A Simple and Cost-Effective Weight Drop Model to Induce Contusive Spinal Cord Injury: Functional and Histological Outcomes

Background: Animal spinal cord injury (SCI) models have provided a better perception of the mechanisms related to traumatic SCI and evaluation of the effectiveness of experimental therapeutic interventions. Objectives: The aim of this study is to develop a cost-effective modified Allen's device to induce contusive spinal cord injury. Methods: Adult male Wistar rats were subjected to contusive spinal cord injury using a customized weight drop model through 10-g weights delivered from a 25-mm height onto an exposed spinal cord. Locomotor and sensory function during 28 days were assessed. Moreover, histopathological changes were assessed at one week and 28 days post SCI. Results: All the SCI rats showed hind limb paralysis up to 48 h post SCI and neuropathic pain after injury. Histological changes similar to the previous reports for contusion model were observed. Conclusions: According to our findings, little variability was observed in the BBB score of individual rats at 28 days after injury. Our customized device to induce spinal cord injury is a simple and inexpensive alternative method to the highly sophisticated contusion device commonly used to induce SCI.

Characterization of ctx gene Negative Vibrio fluvialis Organisms Isolated from the Environment

A total of five Vibrio fluvialis organisms were isolated from the different environmental samples collected from Dhaka, Satkhira and Khulna. All these isolates were confirmed following API 20NE tests. Molecular analysis showed the absence of ctx, toxR, tdh, trh, stx1, and stx2 genes in these organisms. However, culture filtrates and crude proteins prepared from these organisms showed fluid accumulation in rabbit ileal loop assay, haemolysis of sheep red blood cess, rounding of BHK-21, HeLa and MDCK cells in cell culture assay, hind limb paralysis and death of mice in mice lethality assay and morphological changes in mouse neuronal cell assay. All these results indicated that the environmental V. fluvialis organisms, may not contain different virulence genes, including the ctx gene. However, the other in vivo and in vitro assays indicate that the toxins produced by the V. fluvialis organisms may contain enterotoxin, haemolysin, cytotoxin and neurotoxin. Bangladesh J Microbiol, Volume 36 Number 2 December 2019, pp 91-97

LKB1 specifies neural crest cell fates through pyruvate-alanine cycling

Metabolic processes underlying the development of the neural crest, an embryonic population of multipotent migratory cells, are poorly understood. Here, we report that conditional ablation of the Lkb1 tumor suppressor kinase in mouse neural crest stem cells led to intestinal pseudo-obstruction and hind limb paralysis. This phenotype originated from a postnatal degeneration of the enteric nervous ganglia and from a defective differentiation of Schwann cells. Metabolomic profiling revealed that pyruvate-alanine conversion is enhanced in the absence of Lkb1. Mechanistically, inhibition of alanine transaminases restored glial differentiation in an mTOR-dependent manner, while increased alanine level directly inhibited the glial commitment of neural crest cells. Treatment with the metabolic modulator AICAR suppressed mTOR signaling and prevented Schwann cell and enteric defects of Lkb1 mutant mice. These data uncover a link between pyruvate-alanine cycling and the specification of glial cell fate with potential implications in the understanding of the molecular pathogenesis of neural crest diseases.

Stearoyl-CoA Desaturase (SCD) Enhances Central Nervous System Leukemia

Background: Central nervous system (CNS) involvement by acute lymphoblastic leukemia (ALL) is a major clinical concern. Leukemic cells can be found in the CNS at diagnosis (1-2%) or, more frequently, at relapse (30%). Very little is known about the pathogenesis and therefore there are no targeted therapies. Prophylactic CNS-directed conventional intrathecal chemotherapy or irradiation are required for relapse-free survival. However, they are associated with substantial rates of short and long term toxicity. Therefore, elucidation of molecular mechanisms and pathways mediating leukemia-cell entry and survival in the CNS is needed to develop alternative CNS-directed treatment strategies. Previous studies showed an increased expression of Stearoyl-CoA desaturase (SCD), a key enzyme of the de novo fatty acid synthesis pathway, in B cell precursor (BCP) ALL cells isolated from cerebrospinal fluid (CSF) of patients at the time of CNS relapse. A small SCD positive population was detected in the bone marrow (BM) at leukemia diagnosis in patients who later developed isolated CNS relapse, defining a potential biomarker for CNS relapse. It is unknown, however, if SCD has a functional role in CNS leukemia. Aim: To examine the hypothesis that increased expression of SCD enhances trafficking and survival of human B-ALL cells in the CNS Methods: We analyzed leukemia-cell entry into the CNS using xenografts of human BCP-ALL cell lines. Microarray profile of cells isolated from CNS and BM of transplanted mice was performed. Cell lines were transduced to overexpress human SCD and evaluated in vitro for proliferation kinetics and metabolic SCD activity. In vivo, SCD overexpressing cells were transplanted in NSG mice,sacrificed upon the first symptoms of CNS involvement, e.g. hind limb paralysis. BM, spleen and meninges were collected and analyzed to check human engraftment by FACS. The tumor load was expressed as total amount of leukemic cells in each organ. Competition assays were performed by transplanting SCD overexpressing and WT cells in the same mouse in a 1:1 ratio. Results: BCP-ALL cells transplanted into NSG mice faithfully recapitulated pathological features of meningeal infiltration seen in patients with ALL. Gene expression analysis of cells collected from BM and meninges of leukemic mice revealed up-regulation of the genes belonging to the signaling pathway of sterol regulatory element binding proteins (SREBPs) in ALL cells isolated from the CNS. SCD, whose transcription is controlled by the SREBP family, was significantly upregulated. SCD overexpression did not alter proliferation in vitro. Since SCD introduces a double bond in Stearoyl-CoA, its activity was measured as the ratio of unsaturated/saturated fatty acids in the cells. That ratio was increased in SCD overexpressing cells in vitro, confirming the functionality of the enzyme. In vivo, mice transplanted with SCD overexpressing cells led to a faster onset of CNS disease manifested by a clinical phenotype of earlier hind limb paralysis compared to control and significant increased number of leukemic cells in the CNS (Figure 1A).SCD overexpression also induced CNS engraftment of another B-ALL cell line, REH, which is not naturally prone to invade the central nervous system. Mice transplanted with SCD overexpressing REH cells showed the same phenotype of earlier hind limb paralysis and accumulation of leukemic cells in the CNS as the CNS-prone 018z cells, while WT REH did not show any CNS engraftment but comparable tumor load in BM and spleen (Figure1B). To reproduce the clonal heterogeneity in SCD expression observed previously in patients' BM, we performed a competition assay transplanting SCD overexpressing cells and control cells, expressing different fluorochromes, in the same mouse in a 1:1 ratio. In the CNS, the ratio between SCD overexpressing and WT cells ranged from 2 to 20 fold. This effect was unique to the CNS and not reproducible in the other hematopoietic organs where the 1:1 ratio was maintained (Figure 1C). Moreover, SCD overexpression sensitized leukemic cells to mTOR inhibitors, suggesting a potential therapeutic option Conclusion: SCD has a role in homing and survival of leukemic cells in the CNS and may be used as early predictor of CNS relapse. This study reveals a role for SCD and fatty acid metabolism in the pathogenesis of CNS leukemia suggesting that this pathway maybe targeted for specific therapy of this devastating disease. Figure 1. Figure 1. Disclosures Halsey: Jazz Pharmaceuticals: Honoraria, Other: Support for conference attendance.

Meningoencephalitis caused by pathogenic Sarcocystis species in a naturally infected sheep in Turkey

SummaryA 3-year-old sheep was examined after an acute onset of hind limb paralysis and ataxia. At necropsy, central nervous system, pulmonary and intestinal hyperaemia and ecchymoses in the aortic arch were observed. Main microscopic lesions were confined to the heart, cerebrum and cerebellum. There were a multifocal mild myocarditis and nonsuppurative meningoencephalitis together with protozoal cysts in the heart and the brain. Protozoal cystic structures were observed within many of the myocardial fibers as well as in the cerebrum and cerebellum. Using light microscopy it could not be morphologically determined whether these organisms were Toxoplasma (T.) gondii or Neospora (N.) caninum. Additional diagnostic methods like immunohistochemistry and polymerase chain reaction provided differentiation of Sarcocystis from T. gondii and N. caninum. Transmission electron microscopy demonstrated characteristic features of Sarcocystis sp. as previously described. This is the first confirmed diagnosis of Sarcocystis sp. in the central nervous system of a sheep from Turkey.

In VivoMurine Model of Leukemia Cell-Induced Spinal Bone Destruction

Osteolytic bone lesions can be a consequence of leukemic bone infiltration or focal bone destruction by inflammatory factors released from leukemic cells. Destructive bone lesions have a negative impact on the quality of life of leukemia patients, causing unbearable pain and, in some cases, limb paralysis. However, the mechanism, by which leukemic cells produce destructive bone lesions, and the effect of therapeutics on osteolytic lesions have not been fully elucidated yet and, thus, stand to benefit from anin vivomodel. To that end, HL-60 cells were transformed by retrovirus-mediated constitutively active (CA) STAT5 expression and injected into nonobese diabetic (NOD)/SCID mice via the tail vein. After three weeks, lumbar spines were subjected to histocytometric analysis. Xenograft mice developed hind limb paralysis in 2-3 weeks, which was consistent with the consequences of spinal bone destruction by extramedullary invasion of leukemia cells. Thein vivomodel will improve the understanding and treatment of osteolytic bone lesions caused by myeloid leukemic cells.

PI3Kδ Inhibition Suppresses Central Nervous System Involvement of Acute Lymphoblastic Leukemia

The majority of children and adults who experience relapse of acute lymphoblastic leukemia (ALL) will die from the disease. The presence of leukemic blasts within the cerebrospinal fluid (CSF) is an important predictor of disease recurrence in both the bone marrow (BM) and central nervous system (CNS), a frequent site of disease involvement. In the absence of intrathecal chemotherapy or craniospinal irradiation, 30%‒50% of patients will in fact develop CNS disease. All patients therefore receive CNS prophylaxis. High-risk patients require intensive CNS-directed treatment that causes toxic side effects and can impact cognitive development in children. Patients who develop recurrence in the CNS have limited treatment options and an extremely poor prognosis. The enzyme PI3K plays an important role in many biological effects including cell proliferation, migration, and apoptosis. The d isoform of PI3K is specifically expressed in immune cells. The PI3Kd inhibitor idelalisib is approved for use in combination with rituximab for the treatment of chronic lymphocytic leukemia (CLL). However, little is known about the efficacy of PI3Kd inhibition in ALL. Here, the PI3Kd inhibitor GS-649443, a potent and specific in vivo tool compound, was evaluated in a xenograft mouse model. The in vivo effects of GS-649443 were investigated in a Nalm-6 pre-B ALL SCID model. At approximately 40 days postengraftment, untreated mice all developed symptoms of CNS involvement and displayed hind limb paralysis. Hind limb paralysis is the clinical endpoint for sacrifice, occurring prior to death from progressive BM disease. Mice were treated with GS-649443 by oral gavage beginning on postengraftment day 1 and continuing until the development of clinical symptoms requiring sacrifice (hind limb paralysis, weight loss >20%, respiratory or other distress). Only 17% of GS-649443‒treated mice developed hind limb paralysis at their clinical endpoint, while 100% of vehicle-treated mice showed hind limb paralysis. In addition, mice treated with GS-649443 or vehicle control were paired. When either mouse in a treatment pair reached a clinical endpoint, both were sacrificed so disease burden in individual organs could be compared at matched time points. There was no difference in tumor burden or leukemic cell apoptotic rate in the BM of treated vs vehicle control groups. In contrast, there was a significant decrease in the number of leukemic blasts harvested from the CSF of treated mice (Fig. 1). Consistent with the inhibition of CNS disease progression, GS-649443 significantly prolonged the survival of treated mice (Fig. 2). While compromised blood-brain barrier in leukemic mice may allow therapeutic targeting of CNS disease, it is unknown whether GS-649443 enters the CNS in healthy rodents. Given the well-described effects of idelalisib on CLL cell migration, we hypothesized that PI3Kd blockade impacts disease in this ALL model by impairing leukemia migration into the CNS. To investigate the in vitro effect of GS-649443 on ALL cell migration, transwell migration assays with SDF-1 as chemoattractant were performed. Both GS-649443 and idelalisib suppressed migration of Nalm-6 and primary human ALL cells toward SDF-1. Lastly, the effects of GS-649443 in combination with conventional chemotherapy were examined. GS-649443 alone did not cause significant cytotoxicity of Nalm-6 in vitro, however, treatment with GS-649443 after cytarabine significantly increased apoptosis. Leukemic mice (20 days post-engraftment) were then treated with cytarabine (days 1‒5) in combination with GS-649443 or cytarabine alone (days 1‒7) for 1 cycle. In contrast to the single-agent study, significant decreases in the number of leukemic blasts harvested from both the BM and CSF of treated mice were observed, suggesting that PI3Kd inhibition sensitized ALL cells to cytarabine chemotherapy (Fig. 3). This decrease in residual disease after combination therapy led to significantly prolonged survival in GS-649443‒treated mice (Fig. 4). Taken together, this study provides evidence that PI3Kd inhibition prevents ALL progression in the CNS. In addition, GS-649443 and conventional chemotherapy appear to synergize to decrease residual BM disease. The potential for PI3Kd inhibition to improve chemotherapy response and impede development of CNS disease in ALL warrants further investigation in a translational clinical study. Disclosures Yao: Gilead Sciences, Inc.: Research Funding. Price:Gilead Sciences, Inc.: Research Funding. Olivere:Gilead Sciences, Inc.: Research Funding. Warner:Gilead Sciences, Inc.: Research Funding. Tannheimer:Gilead Sciences: Employment. Sipkins:Gilead Sciences, Inc.: Research Funding.