CD133+ brain tumor-initiating cells are dependent on STAT3 signaling to drive medulloblastoma recurrence

Medulloblastoma (MB), the most common malignant paediatric brain tumor, is currently treated using a combination of surgery, craniospinal radiotherapy and chemotherapy. Owing to MB stem cells (MBSCs), a subset of MB patients remains untreatable despite standard therapy. CD133 is used to identify MBSCs although its functional role in tumorigenesis has yet to be determined. In this work, we showed enrichment of CD133 in Group 3 MB is associated with increased rate of metastasis and poor clinical outcome. The signal transducers and activators of transcription-3 (STAT3) pathway are selectively activated in CD133⁺ MBSCs and promote tumorigenesis through regulation of c-MYC, a key genetic driver of Group 3 MB. We screened compound libraries for STAT3 inhibitors and treatment with the selected STAT3 inhibitors resulted in tumor size reduction in vivo. We propose that inhibition of STAT3 signaling in MBSCs may represent a potential therapeutic strategy to treat patients with recurrent MB.

Neuropathology of bouncer Long Evans, a novel dysmyelinated rat

BACKGROUND AND PURPOSE

Spontaneous animal mutants affected by abnormal formation of myelin in the central nervous system (CNS) are useful in studies on myelinogenesis and remyelination leading to better understanding of cellular and molecular interactions involved in myelin repair. A novel rat mutant, Bouncer Long Evans (LE-bo) is severely dysmyelinated, but with exceptional longevity, and its clinical and pathologic phenotype are described.

METHODS

Clinical observations, genetic studies, and determination of longevity were performed in a colony of rats, including carriers of LE-bo phenotype producing the mutant animals. Comprehensive histologic studies were performed on all perfusion-fixed tissues, and ultrastructural examination of the optic nerve and thoracic part of the spinal cord also was done in rats 1 to 14 weeks old.

RESULTS

The LE-bo phenotype is characterized by whole body tremor, progressively severe ataxia, and severe seizure activity. The LE-bo phenotype is transferred as an autosomal recessive trait and is stable. The LE-bo rat can survive in good health beyond 45 weeks. Neuropathologic changes include severe global dysmyelination, with thin uncompacted myelin sheaths in young rats forming no major dense line, whereas the myelin sheaths of the peripheral nervous system appear normal. Oligodendrocytes degenerate with apparently progressing accumulation of membranous material in the perikaryon. Large numbers of immature glial cells were detected in the CNS of LE-bo rats at 4 to 14 weeks.

CONCLUSION

The LE-bo rat is severely dysmyelinated due to inability of its oligodendrocytes to form myelin sheaths. Similarities of the LE-bo rat and Long Evans Shaker (les) rat neuropathologic features, such as severe dysmyelination, lack of major dense line in uncompacted myelin sheaths, apparent proliferation of oligodendroglial cells, and considerable longevity, are striking and suggest that a LE-bo mutation may functionally affect the myelin basic protein gene.

Insertion of a retrotransposon in Mbp disrupts mRNA splicing and myelination in a new mutant rat

Our understanding of myelination has been greatly enhanced via the study of spontaneous mutants that harbor a defect in a gene encoding one of the major myelin proteins (myelin mutants). In this study, we describe a unique genetic defect in a new myelin mutant called the Long Evans shaker (les) rat that causes severe dysmyelination of the CNS. Myelin deficits result from disruption of the myelin basic protein (Mbp) gene caused by the insertion of an endogenous retrotransposon [early transposons (ETn) element] into a noncoding region (intron 3) of the gene. The ETn element alters the normal splicing dynamics of MBP mRNA, leading to a dramatic reduction in the levels of full-length isoforms (<5% of normal) and the appearance of improperly spliced, chimeric transcripts. Although these aberrant transcripts contain proximal coding regions of the MBP gene (exons 1-3), they are unable to encode functional proteins required to maintain the structural integrity of the myelin sheath. These chimeric transcripts seem capable, however, of producing the necessary signal to initiate and coordinate myelin gene expression because normal numbers of mature oligodendrocytes synthesizing abundant levels of other myelin proteins are present in the mutant CNS. The les rat is thus an excellent model to study alternative functions of MBP beyond its well characterized role in myelin compaction.

Morphological and morphometric studies of the dysmyelinating mutant, the Long Evans shaker rat

The Long Evans shaker (les) rat is a recently identified CNS myelin mutant with an autosomal recessive mode of inheritance. Although scattered myelin sheaths are present in some areas of the CNS, most notably the ventral spinal cord in the young neonatal rat, this myelin is gradually lost, and 8-12 weeks little myelin is present throughout the CNS. Despite this severe myelin deficiency, some mutants may live beyond one year of age. Rare, thin myelin sheaths that are present early in development lack myelin basic protein (MBP) and on ultrastructural examination are poorly compacted and lack a major dense line. Many oligodendrocytes develop an accumulation of vesicles and membranous bodies, but no abnormal cell death is observed. In the optic nerve, cell kinetic studies show an increase in proliferation at early time points in les, while total glial cell counts are also increased in les from 2 months of age. In situ hybridization studies demonstrate that the numbers of mature oligodendrocytes are similar to controls early in life and increase with time compared to controls. There is both a progressive astrocyte hypertrophy and microgliosis. While les has a mutation in the myelin basic protein (mbp) gene, it is dissimilar in both genotype and phenotype to the previously described mbp mouse mutants, shiverer (shi) and shiverer(mld). Unlike shi and its allele, where myelin increases with time and oligodendrocytes become ultrastructurally normal, les oligodendrocytes are permanently disabled, continue to demonstrate cytoplasmic abnormalities, and fail to produce myelin beyond the first weeks of life.

The effects of dietary sodium on hypertension and stroke development in female stroke-prone spontaneously hypertensive rats

Previous studies on male stroke-prone spontaneously hypertensive rats (SHRSP) have shown that a high-salt diet accelerated the onset of hypertension and stroke, resulting in an increased mortality rate at a younger age. The purpose of this study was to examine whether a similar effect is present in female SHRSP. After weaning at 4 weeks of age, 32 female SHRSP were placed on a Japanese-style rat diet containing either 0.3% NaCl or 4% NaCl. Blood pressure (BP), heart rate, and body weight were measured weekly. Beginning at 9 weeks of age, the SHRSP on the 4% NaCl diet began to show a consistently and significantly higher BP than those in the 0.3% NaCl group, reaching an average BP of 245 +/- 9 mmHg at 16 weeks of age as compared to 184 +/- 3 mmHg in the 0.3% NaCl group. Some female SHRSP in the 4% NaCl group started to exhibit behavioral signs of stroke at 12 weeks of age and 100% mortality was found by 20 weeks. There was 0% mortality in the 0.3% NaCl group at that age. A positive correlation was found between the age at which BP surpassed 220 mmHg and the age death occurred due to stroke. No significant difference was noted in the heart rate or body weight measurements between the two groups. The increased mortality rate in the 4% NaCl diet group was accompanied by organ damage as evidenced by the presence of left ventricular hypertrophy, edematous kidneys, renal malfunction, kidney lesions, and cerebral lesions in these female SHRSP. It is concluded that a high-salt diet exacerbates hypertension and caused an increased mortality rate. This increased mortality rate was associated with an increased left ventricular hypertrophy, kidney damage and subsequent malfunction, and cerebrovascular lesions in these female SHRSP.

Prevention of stroke with perindopril treatment in stroke-prone spontaneously hypertensive rats

OBJECTIVE

To determine the protective effects of perindopril treatment in the prevention of stroke and the relation between preventive effects and the histopathology of the brain and kidneys in male stroke-prone spontaneously hypertensive rats (SHRSP).

DESIGN

Prospective animal study.

INTERVENTIONS

Beginning at 6 weeks of age, SHRSP were treated with either distilled water (control) or perindopril for different periods (8, 12 or 24 weeks) and at different dosages (1 or 4 mg/kg per day).

OUTCOME MEASURES

Regular determination of systolic blood pressure, heart rate and body weight until death; at necropsy, macroscopic and microscopic examinations of the brain and kidneys.

RESULTS

Control SHRSP developed severe hypertension (up to 250 mm Hg) by 11 weeks of age and died of stroke within 14 weeks of age. Treatment with perindopril (4 mg/kg per day for 8 or 12 weeks or either 1 or 4 mg/kg per day for 24 weeks) attenuated the blood pressure rise and prevented stroke. In untreated SHRSP, the last blood pressure measurement before the first stroke sign was significantly higher than in SHRSP of the same age treated with perindopril. Withdrawal of the treatment resulted in a rise in blood pressure in all the treatment groups, to approximately 260 mm Hg within 4 weeks. Most of the rats treated for 8 or 12 weeks died within 10 weeks after withdrawal of treatment, whereas those treated for 24 weeks survived up to 43 weeks of age. Treatment also prevented damage to the brain and kidneys and reduced the severity of lesions in the brain and kidneys after treatment withdrawal.

CONCLUSION

Treatment of SHRSP with perindopril prevents stroke through the suppression of blood pressure rise and prevention of tissue damage in the brain and the kidneys. Longer treatment decreased the rate of mortality due to stroke after the withdrawal of treatment as well as the severity of lesions in the brain and kidneys.

An oral ivermectin regimen that eradicates pinworms (Syphacia spp.) in laboratory rats and mice

Pinworm infection, a common problem in laboratory rodent colonies, is difficult to control because anthelmintics like ivermectin eliminate adult worms but have no effect on ova, which can survive ex vivo for prolonged periods. On the premise that repeated treatments with ivermectin would keep rodents parasite-free until all ova matured into ivermectin-susceptible worms in vivo or died in vivo or ex vivo, 80 rats and 25 mice heavily infected with pinworms (Syphacia obvelata and S. muris) were randomized to receive two to five courses of ivermectin 3 days apart or no treatment. During each treatment, ivermectin was given for 4 days in the drinking water; based on water consumption, the mean ivermectin dose was 2.9 and 4.0 mg/kg of body weight per day in rats and mice respectively. Ova production was monitored by weekly cellophane tape tests; 29 to 32 weeks after treatment ended, all rodents were euthanized, and their evacuated large intestinal contents were examined for adult pinworms and ova. Despite intermittently negative cellophane tape test results in untreated rodents (10 rats and 5 mice), all were infected with parasites at the end of the follow-up period. These findings underscore the limitations of the tape test for diagnosis of pinworm infection. After two courses of ivermectin, 1 of 10 rats and four of five mice were infected, whereas after three courses only 1 of 40 rats and one of five mice had parasites. In contrast, none of the 20 rats or 10 mice given either four or five courses of ivermectin had parasites at 30 to 32 weeks of follow-up evaluation. This simple and well-tolerated ivermectin regimen may help to treat and control pinworm infection in laboratory rodent colonies.

Familial dysmyelination in a Long Evans rat mutant

Tremors were observed in 15 Long Evans rats beginning at 10 to 12 days of age. These were followed by progressively worsening ataxia, hind limb paresis, episodes of immobility, and seizures by 5 to 14 weeks. Gross lesions were not observed at necropsy in rats euthanized and perfused at 4 to 16 weeks of age. Neurohistologic examination revealed dysmyelination in the central nervous system. Astrogliosis in the white matter with marked increase of expression of the glial fibrillary acid protein marker was accompanied by diffuse microgliosis. Scattered glial cells, interpreted to be oligodendrocytes, contained minute periodic acid-Schiff-positive cytoplasmic granules. Large mineralized periodic acid-Schiff-positive and laminated structures were observed in the cerebellar white matter, midbrain, and thalamus of rats over 6 weeks old. Neuronal degeneration and loss was evident in the cortex, hippocampus, and midbrain. Large axonal spheroids were found in the ventral and lateral funiculi of the spinal cord. An ultrastructural study of four affected rats revealed an almost complete absence of myelinated axons and normal sheaths, and degeneration and necrosis of oligodendrocytes. The Long Evans shaker rat represents a novel myelin mutant with a remarkable survival period and appears to have an autosomal recessive mode of inheritance.

Perindopril treatment prolonged the lifespan of spontaneously hypertensive rats

OBJECTIVE

The effects of perindopril treatment on hypertension development and the lifespan of adult spontaneously hypertensive rats (SHR) were studied.

DESIGN

Adult male SHR (aged 15 weeks) were given once a day treatment with 4 mg/kg perindopril by gavage for 12 weeks. Littermates given distilled water were used as controls. The blood pressure and lifespan of these rats were studied.

METHODS

The systolic blood pressure (SBP), heart rate and body weight of these rats were measured at regular intervals until they died from natural causes. At necropsy macroscopic and microscopic examinations were made of various organs to determine the cause of death. Serum levels of creatinine, urea and protein were also measured.

RESULTS

Perindopril treatment resulted in the normalization of SBP after 2 weeks of treatment. Withdrawal of the treatment after 12 weeks of treatment caused an elevation of SBP, but the blood pressure of the treated SHR had remained in the normotensive range (< or = 150 mmHg). The heart rate and body weight of the SHR were not affected by the treatment. The average lifespan of the SHR was increased by 12 weeks compared with the control rats. The heart weight, brain lesions and arterial lesions were reduced by the treatment.

CONCLUSION

A 12-week treatment of adult SHR with perindopril was effective in causing a permanent prevention of hypertension, amelioration of some of the tissue damage associated with hypertension and an increase in the lifespan of these rats.