Combinatorial treatment of acute spinal cord injury with ghrelin, ibuprofen, C16, and ketogenic diet does not result in improved histologic or functional outcome

Gut microbiota and transcriptome dynamics in every-other-day fasting are associated with neuroprotection in rats with spinal cord injury

Introduction

Every-other-day fasting (EODF) is a classical intermittent fasting (IF) mode with neuroprotective effects that promotes motor function recovery after spinal cord injury (SCI) in rats. However, its dynamic effects on the gut microbiota and spinal cord transcriptome remain unknown.

Methods

In this study, 16S rRNA sequencing and RNA-seq analysis were used to investigate the effects of ad libitum (AL) and EODF dietary modes on the structural characteristics of rat gut microbiota in rats and the spinal cord transcriptome at various time points after SCI induction.

Results

Our results showed that both dietary modes affected the bacterial community composition in SCI rats, with EODF treatment inducing and suppressing dynamic changes in the abundances of potentially anti-inflammatory and pro-inflammatory bacteria. Furthermore, the differentially expressed genes (DEGs) enriched after EODF intervention in SCI rats were associated with various biological events, including immune inflammatory response, cell differentiation, protein modification, neural growth, and apoptosis. In particular, significant spatiotemporal differences were apparent in the DEGs associated with neuroprotection between the EODF and AL interventions. These DGEs were mainly focused on days 1, 3, and 7 after SCI. The relative abundance of certain genera was significantly correlated with DEGs associated with neuroprotective effects in the EODF-SCI group.

Discussion

Our results showed that EODF treatment may exert neuroprotective effects by modulating the transcriptome expression profile following SCI in rats. Furthermore, gut microbiota may be partially involved in mediating these effects.

Automation of training and testing motor and related tasks in pre-clinical behavioural and rehabilitative neuroscience

Testing and training animals in motor and related tasks is a cornerstone of pre-clinical behavioural and rehabilitative neuroscience. Yet manually testing and training animals in these tasks is time consuming and analyses are often subjective. Consequently, there have been many recent advances in automating both the administration and analyses of animal behavioural training and testing. This review is an in-depth appraisal of the history of, and recent developments in, the automation of animal behavioural assays used in neuroscience. We describe the use of common locomotor and non-locomotor tasks used for motor training and testing before and after nervous system injury. This includes a discussion of how these tasks help us to understand the underlying mechanisms of neurological repair and the utility of some tasks for the delivery of rehabilitative training to enhance recovery. We propose two general approaches to automation: automating the physical administration of behavioural tasks (i.e., devices used to facilitate task training, rehabilitative training, and motor testing) and leveraging the use of machine learning in behaviour analysis to generate large volumes of unbiased and comprehensive data. The advantages and disadvantages of automating various motor tasks as well as the limitations of machine learning analyses are examined. In closing, we provide a critical appraisal of the current state of automation in animal behavioural neuroscience and a prospective on some of the advances in machine learning we believe will dramatically enhance the usefulness of these approaches for behavioural neuroscientists.

Nerve injury and repair in a ketogenic milieu: A systematic review of traumatic injuries to the spinal cord and peripheral nervous tissue

Dietary interventions such as intermittent fasting and the ketogenic diet have demonstrated neuroprotective effects in various models of neurological insult. However, there has been a lack of evaluation of these interventions from a surgical perspective despite their potential to augment reparative processes that occur following nerve injury. Thus, we sought to analyze the effects of these dietary regimens on nerve regeneration and repair by critical appraisal of the literature. Following PRISMA guidelines, a systematic review was performed to identify studies published between 1950 and 2020 that examined the impact of either the ketogenic diet or intermittent fasting on traumatic injuries to the spinal cord or peripheral nerves. Study characteristics and outcomes were analyzed for each included article. A total of 1,890 articles were reviewed, of which 11 studies met inclusion criteria. Each of these articles was then assessed based on a variety of qualitative parameters, including type of injury, diet composition, timing, duration, and outcome. In total, seven articles examined the ketogenic diet, while four examined intermittent fasting. Only three studies examined peripheral nerves. Neuroprotective effects manifested as either improved histological or functional benefits in most of the included studies. Overall, we conclude that intermittent fasting and the ketogenic diet may promote neuroprotection and facilitate the regeneration and repair of nerve fibers following injury; however, lack of consistency between the studies in terms of animal models, diet compositions, and timing of dietary interventions preclude synthesis of their outcomes as a whole.

The Effects of a Ketogenic Diet on Sensorimotor Function in a Thoracolumbar Mouse Spinal Cord Injury Model

Spinal cord injury and peripheral nerve injuries are traumatic events that greatly impact quality of life. One factor that is being explored throughout patient care is the idea of diet and the role it has on patient outcomes. But the effects of diet following neurotrauma need to be carefully explored in animal models to ensure that they have beneficial effects. The ketogenic diet provides sufficient daily caloric requirements while being potentially neuroprotective and analgesic. In this study, animals were fed a high-fat, low-carbohydrate diet that led to a high concentration of blood ketone that was sustained for as long as the animals were on the diet. Mice fed a ketogenic diet had significantly lower levels of tyrosine and tryptophan, but the levels of other monoamines within the spinal cord remained similar to those of control mice. Mice were fed a standard or ketogenic diet for 7 d before and 28 d following the injury. Our results show that mice hemisected over the T10–T11 vertebrae showed no beneficial effects of being on a ketogenic diet over a 28 d recovery period. Similarly, ligation of the common peroneal and tibial nerve showed no differences between mice fed normal or ketogenic diets. Tests included von Frey, open field, and ladder-rung crossing. We add to existing literature showing protective effects of the ketogenic diet in forelimb injuries by focusing on neurotrauma in the hindlimbs. The results suggest that ketogenic diets need to be assessed based on the type and location of neurotrauma.

Improved Functional Recovery in Rat Spinal Cord Injury Induced by a Drug Combination Administered with an Implantable Polymeric Delivery System

Spinal cord injury (SCI) is an incurable condition, in which a cascade of cellular and molecular events triggered by inflammation and excitotoxicity impairs endogenous regeneration, namely remyelination and axonal outgrowth. We designed a treatment solution based on an implantable biomaterial (electrospun poly (l-lactic acid) [PLLA]) loaded with ibuprofen and triiodothyronine (T3) to counteract inflammation, thus improving endogenous regeneration. In vivo efficacy was tested by implanting the drug-loaded PLLA in the rat model of T8 contusion SCI. We observed the expected recovery of locomotion beginning on day 7. In PLLA-implanted rats (i.e., controls), the recovery stabilized at 21 days post-lesion (DPL), after which no further improvement was observed. On the contrary, in PLLA + ibuprofen (Ibu) + T3 (PLLA-Ibu-T3) rats a further recovery and a significant treatment effect were observed, also confirmed by the gait analysis on 49 DPL. Glutamate release at 24 h and 8 DPL was reduced in PLLA-Ibu-T3- compared to PLLA-implanted rats, such as the estimated lesion volume at 60 DPL. The myelin- and 200-neurofilament-positive area fraction was higher in PLLA-Ibu-T3-implanted rats, where the percentage of astrocytes was significantly reduced. The implant of a PLLA electrospun scaffold loaded with Ibu and T3 significantly improves the endogenous regeneration, leading to an improvement of functional locomotion outcome in the SCI.

Skilled reaching deterioration contralateral to cervical hemicontusion in rats is reversed by pregabalin treatment conditional upon its early administration

Introduction

Gabapentinoids are first-line treatments for painful traumatic and nontraumatic central nervous system disorders. Evidence from a large human study suggests that early use of gabapentinoids after spinal cord injury improves motor scores. The underlying mechanism is unknown.

Objectives

We sought to examine the effects of early pregabalin (PGB, a gabapentinoid) treatment on performance in a fine motor task (skilled reaching) after cervical hemicontusion. We also asked whether early PGB administration affected PGB responsiveness later on.

Methods

Rats received C4/5 cervical hemicontusions. Injury severities ranged from 80 to 150 kdyn. We monitored evidence of skin irritation (peri-incisional and elsewhere) and quantified food pellet retrieval using the Montoya staircase test. Behaviours were assessed in rats receiving early (for 3 weeks from injury induction) and/or late (resuming or beginning at week 8) PGB treatment in animals with 150-kdyn injuries.

Results

Contralateral skilled reaching waned in control animals with 150-kdyn injuries. This was prevented in animals, which received early PGB as long as treatment continued. Deterioration of skilled reaching was reversed by later (week 8) PGB only in animals that had received early treatment. Ipsilateral reaching impairment was not improved by PGB. Relief of skin irritation verified early PGB efficacy.

Conclusion

Hemicontusive spinal cord injury produces a contralateral motor phenotype evocative of on-going neuropathic pain. Early PGB preserves sensitivity to subsequent PGB treatment, indicating that motor function is impaired by neuropathic pain and can be improved indirectly by early PGB administration. Direct effects of PGB on motor circuitry cannot be excluded but are not supported by our data.

Spinal cord injury pharmacotherapy: Current research & development and competitive commercial landscape as of 2015

CONTEXT

Current treatment of spinal cord injury (SCI) focuses on cord stabilization to prevent further injury, rehabilitation, management of non-motor symptoms, and prevention of complications. Currently, no approved treatments are available, and limited treatment options exist for symptoms and complications associated with chronic SCI. This review describes the pharmacotherapy landscape in SCI from both commercial and research and development (R&D) standpoints through March 2015.

METHODS

Information about specific compounds has been obtained through drug pipeline monographs in the Pharmaprojects® (Citeline, Inc., New York, New York, USA) drug database (current as of a search on May 30, 2014), websites of individual companies with compounds in development for SCI (current as of March 24, 2015), and a literature search of published R&D studies to validate the Pharmaprojects® source for selected compounds (current as of March 24, 2015).

RESULTS

Types of studies conducted and outcomes measured in earlier phases of development are described for compounds in clinical development Currently four primary mechanisms are under investigation and may yield promising therapeutic targets: 1) neuronal regeneration; 2) neuroprotection (including anti-inflammation); 3) axonal reconnection; and 4) neuromodulation and signal enhancement. Many other compounds are no longer under investigation for SCI are mentioned; however, in most cases, the reason for terminating their development is not clear.

CONCLUSION

There is urgent need to develop disease-modifying therapy for SCI, yet the commercial landscape remains small and highly fragmented with a paucity of novel late-stage compounds in R&D.

Ketogenic diet delays spinal fusion and decreases bone mass in posterolateral lumbar spinal fusion: an in vivo rat model

BACKGROUND

Ketogenic diet (KD), a low-carbohydrate-and-high-fat diet, causes a metabolic state of ketogenesis and has been used to treat drug-resistance epilepsy. Our recent studies showed KD neuroprotective after spinal cord injury and causing bone loss. Effects of KD on spinal fusion were still unknown. This study was aimed to evaluate effects of KD on spinal fusion in rats.

METHODS

Thirty-two Sprague-Dawley rats were randomly divided into KD and standard diet (SD) groups. The KD group was fed with food of 1:4 carbohydrates to fat. All rats were subjected to L4/5 posterolateral lumbar spinal fusion. The blood ketone, and serum calcium, phosphorus, and insulin-like growth factor-1 (IGF-1) were measured, as well as the fusion rates, bone mass (BV), and bone mineral contents (BMC) of fusion sites were estimated at 4 and 8 weeks.

RESULTS

There was no significant difference in serum calcium or phosphorus levels between groups at 4 or 8 weeks. However, there was a significant increase of blood ketone (1.02 mmol/L vs 0.38 mmol/L at 4 weeks; 0.83 mmol/L vs 0.32 mmol/L, at 8 weeks) and decrease of serum IGF-1 (339.4 ng/mL vs 630.6 ng/mL at 4 weeks; 418.8 ng/mL vs 628.6 ng/mL, at 8 weeks) in the KD group compared with the SD group. The spinal fusion occurred less in the KD group (1/16 vs 6/16 at 4 weeks; 7/16 vs 10/16, at 8 weeks), particularly at 4 weeks after surgery. The BV and BMC were lower in the KD group than that in the SD group at 4 weeks, but not different between groups at 8 weeks.

CONCLUSIONS

This study demonstrated that KD delayed spinal fusion and decreased bone mass in posterolateral lumbar spinal fusion in rats.

The effects of paranodal myelin damage on action potential depend on axonal structure

Biophysical computational models of axons provide an important tool for quantifying the effects of injury and disease on signal conduction characteristics. Several studies have used generic models to study the average behavior of healthy and injured axons; however, few studies have included the effects of normal structural variation on the simulated axon's response to injury. The effects of variations in physiological characteristics on axonal function were mapped by altering the structure of the nodal, paranodal, and juxtaparanodal regions across reported values in three different caliber axons (1, 2, and 5.7 μm). Myelin detachment and retraction were simulated to quantify the effects of each injury mechanism on signal conduction. Conduction velocity was most affected by axonal fiber diameter (89%), while membrane potential amplitude was most affected by nodal length (86%) in healthy axons. Postinjury axonal functionality was most affected by myelin detachment in the paranodal and juxtaparanodal regions when retraction and detachment were modeled simultaneously. The efficacy of simulated potassium channel blockers on restoring membrane potential and velocity varied with axonal caliber and injury type. The structural characteristics of axons affect their functional response to myelin retraction and detachment and their subsequent response to potassium channel blocker treatment.

Combining neuroprotective agents: effect of riluzole and magnesium in a rat model of thoracic spinal cord injury

BACKGROUND CONTEXT

Damage to the spinal cord can result in irreversible impairments or complete loss of motor, sensory, and autonomic functions. Riluzole and magnesium have been widely investigated as neuroprotective agents in animal models of spinal cord injury. As these drugs protect the injured spinal cord through different mechanisms, we aimed to investigate if their neuroprotective efficacy could be cumulative.

PURPOSE

This study aimed to investigate the neuroprotective efficacy of combined administration of riluzole and magnesium chloride in a contusive model of thoracic spinal cord injury.

STUDY DESIGN

An in vivo experiment was set using female Wistar Han rats that underwent a thoracic spinal cord contusion (T8) using a weight drop method. An hour after injury, animals were randomly distributed to receive (1) saline, (2) riluzole (2.50 mg/kg), (3) magnesium chloride (24.18 mg/kg) in a polyethylene glycol formulation, or (4) a combined treatment (riluzole and magnesium). Subsequent treatments were given in four intraperitoneal injections (spaced 12 hours apart).

METHODS

The Basso, Beattie, and Bresnahan locomotor rating scale, an activity box test, and a swimming test were used to evaluate behavioral recovery over a 4-week period. Histologic analysis of the spinal cords was performed to measure the extent and volume of the lesion, axonal preservation, serotonergic and glutamatergic fiber sparing, motor neuron survival, and inflammation.

RESULTS

Our results show that only the riluzole treatment significantly improved behavioral recovery up to 4 weeks after injury when compared with saline controls (6.2±1.8), with animals achieving weight-supported stepping (9.1±1.2). Riluzole also promoted tissue sparing with significant differences achieved from 200 to 600 µm (caudally to the lesion epicenter), and reduced lesion volume, with animals presenting a significantly smaller lesion (3.23±0.26 mm(3)) when compared with the saline-treated group (4.74±0.80 mm(3)), representing a 32% decrease in lesion volume. Riluzole treatment induced significant axonal preservation, as well as serotonergic fiber sparing, caudally to the injury epicenter.

CONCLUSIONS

Our results suggest that the combined treatment, although simultaneously targeting two excitotoxic-related mechanisms, did not further improve behavioral and histologic outcome when compared with riluzole given alone.

Sciatic nerve regeneration in rats subjected to ketogenic diet

OBJECTIVES

Ketogenic diet (KD) is a high-fat-content diet with insufficiency of carbohydrates that induces ketogenesis. Besides its anticonvulsant properties, many studies have shown its neuroprotective effect in central nervous system, but its influence on peripheral nervous system has not been studied yet. We examined the influence of KD on regeneration of peripheral nerves in adult rats.

METHODS

Fifty one rats were divided into three experimental (n = 15) and one control (n = 6) groups. Right sciatic nerve was crushed and animals were kept on standard (ST group) or ketogenic diet, the latter was introduced 3 weeks before (KDB group) or on the day of surgery (KDA group). Functional (CatWalk) tests were performed once a week, and morphometric (fiber density, axon diameter, and myelin thickness) analysis of the nerves was made after 6 weeks. Body weight and blood ketone bodies level were estimated at the beginning and the end of experiment.

RESULTS

Functional analysis showed no differences between groups. Morphometric evaluation showed most similarities to the healthy (uncrushed) nerves in KDB group. Nerves in ST group differed mostly from all other groups. Ketone bodies were elevated in both KD groups, while post-surgery animals' body weight was lower as compared to ST group.

DISCUSSION

Regeneration of sciatic nerves was improved in KD - preconditioned rats. These results suggest a neuroprotective effect of KD on peripheral nerves.