# Loss of Fatty Acid Oxidation by Neural Stem and Progenitor Cells Increases Proliferation but Does Not Improve Long-Term Neurogenesis After Mild Traumatic Brain Injury

## TL;DR

Blocking fatty acid oxidation in brain stem cells increases short-term cell growth after mild brain injury but does not improve long-term brain cell production.

## Contribution

Shows that fatty acid oxidation loss boosts NSPC proliferation after mild TBI but does not enhance long-term neurogenesis.

## Key findings

- CPT2 deficiency does not affect NSPC proliferation in healthy mice.
- Mild TBI increases NSPC proliferation, especially in male CPT2-deficient mice.
- Increased short-term proliferation does not lead to improved long-term neurogenesis.

## Abstract

Neurogenesis in the dentate gyrus of the hippocampus is a conserved and highly regulated process throughout the lifespan. Hippocampal neural stem and progenitor cells (NSPCs) can either transition into an activated proliferative state or remain quiescent. Accumulating data suggests that mitochondrial fatty acid β-oxidation is important in maintaining NSPCs quiescence under normal physiological conditions; however, the contribution of this pathway in NSPCs following brain injury remains unknown. While severe traumatic brain injury (TBI) is characterized by increased NSPCs proliferation in the hippocampus, the extent of this proliferative response after mild TBI, the most prevalent form of TBI, has not been fully delineated. Using closed head injury as a model of mild TBI and a brain-specific knockout mouse of carnitine palmitoyltransferase 2 (CPT2; an obligate gene in mitochondrial fatty acid β-oxidation), we investigated the role of fatty acid oxidation in hippocampal NSPCs proliferation in naïve and injured male and female mice. Our results show that loss of CPT2 in the brain does not affect hippocampal proliferation in naïve mice. Furthermore, mild TBI upregulates proliferation at day 3 post-injury, and is further increased only in male CPT2-deficient mice. Despite the post-injury increase in hippocampal NSPCs proliferation in CPT2B−/− mice, long-term neurogenesis remained unchanged. Together, these data provides a new insight into the metabolic regulation of NSPCs neurogenesis in the hippocampus following mild traumatic brain injury.