Translational Kidney Research Program
The Translational Kidney Research Program (TKRP) at Ochsner Medical Center brings together basic and clinical science to bridge laboratory discovery with advancement in the diagnosis and treatment of human kidney disease. The program is led by Dr. Juan Carlos Q. Velez and it is focused on several areas of investigation: Hepatorenal Syndrome and Acute Kidney Injury in Cirrhosis, Urinary Cast Composition in Acute Kidney Injury, and Podocyte Aminopeptidase A in Glomerular Disease.
Hepatorenal Syndrome and Acute Kidney Injury in Cirrhosis
Overarching Goal: Our laboratory is interested in finding new ways to improve the currently available clinical tools for the diagnosis and treatment of acute kidney injury (AKI) in patients with cirrhosis. In particular, we are focused on hepatorenal syndrome type 1 (HRS-1), an ominous form of AKI in cirrhosis.
Prospective Cohort (Pre-BRAKE) of AKI in Cirrhosis
Our research team has established a real-time electronic medical record-based prospective data collection for hospitalized patients with cirrhosis who develop AKI. The cohort (Pre-BRAKE) was established as a preliminary phase for the upcoming prospective pilot interventional study (BRAKE, Blood Pressure Rise in Acute Kidney Injury in End-Stage Liver Disease). Exploiting the existence of this cohort, we capture clinical data of patients with HRS-1 or other forms of AKI in cirrhosis, such as acute tubular injury (ATI). Urine specimens from subjects enrolled in the cohort are collected, examined (brightfield, phase contrast, darkfield), scored, utilized in the UCCP study (see below) and stored.
Prospective Pilot Study of Non-Contrast MRI to Assess Renal Perfusion in HRS
As an ancillary project of Pre-BRAKE, we are actively enrolling patients in the TRACE-HRS study (Tracking Renal Arterial Circulatory Effectiveness in HRS), a CRISP-funded project. The study involves measuring perfusion of the kidney cortex in cirrhotic subjects with HRS-1 or other forms of AKI by arterial spin labeling (ASL) MRI. The goal is to examine this technique as a diagnostic tool as well as to assess its value as predictor of response to vasoconstrictors in HRS-1. Urine specimens from subjects enrolled in this ancillary study are also collected, examined by microscopy (brightfield, phase contrast, darkfield), scored, utilized in the UCCP study (see below) and stored.
Role of Intrarenal Angiotensin-Mediated Hemodynamics in Animal Model of Cirrhosis
- We are utilizing 2 rodent models of cirrhosis (carbon tetrachloride and common bile duct ligation) in aminopeptidase A (APA) knockout mice. APA-KO mice are known to have impaired metabolism of angiotensin II, a potent vasoconstrictor and essential molecule in the deranged systemic hemodynamics in HRS-1. Our laboratory is examining the role of intrarenal angiotensin II metabolism in the severity of AKI in the carbon tetrachloride model of cirrhosis.
- In collaboration with Dr. Luis Juncos from University of Arkansas for Medical Sciences, we are interested in examining the role of bile salts and reactive oxygen species in tubular epithelia integrity and renal hemodynamics in the common bile duct ligation model of cirrhosis with hyperbilirubinemia.
Urinary Cast Composition in Acute Kidney Injury
Overarching Goal: Our laboratory is interested in determining the composition of urinary casts as a platform for future development of new diagnostic biomarkers for AKI. Our study is called UCCP (Urinary Cast Composition Project).
Utilizing urine specimens from the Pre-BRAKE cohort as well as from patients with AKI from other causes, our laboratory is currently studying new methodologies for urinary cast isolation and examination of its composition.
- We are currently developing various bench techniques to treat pellets from urine specimens to enrich them with granular and waxy casts simultaneously identified by microscopy. Techniques being tested include sucrose density gradient centrifugation, antibody-based flow cytometry and fixation methods.
- In collaboration with Dr, Michael Janech from College of Charleston, we are currently examining the protein composition of urinary casts by robust mass spectrometry-based approaches.
Podocyte Aminopeptidase A in Glomerular Disease
Overarching Goal: Our laboratory is interested in understanding the role of the angiotensinase aminopeptidase A (APA) in kidney health and in development of glomerular disease.
Dr. Velez and his collaborators at MUSC have demonstrated that aminopeptidase A (APA) plays an important role in modulating the intrarenal action of angiotensin II. In culture mouse podocytes and isolated rat glomeruli, it was shown that APA is the most robust enzyme responsible of cleaving angiotensin-related peptides in the glomerular compartment. APA degrades angiotensin II down to a heptapeptide Ang II to initiate the metabolism of angiotensin II, a potent vasoconstrictor and pro-fibrotic molecule implicated in the progression of proteinuric CKD. In addition, APA converts angiotensin I – the precursor of angiotensin II – into angiotensin 2-10, thereby shunting the pathway of conversion away from angiotensin II formation. Further, utilizing 3 model models of glomerular disease (angiotensin II chronic infusion, glomerulotoxic serum injection and 5/6 renal ablation) in APA knockout mice (APA-KO), our studies demonstrated that deficiency of APA is associated with exacerbated glomerular injury and augmented accumulation of intrarenal angiotensin II. Currently, our laboratory is pursuing the following next steps:
- In human kidney specimens (collaboration with Arkana Laboratories), we are examining adaptive changes in expression and localization of key podocyte-localized peptidases in diabetic glomerulopathy and focal segmental glomerulosclerosis. We are studying APA and neutral endopeptidase with our established techniques of colocalization with podocyte markers (synaptopodin, podocalyxin, nephrin) via confocal microscopy and immunofluorescence.
- In collaboration with Dr. Victor Puelles from Aachen University in Germany, we are performing podometrics in APA-KO mouse kidneys under basal conditions and when subjected to glomerular injury, in order to examine the role of APA in cellular adaptations to injury in podocytes
- In collaboration with Dr. Daniel Batlle from Northwestern University, we are expanding our studies in glomerular disease by looking at streptozotocin-induced model of diabetes mellitus to study the role of APA in diabetic nephropathy. In addition, we are examining the genesis of derangements in the integrity of glomerular basement membrane in APA-KO identified by electron microscopy