Significance of renal hyaline arteriolosclerosis in focal segmental glomerulosclerosis

AC biosusceptometry and magnetic nanoparticles to assess doxorubicin-induced kidney injury in rats

Aim: This paper aims to investigate a doxorubicin (DOX) chronic kidney disease rat model using magnetic nanoparticles (MNPs) associated with the alternate current biosusceptometry (ACB) to analyze its different perfusion profiles in both healthy and DOX-injured kidneys. Materials & methods: We used the ACB to detect the MNP kidney perfusion in vivo. Furthermore, we performed biochemical and histological analyses, which sustained results obtained from the ACB system. We also studied the MNP biodistribution. Results: We found that DOX kidney injury alters the MNPs' kidney perfusion. These changes became more intense as the disease progressed. Moreover, DOX has an important effect on MNP biodistribution as the disease evolved. Conclusion: This study provides new applications of MNPs in nephrology, instrumentation, pharmacology, physiology and nanomedicine.

Association between serum adiponectin levels and arteriolosclerosis in IgA nephropathy patients

OBJECTIVE

Adiponectin has attracted great attention because of its anti-atherogenic properties; however, to date the relationship between serum adiponectin and arteriolosclerosis has not been reported. In our study, we aimed to examine whether or not serum adiponectin levels are associated with arteriolosclerosis in patients with IgA nephropathy which is the most common form of chronic glomerulonephritis.

MATERIALS AND METHODS

We enrolled 35 patients aged 35.0+/-14.6, who underwent renal biopsy from August 2004 to February 2006 in our hospital, and were confirmed to have IgA nephropathy. We examined serum adiponectin, high-sensitive C-reactive protein, total cholesterol and triglyceride level, urinary protein excretion, body mass index (BMI), and the presence of arteriolosclerosis in the renal specimens. Since the serum adiponectin level is strongly affected by renal function, we classified the patients by creatinine clearance.

RESULTS

Multiple regression analysis showed the associations of adiponectin with creatinine clearance (p<0.001), BMI (p<0.001), serum triglyceride (p=0.001) and urinary protein excretion (p=0.001). We observed a positive relation of adiponectin with urinary protein excretion and an inverse relation of adiponectin with creatinine clearance, serum triglyceride, and BMI. We could not detect any relation between the presence of arteriolosclerosis and adiponectin in the IgA nephropathy patients as a whole; however, in patients whose creatinine clearance was 90-120 ml/min/1.73 m2, the serum adiponectin level of patients with arteriolosclerosis was lower than in those without arteriolosclerosis (p=0.025).

CONCLUSION

The serum level of adiponectin was related to arteriolosclerosis in IgA nephropathy patients whose renal function was almost normal. Adiponectin may prevent renal arteriolosclerosis.

Morphometric study of arterioles and glomeruli in the aging kidney suggests focal loss of autoregulation

BACKGROUND

In the past it was widely assumed that hyaline afferent arteriolosclerosis was responsible for ischemic glomerulosclerosis in the aging and hypertensive kidney. However, glomerular lesions of focal segmental glomerulosclerosis are now recognized in essential hypertension. Experimentally, such lesions are associated with loss of autoregulation of blood flow and glomerular hyperperfusion, as well as initial glomerular hypertrophy. These observations challenge the notion of ischemia as a unitary explanation for glomerulosclerosis.

METHODS

A morphometric study was performed on normal portions of eight kidneys removed for tumors in aging, normotensive patients. Measurements were made of 126 pairs of afferent arterioles and their associated glomeruli. In addition, the amount of extracellular matrix (ECM) in the immediate periglomerular region was quantitated.

RESULTS

Afferent arterioles were divided into three types according to the presence or absence of hyaline deposits and whether these did or did not obstruct the lumen. Arterioles with nonobstructive hyaline deposits had lumens over twice as large as those without deposits (482 +/- 240 micro2 vs. 204 +/- 160 micro2, P=0.0000). Their associated glomeruli had significantly greater total capillary area, particularly the hilar capillaries (1276 +/- 797 micro2 vs. 667 +/- 492 micro2, P=0.002), but with larger individual capillaries elsewhere as well (P=0.03). Arterioles with obstructive deposits differed from those with nonobstructive deposits by their smaller lumens (P=0.001) and walls (P=0.004), with a higher proportion of ECM in the periglomerular region (P=0.001), all consistent with a later stage of lesion. Glomeruli were divided into four basic types: normal, hypertrophic, glomeruli with features of focal segmental glomerulosclerosis (FSGS-type), and ischemic. Compared to normal glomeruli, hypertrophic glomeruli were larger, with greater total capillary area (P=0.0005), particularly the hilar capillaries (P=0.0000), and larger capillaries in the remainder of the tuft (P=0.003), but showed no evident lesions. FSGS-type glomeruli were also larger, with larger hilar capillaries (P=0.0005), but showed an increase in ECM due to sclerotic lesions (P=0.004). The remaining capillaries showed an inverse relation with the amount of mesangial matrix, showing a spectrum of sizes from enlarged to shrunken. As anticipated, ischemic glomeruli were significantly smaller than normal ones in every parameter measured. There was a strong association between hypertrophic/FSGS-type glomeruli and hyaline arteriolosclerosis, found in 90.3% of such glomeruli, versus 29.1% for the remaining glomeruli (P=0.0001). The great majority of hyaline deposits were of the nonobstructive variety (86.2%), but some were obstructive (13.8%), particularly in FSGS-type glomeruli, consistent with a more advanced lesion.

CONCLUSIONS

We believe we have demonstrated in the aging kidney of humans the morphologic correlates of loss of autoregulation, occurring on a focal basis, with afferent arteriolar dilatation and increase in glomerular capillary size and subsequent focal segmental glomerulosclerosis. Hyaline arteriolosclerosis of the nonobstructive sort is strongly associated with these changes and may play a role in their pathogenesis.

Focal segmental glomerulosclerosis associated with mitochondrial cytopathy

BACKGROUND

The nonspecific lesion of focal segmental glomerulosclerosis (FSGS) can occur as a primary disease or in a variety of secondary settings. In mitochondrial cytopathies (MCs), the phenotypic expression of the disease depends on the degree of cellular dysfunction, and this correlates with the proportion of abnormal mitochondrial DNA in the cells and the dependence of tissues on oxidative metabolism. The most common renal manifestation in MCs is tubular dysfunction; little has been reported about glomerular diseases.

METHODS

Cases of four adult patients with FSGS and MC are reported. Routine histology and mitochondrial DNA analysis were carried out on renal biopsies.

RESULTS

Family history and clinical manifestations in the four patients with FSGS suggested a diagnosis of MC. An A3243G transition in the mitochondrial DNA tRNA(leu(UUR)) was found in lymphocytes and kidney. Glomerular lesions of FSGS were associated with unusual hyaline lesions, which appeared to represent individual myocyte necrosis in afferent arterioles and small arteries.

CONCLUSION

FSGS is a renal manifestation of MCs. The renal lesion can precede other manifestations of the genetic disease by many years. The striking arteriolar lesions in these cases may have resulted in glomerular hypertension and hyperperfusion, leading to secondary epithelial cell abnormalities and, ultimately, FSGS. However, primary epithelial cell dysfunction caused by mitochondrial defects could not be ruled out on morphological grounds. MCs should be considered in cases of so-called primary FSGS, particularly if there is a familial history of diabetes, neuromuscular disorders, or deafness.

Primary focal segmental glomerular sclerosis in adults: prognostic value of histologic variants

Primary focal segmental glomerular sclerosis (FSGS) is a clinicopathologic syndrome in which variable amounts of proteinuria are associated with the renal biopsy finding of segmental glomerular scarring in some, but not all, of the glomeruli. Additional histologic features have been described in FSGS, including the position of the scar relative to the vascular and tubular pole of the glomerulus, foam cells, hyalinosis, mesangial deposits of immunoglobulin M, diffuse mesangial hypercellularity, glomerular visceral epithelial cell hyperplasia and hypertrophy, and the extent of associated interstitial fibrosis and tubular atrophy. We performed a retrospective study on 81 patients with biopsy-proven, primary FSGS to determine whether any of the histologic features of FSGS correlated with renal function at the time of biopsy and the incidence of end-stage renal disease at follow-up. Sixty patients were nephrotic and 21 had nonnephrotic proteinuria. Only the degree of interstitial fibrosis correlated with the initial serum creatinine (r = 0.536) and none of the histologic features predicted the presence of nephrotic-range proteinuria at the time of biopsy. Segmental scars involved 21% +/- 14% of the glomeruli per biopsy specimen, but their position within the glomerulus was uniform in only 13% of the cases. Diffuse mesangial hypercellularity was present in 17% of the biopsy specimens, and glomerular epithelial cell lesions were present in 57% of the biopsy specimens. Multivariate analysis showed that only the degree of interstitial fibrosis predicted end-stage renal disease in all 81 patients and in the 60 patients with nephrotic-range proteinuria. The current data do not support different therapeutic approaches in primary FSGS based on histologic subtypes.

Renal pathology in pre-eclampsia

Pre-eclampsia affects the kidney both functionally and morphologically. Renal haemodynamics decrease and urinary protein excretion increases, in part due to lesions affecting the glomerulus, where a combination of changes produces a characteristic appearance and permits differentiation of pre-eclamptic nephropathy from other glomerular alterations associated with hypertension in pregnancy. In pre-eclampsia the glomerulus is diffusely enlarged and bloodless, due not to proliferation, but to hypertrophy of the intracapillary cells. These alterations, best described ultrastructurally, include hypertrophy of the cytoplasmic organelles in endothelial and occasionally mesangial cells, particularly the lysosomes, which undergo marked enlargement and vacuolization (due to accumulation of free neutral lipids). These reactive changes have been termed 'glomerular capillary endotheliosis'. Other lesions, observed occasionally, include subendothelial and mesangial electron-dense deposits, as well as interposition of mesangial cell cytoplasm or mesangial matrix along an otherwise normal basement membrane. Some investigators have described immunohistological findings (presence of IgM, IgG and fibrin) which they believe specific for pre-eclampsia, and others have claimed the disease may cause focal segmental glomerulosclerosis (FSGS). We believe the immunohistological findings are non-specific and insudative, and that FSGS when present predates the pre-eclamptic complication. Finally, the renal lesions appear fully reversible and the disease has no remote cardiorenal effects on its patients.

Glomerular hypertrophy and chronic renal failure in focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis evolves toward chronic renal failure (CRF) with a highly variable rate; in particular, a group of patients with a much more rapid decline of renal function has been described. The purpose of this study was to evaluate the usefulness of morphometry in identifying those cases with a faster decline in renal function. Two groups of patients have been studied: six with rapid evolution toward CRF (group 1) and six without reduction in renal function during a follow-up of up to 10 years (group 2). The results of the morphometric analysis of glomeruli were as follows: mean glomerular area: 30,550 +/- 5,259 microns2 (group 1) versus 22,667 +/- 5,078 microns2 (group 2) (P = 0.01); maximum glomerular area: 40,827 +/- 9,508 microns2 (group 1) versus 30,445 +/- 7,224 microns2 (group 2) (P = 0.02); mean glomerular diameter: 193.9 +/- 15.8 microns (group 1) versus 161.8 +/- 16.8 microns (group 2) (P = 0.003); and caliper diameter: 328.6 +/- 20.6 microns (group 1) versus 260.6 +/- 36 microns (group 2) (P = 0.001). Values of body surface area were not different between the two groups (1.85 +/- 0.34 m2 v 1.6 +/- 0.13 m2) (P = NS). Our results suggest that glomerular hypertrophy in the course of focal segmental glomerulosclerosis is correlated with a faster decline toward CRF. It might represent a compensatory hypertrophy that would immediately precede a rapid decline in renal function or it might be the expression of the preexisting condition (meganephronia), which predisposes to the development of CRF.

Lipoprotein metabolism and renal failure

Lipoprotein metabolism is altered in the majority of patients with renal insufficiency and renal-failure, but may not necessarily lead to hyperlipidemia. The dyslipoproteinemia of renal disease has characteristic abnormalities of the apolipoprotein (apo) profile and lipoprotein composition. It develops during the asymptomatic stages of renal insufficiency and becomes more pronounced as renal failure advances. The qualitative characteristics of renal dyslipoproteinemia are not modified substantially by dialysis treatment. Patients with chronic renal disease may therefore be exposed to dyslipoproteinemia for long periods of time. The characteristic plasma lipid abnormality is a moderate hypertriglyceridemia. The alterations of lipoprotein metabolism affect both the apoB-containing very low-density and intermediate-density, and low-density lipoproteins and the apoA-containing high-density lipoproteins. The main underlying abnormality of lipoprotein transport is a decreased catabolism of the apoB-containing lipoproteins caused by decreased activity of lipolytic enzymes and altered lipoprotein composition. There is an increase of intact or partially metabolized, triglyceride-rich, apoB-containing lipoproteins with a disproportionate elevation of apoC-III and, to a lesser extent, apoE, resulting in a marked increase of the intermediate-density lipoproteins and an enrichment of triglycerides, apoC-III, and apoE in the low-density lipoproteins. In high-density lipoproteins there are decreases in the concentrations of cholesterol, apolipoproteins A-I and A-II, and the high-density lipoprotein-2 to high-density lipoprotein-3 ratio. These abnormalities result in a characteristic decrease of the apoA-I to apoC-III ratio and anti-atherogenic index apoA-I/apoB. The pathophysiologic links between the renal insufficiency and the abnormalities of lipoprotein transport are still poorly defined. Changes in the action of insulin on lipolytic enzymes, possibly mediated via increased levels of parathyroid hormone, have been suggested to play a contributory role. The clinical consequences of a defective lipoprotein transport may be related to the atherogenic character of lipoprotein abnormalities. Renal dyslipoproteinemia may contribute to the development of atherosclerotic vascular disease and progression of glomerular and tubular lesions with subsequent deterioration of renal function. Dietary and/or pharmacologic intervention may ameliorate the uremic dyslipoproteinemia, but the long-term clinical effects of such treatment have yet to be established.

Experimental ablation nephropathy. Fine structure, morphometry, cell membrane epitopes, glomerular polyanion and effect of subsequent transplantation

The subtotal (5/6) nephrectomy performed in 23 adult female rats induced severe hypertrophy of residual parenchyma with interstitial fibrosis, tubular dilatation, and focal and segmental glomerulosclerosis (FSG). This ablation nephropathy (AbN) caused proteinuria, progressive renal failure, and hypertension. The extent of FSG was assessed by semiquantitative scoring. The ultrastructure revealed widespread foot process fusion, many dense cytoplasmic inclusions in podocytes, and degenerative changes or disruption of mesangium with glomerular "microcysts". Numerous granular deposits of rat Ig were seen in the glomeruli but a short praeterminal i.v. load by heat-aggregated human Ig did not alter the morphology of AbN and produced discrete and inconstant glomerular deposits. Similarly an i.v. injection of protamine and heparin generated protamine-heparin complexes seen in various layers of glomerular capillary wall, similar to those found previously in normal rats. AbN displayed a partial irregular depletion of polyanion sites reactive with polyethylenimine in lamina rara externa. A significant increase in both glomerular and interstitial Ia+ cells and a marked predominance of W3/25+ cells in the interstitial infiltrates were documented by immunohistochemistry in the remnant kidneys. Both AbN and FSG could be largely corrected (or prevented?) by subsequent syngeneic renal transplantation (TPL; 6 animals). On the other hand a severe AbN was found in two post-ablation residues after unsuccessful TPL with graft necrosis or sclerosis.--AbN has some analogies to various chronic human nephropathies (e.g. FSG) and may explain their progression to the terminal failure. Degenerative and finally destructive mesangial lesion seems to be of prime importance in AbN.

Renal pathology in pre-eclampsia

Pre-eclampsia affects the kidney both functionally and morphologically. Renal haemodynamics decrease and urinary protein excretion increases, in part due to lesions affecting the glomerulus, where a combination of changes produces a characteristic appearance and permits differentiation of pre-eclamptic nephropathy from other glomerular alterations associated with hypertension in pregnancy. In pre-eclampsia the glomerulus is diffusely enlarged and bloodless, due not to proliferation, but to hypertrophy of the intracapillary cells. These alterations, best described ultrastructurally, include hypertrophy of the cytoplasmic organelles in endothelial and occasionally mesangial cells, particularly the lysosomes, which undergo marked enlargement and vacuolization (due to accumulation of free neutral lipids). These reactive changes have been termed 'glomerular capillary endotheliosis'. Other lesions, observed occasionally, include subendothelial and mesangial electron-dense deposits, as well as interposition of mesangial cell cytoplasm or mesangial matrix along an otherwise normal basement membrane. Some investigators have described immunohistologic findings (presence of IgM, IgG and fibrin) which they believe specific for pre-eclampsia, and others have claimed the disease may cause focal segmental glomerulosclerosis (FSGS). We believe the immunohistologic findings are non-specific and insudative, and that FSGS when present predates the pre-eclamptic complication. Finally, the renal lesions appear fully reversible and the disease has no remote cardiorenal effects on its patients.