Unwrapping the origins and roles of the renal endothelium.

The renal vasculature, like all vessels, is lined by a thin layer of simple squamous epithelial cells called an endothelium. These endothelial-lined vessels can be subdivided into four major compartments: arteries, veins, capillaries and lymphatics. The renal vasculature is a highly integrated network that forms through the active processes of angiogenesis and vasculogenesis. Determination of the precise contribution of these two processes and of the molecular signaling that governs the differentiation, specification and maturation of these critical cell populations is the focus of an actively evolving field of research. Although much of the focus has concentrated on the origin of the glomerular capillaries, in this review we extend the investigation to the origins of the endothelial cells throughout the entire kidney and the signaling events that cause their distinct functional and molecular profiles. A thorough understanding of endothelial cell biology may play a critical role in a better understanding of renal vascular diseases.

Continuous real-time viability assessment of kidneys based on oxygen consumption.

BACKGROUND: Current ex vivo quality assessment of donor kidneys is limited to vascular resistance measurements and histological analysis. New techniques for the assessment of organ quality before transplantation may further improve clinical outcomes while expanding the depleted deceased-donor pool. We propose the measurement of whole organ oxygen consumption rate (WOOCR) as a method to assess the quality of kidneys in real time before transplantation. METHODS: Five porcine kidneys were procured using a donation after cardiac death (DCD) model. The renal artery and renal vein were cannulated and the kidney connected to a custom-made hypothermic machine perfusion (HMP) system equipped with an inline oxygenator and fiber-optic oxygen sensors. Kidneys were perfused at 8 degrees C, and the perfusion parameters and partial oxygen pressures (pO(2)) were measured to calculate WOOCR. RESULTS: Without an inline oxygenator, the pO(2) of the perfusion solution at the arterial inlet and venous outlet diminished to near 0 within minutes. However, once adequate oxygenation was provided, a significant pO(2) difference was observed and used to calculate the WOOCR. The WOOCR was consistently measured from presumably healthy kidneys, and results suggest that it can be used to differentiate between healthy and purposely damaged organs. CONCLUSIONS: Custom-made HMP systems equipped with an oxygenator and inline oxygen sensors can be applied for WOOCR measurements. We suggest that WOOCR is a promising approach for the real-time quality assessment of kidneys and other organs during preservation before transplantation.

NADPH-d cells (mast cells) around and within the autonomic nerves of porcine renal hilus.

The enzymehistochemical localization of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) reactive cells next and within the autonomic nerves in the porcine kidney's hilus, close to renal artery and vein as well as in its adventitia, was studied. It was established that the prevailing part of NADPH-d-reactive cells were distributed next to and within NADPH-d-reactive autonomic fibers around the renal vein. Comparatively small number of reactive cells was found around the renal artery, but single NADPH-d-reactive cells were found in the neighbouring autonomic nerves as well. The cells observed next to nerves had much more expressed reaction (granules) than those, located in the nerves. Toluidine blue staining on frozen and paraffine sections from the same areas showed well-expressed gamma-ma metachromasia in mast cells with similar or identical localization. This indicated that observed reactive cells were mast cells. The obtained data convincingly showed that porcine NADPH-d cells may produce nitric oxide and in this way most probably they were involved in the function of autonomic nerves in the renal blood vessels (vasodilatation) and the kidney function, as well.

Endothelin-positive mast cells in porcine renal artery and vein.

For a first time the endothelin (ET)-positive mast cells were examined in the wall of kidney renal artery and vein. The specimen's were collected from six 8-month-old Danmark Landrace pigs, immediately after slaughtering. Mast cells immunopositive to ET granules were observed in the wall of both artery and vein. In the renal artery, they were found mostly between the media and the adventitia. Some mast cells were found in the media, next to smooth muscle cells. Relatively few mast cells were found in the intima and between intima and tunica media. In the renal vein a smaller number of mast cells were observed. They showed similar localization as in the renal artery. Immunopositive mast cells were established also close to endothelial cells - mostly between internal elastic membrane and basal membrane of the endothelium. In conclusion, on the basis of obtained results, presumptions for active participation of ET (most probably mainly ET-1) in the motility of the vessels' smooth muscle and for stimulation of nitric oxide release from the intimal endothelial cells were made.

Accumulating monocytes in the vasculature of rat renal allografts: phenotype, cytokine, inducible no synthase, and tissue factor mRNA expression.

BACKGROUND: Necrotic patches and hemorrhagic lesions develop in the renal tissue between day 4 and day 5 after transplantation of fully allogeneic DA rat kidneys to LEW recipients. These lesions are at least in part due to destruction and obstruction of blood vessels. Damage of graft endothelial cells and blood coagulation are likely to be mediated by intravascular graft leukocytes. However, this cell population has not been thoroughly characterized before. METHODS: We perfused untreated control kidneys, renal isografts, and allografts on day 4 after transplantation with phosphate-buffered saline/ethylenediaminetetraacetic acid to harvest leukocytes from both the blood stream as well as from the marginal intravascular pool. The mRNA expression of typical products of activated monocytes was analyzed in reverse-transcriptase polymerase chain reaction experiments. Graft monocytes were purified and their immunophenotype was investigated by flow cytometry. RESULTS: Allograft rejection led to a 10-fold increase in the number of intravascular graft leukocytes compared to isografts. A mean number of about 100x10(6) leukocytes was harvested from a single allogeneic kidney, about 73% of these cells were monocytes and most of them displayed an activated phenotype. Compared to isografts, intravascular allograft leukocytes displayed an increased expression of tumor necrosis factor-alpha, inducible NO synthase and tissue factor. CONCLUSIONS: Our study shows that large numbers of activated monocytes accumulate inside allograft vessels. As they express genes the products of which might damage the allograft by inducing cell death or thrombosis, we speculate that they directly participate in allograft destruction.

Dynamics of monocytes/macrophages and T lymphocytes in acutely rejecting rat renal allografts.

We examined the infiltration of acutely rejecting renal allografts (DA-->LEW) by ED1+ and ED2+ macrophages and T lymphocytes at intervals of 24 h after transplantation. Donor and recipient macrophages were differentiated by MHC class II antigen expression in double-staining experiments with ED1. Proliferation was assayed after pulse-labelling with BrdU. We subdivided allograft infiltration into three consecutive phases: 1) During phase I on days 1 to 2 after allogeneic kidney transplantation, perivascular infiltrates developed that contained numerous donor and recipient macrophages. Allograft rejection could already be diagnosed 24 h after transplantation by perivascular infiltration of T lymphocytes, whereas T cells were rarely found in isografts. 2) Phase II of allograft rejection from day 3 to 4 was characterized by massive propagation of the infiltrate. About equal numbers of interstitial donor and recipient macrophages were counted. Both macrophages and T lymphocytes proliferated in situ and macrophages outnumbered T cells until complete rejection. 3) During phase III the allograft was destroyed. Large intravascular monocytes surprisingly expressed the ED2 antigen. In the interstitium of viable graft regions, the population of recipient macrophages grew, whereas the population of donor macrophages and of T lymphocytes decreased.

Morphological studies of the valves of the kidney vein in domestic swine.

It was established macroscopically that 37.5% of the renal veins investigated possess valves. Valves were observed on both sides, but predominantly on the left side of the kidneys (14.58%). Some valves were also observed in the main branches of the renal veins. The structure of the valves was studied with the use of light and electron microscopy. The most important finding was the observation of mast cells in the valves. This is probably a common biological phenomenon, since mast cells have been observed in the cardiac valves and the wall of the renal artery and vein.

Age-related changes in the human renal veins and their valves.

Age-related anatomical changes in the human renal veins and their valves were studied. The principal changes were: 1. The muscle fiber bundles were noted to progressively atrophy as a function of age, while conservely the elastic fiber bundles hypertrophied. 2. The valves of the renal veins were observed to become gradually thicker with age as a result of the increased number of collagen fiber bundles.

Leiomiócitos parasitados pelo Trypanosoma Cruzi nas formas congênita e crônica adquirida da doença de Chagas / Smooth muscle cells infected by Trypanosoma Cruzi in congenital and chronic acquired forms of Chagas disease

Os leiomiócitos parassitados pelo T. cruzi, de vasos umbilicais e placentários de casos congênitos da doença de Chagas, foram comparados com células semelhantes da veia suprarrenálica de chagásicos crônicos. Observou-se que algumas destas células, em ambos os grupos, apresentavam envoltório visto à microscopia de fase, nas preparaçöes näo coradas, e à microscopia de luz comum, quando coradas pelo PAS e pela HE. A prata-metenamina cora apenas o envoltório das células parasitadas dos casos de doença de Chagas congênita. A técnica do picro-sirius, associada à microscopia de luz polarizada, mostra que ambos os grupos de leiomiócitos parasitados podem apresentar delicada membrana com birrefrigência discreta "verde limäo", enquanto que un envoltório espesso com forte birrefrigência amarelada ou brancacente é visto apenas nos leiomiócitos fetais. A técnica da peroxidase anti-peroxidase cpara T. cruzi mostra acúmulo de material PAP-positivo formando uma faixa interrompida que se coloca mais internamente à faixa PAS-positivo, em ambas as formas da doença. As modificaçöes nucleares e citoplasmáticas das células fetais parasitadas (Chagas congênito) e dos adultos (chagásicos crônicos) säo muito semelhantes, destacando-se o gigantismo nuclear, o aparecimento de grânulos algumas vezes PAP-positivo, e a desproporçäo entre o aumento do volume celular e o número de parasitas. É possível que o estado de imunodeficiência, localizado na glândula suprarrenal do adulto e o tecido fetal tenham algum papel na gênese dessa peculiaridade das células parasitadas, comuns na doença de Chagas congênita e na forma crônica adquirida

Renal blood vascular system in the elasmobranch, Raja erinacea Mitchill, in relation to kidney zones.

The arrangement and structure of renal blood vessels were studied in a marine skate with injection of silicone rubber and methacrylate resin after intravenous administration of epinephrine and perfusion fixation. The methacrylate casts were investigated with the scanning electron microscope. Histology was performed by light and transmission electron microscopy of serial sections. The course of the blood vessels is described in relation to the renal zones of lateral bundles and mesial tissue. Each nephron performs two loops in the lateral bundles and two coilings in the mesial tissue before it joins the collecting duct system. The lateral bundles contain an elaborate countercurrent arrangement of neck segment, proximal tubule segment PIa, early distal tubule segment, and collecting tubule. Within the bundles, the nephron portions are associated with a blind-ended central vessel, which is connected with the venous sinuses of the mesial tissue. The microcirculatory bed around the bundles is supplied with arterial blood via small bundle arteries that originate from the intrarenal arteries in parallel to the afferent arterioles of the glomeruli. The efferent arterioles of the glomeruli convey their blood to the peritubular sinuses of the mesial tissue, which is largely irrigated with venous blood of the renal portal system. The mesial tissue, containing the proximal tubule segments PIb and PII, intermediate segment, and late distal tubule segment LDTb, receives venous blood from the caudal vein and the lateral musculature via afferent renal and intrarenal veins and from the efferent arterioles of the glomeruli and venules of the microcirculation of the bundles. The sinuses are drained by efferent renal veins via efferent intrarenal veins. By comparing the renal structures of the skate with those of dogfish, a unique type of circulation--as related to nephron segments, renal zones, and fine structure of the wall of the vessels--is revealed in marine elasmobranchs of different evolutionary levels.