but not anymore after 105 days. In rabbits, OCT showed good placement of the PI. However, there was loss of pigmentation on the hESC-RPE-PI over time. In the eyes with PI alone, no obvious signs of inflammation or retinal atrophy were observed. In the presence of hESC-RPE, mononuclear cell infiltration and retinal atrophy were observed around the membranes. The porous ultrathin PI membrane was well-tolerated in the subretinal space and is a promising scaffold for RPE transplantation. However, the rejection of the transplanted cells seems to be a major problem and the given immunosuppression was insufficient for reduction of xenograft induced inflammation.Public Library of Science open acces

Arterial tone in chronic renal insufficiency

Verisuonitonuksen säätely kroonisessa munuaisten vajaatoiminnassa Nykyiset kehittyneet dialyysitekniikat ja munuaisen siirto voivat antaa munuaisten vajaatoimintapotilaille jopa kymmeniä vuosia lisää elinaikaa. Tämän vuoksi loppuvaiheen munuaisten vajaatoimintaa eli uremiaa sairastavat potilaat eivät enää menehdy uremiaan, vaan suurin osa dialyysipotilaiden kuolemista johtuu sydän- ja verenkiertoelimistöön kohdistuvista komplikaatioista kuten sydäninfarktista ja aivohalvauksesta. Näille tapahtumille altistavan valtimopuuston kovettumisen (ateroskleroosi) esiintyminen on jo lievässä munuaisten vajaatoiminnassa moninkertainen verrattuna terveisiin henkilöihin. Valtimoiden sisälehden eli endoteelin tärkeimpiä tehtäviä ovat verisuonitonuksen eli ääreisvastuksen ja sitä kautta verenpaineen säätely, ja veren epätarkoituksenmukaisen hyytymisen (tromboottiset komplikaatiot) estäminen. Endoteelin fysiologisten toimintojen häiriintyminen saattaa olla keskeisessä roolissa sekä kroonisen munuaisten vajaatoiminnan etenemisessä että sen komplikaatioiden syntymekanismeissa. Reniini-angiotensiinijärjestelmä on hyvin tärkeä verenpaineen ja nestetasapainon säätelijä. Sekä systeemisen että kudostason reniini-angiotensiinijärjestelmän patologinen aktivoituminen liittyy keskeisesti munuaissairauksien etenemiseen. Tätä järjestelmää estävät lääkkeet kuten angiotensiinireseptorin salpaajat tarjoavat munuaispotilaille suojaa hidastaen taudin etenemistä, mutta kyseisen ryhmän lääkkeiden yksityiskohtaiset toiminnalliset vaikutukset verisuoniin uremiassa eivät ole tiedossa. Uremiaan liittyvät kalsium-fosforitasapainon häiriöt (korkea verenkierron fosforipitoisuus ja sekundaarinen lisäkilpirauhasen liikatoiminta) aiheuttavat sekä valtimoiden että muiden pehmytkudosten kalsifikaatiota. Munuaispotilaiden hoidossa käytetään ravinnon kalsiumlisää fosforin sitomiseen ja sekundaarisen hyperparatyreoosin hoitoon. Ureemisten kalsium-fosforitasapainon häiriöiden hoidosta ravinnon kalsiumlisällä on ristiriitaisia tuloksia ja tähän liittyvät vaikutukset verisuonitoimintaan ovat osin tuntemattomia. Tässä väitöskirjatyössä tutkittiin valtimoiden toimintaa kokeellisen munuaisten vajaatoiminnan malleissa. Lisäksi selvitettiin angiotensiinireseptorin salpauksen ja ravinnon kalsiumin ja fosforin määrän vaikutuksia verisuonitoimintaan ja kudostason reniini-angiotensiinijärjestelmään. Tutkimuksessa havaittiin, että munuaisten vajaatoimintaan liittyy merkittäviä toiminnallisia häiriöitä valtimoiden laajenemiskyvyssä. Nämä häiriöt selittyivät heikentyneellä endoteelin välittämällä verisuonten laajenemisella (vasodilataatio), sekä kaliumkanavien että typpioksidin vapautumisen kautta. Angiotensiinireseptorin salpaus normalisoi heikentyneen vasodilataation sekä pienissä että keskisuurissa valtimoissa vaikuttamatta verenpaineeseen tai nestekuormaan. Korkean fosforipitoisuuden ja siihen liittyvän hyperparatyreoosin hoito ravinnon kalsiumlisällä laski verenpainetta, vähensi kalsifikaatiota pehmytkudoksissa, vähensi angiotensiinikonvertaasientsyymin synteesiä munuaiskudoksessa ja korjasi heikentyneen vasodilataation vastussuonissa. Ravinnon korkea fosforipitoisuus edelleen heikensi verisuonten laajenemista ja pahensi sekundaarista hyperparatyreoosia. Väitöskirjatyössä selvittettiin uremiaan liittyvien verisuonikomplikaatioiden syntymekanismeja ja saatiin uutta tietoa verisuonten endoteelin ja sileän lihaksen toiminnan muutoksista munuaisten vajaatoiminnassa. Tulokset kalsiumaineenvaihdunnan häiriöiden hoidon ja angiotensiinireseptorin salpauksen vaikutuksista verisuonitonuksen säätelyyn sekä kudostason reniini-angiotensiinijärjestelmään auttavat löytämään uusia keinoja kardiovaskulaaristen komplikaatioiden ehkäisyyn munuaisten vajaatoiminnassa.Chronic renal insufficiency is associated with high morbidity and mortality due to cardiovascular complications. Accumulating evidence shows that the physiological functions of vascular endothelium are disturbed already at the early stages of uremic disease, and impaired regulation of both renovascular and systemic arterial tone plays an important role in the progression of chronic kidney disease itself, as well as in the manifestation of cardiovascular complications that are currently the most frequent cause of death in patients with end-stage renal disease. However, the present knowledge about the underlying pathophysiological mechanisms is scarce, and the current lines in the treatment of renal patients are probably not optimal for the cardiovascular system. Therefore, the objective of this study was to examine the functional and morphological alterations of isolated resistance and conductance arteries in moderate and advanced experimental chronic renal insufficiency. Angiotensin II type 1 receptor antagonists, a class of drugs that has been recently reported to slow down the progression of chronic kidney disease, are widely used to control arterial blood pressure in renal patients. However, the influence of these drugs on the regulation of vascular tone in uremia is unknown, and therefore the current study evaluated the effects of long-term losartan treatment on the uremic changes of small and large arteries in experimental renal insufficiency. High calcium intake has been reported to reduce blood pressure and improve vasorelaxation in experimental hypertension, whereas in renal patients such diet is used to manage hyperphosphatemia and secondary hyperparathyroidism. Therefore, the effects of diet-induced changes in calcium-phosphate balance on resistance artery tone were studied in moderate and advanced chronic renal insufficiency. In addition, the influences of high calcium intake on the uremic changes of local renin-angiotensin system in the kidney, the degree of ectopic calcifications, and renal histology were studied in both moderate and advanced chronic renal insufficiency. Male Sprague-Dawley rats were subjected to 5/6 nephrectomy or sham-operation at the age of 8 weeks. Four weeks later treatments with either losartan or high calcium diet were started and continued for 8 weeks (studies with moderate renal insufficiency). In order to mimic advanced chronic renal insufficiency, the rats were followed for 15 weeks after the subtotal nephrectomy, and thereafter the high calcium and high phosphate diets were applied for 12 weeks. The levels of arterial blood pressure of conscious animals were measured using the tail cuff method. The cardiac synthesis of natriuretic peptides was determined to verify the volume status in the study groups. Renal density of angiotensin II receptors, and renal and aortic angiotensin converting enzyme content, were measured using autoradiography. The in vitro responses of mesenteric resistance and conductance arteries were performed using myographs to measure the changes in arterial wall tension induced by pharmacological vasoconstrictors and vasodilators added to the organ bath containing physiological salt solution. In moderate renal insufficiency, endothelium-mediated vasorelaxation to acetylcholine in both resistance and conductance arteries was impaired via K+ channels, whereas nitric oxide-mediated component of arterial relaxation was preserved. The small arteries of uremic rats also featured eutrophic inward remodelling, as suggested by the increased wall-to-lumen ratio and unchanged cross-sectional area when compared with the arteries of sham-operated controls. Losartan treatment normalized both functional and morphological changes of the arteries in moderate renal insufficiency, without any effect on blood pressure, volume overload or kidney functional parameters. Furthermore, high calcium diet suppressed the elevated levels of parathyroid hormone and phosphate, the effect of which was associated with decreased renal tissue ACE content, reduced albuminuria, inhibited extraskeletal calcification, decreased glomerulosclerosis and tubulo-interstitial fibrosis, reduced volume overload, and improved K+ channel-mediated relaxation of resistance arteries. Moreover, in advanced renal insufficiency, the resistance arteries featured impaired relaxation via both nitric oxide- and K+ channel-mediated pathways. High calcium intake reduced the increased arterial blood pressure, retarded the progression of renal insufficiency, improved survival, and normalized the functional changes of resistance vessels. In contrast, the arteries of uremic rats on high phosphate diet showed virtually no response to acetylcholine. Collectively, the results of the present study suggested that beyond the clinically evidenced benefits on arterial blood pressure and progression of renal scarring, AT1 receptor antagonists confer distinct advantages on arterial tone and morphology in chronic kidney disease. Furthermore, the current study showed that calcium-phosphate balance is a significant modulator of resistance artery tone in chronic renal insufficiency. Finally, these experiments for the first time suggested a link between calcium metabolism and ACE expression in the kidney, which may play a role in the progression of renal damage

Calcium Carbonate versus Sevelamer Hydrochloride as Phosphate Binders after Long-Term Disease Progression in 5/6 Nephrectomized Rats

Our aim was to compare the effects of calcium carbonate and sevelamer-HCl treatments on calcium-phosphate metabolism and renal function in 5/6 nephrectomized (NX) rats so that long-term disease progression preceded the treatment. After 15-week progression, calcium carbonate (3.0%), sevelamer-HCl (3.0%), or control diets (0.3% calcium) were given for 9 weeks. Subtotal nephrectomy reduced creatinine clearance (−40%), plasma calcidiol (−25%), and calcitriol (−70%) and increased phosphate (+37%), parathyroid hormone (PTH) (11-fold), and fibroblast growth factor-23 (FGF-23) (4-fold). In NX rats, calcium carbonate diet increased plasma (+20%) and urinary calcium (6-fold), reduced plasma phosphate (−50%) and calcidiol (−30%), decreased creatinine clearance (−35%) and FGF 23 (−85%), and suppressed PTH without influencing blood pH. In NX rats, sevelamer-HCl increased urinary calcium (4-fold) and decreased creatinine clearance (−45%), PTH (−75%), blood pH (by 0.20 units), plasma calcidiol (−40%), and calcitriol (−65%). Plasma phosphate and FGF-23 were unchanged. In conclusion, when initiated after long-term progression of experimental renal insufficiency, calcium carbonate diet reduced plasma phosphate and FGF-23 while sevelamer-HCl did not. The former induced hypercalcemia, the latter induced acidosis, while both treatments reduced vitamin D metabolites and deteriorated renal function.Thus, delayed initiation influences the effects of these phosphate binders in remnant kidney rats.Copyright © 2014 Suvi Törmänen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

The femoral neck.

<p>Effect of CRI and sevelamer-HCl treatment on (A) volumetric bone mineral density (vBMD), (B) total bone mineral content (BMC), (C) total bone cross-sectional area (tCSA), (D) bone diameter in mediolateral (ML) direction, (E) bone diameter in craniocaudal (CC) direction, and (F) breaking load. Data denotations are mean (line) and SEM (whiskers); ^§P<0.05, ^§§p<0.01 CRI main effect; *P<0.05, ***P<0.001 vs. Sham; ^†P<0.05 vs. CRI.</p

The regions of interest in the femoral bone.

<p>(A) midshaft, analyses in mediolateral and anteroposterior directions; (B) neck, analyses in mediolateral and craniocaudal directions.</p