Modeling Transport of Blood Plasma and Solutes within the Kidney Glomerulus

Diabetic kidney disease is one of the most common long-term complications associated with type one and type two diabetes. There are gaps in the understanding about the progression of the damage within the kidney. By focusing on the filtration system of the kidney, we hope to better understand how the damage associated with diabetic kidney disease is caused.

The glomerulus is a network of blood vessels within the kidney that separates waste from blood plasma. High levels of glucose transporting through the glomerulus is a major contributing factor for the development and progression of diabetic kidney disease. To better understand how high glucose levels damage the glomerulus, we modeled the transport and flow of blood plasma and solutes within the glomerulus using COMSOL.

We modeled the glomerulus as a three-layered system consisting of the mesangial cells, glomerular basement membrane, and the podocytes—the key layers that comprise the glomerular filtration barrier. Blood plasma flows into the mesangial cells laterally and out of the podocytes vertically. We utilized COMSOL to replicate the glomerulus by using a porous media for the system, which allows for the material to consist of fibers and pores similar to the kidney. Combining the transport of dilute solute species through porous media and Darcy’s law, we were able to successfully model the transport of solute proteins albumin and immunoglobulin A (IgA) through the mesangial layer of the glomerulus. We compared results from our COMSOL model with a published model and achieved good agreement between the models. We are now working on the addition of glucose, a small molecule that can move throughout the entire glomerular domain, and other proteins of interest that can negatively impact the health of the tissue during diabetic kidney disease. We are adding the reactions between these proteins that occur within the glomerulus.

After adding all of the solutes and reactions to the model, we plan to predict changes in the material properties of the glomerulus that will lead to a change in thickness of the layers of our model. The change in thickness will then cause our larger solutes to pass through the model similarly to a glomerulus suffering from diabetic kidney disease, where proteins are able to leak into the urine in detectable concentrations.