Faisal H. Cheema

Endocytic delivery of lipocalin-siderophore-iron complex rescues the kidney from ischemia-reperfusion injury

Neutrophil gelatinase-associated lipocalin (Ngal), also known as siderocalin, forms a complex with iron-binding siderophores (Ngal:siderophore:Fe). This complex converts renal progenitors into epithelial tubules. In this study, we tested the hypothesis that Ngal:siderophore:Fe protects adult kidney epithelial cells or accelerates their recovery from damage. Using a mouse model of severe renal failure, ischemia-reperfusion injury, we show that a single dose of Ngal (10 microg), introduced during the initial phase of the disease, dramatically protects the kidney and mitigates azotemia. Ngal activity depends on delivery of the protein and its siderophore to the proximal tubule. Iron must also be delivered, since blockade of the siderophore with gallium inhibits the rescue from ischemia. The Ngal:siderophore:Fe complex upregulates heme oxygenase-1, a protective enzyme, preserves proximal tubule N-cadherin, and inhibits cell death. Because mouse urine contains an Ngal-dependent siderophore-like activity, endogenous Ngal might also play a protective role. Indeed, Ngal is highly accumulated in the human kidney cortical tubules and in the blood and urine after nephrotoxic and ischemic injury. We reveal what we believe to be a novel pathway of iron traffic that is activated in human and mouse renal diseases, and it provides a unique method for their treatment.

The renal papilla is a niche for adult kidney stem cells.

Many adult organs contain stem cells, which are pluripotent and are involved in organ maintenance and repair after injury. In situ, these cells often have a low cycling rate and locate in specialized regions (niches). To detect such cells in the kidney, we administered a pulse of the nucleotide bromodeoxyuridine (BrdU) to rat and mouse pups and, after a long (more than 2-month) chase, examined whether the kidney contained a population of low-cycling cells. We found that in the adult kidney, BrdU-retaining cells were very sparse except in the renal papilla, where they were numerous. During the repair phase of transient renal ischemia, these cells entered the cell cycle and the BrdU signal quickly disappeared from the papilla, despite the absence of apoptosis in this part of the kidney. In vitro isolation of renal papillary cells showed them to have a plastic phenotype that could be modulated by oxygen tension and that when injected into the renal cortex, they incorporated into the renal parenchyma. In addition, like other stem cells, papillary cells spontaneously formed spheres. Single-cell clones of these cells coexpressed mesenchymal and epithelial proteins and gave rise to myofibroblasts, cells expressing neuronal markers, and cells of uncharacterized phenotype. These data indicate that the renal papilla is a niche for adult kidney stem cells.

Ventricular Assist Device Implantation Corrects Myocardial Lipotoxicity, Reverses Insulin Resistance, and Normalizes Cardiac Metabolism in Patients With Advanced Heart Failure

Background— Heart failure is associated with impaired myocardial metabolism with a shift from fatty acids to glucose use for ATP generation. We hypothesized that cardiac accumulation of toxic lipid intermediates inhibits insulin signaling in advanced heart failure and that mechanical unloading of the failing myocardium corrects impaired cardiac metabolism. Methods and Results— We analyzed the myocardium and serum of 61 patients with heart failure (body mass index, 26.5±5.1 kg/m2; age, 51±12 years) obtained during left ventricular assist device implantation and at explantation (mean duration, 185±156 days) and from 9 control subjects. Systemic insulin resistance in heart failure was accompanied by decreased myocardial triglyceride and overall fatty acid content but increased toxic lipid intermediates, diacylglycerol, and ceramide. Increased membrane localization of protein kinase C isoforms, inhibitors of insulin signaling, and decreased activity of insulin signaling molecules Akt and Foxo were detectable in heart failure compared with control subjects. Left ventricular assist device implantation improved whole-body insulin resistance (homeostatic model of analysis–insulin resistance, 4.5±0.6–3.2±0.5; P<0.05) and decreased myocardial levels of diacylglycerol and ceramide, whereas triglyceride and fatty acid content remained unchanged. Improved activation of the insulin/phosphatidylinositol-3 kinase/Akt signaling cascade after left ventricular assist device implantation was confirmed by increased phosphorylation of Akt and Foxo, which was accompanied by decreased membrane localization of protein kinase C isoforms after left ventricular assist device implantation. Conclusions— Mechanical unloading after left ventricular assist device implantation corrects systemic and local metabolic derangements in advanced heart failure, leading to reduced myocardial levels of toxic lipid intermediates and improved cardiac insulin signaling.

Coronary Artery Bypass Grafting in Patients With Low Ejection Fraction

Background—Patients with low ejection fraction (EF) are at a higher risk for postoperative complications and mortality. Our objective was to assess the effect of low EF on clinical outcomes after coronary artery bypass grafting (CABG). Methods and Results—We analyzed 55,515 patients from New York State database who underwent CABG between 1997 and 1999. Patients were stratified into 1 of the 4 EF groups: Group I (EF≤20%), Group II (EF 21% to 30%), Group III (EF 31% to 40%), and Group IV (EF>40%). History of previous myocardial infarction, renal failure, and congestive heart failure were higher in patients with low EF (all P<0.001). Group I experienced a higher incidence of postoperative respiratory failure (10.1% versus 2.9%), renal failure (2.5% versus 0.6%), and sepsis (2.5% versus 0.6%) compared with Group IV. In-hospital mortality was significantly higher in Group I (6.5% versus 1.4%; P<0.001). Multivariate analysis showed hepatic failure [odds ratio (OR), 11.2], renal failure (OR, 4.1), previous myocardial infarction (OR, 3.4), reoperation (OR, 3.4), emergent procedures (OR, 3.2), female gender (OR, 1.7), congestive heart failure (OR, 1.6), and age (OR, 1.04) as independent predictors of in-hospital mortality in the low EF group. The discharges to home rate were significantly lower in Group I versus Group IV (73.1% and 87.7%, respectively; P<0.001). Conclusions—Patients with low EF are sicker at baseline and have >4 times higher mortality than patients with high EF. However, outcomes are improving over time and are superior to historical data. Therefore, CABG remains a viable option in selected patients with low EF.

Effects of Continuous-Flow Versus Pulsatile-Flow Left Ventricular Assist Devices on Myocardial Unloading and Remodeling

Background— Continuous-flow left ventricular assist devices (LVAD) are increasingly used for patients with end-stage heart failure (HF). We analyzed the effects of ventricular decompression by continuous-flow versus pulsatile-flow LVADs on myocardial structure and function in this population. Methods and Results— Sixty-one patients who underwent LVAD implantation as bridge-to-transplant were analyzed (pulsatile-flow LVAD: group P, n=31; continuous-flow LVAD: group C, n=30). Serial echocardiograms, serum levels of brain natriuretic peptide (BNP), and extracellular matrix biomarkers (ECM) were compared between the groups. Myocardial BNP and ECM gene expression were evaluated in a subset of 18 patients. Postoperative LV ejection fraction was greater (33.2±12.6% versus 17.6±8.8%, P<0.0001) and the mitral E/E′ was lower (9.9±2.6 versus 13.2±3.8, P=0.0002) in group P versus group C. Postoperative serum levels of BNP, metalloproteinases (MMP)-9, and tissue inhibitor of MMP (TIMP)-4 were significantly lower in group P compared with group C (BNP: 552.6±340.6 versus 965.4±805.7 pg/mL, P<0.01; MMP9: 309.0±220.2 versus 475.2±336.9 ng/dL, P<0.05; TIMP4: 1490.9±622.4 versus 2014.3±452.4 ng/dL, P<0.001). Myocardial gene expression of ECM markers and BNP decreased in both groups; however, expression of TIMP-4 decreased only in group P (P=0.024). Conclusions— Mechanical unloading of the failing myocardium using pulsatile devices is more effective as indicated by echocardiographic parameters of systolic and diastolic LV function as well as dynamics of BNP and ECM markers. Therefore, specific effects of pulsatile mechanical unloading on the failing myocardium may have important implications for device selection especially for the purpose of bridge-to-recovery in patients with advanced HF.

Hepatic dysfunction and survival after orthotopic heart transplantation: Application of the MELD scoring system for outcome prediction

BACKGROUND The prevalence of heart failure (HF) is rising and the only corrective treatment is cardiac transplantation. Advanced HF is associated with congestive hepatopathy and progressive functional and ultrastructural changes of the liver. We hypothesized that hepatic dysfunction is associated with impaired clinical outcome after heart transplantation. METHODS Data of 617 adult patients (75% men, mean age 53 ± 12 years, mean BMI 25 ± 4, mean ejection fraction 19 ± 9%) undergoing orthotopic heart transplantation (OHT) were analyzed retrospectively. Deviation from institutional normal ranges was used to define abnormal liver function. Standard Model for End-stage Liver Disease (MELD) scores were calculated and a modified MELD score with albumin replacing INR (modMELD) was created to eliminate the confounding effects of anti-coagulation. RESULTS Before OHT, AST, ALT and total bilirubin were elevated in 20%, 18% and 29% of the population, respectively. Total protein and albumin were decreased in 25% and 52% of the population, respectively. By 2 months post-transplantation, percentages of individuals with pathologic values decreased significantly, except for ALT, total protein and albumin, all of which took longer to normalize. Individuals with a higher pre-transplantation MELD or modMELD score had worse outcome 30 days post-transplant and reduced long-term survival over a 10-year follow-up. CONCLUSIONS In this large, single-center retrospective study, we demonstrated the dynamics of liver dysfunction after cardiac transplantation and that elevated MELD scores indicating impaired liver function are associated with poor clinical outcome after OHT. Thus, pre-operative liver dysfunction has a significant impact on survival of patients after cardiac transplantation.

Minimally invasive versus sternotomy approach for mitral valve surgery: a propensity analysis.

BACKGROUND Over the past decade, minimally invasive (MI) mitral valve surgery has grown in popularity. The purpose of this study was to compare both short- and long-term outcomes of mitral valve repair and replacement performed through a MI versus traditional sternotomy (ST) incision using a propensity analysis approach to account for differences in baseline risk. METHODS From January 2000 to December 2008, a total of 1,121 isolated mitral valve operations were performed at our institution (548 ST, 573 MI). Data were retrospectively collected on all patients, and a logistic regression model was created to predict selection to a MI versus ST approach. Propensity scores were then generated based on the regression model and matched pairs created using 1:1 nearest neighbor matching. There were 382 matched pairs in the analysis for a total sample size of 764, or 68.2% of the original cohort. Major outcomes of interest included cardiopulmonary bypass time, cross-clamp time, hospital length of stay, major in-hospital complications, and both short- and long-term survival. RESULTS Cardiopulmonary bypass time was 117.1 ± 2.0 minutes in the ST group and 139.7 ± 2.6 minutes in the MI group (p < 0.0001), and cross-clamp time was 79.6 ± 1.5 minutes in the ST group and 83.7 ± 1.9 in the MI group (p = 0.106). The average hospital length of stay was 9.81 ± 0.61 days among ST patients and 7.76 ± 0.37 days among MI patients (p = 0.0043). There was no significant difference in the frequency of major in-hospital complications between groups. The mean duration of survival follow-up was 4.2 ± 2.4 years. There was no significant difference in mortality at 30 days (p = 0.622) or 1 year (p = 0.599). In addition, there was no significant difference in long-term survival between groups (p = 0.569). CONCLUSIONS Although minimally invasive mitral valve surgery required a slightly longer cardiopulmonary bypass time, there was no difference in cross-clamp time, morbidity, or mortality, and hospital length of stay was significantly shorter when compared with matched sternotomy control patients.

Adipose Tissue Inflammation and Adiponectin Resistance in Patients with Advanced Heart Failure: Correction after Ventricular Assist Device Implantation

Background— Heart failure (HF) is characterized by inflammation, insulin resistance, and progressive catabolism. We hypothesized that patients with advanced HF also develop adipose tissue inflammation associated with impaired adipokine signaling and that hemodynamic correction through implantation of ventricular assist devices (VADs) would reverse adipocyte activation and correct adipokine signaling in advanced HF. Methods and Results— Circulating insulin, adiponectin, leptin, and resistin levels were measured in 36 patients with advanced HF before and after VAD implantation and 10 healthy control subjects. Serum adiponectin was higher in HF patients before VAD implantation compared with control subjects (13.3±4.9 versus 6.4±2.1 &mgr;g/mL, P=0.02). VAD implantation (mean, 129±99 days) reduced serum adiponectin (7.4±3.4 &mgr;g/mL, P<0.05) and improved insulin resistance (Homeostasis Assessment Model of insulin resistance: 6.3±5.8–3.6±2.9; P<0.05). Adiponectin expression in adipose tissue decreased after VAD implantation (−65%; P<0.03). Adiponectin receptor expression was suppressed in the failing myocardium compared with control subjects and increased after mechanical unloading. Histomorphometric analysis of adipose tissue specimens revealed reduced adipocyte size in patients with advanced HF compared with control subjects (1999±24 &mgr;m2 versus 5583±142 &mgr;m2 in control subjects; P<0.05), which increased after VAD placement. Of note, macrophage infiltration in adipose tissue was higher in advanced HF patients compared with control subjects (+25%; P<0.01), which normalized after VAD implantation. Conclusions— Adipose tissue inflammation and adiponectin resistance develop in advanced HF. Mechanical unloading of the failing myocardium reverses adipose tissue macrophage infiltration, inflammation, and adiponectin resistance in patients with advanced HF.

Prolonged donor ischemic time does not adversely affect long-term survival in adult patients undergoing cardiac transplantation

OBJECTIVE With liberalization of donor eligibility criteria, organs are being harvested from remote locations, increasing donor ischemic times. Although several studies have evaluated the effects of prolonged donor ischemic times on short-term survival and graft function, few have addressed concerns regarding long-term survival. METHODS Over the last 11 years, 819 consecutive adults underwent cardiac transplantation at Columbia Presbyterian Medical Center. Recipients were separated into the following 4 groups based on donor ischemic time: <150 minutes, 150 to 200 minutes, 200 to 250 minutes, and >250 minutes. Statistical analysis included Kaplan-Meier survival and Cox proportional hazard models to identify predictors of long-term survival. RESULTS Donor ischemic time was 120.1 +/- 21.1 minutes for group 1 (n = 321), 174.1 +/- 14.7 minutes for group 2 (n = 264), 221.7 +/- 14.6 minutes for group 3 (n = 154), and 295.5 +/- 37.1 minutes for group 4 (n = 80) (P <.001). There were no significant differences in recipient age, donor age, etiology of heart failure, United Network for Organ Sharing status, or history of previous cardiac surgery among the groups (P = NS). Prolonged donor ischemic time did not adversely affect long-term survival, with actuarial survival at 1, 5, and 10 years of 86.9%, 75.2%, and 56.4% for group 1; 86.2%, 76.9%, and 50.9% for group 2; 86.4%, 71.0%, and 43.7% for group 3; and 86.7%, 70.1%, and 50.9% for group 4 (P =.867). There was no significant difference in freedom from transplant coronary artery disease among the 4 groups (P =.474). CONCLUSIONS Prolonged donor ischemic time is not a risk factor for decreased long-term survival. Procurement of hearts with prolonged donor ischemic time is justified in the setting of an increasing recipient pool with a fixed donor population.

Deletion of hensin/DMBT1 blocks conversion of β- to α-intercalated cells and induces distal renal tubular acidosis

Acid–base transport in the renal collecting tubule is mediated by two canonical cell types: the β-intercalated cell secretes HCO3 by an apical Cl:HCO3 named pendrin and a basolateral vacuolar (V)-ATPase. Acid secretion is mediated by the α-intercalated cell, which has an apical V-ATPase and a basolateral Cl:HCO3 exchanger (kAE1). We previously suggested that the β-cell converts to the α-cell in response to acid feeding, a process that depended on the secretion and deposition of an extracellular matrix protein termed hensin (DMBT1). Here, we show that deletion of hensin from intercalated cells results in the absence of typical α-intercalated cells and the consequent development of complete distal renal tubular acidosis (dRTA). Essentially all of the intercalated cells in the cortex of the mutant mice are canonical β-type cells, with apical pendrin and basolateral or diffuse/bipolar V-ATPase. In the medulla, however, a previously undescribed cell type has been uncovered, which resembles the cortical β-intercalated cell in ultrastructure, but does not express pendrin. Polymerization and deposition of hensin (in response to acidosis) requires the activation of β1 integrin, and deletion of this gene from the intercalated cell caused a phenotype that was identical to the deletion of hensin itself, supporting its critical role in hensin function. Because previous studies suggested that the conversion of β- to α-intercalated cells is a manifestation of terminal differentiation, the present results demonstrate that this differentiation proceeds from HCO3 secreting to acid secreting phenotypes, a process that requires deposition of hensin in the ECM.