National Institute of Diabetes and Digestive and Kidney Diseases
George M. O'Brien Kidney Research Core Centers
Vanderbilt O'Brien Mouse Kidney Physiology and Disease Center

Director: Raymond C. Harris, M.D.
Ann and Roscoe R. Robinson Professor of Medicine,
Director, Division of Nephrology and Hypertension

The National Institute of Health established the George O'Brien Centers in 1987 as specialized centers of research into nephrologic and urologic disease. There are currently six O'Brien Renal Centers in the U.S. The Vanderbilt program is the oldest continuing O'Brien Renal Center and is now beginning its 23rd year of existence. The focus of our center continues to be the investigation of mechanisms of progressive nephron destruction and potential interventions to slow the rate of loss of renal function.Studies dating back to the 1980's have refocused the attention of the renal community on the problem that progressive decline in renal function occurs in chronic glomerular injury following a variety of inflammatory or non-inflammatory insults, an inexorable progression of renal damage ensues to the ultimate conclusion of a scarred, shrunken and nonfunctional kidney. The kidney possesses a limited repertoire of responses to injury, with the response to glomerular injury being the accumulation of increasing amounts of extracellular matrix leading ultimately to obliteration of the capillary lumen and decrease in filtration capacity. Associated with the glomerulosclerosis is peri-glomerular and tubulointerstitial fibrosis, with variable infiltration of macrophages and lymphocytes. Understanding the underlying mechanisms of this process and developing successful interventions is a high priority for renal research, given the ever increasing number of patients developing end stage kidney disease in the U.S. The results obtained to date in clinical trials with ACE inhibitors, tight blood glucose control and strict dietary control suggest that clinical intervention to slow the rate of progression is possible and speak to the urgent need for further strategies to retard or interrupt the development of end stage renal failure. The factors that contribute to, or modulate the progression of, renal injury continue to be an area of intense study. Animal and invitroital studies have identified a number of important cellular and molecular mechanisms involved in progression; the role of cytokines and growth factors has received considerable attention recently. Since its inception, the Vanderbilt O'Brien Center has been focused on understanding mechanisms underlying progressive nephron injury and identifying potential therapeutic targets to retard injury progression.The Vanderbilt O'Brien Center participants have made significant contributions to our understanding of mechanisms of progressive nephron destruction, especially in three areas of investigation, involving investigation of cyclooxygenase-2 (COX-2) in physiologic and pathophysiologic regulation of structural, functional and developmental renal processes, the role of the renin-angiotensin system (RAS) in progressive renal injury and control of extracellular matrix production and turnover in glomerulosclerosis.Cyclooxygenase-derived prostanoids are important mediators of altered renal hemodynamic function in response to both inflammatory and progressive noninflammatory renal diseases. The role of prostanoids in mediating or modulating the progressive fibrosis occurring in the glomerulus and tubulointerstitium in chronic renal injury has been incompletely characterized, but there is suggestive evidence in animal studies that thromboxane synthetase inhibitors will ameliorate renal damage in response to renal mass ablation, and studies in cultured mesangial cells have suggested that prostanoids can mediate or modulate growth and extracellular matrix deposition. Furthermore, it is well known that with aging, renal prostaglandin production decreases, and the elderly are more susceptible to adverse effects of NSAID administration. Finally, a significant cause of chronic renal disease worldwide remains analgesic nephropathy.Regulation of prostanoid production depends upon the release of arachidonic acid from membrane phospholipids by specific phospholipases and subsequent conversion to prostaglandin H2 by prostaglandin G2/H2 synthase (cyclooxygenase). Further conversion to individual prostanoid species is mediated by specific synthetases, which determine tissue-specific expression of prostanoids. Cellular responses are mediated by specific membrane-associated receptors, which are members of the G-protein coupled receptor superfamily. Since receptor affinity for the prostanoids is in the nanomolar range, prostanoids act locally on the tissues in which they are synthesized, or on tissues adjacent to those in which they are synthesized. Recent studies have demonstrated that in addition to the constiutive cyclooxygenase enzyme, COX-1, certain cells express a second gene, COX-2, the expression of which is activated by mitogenic stimuli There is increasing evidence that COX-2 plays a crucial role in inflammatory diseases in vivoThe Vanderbilt O'Brien Center made the seminal observation that COX-2 mRNA and immunoreactive protein were expressed in normal mammalian kidney and were localized to the macula densa and surrounding cortical thick ascending limb (cTALH) in the cortex and to the lipid-laden interstitial cells in the medulla. We also determined that cortical COX-2 expression increased in response to volume depletion induced by chronic sodium restriction or dehydration. During the current funding period, we have made additional important observations concerning the regulation and role of COX-2 in regulation of the renin-angiotensin system, in regulation of medullary blood flow and medullary tonicity, in regulation of microvascular angiogenesis, in the expression pattern during antenatal and postnatal renal development and in the pathophysiologic alterations in progressive renal disease. There is increasing evidence, much of it generated by the Vanderbilt O'Brien Renal Center, that COX-2 metabolites play crucial roles both in regulation of important renal physiologic function and in progressive nephron damage.The participants in this Center provide a complementary and integrated array of experimental strategies to investigate these aims, including genetic approaches and combined in vivo and in vitro studies. The individual projects are highly interactive and are all dependent upon the three cores, which will provide, respectively, extremely precise measurement of prostanoids in biologic fluids using state of the art GC/MS methodology, qualitative and quantitative morphologic analysis and the development, maintenance and physiologic assessment of gene-targeted mutant mice. In this regard, the investigators in the Center have access to COX-1 and COX-2 knockout mice, as well as angiotensinogen and AT1 knockout mice. The animal core will generate and provide to the projects additional genetically engineered mice, including chimeric COX-2 null mutants and targeted COX-2 over-expressing mice. These animals will provide useful tools for defining the biologic role of cyclooxygenase metabolites in renal development and responses to progressive renal injury.

Projects and Cores:

Core A:  The Phenotyping-Pathophysiology Core
   Raymond C. Harris, M.D., Principal Investigator

Core B:  The Histology and Morphometry Core
   Agnes Fogo, M.D., Principal Investigator

Core C:  The In Vivo Mouse Kidney Imaging Core
   Takamune Takahashi, M.D., Ph.D., Principal Investigator

Core D:  The Renal Cell-Specific Transgenic Core
   Donald Kohan, M.D., Ph.D., Principal Investigator
   University of Utah

The Education Core
   Mark P. deCaestecker, M.B.B.S., Ph.D., Principal Investigator

Pilot Project 1:  Mechanism of Endothelial-to-Mesenchymal Transition to Diabetic Nephropathy
   Li-Jun Ma, M.D., Ph.D., Principal Investigator

Pilot Project 2:  The Role of Beta 1 Integrin and ILK in Proximal Tubule Regeneration after Injury
   Manakan Betsy Srichai, M.D., Principal Investigator

Pilot Project 3:  Modulation of Renal Ischemia Reperfusion Injury by NFATc1
   H. Scott Baldwin, M.D., Principal Investigator