Published on March 17, 2014
Urinary Podocyte Loss in Fabry Disease FSIG Expert Fabry Conference San Diego, Feb 2014 Behzad Najafian, M.D. Department of Pathology University of Washington
KIDNEYS • The average adult has 1 – 1.5 gallon of blood in the body. • Kidneys filter the entire blood in our body 400 times a day.
HOW DOES KIDNEY WORK? • Each kidney has more than 1,000,000 blood filters (nephrons). • These blood filters are not replaceable. Blood filter (nephron)
WHAT ARE PODOCYTES? Podocyte Blood filter (nephron) Podocytes Podocytes are spider- shaped cells that prevent passage of proteins through blood filter
#34 #35 #36 #37 #38#39 #40 Each glomerulus has 500-600 podocytes. Podocytes do not efficiently proliferate. Podocyte loss is cumulative in time Each Podocyte Counts! Once a glomerulus loses more than ~20% of its podocytes, it scars down. This injury is irreversible.
Kidney International (1998) 54, 687–697 Podocyte Injury and Loss Leads to Segmental and Global Glomerulosclerosis Segmental Sclerosis Global Sclerosis
Podocytse are Especially Vulnerable to Injury in Fabry Disease podocytes
Normal Fabry Glomerulus
Podocyte injury progreses with age Podocyte injury correlates with proteinuria Podocyte inclusion density correlates with proteinuria Mesangial cell inclusion density correlates with proteinuria
2 4 6 8 10 12 14 16 18 20 Age (year) 0.34 0.36 0.38 0.40 0.42 0.44 0.46 0.48 0.50 0.52 0.54 0.56 0.58 Vv(PC/G) r=-0.65 p=0.02 Podocyte Mass Density Reduces with Age in Fabry Patients Vv(PC/G) + Vv(Cap/G) + Vv(Mes/G) + Vv(US/G) = 1 Reduced podocyte mass density was not associated with significant change in other glomerular compartments
CAN WE DIAGNOSE KIDNEY INJURY BY STUDYING CELLS IN THE URINE? Blood filter (nephron) Number of podocytes in the urine correlates with urine protein
We can recognize podocytes in the urine by special stains for molecules that are abundantly present in these cells in the kidney PCX CL1 dapi Parietal cells Distal tubules Podocytes Endothelium Peritubular capillaries PCX+ CL1+ CL1+ PCX+ Normal Human Kidney
Preparation of Urine Samples for Counting Podocytes 50 ml Fresh urine (up to 2-3 hrs) Centrifuge at 500 xg for 6 min at 5C local Cytospin preparation outside Resuspend in preservative and ship within 3 days Virtual slide scanning Podocyte staining podocyte
Podocytes in urine from a Fabry patient Urinary Podocytes in Fabry Patients Resemble Those inside the Kidney A glomerulus from a Fabry patient PCX CL1 dapi synaptopodin GL3 merge Podocytes GL3
PCX+ CL1- Small/apoptotic nu PCX+ CL1+ Small/apoptotic nu PCX+ CL1- Normal size nu ~1/4 of Urine Podocytes in Fabry Patients were Apoptotic
Summary and Conclusion • Podocytes play an important role in preservation of kidney function. • Biopsy studies suggest that podocyte injury and loss are progressive with age in Fabry disease. • Urinary podocytes (podocyte loss) increases with age in (male) Fabry patients. • Urinary podocytes (podocyte loss) correlates with proteinuria in (male) Fabry patients. • Podocyturia may become a useful non-invasive biomarker of Fabry nephropathy.
Next Steps • Fabry disease is very heterogeneous. We need to study larger cohorts. • Longitudinal studies are needed to understand podocyturia changes in time and correlation of changes with renal function. • Parallel biopsy and podocyturia studies are needed to confirm if increased podocyturia correlates with less podocytes in the glomeruli. • Laboratory methods to measure podocyturia easier and faster are needed.
Acknowledgments • University of Washington Najafian Lab: Brent Fall Cindy Tower Cecilia Ponchiardi Alex Sokolovsky Marzieh Panahi Ronald Scot, M.D. Stefanie Uhrich • University of Minnesota Michael Mauer, M.D Chester Whitley, M.D, Ph.D. • University of Alabama David Warnock, M.D. • Gnzyme Daniel Gruskin Miriam Gannon Sincere thanks to all patients who volunteered in these studies!
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