Decoding Molecular Programs for Circuit-Specific Integration of Transplanted Neurons in Traumatic Brain Injury

Every year, more than 165,000 Canadians experience a traumatic brain injury (TBI). For many, recovery is incomplete, leading to long-lasting cognitive, and emotional impairments and loss of physical independence. A major contributor to physical disability is damage to neurons in the brain’s cortex that normally connect to the corticospinal tract, the brain’s high-speed wiring system responsible for voluntary movement of the hands, arms, and legs. When this pathway is disrupted, even simple everyday tasks can become impossible.

Stem cell–based therapies offer hope, as transplanted cells can differentiate into neurons. However, the majority of these cells fail to connect with the correct target neurons and do not rebuild the longdistance connections required for meaningful functional recovery. As a result, the brain remains disconnected, and therapeutic benefits are limited.

This project takes a fundamentally different approach. Instead of expecting transplanted cells to “fit in” on their own, we aim to actively guide them to reconnect with the correct brain circuits. We will identify the genetic programs that enable transplanted human brain cells to form precise long-distance connections and uncover the biological features that make this repair possible. Importantly, we will test these strategies using human-based laboratory models that closely reflect how human brain cells connect to one another, increasing relevance to patients. The knowledge gained from this mechanistic work will support future grant applications aimed at enhancing these connectivity programs using advanced genetic tools, so that more transplanted cells can successfully rebuild the brain’s wiring.

The societal impact is high. TBI imposes an annual economic burden of $12.7 billion in Canada and leaves approximately 75% of survivors unemployed. By moving beyond managing disability and focusing on precise circuit reconstruction, this work aims to restore functional movement and help patients return to independent, meaningful lives.