A Preliminary Cohort Study Assessing Routine Blood Analyte Levels and Neurological Outcome after Spinal Cord Injury

Untargeted blood serum proteomics identifies novel proteins related to neurological recovery after human spinal cord injury

BACKGROUND

The discovery of new prognostic biomarkers following spinal cord injury (SCI) is a rapidly growing field that could help uncover the underlying pathological mechanisms of SCI and aid in the development of new therapies. To date, this search has largely focused on the initial days after the lesion. However, during the subacute stage of SCI (weeks to months after the injury), there remains potential for sensorimotor recovery, and numerous secondary events develop in various organs. Additionally, the confounding effects of early interventions after the injury are less likely to interfere with the results.

METHODS

In this study, we conducted an untargeted proteomics analysis to identify biomarkers of recovery in blood serum samples during the subacute phase of SCI patients, comparing those with strong recovery to those with no recovery between 30 and 120 days. We analyzed the fraction of serum that is depleted of the most abundant proteins to unmask proteins that would otherwise go undetected. Linear models were used to identify peptides and proteins related to neurological recovery and we validated changes in some of these proteins using Enzyme-linked Immunosorbent Assay (ELISA).

RESULTS

Our findings reveal that differences in subacute recovery after SCI (from 30 to 120 days) are associated with an enrichment in proteins involved in inflammation, coagulation, and lipid metabolism. Technical validation using commercial ELISAs further confirms that high levels of SERPINE1 and ARHGAP35 are associated with strong neurological recovery, while high levels of CD300a and DEFA1 are associated with a lack of recovery.

CONCLUSIONS

Our study identifies new candidates for biomarkers of neurological recovery and for novel therapeutic targets after SCI.

Immediate administration of hTERT-MSCs-IDO1-EVs reduces hypoalbuminemia after spinal cord injury

Spinal cord injury (SCI) presents challenging and unpredictable neurological recovery. During inflammatory conditions, the amount of serum albumin and nutrition consumption decreases. Currently, it is proposed to measure serum albumin and glucose content in human or animal subjects to predict the recovery rate and the efficiency of treatments following SCI. In this study, the effect of extra-cellular vesicles (EVs) from immortalized human adipose tissue-derived mesenchymal stem cells (hTERT-MSCs) equipped with the ectopic expression of the human indoleamine 2,3-dioxygenase-1 (IDO1) gene on serum albumin and glucose levels was investigated. After pre-clearing steps of 72-hr conditioned media, small EVs (sEVs) were isolated based on the ultra-filtration method. They were encapsulated with a chitosan-based hydrogel. Five experimental groups (female rats, N = 30, ~ 230 g) were considered, including SCI, sham, hydrogel, control green fluorescent protein (GFP)-EVs and IDO1-EVs. The 60.00 µL of hydrogel or hydrogels containing 100 µg sEVs from GFP or IDO1-EVs were locally injected immediately after SCI (laminectomy of the T10 vertebra and clip compression). After 8 weeks, non-fasting serum glucose and albumin levels were measured. The results indicated that the level of serum albumin in the animals received IDO1-EVs (3.52 ± 0.04) was increased in comparison with the SCI group (3.00 ± 0.94). Also, these animals indicated higher glucose levels in their serum (250.17 ± 69.61) in comparison with SCI ones (214 ± 45.34). Although these changes were not statistically significant, they could be considered as evidence for the beneficial effects of IDO1-EVs administration in the context of SCI to reduce hypoalbuminemia and improve energy consumption. More detailed experiments are required to confirm these results.

Proteomic Analyses of Autologous Chondrocyte Implantation Plasma Highlight Cartilage Acidic Protein 1 as a Candidate for Preclinical Screening

BACKGROUND

Stratification is required to ensure that only patients likely to benefit receive autologous chondrocyte implantation (ACI). It would be advantageous to identify biomarkers to predict ACI outcome that are measurable in blood, avoiding the need for an invasive synovial fluid harvest.

PURPOSE

To assess if proteomic analyses can be used to identify novel candidate blood biomarkers in individuals who respond well or poorly to ACI.

STUDY DESIGN

Controlled laboratory study.

METHODS

Isobaric tagging for relative and absolute quantitation (iTRAQ) mass spectrometry was used to assess the proteome in plasma pooled from ACI responders (mean Lysholm improvement after ACI, 33; n = 10) or nonresponders (mean, -13; n = 10), collected at the time of surgery for cartilage harvest (stage 1) or implantation of culture-expanded chondrocytes (stage 2). An alternative proteomic method, label-free quantitation liquid chromatography-tandem mass spectrometry, was used to analyze plasma samples (majority matched to iTRAQ) individually. Differentially abundant proteins (±2.0-fold) were analyzed from both proteomic data sets, and markers of interest identified via pooled iTRAQ were validated via immunoassay of individual samples.

RESULTS

Protein differences could be detected in the plasma preoperatively between ACI responders and nonresponders (16 proteins; ≥±2.0-fold change; P < .05) using iTRAQ proteomics. The most pronounced plasma proteome shift was evident in response to stage 1 surgery in ACI nonresponders, with 48 proteins being differentially abundant between the procedures. Label-free quantitation liquid chromatography-tandem mass spectrometry analysis of these same plasma samples (nonpooled) resulted in very few proteins being identified that were significantly differentially abundant. However, this work highlighted cartilage acidic protein 1 as being increased preoperatively in nonresponders as compared with responders.

CONCLUSIONS

This study is the first to use proteomic techniques to profile the plasma of individuals treated with ACI. Despite iTRAQ analysis of pooled plasmas indicating that there are differences in the plasma proteome between responders and nonresponders to ACI, these findings were not replicated when assessed using an alternative nonpooled technique. This study highlights some of the difficulties in profiling the plasma proteome in an attempt to identify novel biomarkers. Regardless, cartilage acidic protein 1 has been identified as a protein candidate, which is detectable in plasma and can predict outcome to ACI before treatment.

CLINICAL RELEVANCE

Candidate plasma protein biomarkers identified in this study have the potential to help determine which patients will be best suited to treatment with ACI.

Advances in monitoring for acute spinal cord injury: a narrative review of current literature

Spinal cord injury (SCI) is a devastating condition that affects about 17,000 individuals every year in the United States, with approximately 294,000 people living with the ramifications of the initial injury. After the initial primary injury, SCI has a secondary phase during which the spinal cord sustains further injury due to ischemia, excitotoxicity, immune-mediated damage, mitochondrial dysfunction, apoptosis, and oxidative stress. The multifaceted injury progression process requires a sophisticated injury-monitoring technique for an accurate assessment of SCI patients. In this narrative review, we discuss SCI monitoring modalities, including pressure probes and catheters, micro dialysis, electrophysiologic measures, biomarkers, and imaging studies. The optimal next-generation injury monitoring setup should include multiple modalities and should integrate the data to produce a final simplified assessment of the injury and determine markers of intervention to improve patient outcomes.

Investigation of the blood proteome in response to spinal cord injury in rodent models

Study design

Explanatory and mechanistic study.

Objectives

A better understanding of the ‘whole-body’ response following spinal cord injury (SCI) is needed to guide future research aimed at developing novel therapeutic interventions and identifying prognostic indicators for SCI. This study aimed to characterise the blood proteome following contusion or complete SCI compared to a sham injury in rat models.

Setting

United Kingdom.

Methods

Pooled blood samples from one and seven days after a contusion (serum; n = 5) or from 14 days and 112 days post-complete transection SCI (plasma; n = 8) and their sham-injured counterparts were subjected to independent iTRAQ nanoflow liquid chromatography tandem mass-spectrometry proteomic analyses. Pathway analyses of the proteins that were differentially abundant between SCI and their matched sham injured counterparts were completed to indicate biological pathways that may be changed in response to SCI.

Results

Eleven and 42 proteins were differentially abundant (≥±2.0 FC; p ≤ 0.05) between the contusion SCI and sham injured animals at 24 h and seven days post-injury, respectively. Seven and tweleve proteins were differentially abundant between complete and sham injured rats at 14 and 112 days post-injury, respectively. Acute-phase response signalling and Liver X Receptor/Retinoic X Receptor activation were identified as differentially regulated pathways in both models of SCI.

Conclusions

We have utilised longitudinal preclinical SCI models to provide an insight into the blood proteome changes that result following SCI and to highlight a number of biological pathways of interest for future studies.

Improving Diagnostic Workup Following Traumatic Spinal Cord Injury: Advances in Biomarkers

PURPOSE OF REVIEW

Traumatic spinal cord injury (SCI) is a life-changing event with drastic implications for patients due to sensorimotor impairment and autonomous dysfunction. Current clinical evaluations focus on the assessment of injury level and severity using standardized neurological examinations. However, they fail to predict individual trajectories of recovery, which highlights the need for the development of advanced diagnostics. This narrative review identifies recent advances in the search of clinically relevant biomarkers in the field of SCI.

RECENT FINDINGS

Advanced neuroimaging and molecular biomarkers sensitive to the disease processes initiated by the SCI have been identified. These biomarkers range from advanced neuroimaging techniques, neurophysiological readouts, and molecular biomarkers identifying the concentrations of several proteins in blood and CSF samples. Some of these biomarkers improve current prediction models based on clinical readouts. Validation with larger patient cohorts is warranted. Several biomarkers have been identified-ranging from imaging to molecular markers-that could serve as advanced diagnostic and hence supplement current clinical assessments.

Liver inflammation at the time of spinal cord injury enhances intraspinal pathology, liver injury, metabolic syndrome and locomotor deficits

The current high obesity rates mean that neurological injuries are increasingly sustained on a background of systemic pathology, including liver inflammation, which likely has a negative impact on outcomes. Because obesity involves complex pathology, the effect of hepatic inflammation alone on neurological recovery is unknown. Thus, here we used a gain-of-function model to test if liver inflammation worsens outcome from spinal cord injury (SCI) in rats. Results show liver inflammation concomitant with SCI exacerbated intraspinal pathology and impaired locomotor recovery. Hepatic inflammation also potentiated SCI-induced non-alcoholic steatohepatitis (NASH), endotoxemia and insulin resistance. Circulating and cerebrospinal levels of the liver-derived protein Fetuin-A were higher in SCI rats with liver inflammation, and, when microinjected into intact spinal cords, Fetuin-A caused macrophage activation and neuron loss. Thus, liver inflammation functions as a disease modifying factor to impair recovery from SCI, and Fetuin-A is a potential neuropathological mediator. Since SCI alone induces acute liver inflammation, the liver may be a novel clinical target for improving recovery from SCI.

The Comparative Effects of Mesenchymal Stem Cell Transplantation Therapy for Spinal Cord Injury in Humans and Animal Models: A Systematic Review and Meta-Analysis

Animal models have been used in preclinical research to examine potential new treatments for spinal cord injury (SCI), including mesenchymal stem cell (MSC) transplantation. MSC transplants have been studied in early human trials. Whether the animal models represent the human studies is unclear. This systematic review and meta-analysis has examined the effects of MSC transplants in human and animal studies. Following searches of PubMed, Clinical Trials and the Cochrane Library, published papers were screened, and data were extracted and analysed. MSC transplantation was associated with significantly improved motor and sensory function in humans, and significantly increased locomotor function in animals. However, there are discrepancies between the studies of human participants and animal models, including timing of MSC transplant post-injury and source of MSCs. Additionally, difficulty in the comparison of functional outcome measures across species limits the predictive nature of the animal research. These findings have been summarised, and recommendations for further research are discussed to better enable the translation of animal models to MSC-based human clinical therapy.

Routine Blood Chemistry Predicts Functional Recovery After Traumatic Spinal Cord Injury: A Post Hoc Analysis

BACKGROUND

Spinal cord injury (SCI) leads to various degrees of lifelong functional deficits. Most individuals with incomplete SCI experience a certain degree of functional recovery, especially within the first-year postinjury. However, this is difficult to predict, and surrogate biomarkers are urgently needed.

OBJECTIVE

We aimed to (1) determine if routine blood chemistry parameters are related to neurological recovery after SCI, (2) evaluate if such parameters could predict functional recovery, and (3) establish cutoff values that could inform clinical decision-making.

METHODS

We performed a post hoc analysis of routine blood chemistry parameters in patients with traumatic SCI (n = 676). Blood samples were collected between 24 and 72 hours as well as at 1, 2, 4, 8, and 52 weeks postinjury. Linear mixed models, regression analysis, and unbiased recursive partitioning (URP) of blood chemistry data were used to relate to and predict walking recovery 1 year postinjury.

RESULTS

The temporal profile of platelet counts and serum levels of albumin, alkaline phosphatase, and creatinine differentiated patients who recovered walking from those who remained wheelchair bound. The 4 blood chemistry parameters from the sample collection 8 weeks postinjury predicted functional recovery observed 1 year after incomplete SCI. Finally, URP defined a cutoff for serum albumin at 3.7 g/dL, which in combination with baseline injury severity differentiates individuals who regain ambulation from those not able to walk. Specifically, about 80% of those with albumin >3.7 g/dL recovered walking.

CONCLUSIONS

Routine blood chemistry data from the postacute phase, together with baseline injury severity, predict functional outcome after incomplete SCI.

Routinely Measured Hematological Markers Can Help to Predict American Spinal Injury Association Impairment Scale Scores after Spinal Cord Injury

Neurological outcomes following spinal cord injury (SCI) are currently difficult to predict. While the initial American Spinal Injury Association Impairment Scale (AIS) grade can give an estimate of outcome, the high remaining degree of uncertainty has stoked recent interest in biomarkers for SCI. This study aimed to assess the prognostic value of routinely measured blood biomarkers by developing prognostic models of AIS scores at discharge and 12 months post-injury. Routine blood and clinical data were collected from SCI patients (n = 417), and blood measures that had been assessed in less than 50% of patients were excluded. Outcome neurology was obtained from AIS and Spinal Cord Independence Measure III (SCIM-III) scores at discharge and 12 months post-injury, with motor (AIS) and sensory (AIS, touch and prick) abilities being assessed individually. Linear regression models with and without elastic net penalization were created for all outcome measures. Blood measures associated with liver function, such as alanine transaminase, were found to add value to predictions of SCIM-III at discharge and 12 months post-injury. Further, components of a total blood count, including hemoglobin, were found to add value to predictions of AIS motor and sensory scores at discharge and 12 months post-injury. These findings corroborate the results of our previous preliminary study and thus provide further evidence that routine blood measures can add prognostic value in SCI and that markers of liver function are of particular interest.

Hepatic dysfunction after spinal cord injury: A vicious cycle of central and peripheral pathology?

The liver is essential for numerous physiological processes, including filtering blood from the intestines, metabolizing fats, proteins, carbohydrates and drugs, and regulating iron storage and release. The liver is also an important immune organ and plays a critical role in response to infection and injury throughout the body. Liver functions are regulated by autonomic parasympathetic innervation from the brainstem and sympathetic innervation from the thoracic spinal cord. Thus, spinal cord injury (SCI) at or above thoracic levels disrupts major regulatory mechanisms for hepatic functions. Work in rodents and humans shows that SCI induces liver pathology, including hepatic inflammation and fat accumulation characteristic of a serious form of non-alcoholic fatty liver disease (NAFLD) called non-alcoholic steatohepatitis (NASH). This hepatic pathology is associated with and likely contributes to indices of metabolic dysfunction often noted in SCI individuals, such as insulin resistance and hyperlipidemia. These occur at greater rates in the SCI population and can negatively impact health and quality of life. In this review, we will: 1) Discuss acute and chronic changes in human and rodent liver pathology and function after SCI; 2) Describe how these hepatic changes affect systemic inflammation, iron regulation and metabolic dysfunction after SCI; 3) Describe how disruption of the hepatic autonomic nervous system may be a key culprit in post-injury chronic liver pathology; and 4) Preview ongoing and future research that aims to elucidate mechanisms driving liver and metabolic dysfunction after SCI.