Protocol to Prepare Single-Cell Suspensions from Mouse Vagal Sensory Ganglia for Transcriptomic Studies

Spinal cord injury-induced neurogenic bowel: A role for host-microbiome interactions in bowel pain and dysfunction

Background and aims

Spinal cord injury (SCI) affects roughly 300,000 Americans with 17,000 new cases added annually. In addition to paralysis, 60% of people with SCI develop neurogenic bowel (NB), a syndrome characterized by slow colonic transit, constipation, and chronic abdominal pain. The knowledge gap surrounding NB mechanisms after SCI means that interventions are primarily symptom-focused and largely ineffective. The goal of the present studies was to identify mechanism(s) that initiate and maintain NB after SCI as a critical first step in the development of evidence-based, novel therapeutic treatment options.

Methods

Following spinal contusion injury at T9, we observed alterations in bowel structure and function reflecting key clinical features of NB. We then leveraged tissue-specific whole transcriptome analyses (RNAseq) and fecal 16S rRNA amplicon sequencing in combination with histological, molecular, and functional (Ca2+ imaging) approaches to identify potential mechanism(s) underlying the generation of the NB phenotype.

Results

In agreement with prior reports focused on SCI-induced changes in the skin, we observed a rapid and persistent increase in expression of calcitonin gene-related peptide (CGRP) expression in the colon. This is suggestive of a neurogenic inflammation-like process engaged by antidromic activity of below-level primary afferents following SCI. CGRP has been shown to disrupt colon homeostasis and negatively affect peristalsis and colon function. As predicted, contusion SCI resulted in increased colonic transit time, expansion of lymphatic nodules, colonic structural and genomic damage, and disruption of the inner, sterile intestinal mucus layer corresponding to increased CGRP expression in the colon. Gut microbiome colonization significantly shifted over 28 days leading to the increase in Anaeroplasma, a pathogenic, gram-negative microbe. Moreover, colon specific vagal afferents and enteric neurons were hyperresponsive after SCI to different agonists including fecal supernatants.

Conclusions

Our data suggest that SCI results in overexpression of colonic CGRP which could alter colon structure and function. Neurogenic inflammatory-like processes and gut microbiome dysbiosis can also sensitize vagal afferents, providing a mechanism for visceral pain despite the loss of normal sensation post-SCI. These data may shed light on novel therapeutic interventions targeting this process to prevent NB development in patients.

Mesenchymal stromal cells alleviate acute respiratory distress syndrome through the cholinergic anti-inflammatory pathway

Mesenchymal stromal cells (MSCs) have been considered a promising alternative for treatment of acute respiratory distress syndrome (ARDS). However, there is significant heterogeneity in their therapeutic efficacy, largely owing to the incomplete understanding of the mechanisms underlying the therapeutic activities of MSCs. Here, we hypothesize that the cholinergic anti-inflammatory pathway (CAP), which is recognized as a neuroimmunological pathway, may be involved in the therapeutic mechanisms by which MSCs mitigate ARDS. Using lipopolysaccharide (LPS) and bacterial lung inflammation models, we found that inflammatory cell infiltration and Evans blue leakage were reduced and that the expression levels of choline acetyltransferase (ChAT) and vesicular acetylcholine transporter (VAChT) in lung tissue were significantly increased 6 hours after MSC infusion. When the vagus nerve was blocked or α7 nicotinic acetylcholine (ACh) receptor (α7nAChR)-knockout mice were used, the therapeutic effects of MSCs were significantly reduced, suggesting that the CAP may play an important role in the effects of MSCs in ARDS treatment. Our results further showed that MSC-derived prostaglandin E2 (PGE2) likely promoted ACh synthesis and release. Additionally, based on the efficacy of nAChR and α7nAChR agonists, we found that lobeline, the nicotinic cholinergic receptor excitation stimulant, may attenuate pulmonary inflammation and alleviate respiratory symptoms of ARDS patients in a clinical study (ChiCTR2100047403). In summary, we reveal a previously unrecognized MSC-mediated mechanism of CAP activation as the means by which MSCs alleviate ARDS-like syndrome, providing insight into the clinical translation of MSCs or CAP-related strategies for the treatment of patients with ARDS.

Cultures of glial cells from optic nerve of two adult teleost fish: Astatotilapia burtoni and Danio rerio

BACKGROUND

In vitro studies are very useful to increase the knowledge of different cell types and could be the key to understand cell metabolism and function. Fish optic nerves (ON) can recover visual functions by reestablishing its structure and reconnecting the axons of ganglion cells. This is because fish show spontaneous regeneration of the central nervous system which does not occur in mammals. In addition, several studies have indicated that glial cells of ON have different properties in comparison to the glial cells from brain or retina. Consequently, providing an in vitro tool will be highly beneficial to increase the knowledge of these cells.

NEW METHOD

We developed a cell culture protocol to isolate glial cells from ON of two teleost fish species, Danio rerio and Astatotilapia burtoni.

RESULTS

The optimized protocol allowed us to obtain ON cells and brain-derived cells from adult teleost fish. These cells were characterized as glial cells and their proprieties in vitro were analyzed.Comparison with Existing Method(s): Although it is striking that ON glial cells show peculiarities, their study in vitro has been limited by the only published protocol going back to the 1990s. Our protocol makes glial cells of different fish species available for experiments and studies to increase the understanding of these glial cell types.

CONCLUSIONS

This validated and effective in vitro tool increases the possibilities on studies of glial cells from fish ON which implies a reduction in animal experimentation.