Mark Henkelman

Brain Tumor Surgery with the Toronto Open Magnetic Resonance Imaging System: Preliminary Results for 36 Patients and Analysis of Advantages, Disadvantages, and Future Prospects

OBJECTIVE Frameless navigation systems represent a huge step forward in the surgical treatment of intracranial pathological conditions but lack the ability to provide real-time imaging feedback for assessment of postoperative results, such as catheter positions and the extent of tumor resections. An open magnetic resonance imaging system for intracranial surgery was developed in Toronto, by a multidisciplinary team, to provide real-time intraoperative imaging. METHODS The preliminary experience with a 0.2-T, vertical-gap, magnetic resonance imaging system for intraoperative imaging, which was developed at the University of Toronto for the surgical treatment of patients with intracranial lesions, is described. The system is known as the image-guided minimally invasive therapy unit. RESULTS Between February 1998 and March 1999, 36 procedures were performed, including 21 tumor resections, 12 biopsies, 1 transsphenoidal endoscopic resection, and 2 catheter placements for Ommaya reservoirs. Three complications were observed. All biopsies were successful, and the surgical goals were achieved for all resections. Problems included restricted access resulting from the confines of the magnet and the imaging coil design, difficulties in working in an operating room that is less spacious and familiar, inconsistent image quality, and a lack of nonmagnetic tools that are as effective as standard neurosurgical tools. Advantages included real-time imaging to facilitate surgical planning, to confirm entry into lesions, and to assess the extent of resection and intraoperative and immediate postoperative imaging to confirm the extent of resections, catheter placement, and the absence of postoperative complications. CONCLUSION Intraoperative magnetic resonance imaging has great potential as an aid for intracranial surgery, but a number of logistic problems require resolution.

Bloomsbury report on mouse embryo phenotyping: recommendations from the IMPC workshop on embryonic lethal screening

Identifying genes that are important for embryo development is a crucial first step towards understanding their many functions in driving the ordered growth, differentiation and organogenesis of embryos. It can also shed light on the origins of developmental disease and congenital abnormalities. Current international efforts to examine gene function in the mouse provide a unique opportunity to pinpoint genes that are involved in embryogenesis, owing to the emergence of embryonic lethal knockout mutants. Through internationally coordinated efforts, the International Knockout Mouse Consortium (IKMC) has generated a public resource of mouse knockout strains and, in April 2012, the International Mouse Phenotyping Consortium (IMPC), supported by the EU InfraCoMP programme, convened a workshop to discuss developing a phenotyping pipeline for the investigation of embryonic lethal knockout lines. This workshop brought together over 100 scientists, from 13 countries, who are working in the academic and commercial research sectors, including experts and opinion leaders in the fields of embryology, animal imaging, data capture, quality control and annotation, high-throughput mouse production, phenotyping, and reporter gene analysis. This article summarises the outcome of the workshop, including (1) the vital scientific importance of phenotyping embryonic lethal mouse strains for basic and translational research; (2) a common framework to harmonise international efforts within this context; (3) the types of phenotyping that are likely to be most appropriate for systematic use, with a focus on 3D embryo imaging; (4) the importance of centralising data in a standardised form to facilitate data mining; and (5) the development of online tools to allow open access to and dissemination of the phenotyping data.

Pulmonary hypertension in adult Alk1 heterozygous mice due to oxidative stress

AIMS Mutations in the ALK1 gene, coding for an endothelial-specific receptor of the transforming growth factor-β superfamily, are the underlying cause of hereditary haemorrhagic telangiectasia type 2, but are also associated with familial pulmonary hypertension (PH). We assessed the lung vasculature of mice with a heterozygous deletion of Alk1 (Alk1(+/-)) for disease manifestations and levels of reactive O(2) species (ROS) implicated in both disorders. METHODS AND RESULTS Several signs of PH, including elevated right ventricular (RV) systolic pressure leading to RV hypertrophy, reduced vascular density, and increased thickness and outward remodelling of pulmonary arterioles, were observed in 8- to 18-week-old Alk1(+/-) mice relative to wild-type littermate controls. Higher ROS lung levels were also documented. At 3 weeks, Alk1(+/-) mice were indistinguishable from controls and were prevented from subsequently developing PH when treated with the anti-oxidant Tempol for 6 weeks, confirming a role for ROS in pathogenesis. Levels of NADPH oxidases and superoxide dismutases were higher in adults than newborns, but unchanged in Alk1(+/-) mice vs. controls. Prostaglandin metabolites were also normal in adult Alk1(+/-) lungs. In contrast, NO production was reduced, while endothelial NO synthase (eNOS)-dependent ROS production was increased in adult Alk1(+/-) mice. Pulmonary near resistance arteries from adult Alk1(+/-) mice showed less agonist-induced force and greater acetylcholine-induced relaxation; the later was normalized by catalase or Tempol treatment. CONCLUSION The increased pulmonary vascular remodelling in Alk1(+/-) mice leads to signs of PH and is associated with eNOS-dependent ROS production, which is preventable by anti-oxidant treatment.

Neuroanatomical Phenotypes Are Consistent With Autism‐Like Behavioral Phenotypes in the 15q11‐13 Duplication Mouse Model

Paternally and maternally inherited deletions and duplications of human chromosome 15q11‐13 are relatively common in the human population. Furthermore, duplications in the 15q region are often associated with autism. Both maternal and paternal interstitial 15q11‐13 duplication mouse models have been previously created, where several behavioral differences were found in the paternal duplication (patDp/+) mouse but not in the maternal duplication (matDp/+). These included decreased sociability, behavioral inflexibility, abnormal ultrasonic vocalizations, decreased spontaneous activity, and increased anxiety. Similarly, in the current study, we found several anatomical differences in the patDp/+ mice that were not seen in the matDp/+ mice. Regional differences that are evident only in the paternal duplication are a smaller dentate gyrus and smaller medial striatum. These differences may be responsible for the behavioral inflexibility. Furthermore, a smaller dorsal raphe nucleus could be responsible for the reported serotonin defects. This study highlights consistency that can be found between behavioral and anatomical phenotyping. Autism Res 2015, 8: 545–555.

ENU-induced Mutation in the DNA-binding Domain of KLF3 Reveals Important Roles for KLF3 in Cardiovascular Development and Function in Mice

KLF3 is a Krüppel family zinc finger transcription factor with widespread tissue expression and no previously known role in heart development. In a screen for dominant mutations affecting cardiovascular function in N-ethyl-N-nitrosourea (ENU) mutagenized mice, we identified a missense mutation in the Klf3 gene that caused aortic valvular stenosis and partially penetrant perinatal lethality in heterozygotes. All homozygotes died as embryos. In the first of three zinc fingers, a point mutation changed a highly conserved histidine at amino acid 275 to arginine (Klf3H275R). This change impaired binding of the mutant protein to KLF3s canonical DNA binding sequence. Heterozygous Klf3H275R mutants that died as neonates had marked biventricular cardiac hypertrophy with diminished cardiac chambers. Adult survivors exhibited hypotension, cardiac hypertrophy with enlarged cardiac chambers, and aortic valvular stenosis. A dominant negative effect on protein function was inferred by the similarity in phenotype between heterozygous Klf3H275R mutants and homozygous Klf3 null mice. However, the existence of divergent traits suggested the involvement of additional interactions. We conclude that KLF3 plays diverse and important roles in cardiovascular development and function in mice, and that amino acid 275 is critical for normal KLF3 protein function. Future exploration of the KLF3 pathway provides a new avenue for investigating causative factors contributing to cardiovascular disorders in humans.

Gestational ketogenic diet programs brain structure and susceptibility to depression & anxiety in the adult mouse offspring.

The ketogenic diet (KD) has seen an increase in popularity for clinical and non‐clinical purposes, leading to rise in concern about the diets impact on following generations. The KD is known to have a neurological effect, suggesting that exposure to it during prenatal brain development may alter neuro‐anatomy. Studies have also indicated that the KD has an anti‐depressant effect on the consumer. However, it is unclear whether any neuro‐anatomical and/or behavioral changes would occur in the offspring and persist into adulthood.

A gestational ketogenic diet alters maternal metabolic status as well as offspring physiological growth and brain structure in the neonatal mouse

BackgroundThe use of the ketogenic diet (KD) among women of child-bearing age has been increasing, leading to increased interest in identifying the diet’s suitability during gestation. To date, no studies have thoroughly investigated the effect of a gestational KD on offspring growth. Since ketones have been reported to play a role in cerebral lipid and myelin synthesis, it is particularly important to investigate the diet’s impact on brain anatomy of the offspring.MethodsTo fill this knowledge gap we imaged CD-1 mouse neonates whose mothers were fed either a standard diet (SD) or a KD prior to and during gestation. Images were collected at postnatal (P) 11.5 and 21.5 using Magnetic Resonance Imaging (MRI). Maternal metabolic status was also tracked during lactation, by following their body weight, blood glucose, ketone, cholesterol, and triglyceride concentrations.ResultsThe KD dams exhibit a significant reduction in maternal fertility and litter size, as well as a high risk of developing fatal ketoacidosis by mid-lactation. To increase survival of the KD dams and offspring, fostering of P2.5 pups (from both KD and SD litters) by SD-foster dams was carried out. This resulted in stabilization of blood ketones of the KD dams, and aversion of the fatal ketoacidosis. We also note a slower and smaller weight loss for the KD compared with the SD dams. The average fostered KD pup exhibits retarded growth by P21.5 compared with the average fostered SD pup. An anatomical comparison of their brains further revealed significant structural differences at P11.5, and particularly at P21.5. The KD brain shows a relative bilateral decrease in the cortex, fimbria, hippocampus, corpus callosum and lateral ventricle, but a relative volumetric enlargement of the hypothalamus and medulla.ConclusionA gestational ketogenic diet deleteriously affects maternal fertility and increases susceptibility to fatal ketoacidosis during lactation. Prenatal and early postnatal exposure to a ketogenic diet also results in significant alterations to neonatal brain structure, and results in retarded physiological growth. These alterations could be accompanied by functional and behavioural changes in later postnatal life.

Effects of a ketogenic diet during pregnancy on embryonic growth in the mouse

BackgroundThe increasing use of the ketogenic diet (KD), particularly by women of child-bearing age, raises a question about its suitability during gestation. To date, no studies have thoroughly investigated the direct implications of a gestational ketogenic diet on embryonic development.MethodsTo fill this knowledge gap we imaged CD-1 mouse embryos whose mothers were fed either a Standard Diet (SD) or a KD 30 days prior to, as well as during gestation. Images were collected at embryonic days (E) 13.5 using Optical Projection Tomography (OPT) and at E17.5 using Magnetic Resonance Imaging (MRI).ResultsAn anatomical comparison of the SD and KD embryos revealed that at E13.5 the average KD embryo was volumetrically larger, possessed a relatively larger heart but smaller brain, and had a smaller pharynx, cervical spinal cord, hypothalamus, midbrain, and pons, compared with the average SD embryo. At E17.5 the KD embryo was found to be volumetrically smaller with a relatively smaller heart and thymus, but with enlarged cervical spine, thalamus, midbrain and pons.ConclusionA ketogenic diet during gestation results in alterations in embryonic organ growth. Such alterations may be associated with organ dysfunction and potentially behavioral changes in postnatal life.

Neurobiological Mechanisms of Chemotherapy-induced Cognitive Impairment in a Transgenic Model of Breast Cancer

Animal studies have reinforced clinical reports of cognitive impairment in cancer survivors following chemotherapy but, until now, all pre-clinical research in this area has been conducted on normal rodents. The present study investigated the effects of chemotherapy on cognition and underlying biological mechanisms in the FVB/N-Tg (MMTV-neu) 202 Mul/J mouse, a well-characterized transgenic model of breast cancer that has similarities to the tumorigenesis which occurs in humans. Tumor-bearing and control mice received three weekly injections of a combination of methotrexate + 5-fluorouracil, or an equal volume of saline. Different aspects of learning and memory were measured before and after treatment. The effects of tumor and chemotherapy on neurogenesis, neuro-inflammatory cytokine activity, and brain volume, as they relate to corresponding cognitive changes, were also measured. The toxic effects of chemotherapy extended to the cancerous model in which substantial cognitive impairment was also associated with the disease. Cognitive deficits were greatest in tumorigenic mice that received the anti-cancer drugs. Both tumor growth and chemotherapy caused significant changes in brain volume, including the hippocampus and frontal lobes, two structures that are directly implicated in cognitive tasks that were shown to be vulnerable. The level of hippocampal neurogenesis in adulthood was suppressed in chemotherapy-treated mice and associated with loss of hippocampus-controlled cognitive function. Dysregulation of cytokine activity was found in tumorigenic mice and associated with impaired cognitive performance. The results show that chemotherapy and tumor development independently contribute to cognitive deficits through different biological mechanisms.

Processing, Segmentation, Registration, and Deformation Analysis of 3D MR Images of Mice.

An objective evaluation method to analyze the degree of motion dysfunction in facial expressions due to paralysis is presented. The analysis are based on range data captured for pre-determined facial actions of patients with facial paralysis. The dysfunctions in expressions are analyzed by estimating the degree of asymmetry between left and right sides of 3D expression models that were constructed from measured range data. A symmetric generic face mesh is adapted to the range data using a least squares approximation method to generate these 3D models. The 3D expression models are interpreted as inter-connected meshes of linear springs with point masses and their deformations during expressions are determined by estimating the change of energy in each case. The results obtained for patients in consecutive measurements are compared against that of normal subjects to illustrate the degree of recovery quantitatively.