Slow cycling and durable Flt3+ progenitors contribute to hematopoiesis under native conditions.

The dynamics of the hematopoietic flux responsible for blood cell production in native conditions remains a matter of debate. Using CITE-seq analyses, we uncovered a distinct progenitor population that displays a cell cycle gene signature similar to the one found in quiescent hematopoietic stem cells. We further determined that the CD62L marker can be used to phenotypically enrich this population in the Flt3+ multipotent progenitor (MPP4) compartment. Functional in vitro and in vivo analyses validated the heterogeneity of the MPP4 compartment and established the quiescent/slow-cycling properties of the CD62L- MPP4 cells. Furthermore, studies under native conditions revealed a novel hierarchical organization of the MPP compartments in which quiescent/slow-cycling MPP4 cells sustain a prolonged hematopoietic activity at steady-state while giving rise to other lineage-biased MPP populations. Altogether, our data characterize a durable and productive quiescent/slow-cycling hematopoietic intermediary within the MPP4 compartment and highlight early paths of progenitor differentiation during unperturbed hematopoiesis.

MGMT Promoter Methylation: Prognostication beyond Treatment Response.

MGMT promoter methylation is related to the increased sensitivity of tumour tissue to chemotherapy with temozolomide (TMZ) and thus to improved patient survival. However, it is unclear how the extent of MGMT promoter methylation affects outcomes. In our study, a single-centre retrospective study, we explore the impact of MGMT promoter methylation in patients with glioblastoma who were operated upon with 5-ALA. Demographic, clinical and histology data, and survival rates were assessed. A total of 69 patients formed the study group (mean age 53.75 ± 15.51 years old). Positive 5-ALA fluorescence was noted in 79.41%. A higher percentage of MGMT promoter methylation was related to lower preoperative tumour volume (p = 0.003), a lower likelihood of 5-ALA positive fluorescence (p = 0.041) and a larger extent of resection EoR (p = 0.041). A higher MGMT promoter methylation rate was also related to improved progression-free survival (PFS) and overall survival (OS) (p = 0.008 and p = 0.006, respectively), even when adjusted for the extent of resection (p = 0.034 and p = 0.042, respectively). A higher number of adjuvant chemotherapy cycles was also related to longer PFS and OS (p = 0.049 and p = 0.030, respectively). Therefore, this study suggests MGMT promoter methylation should be considered as a continuous variable. It is a prognostic factor that goes beyond sensitivity to chemotherapy treatment, as a higher percentage of methylation is related not only to increased EoR and increased PFS and OS, but also to lower tumour volume at presentation and a lower likelihood of 5-ALA fluorescence intraoperatively.

Prognostic Factors for Surgically Managed Spontaneous Spinal Epidural Hematoma: A Single-Center Case Series of 18 Patients.

BACKGROUND: Spontaneous spinal epidural hematoma (SSEH) is a rare pathology, which carries a significant morbidity. OBJECTIVE: To review our institutional experience of surgically managed patients with SSEH, seeking to better understand clinical prognostic factors related to postoperative outcomes and thereby improve counseling of patients before treatment. METHODS: All patients who underwent surgical management of SSEH between September 2011 and 2021. Baseline and postoperative clinical and radiological characteristics are presented, including the American Spinal Injury Association grade (ASIA). Statistical analyses were performed using Stata 13.1. RESULTS: Eighteen patients were identified in total (11 male patients and 7 female patients) with a median age of 59.5 (range 3-83) years. The most common spinal region affected was cervicothoracic (33.3%). Limb weakness (94.4%) and urinary dysfunction (83.3%) represented the most common presenting symptoms. Preoperatively, the presence of spinal cord edema on imaging was associated with worse preoperative Medical Research Council (MRC) grade ( P = .033), female sex was associated with preserved saddle sensation ( P = .04), and patients receiving antiplatelet medication were associated with a higher risk of preoperative axial back pain ( P = .005). Higher postoperative MRC grade was associated with higher preoperative ASIA ( P = .012) and MRC grade ( P = .005), and preservation of saddle sensation ( P = .018). Postoperative improvements in axial back pain were associated with higher preoperative ASIA grade ( P = .035) and anticoagulation treatment ( P = .029). CONCLUSION: Neurosurgical intervention for SSEH yields positive outcomes and benefits patients. Patients with higher preoperative ASIA, MRC grade, and those presenting with preserved saddle sensation may experience further improved clinical outcomes after intervention.

The new metabolic needs of hematopoietic stem cells.

PURPOSE OF REVIEW: Hematopoietic stem cells (HSCs) are endowed with high regenerative potential to supply mature blood cells throughout life, under steady state or stress conditions. HSCs are thought to rely on glycolysis when in a quiescent state and to switch to oxidative phosphorylation to meet their metabolic needs during activation. Recently, a series of important studies reveals a higher degree of complexity that goes well beyond the dichotomy between glycolysis and oxidative phosphorylation. The purpose of this review is to summarize the recent findings highlighting the multifaceted metabolic requirements of HSC homeostasis. RECENT FINDINGS: Emerging evidence points to the importance of lysosomal catabolic activity and noncanonical retinoic acid pathway in maintaining HSC quiescence and stemness. HSC activation into cycle seems to be accompanied by a switch to glycolysis-mitochondrial coupling and to anabolic pathways, including Myc, aspartate-mediated purine synthesis. SUMMARY: Knowledge of metabolism of HSCs has dramatically increased in the past 2 years and reveals unexpected needs of HSCs during both their quiescent and activated state. Understanding how HSCs use metabolism for their functions will offer new opportunity for HSC-based therapies.

Prognostic factors for surgically managed intramedullary spinal cord tumours: a single-centre case series.

PURPOSE: Intramedullary spinal cord tumours (IMSCTs) are comparatively rare neoplasms. We present a single-centre clinical case series of adult patients with surgically managed IMSCTs. METHODS: We performed a retrospective analysis of electronic patient records in the time period spanning July 2010 to July 2021. All adult patients that had undergone surgical management for IMSCTs were eligible for inclusion. Baseline and post-operative clinical and radiological characteristics, along with follow-up data, were assessed. We also performed a literature review with a focus on surgical outcomes for IMSCTs. RESULTS: Sixty-six patients matched our selection criteria, with a median age of 42 years (range 23-85). Thirty-four ependymomas, 17 haemangioblastomas, 12 astrocytomas, 2 lymphomas and 1 teratoma were included. Statistical analysis yielded several significant findings: IMSCTs spanning a greater number of vertebral levels are significantly associated with poor McCormick outcomes (p = 0.03), presence of gait disturbance before surgery is significantly associated with poor outcome for both post-operative McCormick and Nurick scores (p = 0.007), and radicular pain present pre-operatively is significantly associated with a good post-operative McCormick score (p = 0.045). Haemangioblastomas are significantly more likely to have a clear intra-operative dissection plane compared to ependymomas and astrocytomas (p = 0.009). However, astrocytomas have a significantly higher prevalence of good McCormick outcomes compared to ependymomas and haemangioblastomas (p = 0.03). CONCLUSION: Histological diagnosis, cranio-caudal extent of the tumour and the presence or absence of baseline deficits-such as gait impairment and radicular pain-are significant in determining neurological outcomes after surgery for IMSCTs.

Sinonasal carcinosarcoma with cartilaginous and rhabdomyoblastic components: A previously undescribed entity.

Carcinosarcomas are rare, aggressive tumors seldom found in the sinonasal region. They classically consist of sarcomatous spindle cell and carcinomatous squamous cell elements. A 61-year-old woman presented reporting right-sided nasal discharge and obstruction. Examination demonstrated a large right-sided nasal mass, from which a biopsy was taken. Computed tomography and magnetic resonance imaging revealed a mass arising from the maxillary antrum and extending into the nasal cavity, ethmoid air cells, and frontal sinus. Right total maxillectomy with resection of the nasal tumour component was performed. Histological analysis demonstrated a high-grade malignancy with features consistent with carcinosarcoma with cartilaginous and rhabdomyoblastic elements, a histologic pattern that has not previously been described at this site. Magnetic resonance imaging 5 weeks postoperatively showed sizeable recurrence. Adjuvant chemotherapy and radiotherapy were commenced to excellent effect. Carcinosarcomas, though very rare at sinonasal sites, should be considered if biopsy demonstrates undifferentiated high-grade neoplasm with cytokeratin expression. These tumors require aggressive multimodal therapy for optimal outcomes.

Surgical management and long-term follow-up of aberrant right coronary arteries in adults.

OBJECTIVES: Anomalous origins of the right coronary artery (RCA) can cause ischaemia and sudden cardiac death, particularly if the RCA runs between the aorta and pulmonary artery. Conventional coronary artery bypass grafting (CABG) can be affected by early graft failure due to collateral blood flow. We present our institutional experience in managing patients with RCA anomalies. METHODS: A single-center retrospective review of all patients who underwent surgery for aberrant right coronary arteries between 2005 and 2021 was conducted and in-hospital and long-term outcomes were analysed at our institution. RESULTS: A total of 10 patients (5 females, median age: 51 years, 36-62) were identified. They presented with symptoms of chest pain (n = 8), dyspnoea (n = 1) or following cardiac arrest (n = 1). In the majority the RCA originated from the left coronary sinus (n = 9). In one of those patients and one in whom the RCA originated directly from the left anterior descending artery CABG was performed. The other 8 patients were treated using transfer of the RCA ostium. All patients were discharged home (median hospital stay 5 days, range: 4-10). Four patients experienced post-op atrial fibrillation. No other complications were observed. At a median follow-up of 10 years and 9 months, 9 patients were alive and free from cardiac symptoms. One patient died 3 years postsurgery due to liver failure, unrelated to cardiac disease. CONCLUSIONS: In patients with an aberrant RCA, transfer of the ostium into the RCS carries a low surgical risk. It overcomes early graft failure in these patients, who present with a dynamic impairment in RCA blood flow. However, if fixed proximal RCA flow-limiting pathology exists, conventional bypass surgery is feasible.

Systematic Review of Surgical Management of Spinal Intradural Arachnoid Cysts.

OBJECTIVE: Spinal intradural arachnoid cysts (SIACs) are rare pathological lesions that can arise via outpouchings of the arachnoid layer in the spinal canal that can result in neurological deficits. We performed a systematic literature review regarding the current surgical techniques used in the management of SIACs and discussed the prevailing hypotheses surrounding the etiology of SIACs. METHODS: A systematic search of the literature was performed in December 2020 using EMBASE and MEDLINE for reports regarding the surgical management of SIACs. Data were collected regarding the demographics of the patients, classification system used, presence or absence of syrinxes, preoperative imaging modality, surgical approach and extent of resection, and postoperative outcomes and follow-up. RESULTS: Our search yielded 19 reports for inclusion in the present study. The 19 studies included a total of 414 cases, with an overall male/female ratio of 0.93:1. The most common site for the SIACs was the thoracic spinal cord at 77.5%. The symptoms were very similar across the 19 studies. Of the 19 studies, 15 had used resection to manage the SIACs, 10 had used fenestration or marsupialization, and 4 had used cystoarachnoid or cystoperitoneal shunts. CONCLUSIONS: SIACs are rare and debilitating spinal pathological lesions, with the etiology of primary SIACs still not fully elucidated. Multiple surgical approaches have been effective, with the optimal operative strategy largely dependent on the individual patient and cyst factors on a case-by-case basis.

Surgical management and outcomes in spinal intradural arachnoid cysts: the experience from two tertiary neurosurgical centres.

PURPOSE: Evaluation of the presentation and outcomes of different surgical treatment approaches for spinal intradural arachnoid cysts (SIAC). METHODS: Cases were identified from electronic records of two major neurosurgical centres in London over the last 10 years (October 2009-October 2019) that have been surgically treated in both institutions. Clinical findings, surgical technique, and recurrence by procedure were statistically analysed. Statistical analysis was performed with STATA 13.1 Software. RESULTS: A total of 42 patients with SIAC were identified for this study with a mean age at the time of surgery of 53.6 years and a male:female ratio of 8:13. There were 31 patients with primary SIACs and 11 with secondary SIACs. The most common presenting symptom was paraesthesia (n = 27). The most common location of the cyst was in the thoracic region (n = 33). Syrinx was present in 26.2% of SIACs (n = 11). Resection was associated with significantly better postoperative pain compared to other surgical techniques (p = 0.01), significantly poorer postoperative urinary function (p = 0.029), and lower rates of sensory recovery in patients who presented preoperatively with sensory deficit (p = 0.041). No significant difference was seen in symptomatic outcomes between patients with primary and secondary SIACs. CONCLUSION: Resection and drainage are both effective methods of managing SIACs. In this observational study, resection was associated with significantly reduced pain postoperatively when compared with drainage, however also with significantly less improvement in postoperative urinary function. Therefore, resection should be the gold standard management option for SIACs, with drainage as an option where resection is unsafe, and drainage should also be considered in patients presenting with urinary dysfunction.

Transforming growth factor-ß signaling modifies the hematopoietic acute inflammatory response to drive bone marrow failure.

Bone marrow failure syndromes are characterized by ineffective hematopoiesis due to impaired fitness of hematopoietic stem cells. They can be acquired during bone marrow stress or innate and are associated with driver genetic mutations. Patients with a bone marrow failure syndrome are at higher risk of developing secondary neoplasms, including myelodysplastic syndromes and leukemia. Despite the identification of genetic driver mutations, the hematopoietic presentation of the disease is quite heterogeneous, raising the possibility that non-genetic factors contribute to the pathogenesis of the disease. The role of inflammation has emerged as an important contributing factor, but remains to be understood in detail. In this study, we examined the effect of increased transforming growth factor-b (TGFb) signaling, in combination or not with an acute innate immune challenge using polyinosinc:polycytidilic acid (pIC), on the hematopoietic system without genetic mutations. We show that acute rounds of pIC alone drive a benign age-related myeloid cell expansion and increased TGFb signaling alone causes a modest anemia in old mice. In sharp contrast, increased TGFb signaling plus acute pIC challenge result in chronic pancytopenia, expanded hematopoietic stem and progenitor cell pools, and increased bone marrow dysplasia 3-4 months after stress, which are phenotypes similar to human bone marrow failure syndromes. Mechanistically, this disease phenotype is uniquely associated with increased mitochondrial content, increased reactive oxygen species and enhanced caspase-1 activity. Our results suggest that chronic increased TGFb signaling modifies the memory of an acute immune response to drive bone marrow failure without the need for a preexisting genetic insult. Hence, non-genetic factors in combination are sufficient to drive bone marrow failure.

The deubiquitinase USP15 modulates cellular redox and is a therapeutic target in acute myeloid leukemia.

Ubiquitin-specific peptidase 15 (USP15) is a deubiquitinating enzyme implicated in critical cellular and oncogenic processes. We report that USP15 mRNA and protein are overexpressed in human acute myeloid leukemia (AML) as compared to normal hematopoietic progenitor cells. This high expression of USP15 in AML correlates with KEAP1 protein and suppression of NRF2. Knockdown or deletion of USP15 in human and mouse AML models significantly impairs leukemic progenitor function and viability and de-represses an antioxidant response through the KEAP1-NRF2 axis. Inhibition of USP15 and subsequent activation of NRF2 leads to redox perturbations in AML cells, coincident with impaired leukemic cell function. In contrast, USP15 is dispensable for human and mouse normal hematopoietic cells in vitro and in vivo. A preclinical small-molecule inhibitor of USP15 induced the KEAP1-NRF2 axis and impaired AML cell function, suggesting that targeting USP15 catalytic function can suppress AML. Based on these findings, we report that USP15 drives AML cell function, in part, by suppressing a critical oxidative stress sensor mechanism and permitting an aberrant redox state. Furthermore, we postulate that inhibition of USP15 activity with small molecule inhibitors will selectively impair leukemic progenitor cells by re-engaging homeostatic redox responses while sparing normal hematopoiesis.

Surgical Management of Spinal Chordoma: A Systematic Review and Single-Center Experience.

OBJECTIVE: Chordoma is a rare neoplasm of the neuraxis derived from remnants of the primitive notochord. The importance of wide margins and use of adjuvant therapy in spinal chordomas are still contentious points in the management of spinal chordomas. We conducted a systematic review of the surgical management of spinal chordomas alongside our 10-year institutional experience. METHODS: A systematic search of the literature was performed in November 2020 using Embase and MEDLINE for articles regarding the surgical management of chordomas arising from the mobile spine and sacrum. We also searched for all adult patients who were surgically managed for spinal chordomas at our institute between 2010 and 2020. In both the systematic review and our institutional case series, data on adequacy of resection, use of adjuvant therapy, complications, recurrence (local or metastatic), and survival outcomes were collected. RESULTS: We identified and analyzed 42 articles, yielding 1531 patients, from which the overall gross total or wide resection rate was 54.9%. Among the 8 cases in our institutional experience (4 sacral, 3 cervical, and 1 lumbar), we achieved gross total resection in 50% of initial operations. The recurrence rate was 25% in our gross total resection group and 50% where initial resection was subtotal. Of patients, 75% had no evidence of recurrence at most recent follow-up. CONCLUSIONS: Albeit difficult at times because of the proximity to neurovascular tissue, achieving a wide resection followed by adjuvant therapy for spinal chordomas is of great importance. Multidisciplinary discussion is valuable to ensure the best outcome for the patient.

Asymmetrically Segregated Mitochondria Provide Cellular Memory of Hematopoietic Stem Cell Replicative History and Drive HSC Attrition.

The metabolic requirements of hematopoietic stem cells (HSCs) change with their cell cycle activity. However, the underlying role of mitochondria remains ill-defined. Here we found that, after mitochondrial activation with replication, HSCs irreversibly remodel the mitochondrial network and that this network is not repaired after HSC re-entry into quiescence, contrary to hematopoietic progenitors. HSCs keep and accumulate dysfunctional mitochondria through asymmetric segregation during active division. Mechanistically, mitochondria aggregate and depolarize after stress because of loss of activity of the mitochondrial fission regulator Drp1 onto mitochondria. Genetic and pharmacological studies indicate that inactivation of Drp1 causes loss of HSC regenerative potential while maintaining HSC quiescence. Molecularly, HSCs carrying dysfunctional mitochondria can re-enter quiescence but fail to synchronize the transcriptional control of core cell cycle and metabolic components in subsequent division. Thus, loss of fidelity of mitochondrial morphology and segregation is one type of HSC divisional memory and drives HSC attrition.

The effect of fluoride on the structure, function, and proteome of a renal epithelial cell monolayer.

High concentrations of fluoride in the body may cause toxic effects. Here, we investigated the effects of fluoride on the structure, function, and proteome of a cortical collecting duct epithelium in vitro. Kidney tubule cells (M-1) were chosen because the concentration of fluoride in the kidney is 4-5-fold higher than that in plasma. Mouse M-1 cell monolayers were incubated in fluoride-containing media, and the amiloride-sensitive short-circuit current and transepithelial resistance were measured. The Young's modulus of the epithelium was determined using atomic force microscopy, and the effect of fluoride on epithelial structure was assessed using scanning and transmission electron microscopy, and immunofluorescence. Differences in the expression of membrane proteins were evaluated using proteomics and bioinformatics. Fluoride exposure reduced both transepithelial Na+ transport and resistance. The IC50 for fluoride was ∼300 µM for both effects, and the half-times for the decays of ion transport and resistance were 8.4 h and 3.6 days, respectively. Fluoride treatment did not affect the sensitivity of Na+ transport to amiloride. The Young's modulus of the epithelium was also unaffected by fluoride; however, the functional effects of fluoride were accompanied by marked structural effects. Proteomic analysis revealed changes in expression of a number of proteins, and particularly mitochondrial proteins. Treatment with fluoride had profound effects on the structure, function and proteome of a model cortical collecting duct epithelium. Significantly, however, these effects were produced only at concentrations considerably higher than those likely to be encountered in vivo. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1455-1467, 2017.