MRI findings in a case of spinal cord Wallerian degeneration following trauma

The Potential Role of Inflammation in Modulating Endogenous Hippocampal Neurogenesis After Spinal Cord Injury

Currently there are approximately 291,000 people suffering from a spinal cord injury (SCI) in the United States. SCI is associated with traumatic changes in mobility and neuralgia, as well as many other long-term chronic health complications, including metabolic disorders, diabetes mellitus, non-alcoholic steatohepatitis, osteoporosis, and elevated inflammatory markers. Due to medical advances, patients with SCI survive much longer than previously. This increase in life expectancy exposes them to novel neurological complications such as memory loss, cognitive decline, depression, and Alzheimer's disease. In fact, these usually age-associated disorders are more prevalent in people living with SCI. A common factor of these disorders is the reduction in hippocampal neurogenesis. Inflammation, which is elevated after SCI, plays a major role in modulating hippocampal neurogenesis. While there is no clear consensus on the mechanism of the decline in hippocampal neurogenesis and cognition after SCI, we will examine in this review how SCI-induced inflammation could modulate hippocampal neurogenesis and provoke age-associated neurological disorders. Thereafter, we will discuss possible therapeutic options which may mitigate the influence of SCI associated complications on hippocampal neurogenesis.

SARM1 promotes neuroinflammation and inhibits neural regeneration after spinal cord injury through NF-κB signaling

Axonal degeneration is a common pathological feature in many acute and chronic neurological diseases such as spinal cord injury (SCI). SARM1 (sterile alpha and TIR motif-containing 1), the fifth TLR (Toll-like receptor) adaptor, has diverse functions in the immune and nervous systems, and recently has been identified as a key mediator of Wallerian degeneration (WD). However, the detailed functions of SARM1 after SCI still remain unclear.

Methods: Modified Allen's method was used to establish a contusion model of SCI in mice. Furthermore, to address the function of SARM1 after SCI, conditional knockout (CKO) mice in the central nervous system (CNS), SARM1^Nestin-CKO mice, and SARM1^GFAP-CKO mice were successfully generated by Nestin-Cre and GFAP-Cre transgenic mice crossed with SARM1^flox/flox mice, respectively. Immunostaining, Hematoxylin-Eosin (HE) staining, Nissl staining and behavioral test assays such as footprint and Basso Mouse Scale (BMS) scoring were used to examine the roles of SARM1 pathway in SCI based on these conditional knockout mice. Drugs such as FK866, an inhibitor of SARM1, and apoptozole, an inhibitor of heat shock protein 70 (HSP70), were used to further explore the molecular mechanism of SARM1 in neural regeneration after SCI.

Results: We found that SARM1 was upregulated in neurons and astrocytes at early stage after SCI. SARM1^Nestin-CKO and SARM1^GFAP-CKO mice displayed normal development of the spinal cords and motor function. Interestingly, conditional deletion of SARM1 in neurons and astrocytes promoted the functional recovery of behavior performance after SCI. Mechanistically, conditional deletion of SARM1 in neurons and astrocytes promoted neuronal regeneration at intermediate phase after SCI, and reduced neuroinflammation at SCI early phase through downregulation of NF-κB signaling after SCI, which may be due to upregulation of HSP70. Finally, FK866, an inhibitor of SARM1, reduced the neuroinflammation and promoted the neuronal regeneration after SCI.

Conclusion: Our results indicate that SARM1-mediated prodegenerative pathway and neuroinflammation promotes the pathological progress of SCI and anti-SARM1 therapeutics are viable and promising approaches for preserving neuronal function after SCI.

The Role of Acid-sensing Ion Channel 3 in the Modulation of Tooth Mechanical Hyperalgesia Induced by Orthodontic Tooth Movement

This study aimed to explore the role of acid-sensing ion channel 3 (ASIC3) in the modulation of tooth mechanical hyperalgesia induced by orthodontic tooth movement. In male Sprague-Dawley rats, closed coil springs were ligated between mandibular incisors and molars to mimic orthodontic tooth movement. Bite force was assessed to evaluate tooth mechanical hyperalgesia. The alveolar bone, trigeminal ganglia, and trigeminal nucleus caudalis underwent immunohistochemical staining and immunoblotting for ASIC3. The inferior alveolar nerves were transected to explore the interaction between the periodontal sensory endings and trigeminal ganglia. The role of ASIC3 in trigeminal ganglia was further explored with lentivirus-mediated ASIC3 ribonucleic acid interference. Results showed that ASIC3 was expressed in the periodontal Ruffini endings and expression of ASIC3 protein was elevated in periodontal tissues, trigeminal ganglia, and trigeminal nucleus caudalis, following orthodontic tooth movement. ASIC3 agonists and antagonists significantly aggravated and mitigated tooth mechanical hyperalgesia, respectively. ASIC3 expression decreased after inferior alveolar nerve transection in periodontal tissues. Both in vitro and vivo, the lentivirus vector carrying ASIC3 shRNA inhibited ASIC3 expression and relieved tooth mechanical hyperalgesia. To conclude, ASIC3 is important in the modulation of tooth mechanical hyperalgesia induced by orthodontic tooth movement. Further, the role of ASIC3 in the modulation of pain in periodontal tissues is regulated by trigeminal ganglia. An adjuvant analgesic therapy targeting ASIC3 could alleviate orthodontic movement-associated mechanical hyperalgesia in rats.

Discriminative clinical and neuroimaging features of motor-predominant hereditary diffuse leukoencephalopathy with axonal spheroids and primary progressive multiple sclerosis: A preliminary cross-sectional study

BACKGROUND

Hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) is a rare autosomal-dominant white matter disease, typically characterized by juvenile cognitive decline and frontoparietal white matter lesions. A portion of HDLS patients exhibit preferential motor dysfunctions as their initial symptoms, mimicking multiple sclerosis (MS). However, there is no study comparing this phenotype of HDLS and primary progressive multiple sclerosis (PPMS), which greatly resemble each other. This is the first preliminary study to clarify the clinical and neuroimaging features of motor-predominant HDLS, and compare it with PPMS, using cases whose colony stimulating factor 1 receptor (CSF1R) were sequenced.

METHODS

Clinical and radiological data from Japanese patients at the Department of Neurology, Kyushu University Hospital, Fukuoka, Japan, were evaluated retrospectively and cross-sectionally. Twenty-nine brain and 18 spinal cord magnetic resonance imaging (MRI) scans from four motor-predominant HDLS patients with CSF1R mutations and 15 PPMS patients without CSF1R mutations, were evaluated using an HDLS MRI scoring system.

RESULTS

Two patients with HDLS were initially diagnosed with MS and received immunotherapy. Clinically, motor-predominant HDLS and PPMS patients resembled each other in onset age and disability. However, motor-predominant HDLS patients had a significantly higher frequency of frontal release signs, lower positivity rates of oligoclonal IgG bands (OCB), and lower IgG index values. Total HDLS MRI scores, total white matter lesions (WMLs), and brain atrophy were similar between the diseases. However, motor-predominant HDLS patients had more marked atrophy of the corpus callosum (CC) body, more WMLs in the deep and subcortical regions of the frontoparietal lobes, fewer WMLs in the occipitotemporal periventricular regions, and more restricted diffusivity lesions on MRI than PPMS patients. There was a stronger association between disease duration and CC index in HDLS, suggesting more rapid progression compared with PPMS.

CONCLUSIONS

Motor-predominant HDLS has characteristic frequent frontal release signs, normal findings for OCB and the IgG index, severe CC body atrophy, abundant deep and subcortical WMLs in the frontoparietal lobes, subtle occipitotemporal lobe periventricular WMLs, and more restricted diffusivity lesions on MRI. Although the present study was limited by the small number of HDLS cases, we propose that immunotherapy should be avoided in such cases.