College of Science and Health Theses and Dissertations

Date of Award

Spring 6-11-2021

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Science

First Advisor

Dorothy Kozlowski, PhD

Second Advisor

Daniel Peterson, PhD

Third Advisor

Talitha Rajah, PhD

Abstract

Abstract

A concussion is one of the most common types of traumatic brain injury. Repeat concussion has been associated with an increased likelihood of developing neurodegenerative diseases, such as Parkinson's and Alzheimer's Disease, and chronic traumatic encephalopathy. Although treatments are available to tolerate the symptoms, one potential treatment to address the pathology is to use adult neurogenesis to promote and recruit cells to injury sites for repair. Neurogenesis is the study of new neurons from neural stem cells (NSCs) present in adult humans at the hippocampal dentate gyrus. This study explored whether repeat concussion induces the proliferative capabilities of NSCs using BrdU and NSCs' commitment in becoming neurons using anti-DCX+ in both male and female rats. Long-Evans adult rats were divided into treatment (sham and repeat concussion) and sex (male and female) groups (n=5-6/group). The injury was performed once every 48 hrs for three days using a clinically relevant model of closed head injury (Jamnia et al., 2017). A novel object recognition test was also used to assess working memory and compare it to changes in the BrdU+ and DCX+ populations. BrdU was injected three times every 2hr on day 45, and then animals were euthanized 24hrs later. Unbiased stereology was used to manually count cells expressing BrdU, DCX or both at randomly selected sites on the dentate gyrus. The current study has shown no significant results due to the chronic effects of repeat concussions on cell proliferation for neurogenesis (p= 0.6501), nor on neuronal commitment (p= 0.3944). Normal estrus-cycling female rats’ BrdU (p= 0.7777) and DCX (p= 0.6743) populations did not change compared to male rats. However, the injured female rats did show a trend for a greater amount of DCX+ expression than the injured male population. The injured females reported the strongest correlation (R=0.702) between the novel object test and the DCX+ population, but it was not statistically significant. The current study did not show any significant effects of repeat concussion on the neurogenic response in both males and females. However, given a limited sample size, and trends present in this study, future studies should be conducted to continue this line of inquiry. This would potentially lead to treating the pathology of a concussion with future implications of treating other brain pathologies, such as neurodegenerative diseases.

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