Mechanisms of Podocyte Damage in Alport Syndrome: Insights from the Alport-on-a-chip System

The glomerular filtration barrier, generated through the interaction between podocytes and glomerular endothelial cells (GECs) and separated by a thin layer of glomerular basement membrane (GBM), is structurally responsible for filtering the blood and preventing the loss of proteins. The mature GBM is composed of laminin-521, collagen α3α4α5(IV), and agrin. Mutations in the alpha chains of collagen IV genes lead to a hereditary chronic kidney disease identified as Alport syndrome (AS). To study the cellular and molecular mechanisms responsible for glomerular injury and podocyte loss and design therapeutics strategies targeted to the glomerulus, we must develop human physiologically relevant models of the glomerulus. We designed a glomerulus-on-a-chip (GOAC) constituted by human amniotic fluid kidney progenitor-derived podocytes (hAKPC-P) and human glomerular endothelial cells (hGEC) seeded on OrganoplatesTM(MIMETAS). Our system is characterized by the absence of an artificial membrane separating the two monolayers. The GOAC system recapitulated the function and structure of the glomerulus, including permselectivity. In long-term cultures, seeded cells maintained morphology and formed capillary-like structures that expressed slit diaphragm proteins. Chips generated using these AS podocytes presented impaired permselectivity to albumin due to a dysfunctional assembly of the GBM, typical of AS. We show that miR-193a and serpins may also play key roles in influencing glomerular homeostasis, and modulating their expression may minimize disease progression. Our GOAC system offers a unique prospect for disease-modifying studies and can serve as a platform for personalized medicine studies.
 
Learning Objectives:

1. Explain the structure and function of the glomerular filtration barrier, the pathophysiology of Alport syndrome, and the role of miR193.

2. Explore the glomerulus-on-a-chip model and how it may be used to model disease and in studies of personalized medicine.