Slim ruimtegebruik: hoe kunnen we meer doen met minder ruimte?

Meer dan 25 procent van de Vlaamse ruimte is bebouwd of verhard en prognoses geven aan dat Vlaanderen 30 tot 50 procent verhard zou worden tegen 2050 (Poelmans en Van Rompaey, 2009; Poelmans et al., 2010). De ruimte in Vlaanderen is echter niet oneindig beschikbaar. Willen we verstening een halt toeroepen, dan is een meer duurzame ruimtelijke ontwikkeling noodzakelijk met (her)gebruik van reeds ontwikkelde structuren en gebieden. Dit artikel stelt de resultaten voor van een onderzoek in opdracht van de Vlaamse Overheid waarin aangetoond wordt dat hergebruik een methode kan zijn om de toenemende druk op greenfields -en dus het aansnijden van nieuwe ruimte- te verminderen

Dedifferentiation and aberrations of the endolysosomal compartment characterize the early stage of nephropathic cystinosis

Nephropathic cystinosis, a lysosomal storage disease caused by mutations in the CTNS gene encoding the lysosomal cystine transporter cystinosin, is characterized by generalized proximal tubule (PT) dysfunction that progresses, if untreated, to end-stage renal disease. The pathogenesis of defective PT cellular transport in nephropathic cystinosis remains unclear. We characterized a recently generated line of C57BL/6 Ctns mice and analyzed endocytic uptake, lysosome function, and dedifferentiation and proliferation markers using primary cultures of PT epithelial cells derived from Ctns−/− and Ctns+/+ littermates. Metabolic studies revealed that Ctns−/− mice show a progressive PT dysfunction characterized by low-molecular-weight (LMW) proteinuria, glucosuria and phosphaturia, before structural damage and in the absence of renal failure. These changes are related to decreased expression of the multi-ligand receptors megalin and cubilin and to increased dedifferentiation (ZONAB transcription factor) and proliferation (PCNA and Cyclin D1) rates. Studies on PT cells derived from Ctns−/− kidneys confirmed cystine overload, with accumulation of enlarged, dysfunctional lysosomes and reduced expression of endocytic receptors reflected by decreased uptake of specific ligands. These changes were related to a loss of integrity of tight junctions with a nuclear translocation of ZONAB and increased proliferation, as observed in Ctns−/− kidneys. These data reveal that the absence of cystinosin in PT cells triggers aberrations of the endolysosomal compartment, transport defects and an abnormal transcription program in the early stage of nephropathic cystinosis. Insights into the early manifestations of cystinosis may offer new targets for intervention, before irreversible renal damag

Decreased renal accumulation of aminoglycoside reflects defective receptor-mediated endocytosis in cystic fibrosis and Dent's disease

The clinical use of aminoglycoside (AG) antibiotics is limited by their renal toxicity, which is caused by drug accumulation in proximal tubule (PT) cells. Clinical studies reported that renal clearance of AG is enhanced in cystic fibrosis (CF) patients, which might reflect the role of CFTR in PT cell endocytosis. In order to assess the role of chloride transporters on the renal handling of AG, we investigated gentamicin uptake and renal accumulation in mice lacking functional CFTR (Cftr ∆F/∆F) or knock-out for the Cl−/H+ exchanger ClC-5 (Clcn5 Y/− ). The latter represent a paradigm of PT dysfunction and defective receptor-mediated endocytosis. As compared with controls, Cftr ∆F/∆F and Clcn5 Y/− mice showed a 15% to 85% decrease in gentamicin accumulation in the kidney, respectively, in absence of renal failure. Studies on primary cultures of Cftr ∆F/∆F and Clcn5 Y/− mouse PT cells confirmed the reduction in gentamicin uptake, although colocalization with endosomes and lysosomes was maintained. Quantification of endocytosis in PT cells revealed that gentamicin, similar to albumin, preferentially binds to megalin. The functional loss of ClC-5 or CFTR was reflected by a decrease of the endocytic uptake of gentamicin, with a more pronounced effect in cells lacking ClC-5. These results support the concept that CFTR, as well as ClC-5, plays a relevant role in PT cell endocytosis. They also demonstrate that the functional loss of these two chloride transporters is associated with impaired uptake of AG in PT cells, reflected by a decreased renal accumulation of the dru

High-dose steroid treatment increases free water transport in peritoneal dialysis patients

The water channel aquaporin-1 (AQP1) is the molecular counterpart of the ultrasmall pore that mediates free water transport during peritoneal dialysis (PD). Proof-of-principle studies performed in rats have shown that treatment with corticosteroids upregulates the expression of AQP1 in the peritoneal capillaries, causing a significant increase in free water transport. Whether such a beneficial effect could be observed in end-stage renal disease patients treated by PD remains unknown. Peritoneal transport parameters were evaluated in three patients on PD, shortly before and after living-donor renal transplantation and treatment with high-dose methylprednisolone (1.0-1.2 g/m2). As compared with pre-transplantation values, the post-transplantation test revealed an ∼2-fold increase in the sodium sieving and ultrasmall pore ultrafiltration volume, suggesting an effect on AQP1 water channels. In contrast, there was no change in the parameters of small solute transport. The direct involvement of AQP1 in these changes is suggested by the expression of glucocorticoid receptors in the human peritoneum and the presence of conserved glucocorticoid response elements in the promoter of the human AQP1 gen

Corrosion protection of Cu by atomic layer deposition

Atomic layer deposition (ALD) is a vapor phase technique that is able to deposit uniform, conformal thin films with an excellent thickness control at the atomic scale. 18 nm thick Al2O3 and TiO2 coatings were deposited conformaly and pinhole-free onto micrometer-sized Cu powder, using trimethylaluminum and tetrakis(dimethylamido)titanium(IV), respectively, as a precursor and de-ionized water as a reactant. The capability of the ALD coating to protect the Cu powder against corrosion was investigated. Therefore, the stability of the coatings was studied in solutions with different pH in the range of 0-14, and in situ raman spectroscopy was used to detect the emergence of corrosion products of Cu as an indication that the protective coating starts to fail. Both ALD coatings provide good protection at standard pH values in the range of 5-7. In general, the TiO2 coating shows a better barrier protection against corrosion than the Al2O3 coating. However, for the most extreme pH conditions, pH 0 and pH 14, the TiO2 coating starts also to degrade. Published by the AVS

The inositol Inpp5k 5-phosphatase affects osmoregulation through the vasopressin-aquaporin 2 pathway in the collecting system

Inositol Inpp5k (or Pps, SKIP) is a member of the inositol polyphosphate 5-phosphatases family with a poorly characterized function in vivo. In this study, we explored the function of this inositol 5-phosphatase in mice and cells overexpressing the 42-kDa mouse Inpp5k protein. Inpp5k transgenic mice present defects in water metabolism characterized by a reduced plasma osmolality at baseline, a delayed urinary water excretion following a water load, and an increased acute response to vasopressin. These defects are associated with the expression of the Inpp5k transgene in renal collecting ducts and with alterations in the arginine vasopressin/aquaporin-2 signalling pathway in this tubular segment. Analysis in a mouse collecting duct mCCD cell line revealed that Inpp5k overexpression leads to increased expression of the arginine vasopressin receptor type 2 and increased cAMP response to arginine vasopressin, providing a basis for increased aquaporin-2 expression and plasma membrane localization with increased osmotically induced water transport. Altogether, our results indicate that Inpp5k 5-phosphatase is important for the control of the arginine vasopressin/aquaporin-2 signalling pathway and water transport in kidney collecting duct

A primary culture system of mouse thick ascending limb cells with preserved function and uromodulin processing

The epithelial cells lining the thick ascending limb (TAL) of the loop of Henle perform essential transport processes and secrete uromodulin, the most abundant protein in normal urine. The lack of differentiated cell culture systems has hampered studies of TAL functions. Here, we report a method to generate differentiated primary cultures of TAL cells, developed from microdissected tubules obtained in mouse kidneys. The TAL tubules cultured on permeable filters formed polarized confluent monolayers in ∼12days. The TAL cells remain differentiated and express functional markers such as uromodulin, NKCC2, and ROMK at the apical membrane. Electrophysiological measurements on primary TAL monolayers showed a lumen-positive transepithelial potential (+9.4 ± 0.8mV/cm2) and transepithelial resistance similar to that recorded in vivo. The transepithelial potential is abolished by apical bumetanide and in primary cultures obtained from ROMK knockout mice. The processing, maturation and apical secretion of uromodulin by primary TAL cells is identical to that observed in vivo. The primary TAL cells respond appropriately to hypoxia, hypertonicity, and stimulation by desmopressin, and they can be transfected. The establishment of this primary culture system will allow the investigation of TAL cells obtained from genetically modified mouse models, providing a critical tool for understanding the role of that segment in health and disease

Cell therapy for cystinosis

In the September 2009 issue of Blood, Syres et al. [1] report on syngeneic bone marrow cell (BMC) and haematopoietic stem cell (HSC) therapy as a successful treatment in a mouse model of cystinosis, an autosomal recessive metabolic disease caused by a defect in the transport of cystine across the lysosomal membrane. The accumulation of cystine crystals in lysosomes leads to a multi-organ dysfunction including proximal tubulopathy and renal failure, corneal deposits, myopathy and central nervous system defects. By using Ctns knock-out (Ctns(-/-)) mice as a model for cystinosis, Syres et al. show that BMC transplantation leads to a major reduction of cystine content in all tissues tested, reflected by a significant attenuation of the development and progression of kidney injury and reduction in the number of mice with corneal cystine crystals. These changes were correlated with the engraftment of donor BMC producing a functional cystine transporter in the tissues tested. The transplantation of mouse HSC had the same therapeutic effect than whole BMC in this model, which is important as such HSC can readily be isolated from peripheral blood in humans. This work suggests that BMC or HSC transplantation is a potential treatment for cystinosis and emphasizes a potential treatment for cystinosis and other renal tubular disorders