Seymour Rosen

Podocyte-Specific Loss of Functional MicroRNAs Leads to Rapid Glomerular and Tubular Injury

MicroRNAs (miRNAs) are in a class of endogenous, small, noncoding RNAs that exert their effects through posttranscriptional repression of specific target mRNAs. Although miRNAs have been implicated in the regulation of diverse biologic processes, little is known about miRNA function in the kidney. Here, mice lacking functional miRNAs in the developing podocyte were generated through podocyte-specific knockout of Dicer, an enzyme required for the production of mature miRNAs (Nphs2-Cre; Dicer(flx/flx)). Podocyte-specific loss of miRNAs resulted in significant proteinuria by 2 wk after birth, rapid progression of marked glomerular and tubular injury beginning at 3 wk, and death by 4 wk. Expression of the slit diaphragm proteins nephrin and podocin was decreased, and expression of the transcription factor WT1 was relatively unaffected. To identify miRNA-mRNA interactions that contribute to this phenotype, we profiled the glomerular expression of miRNAs; three miRNAs expressed in glomeruli were identified: mmu-miR-23b, mmu-miR-24, and mmu-miR-26a. These results suggest that miRNA function is dispensable for the initial development of glomeruli but is critical to maintain the glomerular filtration barrier.

Port wine stains and the response to argon laser therapy: successful treatment and the predictive role of color, age, and biopsy.

To date, no criteria exist for anticipating the response of a port wine stain to argon laser therapy. In an effort to determine such predictive factors, the preceding study was undertaken. Sixty-two patients, ages 7 to 66 years, with port wine stains were biopsied, had a small test area treated, and were evaluated after 4 months. A desirable result, defined by marked lightening of the lesion without scarring, occurred in 73 percent of the patients. Factors favoring a desirable result included age greater than 37 years, purple color, fraction of dermis occupied by vessels greater than 5 percent, mean vessel area greater than 2500 micrometers2, and percent of vessels containing erythrocytes greater than 15 percent. Furthermore, the degree of color change strongly correlated with these indices. Factors indicating an undesirable result included age less than 17 years, pink color, vascular area less than 2 percent, mean vessel area less than 1500 micrometers2, and percent of vessels containing erythrocytes less than 3 percent, Thus, if appropriate clinical and histological criteria are met port wine stains can successfully treated with argon laser therapy.

Extended Prostate Needle Biopsy Improves Concordance Of Gleason Grading Between Prostate Needle Biopsy And Radical Prostatectomy

PURPOSE We examined the concordance of Gleason scores in prostate needle biopsy specimens and the corresponding radical retropubic prostatectomy specimens in a cohort of patients grouped according to the number of cores obtained during diagnostic needle biopsy. MATERIALS AND METHODS We reviewed clinical and pathological data on a cohort of 466 men diagnosed with localized prostate cancer by needle biopsies who underwent radical retropubic prostatectomy between January 1, 1990 and July 31, 2001. Two study groups were identified, including 126 patients diagnosed with prostate cancer by extended needle biopsies (10 or more cores) and 340 diagnosed with cancer by nonextended needle biopsies (9 or fewer cores). Mean age was 60 years and median prostate specific antigen was 5.8 ng./ml. The median number of cores in the extended and nonextended biopsy groups was 12 and 6, respectively. The concordance of Gleason score in the needle biopsy and prostatectomy specimens was compared and correlated with the number of cores on needle biopsy. RESULTS In the whole cohort 311 patients (67%) had identical Gleason scores on the needle biopsy and prostatectomy specimens, while 53 (11%) were over graded and 102 (22%) were under graded on needle biopsy. In patients who underwent extended needle biopsies the accuracy rate for Gleason scoring was 76% with 10% over and 14% under graded. The highest accuracy rates were in patients with 13, 14 and 16 cores (89%, 87% and 100%, respectively). No patients in the extended needle biopsy group had a discrepancy of more than 2 Gleason units in grade in the biopsy and surgical specimens. In those who underwent nonextended needle biopsies the accuracy rate for Gleason scoring was 63% with 12% over and 25% under graded. There were significantly different rates of accuracy (p = 0.008) and under grading (p = 0.01) in the 2 needle biopsy groups. Patients with a needle biopsy Gleason score of less than 7 had significantly higher concordance with the prostatectomy Gleason score when extended biopsies were done compared with nonextended biopsies (p = 0.001). CONCLUSIONS Prostate cancer grading by extended needle biopsy is a better predictor of the final Gleason score than nonextended needle biopsy, as determined by radical prostatectomy histological evaluation. Therefore, extended prostate needle biopsy provides better guidance to determine the appropriate treatment in patients with prostate cancer.

Reactive Oxygen Species and the Pathogenesis of Radiocontrast-Induced Nephropathy

Experimental findings in vitro and in vivo illustrate enhanced hypoxia and the formation of reactive oxygen species (ROS) within the kidney following the administration of iodinated contrast media, which may play a role in the development of contrast media-induced nephropathy. Clinical studies indeed support this possibility, suggesting a protective effect of ROS scavenging or reduced ROS formation with the administration of N-acetyl cysteine and bicarbonate infusion, respectively. Furthermore, most risk factors, predisposing to contrast-induced nephropathy are prone to enhanced renal parenchymal hypoxia and ROS formation.In this review, the association of renal hypoxia and ROS-mediated injury is outlined. Generated during contrast-induced renal parenchymal hypoxia, ROS may exert direct tubular and vascular endothelial injury and might further intensify renal parenchymal hypoxia by virtue of endothelial dysfunction and dysregulation of tubular transport. Preventive strategies conceivably should include inhibition of ROS generation or ROS scavenging.

Renal Parenchymal Hypoxia, Hypoxia Response and the Progression of Chronic Kidney Disease

Renal parenchymal hypoxia, documented under a variety of clinical conditions, conceivably contributes to the progression chronic kidney disease. In this review, normal physiologic medullary hypoxia and abnormal profiles of renal pO(2) in chronic kidney diseases are presented, and the mechanisms leading to anomalous renal tissue oxygenation are discussed. Direct measurements of pO(2) with oxygen electrodes, immunostaining with pimonidazole (which binds to regions with very low pO(2)), or the detection of hypoxia-inducible factor (HIF)-alpha (which accumulates in hypoxic regions, initiating hypoxia-adaptive responses), all serve to detect the distribution and extent of renal parenchymal hypoxia under experimental settings. The use of BOLD MRI as a noninvasive tool, detecting deoxygenated hemoglobin in hypoxic renal tissues, has evolved from experimental settings to human studies. All these modalities indicate that abnormal renal oxygenation develops under conditions such as chronic glomerular, tubulointerstitial or renovascular disease, in diabetes, hypertension, aging, renal hypertrophy, anemia or obstructive uropathy. Abnormal renal tissue hypoxia modifies the pattern of regional gene expression, evoking a host of adaptive and renoprotective pathways (such as HIF-mediated erythropoietin or heme-oxygenase-1), in parallel with the induction of potentially harmful mediators that participate in the progression of chronic kidney injury. Slowing the progression of chronic kidney disease may be achieved by a better understanding of these parallel processes and the accomplishment of a selective control of such protective and maladaptive responses.

Chilling Port Wine Stains Improves the Response to Argon Laser Therapy

Twenty-three patients with facial port wine stains were studied to determine whether chilling lesional skin at the time of treatment could improve the outcome of argon laser therapy and whether this effect could be attributed to increased hemoglobin content of chilled sites, as hypothesized on clinical grounds. Each patient was biopsied in two representative and clinically identical sites, once at room temperature and once immediately after application of ice to the skin surface for 2 to 3 minutes. Two additional identical sites were treated with an argon laser in the same manner. Histologic sections of the port wine stain after application of ice tended to have a higher percentage of erythrocyte-filled vessels, but the effect of chilling on the dermal vasculature varied greatly among patients and was not statistically significant. In contrast, chilling of lesional skin prior to laser therapy resulted in a significantly better average outcome (p = 0.0002), with 57 percent of chilled sites superior to the paired room temperature control and none inferior. In nearly all instances of differential response, the site treated at room temperature manifested scarring, while the chilled site did not. Overall, after an average evaluation period of 4.8 months, 65 percent of the patients achieved a good or excellent result in the control site, and 87 percent achieved this result in the chilled site. These data establish the potential benefit of lesional modification prior to argon laser therapy and suggest that in the case of port wine stain chilling, this benefit is due to reduced heat injury of nonvascular elements in the skin.

Renal Parenchymal Hypoxia, Hypoxia Adaptation, and the Pathogenesis of Radiocontrast Nephropathy

BACKGROUND AND OBJECTIVES Renal parenchymal Po(2) declines after the administration of iodinated radiocontrast agents, reaching critically low levels of approximately 10 mmHg in medullary structures. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS In this review, the causes of renal parenchymal hypoxia and its potential role in the pathogenesis of contrast nephropathy are appraised. RESULTS Commonly associated predisposing factors are associated with a propensity to enhance renal hypoxia. Indeed, animal models of radiocontrast nephropathy require the induction of such predisposing factors, mimicking clinical scenarios that lead to contrast nephropathy in high-risk individuals. In these models, in association with medullary hypoxic damage, a transient local cellular hypoxia response is noted, initiated at least in part by hypoxia-inducible factors. Some predisposing conditions that are distinguished by chronically aggravated medullary hypoxia, such as tubulointerstitial disease and diabetes, are characterized by a priori upregulation of hypoxia-inducible factors, which seems to confer tolerance against radiocontrast-related hypoxic tubular damage. Renal dysfunction under such circumstances likely reflects to some extent altered intrarenal hemodynamics, rather than acute tubular injury. CONCLUSIONS Real-time, noninvasive novel methods may help to differentiate between evolving tubular damage and altered hemodynamics and in the design of appropriate preventive interventions.

Experimental ischemia-reperfusion: biases and myths-the proximal vs. distal hypoxic tubular injury debate revisited.

Although the understanding of processes associated with hypoxic tubular cell injury has remarkably improved, controversies remain regarding the appropriateness of various animal models to the human syndrome of acute kidney injury (AKI). We herein compare available experimental models of hypoxic acute kidney damage, which differ both conceptually and morphologically in the distribution of tubular cell injury. Tubular segment types differ in their capacity to mount hypoxia-adaptive responses, mediated by hypoxia-inducible factors (HIFs), and in cell type-specific molecules shed into the urine, which may serve as early biomarkers for renal damage. These differences may be of value in the perception of the human AKI, its detection, and prevention.

Chronic cyclosporine-induced nephropathy in the rat : a medullary ray and inner stripe injury

Cyclosporine CsA nephrotoxicity was examined in male Sprague-Dawley rats with or without prior uninephrectomy, injected daily with 12.5 mg/kg CsA, and fed a salt-depleted or normal diet for 3-10 weeks. Control rats received the CsA vehicle. CsA induced a fall in creatinine clearance in salt-depleted rats, from 1.3 +/- 0.1 to 0.8 +/- 0.1 ml/min (P less than 0.001), and in normally fed rats from 1.8 +/- 0.2 to 1.0 +/- 0.2 ml/min (P less than 0.02). Vehicle treatment had no effect. The most striking morphologic changes were those of thick ascending limb cell atrophy with concomitant fibroblastic proliferation and collagen formation; these alterations were present in the inner stripe of the outer medulla and the medullary ray. The medullary-ray findings included S2-S3 degenerative changes as well and apparently correspond to the striped fibrosis described in human CsA nephropathy. The alterations were specific to the CsA group, progressive, and most severe in the salt-depleted, CsA-injected rats (on a scale of 0-4: 1.7 +/- 0.2 for medullary rays, and 2.0 +/- 0.2 for inner stripe, P less than 0.001). Morphologic changes predicted renal failure (r = 0.3, P less than 0.01 for cortical alterations, and r = 0.5, P less than 0.001 for medullary alterations). Prior uninephrectomy did not enhance these changes. Thus, chronic CsA administration impaired kidney function and induced morphologic alterations found in regions characterized by, and in nephron segments particularly vulnerable to, limited O2 availability. Salt depletion appears to accelerate the development of chronic CsA renal injury in the rat.

RENAL PARENCHYMAL OXYGENATION AND HYPOXIA ADAPTATION IN ACUTE KIDNEY INJURY

1 The pathogenesis of acute kidney injury (AKI), formally termed acute tubular necrosis, is complex and, phenotypically, may range from functional dysregulation without overt morphological features to literal tubular destruction. 2 Hypoxia results from imbalanced oxygen supply and consumption. Increasing evidence supports the view that regional renal hypoxia occurs in AKI irrespective of the underlying condition, even under circumstances basically believed to reflect ‘direct’ tubulotoxicity. However, at present, it is remains unclear whether hypoxia per se or, rather, re‐oxygenation (possibly through reactive oxygen species) causes AKI. 3 Data regarding renal hypoxia in the clinical situation of AKI are lacking and our current concepts regarding renal oxygenation during acute renal failure are presumptive and largely derived from experimental studies. 4 There is robust experimental evidence that AKI is often associated with altered intrarenal microcirculation and oxygenation. Furthermore, renal parenchymal oxygen deprivation seems to participate in the pathogenesis of experimental AKI, induced by exogenous nephrotoxins (such as contrast media, non‐steroidal anti‐inflammatory drugs or amphotericin), sepsis, pigment and obstructive nephropathies. 5 Sub‐lethal cellular hypoxia engenders adaptational responses through hypoxia‐inducible factors (HIF). Forthcoming technologies to modulate the HIF system form a novel potential therapeutic approach for AKI.