Do Reprogrammed Brain Cells Hold the Key to Healing Damaged Networks After Traumatic Brain Injury?
Doris Lam | 21-LW-014
Traumatic brain injury (TBI) has become the signature wound for military personnel. Moreover, there are many sources of TBI including improvised explosive devices, combat, motor-vehicle accidents, and more. The predominant number (82%) of documented TBI cases in military personnel are of the mild form, allowing individuals to return to active duty following a period of recovery. TBI, however, is not a single-injury event; tissue damage persists and can alter brain structure and function long term (i.e., months to years), even after military personnel have been deemed recovered and returned to duty. Still, treatment options for TBI remain scarce and are limited to rehabilitation and pharmaceutical interventions to adapt to the TBI-induced disability (e.g., cognitive and motor deficits). Thus, there is still a large need for technological advancement to better understand changes in brain function following TBI. There is also a large need for screening of potential therapeutics that will provide the bioresilience needed to treat active-duty personnel, repair TBI-induced disability, and prevent late-onset TBI-induced neurodegenerative diseases.
Cell-based therapies, stem-cell transplantation, and, more recently, in vivo astrocyte reprogramming are attractive therapeutic approaches for treating TBI-related pathophysiology. Initial studies demonstrate the potential for neuroprotection and tissue repair at the site of injury/disease in preclinical models of neurodegenerative diseases and stroke and promoting some degree of functional recovery in cognitive and motor behavior in in vivo models. However, the lack of clinical translation of cell-based therapies for neurological disease may be due to inadequate understanding of whether these treatments resolve circuit abnormalities (from a collection of networks) leading to functional improvement, or simply replace cells. Further investigation is needed to understand whether these new neurons (from reprogrammed astrocytes) can form neuronal networks that have the potential to repair brain activity, back to pre-injury levels of activity, that are left damaged or dysfunctional following TBI.
Our project has used a novel experimental conceptual framework that combines methodologies, including in vitro technologies (e.g., 2D multi-electrode arrays [MEAs]), (Doris Lam et al. 2022), computational tools (e.g., graph-based models) and complementary cellular assays (Doris Lam et al. 2022), to assess the functional state of neurons from reprogrammed astrocytes under a healthy and reactive state and the development and maturation of their networks. The results of our project demonstrate we can chemically reprogram astrocytes into neurons, track the transformation and development of these cells for a prolonged period of time (i.e., two months), and reliably record neural-network activity over the course of days, weeks, or months. Further, we have developed complementary computational tools to identify the functional phenotype of the neurons (e.g., excitatory and inhibitory neurons), which is important in understanding healthy and pathological brain activity.
The significance of our findings evaluates whether a novel therapeutic approach (e.g., astrocyte reprogramming) is capable of repairing TBI-induced changes in brain activity, addressing the critical need to protect and treat active-duty personnel who are at high risk of TBI. Astrocyte reprogramming is a therapeutic approach and potential solution to treating TBI that has gained attention in recent years in Alzheimer's and Parkinson's diseases, with the goal of replacing the loss of neurons by reprogramming astrocytes into neurons. This is an attractive approach for TBI; however, the lack of clinical translation for this therapy may be due to inadequate understanding of whether brain-activity abnormalities are repaired. Here we address whether reprogrammed astrocytes can form neural-network activity and if reprogramming is specific. That is, does chemical reprogramming equally affect healthy and TBI-induced reactive astrocytes or is it more selective in reprogramming reactive astrocytes? Having demonstrated the efficacy and selectivity of chemical reprogramming of astrocytes, future studies will need to examine whether these reprogrammed cells can restore circuit structure and brain activity, allowing military personnel to return to active duty following TBI with no further risk, or does the approach alter circuit structure to restore activity. The latter, a temporary compensation mechanism, may require further monitoring of injured military personnel to see whether they are at risk of long-term neurological and psychological consequences. Our long-term goal is to use this novel experimental conceptual framework (i.e., human-relevant MEA platform and computational tools) to meet future national-security challenges, screening for novel and existing drug candidates (e.g., neuroregenerative drugs) for brain-related diseases and injury. LLNL has ongoing efforts and strong capabilities in high-performance computing (HPC) and machine-learning tools to speed up drug discovery for cancer and neurotoxicants, and actively participates in the Accelerating Therapeutic Opportunities for Medicine (ATOM) consortium. Future efforts will identify drug candidates using HPC and machine-learning tools during the early drug-discovery phase (e.g., to predict safety, pharmacokinetics, and efficacy) and down select promising candidates that can be screened on our human-relevant brain MPS, with the goal of accelerating the "bench-to-bedside" drug-discovery process for TBI, which aligns with both DOE and NNSA missions.
Publications, Presentations, and Patents
Lam, D. et al. 2021. "Do Reprogrammed Brain Cells Hold the Key to Healing Damaged Networks after Traumatic Brain Injury?" Journal of Neurotrauma 38, no. 14: A70 (2021).
Lam, D. et al. 2021. "Functional Assessment of a Novel 3D Human Brain-on-a-Chip System." Presentation, NASA Human Research Program Investigators' Workshop. Virtual. January 2021.
Lam, D. et al. 2022. "Dose-dependent consequences of sub-chronic fentanyl exposure on neuron and glial co-cultures." Frontiers in Toxicology 4 (2022); https://doi.org/10.3389/ftox.2022.983415.
Ge, L. et al. 2020. "In Vivo Neuroregeneration to Treat Ischemic Stroke Through NeuroD1 AAV-Based Gene Therapy in Adult Non-Human Primates." Front Cell Dev Biol 8: 590008 (2020); doi.org/10.3389/fcell.2020.590008.