Multiscale form and function can predict renal biomineralization

University Of California, San Francisco, San Francisco CA

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Abstract

DESCRIPTION (provided by applicant): Mineral formations in tissues are observed in normal and pathologic states. Pathologic biominerals that impair organ function are found in the breast, liver, kidney, salivary glands, brain, eye and vasculature to name a few. By systematically understanding the common denominators and differences between normal and pathologic biomineral formations in humans, effective pharmacological strategies can be developed. In this proposed research strategy we will investigate two distinct types of biomineral formations, intratubular and interstitial that we have observed along the length of a human renal papilla, a unique substructure in a kidney which acts as a biofilter and concentrator. Our preliminary data revealed intratubular mineralization and obstruction of the shorter proximal and peripherally located nephrons in contrast to the interstitial biominerals in the distal tip of the human papilla These two distinct yet overlapping processes have manifested into a spatially delineating interface between proximal and distal regions of the human renal papilla. From a function perspective, the shift in elastic modulus of the matrix at the interface between the proximally biomineralized and distally yet-to-be mineralized regions could be the trigger for interstitial mineralization. We hypothesize that the net decrease in functional papillary volume due to proximal renal papillary biomineralization shifts the elastic modulus at the interface. This shift n elastic modulus is the mechanoresponsive switch that acts as a biophysical cue along the papilla and triggers a biochemical cascade culminating in distal papillary interstitial biomineralization. Proposed specific hypotheses for aims 1 and 2 include: AIM 1) that the structure, elemental compositions, and mechanical properties of intratubular papillary mineral formations are different from those of interstitial formations; and AIM 2) that matrix composition and protein localizations are distinct between intratubular and interstitial mineralizations. The proposed multiscale approach at the level of the renal papilla will document changes in functional volume and will be correlated with spatial maps of mineral densities (MD) between proximal and distal papillary regions. At a tissue-level, respective MD variations will be correlated with spatial maps of molecular composition and elements within minerals, and elastic modulus maps on sections of papilla indicating shifts due to proximal intratubular and distal interstitial mineral formations in fresh human specimens. At an ultrastructure-level, mineral structure (crystalline or amorphous), and fibrillar and globular protein localization will help differentiate formation of intratubular from interstitial minerals. This study will help to elucidae common denominators and differences between nonpathologic (intratubular) and pathologic (interstitial) biominerals, and provide insights to direct discovery of novel therapies to mitigate mineral formations that lead to debilitating and excruciatingly painful urinary stone disease.