MicroRNA-based engineered mesenchymal stem cell extracellular vesicles to treat visual deficits after blast-induced trauma.

Our previous studies have shown the benefit of intravitreal injection of a mesenchymal stem cell (MSC)- derived secretome to treat visual deficits in a mild traumatic brain injury (mTBI) mouse model. In this study, we have addressed whether MSC-derived extracellular vesicles (EV) overexpressing miR424, which particularly targets neuroinflammation, show similar benefits in the mTBI model. Adult C57BL/6 mice were subjected to a 50-psi air pulse on the left side, overlying the forebrain, resulting in mTBI.

Sphingolipid changes in mouse brain and plasma after mild traumatic brain injury at the acute phases.

Background: Traumatic brain injury (TBI) causes neuroinflammation and can lead to long-term neurological dysfunction, even in cases of mild TBI (mTBI). Despite the substantial burden of this disease, the management of TBI is precluded by an incomplete understanding of its cellular mechanisms. Sphingolipids (SPL) and their metabolites have emerged as key orchestrators of biological processes related to tissue injury, neuroinflammation, and inflammation resolution.

Raloxifene Mitigates Emotional Deficits after Mild Traumatic Brain Injury in Mice.

Persons with mild traumatic brain injury (TBI) often exhibit persistent emotional impairments, particularly depression, fearfulness, and anxiety, that significantly diminish quality of life. Studying these mood disorders in animal models of mild TBI can help provide insight into possible therapies. We have previously reported that mice show increased depression, fearfulness, and anxiety, as well as visual and motor deficits, after focal cranial blast and that treatment with the cannabinoid type 2 receptor (CB2) inverse agonist, SMM-189, reduces these deficits.

A Long-Term Safety and Efficacy Report on Intravitreal Delivery of Adipose Stem Cells and Secretome on Visual Deficits After Traumatic Brain Injury.

Purpose: We compared intravitreal injection of human adipose stem cell concentrated conditioned media (ASC-CCM) to injection of live ASCs for their long-term safety and effectiveness against the visual deficits of mild traumatic brain injury (mTBI).

Methods: We first tested different intravitreal ASC doses for safety. Other C57BL/6 mice then received focal cranial blast mTBI and were injected with the safe ASC dose (1000 cells/eye), ASC-CCM (∼200 ng protein/eye), or saline solution.

Raloxifene, a cannabinoid type-2 receptor inverse agonist, mitigates visual deficits and pathology and modulates microglia after ocular blast.

Visual deficits after ocular blast injury (OBI) are common, but pharmacological approaches to improve long-term outcomes have not been identified. Blast forces frequently damage the retina and optic nerves, and work on experimental animals has shown the pro-inflammatory actions of microglia can further exacerbate such injuries. Cannabinoid type-2 receptor (CB2) inverse agonists specifically target activated microglia, biasing them away from the harmful pro-inflammatory M1 state toward the helpful reparative M2 state.

Mesenchymal stem cell secretome protects against oxidative stress-induced ocular blast visual pathologies.

Visual deficits are a common concern among subjects with head trauma. Stem cell therapies have gained recent attention in treating visual deficits following head trauma. Previously, we have shown that adipose-derived stem cell (ASC) concentrated conditioned medium (ASC-CCM), when delivered via an intravitreal route, yielded a significant improvement in vision accompanied by a decrease in retinal neuroinflammation in a focal cranial blast model that indirectly injures the retina.

Raloxifene Modulates Microglia and Rescues Visual Deficits and Pathology After Impact Traumatic Brain Injury.

Mild traumatic brain injury (TBI) involves widespread axonal injury and activation of microglia, which initiates secondary processes that worsen the TBI outcome. The upregulation of cannabinoid type-2 receptors (CB2) when microglia become activated allows CB2-binding drugs to selectively target microglia. CB2 inverse agonists modulate activated microglia by shifting them away from the harmful pro-inflammatory M1 state toward the helpful reparative M2 state and thus can stem secondary injury cascades.

Systemic Elevation of n-3 Polyunsaturated Fatty Acids (n-3-PUFA) Is Associated with Protection against Visual, Motor, and Emotional Deficits in Mice following Closed-Head Mild Traumatic Brain Injury.

Traumatic brain injury (TBI) causes neuroinflammation and neurodegeneration leading to various pathological complications such as motor and sensory (visual) deficits, cognitive impairment, and depression. N-3 polyunsaturated fatty acid (n-3 PUFA) containing lipids are known to be anti-inflammatory, whereas the sphingolipid, ceramide (Cer), is an inducer of neuroinflammation and degeneration. Using Fat1-transgenic mice that contain elevated levels of systemic n-3 PUFA, we tested whether they are resistant to mild TBI-mediated sensory-motor and emotional deficits by subjecting Fat1-transgenic mice and their WT littermates to focal cranial air blast (50 psi) or sham blast (0 psi, control).

Role of the superior salivatory nucleus in parasympathetic control of choroidal blood flow and in maintenance of retinal health.

The vasodilatory pterygopalatine ganglion (PPG) innervation of the choroid is under the control of preganglionic input from the superior salivatory nucleus (SSN), the parasympathetic portion of the facial motor nucleus. We sought to confirm that choroidal SSN drives a choroid-wide vasodilation and determine if such control is important for retinal health. To the former end, we found, using transscleral laser Doppler flowmetry, that electrical activation of choroidal SSN significantly increased choroidal blood flow (ChBF), at a variety of choroidal sites that included more posterior as well as more anterior ones.

Adipose Tissue-Derived Mesenchymal Stem Cell Concentrated Conditioned Medium Alters the Expression Pattern of Glutamate Regulatory Proteins and Aquaporin-4 in the Retina after Mild Traumatic Brain Injury.

Concentrated conditioned media from adipose tissue-derived mesenchymal stem cells (ASC-CCM) show promise for retinal degenerative diseases. In this study, we hypothesized that ASC-CCM could rescue retinal damage and thereby improve visual function by acting through Müller glia in mild traumatic brain injury (mTBI). Adult C57Bl/6 mice were subjected to a 50-psi air pulse on the left side of the head, resulting in an mTBI.

Progressive long-term spatial memory loss following repeat concussive and subconcussive brain injury in mice, associated with dorsal hippocampal neuron loss, microglial phenotype shift, and vascular abnormalities.

There is considerable concern about the long-term deleterious effects of repeat head trauma on cognition, but little is known about underlying mechanisms and pathology. To examine this, we delivered four air blasts to the left side of the mouse cranium, a week apart, with an intensity that causes deficits when delivered singly and considered "concussive," or an intensity that does not yield significant deficits when delivered singly and considered "subconcussive." Neither repeat concussive nor subconcussive blast produced spatial memory deficits at 4 months, but both yielded deficits at 14 months, and dorsal hippocampal neuron loss.

TSG-6 in conditioned media from adipose mesenchymal stem cells protects against visual deficits in mild traumatic brain injury model through neurovascular modulation.

Background: Retinal inflammation affecting the neurovascular unit may play a role in the development of visual deficits following mild traumatic brain injury (mTBI). We have shown that concentrated conditioned media from adipose tissue-derived mesenchymal stem cells (ASC-CCM) can limit retinal damage from blast injury and improve visual function. In this study, we addressed the hypothesis that TNFα-stimulated gene-6 (TSG-6), an anti-inflammatory protein released by mesenchymal cells, mediates the observed therapeutic potential of ASCs via neurovascular modulation.

Amelioration of visual deficits and visual system pathology after mild TBI via the cannabinoid Type-2 receptor inverse agonism of raloxifene.

Visual deficits after traumatic brain injury (TBI) are common, but interventions that limit the post-trauma impairments have not been identified. We have found that treatment with the cannabinoid type-2 receptor (CB2) inverse agonist SMM-189 for 2 weeks after closed-head blast TBI greatly attenuates the visual deficits and retinal pathology this otherwise produces in mice, by modulating the deleterious role of microglia in the injury process after trauma. SMM-189, however, has not yet been approved for human use.

Amelioration of visual deficits and visual system pathology after mild TBI with the cannabinoid type-2 receptor inverse agonist SMM-189.

Mild TBI is often accompanied by visual system dysfunction and injury, which is at least partly caused by microglial neuroinflammatory processes initiated by the injury. Using our focal cranial blast mouse model of closed-skull mild TBI, we evaluated the ability of the cannabinoid type-2 (CB2) receptor inverse agonist SMM-189, which biases microglia from the harmful M1 state to the beneficial M2 state, to mitigate visual system dysfunction and injury after TBI. Male C57BL/6 or Thy1-EYFP reporter mice received a closed-head blast of either 0-psi (sham) or 50-psi to the left side of the cranium.

Defective Choroidal Blood Flow Baroregulation and Retinal Dysfunction and Pathology Following Sympathetic Denervation of Choroid.

Purpose: We sought to determine if sympathetic denervation of choroid impairs choroidal blood flow (ChBF) regulation and harms retina.

Methods: Rats received bilateral superior cervical ganglionectomy (SCGx), which depleted choroid of sympathetic but not parasympathetic innervation. The flash-evoked scotopic ERG and visual acuity were measured 2 to 3 months after SCGx, and vasoconstrictive ChBF baroregulation during high systemic arterial blood pressure (ABP) induced by LNAME was assessed by laser Doppler flowmetry (LDF).

Neural control of choroidal blood flow.

The choroid is richly innervated by parasympathetic, sympathetic and trigeminal sensory nerve fibers that regulate choroidal blood flow in birds and mammals, and presumably other vertebrate classes as well. The parasympathetic innervation has been shown to vasodilate and increase choroidal blood flow, the sympathetic input has been shown to vasoconstrict and decrease choroidal blood flow, and the sensory input has been shown to both convey pain and thermal information centrally and act locally to vasodilate and increase choroidal blood flow. As the choroid lies behind the retina and cannot respond readily to retinal metabolic signals, its innervation is important for adjustments in flow required by either retinal activity, by fluctuations in the systemic blood pressure driving choroidal perfusion, and possibly by retinal temperature.

Abnormalities in Dynamic Brain Activity Caused by Mild Traumatic Brain Injury Are Partially Rescued by the Cannabinoid Type-2 Receptor Inverse Agonist SMM-189.

Mild traumatic brain injury (mTBI) can cause severe long-term cognitive and emotional deficits, including impaired memory, depression, and persevering fear, but the neuropathological basis of these deficits is uncertain. As medial prefrontal cortex (mPFC) and hippocampus play important roles in memory and emotion, we used multi-site, multi-electrode recordings of oscillatory neuronal activity in local field potentials (LFPs) in awake, head-fixed mice to determine if the functioning of these regions was abnormal after mTBI, using a closed-skull focal cranial blast model. We evaluated mPFC, hippocampus CA1, and primary somatosensory/visual cortical areas (S1/V1).

Stimulation of Baroresponsive Parts of the Nucleus of the Solitary Tract Produces Nitric Oxide-mediated Choroidal Vasodilation in Rat Eye.

Preganglionic parasympathetic neurons of the ventromedial part of the superior salivatory nucleus (SSN) mediate vasodilation of orbital and choroidal blood vessels, via their projection to the nitrergic pterygopalatine ganglion (PPG) neurons that innervate these vessels. We recently showed that the baroresponsive part of the nucleus of the solitary tract (NTS) innervates choroidal control parasympathetic preganglionic neurons of SSN in rats. As this projection provides a means by which blood pressure (BP) signals may modulate choroidal blood flow (ChBF), we investigated if activation of baroresponsive NTS evokes ChBF increases in rat eye, using Laser Doppler Flowmetry (LDF) to measure ChBF transclerally.

Mild Traumatic Brain Injury Produces Neuron Loss That Can Be Rescued by Modulating Microglial Activation Using a CB2 Receptor Inverse Agonist.

We have previously reported that mild TBI created by focal left-side cranial blast in mice produces widespread axonal injury, microglial activation, and a variety of functional deficits. We have also shown that these functional deficits are reduced by targeting microglia through their cannabinoid type-2 (CB2) receptors using 2-week daily administration of the CB2 inverse agonist SMM-189. CB2 inverse agonists stabilize the G-protein coupled CB2 receptor in an inactive conformation, leading to increased phosphorylation and nuclear translocation of the cAMP response element binding protein (CREB), and thus bias activated microglia from a pro-inflammatory M1 to a pro-healing M2 state.

Disinhibition of neurons of the nucleus of solitary tract that project to the superior salivatory nucleus causes choroidal vasodilation: Implications for mechanisms underlying choroidal baroregulation.

Preganglionic neurons in the superior salivatory nucleus (SSN) that mediate parasympathetic vasodilation of choroidal blood vessels receive a major excitatory input from the baroresponsive part of the nucleus of the solitary tract (NTS). This input appears likely to mediate choroidal vasodilation during systemic hypotension, which prevents decreases in choroidal blood flow (ChBF) due to reduced perfusion pressure. It is uncertain, however, how low blood pressure signals to NTS from the aortic depressor nerve (ADN), which fires at a low rate during systemic hypotension, could yield increased firing in the NTS output to SSN.

A Novel Closed-Head Model of Mild Traumatic Brain Injury Using Focal Primary Overpressure Blast to the Cranium in Mice.

Mild traumatic brain injury (TBI) from focal head impact is the most common form of TBI in humans. Animal models, however, typically use direct impact to the exposed dura or skull, or blast to the entire head. We present a detailed characterization of a novel overpressure blast system to create focal closed-head mild TBI in mice.

The identification and neurochemical characterization of central neurons that target parasympathetic preganglionic neurons involved in the regulation of choroidal blood flow in the rat eye using pseudorabies virus, immunolabeling and conventional pathway tracing methods.

The choroidal blood vessels of the eye provide the main vascular support to the outer retina. These blood vessels are under parasympathetic vasodilatory control via input from the pterygopalatine ganglion (PPG), which in turn receives its preganglionic input from the superior salivatory nucleus (SSN) of the hindbrain. The present study characterized the central neurons projecting to the SSN neurons innervating choroidal PPG neurons, using pathway tracing and immunolabeling.

A novel closed-body model of spinal cord injury caused by high-pressure air blasts produces extensive axonal injury and motor impairments.

Diffuse axonal injury is thought to be the basis of the functional impairments stemming from mild traumatic brain injury. To examine how axons are damaged by traumatic events, such as motor vehicle accidents, falls, sports activities, or explosive blasts, we have taken advantage of the spinal cord with its extensive white matter tracts. We developed a closed-body model of spinal cord injury in mice whereby high-pressure air blasts targeted to lower thoracic vertebral levels produce tensile, compressive, and shear forces within the parenchyma of the spinal cord and thereby cause extensive axonal injury.

Differential organization of cortical inputs to striatal projection neurons of the matrix compartment in rats.

In prior studies, we described the differential organization of corticostriatal and thalamostriatal inputs to the spines of direct pathway (dSPNs) and indirect pathway striatal projection neurons (iSPNs) of the matrix compartment. In the present electron microscopic (EM) analysis, we have refined understanding of the relative amounts of cortical axospinous vs. axodendritic input to the two types of SPNs.

Motor, visual and emotional deficits in mice after closed-head mild traumatic brain injury are alleviated by the novel CB2 inverse agonist SMM-189.

We have developed a focal blast model of closed-head mild traumatic brain injury (TBI) in mice. As true for individuals that have experienced mild TBI, mice subjected to 50-60 psi blast show motor, visual and emotional deficits, diffuse axonal injury and microglial activation, but no overt neuron loss. Because microglial activation can worsen brain damage after a concussive event and because microglia can be modulated by their cannabinoid type 2 receptors (CB2), we evaluated the effectiveness of the novel CB2 receptor inverse agonist SMM-189 in altering microglial activation and mitigating deficits after mild TBI.