Identification of Biochemical Changes Associated with Diabetes in Renal Glomeruli by Infrared Spectroscopic Imaging
Michael J Walsh, Suman Setty, Andre Kajdacsy-Balla, Rohit Bhargava. University of Illinois at Urbana-Champaign, Urbana, IL; University of Illinois at Chicago, Chicago, IL
Background: The ability to detect chemical changes in tissues is limited by the level of resolution of special stains and immunostains. Infrared (IR) spectroscopic imaging has shown great promise at measuring biochemical changes in tissues in an entirely label-free fashion. Renal changes in diabetes as seen by light and electron microscopy include expansion of the glomerular mesangium and glomerular and tubular basement membranes by deposition of matrix thus leading to chronic renal failure. IR spectroscopic imaging has the potential to allow for novel insight into the biochemical changes in diabetes including non-enzymatic glycosylation of matrix proteins and altered composition of the matrix.
Design: 16 kidney biopsies were acquired, 8 from non-diabetics and 8 from diabetics were analyzed. A formalin-fixed paraffin-embedded serial section was stained using Periodic Acid Schiff and an adjacent unstained tissue section were obtained. IR images were acquired of the whole tissue at a low resolution (6.25x6.25microns) for the identification of gross chemical changes observed between normal and diabetic patients. In addition, high resolution IR images were acquired glomeruli and proximal tubules. Regions within the glomeruli were categorized as normal mesangium, early Kimmelstiel-Wilson (KW) nodules, late KW nodules, glomerular basement membranes and other areas from obsolescent glomeruli and spectroscopic data extracted for comparison.
Results: New high resolution IR imaging techniques have allowed for the visualization and chemical characterization of glomerular structures in kidney tissues, including glomerular basement membrane, mesangium and Bowman's capsule. Chemical changes measured by IR were found to be different in normal and diabetic tissues, in particular, increased levels of glycosylation in late KW nodules of the mesangium as compared to the mesangium from normal subjects.
Conclusions: IR spectroscopic imaging can allow for novel insight into the chemical changes occurring in kidney tissue structures that correlate with disease states. In particular, this work demonstrates increasing levels of glycosylation can be measured using IR imaging in an entirely label-free fashion. Future work will focus on the identification of pre-diabetic changes and whether predictions of increasing glycation and extracellular matrix composition can be related to early pre-diabetes before the appearance of histological changes.
Wednesday, March 6, 2013 9:30 AM
Poster Session V # 289, Wednesday Morning