Thrombospondin 1 precedes and predicts the development of tubulointerstitial fibrosis in glomerular disease in the rat

Thrombospondin 1 precedes and predicts the development of tubulointerstitial fibrosis in glomerular disease in the rat. Tubulointerstitial fibrosis is one of the most important histologic features that predicts progression in kidney disease. Thrombospondin 1 is an extracellular matrix protein that can activate latent TGF-β, a cytokine implicated in the pathogenesis of tubulointerstitial fibrosis. We examined the expression of thrombospondin 1 in several animal models of glomerulonephritis (anti-Thy1 model, aminonucleoside nephrosis, passive Heymann nephritis) that are associated with tubulointerstitial disease. Thrombospondin 1 mRNA and protein were transiently increased in tubular cells, myofibroblasts and some macrophages in areas of tubulointerstitial injury. Thrombospondin 1 expression always preceded the development of tubulointerstitial fibrosis, and correlated quantitatively and spatially with the later development of interstitial fibrosis. Thrombospondin 1 expression predicted the severity of tubulointerstitial fibrosis better than the degree of macrophage or myofibroblast accumulation. Thrombospondin 1 expression was associated with increased expression and activation of TGF-β1 and decreased expression of LAP-TGF-β in areas of tubulointerstitial injury. We conclude that thrombospondin 1 is an early marker predicting the development of tubulointerstitial kidney disease. De novo expression of thrombospondin 1 is associated and colocalized with increased expression of TGF-β1 and decreased expression of LAP-TGF-β during the development of tubulointerstitial disease in vivo. These data are consistent with the possibility that thrombospondin 1 may be an endogenous activator of TGF-β

The plasma membrane-actin linking protein, ezrin, is a glomerular epithelial cell marker in glomerulogenesis, in the adult kidney and in glomerular injury

The plasma membrane-actin linking protein, ezrin, is a glomerular epithelial cell marker in glomerulogenesis, in the adult kidney and in glomerular injury.BackgroundEzrin belongs to a family of plasma membrane-cytoskeleton linking, actin binding proteins (Ezrin-radixin-Moesin family) involved in signal transduction, growth control, cell-cell adhesion, and microvilli formation.MethodsThe expression of ezrin was examined in glomerular cells in culture, during kidney development, in the mature kidney, and in five different experimental kidney disease models in the rat.ResultsEzrin was specifically expressed in glomerular epithelial cells in developing glomeruli in mature glomeruli and in glomerular epithelial cells in culture. Distinct from its other family members, moesin and radixin, which are predominantly expressed in glomerular endothelial and mesangial areas, ezrin protein (by immunohistochemistry) was specifically and exclusively modulated during podocyte injury and regeneration. Ezrin immunohistochemistry was able to visualize cell body attenuation, pseudocysts, and in particular vacuolation of injured podocytes, a feature that usually has to be identified at the ultrastructural level, and was strikingly increased in binucleated podocytes or podocytes that were partially or completely detached from the underlying GBM (frequently also binucleated). Infiltrating macrophages also express ezrin, but can easily be differentiated from podocytes by their round shape and higher level of expression.ConclusionsEzrin likely has a role in the cytoskeletal organization, such as reassembling of actin filaments accompanying podocyte injury and regeneration. Since suitable light microscopic markers for the identification of glomerular epithelial cells are rare, ezrin may also be a useful marker for podocytes in normal and injured glomeruli

De novo glomerular osteopontin expression in rat crescentic glomerulonephritis

De novo glomerular osteopontin expression in rat crescentic glomerulonephritis. Osteopontin (OPN) is a secreted acidic glycoprotein that has potent monocyte chemoattractant and adhesive properties. Up-regulation of tubular OPN expression is thought to promote interstitial macrophage infiltration in experimental nephritis; however, the role of OPN in glomerular lesions, particularly crescent formation, is unknown. The present study used Northern blotting, in situ hybridization and immunohistochemistry to examine OPN expression in a rat model of accelerated anti-GBM glomerulonephritis. Osteopontin mRNA and protein is expressed by some parietal epithelial cells, thick ascending limbs of Henle and medullary tubules and collecting ducts in normal rat kidney. De novo OPN mRNA and protein expression was evident in glomerular visceral and parietal epithelial cells in anti-GBM glomerulonephritis. Glomerular OPN expression preceded and correlated with macrophage infiltration in the development of hypercellularity, focal and segmental lesions and, notably, crescent formation. There was marked up-regulation of OPN expression by tubular epithelial cells that also preceded and correlated with interstitial macrophage (r = 0.93, P < 0.001) and T-cell infiltration (r = 0.85, P < 0.001). Both glomerular and tubular OPN expression correlated significantly with proteinuria (P < 0.001) and a reduction in creatinine clearance (P < 0.01). In addition, double immunohistochemistry showed co-expression of osteopontin and one of its ligands, CD44, in intrinsic renal cells. CD44 and OPN expression by parietal epithelial cells was evident in crescent formation, while virtually all OPN-positive tubules expressed CD44. Infiltrating macrophages and T-cells were CD44-positive, but only a small proportion of T-cells and few macrophages showed OPN expression. Interestingly, strong OPN mRNA and protein expression was seen in macrophage multinucleated giant cells. In summary, this study suggests that OPN promotes macrophage and T-cell infiltration in the development of renal lesions in rat anti-GBM glomerulonephritis, including glomerular crescent and multinucleated giant cell formation

SPARC is expressed in renal interstitial fibrosis and in renal vascular injury

SPARC is expressed in renal interstitial fibrosis and in renal vascular injury. Tubulointerstitial inflammation and fibrosis are critical determinants for renal function and prognosis in a variety of human nephropathies. Yet, the pathophysiology of the injury remains obscure. We investigated the expression of SPARC (secreted protein acidic and rich in cysteine) by immunohistochemistry and in situ hybridization in experimental models characterized by tubulointerstitial fibrosis and matrix expansion in rats. SPARC is a secreted glycoprotein that has been demonstrated to affect cellular interaction with matrix proteins, modulate cell proliferation, bind to and/or inhibit growth factors such as PDGF and bFGF, and regulate angiogenesis. Interstitial expression of SPARC was most prominent in passive Heyman nephritis (PHN), chronic cyclosporine A (CsA) nephropathy, and the remnant kidney model and, to a lesser extent, in angiotensin II (Ang II)-infused animals. SPARC protein and mRNA were substantially increased at sites of tubulointerstitial fibrosis/matrix expansion. In the PHN model, SPARC protein was expressed by interstitial fibroblasts that also produced α-smooth muscle actin (“myofibroblasts”) and correlated both temporally (r = 0.97) and spatially with sites of type I collagen deposition. Interstitial cell proliferation preceded the development of interstitial fibrosis, and maximal SPARC expression (d15) coincided with the initial decline in interstitial proliferation. In the Ang II-infusion model, which is characterized by arteriolopathy and tubulointerstitial injury, an increase in SPARC protein and mRNA was also seen in injured blood vessels. SPARC was shown to be expressed by vascular smooth muscle cells and also by cells in the adventitia of hypertrophied arteries. In summary, SPARC was transiently expressed by interstitial fibroblasts at sites of tubulointerstitial injury and fibrosis, and by smooth muscle cells and cells in the adventitia of injured arteries in the Ang II-model. In addition to its proposed role in extracellular matrix deposition, the antiproliferative properties of SPARC might contribute to the resolution of interstitial fibroblast proliferation in the PHN model

Differential expression of transforming growth factor-β isoforms and receptors in experimental membranous nephropathy

Transforming growth factor-β1 stimulates matrix production by glomerular mesangial and epithelial cells. In membranous nephropathy (MN) overproduction of matrix by glomerular epithelial cells (GEC) is believed to be responsible for glomerular basement membrane thickening and spikes. We studied experimental MN in rats (passive Heymann nephritis, PHN) at 5, 10 and 30 days. PHN rats exhibited a marked increase in GEC immunostaining for TGF-β2 at all time points. TGF-β3 staining was increased at day 10 only, and TGF-β1 was unchanged. Glomerular mRNA for TGF-β2 and -β3 was increased by day 5 when urine protein increased, whereas TGF-β1 was not. TGF-β2 bioactivity was increased at day 5. There was also a marked increase in GEC immunostaining for TGF-β receptor type I (TβIR) and TGF-β receptor type II (TβIIR) at all time points in PHN. mRNA levels for both receptors increased at day 5. Increases in protein expression and mRNA levels for the TGF-β2 and -β3 isoforms, and TβIR and TβRII were prevented by complement depletion. We conclude that complement-mediated injury to the GEC in vivo is associated with the up-regulation of TGF-β2 and -β3 isoforms, an increase in TGF-β2 bioactivity, and an increase in TβRI and TβRII expression. This contrasts with changes in TGF-β1 reported in mesangial disease, suggesting that TGF-β2 and -β3 may be important in diseases of the GEC. The differential expression of TGF-β isoforms and receptors may be important determinants of the GEC response to injury

Tree-rings reveal two strong solar proton events in 7176 and 5259 BCE

The Sun sporadically produces eruptive events leading to intense fluxes of solar energetic particles (SEPs) that dramatically disrupt the near-Earth radiation environment. Such events have been directly studied for the last decades but little is known about the occurrence and magnitude of rare, extreme SEP events. Presently, a few events that produced measurable signals in cosmogenic radionuclides such as 14C, 10Be and 36Cl have been found. Analyzing annual 14C concentrations in tree-rings from Switzerland, Germany, Ireland, Russia, and the USA we discovered two spikes in atmospheric 14C occurring in 7176 and 5259 BCE. The ~2% increases of atmospheric 14C recorded for both events exceed all previously known 14C peaks but after correction for the geomagnetic field, they are comparable to the largest event of this type discovered so far at 775 CE. These strong events serve as accurate time markers for the synchronization with floating tree-ring and ice core records and provide critical information on the previous occurrence of extreme solar events which may threaten modern infrastructure

Extensive Microhemorrhages of the Cerebellar Peduncles After High-Altitude Cerebral Edema

Extensive microhemorrhages of the cerebellar peduncles after high-altitude cerebral edema. High Alt Med Biol. 18:182-184, 2017.-Neuromagnetic resonance imaging (MRI) of subjects who suffered from high-altitude cerebral edema (HACE) typically shows cerebral microhemorrhages (MH) of the corpus callosum, in particular the splenium, and supratentorial white matter. This is a case report of a 43-year-old male, who suffered from unusually prolonged severe ataxia and amnesia after having been rescued during the ascent to Mount Everest at 6400 m. MRI of the brain 63 days after the incident showed the typical MH in the corpus callosum, but, in addition, extensive MH were found in the middle cerebellar peduncles. These infratentorial MH might reflect the pronounced atactic gait disorder. This case describes the first HACE-associated MH in the cerebellar peduncles in a high-altitude mountaineer indicating a potential vulnerability of infratentorial brain areas to hypobaric hypoxia

Morphological Brain Changes after Climbing to Extreme Altitudes-A Prospective Cohort Study.

BACKGROUND Findings of cerebral cortical atrophy, white matter lesions and microhemorrhages have been reported in high-altitude climbers. The aim of this study was to evaluate structural cerebral changes in a large cohort of climbers after an ascent to extreme altitudes and to correlate these findings with the severity of hypoxia and neurological signs during the climb. METHODS Magnetic resonance imaging (MRI) studies were performed in 38 mountaineers before and after participating in a high altitude (7126m) climbing expedition. The imaging studies were assessed for occurrence of new WM hyperintensities and microhemorrhages. Changes of partial volume estimates of cerebrospinal fluid, grey matter, and white matter were evaluated by voxel-based morphometry. Arterial oxygen saturation and acute mountain sickness scores were recorded daily during the climb. RESULTS On post-expedition imaging no new white matter hyperintensities were observed. Compared to baseline testing, we observed a significant cerebrospinal fluid fraction increase (0.34% [95% CI 0.10-0.58], p = 0.006) and a white matter fraction reduction (-0.18% [95% CI -0.32--0.04], p = 0.012), whereas the grey matter fraction remained stable (0.16% [95% CI -0.46-0.13], p = 0.278). Post-expedition imaging revealed new microhemorrhages in 3 of 15 climbers reaching an altitude of over 7000m. Affected climbers had significantly lower oxygen saturation values but not higher acute mountain sickness scores than climbers without microhemorrhages. CONCLUSIONS A single sojourn to extreme altitudes is not associated with development of focal white matter hyperintensities and grey matter atrophy but leads to a decrease in brain white matter fraction. Microhemorrhages indicative of substantial blood-brain barrier disruption occur in a significant number of climbers attaining extreme altitudes

Delayed Graft Function and Cast Nephropathy Associated with Tacrolimus Plus Rapamycin Use

Delayed graft function (DGF) occurs in 15 to 25% (range, 10 to 62%) of cadaveric kidney transplant recipients and up to 9% of living donor recipients. In addition to donor, recipient, and procedural factors, the choice of immunosuppression may influence the development of DGF. The impact of immunosuppression on DGF was studied. The frequency of DGF was evaluated in first cadaveric or living donor kidney allograft recipients (n = 144) transplanted at the University of Washington from November 1999 through September 1, 2001. Donor, recipient, and procedural factors, as well as biopsy results, were compared between patients who developed DGF and those who did not. DGF was more common in patients treated with rapamycin than without (25% versus 8.9%, P = 0.02) and positively correlated with rapamycin dose (P = 0.008). In those developing DGF, the duration of posttransplant dialysis increased with donor age (P = 0.003) but decreased with mycophenolate mofetil use (P = 0.01). All biopsies during episodes of DGF demonstrated changes of acute tubular injury. Of the patients with tubular injury, 12 treated with rapamycin and tacrolimus developed intratubular cast formation indistinguishable from myeloma cast nephropathy. Histologic, immunohistochemical, and ultrastructural studies indicated that these casts were composed at least in part of degenerating renal tubular epithelial cells. These findings suggest that rapamycin therapy exerts increased toxicity on tubular epithelial cells and/or retards healing, leading to an increased incidence of DGF. Additionally, rapamycin treatment combined with a calcineurin inhibitor may lead to extensive tubular cell injury and death and a unique form of cast nephropathy