The effects of elongation strain on choroid plexus endothelial cells as a model of mild traumatic brain injury

Abstract

Traumatic Brain Injuries (TBIs) account for a significant portion of morbidity and mortality accounting for approximately 2.5 million reported cases per year. However, there has been little research regarding the blood-cerebrospinal fluid barrier (BCSFB), the choroid plexus, in TBI pathophysiology. Choroid plexus endothelial cells (CPECs) play a critical role in maintaining CSF homeostasis and regulating neuroinflammation. These endothelial cells, once exposed to the shearing force associated with TBI, release proinflammatory cytokines and become leaky via the breakdown of gap junctions leading to an influx of immune cells. Identifying key cytokines involved in this process and critical timepoints post-injury will allow researchers to better understand key TBI pathophysiology. The aim of this study was to elucidate the cytokine response of CPECs post-mild shearing strain to mimic mild TBI (mTBI). We hypothesized that pro-inflammatory cytokines like IL-6 & TNFα would be elevated post mTBI. Using primary human choroid plexus endothelial cells (HCPECs) purchased from ScienCell (Cat# 1300) and the FlexCell Tension system, HCPECs were subjected to a 12% mild mechanical strain (“one hit”), supernatant was collected, and 36 different cytokines and chemokines were measured at multiple time points post-injury using a membrane-based array (R&D Systems, Cat# ARY005B). This was repeated in a “two hit” model where the cells were subjected to a second 12% strain, 24 hours after the first to examine two subsequent mild head injuries. The multiple time points of supernatant collection allowed for longitudinal measurement of cell behavior and cytokine profiles. Experimental controls included HCPECs plated on the FlexCell flexible membrane 6-well plates without being subjected to mechanical strain. Consistent with the literature and clinical TBI presentation, cytokines were elevated 48-hours post-injury. There were changes in cytokine production between 24- to 48- hours post-injury, most notably CCL2, MIP1α/MIP1β, G-CSF, IL-10 and CCL5 (RANTES), to name a few. Interestingly, while some cytokines increased after injury, such as the 2-fold and 4-fold increase in CCL2 between 24- and 48-hours post one and two hit, respectively, others decreased. There was a 3-fold decrease in RANTES between 24- and 48- hours post one hit, and a 2-fold decrease in G-CSF. Contrary to our hypothesis, cytokine responses post-injury were related to regulatory and anti-inflammatory responses as opposed to pro-inflammatory responses. As both RANTES and G-CSF are implicated in chronic inflammation, the results indicate that there was a decrease in pro-inflammatory responses in favor of more regulatory and anti-inflammatory responses post mTBI. Overall, this pilot project helped identify key cytokines involved in HCPEC signaling after mild mechanical strain and demonstrated a critical window between 24- and 48- hours post-injury for the treatment of mTBI. Indiana Academy of Sciences; Marian University This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.