The contribution of initial concussive forces and resulting acrolein surge to ß-amyloid accumulation and functional alterations in neuronal networks using a TBI-on-a-chip model.

Trauma-induced Alzheimer's disease (AD) is rapidly emerging as a major consequence of traumatic brain injuries (TBI), with devastating social and economic impacts. Unfortunately, few treatment options are currently available due to a limited understanding of the underlying mechanisms. A clinically-relevant, in vitro experimental model that emulates in vivo scenarios with high levels of spatial and temporal resolution is critical for demystifying the pathways of post-TBI AD. Using a unique, recently established "TBI-on-a-chip" system with murine cortical networks, we demonstrate the correlative elevation of oxidative stress (acrolein), inflammation (TNF-α), and Aß42 aggregation, with concomitant reduction of neuronal network electrical activity post-concussive impact. These findings confirm that TBI-on-a-chip could provide a novel paradigm to supplement in vivo studies of trauma, while simultaneously validating the interaction of these alleged, key-pathological factors in post-TBI AD development. Specifically, we have shown that acrolein, acting as a diffusive factor of secondary injury, is both critical and sufficient in promoting inflammation (TNF-α) and Aß42 aggregation, two known contributors of AD pathogenesis. Furthermore, using a cell-free preparation with TBI-on-a-chip, we have confirmed that both force and acrolein can independently and directly stimulate the aggregation of purified Aß42, highlighting the key capabilities of primary and secondary injury mechanisms towards inducing Aß42 aggregation, independently and synergistically. In addition to morphological and biochemical assessment, we also demonstrate parallel monitoring of neuronal network activity, further validating the chief pathological role of acrolein in not only inflicting biochemical abnormalities, but also functional deficits in neuronal networks. In conclusion, through this line of investigations, we have shown that by recapitulating clinically-relevant events, the TBI-on-a-chip device is capable of quantitatively characterizing parallel force-dependent increases in oxidative stress, inflammation, protein aggregation, and network activity, offering a unique platform for mechanistic investigations of post-TBI AD, and trauma-induced neuronal injury in general. It is expected that this model could provide crucial insights into pathological mechanisms which will be critical in developing novel, effective diagnostics and treatment strategies that significantly benefit TBI victims.

Targeting the Corticospinal Tract in Neonatal Rats with a Double-Viral Vector using Combined Brain and Spine Surgery.

Successfully tackling the obstacles that constrain research on neonatal rats is important for studying the differences in outcomes seen in pediatric spinal cord injuries (SCIs) compared to adult SCIs. In addition, reliably introducing therapies into the target cells of the central nervous system (CNS) can be challenging, and inaccuracies can compromise the efficacy of the study or therapy. This protocol combines viral vector technology with a novel surgical technique to accurately introduce gene therapies into neonatal rats at postnatal day 5. Here, a virus engineered for retrograde transport (retroAAV2) of Cre is introduced at the axon terminals of corticospinal neurons in the spinal cord, where it is subsequently transported to the cell bodies. A double-floxed inverted orientation (DIO) designer receptor exclusively activated by designer drug(s) (DREADD) virus is then injected into the somatomotor cortex of the brain. This double-infection technique promotes the expression of the DREADDs only in the co-infected corticospinal tract (CST) neurons. Thus, the simultaneous co-injection of the somatomotor cortex and cervical CST terminals is a valid method for studying the chemogenetic modulation of recovery following cervical SCI models in neonatal rats.