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Drug-induced kidney injury (DIKI) is of significant concern, both during drug development and in clinical practice. We report a patient-centric approach for clinical implementation of the FDA-qualified kidney safety biomarker panel, highlighting Phase 1 and 2 trials for candidate therapeutics in Pfizer's portfolio (PFE-1 and PFE-2, respectively) that induced kidney tubular injury in rat toxicity studies. Clusterin (CLU), cystatin-C (CysC), kidney injury molecule-1 (KIM-1), N -acetyl-beta- d -glucosaminidase (NAG), neutrophil gelatinase-associated lipocalin (NGAL), and osteopontin (OPN) were measured in urine samples from (i) Phase 1 healthy volunteers (HVs; n  = 12) dosed with PFE-1, (ii) Phase 2 rheumatoid arthritis (RA) patients (n  = 266) dosed with PFE-2, (iii) lupus patients on standard-of-care therapies (n  = 121), and (iv) healthy volunteers (n  = 60). The FDA-defined composite measure (CM), calculated as the geometric mean response across the 6 biomarkers, was increased ∼30% in HVs administered 100 mg PFE-1 relative to placebo, providing evidence of DIKI. In contrast, the CM for RA patients dosed with PFE-2 was comparable to placebo controls, helping to de-risk the concern for DIKI at clinically relevant doses. Comparing individual biomarker concentrations across disease states revealed that CLU, KIM-1, NAG, NGAL, and OPN are elevated in the urine of RA and lupus patients (those without severe active proliferative lupus nephritis) relative to HVs. Overall, these case studies demonstrate the value of using the FDA-qualified kidney biomarker panel to guide risk assessment, dose selection, and clinical decision making for novel therapeutics, both in HVs and patient populations. [ABSTRACT FROM AUTHOR]

Accumulation of IL-17-producing Th17 cells is associated with the development of multiple autoimmune diseases; however, the contribution of microRNA (miRNA) pathways to the intrinsic control of Th17 development remains unclear. Here, we demonstrated that miR-21 expression is elevated in Th17 cells and that mice lacking miR-21 have a defect in Th17 differentiation and are resistant to experimental autoimmune encephalomyelitis (EAE). Furthermore, we determined that miR-21 promotes Th17 differentiation by targeting and depleting SMAD-7, a negative regulator of TGF-β signaling. Moreover, the decreases in Th17 differentiation in miR-21-deficient T cells were associated with defects in SMAD-2/3 activation and IL-2 suppression. Finally, we found that treatment of WT mice with an anti-miR-21 oligonucleotide reduced the clinical severity of EAE, which was associated with a decrease in Th17 cells. Thus, we have characterized a T cell-intrinsic miRNA pathway that enhances TGF-β signaling, limits the autocrine inhibitory effects of IL-2, and thereby promotes Th17 differentiation and autoimmunity., Introduction IL-17-producing Th17 cells contribute to protection against microbial pathogens but also play a critical role in the development of autoimmunity (1), including multiple sclerosis (MS) and its animal model [...]

Tubulointerstitial lesions are important in the progression of proteinuric renal disease. Tubular kidney injury molecule-1 (Kim-1) is induced in acute renal injury and reversible as a natural course. Kim-1 is also present in chronic renal damage; however, the dynamics of Kim-1 in chronic renal damage and effects of antiproteinuric treatment on Kim-1 are unknown. We studied Kim-1 in adriamycin nephrosis (AN) before and after reninangiotensin system blockade. A renal biopsy was taken 6 wk after adriamycin injection to study renal damage and Kim-1 expression. Subsequently, ACE inhibition (ACEi; n = 23), angiotensin II antagonist ([AT.sub.1A]; n = 23), or vehicle (n = 10) was given for 6 wk; healthy rats served as controls (CON; n = 8). In AN, renal Kim-1 mRNA was induced 26-fold vs. CON at week 6, with further increase in vehicle to week 12 (40-fold) but was reduced by ACEi and [AT.sub.1A] to 10- and 12-fold vs. CON (P < 0.05 vs. week 6). Kim-1 protein was undetectable in CON; in AN, it was present in brush border of dilated tubules in areas with adjacent interstitial lesions. Renal Kim-I protein levels increased from weeks 6-12 in vehicle and decreased in ACEi- and [AT.sub.1A]-treated groups (P < 0.05). In vehicle, urinary Kim-1 was increased (P < 0.05 vs. CON), with a reduction by ACEi and [AT.sub.1A] (P < 0.05 vs. vehicle). Renal and urinary Kim-1 correlated with proteinuria and interstitial damage cross-sectionally. Reductions in proteinuria and renal Kim-1 correlated, which was not associated by corresponding changes in tubulointerstitial fibrosis. In conclusion, on longitudinal follow-up during antiproteinuric treatment increased renal Kim-1 expression is reversible in proportion to proteinuria reduction, likely reflecting reversibility of early tubular injury, supporting its potential as a biomarker for tubulointerstitial processes of damage and repair. ACE inhibitors; chronic kidney disease; fibrosis; proximal tubule; proteinuria

Kidney injury molecule-1 (Kim-1) is associated with ischemic and proteinuric tubular injury; however, whether dysregulation of the reninangiotensin system (RAS) can also induce Kim-1 is unknown. We studied Kim-1 expression in homozygous Ren2 rats, characterized by renal damage through excessive RAS activation. We also investigated whether antifibrotic treatment (RAS blockade or p38 MAP kinase inhibition) would affect Kim-1 expression. At 7 wk of age, homozygous Ren2 rats received a nonhypotensive dose of candesartan (0.05 mg * [kg.sup.-1] * [day.sup.-1] sc) or the p38 inhibitor SB-239063 (15 mg * [kg.sup.-1] [day.sup.-1] sc) for 4 wk; untreated Ren2 and Sprague-Dawley (SD) rats served as controls. Kim-1 mRNA and protein expression were determined by quantitative PCR and immunohistochemistry, respectively, and related to markers of prefibrotic renal damage. Urinary Kim-1 was measured in 8-wk-old Ren2 and SD rats with and without angiotensinconverting enzyme inhibition (ramipril, 1 mg * [kg.sup.-1] * [day.sup.-1] in drinking water for 4 wk). Untreated Ren2 rats showed a >20-fold increase in renal Kim-1 mRNA (expressed as Kim-I-to-GAPDH ratio): 75.5 [+ or -] 43.6 vs. 3.1 [+ or -] 1.0 in SD rats (P < 0.01). Candesartan and SB-239063 strongly reduced Kim-1 mRNA: 3.1 [+ or -] 1.5 (P < 0.01) and 9.8 [+ or -] 4.2 (P < 0.05), respectively. Kim-1 protein expression in damaged tubules paralleled mRNA expression. Kim-1 expression correlated with renal osteopontin, s-smooth muscle actin, and collagen III expression and with tubulointerstitial fibrosis. Damaged tubular segments expressing activated p38 also expressed Kim-1. Urinary Kim-1 was increased in Ren2 vs. SD (458 [+ or -] 70 vs. 27 [+ or -] 2 pg/ml, P < 0.01) rats and abolished in Ren2 rats treated with ramipril (33 [+ or -] 5 pg/ml, P < 0.01). Kim-1 is associated with development of RAS-mediated renal damage. Antifibrotic treatment through RAS blockade or p38 MAP kinase inhibition reduced Kim-1 in the homozygous Ren2 model. homozygous TGR(mRen2)27; angiotensin II type 1 receptor

Recent studies from our laboratory have shown that the mineralocorticoid receptor (MR) blockade with spironolactone (Sp) prevented renal dysfunction and reduced renal injury in both acute and chronic cyclosporine (CsA) nephrotoxicity. This study was designed to evaluate whether Sp administration reduces functional and structural renal damage associated in the setting of preexisting chronic CsA nephrotoxicity. Twenty eight male Wistar rats were fed a low-sodium diet. Fourteen received vehicle (V) and the others were treated with CsA (15 mg/kg sc). After 18 days one half of each group received Sp (20 mg/kg po) for the subsequent 18 days. Creatinine clearance, arteriolopathy, tubulointerstitial fibrosis, arteriolar thickening, glomerular diameter, apoptosis index and TGF-[beta], procaspase-3, and kidney injury molecule 1 (Kim-1) mRNA levels as well as Kim-1 shedding in urine were evaluated. Sp reduced the progression of renal dysfunction and tubulointerstitial fibrosis in preexisting chronic CsA nephrotoxicity. There was a significant reduction of arteriolar thickening in the CsA+Sp group that was associated with greater glomerular diameter and reduction of apoptosis index. These renoprotective effects were associated with reduction of TGF-[beta], procaspase-3, and Kim-1 mRNA levels as well as Kim-1 shedding into the urine. In conclusion, MR blockade with Sp prevented the progression of renal injury in preexisting chronic CsA nephropathy. These results suggest that Sp may reduce CsA-induced established nephrotoxicity in patients. apoptosis; kidney injury molecule 1; transforming growth factor-[beta]; glomerular diameter; fibrosis; procaspase-3

Kim-1, a recently discovered membrane protein, is undetectable in normal kidneys but markedly induced in proximal tubules after ischemic and toxic injury. The function of Kim-1 is unclear, but it is implicated in damage/repair processes. The Kim-1 ectodomain is cleaved by metalloproteinases and detectable in urine. We studied Kim-1 in a nontoxic, nonischemic, model of tubulointerstitial damage caused by acute proteinuria. Uninephrectomized (NX) rats received daily (ip) injections of 2 g BSA (NX+BSA, n = 12) or saline (NX, 1l = 6) for 3 wk. Kidneys were stained for various damage markers by immunohistochemistry (IHC). Kim-1 mRNA (RT-PCR, in situ hybridization), protein (IHC, Western blotting), and urinary Kim-1 (Luminex) were determined. Spatial relations between Kim-1 and other damage markers were studied by double labeling IHC. NX+BSA rats developed massive proteinuria (1,217 [+ or -] 313 vs. 18 [+ or -] 2 mg/day in NX, P < 0.001) and significant renal damage. Kim-1 mRNA was upregulated eightfold in NX+BSA (ratio Kim-1/[beta]-actin, 4.08 [+ or -] 2.56 vs. 0.52 [+ or -] 0.64 in NX, P < 0.001) and localized to damaged tubules. Kim-l protein expression was markedly induced in NX+BSA (2.46 [+ or -] 1.19 vs. 0.39 [+ or -] 0.10% staining/field in NX, P < 0.001). Urinary Kim-1 was significantly elevated in NX+BSA (921 [+ or -] 592 vs. 87 [+ or -] 164 pg/ml in NX, P < 0.001) and correlated with tissue Kim-1 expression (r = 0.66, P = 0.02). Kim-1 protein was found at the apical membrane of dilated nephrons. Kim-1 expression was limited to areas with inflammation (MO), fibrosis ([alpha]-smooth muscle actin), and tubular damage (osteopontin), and only occasionally with tubular dedifferentiation (vimentin). These results implicate involvement of Kim-1 in the pathogenesis of proteinuria-induced renal damage/repair. Urinary Kim-1 levels may serve as a marker of proteinuria-induced renal damage. tubulointerstitial damage; proximal tubular cell; proteinuria; renal pathology doi:10.1152/ajprenal.00403.2005

Sensitive and specific biomarkers are needed to detect early kidney injury. The objective of the present work was to develop a sensitive quantitative urinary test to identify renal injury in the rodent to facilitate early assessment of pathophysiologicai influences and drug toxicity. Two mouse monoclonal antibodies were made against the purified ectodomain of kidney injury molecule-1 (Kim-1), and these were used to construct a sandwich Kim-1 ELISA. The assay range of this ELISA was 50 pg/ml to 5 ng/ml, with inter- and intra-assay variability of biomarkers; nephrotoxicity; enzyme-linked immunosorbent assay; cisplatin; ischemia; acute renal failure

Early diagnosis of drug-induced liver injury (DILI) continues to be a major hurdle during drug development and postmarketing. The objective of this study was to evaluate the diagnostic performance of promising biomarkers of liver injury—glutamate dehydrogenase (GLDH), cytokeratin-18 (K18), caspase-cleaved K18 (ccK18), osteopontin (OPN), macrophage colony-stimulating factor (MCSF), MCSF receptor (MCSFR), and microRNA-122 (miR-122) in comparison to the traditional biomarker alanine aminotransferase (ALT). Biomarkers were evaluated individually and as a multivariate model in a cohort of acetaminophen overdose (n  = 175) subjects and were further tested in cohorts of healthy adults (n  = 135), patients with liver damage from various causes (n  = 104), and patients with damage to the muscle (n  = 74), kidney (n  = 40), gastrointestinal tract (n  = 37), and pancreas (n  = 34). In the acetaminophen cohort, a multivariate model with GLDH, K18, and miR-122 was able to detect DILI more accurately than individual biomarkers alone. Furthermore, the three-biomarker model could accurately predict patients with liver injury compared with healthy volunteers or patients with damage to muscle, pancreas, gastrointestinal tract, and kidney. Expression of K18, GLDH, and miR-122 was evaluated using a database of transcriptomic profiles across multiple tissues/organs in humans and rats. K18 mRNA (Krt18) and MiR-122 were highly expressed in liver whereas GLDH mRNA (Glud1) was widely expressed. We performed a comprehensive, comparative performance assessment of 7 promising biomarkers and demonstrated that a 3-biomarker multivariate model can accurately detect liver injury. [ABSTRACT FROM AUTHOR]

Traditional serum biomarkers used to assess skeletal muscle damage, such as activity of creatine kinase (CK), lack tissue specificity and sensitivity, hindering early detection of drug-induced myopathies. Recently, a novel four-factor skeletal muscle injury panel (MIP) of biomarkers consisting of skeletal troponin I (sTnI), CK mass (CKm), fatty-acid-binding protein 3 (Fabp3), and myosin light chain 3, has been shown to have increased tissue specificity and sensitivity in rodent models of skeletal muscle injury. Here, we evaluated if a previously established model of tissue-engineered functional human skeletal muscle (myobundle) can allow detection of the MIP biomarkers after injury or drug-induced myotoxicity in vitro. We found that concentrations of three MIP biomarkers (sTnI, CKm, and Fabp3) in myobundle culture media significantly increased in response to injury by a known snake venom (notexin). Cerivastatin, a known myotoxic statin, but not pravastatin, induced significant loss of myobundle contractile function, myotube atrophy, and increased release of both traditional and novel biomarkers. In contrast, dexamethasone induced significant loss of myobundle contractile function and myotube atrophy, but decreased the release of both traditional and novel biomarkers. Dexamethasone also increased levels of matrix metalloproteinase-2 and -3 in the culture media which correlated with increased remodeling of myobundle extracellular matrix. In conclusion, this proof-of-concept study demonstrates that tissue-engineered human myobundles can provide an in vitro platform to probe patient-specific drug-induced myotoxicity and performance assessment of novel injury biomarkers to guide preclinical and clinical drug development studies. [ABSTRACT FROM AUTHOR]

The failure to predict kidney toxicity of new chemical entities early in the development process before they reach humans remains a critical issue. Here, we used primary human kidney cells and applied a systems biology approach that combines multidimensional datasets and machine learning to identify biomarkers that not only predict nephrotoxic compounds but also provide hints toward their mechanism of toxicity. Gene expression and high-content imaging-derived phenotypical data from 46 diverse kidney toxicants were analyzed using Random Forest machine learning. Imaging features capturing changes in cell morphology and nucleus texture along with mRNA levels of HMOX1 and SQSTM1 were identified as the most powerful predictors of toxicity. These biomarkers were validated by their ability to accurately predict kidney toxicity of four out of six candidate therapeutics that exhibited toxicity only in late stage preclinical/clinical studies. Network analysis of similarities in toxic phenotypes was performed based on live-cell high-content image analysis at seven time points. Using compounds with known mechanism as reference, we could infer potential mechanisms of toxicity of candidate therapeutics. In summary, we report an approach to generate a multidimensional biomarker panel for mechanistic de-risking and prediction of kidney toxicity in in vitro for new therapeutic candidates and chemical entities. [ABSTRACT FROM AUTHOR]

Drug-induced acute kidney injury (AKI) is often encountered in hospitalized patients. Although serum creatinine (SCr) is still routinely used for assessing AKI, it is known to be insensitive and nonspecific. Therefore, our objective was to evaluate kidney injury molecule 1 (KIM-1) in conjunction with microRNA (miR)-21, -200c, and -423 as urinary biomarkers for druginduced AKI in humans. In a cross-sectional cohort of patients (n?135) with acetaminophen (APAP) overdose, all 4 biomarkers were significantly (P<.004) higher not only in APAP-overdosed (OD) patients with AKI (based on SCr increase) but also in APAP-OD patients without clinical diagnosis of AKI compared with healthy volunteers. In a longitudinal cohort of patients with malignant mesothelioma receiving intraoperative cisplatin (Cp) therapy (n?108) the 4 biomarkers increased significantly (P<.0014) over time after Cp administration, but could not be used to distinguish patients with or without AKI. Evidence for human proximal tubular epithelial cells (HPTECs) being the source of miRNAs in urine was obtained first, by in situ hybridization based confirmation of increase in miR-21 expression in the kidney sections of AKI patients and second, by increased levels of miR-21, -200c, and -423 in the medium of cultured HPTECs treated with Cp and 4-aminophenol (APAP degradation product). Target prediction analysis revealed 1102 mRNA targets of miR-21, -200c, and -423 that are associated with pathways perturbed in diverse pathological kidney conditions. In summary, we report noninvasive detection of AKI in humans by combining the sensitivity of KIM-1 along with mechanistic potentials of miR-21, -200c, and -423. [ABSTRACT FROM AUTHOR]

The high incidence of acute and chronic kidney injury due to various environmental factors such as heavy metals or chemicals has been a major problem in developing countries. However, the diagnosis of kidney injury in these areas can be more challenging due to the lack of highly sensitive and specific techniques that can be applied in point-of-care settings. To address this, we have developed a technique called ‘micro-urine nanoparticle detection (μUNPD)’, that allows the detection of trace amounts of molecular markers in urine. Specifically, this technique utilizes an automated on-chip assay followed by detection with a hand-held device for the read-out. Using the μUNPD technology, the kidney injury markers KIM-1 and Cystatin C were detected down to concentrations of 0.1 ng/ml and 20 ng/ml respectively, which meets the cut-off range required to identify patients with acute or chronic kidney injury. Thus, we show that the μUNPD technology enables point of care and non-invasive detection of kidney injury, and has potential for applications in diagnosing kidney injury with high sensitivity in resource-limited settings. [ABSTRACT FROM AUTHOR]

Objective: The objective of the study was to assess urinary biomarkers of renal injury for their individual or collective ability to predict Worsening renal function (WRF) in patients with acutely decompensated heart failure (ADHF). Methods: In a prospective, blinded international study, 87 emergency department (ED) patients with ADHF were evaluated with biomarkers of cardiac stretch (B type natriuretic peptide [BNP] and its amino terminal equivalent [NT-proBNP], ST2), biomarkers of renal function (creatinine, estimated glomerular filtration rate [eGFR]) and biomarkers of renal injury (plasma neutrophil gelatinase associated lipocalin [pNGAL], urine kidney injury molecule-1 [KIM-1], urine N-acetyl-beta-D-glucosaminidase [NAG], urine Cystatin C, urine fibrinogen). The primary endpoint was WRF. Results: 26% developed WRF; baseline characteristics of subjects who developed WRF were generally comparable to those who did not. Biomarkers of renal function and urine biomarkers of renal injury were not correlated, while urine biomarkers of renal injury correlated between each other. Biomarker concentrations were similar between patients with and without WRF except for baseline BNP. Although plasma NGAL was associated with the combined endpoint, none of the biomarker showed predictive accuracy for WRF. Conclusions: In ED patients with ADHF, urine biomarkers of renal injury did not predict WRF. Our data suggest that a weak association exists between renal dysfunction and renal injury in this setting (Clinicaltrials.gov NCT#0150153). [ABSTRACT FROM AUTHOR]

The development of nephrotoxicity limits the maximum achievable dosage and treatment intervals for cisplatin chemotherapy. Therefore, identifying mechanisms that regulate this toxicity could offer novel methods to optimize cisplatin delivery. MicroRNAs are capable of regulating many different genes, and can influence diverse cellular processes, including cell death and apoptosis. We previously observed miR-155 to be highly increased following ischemic or toxic injury to the kidneys and, therefore, sought to determine whether mice deficient in miR-155 would respond differently to kidney injury. We treated C57BL/6 and miR-155−/− mice with 20 mg/kg of cisplatin and found a significantly higher level of kidney injury in the miR-155−/− mice. Genome-wide expression profiling and bioinformatic analysis indicated the activation of a number of canonical signaling pathways relating to apoptosis and oxidative stress over the course of the injury, and identified potential upstream regulators of these effects. One predicted upstream regulator was c-Fos, which has two confirmed miR-155 binding sites in its 3′ UTR and, therefore, can be directly regulated by miR-155. We established that the miR-155−/− mice had significantly higher levels of c-Fos mRNA and protein than the C57BL/6 mice at 72 h after cisplatin exposure. These data indicate a role for miR-155 in the cisplatin response and suggest that targeting of c-Fos could be investigated to reduce cisplatin-induced nephrotoxicity. [ABSTRACT FROM AUTHOR]

Fibrinogen (Fg) has been implicated in the pathogenesis of several fibrotic disorders by acting as a profibrotic ligand for a variety of cellular surface receptors and by modulating the provisional fibrin matrix formed after injury. We demonstrated increased renal Fg expression after unilateral ureteral obstruction and folic acid (FA) nephropathy in mice, respectively. Urinary Fg excretion was also increased in FA nephropathy. Using in vitro and in vivo approaches, our results suggested that IL-6 mediates STAT3 activation in kidney fibrosis and that phosphorylated (p)STAT3 binds to Fgα, Fgβ, and Fgγ promoters in the kidney to regulate their transcription. Genetically modified Fg heterozygous mice (~75% of normal plasma Fg levels) exhibited only 3% kidney interstitial fibrosis and tubular atrophy after FA nephropathy compared with 24% for wild-type mice. Fibrinogenolysis through Ancrod administration after FA reduced interstitial fibrosis more than threefold compared with vehicle-treated control mice. Mechanistically, we show that Fg acts synergistically with transforming growth factor (TGF)-β1 to induce fibroblast proliferation and activates TGF-β1/pSMAD2 signaling. This study offers increased understanding of Fg expression and molecular interactions with TGF-β1 in the progression to kidney fibrosis and, importantly, indicates that fibrinogenolytics like Ancrod present a treatment opportunity for a yet intractable disease. [ABSTRACT FROM AUTHOR]

Belgrade rats carry a disabling mutation in the iron transporter divalent metal transporter 1 (DMT1). Although DMT1 plays a major role in intestinal iron absorption, the transporter is also highly expressed in the kidney, where its function remains unknown. The goal of this study was to characterize renal physiology of Belgrade rats. Male Belgrade rats died prematurely with ~50% survival at 20 wk of age. Necropsy results indicated marked glomerular nephritis and chronic end-stage renal disease. By 15 wk of age, Belgrade rats displayed altered renal morphology associated with sclerosis and fibrosis. Creatinine clearance was significantly lower compared with heterozygote littermates. Urinary biomarkers of kidney injury, including albumin, fibrinogen, and kidney injury molecule-1, were significantly elevated. Pilot morphological studies suggest that nephrogenesis is delayed in Belgrade rat pups due to their low iron status and fetal growth restriction. Such defects in renal development most likely underlie the compromised renal metabolism observed in adult b/b rats. Belgrade rat kidney nonheme iron levels were not different from controls but urinary iron and transferrin levels were higher. These results further implicate an important role for the transporter in kidney function not only in iron reabsorption but also in glomerular filtration of the serum protein. [ABSTRACT FROM AUTHOR]

Fibrinogen (Fg) has been recognized to play a central role in coagulation, inflammation and tissue regeneration. Several studies have used Fg deficient mice (Fg-/-) in comparison with heterozygous mice (Fg+/-) to point the proinflammatory role of Fg in diverse pathological conditions and disease states. Although Fg+/- mice are considered 'normal', plasma Fg is reduced to ~75% of the normal circulating levels present in wild type mice (Fg+/+). We report that this reduction in Fg protein production in the Fg+/- mice is enough to protect them from kidney ischemia reperfusion injury (IRI) as assessed by tubular injury, kidney dysfunction, necrosis, apoptosis and inflammatory immune cell infiltration. Mechanistically, we observed binding of Fg to ICAM-1 in kidney tissues of Fg+/+ mice at 24 h following IRI as compared to a complete absence of binding observed in the Fg+/- and Fg-/- mice. Raf-1 and ERK were highly activated as evident by significantly higher phosphorylation in the Fg+/+ kidneys at 24 h following IRI as compared to Fg+/+ and Fg-/- mice kidneys. On the other hand Cyclin D1 and pRb, indicating higher cell proliferation, were significantly increased in the Fg+/- and Fg-/- as compared to Fg+/+ kidneys. These data suggest that Fg heterozygosity allows maintenance of a critical balance of Fg that enables regression of initial injury and promotes faster resolution of kidney damage. [ABSTRACT FROM AUTHOR]