An Enhanced Neurovascular Model with Scanning Conductance Imaging of Cell Junctions to Determine the Role of Matrix Metalloproteases in Multiple Sclerosis - PROJECT SUMMARY It is well-established that damage to the myelin sheath, the protein-based substance that surrounds nerve fiber, is a hallmark feature of Multiple Sclerosis (MS), a disease that ~ affects 1 in 800 people in the United States, and females at a higher ratio (~2:1) than males. The neurovascular unit (NVU), a concept in neuroscience that describes the relationship between brain cells, the extracellular matrix (ECM), basement membrane, and associated blood vessels, is at the center of MS pathology. The exact mechanism leading to an attack on the myelin sheath is not known, although evidence suggests the blood brain barrier (BBB) and ECM begin to break down and become permeable. This increase in barrier permeability enables toxins and other foreign species to invade the central nervous system space and damage myelin leading to the multiple scar lesions (hence, Multiple Sclerosis) that are characteristic of the disease. Unfortunately, investigating barrier permeability in vivo, and mechanisms leading to its breakdown, is challenging. Here, an investigative team with basic and clinical science experience proposes development of an in vitro platform that contains a highly resistant barrier of cells while also enabling blood flow from people with varying stages of MS. In this construct, this in vitro NVU will be employed to determine the role of MMP-9 (one member of the family of enzymes known as matrix metalloproteinases) in barrier permeability and NVU dysfunction. It is hypothesized that high levels of MMP-9, which are well-known to exist in people with MS, is leading to either (1) degradation of the tight junction proteins that lead to high barrier resistance or (2) is degrading collagen (MMP-9 is also known as type IV collagenase, an enzyme that breaks down collagen in the ECM). Due to the broad expertise and collaborative history of the investigative team, a key feature of this proposal is integration of measurement tools that enable real-time determination in changes of barrier permeability. Specifically, our team proposes the use of “on-chip” transendothelial electrical resistance (TEER) measurements for real-time changes in barrier resistivity coupled with nanoscale scanning ion conductance microscopy (SICM) to determine local breaches of barrier permeability. While the in vitro model of the NVU and measurement tools will be developed and optimized in specific aims 1 and 2, later aims will incorporate whole blood samples from people with varying stages of MS to determine if (1) higher levels of MMP-9 circulating through the device leads to an increase in barrier permeability and destruction of collagen nanofibers strategically embedded in the device and (2) if a popular disease modifying therapy used in MS (interferon-beta, IFN-) reduces MMP-9 production in circulating blood from MS patients, thereby preserving barrier integrity in our in vitro NVU model. Our studies use rigorous controls including people with neurological diseases other than MS and healthy subjects to help us draw meaningful conclusions about factors leading to lesion formation in MS.
