Anatomical and Functional Changes to the Colonic Neuromuscular Compartment after Experimental Spinal Cord Injury

Dysfunction of pancreatic exocrine secretion after experimental spinal cord injury

Pancreatic exocrine dysfunction is an underdiagnosed comorbidity in individuals living with spinal cord injury (SCI) who often present cholestasis, acute pancreatitis or high levels of serum pancreatic enzymes. Parasympathetic control of pancreatic exocrine secretion (PES) is mediated in the medullary dorsal vagal complex in part through cholecystokinin (CCK) release. Our previous reports indicate high thoracic (T3-) SCI reduces vagal afferent sensitivity to GI regulatory peptides, like CCK and thyrotropin releasing hormone (TRH). To date, the effects of experimental SCI on PES are unknown. Here we investigated the modulation of PES following T3-SCI in rats. We measured PES volume and amylase concentration in control and T3-SCI rats (3-days or 3-weeks after injury) following: (i) intra-duodenal administration of a mixed-nutrient liquid meal (Ensure® ™) or (ii) central TRH injection (100 pmol) in the dorsal motor nucleus of the vagus. In a separate cohort of overnight-fasted rats, basal serum amylase levels were measured. The baseline volume of PES secretion was lower in 3-week rats destined to receive Ensure® or TRH following T3-SCI surgery compared to control. PES protein concentration was significantly reduced at baseline in 3-week T3-SCI and elevated in 3-day and 3-week T3-SCI rats postprandially but only elevated in 3-day rats following TRH microinjection. Serum amylase activity levels were elevated in 3-day T3-SCI rats and remained at similar levels post 3-weeks T3-SCI. Our data suggest that vagally-mediated regulation of multiple visceral organs is disrupted in the days and weeks following experimental SCI.

Complete High Thoracic Spinal Cord Injury Causes Bowel Dysfunction in Mice

Bowel dysfunction, is a prevalent and life-impacting comorbidity of spinal cord injury (SCI) with no long-term treatment available. SCI-induced colon changes including motility and fibrosis are understudied as are strategies to address SCI bowel dysfunction. This need remains partly due to the lack of a mouse model that recapitulates the human condition. We hypothesized that a high thoracic spinal transection in mice would trigger bowel dysfunction with coincident colon pathology similar to humans and rats after SCI. We observed bowel dysfunction as increased fecal pellet numbers within the colon, smaller pellet size, and decreased motility. Fecal pellets numbers in the colon increased significantly in SCI animals versus sham (laminectomy only) injuries by 4 days postinjury (dpi) and persisted to 7 and 21 dpi. The number of pellets expelled (fecal output) significantly decreased in SCI versus sham animals at both 7 and 20 dpi. Pellet size was significantly decreased in SCI animals at 7 and 14 dpi, collectively indicative of decreased motility with SCI. SCI caused non-significant reductions in colonic motility (bead expulsion assay) at all three timepoints. Through ex vivo myograph analyses of live colon sections, we detected significant increase in the maximal contractility of the circular musculature from both the proximal and distal colon after SCI at 21 dpi. At the same time point, distal colons displayed significant collagen deposition in the musculature after SCI. Collectively, these findings demonstrate bowel dysfunction immediately after injury that continues in the distal colon over time. Establishing this mouse model enables further interrogation using transgenic models.

Diversity of intestinal microbiota and inflammatory cytokines after severe trauma

Accumulating evidence has reported that the intestinal microbiota could play important roles in the occurrence and progression of severe trauma. However, the hypothesized potential targeted intestinal microbiota to mediate and regulate the levels of inflammatory cytokines and promote rapid recovery of body after severe trauma remains unclear. This study was aimed to explore the changes and correlation of intestinal microbiota and inflammatory cytokines in rats with severe crush and fracture trauma. The controlled laboratory study design was used, and a crush and fracture severe trauma rat model was established. 16S rRNA high-throughput gene sequencing and ELISA were used to analyze the changes in intestinal microbiota and inflammatory cytokines within one week after trauma. The correlation between intestinal microbiota and inflammatory cytokines was also analyzed. Loss of overall diversity and expansion of intestinal microbiota in the rats due to severe trauma was observed. Specifically, there was a significant increase in the abundance of Muribaculaceae [LDA (Linear Discriminant Analysis)-value = 4.814, P = 0.014] after severe trauma, while Prevotella (LDA-value = 5.235, P = 0.020) and Alloprevotella (LDA-value = 4.443, P = 0.015) were slightly lower in the trauma group than in the control group. The levels of inflammatory cytokines (IL-1α, IL-6, IL-8 and TNF-α) in the trauma group decreased from the first day to the third day and continued to increase until one week after the trauma. Prevotellaceae_UCG_001 was correlated with TNF-a (R = 0.411, P = 0.033); Lactobacillus was negatively correlated with IL-6 (R = - 0.434, P = 0.024) and IL-1α (R = - 0.419, P = 0.030) and positively correlated with IL-8 (R = 0.391, P = 0.045); and Lachnospiraceae_NK4A136_group (R = - 0.559, P = 0.027) and Muribaculaceae (R = - 0.568, P = 0.024) were negatively correlated with IL-8. Severe trauma shows stress-like activities by negatively modulating intestinal microbiota and affecting certain inflammatory cytokines contributing to host health, which implies that the regulation of potentially targeted intestinal microbiota, and further mediating and maintaining the homeostasis of inflammatory cytokines, is expected to promote the accelerating recovery of the body after severe trauma.

Biomarker expression level changes within rectal gut-associated lymphoid tissues in spinal cord-injured rats

Neurogenic bowel dysfunction (NBD) is common after spinal cord injury (SCI). Gut-associated lymphoid tissue (GALT), an organized structure within the mucosal immune system, is important for the maintenance of gut homeostasis and body health and serves as the first line barrier/defense against diet antigens, commensal microbiota, pathogens, and toxins in mucosal areas. The current study examined gene expression levels along six segments of anorectal tissue using real-time polymerase chain reaction (RT-PCR) in uninjured rats (28-day sham surgical controls) and at both 28- and 42-days post-T9 contusion injury. Consistent with our previous report of functional regional differences in the ano-rectum, we demonstrate the existence of GALTs located primarily within the segment at 3-4.5 cm from the rectal dentate line (termed rectal GALTs-rGALTs) in shams with upregulated gene expression levels of multiple biomarkers, including B cell and T cell-related genes, major histocompatibility complex (MHC) class II molecules, and germinal center (GC)-related genes, which was further confirmed by histologic examination. In the same rectal tissue segment following T9 SCI, inflammation-related genes were upregulated at 28 days post-injury (DPI) indicating that microbial infection and inflammation of rGALTs modified structure and function of rGALTs, while at 42 DPI rGALTs exhibited resolution of inflammation and impaired structure/function for extrafollicular B cell responses. Taken together, our data suggest that rGALTs exists in rat rectum for homeostasis of gut microbiota/barrier. SCI induces microbial infection and inflammation in rectal tissues containing rGALTs, which could contribute to development of SCI-related gut microbiome dysbiosis, NBD, and systemic diseases.

Regional Heterogeneity in Intestinal Epithelial Barrier Permeability and Mesenteric Perfusion After Thoracic Spinal Cord Injury

BACKGROUND

Spinal cord injury (SCI) disrupts intestinal barrier function, thereby increasing antigen permeation and leading to poor outcomes. Despite the intestinal tract's anatomic and physiologic heterogeneity, studies following SCI have not comprehensively addressed intestinal pathophysiology with regional specificity.

AIMS AND METHODS

We used an experimental model of high thoracic SCI to investigate (1) regional mucosal oxidative stress using dihydroethidium labeling; (2) regional paracellular permeability to small- and large-molecular probes via Ussing chamber; (3) regional intestinal tight junction (TJ) protein expression; and (4) hindgut perfusion via the caudal mesenteric artery.

RESULTS

Dihydroethidium staining was significantly elevated within duodenal mucosa at 3-day post-SCI. Molar flux of [14C]-urea was significantly elevated in duodenum and proximal colon at 3-day post-SCI, while molar flux of [3H]-inulin was significantly elevated only in duodenum at 3-day post-SCI. Barrier permeability was mirrored by a significant increase in the expression of pore-forming TJ protein claudin-2 in duodenum and proximal colon at 3-day post-SCI. Claudin-2 expression remained significantly elevated in proximal colon at 3-week post-SCI. Expression of the barrier-forming TJ protein occludin was significantly reduced in duodenum at 3-day post-SCI. Caudal mesenteric artery flow was unchanged by SCI at 3 days or 3 weeks despite significant reductions in mean arterial pressure.

CONCLUSION

These data show that T3-SCI provokes elevated mucosal oxidative stress, altered expression of TJ proteins, and elevated intestinal barrier permeability in the proximal intestine. In contrast, mucosal oxidative stress and intestinal barrier permeability were unchanged in the hindgut after SCI. This regional heterogeneity may result from differential sensitivity to reduced mesenteric perfusion, though further studies are required to establish a causal link. Understanding regional differences in intestinal pathophysiology is essential for developing effective treatments and standards of care for individuals with SCI.

Diet-microbiome interactions promote enteric nervous system resilience following spinal cord injury

Spinal cord injury (SCI) results in numerous systemic dysfunctions, including intestinal dysmotility and enteric nervous system (ENS) atrophy. The ENS has capacity to recover following perturbation, yet intestinal pathologies persist. With emerging evidence demonstrating SCI-induced alterations to gut microbiome composition, we hypothesized that microbiome modulation contributes to post-injury enteric recovery. Here, we show that intervention with the dietary fiber, inulin, prevents SCI-induced ENS atrophy and dysmotility in mice. While SCI-associated microbiomes and specific injury-sensitive gut microbes are not sufficient to modulate intestinal dysmotility after injury, intervention with microbially-derived short-chain fatty acid (SCFA) metabolites prevents ENS dysfunctions in injured mice. Notably, inulin-mediated resilience is dependent on IL-10 signaling, highlighting a critical diet-microbiome-immune axis that promotes ENS resilience post-injury. Overall, we demonstrate that diet and microbially-derived signals distinctly impact ENS survival after traumatic spinal injury and represent a foundation to uncover etiological mechanisms and future therapeutics for SCI-induced neurogenic bowel.

Rapid-Onset, Short-Duration Induction of Colorectal Contractions in Anesthetized, Adult, Male Rats

Substantial clinical and preclinical evidence indicates that transient receptor potential vanilloid 1 (TRPV1) receptors are expressed on terminals of colorectal chemoreceptors and mechanoreceptors and are involved in various rectal hypersensitivity disorders with common features of colorectal overactivity. These stimulatory properties of TRPV1 receptors on colorectal function suggested that brief stimulation of TRPV1 might provide a means of pharmacologically activating the colorectum to induce defecation in patients with an "unresponsive" colorectum. The current studies explored the basic features of TRPV1 receptor-induced contractions of the colorectum in anesthetized rats with and without acute spinal cord injury (aSCI). Cumulative concentration-response curves to intrarectal (IR) capsaicin (CAP) solutions (0.003%-3.0%) were performed in anesthetized aSCI and spinal intact rats. CAP produced an "inverted U," cumulative concentration-response curve with a threshold for inducing colorectal contractions at 0.01% and a peak response at 0.1% and slight decreases in responses up to 3%. Decreases in responses with concentrations >0.1% are due to a rapid desensitization (i.e., ≤30 minutes) of TRPV1 receptors to each successive dose. Desensitization appeared fully recovered within 24 hours in spinal intact rats. Colorectal contractions were completely blocked by atropine, indicating a reflexogenic activation of parasympathetic neurons, and responses were completely unaffected by a neurokinin 2 receptor antagonist, indicating that release of neurokinin A from afferent terminals and subsequent direct contractions of the smooth muscle was not involved. IR administration of three other TRPV1 receptor agonists produced similar results as CAP. SIGNIFICANCE STATEMENT: Individuals with spinal cord injury often lose control of defecation. Time-consuming bowel programs using digital stimulation of the rectum are used to empty the bowel. This study shows that intrarectal administration of the transient receptor potential vanilloid 1 (TRPV1) receptor agonist, capsaicin, can induce rapid-onset, short-duration colorectal contractions capable of inducing defecation in spinal cord injured and intact rats. Therefore, TRPV1 agonists show promise as potential therapeutics to induce defecation in individuals with neurogenic bowel.

Diet-microbiome interactions promote enteric nervous system resilience following spinal cord injury

Spinal cord injury (SCI) results in a plethora of physiological dysfunctions across all body systems, including intestinal dysmotility and atrophy of the enteric nervous system (ENS). Typically, the ENS has capacity to recover from perturbation, so it is unclear why intestinal pathophysiologies persist after traumatic spinal injury. With emerging evidence demonstrating SCI-induced alterations to the gut microbiome composition, we hypothesized that modulation of the gut microbiome could contribute to enteric nervous system recovery after injury. Here, we show that intervention with the dietary fiber, inulin prevents ENS atrophy and limits SCI-induced intestinal dysmotility in mice. However, SCI-associated microbiomes and exposure to specific SCI-sensitive gut microbes are not sufficient to modulate injury-induced intestinal dysmotility. Intervention with microbially-derived short-chain fatty acid (SCFA) metabolites prevents ENS dysfunctions and phenocopies inulin treatment in injured mice, implicating these microbiome metabolites in protection of the ENS. Notably, inulin-mediated resilience is dependent on signaling by the cytokine IL-10, highlighting a critical diet-microbiome-immune axis that promotes ENS resilience following SCI. Overall, we demonstrate that diet and microbially-derived signals distinctly impact recovery of the ENS after traumatic spinal injury. This protective diet-microbiome-immune axis may represent a foundation to uncover etiological mechanisms and future therapeutics for SCI-induced neurogenic bowel.

System failure: Systemic inflammation following spinal cord injury

Spinal cord injury (SCI) affects hundreds of thousands of people in the United States, and while some effects of the injury are broadly recognized (deficits to locomotion, fine motor control, and quality of life), the systemic consequences of SCI are less well-known. The spinal cord regulates systemic immunological and visceral functions; this control is often disrupted by the injury, resulting in viscera including the gut, spleen, liver, bone marrow, and kidneys experiencing local tissue inflammation and physiological dysfunction. The extent of pathology depends on the injury level, severity, and time post-injury. In this review, we describe immunological and metabolic consequences of SCI across several organs. Since infection and metabolic disorders are primary reasons for reduced lifespan after SCI, it is imperative that research continues to focus on these deleterious aspects of SCI to improve life span and quality of life for individuals with SCI.

Immune Status of Individuals with Traumatic Spinal Cord Injury: A Systematic Review and Meta-Analysis

Individuals with spinal cord injury (SCI) have higher infection rates compared to those without SCI. In this review, the immune status difference between individuals with and without traumatic SCI is investigated by examining their peripheral immune cells and markers. PubMed, Cochrane, EMBASE, and Ovid MEDLINE were searched without language or date restrictions. Studies reporting peripheral immune markers' concentration and changes in functional capabilities of immune cells that compared individuals with and without SCI were included. Studies with participants with active infection, immune disease, and central nervous system (CNS) immune markers were excluded. The review followed the PRISMA guidelines. Effect estimates were measured by Weighted Mean Difference (WMD) using a random-effects model. Study quality was assessed using the National Heart, Lung, and Blood Institute Quality Assessment Tool. Fifty-four studies (1813 with SCI and 1378 without SCI) contributed to the meta-analysis. Leukocytes (n = 23, WMD 0.78, 95% CI 0.17; 1.38, I2 83%), neutrophils (n = 11, WMD 0.76, 95% CI 0.09; 1.42, I2 89%), C-reactive protein (CRP) (n = 12, WMD 2.25, 95% CI 1.14; 3.56, I2 95%), and IL6 (n = 13, WMD 2.33, 95% CI 1.20; 3.49, I2 97%) were higher in individuals with SCI vs. without SCI. Clinical factors (phase of injury, completeness of injury, sympathetic innervation impairment, age, sex) and study-related factors (sample size, study design, and serum vs. plasma) partially explained heterogeneity. Immune cells exhibited lower functional capability in individuals with SCI vs. those without SCI. Most studies (75.6%) had a moderate risk of bias. The immune status of individuals with SCI differs from those without SCI and is clinically influenced by the phase of injury, completeness of injury, sympathetic innervation impairment, age, and sex. These results provide information that is vital for monitoring and management strategies to effectively improve the immune status of individuals with SCI.

Plasticity of colonic enteric nervous system following spinal cord injury in male and female rats

BACKGROUND

Neurogenic bowel is a dysmotility disorder following spinal cord injury (SCI) that negatively impacts quality of life, social integration, and physical health. Colonic transit is directly modulated by the enteric nervous system. Interstitial Cells of Cajal (ICC) distributed throughout the small intestine and colon serve as specialized pacemaker cells, generating rhythmic electrical slow waves within intestinal smooth muscle, or serve as an interface between smooth muscle cells and enteric motor neurons of the myenteric plexus. Interstitial Cells of Cajal loss has been reported for other preclinical models of dysmotility, and our previous experimental SCI study provided evidence of reduced excitatory and inhibitory enteric neuronal count and smooth muscle neural control.

METHODS

Immunohistochemistry for the ICC-specific marker c-Kit was utilized to examine neuromuscular remodeling of the distal colon in male and female rats with experimental SCI.

KEY RESULTS

Myenteric plexus ICC (ICC-MP) exhibited increased cell counts 3 days following SCI in male rats, but did not significantly increase in females until 3 weeks after SCI. On average, ICC-MP total primary arborization length increased significantly in male rats at 3-day, 3-week, and 6-week time points, whereas in females, this increase occurred most frequently at 6 weeks post-SCI. Conversely, circular muscle ICC (ICC-CM) did not demonstrate post-SCI changes.

CONCLUSIONS AND INFERENCES

These data demonstrate resiliency of the ICC-MP in neurogenic bowel following SCI, unlike seen in other related disease states. This plasticity underscores the need to further understand neuromuscular changes driving colonic dysmotility after SCI in order to advance therapeutic targets for neurogenic bowel treatment.

Region-specific remodeling of the enteric nervous system and enteroendocrine cells in the colon of spinal cord injury patients

Patients with spinal cord injury (SCI) suffer from major bowel dysfunction, whose exact pathophysiology, particularly the involvement of the enteric nervous system or epithelial dysfunction is poorly understood. Herein, we aimed to characterize the mucosal biopsies of the right and left colon in SCI patients vs controls (CT): (1) remodeling of key enteric neurotransmitters, (2) remodeling of enteroendocrine cells, and (3) mucosal inflammation compared to those in controls. In SCI, mucosal ACh concentration was lower in the right colon as compared to CT, but no change was observed in the left colon, and AChE expression was lower in both the right and left colons than in CT. While the VIP concentration was similar in the right and left colons, VIP mRNA expression was increased in the right colon and decreased in the left colon, in SCI patients as compared to CT. Interestingly, 5-HT concentration was reduced in the left colon but not in the right colon in SCI patients. Moreover, in SCI patients, as compared to CT, SERT mRNA expression was selectively increased in the left colon while TPH1 mRNA expression was increased in the right and left colons. Although mucosal TNFα and IL-1β mRNA expression did not significantly differ between SCI and CT groups, we identified a significant positive correlation between TNFα and IL-1β mRNA expression and left colon transit time in the SCI group. In conclusion, region-specific changes occur in the enteric neurotransmitter, serotonergic, and inflammatory pathways in the colon of SCI patients. The significant correlations between these pathways and clinical parameters in the left colon further set a scientific basis for designing therapeutic targets to improve colonic motor dysfunction in patients.Biobank information: Spinal cord injury patients: PHRC ConstiCAPE-clinical trial NCT02566746. Controls: Anosain-clinical trial NCT03054415 and biobank of the "Institut des Maladies de l'Appareil Digestif (IMAD)" registered under number DC-2008-402.

Autogenic biofeedback training improves autonomic responses in a participant with cervical motor complete spinal cord injury- case report

STUDY DESIGN

Single-subject case design OBJECTIVE: To evaluate the Autogenic Feedback Training Exercise (AFTE) on autonomic nervous system responses.

INTRODUCTION

AFTE combines specific autogenic exercises with biofeedback of multiple physiological responses. Originally developed by the National Aeronautics and Space Administration (NASA), AFTE is used to improve post-flight orthostatic intolerance and motion sickness in astronauts. Individuals with cervical or upper thoracic spinal cord injury (SCI) often present symptoms of autonomic dysfunction similar to astronauts. We hypothesize that AFTE challenges nervous system baroreflex, gastric and vascular responses often impaired after SCI.

METHODS

Using a modified AFTE protocol, we trained a hypotensive female participant with cervical motor complete (C5/6-AIS A) SCI, and a male non-injured control participant (NI) and measured blood pressure (BP), heart rate (HR), gastric electrical activity, and microvascular blood volume before, during and after AFTE. The participants were instructed to complete breathing and imagery exercises to help facilitate relaxation. Subsequently, they were instructed to use stressful imagery and breathing exercises during arousal trials.

RESULTS

Both participants completed 8 sessions of approximately 45 min each. Microvascular blood volume decreased 23% (SCI) and 54% (NI) from the beginning to the end of the stimulation cycles. The participant with SCI became progressively more normotensive and improved levels of gastric electrical activity, while the NI participant's changes in HR, gastric electrical activity, and BP were negligible.

CONCLUSIONS

AFTE may offer a novel non-pharmacologic intervention to minimize symptoms of dysautonomia in people with SCI.

Direct electrical stimulation impacts on neuromuscular junction morphology on both stimulated and unstimulated contralateral soleus

BACKGROUND

There is increasing evidence of crosstalk between organs. The neuromuscular junction (NMJ) is a peripheral chemical synapse whose function and morphology are sensitive to acetylcholine (ACh) release and muscle depolarization. In an attempt to improve our understanding of NMJ plasticity and muscle crosstalk, the effects of unilateral direct electrical stimulation of a hindlimb muscle on the NMJ were investigated in rats exposed long-term post-synaptic neuromuscular blockade.

METHODS

Sprague Dawley rats were subjected to post-synaptic blockade of neuromuscular transmission by systemic administration of α-cobrotoxin and mechanically ventilated for up to 8 days and compared with untreated sham operated controls and animals exposed to unilateral chronic electrical stimulation 12 h/day for 5 or 8 days.

RESULTS

NMJs produced axonal and glial sprouts (growth of processes that extend beyond the confines of the synapse defined by high-density aggregates of acetylcholine receptors [AChRs]) in response to post-synaptic neuromuscular blockade, but less than reported after peripheral denervation or pre-synaptic blockade. Direct electrical soleus muscle stimulation reduced the terminal Schwann cell (tSC) and axonal sprouting in both stimulated and non-stimulated contralateral soleus. Eight days chronic stimulation reduced (P < 0.001) the number of tSC sprouts on stimulated and non-stimulated soleus from 6.7 ± 0.5 and 6.9 ± 0.5 sprouts per NMJ, respectively, compared with 10.3 ± 0.9 tSC per NMJ (P < 0.001) in non-stimulated soleus from rats immobilized for 8 days. A similar reduction of axonal sprouts (P < 0.001) was observed in stimulated and non-stimulated contralateral soleus in response to chronic electrical stimulation. RNAseq-based gene expression analyses confirmed a restoring effect on both stimulated and unstimulated contralateral muscle. The cross-over effect was paralleled by increased cytokine/chemokine levels in stimulated and contralateral unstimulated muscle as well as in plasma.

CONCLUSIONS

Motor axon terminals and terminal Schwann cells at NMJs of rats subjected to post-synaptic neuromuscular blockade exhibited sprouting responses. These axonal and glial responses were likely dampened by a muscle-derived myokines released in an activity-dependent manner with both local and systemic effects.

Circuit reconstruction of newborn neurons after spinal cord injury in adult rats via an NT3-chitosan scaffold

An implanted neurotrophin-3 (NT3)-chitosan scaffold can recruit endogenous neural stem cells to migrate to a lesion region and differentiate into mature neurons after adult spinal cord injury (SCI). However, the identities of these newborn neurons and whether they can form functional synapses and circuits to promote recovery after paraplegia remain unknown. By using combined advanced technologies, we revealed here that the newborn neurons of several subtypes received synaptic input from the corticospinal tract (CST), rubrospinal tract (RST), and supraspinal tracts. They formed a functional neural circuit at the injured spinal region, further driving the local circuits beneath the lesion. Our results showed that the NT3-chitosan scaffold facilitated the maturation of spinal neurons and the reestablishment of the spinal neural circuit in the lesion region 12 weeks after SCI. Transsynaptic virus experiments revealed that these newborn spinal neurons received synaptic connections from the CST and RST and drove the neural circuit beneath the lesion via newly formed synapses. These re-established circuits successfully recovered the formation and function of the neuromuscular junction (NMJ) beneath the lesion spinal segments. These findings suggest that the NT3-chitosan scaffold promotes the formation of relay neural circuits to accommodate various types of brain descending inputs and facilitate functional recovery after paraplegia.

BDNF Spinal Overexpression after Spinal Cord Injury Partially Protects Soleus Neuromuscular Junction from Disintegration, Increasing VAChT and AChE Transcripts in Soleus but Not Tibialis Anterior Motoneurons

After spinal cord transection (SCT) the interaction between motoneurons (MNs) and muscle is impaired, due to reorganization of the spinal network after a loss of supraspinal inputs. Rats subjected to SCT, treated with intraspinal injection of a AAV-BDNF (brain-derived neurotrophic factor) construct, partially regained the ability to walk. The central effects of this treatment have been identified, but its impact at the neuromuscular junction (NMJ) has not been characterized. Here, we compared the ability of NMJ pre- and postsynaptic machinery in the ankle extensor (Sol) and flexor (TA) muscles to respond to intraspinal AAV-BDNF after SCT. The gene expression of cholinergic molecules (VAChT, ChAT, AChE, nAChR, mAChR) was investigated in tracer-identified, microdissected MN perikarya, and in muscle fibers with the use of qPCR. In the NMJs, a distribution of VAChT, nAChR and Schwann cells was studied by immunofluorescence, and of synaptic vesicles and membrane active zones by electron microscopy. We showed partial protection of the Sol NMJs from disintegration, and upregulation of the VAChT and AChE transcripts in the Sol, but not the TA MNs after spinal enrichment with BDNF. We propose that the observed discrepancy in response to BDNF treatment is an effect of difference in the TrkB expression setting BDNF responsiveness, and of BDNF demands in Sol and TA muscles.

Traumatic spinal cord injury and the contributions of the post-injury microbiome

Spinal cord injuries are an enormous burden on injured individuals and their caregivers. The pathophysiological effects of injury are not limited to the spine and limb function, but affect numerous body systems. Growing observations in human studies and experimental models suggest that the gut microbiome is altered following spinal cord injury. Given the importance of signals derived from the gut microbiome for host physiology, it is possible that injury-triggered dysbiosis subsequently affects aspects of recovery. Here, we review emerging literature on the role of the microbiome following spinal cord injury. Specifically, we highlight findings from both human and experimental studies that correlate taxonomic changes to aspects of injury recovery. Examination of both observational and emerging interventional studies supports the notion that future therapeutic avenues for spinal cord injury pathologies may lie at the interface of the host and indigenous microbes.

Bowel and Bladder Care in Patients With Spinal Cord Injury

Complete and incomplete spinal cord injuries affect between 250,000 and 500,000 people on an annual basis worldwide. In addition to sensory and motor dysfunction, spinal cord injury patients also suffer from associated conditions such as neurogenic bowel and bladder dysfunction. The degree of dysfunction varies on the level, degree, and type of spinal cord injury that occurs. In addition to the acute surgical treatment of these patients, spine surgeons should understand how to manage neurogenic bowel and bladder care on both a short- and long-term basis to minimize the risk for complications and optimize potential for rehabilitation.

Spinal cord injury-mediated changes in electrophysiological properties of rat gastric nodose ganglion neurons

In preclinical rodent models, spinal cord injury (SCI) manifests as gastric vagal afferent dysfunction both acutely and chronically. However, the mechanism that underlies this dysfunction remains unknown. In the current study, we examined the effect of SCI on gastric nodose ganglia (NG) neuron excitability and on voltage-gated Na⁺ (Na_V) channels expression and function in rats after an acute (i.e. 3-days) and chronic (i.e. 3-weeks) period. Rats randomly received either T3-SCI or sham control surgery 3-days or 3-weeks prior to experimentation as well as injections of 3% DiI solution into the stomach to identify gastric NG neurons. Single cell qRT-PCR was performed on acutely dissociated DiI-labeled NG neurons to measure Na_V1.7, Na_V1.8 and Na_V1.9 expression levels. The results indicate that all 3 channel subtypes decreased. Current- and voltage-clamp whole-cell patch-clamp recordings were performed on acutely dissociated DiI-labeled NG neurons to measure active and passive properties of C- and A-fibers as well as the biophysical characteristics of Na_V1.8 channels in gastric NG neurons. Acute and chronic SCI did not demonstrate deleterious effects on either passive properties of dissociated gastric NG neurons or biophysical properties of Na_V1.8. These findings suggest that although Na_V gene expression levels change following SCI, Na_V1.8 function is not altered. The disruption throughout the entirety of the vagal afferent neuron has yet to be investigated.

Electroacupuncture modulates the intestinal microecology to improve intestinal motility in spinal cord injury rats

Spinal cord injury (SCI) is a disease involving gastrointestinal disorders. The underlying mechanisms of the potential protective effects of electroacupuncture (EA) and 5-hydroxytryptamine (5-HT) system on SCI remain unknown. We investigated whether EA improves gut microbial dysbiosis in SCI and regulates the 5-HT system. 16S rDNA gene sequencing was applied to investigate alterations in the gut microbiome of the rats. Faecal metabolites and the expression of the 5-HT system were detected. EA and faecal microbiota transplantation (FMT) treatment facilitated intestinal transmission functional recovery and restored the colon morphology of SCI rats. The composition of the intestinal microbiota, including numbers of phylum Proteobacteria, class Clostridia, order Bacteroidales, and genus Dorea, were amplified in SCI rats, and EA and FMT significantly reshaped the intestinal microbiota. SCI resulted in disturbed metabolic conditions in rats, and the EA and FMT group showed increased amounts of catechin compared with SCI rats. SCI inhibited 5-HT system expression in the colon, which was significantly reversed by EA and FMT treatment. Therefore, EA may ameliorate SCI by modulating microbiota and metabolites and regulate the 5-HT system. Our study provides new insights into the pathogenesis and therapy of SCI from the perspective of microbiota and 5-HT regulation.

Factors impacting bowel symptoms in a contemporary spinal cord injury cohort: results from the Neurogenic Bladder Research Group Registry

STUDY DESIGN

Cross sectional.

OBJECTIVES

To identify variables associated with severe bowel symptoms in spinal cord injured people.

SETTING

National cohort.

METHODS

Adult spinal cord injured (SCI) people were recruited for an online registry and 1373 were included for analysis. Univariate analysis and logistic regression was used to evaluate associations between severity of bowel symptoms and variables. Bowel symptoms were assessed by the Neurogenic Bowel Dysfunction (NBD) score and patients scoring ≥14 were categorized as having severe bowel symptoms. Autonomic dysreflexia (AD) severity was measured using a six item questionnaire and reported as total AD score (0-24). Bladder management was categorized as: voiding, clean intermittent catheterization (CIC), surgery (augmentation/diversion) or indwelling catheter.

RESULTS

Severe bowel symptoms were reported in 570 (42%) On multivariable logistic regression, every point increase of AD total score was associated with 5% increased odds of having more severe bowel symptoms [OR 1.05 95% CI 1.03-1.10]. Type of bladder management was also associated with more severe symptoms (p = 0.0001). SCI people with indwelling catheters (OR = 2.16, 95% CI 1.40-3.32) or reconstructive surgery (OR = 1.79, 95% CI 1.08-3.32) were almost twice as likely to report more severe bowel symptoms than those performing CIC.

Spinal Cord Injury Changes the Structure and Functional Potential of Gut Bacterial and Viral Communities

Emerging data indicate that gut dysbiosis contributes to many human diseases, including several comorbidities that develop after traumatic spinal cord injury (SCI). To date, all analyses of SCI-induced gut dysbiosis have used 16S rRNA amplicon sequencing. This technique has several limitations, including being susceptible to taxonomic "blind spots," primer bias, and an inability to profile microbiota functions or identify viruses. Here, SCI-induced gut dysbiosis was assessed by applying genome- and gene-resolved metagenomic analysis of murine stool samples collected 21 days after an experimental SCI at the 4th thoracic spine (T4) or 10th thoracic spine (T10) spinal level. These distinct injuries partially (T10) or completely (T4) abolish sympathetic tone in the gut. Among bacteria, 105 medium- to high-quality metagenome-assembled genomes (MAGs) were recovered, with most (n = 96) representing new bacterial species. Read mapping revealed that after SCI, the relative abundance of beneficial commensals (Lactobacillus johnsonii and CAG-1031 spp.) decreased, while potentially pathogenic bacteria (Weissella cibaria, Lactococcus lactis _A, Bacteroides thetaiotaomicron) increased. Functionally, microbial genes encoding proteins for tryptophan, vitamin B6, and folate biosynthesis, essential pathways for central nervous system function, were reduced after SCI. Among viruses, 1,028 mostly novel viral populations were recovered, expanding known murine gut viral species sequence space ∼3-fold compared to that of public databases. Phages of beneficial commensal hosts (CAG-1031, Lactobacillus, and Turicibacter) decreased, while phages of pathogenic hosts (Weissella, Lactococcus, and class Clostridia) increased after SCI. Although the microbiomes and viromes were changed in all SCI mice, some of these changes varied as a function of spinal injury level, implicating loss of sympathetic tone as a mechanism underlying gut dysbiosis.IMPORTANCE To our knowledge, this is the first article to apply metagenomics to characterize changes in gut microbial population dynamics caused by a clinically relevant model of central nervous system (CNS) trauma. It also utilizes the most current approaches in genome-resolved metagenomics and viromics to maximize the biological inferences that can be made from these data. Overall, this article highlights the importance of autonomic nervous system regulation of a distal organ (gut) and its microbiome inhabitants after traumatic spinal cord injury (SCI). By providing information on taxonomy, function, and viruses, metagenomic data may better predict how SCI-induced gut dysbiosis influences systemic and neurological outcomes after SCI.

Effect of fecal microbiota transplantation on neurological restoration in a spinal cord injury mouse model: involvement of brain-gut axis

BACKGROUND

Spinal cord injury (SCI) patients display disruption of gut microbiome, and gut dysbiosis exacerbate neurological impairment in SCI models. Cumulative data support an important role of gut microbiome in SCI. Here, we investigated the hypothesis that fecal microbiota transplantation (FMT) from healthy uninjured mice into SCI mice may exert a neuroprotective effect.

RESULTS

FMT facilitated functional recovery, promoted neuronal axonal regeneration, improved animal weight gain and metabolic profiling, and enhanced intestinal barrier integrity and GI motility in SCI mice. High-throughput sequencing revealed that levels of phylum Firmicutes, family Christensenellaceae, and genus Butyricimonas were reduced in fecal samples of SCI mice, and FMT remarkably reshaped gut microbiome. Also, FMT-treated SCI mice showed increased amount of fecal short-chain fatty acids (SCFAs), which correlated with alteration of intestinal permeability and locomotor recovery. Furthermore, FMT downregulated IL-1β/NF-κB signaling in spinal cord and NF-κB signaling in gut following SCI.

CONCLUSION

Our study demonstrates that reprogramming of gut microbiota by FMT improves locomotor and GI functions in SCI mice, possibly through the anti-inflammatory functions of SCFAs. Video Abstract.

Erythropoietin promotes functional recovery in a mouse model of postoperative ileus

BACKGROUND

Dysmotility and postoperative ileus (POI) are major clinical problems after surgical trauma and it is associated with increased intestinal inflammation and oxidative stress. Despite the high occurrence of POI following intra-abdominal surgeries, no effective treatment is currently available. Erythropoietin (EPO) is a multifunctional tissue-protective cytokine with potent anti-inflammatory and anti-oxidative properties, and it is an FDA approved medicine for clinical use. While both EPO and EPO receptors (EPOR) are widely expressed in the gut, the role of EPO in POI is largely unknown. This study was designed to explore the possible beneficial effect of EPO in a mouse model of POI.

METHODS

Mice were subjected to intestinal manipulation to induce standard POI and intestinal transit time was determined at 24-h post-injury with or without EPO treatment (5000 units/kg, once, IP, immediately after intestinal trauma). Intestinal samples were harvested for histological and immunohistochemical analysis.

RESULTS

Systemic EPO significantly improved intestinal transit time compared with control group and it was associated with significantly increased levels of tissue macrophages and reduced levels of oxidative stress.

CONCLUSIONS AND INFERENCES

This is the first pre-clinical study to document novel beneficial effects of EPO in gut dysmotility and our findings suggest that the beneficial effects of EPO in POI is predominantly mediated by its anti-oxidative and immunomodulatory properties.

Spinal cord injury and gut microbiota: A review

After spinal cord injury (SCI), intestinal dysfunction has a serious impact on physical and mental health, quality of life, and social participation. Recent data from rodent and human studies indicated that SCI causes gut dysbiosis. Remodeling gut microbiota could be beneficial for the recovery of intestinal function and motor function after SCI. However, few studies have explored SCI with focus on the gut microbiota and "microbiota-gut-brain" axis. In this review, the complications following SCI, including intestinal dysfunction, anxiety and depression, metabolic disorders, and neuropathic pain, are directly or indirectly related to gut dysbiosis, which may be mediated by "gut-brain" interactions. Furthermore, we discuss the research strategies that can be beneficial in this regard, including germ-free animals, fecal microbiota transplantation, probiotics, phages, and brain imaging techniques. The current microbial research has shifted from descriptive to mechanismal perspective, and future research using new technologies may further demonstrate the pathophysiological mechanism of association of SCI with gut microbiota, elucidate the mode of interaction of gut microbiota and hosts, and help develop personalized microbiota-targeted therapies and drugs based on microbiota or corresponding metabolites.

Enteric Nervous System Remodeling in a Rat Model of Spinal Cord Injury: A Pilot Study

The physiopathology of digestive disorders in patients with spinal cord injury (SCI) remains largely unknown, particularly the involvement of the enteric nervous system (ENS). We aimed in a rat model of chronic thoracic SCI to characterize (1) changes in the neurochemical coding of enteric neurons and their putative consequences upon neuromuscular response, and (2) the inflammatory response of the colon. Ex vivo motility of proximal and distal colon segments of SCI and control (CT) rats were studied in an organ chamber in response to electrical field stimulation (EFS) and bethanechol. Immunohistochemical analysis of proximal and distal segments was performed using antibodies again Hu, neuronal nitric oxide synthase, (nNOS), and choline acetyltransferase. Colonic content of acetylcholine and acetylcholinesterase was measured; messenger RNA (mRNA) expression of inflammatory cytokines was measured using reverse transcription quantitative polymerase chain reaction (RT-qPCR) approaches. Compared with the CT rats, the contractile response to bethanechol was significantly decreased in the proximal colon of SCI rats but not in the distal colon. The proportion of nNOS immunoreactive (IR) neurons was significantly reduced in the proximal but not distal colon of SCI rats. No change in proportion of choline acetyltransferase (ChAT)-IR was reported; the tissue concentration of acetylcholine was significantly decreased in the proximal colon of SCI rats. The expression of tumor necrosis factor alpha (TNF-α) and intercellular adhesion molecule-1 (ICAM-1) was significantly reduced in the proximal and distal colon of SCI rats. This study demonstrates that functional motor and enteric neuroplastic changes affect preferentially the proximal colon compared with the distal colon. The underlying mechanisms and factors responsible for these changes remain to be discovered.

Investigation of Bowel Function with Anorectal Manometry in a Rat Spinal Cord Contusion Model

Bowel dysfunction after chronic spinal cord injury (SCI) is a common source of morbidity and rehospitalization. Typical complications include constipation, fecal impaction, incontinence, abdominal distention, autonomic dysreflexia, and the necessity of interventions (i.e., suppositories, digital stimulation) to defecate. Numerous surveys have confirmed that the remediation of bowel complications is more highly valued for quality of life than improvements in walking. Much of what is known about bowel function after SCI for diagnosis and research in humans has been gained using anorectal manometry (ARM) procedures. However, ARM has been underutilized in pre-clinical animal work. Therefore, a novel combination of outcome measures was examined in the current study that incorporates functional output of the bowel (weekly fecal measurements), weight gain (pre-injury to terminal weight), and terminal ARM measurement with external anal sphincter electromyography under urethane anesthesia. The results indicate higher fecal output after contusion during the sub-acute period (4-7 days) post-injury, changes in the composition of the feces, and functionally obstructive responses in a specific section of the rectum (increased baseline pressure, increased frequency of contraction, and reduced ability to trigger a giant contraction to a distension stimulus). These results demonstrate significant bowel dysfunction in the rodent SCI contusion model that is consistent with data from human research. Thus, the combined measurement protocol enables the detection of changes and can be used, with minimal cost, to assess effectiveness of therapeutic interventions on bowel complications.

Acute Colonic Pseudo-Obstruction After Posterior Spinal Fusion: A Case Report and Literature Review

BACKGROUND

Acute colonic pseudo-obstruction (ACPO) or Ogilvie's syndrome occurs in 0.22%-7% of patients undergoing surgery, with a mortality of up to 46%. ACPO increased median hospital days versus control in spinal surgery (14 vs. 6 days; P < 0.001). If defined as postoperative ileus, the incidence was 7%-13.4%. Postoperative ileus is associated with 2.9 additional hospital days and an $80,000 increase in cost per patient. We present a case of ACPO in an adult patient undergoing spinal fusion for correction of scoliosis and review the available literature to outline clinical characteristics and surgical outcomes.

CASE DESCRIPTION

The patient was a 31-year-old woman with untreated advanced scoliosis with no history of neurologic issues. T2-L3 spinal instrumentation and fusion was completed. Plain abdominal radiography showed of dilated cecum 11 cm and the department of general surgery was consulted. Neostigmine administration was planned after conservative treatment failure after transfer to the intensive care unit. The patient was discharged home with no recurrence >60 days. Thirty cases were found in our literature review using PubMed and Embase databases and summarized.

CONCLUSIONS

Of 30 cases reviewed, only 3 cases of ACPO were specific to patients undergoing spinal fusion for scoliosis. According to the literature, 20% of patients had resolution with conservative treatment, 40% with neostigmine, and 30% with surgical intervention. Other noninvasive treatments may have similar efficacy in preventing complications leading to surgical invention. Sixty clinical trials and 9 systematic reviews were summarized with an updated management algorithm.

Diminished enteric neuromuscular transmission in the distal colon following experimental spinal cord injury

Neurogenic bowel following spinal cord injury (SCI) leads to decreased colonic motility, remodeling of the neuromuscular compartment and results in chronic evacuation difficulties. The distal colon of the rat serves a dual role for fluid absorption and storage that is homologous to the descending colon of humans. Dysmotility of the descending colon is one component of neurogenic bowel. We investigated the integrity of the enteric neuromuscular transmission responsible for the generation of excitatory and inhibitory junction potentials (EJPs and IJPs, respectively) in the distal colon of rats. We previously demonstrated a chronic reduction in colonic enteric neurons from rats with acute and chronic high-thoracic (T3) SCI and hypothesized that neurogenic bowel following T3-SCI results from diminished enteric neuromuscular transmission. Immunohistochemical labeling for myenteric neuronal nitric oxide synthase (nNOS) and choline acetyltransferase (ChAT) neurons demonstrated a significant loss of presumptive nitric oxide (NO) and acetylcholine (ACh) immunoreactive neurons in both 3-day and 3-week injured animals. Colonic neuromuscular transmission in response to transmural electrical stimulation of the colon was significantly reduced 3-days and 3-weeks following SCI in male rats. Specifically, cholinergic-mediated excitatory junction potentials (EJPs) and nitrergic-mediated slow inhibitory junction potentials (IJPs) were significantly reduced while ATP-mediated fast IJPs remained unaffected. We conclude that a reduction in excitatory and inhibitory enteric neuromuscular transmission contributes to neurogenic bowel observed following SCI, and that these loss-of-function changes involve enteric-mediated cholinergic and nitrergic pathways.

Chronic, Twice-Daily Dosing of an NK2 Receptor Agonist [Lys5,MeLeu9,Nle10]-NKA(4-10), Produces Consistent Drug-Induced Micturition and Defecation in Chronic Spinal Rats

Acute administration of [Lys5,Me,Leu9,Nle10]-NKA(4-10) (LMN-NKA) produces contractions of the detrusor and rectum with voiding in intact and acutely spinal cord injured (SCI) rats. In the current study, the ability of LMN-NKA (10 μg/kg or 100 μg/kg, subcutaneous [SC], twice a day [bid]) or vehicle to induce voiding and defecation in chronic SCI rats was examined across 30 days. After the last day of administration, voiding response rates and bladder pressure (BP) responses to LMN-NKA (intravenous [IV] and SC) were evaluated under anesthesia. In conscious rats, LMN-NKA (100 μg/kg) produced dose-dependent micturition within 5 min, with response rates >90%, and voiding efficiency >80% in males and >60% in females, which remained stable across the 1-month test period. Similarly, LMN-NKA administration rapidly induced defecation, which also remained stable. Under anesthesia, LMN-NKA increased BP, voiding efficiency, and voiding response rates, which reached 100% at 3 and 10 μg/kg IV in males and females, respectively. SC administration produced 100% response rates in males (30 μg/kg) but only 71% in females (100 μg/kg). Efficacy in rats chronically treated with LMN-NKA was similar to naïve and vehicle-treated rats, except for reduced voiding efficiency in chronically dosed female rats (100 μg/kg). No differences in bladder weights or collagen-to-smooth muscle ratios in histological sections were seen between the groups. Thus neither tolerance, nor sensitization, to LMN-NKA-induced micturition and defecation occurs with chronic administration in rats with chronic SCI. Efficacy was higher in male than in female rats.

Muscarinic receptor 1 allosteric modulators stimulate colorectal emptying in dog, mouse and rat and resolve constipation

BACKGROUND

Because M1 muscarinic receptors are expressed by enteric neurons, we investigated whether positive allosteric modulators of these receptors (M1PAMs) would enhance colorectal propulsion and defecation in dogs, mice, and rats.

METHODS

The potencies of the M1PAMs, T662 or T523, were investigated using M1 receptor-expressing CHO cells. Effectiveness of M1PAMs on defecation was investigated by oral administration in mice and rats, by recording propulsive contractions in anaesthetized rats and by recording high amplitude propagating contractions in dogs.

KEY RESULTS

PAM EC50 values in M1 receptor-expressing CHO cells were 0.7-1.8 nmol/L for T662 and 8-10 nmol/L for T523. The compounds had 1000-fold lower potencies as agonists. In anesthetized rats, both compounds elicited propulsive colorectal contractions, and in dogs, mice, and rats, oral administration increased fecal output. No adverse effects were observed in conscious animals. M1PAMs triggered propagated high amplitude contractions and caused defecation in dogs. Nerve-mediated contractions were enhanced in the isolated mouse colon. M1PAMs were equi-effective in rats with or without the pelvic nerves being severed. In two models of constipation in mice, opiate-induced constipation and constipation of aging, defecation was induced and constipation was reversed.

CONCLUSION AND INFERENCES

M1PAMs act at targets sites in the colorectum to enhance colorectal propulsion. They are effective across species, and they reverse experimentally induced constipation. Previous studies have shown that they are safe in human. Because they provide an enhancement of physiological control rather than being direct agonists, they are predicted to provide effective treatment for constipation.

Gastrointestinal dysfunction after spinal cord injury

The gastrointestinal tract of vertebrates is a heterogeneous organ system innervated to varying degrees by a local enteric neural network as well as extrinsic parasympathetic and sympathetic neural circuits located along the brainstem and spinal axis. This diverse organ system serves to regulate the secretory and propulsive reflexes integral to the digestion and absorption of nutrients. The quasi-segmental distribution of the neural circuits innervating the gastrointestinal (GI) tract produces varying degrees of dysfunction depending upon the level of spinal cord injury (SCI). At all levels of SCI, GI dysfunction frequently presents life-long challenges to individuals coping with injury. Growing attention to the profound changes that occur across the entire physiology of individuals with SCI reveals profound knowledge gaps in our understanding of the temporal dimensions and magnitude of organ-specific co-morbidities following SCI. It is essential to understand and identify these broad pathophysiological changes in order to develop appropriate evidence-based strategies for management by clinicians, caregivers and individuals living with SCI. This review summarizes the neurophysiology of the GI tract in the uninjured state and the pathophysiology associated with the systemic effects of SCI.

Recommendations for evaluation of bladder and bowel function in pre-clinical spinal cord injury research

Objective: In order to encourage the inclusion of bladder and bowel outcome measures in preclinical spinal cord injury (SCI) research, this paper identifies and categorizes 1) fundamental, 2) recommended, 3) supplemental and 4) exploratory sets of outcome measures for pre-clinical assessment of bladder and bowel function with broad applicability to animal models of SCI.Methods: Drawing upon the collective research experience of autonomic physiologists and informed in consultation with clinical experts, a critical assessment of currently available bladder and bowel outcome measures (histological, biochemical, in vivo functional, ex vivo physiological and electrophysiological tests) was made to identify the strengths, deficiencies and ease of inclusion for future studies of experimental SCI.Results: Based upon pre-established criteria generated by the Neurogenic Bladder and Bowel Working Group that included history of use in experimental settings, citations in the literature by multiple independent groups, ease of general use, reproducibility and sensitivity to change, three fundamental measures each for bladder and bowel assessments were identified. Briefly defined, these assessments centered upon tissue morphology, voiding efficiency/volume and smooth muscle-mediated pressure studies. Additional assessment measures were categorized as recommended, supplemental or exploratory based upon the balance between technical requirements and potential mechanistic insights to be gained by the study.Conclusion: Several fundamental assessments share reasonable levels of technical and material investment, including some that could assess bladder and bowel function non-invasively and simultaneously. Such measures used more inclusively across SCI studies would advance progress in this high priority area. When complemented with a few additional investigator-selected study-relevant supplemental measures, they are highly recommended for research programs investigating the efficacy of therapeutic interventions in preclinical animal models of SCI that have a bladder and/or bowel focus.

Investigating neurogenic bowel in experimental spinal cord injury: where to begin?

The devastating losses following traumatic spinal cord injury (SCI) encompass the motor, sensory and autonomic nervous systems. Neurogenic bowel is a slow transit colonic dysfunction marked by constipation, rectal evacuation difficulties, decreased anorectal sensation, fecal incontinence or some combination thereof. Furthermore, neurogenic bowel is one of the most prevalent comorbidities of SCI and is recognized by afflicted individuals and caregivers as a lifelong physical and psychological challenge that profoundly affects quality of life. The restoration of post-injury control of movement has received considerable scientific scrutiny yet the daily necessity of voiding the bowel and bladder remains critically under-investigated. Subsequently, physicians and caregivers are rarely presented with consistent, evidence-based strategies to successfully address the consequences of dysregulated voiding reflexes. Neurogenic bowel is commonly believed to result from the interruption of the supraspinal control of the spinal autonomic circuits regulating the colon. In this mini-review, we discuss the clinical challenges presented by neurogenic bowel and emerging pre-clinical evidence that is revealing that SCI also initiates functional remodeling of the colonic wall concurrent with a decrease in local enteric neurons. Since the enteric input to the colonic smooth muscle is the final common pathway for functional contractions of the colon, changes to the neuromuscular interface must first be understood in order to maximize the efficacy of therapeutic interventions targeting colonic dysfunction following SCI.

Reduced colonic smooth muscle cholinergic responsiveness is associated with impaired bowel motility after chronic experimental high-level spinal cord injury

The mechanisms underlying bowel dysfunction after high-level spinal cord injury (SCI) are poorly understood. However, impaired supraspinal sympathetic and parasympathetic control is likely a major contributing factor. Disruption of the descending autonomic pathways traversing the spinal cord was achieved by a T3 complete spinal cord transection, and colonic function was examined in vivo and ex vivo four weeks post-injury. Total gastrointestinal transit time (TGTT) was reduced and contractility of the proximal and distal colon was impaired due to reduced M₃ receptor sensitivity. These data describe a clinically relevant model of bowel dysfunction after SCI.