Defining Intraglomerular Mechanical Stresses and Podocyte Response in Focal Segmental Glomerulosclerosis
Abstract
Background: An estimated 37 million individuals in the United States (14% of the population) are currently living with chronic kidney disease (CKD). U.S. Veterans are at even higher risk for kidney disease than the general population. Focal segmental glomerulosclerosis (FSGS) is a major form of kidney disease that primarily results from dysfunction of the kidney podocyte, a specialized cell that maintains the kidney’s ability to filter our blood. Despite the importance of this cell, there remains a lack of knowledge related to the mechanisms of podocyte dysfunction and how it leads to FSGS and CKD, limiting the development of more specific therapies that target the podocyte. Podocytes rely on their cellular skeletons to maintain their structure and function while facing constant mechanical stresses within the filtering unit of the kidney. These mechanical stresses consist of (1) strain, resulting from pulsing of the kidney blood vessels on which podocytes are attached and (2) shear stress, resulting from filtration of blood in the kidney. Studies have largely been conducted without these mechanical stresses, and we have yet to measure the mechanical stresses directly experienced by podocytes. Without a better understanding of how podocyte defects—e.g., genetic mutations—impair its response to the mechanical stresses, the discovery of more precise therapies that target podocyte dysfunction will remain limited. To address these gaps in research, we have formed a study team consisting of experts in genetics, physiology, engineering, and advanced microscopy. Our preliminary data show that the latest techniques in microscopy and kidney-on-a-chip technology—a technology that recreates the kidney environment including podocytes and fluid flow—allow for characterizing kidney stresses and podocyte defects in ways not possible before. We are using an advanced microscope to directly visualize fluid flow over podocytes and blood vessel stretching of the podocytes, which reflect the mechanical stress that podocytes experience every second within the kidney. Moreover, we are using kidney-on-chips that incorporate podocytes derived from patients with FSGS-causing genetic mutations. We are using these chips to determine podocyte responses to both normal and elevated mechanical stresses. The research proposed in this project will synergize these latest technologies to comprehensively characterize the fundamental interaction between podocyte dysfunction and mechanical stresses in the kidney. Hypothesis: Our main hypothesis is that podocyte defects render the podocyte vulnerable to the mechanical stresses while filtering blood. This vulnerability is amplified under increased mechanical stresses, and lowering these stresses and/or reversing the podocyte defect can protect against podocyte dysfunction and FSGS. Specific Aims and Approach: Aim 1: Define the mechanical stresses that podocytes experience in live kidneys. The objective of this aim is to directly measure the mechanical stresses that podocytes experience, in both normal states and in states of disease. First, we will measure these stresses by using advanced microscopy in a rat model, comparing healthy rats with rats carrying a genetic mutation known to cause FSGS. Second, we will measure these stresses before and after administration of drug therapies used clinically in FSGS and CKD. We anticipate that, compared to healthy rats, mutant rats will have higher degrees of mechanical strain and shear stress experienced by podocytes. These elevated stresses result from podocyte dysfunction. We further anticipate that after administration of drug therapies, advanced microscopy will detect reductions in these mechanical stresses within the kidneys of mutant rats. The rationale of this aim is (1) to gain new understanding of the real-time mechanical stresses directly experienced by podocytes in normal and diseased (FSGS) conditions and (2) to determine whether these stresses
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 28, 2022
- Source ID
- W81XWH2210237
Entities
People
- Di Feng
Organizations
- Beth Israel Deaconess Medical Center
- United States Army