Spinal Cord Injury Induces Permanent Reprogramming of Microglia into a Disease-Associated State Which Contributes to Functional Recovery.

Microglia are resident myeloid cells of the CNS. Recently, single-cell RNA sequencing (scRNAseq) has enabled description of a disease-associated microglia (DAM) with a role in neurodegeneration and demyelination. In this study, we use scRNAseq to investigate the temporal dynamics of immune cells harvested from the epicenter of traumatic spinal cord injury (SCI) induced in female mice. We find that as a consequence of SCI, baseline microglia undergo permanent transcriptional reprogramming into a previously uncharacterized subtype of microglia with striking similarities to previously reported DAM as well as a distinct microglial state found during development. Using a microglia depletion model we showed that DAM in SCI are derived from baseline microglia and strongly enhance recovery of hindlimb locomotor function following injury.SIGNIFICANCE STATEMENT Although disease-associated microglia (DAM) have been the subject of strong research interest during recent years (Keren-Shaul, 2017; Jordão, 2019), their cellular origin and their role in "normal" acute injury processes is not well understood. Our work directly addresses the origin and the role of DAM in traumatic injury response. Further, we use a microglia depletion model to prove that DAM in spinal cord injury (SCI) are indeed derived from homeostatic microglia, and that they strongly enhance recovery. Thus, in this work we significantly expand the knowledge of immune response to traumatic injury, demonstrate the applicability to human injury via our unique access to injured human spinal cord tissue, and provide the community with a comprehensive dataset for further exploration.

Sex-Specific Effects of Microglia-Like Cell Engraftment during Experimental Autoimmune Encephalomyelitis.

Multiple sclerosis (MS) is a chronic neuroinflammatory disorder of the central nervous system (CNS) that usually presents in young adults and predominantly in females. Microglia, a major resident immune cell in the CNS, are critical players in both CNS homeostasis and disease. We have previously demonstrated that microglia can be efficiently depleted by the administration of tamoxifen in Cx3cr1CreER/+Rosa26DTA/+ mice, with ensuing repopulation deriving from both the proliferation of residual CNS resident microglia and the engraftment of peripheral monocyte-derived microglia-like cells. In this study, tamoxifen was administered to Cx3cr1CreER/+Rosa26DTA/+ and Cx3cr1CreER/+ female and male mice. Experimental autoimmune encephalomyelitis (EAE), a widely used animal model of MS, was induced by active immunization with myelin oligodendrocyte glycoprotein (MOG) one month after tamoxifen injections in Cx3cr1CreER/+Rosa26DTA/+ mice and Cx3cr1CreER/+ mice, a time point when the CNS niche was colonized by microglia derived from both CNS microglia and peripherally-derived macrophages. We demonstrate that engraftment of microglia-like cells following microglial depletion exacerbated EAE in Cx3cr1CreER/+Rosa26DTA/+ female mice as assessed by clinical symptoms and the expression of CNS inflammatory factors, but these findings were not evident in male mice. Higher major histocompatibility complex class II expression and cytokine production in the female CNS contributed to the sex-dependent EAE severity in mice following engraftment of microglia-like cells. An underestimated yet marked sex-dependent microglial activation pattern may exist in the injured CNS during EAE.

Epidemiology of NMOSD in Sweden from 1987 to 2013: A nationwide population-based study.

OBJECTIVE: To report the yearly incidence rate and prevalence of neuromyelitis spectrum disorder (NMOSD) in Sweden and to investigate clinical characteristics, treatment, and outcome. METHODS: We conducted a retrospective study of hospital case records of 294 individuals diagnosed with neuromyelitis optica (NMO) (G36.0 ICD-10, 341.0 ICD-9) in the Swedish National Patient Register from 1987 to end of 2013 or detected by the presence of aquaporin-4 (AQP4) immunoglobulin G (IgG) in serum during the study period. Ninety-two patients (51 NMO and 41 NMOSD) met the 2006 Wingerchuk criteria and were included in the study. Ten patients with an onset of NMO prior to 1987 and alive at the end of 2013 were included when estimating the prevalence. RESULTS: The average yearly incidence rate per 1,000,000 individuals increased significantly from 0.30 (confidence interval [CI] 0.19-0.41) between 1987 and 2006 to 0.79 (CI 0.55-1.03) between 2007 and 2013. The prevalence was 10.4 (CI 8.5-12.6) per 1,000,000 individuals at end of 2013. The median time from onset to first relapse was 1.42 years (range 0.58-3.90). The probability of relapse was 60% and 75% after 5 and 10 years after onset. More than 80% were treated with immunosuppressive drugs. Three patients died during the study period. CONCLUSION: The increased incidence rate during the study period was likely due to heightened awareness and increased access to MRI and AQP4-IgG analysis. Incidence and prevalence of NMO in Sweden correspond to other countries with a predominately Caucasian population. We found that most patients were treated with immunosuppressant drugs, presumably resulting in low mortality among the detected cases.

Syngeneic, in contrast to allogeneic, mesenchymal stem cells have superior therapeutic potential following spinal cord injury.

We evaluated the importance of histocompatibility of transplanted MSCs in terms of therapeutic potential. Mouse syngeneic MSCs or allogeneic MSCs were transplanted following SCI in mouse. In this study we found that syngeneic, but not allogeneic, MSCs alternatively activated macrophages resulting in a down-regulation of pro-inflammation. Syngeneic MSCs also had a general suppressive effect on the immune response as compared to allogeneic MSCs. Additionally, syngeneic, but not allogeneic, MSCs significantly enhanced the recovery of hind limb function. In this study we show that the histocompatibility of transplanted MSCs is of importance for their therapeutic potential.

Mesenchymal stem cells transplanted into spinal cord injury adopt immune cell-like characteristics.

BACKGROUND: Mesenchymal stem cells (MSCs) and their cellular response to various stimuli have been characterized in great detail in culture conditions. In contrast, the cellular response of MSCs in an in vivo setting is still uncharted territory. In this study, we investigated the cellular response of MSCs following transplantation into spinal cord injury (SCI). METHODS: Mouse bone marrow-derived MSCs were transplanted 24 h following severe contusion SCI in mice. As controls, MSCs transplanted to the uninjured spinal cord and non-transplanted MSCs were used. At 7 days post transplantation, the MSCs were isolated from the SCI, and their global transcriptional changes, survival, differentiation, proliferation, apoptosis, and phenotypes were investigated using RNA sequencing, immunohistochemistry, and flow cytometry. RESULTS: MSCs transplanted into SCI downregulated genes related to cell-cycle regulation/progression, DNA metabolic/biosynthetic process, and DNA repair and upregulated genes related to immune system response, cytokine production/response, response to stress/stimuli, signal transduction and signaling pathways, apoptosis, and phagocytosis/endocytosis. MSCs maintained their surface expression of Sca1 and CD29 but upregulated expression of CD45 following transplantation. Transplanted MSCs maintained their surface expression of MHC-I but upregulated surface expression of MHC-II. Transplanted MSCs survived and proliferated to a low extent, did not express Caspase-3, and did not differentiate into neurons or astrocytes. CONCLUSION: MSCs transplanted into SCI upregulate expression of CD45 and MHC-II and expression of genes related to cytokine production, phagocytosis/endocytosis, and immune cells/response and thereby adopt immune cell-like characteristics within the recipient.

Adult Neural Progenitor Cells Transplanted into Spinal Cord Injury Differentiate into Oligodendrocytes, Enhance Myelination, and Contribute to Recovery.

Long-term survival and integration of neural progenitor cells (NPCs) transplanted following spinal cord injury (SCI) have been observed. However, questions concerning the differentiation choice, the mechanism of action, and the contribution of NPCs to functional recovery remains unanswered. Therefore, we investigated the differentiation of NPCs, global transcriptomal changes in transplanted NPCs, the effect of NPCs on neuroinflammation, and the causality between NPC transplantation and functional recovery. We found that NPCs transplanted following SCI differentiate mainly into oligodendrocytes and enhance myelination, upregulate genes related to synaptic signaling and mitochondrial activity, and downregulate genes related to cytokine production and immune system response. NPCs suppress the expression of pro-inflammatory cytokines/chemokines; moreover, NPC ablation confirm that NPCs were responsible for enhanced recovery in hindlimb locomotor function. Understanding the reaction of transplanted NPCs is important for exploiting their full potential. Existence of causality implies that NPCs are useful in the treatment of SCI.

The national incidence of PML in Sweden, 1988-2013.

OBJECTIVE: To investigate the incidence of progressive multifocal leukoencephalopathy (PML) and patient characteristics in Sweden between 1988 and 2013. METHODS: All PML diagnoses in Sweden between 1988 and 2013 were identified in the National Patient Register. Information to validate the diagnosis and patient characteristics was obtained from medical records. RESULTS: Medical record review classified 108 out of 250 patients (43%) as definite (n = 84), probable (n = 4), or possible (n = 20) PML according to diagnostic criteria. Accurate diagnoses were more common in records obtained from neurology departments (82% of patients seen in neurology departments) compared with other departments (31%) (p < 0.001). The incidence of PML increased from a largely stable level at 0.026 (95% confidence interval [CI] 0.021-0.031) per 100,000 individuals per year during 1988-2010 to 0.11 (95% CI 083-0.137) during 2011-2013, during which time there was a notable increase (p < 0.001). Hematologic malignancies (n = 34), HIV/AIDS (n = 33), and autoimmune disease (n = 23) were the most common underlying diseases. Treatment with a monoclonal antibody prior to PML diagnosis was identified in 26 patients. CONCLUSION: An increased incidence of PML in Sweden was observed and coincided with the prior use of monoclonal antibody treatment. The high level of misdiagnosis emphasizes the importance of immediate contact with a neurology center upon suspicion of PML.

Health-Related Quality of Life Dynamics 2 Years Following Aneurysmal Subarachnoid Hemorrhage: A Prospective Cohort Study Using EQ-5D.

BACKGROUND: Previous studies have shown that aneurysmal subarachnoid hemorrhage (aSAH) affects health-related quality of life (HRQoL) to a large extent. However, longitudinal studies on HRQoL after aSAH are scarce, and there is limited knowledge whether different HRQoL dimension scores change over time, and if so, if the scoring differs from results from the general population. OBJECTIVE: To evaluate HRQoL dynamics over time, 2 years following aSAH, and compare the results with general population. METHODS: In a prospective cohort design, 88 consecutive aSAH patients (85% of eligible) were followed up with the generic HRQoL instrument EQ-5D at 3 time points: 6 months, 1 year, and 2 years after the onset. Data were collected in 2006 to 2009, and the results were compared with a general population sample from the Stockholm Public Health Survey 2006, matched by age and sex. RESULTS: Overall HRQoL in the aSAH sample was stationary over time. Improved function was only found in the usual activities dimension (P = .026). HRQoL was most affected in participants reporting comorbidity. Compared with the general population, women in the aSAH sample reported significantly more problems in 4 out of 5 dimensions (mobility, self-care, usual activities, and anxiety/depression). Men in the aSAH sample reported significantly more problems in the usual activities dimension in comparison to the general population. CONCLUSION: HRQoL is stationary during the first 2 years following aSAH, and is significantly worse when compared to the general population. Rehabilitation efforts should be initiated shortly after hospitalization.

A Review of the Segmental Diameter of the Healthy Human Spinal Cord.

Knowledge of the average size and variability of the human spinal cord can be of importance when treating pathological conditions in the spinal cord. Data on healthy human spinal cord morphometrics have been published for more than a century using different techniques of measurements, but unfortunately, comparison of results from different studies is difficult because of the different anatomical landmarks used as reference points along the craniocaudal axis for the measurements. The aim of this review was to compute population estimates of the transverse and anteroposterior diameter of the human spinal cord by comparing and combining previously published data on a normalized craniocaudal axis. We included 11 studies presenting measurements of spinal cord cross-sectional diameters, with a combined sample size ranging from 15 to 488 subjects, depending on spinal cord level. Based on five published studies presenting data on the lengths of the segments of the spinal cord and vertebral column, we calculated the relative positions of all spinal cord neuronal segments and vertebral bony segments and mapped measurements of spinal cord size to a normalized craniocaudal axis. This mapping resulted in better alignment between studies and allowed the calculation of weighted averages and standard deviations (SDs) along the spinal cord. These weighted averages were smoothed using a generalized additive model to yield continuous population estimates for transverse and anteroposterior diameter and associated SDs. The spinal cord had the largest transverse diameter at spinal cord neuronal segment C5 (13.3 ± 2.2), decreased to segment T8 (8.3 ± 2.1), and increased slightly again to 9.4 ± 1.5 at L3. The anteroposterior diameter showed less variation in size along the spinal cord at C5 (7.4 ± 1.6), T8 (6.3 ± 2.0), and L3 (7.5 ± 1.6). All estimates are presented in millimeters ± 2 SDs. We conclude that segmental transverse and anteroposterior diameters of the healthy human spinal cord from different published sources can be combined on a normalized craniocaudal axis and yield meaningful population estimates. These estimates could be useful in routine management of patients with neurodegenerative diseases as well as for clinical research and experimental applications aimed at surgical spinal cord repair.

Adjuvant Stereotactic Radiosurgery Reduces Need for Retreatments in Patients with Meningioma Residuals.

BACKGROUND: Radical surgical resection of cerebral meningiomas involving the dura mater of venous sinuses is challenging, and tumor residuals are frequently left after surgery. This study sought to evaluate the effect of adjuvant stereotactic radiosurgery (aSRS) on the time to significant growth of meningioma residuals requiring retreatment. METHODS: A total of 119 consecutive patients (2004-2013) receiving primary surgical treatment for a meningioma in proximity to a venous structure were included. The patients were assessed retrospectively, with a focus on retreatments and mortality. Radicality of initial tumor surgery was scored using postoperative magnetic resonance imaging. Three subgroups were identified: 1) radical total resection (RTR); 2) near-total resection (NTR), followed by aSRS (NTR + aSRS); and 3) NTR but no aSRS (NTR - aSRS). In the NTR - aSRS group, intervention was initiated after radiologic (magnetic resonance imaging) findings verified growth of residual tumor, in contrast to the NTR + aSRS group, which received aSRS before regrowth. Time to first retreatment, progression-free survival (PFS), and overall survival were analyzed with the log-rank test and multiple-events Cox regression. RESULTS: RTR was associated with the best prognosis. The patients in the NTR + aSRS group had significantly longer time to first retreatment compared with NTR - aSRS patients (P < 0.001). There was also a significant difference in mortality (P < 0.05) and a tendency to prolonged PFS (P = 0.07) in the NTR + aSRS group. The Cox regressions confirmed the positive effects of NTR + aSRS on time to retreatment (hazard ratio, 7.3; P < 0.01) and PFS (hazard ratio, 3.69; P = 0.055). CONCLUSIONS: aSRS of meningioma residuals had a positive effect on tumor control and should be considered in patients with meningioma residuals.