Protocol for isolating and processing mouse sciatic nerve fibers for confocal immunohistochemistry

Many motor and neurodegenerative diseases affect the peripheral nervous system (PNS). The myelinated axons in the sciatic nerves offer valuable insights into the pathology of these diseases. Here, we present a protocol for isolating and processing mouse sciatic nerves for confocal immunohistochemistry. We describe steps for mouse perfusion, removing and fixing the sciatic nerve, transferring nerves onto slides, staining, and imaging. This protocol can assist in characterizing pathologies of myelinated fibers resulting from diseases affecting the PNS. For complete details on the use and execution of this protocol, please refer to Chang et al. (2023).1.

Mouse models of human CNTNAP1-associated congenital hypomyelinating neuropathy and genetic restoration of murine neurological deficits

The Contactin-associated protein 1 (Cntnap1) mouse mutants fail to establish proper axonal domains in myelinated axons. Human CNTNAP1 mutations are linked to hypomyelinating neuropathy-3, which causes severe neurological deficits. To understand the human neuropathology and to model human CNTNAP1C323R and CNTNAP1R764C mutations, we generated Cntnap1C324R and Cntnap1R765C mouse mutants, respectively. Both Cntnap1 mutants show weight loss, reduced nerve conduction, and progressive motor dysfunction. The paranodal ultrastructure shows everted myelin loops and the absence of axo-glial junctions. Biochemical analysis reveals that these Cntnap1 mutant proteins are nearly undetectable in the paranodes, have reduced surface expression and stability, and are retained in the neuronal soma. Postnatal transgenic expression of Cntnap1 in the mutant backgrounds rescues the phenotypes and restores the organization of axonal domains with improved motor function. This study uncovers the mechanistic impact of two human CNTNAP1 mutations in a mouse model and provides proof of concept for gene therapy for CNTNAP1 patients.

Farnesol induces protection against CNS inflammatory demyelination and decreases spinal infiltration of CD4+ T-Cells

Multiple Sclerosis (MS) is an autoimmune disease that causes T-cells to attack and degrade the myelin sheath of neurons in the spinal cord and brain. Farnesol is synthesized by plants and mammals and has anti-inflammatory along with neuroprotective activities. We used the MOG35–55 induced c57BL/6 murine EAE (experimental autoimmune encephalomyelitis) model due to model’s neurodegenerative and inflammatory properties. We predicted that farnesol would protect against EAE and increase autoimmunity markers. We collected spinal cords and spleens for flow cytometry analysis at the end of the study. This study found that farnesol significantly reduced spinal infiltration of CD4+ T cells, and increased infiltration of Tregs compared to untreated mice. Interestingly the proportion of CD25+Foxp3+ was increased compared to untreated mice, and statistically significant compared to vehicle treatment. We did not observe significant changes in CD4+, or CD25+Foxp3+ frequencies in the spleens. FOL treatment showed significant increase in CD11b+F4/80+ monocyte-derived macrophages (MDM) and F4/80int granulocytes/monocytes. FOL also showed significant weight retention and reduction of disease severity compared to untreated. These findings show that farnesol helps mediate the invasion of CD4+ T cells in the EAE model. Future studies should study how farnesol affects T-cell activation and differentiation, along with affects on macrophages and dendritic cells.

This work was supported in part by the National Institutes of Health (grant R15NS107743)

Farnesol reduces T cell infiltration in murine CNS inflammatory demyelination

Farnesol (FOL) is a naturally-produced 15-carbon organic acyclic sesquiterpene alcohol (isoprenol) that acts as a potent blocker of neuronal voltage-gated Ca2+ channels (L- and N-type) and is found in the human brain. FOL has potent anti-oxidant and anti-inflammatory effects in vitro and is neuroprotective in a murine model of neurotoxicity. Because inflammation and neurodegeneration are mechanisms associated with CNS demyelinating diseases, we sought to determine whether FOL treatment would result in protection against experimental autoimmune encephalomyelitis (EAE). We compared the progression of EAE in MOG35–55 immunized female C57BL/6 mice treated orally with FOL (100 mg/kg/daily) emulsified in corn oil, versus vehicle-treated and untreated EAE mice. FOL significantly reduced the average clinical scores of EAE mice when compared to untreated mice and vehicle-treated mice. The protective effect was associated with a significant reduction of CD4+ T cell spinal cord infiltration in FOL-treated mice as assessed by flow cytometry. Although FOL’s mechanism of action remains to be known, we propose that FOL promotes protection against CNS inflammatory demyelination by promoting an anti-inflammatory effect. We compared pro-inflammatory and anti-inflammatory cytokine transcriptional levels in brain tissues of EAE mice and histological analysis of CD4+ T cell CNS infiltration and demyelination. The potential benefit of FOL nanoencapsulation in neuroprotection was explored. We demonstrate that there is a correlation between the reduced neuroinflammation and EAE severity observed in the context of FOL protection. Understanding the neuroprotective effects of FOL may provide insight to novel therapeutic approaches for MS.

Organic compound farnesol as possible inhibitor of inflammasome complex, in murine macrophages and mouse model of multiple sclerosis

Many advancements in the understanding of multiple sclerosis (MS) have been made through the use of laboratory models. One commonly used model is experimental autoimmune encephalomyelitis (EAE), a mouse model characterized by central nervous system (CNS) inflammation and demyelination, allowing for symptoms resembling some of the most prominent features of the human disease. Although the exact etiology of MS is still being investigated, experiments with EAE have shown that the NLRP3 inflammasome complex of the innate immune system is critical and necessary for disease development. The inflammasome complex can be assembled in all innate immune cells, including microglia and astrocytes in the CNS. Dysregulation of inflammasome activity can result in uncontrolled inflammation, which underlies many chronic diseases, and metabolic and autoimmune disorders such as MS. Our lab has shown that farnesol a 15-carbon organic sesquiterpene and primary alcohol, reduced EAE disease severity and onset and also decreased T-cell infiltration into the CNS. However, the mechanisms of its action have yet to be fully defined. Therefore, in-vitro work on murine macrophages is being conducted to investigate how farnesol may be potentially affecting the pathway of the inflammasome complex and providing this protection. Furthermore, since farnesol is a quorum-sensing molecule that impacts biofilm formation, other studies of ours are aimed at evaluating how farnesol affects the gut-brain axis and specifically the gut microbiome of EAE mice.