Combinatorial strategies for cell transplantation in traumatic spinal cord injury.

Spinal cord injury (SCI) substantially reduces the quality of life of affected individuals. Recovery of function is therefore a primary concern of the patient population and a primary goal for therapeutic interventions. Currently, even with growing numbers of clinical trials, there are still no effective treatments that can improve neurological outcomes after SCI. A large body of work has demonstrated that transplantation of neural stem/progenitor cells (NSPCs) can promote regeneration of the injured spinal cord by providing new neurons that can integrate into injured host neural circuitry. Despite these promising findings, the degree of functional recovery observed after NSPC transplantation remains modest. It is evident that treatment of such a complex injury cannot be addressed with a single therapeutic approach. In this mini-review, we discuss combinatorial strategies that can be used along with NSPC transplantation to promote spinal cord regeneration. We begin by introducing bioengineering and neuromodulatory approaches, and highlight promising work using these strategies in integration with NSPCs transplantation. The future of NSPC transplantation will likely include a multi-factorial approach, combining stem cells with biomaterials and/or neuromodulation as a promising treatment for SCI.

Clickable Granular Hydrogel Scaffolds for Delivery of Neural Progenitor Cells to Sites of Spinal Cord Injury.

Spinal cord injury (SCI) is a serious condition with limited treatment options. Neural progenitor cell (NPC) transplantation is a promising treatment option, and the identification of novel biomaterial scaffolds that support NPC engraftment and therapeutic activity is a top research priority. The objective of this study is to evaluate in situ assembled poly (ethylene glycol) (PEG)-based granular hydrogels for NPC delivery in a murine model of SCI. Microgel precursors are synthesized by using thiol-norbornene click chemistry to react four-armed PEG-amide-norbornene with enzymatically degradable and cell adhesive peptides. Unreacted norbornene groups are utilized for in situ assembly into scaffolds using a PEG-di-tetrazine linker. The granular hydrogel scaffolds exhibit good biocompatibility and do not adversely affect the inflammatory response after SCI. Moreover, when used to deliver NPCs, the granular hydrogel scaffolds supported NPC engraftment, do not adversely affect the immune response to the NPC grafts, and successfully support graft differentiation toward neuronal or astrocytic lineages as well as axonal extension into the host tissue. Collectively, these data establish PEG-based granular hydrogel scaffolds as a suitable biomaterial platform for NPC delivery and justify further testing, particularly in the context of more severe SCI.

Chemogenetic Attenuation of Acute Nociceptive Signaling Enhances Functional Outcomes Following Spinal Cord Injury.

Identifying novel therapeutic approaches to promote recovery of neurological functions following spinal cord injury (SCI) remains a great unmet need. Nociceptive signaling in the acute phase of SCI has been shown to inhibit recovery of locomotor function and promote the development of chronic neuropathic pain. We therefore hypothesized that inhibition of nociceptive signaling in the acute phase of SCI might improve long-term functional outcomes in the chronic phase of injury. To test this hypothesis, we took advantage of a selective strategy utilizing AAV6 to deliver inhibitory (hM4Di) Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) to nociceptors of the L4-L6 dorsal root ganglia to evaluate the effects of transient nociceptor silencing on long-term sensory and motor functional outcomes in a rat thoracic contusion SCI model. Following hM4Di-mediated nociceptor inhibition from 0-14 days post-SCI, we conducted behavioral assessments until 70 days post-SCI, then performed histological assessments of lesion severity and axon plasticity. Our results show highly selective expression of hM4Di within small diameter nociceptors including calcitonin gene-related peptide (CGRP)+ and IB4-binding neurons. Expression of hM4Di in less than 25% of nociceptors was sufficient to increase hindlimb thermal withdrawal latency in naïve rats. Compared with subjects who received AAV-yellow fluorescent protein (YFP; control), subjects who received AAV-hM4Di exhibited attenuated thermal hyperalgesia, greater coordination, and improved hindlimb locomotor function. However, treatment did not impact the development of cold allodynia or mechanical hyperalgesia. Histological assessments of spinal cord tissue suggested trends toward reduced lesion volume, increased neuronal sparing and increased CGRP+ axon sprouting in hM4Di-treated animals. Together, these findings suggest that nociceptor silencing early after SCI may promote beneficial plasticity in the acute phase of injury that can impact long-term functional outcomes, and support previous work highlighting primary nociceptors as possible therapeutic targets for pain management after SCI.

Differences in Anatomical Outcomes Between Early Chronic and Far Chronic Time-Points After Transplantation of Spinal Cord Neural Progenitor Cells in Mice.

Spinal cord injury (SCI) affects millions of people worldwide. Neural progenitor cell (NPC) transplantation is a promising treatment for regenerating lost spinal cord tissue and restoring neurological function after SCI. We conducted a literature search and found that less than a quarter of experimental rodent cell and tissue transplantation studies have investigated anatomical outcomes at longer than 4 months post-transplantation. This is a critical topic to investigate, given that stem and progenitor cell therapies would need to remain in place throughout the lifetime of an individual. We sought to determine how commonly assessed anatomical outcomes evolve between early and far chronic time-points post-NPC transplantation. At either 8 weeks or 26 weeks following transplantation of NPCs into sites of cervical SCI, we evaluated graft neuronal density, astroglial cell density, graft axon outgrowth, and regeneration of host axon populations into grafts in male and female mice. We found that graft neuronal density does not change over time, but the numbers of graft-associated astrocytes and glial fibrillary acidic protein intensity is significantly increased in the far chronic phase compared with the early chronic time-point. In addition, graft axon outgrowth was significantly decreased at 26 weeks post-transplantation compared with 8 weeks post-transplantation. In contrast, corticospinal axon regeneration into grafts was not diminished over time, but rather increased significantly from early to far chronic periods. Interestingly, we found that graft neuronal density is significantly influenced by sex of the host animal, suggesting that sex-dependent processes may shape graft composition over time. Collectively, these results demonstrate that NPC transplants are dynamic and that commonly assessed outcome measures associated with graft efficacy evolve over the weeks to months post-transplantation into the spinal cord.

The Combined Effect of Delirium and Falls on Length of Stay and Discharge.

INTRODUCTION: Delirium or a fall are associated with many negative outcomes including increased length of stay (LOS) and discharge to a facility; however, this relationship is incompletely understood. METHODS: A cross-sectional study of all hospitalizations in a large, tertiary care hospital evaluated the effect of delirium and a fall on the outcomes of LOS and risk of being discharged to a facility. RESULTS: The study included 29,655 hospital admissions. A total of 3,707 (12.5%) patients screened positive for delirium and 286 (0.96%) had a reported fall. After adjustment for covariates, relative to patients without delirium or a fall, patients with delirium only had a 1.64-fold longer LOS; patients with fall only had a 1.96-fold longer LOS; and patients who had delirium and fall had a 2.84-fold longer LOS. The adjusted odds of discharge to a facility, relative to those without delirium or a fall, was 8.98 times higher in those with delirium and a fall. CONCLUSIONS: Delirium and falls influence LOS and likelihood of being discharged to a facility. The joint impact of falls and delirium on LOS and facility discharge was more than additive. Hospitals should consider the integrated management of delirium and falls.

Developmental stage of transplanted neural progenitor cells influences anatomical and functional outcomes after spinal cord injury in mice.

Neural progenitor cell (NPC) transplantation is a promising therapeutic strategy for replacing lost neurons following spinal cord injury (SCI). However, how graft cellular composition influences regeneration and synaptogenesis of host axon populations, or recovery of motor and sensory functions after SCI, is poorly understood. We transplanted developmentally-restricted spinal cord NPCs, isolated from E11.5-E13.5 mouse embryos, into sites of adult mouse SCI and analyzed graft axon outgrowth, cellular composition, host axon regeneration, and behavior. Earlier-stage grafts exhibited greater axon outgrowth, enrichment for ventral spinal cord interneurons and Group-Z spinal interneurons, and enhanced host 5-HT+ axon regeneration. Later-stage grafts were enriched for late-born dorsal horn interneuronal subtypes and Group-N spinal interneurons, supported more extensive host CGRP+ axon ingrowth, and exacerbated thermal hypersensitivity. Locomotor function was not affected by any type of NPC graft. These findings showcase the role of spinal cord graft cellular composition in determining anatomical and functional outcomes following SCI.

Tempo and Mode of Genome Structure Evolution in Insects.

The division of the genome into discrete chromosomes is a fundamental characteristic of eukaryotic life. Insect taxonomists' early adoption of cytogenetics has led to an incredible amount of data describing genome structure across insects. In this article, we synthesize data from thousands of species and use biologically realistic models to infer the tempo and mode of chromosome evolution among insect orders. Our results show that orders vary dramatically in the overall rate of chromosome number evolution (a proxy of genome structural stability) and the pattern of evolution (e.g., the balance between fusions and fissions). These findings have important implications for our understanding of likely modes of speciation and offer insight into the most informative clades for future genome sequencing.

The Emerging Role of Biological Sex in Cell Therapy for Spinal Cord Injury.

Neural progenitor cell (NPC) transplantation is a promising potential therapy for replacing spinal cord neurons and glial cells following spinal cord injury (SCI). Despite the rapid advancement of NPC transplantation to SCI clinical trials, we still lack understanding of fundamental biology underlying how NPC grafts interact with the injured host nervous system. Our recent study demonstrated a potent effect of biological sex mismatch between donor and host on graft immune rejection. Here we discuss the implications of this study in the context of clinical trials for SCI, and important topics for future research in SCI cell transplantation.

The Association between Delirium and In-Hospital Falls: A Cross-Sectional Analysis of a Delirium Screening Program.

Methods: A cross-sectional study using delirium screening and falls reports was used to measure the association between delirium and falls. All inpatient data from August, 2018, to January, 2020, at a large academic medical center were analyzed. A multivariable logistic regression of 29,655 hospital admissions was used to understand the association between in-hospital delirium and falls. Results: Analysis revealed a delirium rate of 12.5% (n = 3,707) of all admissions and 286 (0.9%) admissions with falls; of the falls studied, 37.6% of these patients screened positive for delirium during their admission. Relative to those who screened negative for delirium, admissions that screened positive for delirium had a 2.81 increased odds of falling. Conclusions: Delirium and falls are related. This strong association should motivate health systems to look closely at both problems. Falls and delirium can both have immense impacts on the patient and the health system. The powerful association between them provides a window to reduce these additional patient harms. More specifically, a modern delirium screening tool should be used as part of routine risk assessment focused on reducing in-hospital falls.

Understanding the association between admission source and in-hospital delirium: A cross-sectional study.

Patients admitted via interhospital transfer (IHT) experience increased risk-adjusted mortality, adverse events, length of stay, and discharge to facility; however, the etiology is not well understood. We hypothesize that IHTs are more likely to experience in-hospital delirium as compared with admissions to the hospital via the emergency department (ED) and clinic. This is a cross-sectional study of all adult admissions to medical, surgical, neurological, and obstetrics and gynecology services at an academic medical center who were screened for delirium between August 2018 and January 2020. Unit of analysis was admission source (IHT vs ED vs clinic) as the independent variable and the primary outcome was in-hospital delirium, assessed with initial brief confusion assessment method (bCAM) screening. 30,100 hospitalizations were included in this study with 3925 admissions (13.0%) screening positive for delirium at the initial bCAM assessment. The prevalence of delirium was much higher in IHTs at 22.3% (1334/5971) when compared with clinic at 5.8% (244/4214) and ED at 11.8% (2347/19,915) admissions. Multivariable logistic regression adjusting for demographics and comorbidities showed that IHT admissions had higher odds (OR 1.91, 95% CI 1.74 to 2.10) and clinic admissions had lower odds (OR 0.56, 95% CI 0.48 to 0.64) of in-hospital delirium compared with ED admissions. Increased odds of delirium in IHT admissions may contribute to the observed increased length of stay, discharge to facility, and mortality. These results emphasize the importance of routine screening and possible intervention prior to patient transfer.

Fighting for recovery on multiple fronts: The past, present, and future of clinical trials for spinal cord injury.

Through many decades of preclinical research, great progress has been achieved in understanding the complex nature of spinal cord injury (SCI). Preclinical research efforts have guided and shaped clinical trials, which are growing in number by the year. Currently, 1,149 clinical trials focused on improving outcomes after SCI are registered in the U.S. National Library of Medicine at ClinicalTrials.gov. We conducted a systematic analysis of these SCI clinical trials, using publicly accessible data downloaded from ClinicalTrials.gov. After extracting all available data for these trials, we categorized each trial according to the types of interventions being tested and the types of outcomes assessed. We then evaluated clinical trial characteristics, both globally and by year, in order to understand the areas of growth and change over time. With regard to clinical trial attributes, we found that most trials have low enrollment, only test single interventions, and have limited numbers of primary outcomes. Some gaps in reporting are apparent; for instance, over 75% of clinical trials with "Completed" status do not have results posted, and the Phase of some trials is incorrectly classified as "Not applicable" despite testing a drug or biological compound. When analyzing trials based on types of interventions assessed, we identified the largest representation in trials testing rehab/training/exercise, neuromodulation, and behavioral modifications. Most highly represented primary outcomes include motor function of the upper and lower extremities, safety, and pain. The most highly represented secondary outcomes include quality of life and pain. Over the past 15 years, we identified increased representation of neuromodulation and rehabilitation trials, and decreased representation of drug trials. Overall, the number of new clinical trials initiated each year continues to grow, signifying a hopeful future for the clinical treatment of SCI. Together, our work provides a comprehensive glimpse into the past, present, and future of SCI clinical trials, and suggests areas for improvement in clinical trial reporting.

Transcription Factor Hb9 Is Expressed in Glial Cell Lineages in the Developing Mouse Spinal Cord.

Hb9 (Mnx1) is a transcription factor described as a spinal cord motor neuron (MN)-specific marker and critical factor for the postmitotic specification of these cells. To date, expression of Hb9 in other cell types has not been reported. We performed a fate-mapping approach to examine distributions of Hb9-expressing cells and their progeny ("Hb9-lineage cells") within the embryonic and adult spinal cord of Hb9cre;Ai14 mice. We found that Hb9-lineage cells are distributed in a gradient of increasing abundance throughout the rostrocaudal spinal cord axis during embryonic and postnatal stages. Furthermore, although the majority of Hb9-lineage cells at cervical spinal cord levels are MNs, at more caudal levels, Hb9-lineage cells include small-diameter dorsal horn neurons, astrocytes, and oligodendrocytes. In the peripheral nervous system, we observed a similar phenomenon with more abundant Hb9-lineage Schwann cells in muscles of the lower body versus upper body muscles. We cultured spinal cord progenitors in vitro and found that gliogenesis was increased by treatment with the caudalizing factor FGF-8B, while glial tdTomato expression was increased by treatment with both FGF-8B and GDF-11. Together, these observations suggest that early and transient expression of Hb9 in spinal cord neural progenitors may be induced by caudalizing factors such as FGF and GDF signaling. Furthermore, our work raises the possibility that early Hb9 expression may influence the development of spinal cord macroglia and Schwann cells, especially at caudal regions. Together, these findings highlight the importance of using caution when designing experiments using Hb9cre mice to perform spinal cord MN-specific manipulations.

Effects of biological sex mismatch on neural progenitor cell transplantation for spinal cord injury in mice.

Despite advancement of neural progenitor cell transplantation to spinal cord injury clinical trials, there remains a lack of understanding of how biological sex of transplanted cells influences outcomes after transplantation. To address this, we transplanted GFP-expressing sex-matched, sex-mismatched, or mixed donor cells into sites of spinal cord injury in adult male and female mice. Biological sex of the donor cells does not influence graft neuron density, glial differentiation, formation of the reactive glial cell border, or graft axon outgrowth. However, male grafts in female hosts feature extensive hypervascularization accompanied by increased vascular diameter and perivascular cell density. We show greater T-cell infiltration within male-to-female grafts than other graft types. Together, these findings indicate a biological sex-specific immune response of female mice to male donor cells. Our work suggests that biological sex should be considered in the design of future clinical trials for cell transplantation in human injury.

Association of delirium screening on hospitalized adults and postacute care utilization: A retrospective cohort study.

BACKGROUND: Patients with delirium have increased hospital length of stay (LOS), morbidity and mortality. Impact of delirium on postacute care (PAC) utilization is not fully characterized. Impact of screening for delirium on general medicine patients is unknown. The objective of this study was to assess impact of screening for delirium on inpatient PAC utilization. METHODS: This was a single center, retrospective cohort study at an academic tertiary care center in Charleston, SC. Patients were selected from adults hospitalized from home and discharged alive between June 2014 and June 2018. The brief confusion assessment method (bCAM) screening was conducted and documented by nursing on admission and every shift thereafter. Outcome measure was the proportion of patients discharged to facility. RESULTS: Of 93,388 non-ICU adult admission between June 2014 and June 2018, 4.4% of those not screened for delirium were discharged to facility versus 15.0% in those screened and 41.4% in those screening positive. Multivariable regression analysis showed that patients screened for delirium were 2.3 times more likely to discharge to facility (95% CI (2.145, 2.429)) while those with a positive bCAM were 3.3 times more likely than those with a negative bCAM to discharge to facility (95% CI (2.949, 3.712)). CONCLUSIONS: After adjusting for demographics, medication orders and comorbidities there was an association between screening for delirium, positive delirium screen and discharge to facility. An appreciation of where and why patients are discharged is imperative to optimize both patient care and cost utilization.

Dorsal horn neuronal sparing predicts the development of at-level mechanical allodynia following cervical spinal cord injury in mice.

Spinal cord injury (SCI) frequently results in immediate and sustained neurological dysfunction, including intractable neuropathic pain in approximately 60-80% of individuals. SCI induces immediate mechanical damage to spinal cord tissue followed by a period of secondary injury in which tissue damage is further propagated, contributing to the development of anatomically unique lesions. Variability in lesion size and location influences the degree of motor and sensory dysfunction incurred by an individual. We predicted that variability in lesion parameters may also explain why some, but not all, experimental animals develop mechanical sensitivity after SCI. To characterize the relationship of lesion anatomy to mechanical allodynia, we utilized a mouse cervical hemicontusion model of SCI that has been shown to lead to the development and persistence of mechanical allodynia in the ipsilateral forelimb after injury. At four weeks post-SCI, the numbers and locations of surviving neurons were quantified along with total lesion volume and nociceptive fiber sprouting. We found that the subset of animals exhibiting mechanical allodynia had significantly increased neuronal sparing in the ipsilateral dorsal horn around the lesion epicenter compared to animals that did not exhibit mechanical allodynia. Additionally, we failed to observe significant differences between groups in nociceptive fiber density in the dorsal horn around the lesion epicenter. Notably, we found that impactor probe displacement upon administration of the SCI surgery was significantly lower in sensitive animals compared with not-sensitive animals. Together, our data indicate that lesion severity negatively correlates with the manifestation of at-level mechanical hypersensitivity and suggests that sparing of dorsal horn neurons may be required for the development of neuropathic pain.

Iatrogenic Oral Ketamine Overdose in Palliative Care.

Background: Optimal pain management in the palliative care setting often requires multiple pharmacological interventions including novel and off-label therapies. Ketamine is an anesthetic agent with increasing evidence supporting its use for pain. Through N-methyl-d-aspartate antagonism and activity at opioid receptors, it is an adjuvant to traditional analgesics with the benefit of being opioid sparing. Ketamine has a wide safety profile with limited reports of overdose. Little is published on supratherpeutic dosing in the pain setting. Objective: We report a case of a 41-year-old male with refractory nociceptive and neuropathic cancer-related pain. Conventional therapies were ineffective. Ketamine was initiated to reduce opioid burden and attenuate pain with good response. The patient received an iatrogenic overdose (10 times ordered dose) of the drug. Several self-limited physiologic and psychologic reactions were observed during subsequent monitoring. Design: This is a study and analysis of a patient with refractory nociceptive and neuropathic pain syndrome treated with ketamine who sustained an iatrogenic overdose of ketamine. Conclusions: Ketamine's use to treat pain is increasing along with its evidence of efficacy. Despite ketamine's wide safety profile, the medication is not without risk, especially in palliative care wherein patients are on multiple drugs with potentially severe interactions. Careful examination of the risks of overdose, especially of the various formulations of the drug, is needed.

An Analysis of Variability in "CatWalk" Locomotor Measurements to Aid Experimental Design and Interpretation.

Preclinical studies in models of neurologic injury and disease rely on behavioral outcomes to measure intervention efficacy. For spinal cord injury, the CatWalk system provides unbiased quantitative assessment of subtle aspects of locomotor function in rodents and so can powerfully detect significant differences between experimental and control groups. Although clearly of key importance, summary group-level data can obscure the variability within and between individual subjects and therefore make it difficult to understand the magnitude of effect in individual animals and the proportion of a group that may show benefit. Here, we calculate reference change intervals (RCIs) that define boundaries of normal variability for measures of rat locomotion on the CatWalk. Our results indicate that many commonly-used outcome measures are highly variable, such that differences of up to 70% from baseline value must be considered normal variation. Many CatWalk outcome variables are also highly correlated and dependent on run speed. Application of calculated RCIs to open access data (https://scicrunch.org/odc-sci) on hindlimb stride length in spinal cord-injured rats illustrates the complementarity between group-level (16 mm change; p = 0.0009) and individual-level (5/32 animals show change outside RCI boundaries) analysis between week 3 and week 6 after injury. We also conclude that interdependence among CatWalk variables implies that test "batteries" require careful composition to ensure that different aspects of defective gait are analyzed. Calculation of RCIs aids in experimental design by quantifying variability and enriches overall data analysis by providing details of change at an individual level that complement group-level analysis.