Spinal Cord-Gut-Immune Axis and its Implications Regarding Therapeutic Development for Spinal Cord Injury

No Beneficial Effects of the Alfasigma VSL#3 Probiotic Treatment After Cervical Spinal Cord Injury in Rats

Background

The bidirectional communication between the gastrointestinal tract and the central nervous system appears to be linked to the intestinal microbiome. Research has shown that spinal cord injury (SCI) can disrupt the gut microbiome, leading to gut dysbiosis. These changes can have several negative impacts, such as exacerbated systemic inflammation and susceptibility to infection. Probiotics administered to mice with SCI have been shown to ameliorate gut dysbiosis, confer neuroprotection, and improve locomotor recovery. However, probiotics have also produced conflicting results, making potential claims regarding the application of probiotics as a therapeutic supplement ambiguous.

Objectives

This study aimed to investigate the effects of a commercially available probiotic on recovery in a rat model of cervical SCI.

Methods

Rats with cervical contusion SCI received probiotics over 7 days immediately after injury, and their recovery in motor, sensory, and cognitive tasks was compared to that of untreated animals.

Results

Compared with a control group, the oral administration of probiotics influenced neither motor nor cognitive outcomes. We did observe a significantly different lesion size between the two groups, where the probiotic group had less spared tissue, despite a lack of differences in functional outcomes. In addition, probiotic treatment delayed gut microbiome composition recovery to baseline levels for up to 35 days postinjury (DPI). We found significantly higher proportions of Lactobacillus in the fecal matter of SCI-vehicle rats at 35 DPI, whereas Streptococcus was higher in SCI-probiotics fecal matter at 14 and 35 DPI, and Bacillales was higher in the latter group at 35 DPI.

Conclusion

Taken together, our results do not support the application of the utilized probiotic cocktail as a dietary supplement for the treatment of cervical SCI-induced gut dysbiosis and secondary complications.

Overview of the Efficacy of Using Probiotics for Neurosurgical and Potential Neurosurgical Patients

This review delves into the emerging field of the gut microbiota-brain axis, emphasizing its bidirectional communication and implications for neurological health, particularly in trauma and neurosurgery. While disruptions in this axis can lead to dysbiosis and hinder neurological recovery, recent studies have highlighted the therapeutic potential of interventions like probiotics in targeting this axis. This review aims to focus on the efficacy of probiotic supplementation to support the gut microbiota-brain axis in trauma, neurosurgery, or pain based on the current clinical trials to assess the complex interplays among probiotics, the gut microbiota, and the central nervous system (CNS). This comprehensive literature review identified 10 relevant publications on probiotic interventions for various neurosurgical conditions across multiple countries. These studies demonstrated diverse outcomes, with significant improvements observed in gastrointestinal mobility, inflammatory responses, and infection rates, particularly in post-traumatic brain injury and spinal surgery. Probiotics also showed promise in mitigating antibiotic-associated diarrhea and modulating inflammatory cytokines. Despite the promising findings, the complex interplays among probiotics, the gut microbiota, and the central nervous system (CNS) call for cautious interpretation. Conflicting outcomes emphasize the need for better-designed trials to understand strain-specific and disease-specific effects accurately. In conclusion, probiotics offer a promising adjuvant therapy for neurosurgical patients, traumatic brain injuries, and post-spinal surgery. However, further well-designed randomized controlled trials are essential to elucidate the intricate relationship between microbiome-modulating interventions and the CNS via the gut microbiota-brain axis.

Lack of gut microbiome recovery with spinal cord injury rehabilitation

Spinal cord injury (SCI) is a devastating event that significantly changes daily function and quality of life and is linked to bowel and bladder dysfunction and frequent antibiotic treatment. We aimed to study the composition of the gut microbiome in individuals with SCI during the initial sub-acute rehabilitation process and during the chronic phase of the injury. This study included 100 fecal samples from 63 participants (Median age 40 years, 94% males): 13 cases with SCI in the sub-acute phase with 50 longitudinal samples, 18 cases with chronic SCI, and 32 age and gender-matched controls. We show, using complementary methods, that the time from the injury was a dominant factor linked with gut microbiome composition. Surprisingly, we demonstrated a lack of gut microbial recovery during rehabilitation during the sub-acute phase, with further deviation from the non-SCI control group in the chronic ambulatory SCI group. To generalize the results, we were able to show significant similarity of the signal when comparing to a previous cohort with SCI, to subjects from the American Gut Project who reported low physical activity, and to subjects from another population-based cohort who reported less normal stool consistency. Restoration of the microbiome composition may be another desirable measure for SCI recovery in the future, but further research is needed to test whether such restoration is associated with improved neurological outcomes and quality of life.

The Intestinal Microbiome after Traumatic Injury

The intestinal microbiome plays a critical role in host immune function and homeostasis. Patients suffering from-as well as models representing-multiple traumatic injuries, isolated organ system trauma, and various severities of traumatic injury have been studied as an area of interest in the dysregulation of immune function and systemic inflammation which occur after trauma. These studies also demonstrate changes in gut microbiome diversity and even microbial composition, with a transition to a pathobiome state. In addition, sex has been identified as a biological variable influencing alterations in the microbiome after trauma. Therapeutics such as fecal transplantation have been utilized to ameliorate not only these microbiome changes but may also play a role in recovery postinjury. This review summarizes the alterations in the gut microbiome that occur postinjury, either in isolated injury or multiple injuries, along with proposed mechanisms for these changes and future directions for the field.