Daniel Zhang

BioE MS Thesis Presentation

12:00 PM, Monday, July 15, 2024

IBB 2315

Link:

https://teams.microsoft.com/l/meetup-join/19%3ameeting_M2U1ZDkwOGQtMTkxZi00Y2VkLWI0YzctNjlkN2ExMGVhOTcw%40thread.v2/0?context=%7b%22Tid%22%3a%22482198bb-ae7b-4b25-8b7a-6d7f32faa083%22%2c%22Oid%22%3a%22ec1b231d-4556-4358-ba7d-701fa4407146%22%7d

Meeting ID: 249 712 102 870

Passcode: ybqBHL

Advisor:

Michelle LaPlaca, Ph.D.  (Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology)

Committee Members:

Brandon Dixon, Ph.D. (George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology)

Ari Glezer, Ph.D. (George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology)

Quantifying glymphatic system efflux and permeability following rmTBI

Traumatic brain injury (TBI) is a leading cause of death and injury that can lead to long-term health problems and decreased quality of life and has been shown to alter glymphatic clearance in preclinical and clinical TBI.     This study aims to measure glymphatic system efflux by measuring brain clearance 24 hours post-injury. Male Sprague Dawley rats were divided into Sham (n = 10) and TBI (n = 10) groups.  TBI animals obtained 3 closed head impacts at a velocity of 5 m/s at displacements 5, 2, and 2 mm in 2-minute intervals. Radiolabeled tracers containing 0.05 μCi of [14C]-inulin carboxyl (5000 Da) and [3H]-sucrose (342 Da) in 5 μL of artificial cerebrospinal fluid buffer (aCSF) were injected into the striatum 24 hours post-injury. Blood was collected at 30, 60, 90, and 120 minutes and the lymph nodes, brains, olfactory bulbs (OBs), nasopharynx (NP), and CSF were extracted at 120 minutes post-infusion. The brains were sectioned coronally into 5 mm sections anterior to posterior (BR1, 2, 3, 4). Samples were solubilized and then counted with a liquid scintillation counter. Results showed a significant increase in [14C]-inulin-carboxyl in the normalized counts of all lymph nodes (p = 0.01) and the superficial cervical lymph nodes (SCLNs) (p = 0.01) for TBI vs. Sham groups, indicating reduced glymphatic flux from the injection site. There were no significant differences in the whole brain or individual brain sections, deep cervical lymph nodes (DCLNs), blood, OBs, NP, or CSF between injured and Sham animals for either [14C]-inulin-carboxyl or [3H]-sucrose. Interestingly, we observed [14C]-inulin-carboxyl in the blood, which was intended to be a brain reference, and little to no [3H]-sucrose for TBI and Sham conditions. There were significant levels of both [14C]-inulin-carboxyl and [3H]-sucrose in the CSF, which suggests preferential glymphatic clearance over the blood-brain barrier (BBB). Additionally, there was low recovery of [3H]-sucrose in the whole animal, suggesting it may have been distributed to an unknown area or possibly excreted through the feces or urine. While we saw little injury effects, this study is only focused on a single time point. Injury effects may be more pronounced at other time points, and further studies looking at other times are needed to have a more concrete model of the efflux routes of the glymphatic system.