Divergent transcriptional regulation of astrocyte reactivity across disorders.

Astrocytes respond to injury and disease in the central nervous system with reactive changes that influence the outcome of the disorder1-4. These changes include differentially expressed genes (DEGs) whose contextual diversity and regulation are poorly understood. Here we combined biological and informatic analyses, including RNA sequencing, protein detection, assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) and conditional gene deletion, to predict transcriptional regulators that differentially control more than 12,000 DEGs that are potentially associated with astrocyte reactivity across diverse central nervous system disorders in mice and humans. DEGs associated with astrocyte reactivity exhibited pronounced heterogeneity across disorders. Transcriptional regulators also exhibited disorder-specific differences, but a core group of 61 transcriptional regulators was identified as common across multiple disorders in both species. We show experimentally that DEG diversity is determined by combinatorial, context-specific interactions between transcriptional regulators. Notably, the same reactivity transcriptional regulators can regulate markedly different DEG cohorts in different disorders; changes in the access of transcriptional regulators to DNA-binding motifs differ markedly across disorders; and DEG changes can crucially require multiple reactivity transcriptional regulators. We show that, by modulating reactivity, transcriptional regulators can substantially alter disorder outcome, implicating them as therapeutic targets. We provide searchable resources of disorder-related reactive astrocyte DEGs and their predicted transcriptional regulators. Our findings show that transcriptional changes associated with astrocyte reactivity are highly heterogeneous and are customized from vast numbers of potential DEGs through context-specific combinatorial transcriptional-regulator interactions.

Required growth facilitators propel axon regeneration across complete spinal cord injury.

Transected axons fail to regrow across anatomically complete spinal cord injuries (SCI) in adults. Diverse molecules can partially facilitate or attenuate axon growth during development or after injury1-3, but efficient reversal of this regrowth failure remains elusive4. Here we show that three factors that are essential for axon growth during development but are attenuated or lacking in adults-(i) neuron intrinsic growth capacity2,5-9, (ii) growth-supportive substrate10,11 and (iii) chemoattraction12,13-are all individually required and, in combination, are sufficient to stimulate robust axon regrowth across anatomically complete SCI lesions in adult rodents. We reactivated the growth capacity of mature descending propriospinal neurons with osteopontin, insulin-like growth factor 1 and ciliary-derived neurotrophic factor before SCI14,15; induced growth-supportive substrates with fibroblast growth factor 2 and epidermal growth factor; and chemoattracted propriospinal axons with glial-derived neurotrophic factor16,17 delivered via spatially and temporally controlled release from biomaterial depots18,19, placed sequentially after SCI. We show in both mice and rats that providing these three mechanisms in combination, but not individually, stimulated robust propriospinal axon regrowth through astrocyte scar borders and across lesion cores of non-neural tissue that was over 100-fold greater than controls. Stimulated, supported and chemoattracted propriospinal axons regrew a full spinal segment beyond lesion centres, passed well into spared neural tissue, formed terminal-like contacts exhibiting synaptic markers and conveyed a significant return of electrophysiological conduction capacity across lesions. Thus, overcoming the failure of axon regrowth across anatomically complete SCI lesions after maturity required the combined sequential reinstatement of several developmentally essential mechanisms that facilitate axon growth. These findings identify a mechanism-based biological repair strategy for complete SCI lesions that could be suitable to use with rehabilitation models designed to augment the functional recovery of remodelling circuits.

Astrocyte scar formation aids central nervous system axon regeneration.

Transected axons fail to regrow in the mature central nervous system. Astrocytic scars are widely regarded as causal in this failure. Here, using three genetically targeted loss-of-function manipulations in adult mice, we show that preventing astrocyte scar formation, attenuating scar-forming astrocytes, or ablating chronic astrocytic scars all failed to result in spontaneous regrowth of transected corticospinal, sensory or serotonergic axons through severe spinal cord injury (SCI) lesions. By contrast, sustained local delivery via hydrogel depots of required axon-specific growth factors not present in SCI lesions, plus growth-activating priming injuries, stimulated robust, laminin-dependent sensory axon regrowth past scar-forming astrocytes and inhibitory molecules in SCI lesions. Preventing astrocytic scar formation significantly reduced this stimulated axon regrowth. RNA sequencing revealed that astrocytes and non-astrocyte cells in SCI lesions express multiple axon-growth-supporting molecules. Our findings show that contrary to the prevailing dogma, astrocyte scar formation aids rather than prevents central nervous system axon regeneration.

The impact of an integrated safer use space and safer supply program on non-fatal overdose among emergency shelter residents during a COVID-19 outbreak: a case study.

BACKGROUND: Opioid-related harms, including fatal and non-fatal overdoses, rose dramatically during the COVID-19 pandemic and presented unique challenges during outbreaks in congregate settings such as shelters. People who are deprived of permanent housing have a high prevalence of substance use and substance use disorders, and need nimble, rapid, and portable harm reduction interventions to address the harms of criminalized substance use in an evidence-based manner. CASE STUDY: In February 2021, a COVID-19 outbreak was declared at an emergency men's shelter in Hamilton, Ontario, Canada. Building on pre-existing relationships, community and hospital-based addictions medicine providers and a local harm reduction group collaborated to establish a shelter-based opioid agonist treatment and safer supply program, and a volunteer run safer drug use space that also distributed harm reduction supplies. In the 4 weeks preceding the program, the rate of non-fatal overdoses was 0.93 per 100 nights of shelter bed occupancy. During the 26 days of program operation, there were no overdoses in the safer use space and the rate of non-fatal overdoses in the shelter was 0.17 per 100 nights of shelter bed occupancy. The odds ratio of non-fatal overdose pre-intervention to during intervention was 5.5 (95% CI 1.63-18.55, p = 0.0059). We were not able to evaluate the impact of providing harm reduction supplies and did not evaluate the impact of the program on facilitating adherence to public health isolation and quarantine orders. The program ended as the outbreak waned, as per the direction from the shelter operator. CONCLUSIONS: There was a significant reduction in the non-fatal overdose rate after the safer drug use and safer supply harm reduction program was introduced. Pre-existing relationships between shelter providers, harm reduction groups, and healthcare providers were critical to implementing the program. This is a promising approach to reducing harms from the criminalization of substance use in congregate settings, particularly in populations with a higher prevalence of substance use and substance use disorders.

Pandemic Planning in Homeless Shelters: A Pilot Study of a Coronavirus Disease 2019 (COVID-19) Testing and Support Program to Mitigate the Risk of COVID-19 Outbreaks in Congregate Settings.

We tested 104 residents and 141 staff for coronavirus disease 2019 who failed daily symptom screening in homeless shelters in Hamilton, Canada. We detected 1 resident (1%), 7 staff (5%), and 1 case of secondary spread. Shelter restructuring to allow physical distancing, testing, and isolation can decrease outbreaks in shelters.

Change in body mass index within the first-year post-injury: a VA Traumatic Brain Injury (TBI) model systems study.

OBJECTIVE: To describe change in body mass index (BMI) and weight classification 1-year post- traumatic brain injury (TBI) among Veterans and service members. DESIGN: Prospective observational cohort study. SETTING: VA Polytrauma Rehabilitation Centers. PARTICIPANTS: Veterans and service members (N = 84) enrolled in VA Traumatic Brain Injury Model Systems (VA TBIMS) study with BMI scores at enrollment and 1-year post-injury. INTERVENTIONS: N/A. MAIN OUTCOME MEASURES: BMI scores from height and weight and weight classifications (underweight, normal weight, overweight, obese classes 1-3) defined by WHO. RESULTS: Twenty per cent were obese at time of injury and 24% were obese at 1-year post-injury. Cross-tab analyses revealed 7% of normal weight and 24% overweight participants at time of injury as obese Class 1 one-year post-injury. Univariate models found BMI and tobacco smoking at time of injury were significant predictors of higher BMI scores 1-year post-TBI. Multivariable models found BMI at time of injury and motor functioning, were significant predictors. Preinjury BMI, tobacco smoking and PTSD symptom severity predicted change in weight category. CONCLUSION: While obesity among service members and Veterans post-TBI is below national averages, trends in weight gain between time of injury and 1-year follow-up were observed. Implications for health promotion and chronic disease management efforts with regards to rehabilitation for injured military are discussed. List of Abbreviations: BMI, Body mass index; BRFSS, Behavioural Risk Factor Surveillance; GCS, Glasgow Coma Scale; FIM, Functional Independence Measure; NIDILRR, National Institute on Independent Living and Rehabilitation Research; PCL-C, PTSD checklist-civilian; PSTD, Post-traumatic stress disorder; VA, Veterans Affairs; VA PRC, Veterans Affairs Polytrauma Rehabilitation; VA TBIMS, Veterans Affairs TBI Model Systems.

Conformation-Directed Formation of Self-Healing Diblock Copolypeptide Hydrogels via Polyion Complexation.

Synthetic diblock copolypeptides were designed to incorporate oppositely charged ionic segments that form ß-sheet-structured hydrogel assemblies via polyion complexation when mixed in aqueous media. The observed chain conformation directed assembly was found to be required for efficient hydrogel formation and provided distinct and useful properties to these hydrogels, including self-healing after deformation, microporous architecture, and stability against dilution in aqueous media. While many promising self-assembled materials have been prepared using disordered or liquid coacervate polyion complex (PIC) assemblies, the use of ordered chain conformations in PIC assemblies to direct formation of new supramolecular morphologies is unprecedented. The promising attributes and unique features of the ß-sheet-structured PIC hydrogels described here highlight the potential of harnessing conformational order derived from PIC assembly to create new supramolecular materials.

Post-traumatic epilepsy associations with mental health outcomes in the first two years after moderate to severe TBI: A TBI Model Systems analysis.

PURPOSE: Research suggests that there are reciprocal relationships between mental health (MH) disorders and epilepsy risk. However, MH relationships to post-traumatic epilepsy (PTE) have not been explored. Thus, the objective of this study was to assess associations between PTE and frequency of depression and/or anxiety in a cohort of individuals with moderate-to-severe TBI who received acute inpatient rehabilitation. METHODS: Multivariate regression models were developed using a recent (2010-2012) cohort (n=867 unique participants) from the TBI Model Systems (TBIMS) National Database, a time frame during which self-reported seizures, depression [Patient Health Questionnaire (PHQ)-9], and anxiety [Generalized Anxiety Disorder (GAD-7)] follow-up measures were concurrently collected at year-1 and year-2 after injury. RESULTS: PTE did not significantly contribute to depression status in either the year-1 or year-2 cohort, nor did it contribute significantly to anxiety status in the year-1 cohort, after controlling for other known depression and anxiety predictors. However, those with PTE in year-2 had 3.34 times the odds (p=.002) of having clinically significant anxiety, even after accounting for other relevant predictors. In this model, participants who self-identified as Black were also more likely to report clinical symptoms of anxiety than those who identified as White. PTE was the only significant predictor of comorbid depression and anxiety at year-2 (Odds Ratio 2.71; p=0.049). CONCLUSIONS: Our data suggest that PTE is associated with MH outcomes 2years after TBI, findings whose significance may reflect reciprocal, biological, psychological, and/or experiential factors contributing to and resulting from both PTE and MH status post-TBI. Future work should consider temporal and reciprocal relationships between PTE and MH as well as if/how treatment of each condition influences biosusceptibility to the other condition.

Incidence and risk factors of posttraumatic seizures following traumatic brain injury: A Traumatic Brain Injury Model Systems Study.

OBJECTIVE: Determine incidence of posttraumatic seizure (PTS) following traumatic brain injury (TBI) among individuals with moderate-to-severe TBI requiring rehabilitation and surviving at least 5 years. METHODS: Using the prospective TBI Model Systems National Database, we calculated PTS incidence during acute hospitalization, and at years 1, 2, and 5 postinjury in a continuously followed cohort enrolled from 1989 to 2000 (n = 795). Incidence rates were stratified by risk factors, and adjusted relative risk (RR) was calculated. Late PTS associations with immediate (<24 h), early (24 h-7 day), or late seizures (>7 day) versus no seizure prior to discharge from acute hospitalization was also examined. RESULTS: PTS incidence during acute hospitalization was highest immediately (<24 h) post-TBI (8.9%). New onset PTS incidence was greatest between discharge from inpatient rehabilitation and year 1 (9.2%). Late PTS cumulative incidence from injury to year 1 was 11.9%, and reached 20.5% by year 5. Immediate/early PTS RR (2.04) was increased for those undergoing surgical evacuation procedures. Late PTS RR was significantly greater for individuals who self-identified as a race other than black/white (year 1 RR = 2.22), and for black individuals (year 5 RR = 3.02) versus white individuals. Late PTS was greater for individuals with subarachnoid hemorrhage (year 1 RR = 2.06) and individuals age 23-32 (year 5 RR = 2.43) and 33-44 (year 5 RR = 3.02). Late PTS RR years 1 and 5 was significantly higher for those undergoing surgical evacuation procedures (RR: 3.05 and 2.72, respectively). SIGNIFICANCE: In this prospective, longitudinal, observational study, PTS incidence was similar to that in studies published previously. Individuals with immediate/late seizures during acute hospitalization have increased late PTS risk. Race, intracranial pathologies, and neurosurgical procedures also influenced PTS RR. Further studies are needed to examine the impact of seizure prophylaxis in high-risk subgroups and to delineate contributors to race/age associations on long-term seizure outcomes.

Prognostic models for predicting posttraumatic seizures during acute hospitalization, and at 1 and 2 years following traumatic brain injury.

OBJECTIVE: Posttraumatic seizures (PTS) are well-recognized acute and chronic complications of traumatic brain injury (TBI). Risk factors have been identified, but considerable variability in who develops PTS remains. Existing PTS prognostic models are not widely adopted for clinical use and do not reflect current trends in injury, diagnosis, or care. We aimed to develop and internally validate preliminary prognostic regression models to predict PTS during acute care hospitalization, and at year 1 and year 2 postinjury. METHODS: Prognostic models predicting PTS during acute care hospitalization and year 1 and year 2 post-injury were developed using a recent (2011-2014) cohort from the TBI Model Systems National Database. Potential PTS predictors were selected based on previous literature and biologic plausibility. Bivariable logistic regression identified variables with a p-value < 0.20 that were used to fit initial prognostic models. Multivariable logistic regression modeling with backward-stepwise elimination was used to determine reduced prognostic models and to internally validate using 1,000 bootstrap samples. Fit statistics were calculated, correcting for overfitting (optimism). RESULTS: The prognostic models identified sex, craniotomy, contusion load, and pre-injury limitation in learning/remembering/concentrating as significant PTS predictors during acute hospitalization. Significant predictors of PTS at year 1 were subdural hematoma (SDH), contusion load, craniotomy, craniectomy, seizure during acute hospitalization, duration of posttraumatic amnesia, preinjury mental health treatment/psychiatric hospitalization, and preinjury incarceration. Year 2 significant predictors were similar to those of year 1: SDH, intraparenchymal fragment, craniotomy, craniectomy, seizure during acute hospitalization, and preinjury incarceration. Corrected concordance (C) statistics were 0.599, 0.747, and 0.716 for acute hospitalization, year 1, and year 2 models, respectively. SIGNIFICANCE: The prognostic model for PTS during acute hospitalization did not discriminate well. Year 1 and year 2 models showed fair to good predictive validity for PTS. Cranial surgery, although medically necessary, requires ongoing research regarding potential benefits of increased monitoring for signs of epileptogenesis, PTS prophylaxis, and/or rehabilitation/social support. Future studies should externally validate models and determine clinical utility.

Psychotropic Medication Use During Inpatient Rehabilitation for Traumatic Brain Injury.

OBJECTIVE: To describe psychotropic medication administration patterns during inpatient rehabilitation for traumatic brain injury (TBI) and their relation to patient preinjury and injury characteristics. DESIGN: Prospective observational cohort. SETTING: Multiple acute inpatient rehabilitation units or hospitals. PARTICIPANTS: Individuals with TBI (N=2130; complicated mild, moderate, or severe) admitted for inpatient rehabilitation. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Not applicable. RESULTS: Most frequently administered were narcotic analgesics (72% of sample), followed by antidepressants (67%), anticonvulsants (47%), anxiolytics (33%), hypnotics (30%), stimulants (28%), antipsychotics (25%), antiparkinson agents (25%), and miscellaneous psychotropics (18%). The psychotropic agents studied were administered to 95% of the sample, with 8.5% receiving only 1 and 31.8% receiving ≥6. Degree of psychotropic medication administration varied widely between sites. Univariate analyses indicated younger patients were more likely to receive anxiolytics, antidepressants, antiparkinson agents, stimulants, antipsychotics, and narcotic analgesics, whereas those older were more likely to receive anticonvulsants and miscellaneous psychotropics. Men were more likely to receive antipsychotics. All medication classes were less likely administered to Asians and more likely administered to those with more severe functional impairment. Use of anticonvulsants was associated with having seizures at some point during acute care or rehabilitation stays. Narcotic analgesics were more likely for those with history of drug abuse, history of anxiety and depression (premorbid or during acute care), and severe pain during rehabilitation. Psychotropic medication administration increased rather than decreased during the course of inpatient rehabilitation in each of the medication categories except for narcotics. This observation was also true for medication administration within admission functional levels (defined by cognitive FIM scores), except for those with higher admission FIM cognitive scores. CONCLUSIONS: Many psychotropic medications are used during inpatient rehabilitation. In general, lower admission FIM cognitive score groups were administered more of the medications under investigation compared with those with higher cognitive function at admission. Considerable site variation existed regarding medications administered. The current investigation provides baseline data for future studies of effectiveness.

Predictors of Agitated Behavior During Inpatient Rehabilitation for Traumatic Brain Injury.

OBJECTIVE: To identify predictors of the severity of agitated behavior during inpatient traumatic brain injury (TBI) rehabilitation. DESIGN: Prospective, longitudinal observational study. SETTING: Inpatient rehabilitation centers. PARTICIPANTS: Consecutive patients enrolled between 2008 and 2011, admitted for inpatient rehabilitation after index TBI, who exhibited agitation during their stay (n=555, N=2130). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Daytime Agitated Behavior Scale scores. RESULTS: Infection and lower FIM cognitive scores predicted more severe agitation. The medication classes associated with more severe agitation included sodium channel antagonist anticonvulsants, second-generation antipsychotics, and gamma-aminobutyric acid-A anxiolytics/hypnotics. Medication classes associated with less severe agitation included antiasthmatics, statins, and norepinephrine-dopamine-5 hydroxytryptamine (serotonin) agonist stimulants. CONCLUSIONS: Further support is provided for the importance of careful serial monitoring of both agitation and cognition to provide early indicators of possible beneficial or adverse effects of pharmacologic interventions used for any purpose and for giving careful consideration to the effects of any intervention on underlying cognition when attempting to control agitation. Cognitive functioning was found to predict agitation, medications that have been found in previous studies to enhance cognition were associated with less agitation, and medications that can potentially suppress cognition were associated with more agitation. There could be factors other than the interventions that account for these relations. In addition, the study provides support for treatment of underlying disorders as a possible first step in management of agitation. Although the results of this study cannot be used to draw causal inferences, the associations that were found can be used to generate hypotheses about the most viable interventions that should be tested in future controlled trials.

A new model for in vitro testing of vitreous substitute candidates.

PURPOSE: To describe a new model for in vitro assessment of novel vitreous substitute candidates. METHODS: The biological impact of three vitreous substitute candidates was explored in a retinal explant culture model; a polyalkylimide hydrogel (Bio-Alcamid®), a two component hydrogel of 20 wt.% poly (ethylene glycol) in phosphate buffered saline (PEG) and a cross-linked sodium hyaluronic acid hydrogel (Healaflow®). The gels where applied to explanted adult rat retinas and then kept in culture for 2, 5 and 10 days. Gel-exposed explants were compared with explants incubated under standard tissue culture conditions. Cryosections of the specimens were stained with hematoxylin and eosin, immunohistochemical markers (GFAP, Vimentin, Neurofilament 160, PKC, Rhodopsin) and TUNEL. RESULTS: Explants kept under standard conditions as well as PEG-exposed explants displayed disruption of retinal layers with moderate pyknosis of all neurons. They also displayed moderate labeling of apoptotic cells. Bio-Alcamid®-exposed explants displayed severe thinning and disruption of retinal layers with massive cell death. Healaflow®-treated explants displayed normal retinal lamination with significantly better preservation of retinal neurons compared with control specimens, and almost no signs of apoptosis. Retinas exposed to Healaflow® and retinas kept under standard conditions showed variable labeling of GFAP with generally low expression and some areas of upregulation. PEG-exposed retinas showed increased GFAP labeling and Bio-Alcamid®-exposed retinas showed sparse labeling of GFAP. CONCLUSIONS: Research into novel vitreous substitutes has important implications for both medical and surgical vitreoretinal disease. The in vitro model presented here provides a method of biocompatibility testing prior to more costly and cumbersome in vivo experiments. The explant culture system imposes reactions within the retina including disruption of layers, cell death and gliosis, and the progression of these reactions can be used for comparison of vitreous substitute candidates. Bio-Alcamid® had strong adverse effects on the retina which is consistent with results of prior in vivo trials. PEG gel elicits reactions similar to the control retinas whereas Healaflow® shows protection from culture-induced trauma indicating favorable biocompatibility.

Trehalose-based coacervates for local bioactive protein delivery to the central nervous system.

Therapeutic outcomes of local biomolecule delivery to the central nervous system (CNS) using bulk biomaterials are limited by inadequate drug loading, neuropil disruption, and severe foreign body responses. Effective CNS delivery requires addressing these issues and developing well-tolerated, highly-loaded carriers that are dispersible within local neural parenchyma. Here, we synthesized biodegradable trehalose-based polyelectrolyte oligomers using facile A2:B3:AR thiol-ene Michael addition reactions that form complex coacervates upon mixing of oppositely charged oligomers. Coacervates permit high concentration loading and controlled release of bioactive growth factors, enzymes, and antibodies, with modular formulation parameters that confer tunable release kinetics. Coacervates are cytocompatible with cultured neural cells in vitro and can be formulated to either direct intracellular protein delivery or sequester media containing proteins and remain extracellular. Coacervates serve as effective vehicles for precisely delivering biomolecules, including bioactive neurotrophins, to the mouse striatum following intraparenchymal injection. These results support the use of trehalose-based coacervates as part of therapeutic protein delivery strategies for CNS disorders.

Ischemic and hemorrhagic stroke lesion environments differentially alter the glia repair potential of neural progenitor cell and immature astrocyte grafts.

Using cell grafting to direct glia-based repair mechanisms in adult CNS injuries represents a potential therapeutic strategy for supporting functional neural parenchymal repair. However, glia repair directed by neural progenitor cell (NPC) grafts is dramatically altered by increasing lesion size, severity, and mode of injury. To address this, we studied the interplay between astrocyte differentiation and cell proliferation of NPC in vitro to generate proliferating immature astrocytes (ImA) using hysteretic conditioning. ImA maintain proliferation rates at comparable levels to NPC but showed robust immature astrocyte marker expression including Gfap and Vimentin. ImA demonstrated enhanced resistance to myofibroblast-like phenotypic transformations upon exposure to serum enriched environments in vitro compared to NPC and were more effective at scratch wound closure in vitro compared to quiescent astrocytes. Glia repair directed by ImA at acute ischemic striatal stroke lesions was equivalent to NPC but better than quiescent astrocyte grafts. While ischemic injury environments supported enhanced survival of grafts compared to healthy striatum, hemorrhagic lesions were hostile towards both NPC and ImA grafts leading to poor survival and ineffective modulation of natural wound repair processes. Our findings demonstrate that lesion environments, rather than transcriptional pre-graft states, determine the survival, cell-fate, and glia repair competency of cell grafts applied to acute CNS injuries.

Alteration of mechanical stresses in the murine brain by age and hemorrhagic stroke.

Residual mechanical stresses, also known as solid stresses, emerge during rapid differential growth or remodeling of tissues, as observed in morphogenesis and tumor growth. While residual stresses typically dissipate in most healthy adult organs, as the growth rate decreases, high residual stresses have been reported in mature, healthy brains. However, the origins and consequences of residual mechanical stresses in the brain across health, aging, and disease remain poorly understood. Here, we utilized and validated a previously developed method to map residual mechanical stresses in the brains of mice across three age groups: 5-7 days, 8-12 weeks, and 22 months. We found that residual solid stress rapidly increases from 5-7 days to 8-12 weeks and remains high in mature 22 months mice brains. Three-dimensional mapping revealed unevenly distributed residual stresses from the anterior to posterior coronal brain sections. Since the brain is rich in negatively charged hyaluronic acid, we evaluated the contribution of charged extracellular matrix (ECM) constituents in maintaining solid stress levels. We found that lower ionic strength leads to elevated solid stresses, consistent with its unshielding effect and the subsequent expansion of charged ECM components. Lastly, we demonstrated that hemorrhagic stroke, accompanied by loss of cellular density, resulted in decreased residual stress in the murine brain. Our findings contribute to a better understanding of spatiotemporal alterations of residual solid stresses in healthy and diseased brains, a crucial step toward uncovering the biological and immunological consequences of this understudied mechanical phenotype in the brain.

Ethnoracial disparities in care on a consultation-liaison service at an academic hospital.

BACKGROUND: There is currently an increasing recognition of and focus on structural and institutional racism and its impacts on health disparities. In psychiatry and mental health, research has focused on racial and ethnic disparities in the availability and utilization of mental health services, care in emergency departments, and inpatient psychiatric services. Little is known about disparities in care on general hospital psychiatry consultation-liaison (CL) services. METHODS: In this exploratory study, we conducted a retrospective chart review using electronic health record (EHR) data of all adults (≥ 18 years of age) admitted to inpatient medical or surgical floors at an urban academic medical center for whom a psychiatric consultation was requested during the study period. We examined differences by race and ethnicity in: rates of consultation requests; use of legal holds, constant observation, restraints; follow-up by the CL service; and ultimate disposition. RESULTS: The service received 310 unique consults during the study period. Compared to hospital-wide numbers, Black-identifying patients were over-represented in our sample (11.9% vs 6.6%), while Latinx patients were underrepresented (6.1% vs 9.8%). Of the clinical and outcome variables collected, there were higher odds of being placed on a legal hold both prior to (OR 2.6) and after the consult question (OR 2.98) and in the odds of having a one-to-one observer prior to (OR 2.47) and after (OR 2.9) the initial consult visit for Black-identifying patients, when adjusting for confounders. There were no other measurable differences in care or outcomes by racial or ethnic categories. CONCLUSION: Black-identifying patients may be more likely to receive psychiatric consultation and be placed on legal holds because of a combination of chronic adverse social determinants of health and race-based bias. Conversely, Latinx patients may be less likely to receive psychiatric consultation because of language barriers among other factors. The lack of disparities identified in other domains may be encouraging, but larger studies are needed. Further research is also needed to identify causality and interventions that could help close the gap in care and outcomes for racial and ethnic minorities.

Derivation and transcriptional reprogramming of border-forming wound repair astrocytes after spinal cord injury or stroke in mice.

Central nervous system (CNS) lesions become surrounded by neuroprotective borders of newly proliferated reactive astrocytes; however, fundamental features of these cells are poorly understood. Here we show that following spinal cord injury or stroke, 90% and 10% of border-forming astrocytes derive, respectively, from proliferating local astrocytes and oligodendrocyte progenitor cells in adult mice of both sexes. Temporal transcriptome analysis, single-nucleus RNA sequencing and immunohistochemistry show that after focal CNS injury, local mature astrocytes dedifferentiate, proliferate and become transcriptionally reprogrammed to permanently altered new states, with persisting downregulation of molecules associated with astrocyte-neuron interactions and upregulation of molecules associated with wound healing, microbial defense and interactions with stromal and immune cells. These wound repair astrocytes share morphologic and transcriptional features with perimeningeal limitans astrocytes and are the predominant source of neuroprotective borders that re-establish CNS integrity around lesions by separating neural parenchyma from stromal and immune cells as occurs throughout the healthy CNS.

Proliferation history and transcription factor levels drive direct conversion.

The sparse and stochastic nature of reprogramming has obscured our understanding of how transcription factors drive cells to new identities. To overcome this limit, we developed a compact, portable reprogramming system that increases direct conversion of fibroblasts to motor neurons by two orders of magnitude. We show that subpopulations with different reprogramming potentials are distinguishable by proliferation history. By controlling for proliferation history and titrating each transcription factor, we find that conversion correlates with levels of the pioneer transcription factor Ngn2, whereas conversion shows a biphasic response to Lhx3. Increasing the proliferation rate of adult human fibroblasts generates morphologically mature, induced motor neurons at high rates. Using compact, optimized, polycistronic cassettes, we generate motor neurons that graft with the murine central nervous system, demonstrating the potential for in vivo therapies.