Spatiotemporal heterogeneity and patterning of developing renal blood vessels.

The kidney vasculature facilitates the excretion of wastes, the dissemination of hormones, and the regulation of blood chemistry. To carry out these diverse functions, the vasculature is regionalized within the kidney and along the nephron. However, when and how endothelial regionalization occurs remains unknown. Here, we examine the developing kidney vasculature to assess its 3-dimensional structure and transcriptional heterogeneity. First, we observe that endothelial cells (ECs) grow coordinately with the kidney bud as early as E10.5, and begin to show signs of specification by E13.5 when the first arteries can be identified. We then focus on how ECs pattern and remodel with respect to the developing nephron and collecting duct epithelia. ECs circumscribe nephron progenitor populations at the distal tips of the ureteric bud (UB) tree and form stereotyped cruciform structures around each tip. Beginning at the renal vesicle (RV) stage, ECs form a continuous plexus around developing nephrons. The endothelial plexus envelops and elaborates with the maturing nephron, becoming preferentially enriched along the early distal tubule. Lastly, we perform transcriptional and immunofluorescent screens to characterize spatiotemporal heterogeneity in the kidney vasculature and identify novel regionally enriched genes. A better understanding of development of the kidney vasculature will help instruct engineering of properly vascularized ex vivo kidneys and evaluate diseased kidneys.

Enhanced protection of the renal vascular endothelium improves early outcome in kidney transplantation: Preclinical investigations in pig and mouse.

Ischemia reperfusion injury is one of the major complications responsible for delayed graft function in kidney transplantation. Applications to reduce reperfusion injury are essential due to the widespread use of kidneys from deceased organ donors where the risk for delayed graft function is especially prominent. We have recently shown that coating of inflamed or damaged endothelial cells with a unique heparin conjugate reduces thrombosis and leukocyte recruitment. In this study we evaluated the binding capacity of the heparin conjugate to cultured human endothelial cells, to kidneys from brain-dead porcine donors, and to murine kidneys during static cold storage. The heparin conjugate was able to stably bind cultured endothelial cells with high avidity, and to the renal vasculature of explanted kidneys from pigs and mice. Treatment of murine kidneys prior to transplantation reduced platelet deposition and leukocyte infiltration 24 hours post-transplantation, and significantly improved graft function. The present study thus shows the benefits of enhanced protection of the renal vasculature during cold storage, whereby increasing the antithrombotic and anti-adhesive properties of the vascular endothelium yields improved renal function early after transplantation.

Heterotopic renal transplantation in piglets using vascular closure stapler metallic clips or conventional suturing techniques: comparison of vessel growth and macroscopical study.

BACKGROUND/PURPOSE: Our aim was to perform a macroscopic and imaging (ultrasonographic and angiographic) evaluation of vascular closure stapler (VCS) metallic clips for renal transplantation in growing piglets to assess their role for transplantation surgery in young children. If these techniques are to be useful, it is necessary to prove that their use avoids one of the main pitfalls of conventional sutures in this setting, namely lack of growth in the suture line. METHODS: Twenty-four piglets were used for this study. Animals were subjected to a heterotopic renal autotransplantation when they were 45 days old. The right kidney was moved from its normal location to the cranial area of the iliac fossa. The end-to-side anastomoses between the renal artery and vein and the aorta and vena cava, respectively, were performed using VCS metallic clips in 6 animals. Continuous polypropylene suturing was used in another 6 piglets, and continuous polyglycolic acid suture was used in 6 additional piglets. A control group of 6 animals without renal autotransplantation was also included in the study. All animals were allowed to grow for 6 months, during which time serial angiographic and ultrasonographic studies were carried out to assess the existence of vascular flow disturbances or stenosis. Similarly, angiographic measurements were obtained to document growth at the anastomotic site. Longitudinal growth was evaluated postmortem after the 6-month growing period. RESULTS: Angiography showed significant (P < .001) transverse growth in both arteries and veins belonging to the VCS clips, running absorbable suture, or control groups. No significant difference was observed among the 3 groups. Vascular growth in the running nonabsorbable suture (polypropylene) group, however, was significantly less than in the other 3 groups and did not significantly differ from baseline. Baseline luminal diameters at the anastomotic site as measured by angiography in the VCS group were 3.64 ± 0.40 mm in the artery and 5.30 ± 1.43 mm in the vein. After growth, these values increased to 6.87 ± 0.90 mm and 11.27 ± 2.53 mm, respectively. Significant longitudinal growth was evidenced macroscopically after 6 months in both aorta and vena cava in all groups. On the other hand, significant longitudinal growth in the renal artery and vein were only observed in the control, VCS, and absorbable suture groups. CONCLUSIONS: In this experimental setting, satisfactory macroscopic and angiographic vascular growth results were obtained using the VCS clips, suggesting that this suture could be the technique of choice in pediatric transplantation surgery.

Adrenocortical and adrenomedullary homologs in eight species of adult and developing teleosts: morphology, histology, and immunohistochemistry.

Morphology, histology, and immunohistochemistry of the adrenocortical and adrenomedullary homologs (adrenal glands) of the following developing and adult teleosts were examined: Salmoniformes-Oncorhynchus mykiss (rainbow trout), Salmo trutta fario (brown trout), Coregonus lavaretus (white fish); Cyprinodontiformes-Gambusia affinis (mosquito fish). Perciformes-Dicentrarchus labrax (sea bass), Sparus aurata (sea bream), Diplodus sargus (white bream), Oblada melanura (saddled bream). The anatomical relationships of the gland with the renal system and venous vessels were also noted. In adults of all species steroidogenic and catecholaminergic chromaffin cells were found in the head kidney, which is pronephric in origin and subsequently transformed into a hematopoietic lymphatic organ. In Perciformes, chromaffin cells are distributed around the anterior and posterior cardinal veins and ducts of Cuvier; in Salmoniformes, around the posterior cardinal veins and in the hematopoietic tissue; and in G. affinis, around the ducts of Cuvier and posterior cardinal veins, while a few are visible also around the sinus venosus. In Perciformes and Salmoniformes, numerous chromaffin cells are also present in the posterior kidney, derived from the opisthonephros, in contact with the caudal vein. Steroidogenic cells are always confined to the head kidney. During development chromaffin and steroidogenic cells appear early after hatching in the pronephric kidney, at the level of the ducts of Cuvier and of the cephalic part of the posterior cardinal veins. Later, chromaffin cells in Perciformes reach the anterior cardinal veins, and subsequently, in both Perciformes and Salmoniformes, they reach the developing posterior kidney. Their localization along the posterior kidney is still in progress about 4 months after hatching and is completed about a year after hatching. These findings support the concept that the structure of the adrenal gland in teleosts is intermediate between that of the other actinopterygians and that of tetrapods. The development differs from that of tetrapods in that it occurs mainly in the pronephros and only later do chromaffin cells reach the opisthonephric kidney.

Nephrogenesis and renovascular development in angiotensinogen-deficient mice.

Angiotensinogen-deficient mice provide a model to examine the roles of angiotensin II as a renal growth factor in vivo. We monitored nephrogenesis and renovascular development in angiotensinogen-deficient mice from Embryonic Day 13 (E13) to 4 weeks after birth. Northern analysis of homozygote (Atg-/-) mice confirmed the absence of angiotensinogen mRNA in the liver and the kidneys. Embryonic kidneys in Atg-/- mice from E13 to E18 exhibited active nephrogenesis, as also observed in Atg+/- mice and Atg+/+ mice. Furthermore, metanephroi harvested at E12 from Atg-/- embryos showed branching morphogenesis of ureteric bud and tubulogenesis similar to metanephrol from Atg-/- embryos grown with exogenous angiotensin II in serum-free culture. In newborn Atg-/- mice, we observed uniform dilation of the pelvis accompanied by a coarse medulla, which was not noted in Atg+/- or Atg+/+ mice. Hydronephrosis in Atg-/- mice continued, and renal papillae underwent atrophy for the 4 weeks after birth. Another characteristic aspect of the morphology of Atg-/- mice was the thickening of vascular walls as little as 2 weeks after birth. Immunohistochemistry revealed recruitment of renin in hyperplastic vascular smooth muscle cells (VSMC) in Atg-/- mice after 2 weeks. Electron microscopy confirmed that the majority of hyperplastic VSMC contained various sized renin granules with abundant endoplasmic reticulum. In situ hybridization demonstrated that expression of renin mRNA became prominent in parallel with hyperplasia of VSMC, as well as recruitment of renin protein. Furthermore, at 4 weeks, Atg-/- mice expressed alpha-smooth muscle actin in the mesangium, whereas none was ever found in that of Atg+/- mice and Atg+/+ mice. In conclusion, the renin-angiotensin system seems not be essential for nephrogenesis in vivo. Furthermore, hyperplasia of VSMC and expression of the smooth-muscle phenotype in the mesangium are inducible even in the absence of angiotensin II, with hypotension, in vivo.

Renal venous architectonics in domestic swine.

Renal venous architectonics were investigated in 240 kidneys from 120 swines at an age of 1-8 months. The methods used were: preparation, corrosion and X-ray examination. It was established that, in 75% of the cases, v. renalis cranialis and v. renalis caudalis were present. In the rest of the cases (25%), v. renalis intermedia was present. It was also observed that right and left renal veins formed distentions, which enveloped the caudal medial part of each adrenal gland. V. adrenalis (suprarenalis) was not formed as an independent blood vessel. Venous blood from the adrenal gland drains through 2-3 orifices in these distentions. This study describes vv. prelobares, vv, interlobares and vv. arcuatae. Anastomoses were found between them. On that basis this concluded that the renal venous system in domestic swine is not segmented.

Age-related changes of noradrenergic innervation of rat splanchnic blood vessels: a histofluorescence and neurochemical study.

The influence of ageing on the noradrenergic innervation of superior mesenteric artery and vein, renal artery and vein, and portal vein was studied in male Wistar rats by means of catecholamine histofluorescence, image analysis techniques and high pressure chromatography with electrochemical detection. Old age was accompanied by a marked increase in the density of noradrenergic innervation and an increase of noradrenaline levels in superior mesenteric artery, renal artery, and portal vein. In contrast, no significant age-related changes were observed in the density of noradrenergic innervation or in noradrenaline levels in superior mesenteric and renal vein. The present data indicate that, at least in superior mesenteric and renal artery and portal vein, senescence is not accompanied by loss or by lack of change in the noradrenergic innervation as commonly believed to be the case in many vascular trees. On the basis of our findings it cannot be excluded that increased plasma catecholamine levels observed in senescence derive, in part, from perivascular sympathetic endings.

Development of the intrarenal vascular system of the puppy kidney.

This study investigates the development of the vascular system of the puppy kidney (1-21 days after birth) after preparing casts of the renal vessels. At two days, the intrarenal vascular system distal to the afferent arteriole is strikingly different than that of the adult. The glomeruli of the outer cortex consist of a single dilated vessel while those of the mid and inner cortex posses an increasingly larger number of capillary loops. The efferent arterioles vary greatly in appearance from outer to inner cortex. Those in the nephrogenic zone are characteristically short and narrow and join a larger venous vessel termined a sinusoidal capillary. An efferent system somewhat similar to that of the adult is seen in the mid and inner cortex. One of the most obvious differences noted between the puppy and adult kidney is the relative lack of peritubular capillary networks throughout the cortex of the puppy kidney. The puppy possesses large, irregular vessels termed sinusoidal capillaries. The most rudimentary sinusoids are found in the outer cortex with more mature vessels in the inner cortex. The vascular arrangement of the efferent arteriole and sinusoidal capillary appears as a post-glomerular shunt. Functionally, the shunt would direct blood flow away from the proximal tubule and thus could result in a low extraction ratio and Tm for secreted solutes.