(533d) A Network Model Predicts Glucose-Mediated Change in Glomerular Endothelial Structure

Introduction: Diabetic kidney disease (DKD) is a leading cause of kidney failure worldwide. Aberrant glucose metabolism and oxidative stress are physiological disorders in diabetes that lead to immune response and inflammation in the glomerular cells in the kidney. Dysregulated biological mechanisms contribute to the widening and loss of the glomerular endothelial cell (GEC) fenestrations, leading to GEC dysfunction in the early stages of DKD development and progression. GEC fenestrations are essential to the structure and overall hydraulic resistance of the glomerular filtration barrier, yet little is known about how they are regulated and their role in disease. A deeper mechanistic analysis of the glucose-mediated inflammatory mechanisms in the kidney glomerulus can contribute to the understanding of GEC dysfunction in early-stage DKD.

Method: Computational models in systems biology allow the integration of experimental evidence and cellular signaling networks to understand mechanisms involved in disease progression. We built a protein-protein interaction network of the crosstalk between macrophages and GECs in the diabetic kidney, which was stimulated with glucose and an inflammatory stimulus (Figure 1). The network interactions were formulated using normalized-Hill type functions and logic-based ordinary differential equations using an open-source software package Netflux [1]. Logic-based ODE modeling (LBODE) techniques offer a comprehensive view of system behavior without relying on a large number of kinetic or mechanistic parameters. We performed a composite model analysis involving structure and identifiability analysis, global sensitivity analysis, and uncertainty quantification of parameters and predictions [2]. The model responses were fitted to protein biomarker data from in vitro and in vivo mice experiments for short-term (48 hours) and long-term exposure (20 weeks) to glucose and inflammation. The prediction uncertainty was quantified using 95% credible intervals. Further, model perturbation and species knockdown tests on the validated model were beneficial in identifying influential species and interactions associated with DKD.

Results: The fitted model responses had narrow credible intervals suggesting low prediction uncertainty. The model responses were also validated using in vitro data. The interplay of VEGF receptor 1, PLC-gamma, junction proteins, NO, and Ca was found to increase the GEC fenestration width from baseline. LBODE model predicts that reducing the strength of interactions activating NF-kappaB, VEGF-A, VEGF receptor 1, PLC-gamma, NO, and Ca by 50% decreased fenestration width by 10-52%, suggesting recovery of fenestration size. Based on in vivo diabetic mice studies, the LBODE model predicted a 70% increase in fenestration width from baseline between 6-20 weeks under high glucose and inflammation. Ongoing work involves model-based hypothesis testing of the impact of imbalanced NO, Ca, and actin disorder on the loss of fenestrations.

Conclusion: The proposed model identified species and mechanisms that regulate GEC fenestrations and signaling dysregulation in the early stages of DKD. This work supports the study of early-stage GEC dysfunction especially when temporal measurements of structural changes in GEC are challenging to obtain through experiments. The future work may include relating observed ultrastructural changes in GECs to preclinical parameters (filtration rate, permeability) of DKD progression and development.

Reference

[1] Kraeutler et al. BMC Systems Biology 2010, 4:157.

[2] Patidar, K. and Ford Versypt, A. N, bioRxiv (2023).

Acknowledgment: This work was supported by National Institutes of Health grant R35GM133763 and National Science Foundation CAREER grant 2133411.

Figure 1 caption: Glucose-mediated change in glomerular endothelial cell (GEC) structure. (a) Visualization of GEC fenestration (gap) widening in DKD. (b) LBODE network model of crosstalk between macrophages and GECs.