Second harmonic microscopy to quantify renal interstitial fibrosis and arterial remodeling

Area of Science:

• Nephrology
• Biomedical Imaging
• Pathology

Background:

• Interstitial fibrosis, marked by collagen deposition, is a key predictor of chronic kidney disease progression.
• Accurate assessment of renal fibrosis is crucial but remains challenging in research and clinical settings.
• Current methods struggle to quantify fibrosis and differentiate it from other renal pathologies.

Purpose of the Study:

• To develop and validate a novel imaging methodology for quantitative assessment of interstitial fibrosis in kidney tissues.
• To utilize second harmonic generation (SHG) microscopy for high-accuracy, 3-D imaging of collagen in unstained human and mouse kidneys.
• To investigate the spatial heterogeneity of fibrosis progression and its distinction from glomerulosclerosis.

Main Methods:

• Development of a novel methodology based on second harmonic generation (SHG) microscopy.
• Imaging of collagen fibers in unstained human and mouse kidney tissues.
• Implementation of automated image processing for quantitative scoring of thick murine tissues, accounting for renal shape variability.

Main Results:

• Quantitative 3-D imaging of interstitial fibrosis and arterial remodeling with high accuracy was achieved.
• SHG microscopy revealed fibrosis as a heterogeneous process across different renal compartments.
• SHG signals from fibrillar collagens did not overlap with glomerular tufts, suggesting distinct pathophysiological mechanisms for interstitial fibrosis and glomerulosclerosis.

Conclusions:

• SHG microscopy provides a powerful tool for accurate, quantitative assessment of interstitial fibrosis and arterial remodeling in kidneys.
• The findings highlight the heterogeneous nature of fibrosis progression within the kidney.
• This approach supports the distinction between interstitial fibrosis and glomerulosclerosis, identifying the latter as a nonfibrotic process involving SHG-silent collagens.