Pediatric Urology Research at The Medical College of Wisconsin and Children’s Hospital of Wisconsin
Hrair G. Mesrobian, MD, Professor, Pediatric Urology
Our research has focused on urinary biomarker discovery utilizing research technology available at The Medical College of Wisconsin Department of Biochemistry and Biotechnology and Bioengineering Center. We are analyzing the urinary proteome ((PROT Ein complement of the genOME). Proteomics is the study of the composition, structure, function and interactions of proteins directing the activities of cells or found in an environment or special condition (UPJO). Urinary proteome analysis has been a rapidly growing discipline with applications in biomedical research aimed at discovery of disease biomarkers, better understanding of physiology and biology, and discovery of new therapeutic modalities. More than 2,000 proteins have been identified in normal urine. Individual proteins, which are increased or decreased in their level of abundance in disease compared to normal, are valuable biomarkers. Analysis of the urinary proteome as a whole can identify underlying pathologic processes taking place in a diseased kidney. Biomarker-linked functions of interest include inflammation, cell death, oxidative stress, tubular or glomerular damage and interstitial fibrosis. In addition, 30 percent of the urinary proteome is derived from the general circulation. Therefore, the urinary proteome has been interrogated for early markers of coronary heart disease, hepatic carcinoma, diabetes and neurologic disorders, in addition to urinary tract malignancies in adults. In contrast to other body fluids or tissues, urinary proteins have been shown to remain stable up to six months at -80° C and to allow the performance of reliable analyses. Two milliliters of urine is sufficient to run an experiment. The specimen is subjected to trypsin, which cuts the proteins into peptides. The latter are ionized and injected in a mass analyzer. Each peptide or fragment has a specific mass to charge ratio, which is detected by the mass spectrometer. It is analogous to sorting and counting pocket change (the mixture of peptides in the urine). The identity of the proteins is derived from matching the output data to known fragmentation patterns of proteins/peptides based on the genome.
Our studies have focused uniquely on patients with SFU grade 4 hydronephrosis and confirm the presence of statistically significant differential levels of abundance of a number of urinary proteins and polypeptides between normal and UPJO. Our results strongly point to the presence of inflammation, apoptosis, tubular fibrosis and oxidative stress in the hydronephrotic kidney even prior to the emergence of increasing hydronephrosis and or decreasing function by imaging. We are now in the process of validating these results in a prospective fashion. Our ultimate goal is to design a point of care urinary test, which identifies early glomerular or cellular injury, inflammation, oxidative stress and cell death before the onset of fibrosis and irreversible injury. An appropriate analogy is the treatment of acute myocardial infarction since 1960, which has evolved over time in major part because of the discovery of more specific and sensitive markers of injury. This has resulted in a reduction in mortality by 50 percent during this time period. The evolution from serum LDH to troponins in this decade is remarkable. Current modalities (serum creatinine) for assessing renal function are inadequate or too invasive (renal biopsy). The urinary proteome contains information equivalent to a renal biopsy. Our treatment paradigms for UPJO and other GU diseases including malignancies in adults may change.