Peripheral Nerve Ultrasound for the Differentiation between ALS, Inflammatory, and Hereditary Polyneuropathies.

Background and Objectives: Ultrasound (US) is a non-invasive tool for the in vivo detection of peripheral nerve alterations. Materials and Methods: In this study, we applied nerve US to assist the discrimination between the spectrum of amyotrophic lateral sclerosis (ALS, n = 11), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP, n = 5), and genetically confirmed Charcot-Marie-Tooth disease (CMT, n = 5). All participants and n = 15 controls without neurological diseases underwent high-resolution US of the bilateral tibial nerve. The nerve cross-sectional area (CSA) and nerve microvascular blood flow were compared between the groups and related to cerebrospinal fluid (CSF) measures, clinical symptoms, and nerve conduction studies. The analyses are part of a larger multimodal study on the comparison between US and 7 Tesla (7T) magnetic resonance neurography (MRN). Results: The patients and controls were matched with respect to their demographical data. CMT had the longest disease duration, followed by CIDP and ALS. CSA was related to age, weight, and disease duration. CSA was larger in CMT and CIDP compared to ALS and controls. The blood flow was greatest in CIDP, and higher than in CMT, ALS, and controls. In ALS, greater CSA was correlated with greater CSF total protein and higher albumin quotient. The US measures did not correlate with clinical scores or nerve conduction studies in any of the subgroups. Conclusion: Our results point towards the feasibility of CSA and blood flow to discriminate between ALS, CIDP, and CMT, even in groups of small sample size. In ALS, larger CSA could indicate an inflammatory disease subtype characterized by reduced blood-nerve barrier integrity. Our upcoming analysis will focus on the additive value of 7T MRN in combination with US to disentangle the spectrum between more inflammatory or more degenerative disease variants among the disease groups.

Analysis of the growth dynamics of angiogenesis-dependent and -independent experimental glioblastomas by multimodal small-animal PET and MRI.

UNLABELLED: The hypothesis of this study was that distinct experimental glioblastoma phenotypes resembling human disease can be noninvasively distinguished at various disease stages by imaging in vivo. METHODS: Cultured spheroids from 2 human glioblastomas were implanted into the brains of nude rats. Glioblastoma growth dynamics were followed by PET using (18)F-FDG, (11)C-methyl-l-methionine ((11)C-MET), and 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) and by MRI at 3-6 wk after implantation. For image validation, parameters were coregistered with immunohistochemical analysis. RESULTS: Two tumor phenotypes (angiogenic and infiltrative) were obtained. The angiogenic phenotype showed high uptake of (11)C-MET and (18)F-FLT and relatively low uptake of (18)F-FDG. (11)C-MET was an early indicator of vessel remodeling and tumor proliferation. (18)F-FLT uptake correlated to positive Ki67 staining at 6 wk. T1- and T2-weighted MR images displayed clear tumor delineation with strong gadolinium enhancement at 6 wk. The infiltrative phenotype did not accumulate (11)C-MET and (18)F-FLT and impaired the (18)F-FDG uptake. In contrast, the Ki67 index showed a high proliferation rate. The extent of the infiltrative tumors could be observed by MRI but with low contrast. CONCLUSION: For angiogenic glioblastomas, noninvasive assessment of tumor activity corresponds well to immunohistochemical markers, and (11)C-MET was more sensitive than (18)F-FLT at detecting early tumor development. In contrast, infiltrative glioblastoma growth in the absence of blood-brain barrier breakdown is difficult to noninvasively follow by existing imaging techniques, and a negative (18)F-FLT PET result does not exclude the presence of proliferating glioma tissue. The angiogenic model may serve as an advanced system to study imaging-guided antiangiogenic and antiproliferative therapies.

Imaging bone morphogenetic protein 7 induced cell cycle arrest in experimental gliomas.

Bone morphogenetic protein 7 (BMP-7) belongs to the superfamily of transforming growth factor ß-like cytokines, which can act either as tumor suppressors or as tumor promoters depending on cell type and differentiation. Our investigations focused on analyzing the effects of BMP-7 during glioma cell proliferation in vitro and in vivo. BMP-7 treatment decreased the proliferation of Gli36ΔEGFR-LITG glioma cells up to 50%through a cell cycle arrest in the G(1) phase but not by induction of apoptosis. This effect was mediated by the modulation of the expression and phosphorylation of cyclin-dependent kinase 2, cyclin-dependent kinase inhibitor p21, and downstream retinoblastoma protein. Furthermore, in vivo optical imaging of luciferase activity of Gli36ΔEGFR-LITG cells implanted intracranially into nude mice in the presence or absence of BMP-7 treatment corroborated the antiproliferative effects of this cytokine. This report clearly underlines the tumor-suppressive role of BMP-7 in glioma-derived cells. Taken together, our results indicate that manipulating the BMP/transforming growth factor ß signaling cascade may serve as a new strategy for imaging-guided molecular-targeted therapy of malignant gliomas.

Mouse models in neurological disorders: applications of non-invasive imaging.

Neuroimaging techniques represent powerful tools to assess disease-specific cellular, biochemical and molecular processes non-invasively in vivo. Besides providing precise anatomical localisation and quantification, the most exciting advantage of non-invasive imaging techniques is the opportunity to investigate the spatial and temporal dynamics of disease-specific functional and molecular events longitudinally in intact living organisms, so called molecular imaging (MI). Combining neuroimaging technologies with in vivo models of neurological disorders provides unique opportunities to understand the aetiology and pathophysiology of human neurological disorders. In this way, neuroimaging in mouse models of neurological disorders not only can be used for phenotyping specific diseases and monitoring disease progression but also plays an essential role in the development and evaluation of disease-specific treatment approaches. In this way MI is a key technology in translational research, helping to design improved disease models as well as experimental treatment protocols that may afterwards be implemented into clinical routine. The most widely used imaging modalities in animal models to assess in vivo anatomical, functional and molecular events are positron emission tomography (PET), magnetic resonance imaging (MRI) and optical imaging (OI). Here, we review the application of neuroimaging in mouse models of neurodegeneration (Parkinson's disease, PD, and Alzheimer's disease, AD) and brain cancer (glioma).

PET in the diagnosis and management of patients with brain metastasis: current role and future perspectives.

Systemic cancer is the second most common cause of death in developed countries and metastatic brain tumour the most common tumour of the central nervous system (CNS). As the incidence of brain metastases appears to be rising, more accurate non-invasive imaging modalities for diagnosis, prognosis, prediction and follow-up of treatment are requisites for efficient patient management. Positron emission tomography (PET) imaging has the ability to evaluate different aspects of tumour microenvironment on the molecular and cellular level and impact the workup of patients with brain metastasis. This article reviews the current application of PET imaging in patients with metastatic brain disease.

Methods to monitor gene therapy with molecular imaging.

Recent progress in scientific and clinical research has made gene therapy a promising option for efficient and targeted treatment of several inherited and acquired disorders. One of the most critical issues for ensuring success of gene-based therapies is the development of technologies for non-invasive monitoring of the distribution and kinetics of vector-mediated gene expression. In recent years many molecular imaging techniques for safe, repeated and high-resolution in vivo imaging of gene expression have been developed and successfully used in animals and humans. In this review molecular imaging techniques for monitoring of gene therapy are described and specific use of these methods in the different steps of a gene therapy protocol from gene delivery to assessment of therapy response is illustrated. Linking molecular imaging (MI) to gene therapy will eventually help to improve the efficacy and safety of current gene therapy protocols for human application and support future individualized patient treatment.

Early detection of erlotinib treatment response in NSCLC by 3'-deoxy-3'-[F]-fluoro-L-thymidine ([F]FLT) positron emission tomography (PET).

BACKGROUND: Inhibition of the epidermal growth factor receptor (EGFR) has shown clinical success in patients with advanced non-small cell lung cancer (NSCLC). Somatic mutations of EGFR were found in lung adenocarcinoma that lead to exquisite dependency on EGFR signaling; thus patients with EGFR-mutant tumors are at high chance of response to EGFR inhibitors. However, imaging approaches affording early identification of tumor response in EGFR-dependent carcinomas have so far been lacking. METHODOLOGY/PRINCIPAL FINDINGS: We performed a systematic comparison of 3'-Deoxy-3'-[(18)F]-fluoro-L-thymidine ([(18)F]FLT) and 2-[(18)F]-fluoro-2-deoxy-D-glucose ([(18)F]FDG) positron emission tomography (PET) for their potential to identify response to EGFR inhibitors in a model of EGFR-dependent lung cancer early after treatment initiation. While erlotinib-sensitive tumors exhibited a striking and reproducible decrease in [(18)F]FLT uptake after only two days of treatment, [(18)F]FDG PET based imaging revealed no consistent reduction in tumor glucose uptake. In sensitive tumors, a decrease in [(18)F]FLT PET but not [(18)F]FDG PET uptake correlated with cell cycle arrest and induction of apoptosis. The reduction in [(18)F]FLT PET signal at day 2 translated into dramatic tumor shrinkage four days later. Furthermore, the specificity of our results is confirmed by the complete lack of [(18)F]FLT PET response of tumors expressing the T790M erlotinib resistance mutation of EGFR. CONCLUSIONS: [(18)F]FLT PET enables robust identification of erlotinib response in EGFR-dependent tumors at a very early stage. [(18)F]FLT PET imaging may represent an appropriate method for early prediction of response to EGFR TKI treatment in patients with NSCLC.

Multimodal imaging of neural progenitor cell fate in rodents.

For clinical application of stem cell-based therapies, noninvasive detection of applied stem cells is of high importance. We report on the feasibility of detecting implanted neural progenitor cells (NPCs) noninvasively and follow their fate and functional status by sequential multimodal molecular imaging and reporter gene technology. We investigated C17.2 cells stably expressing herpes simplex virus type 1-thymidine kinase (HSV-1-tk) and green fluorescent protein (gfp) (C17.2-tkIRESgfp = C17.2-TIG) or HSV-1-tk, gfp, and firefly luciferase (luc) (C17.2-lucIREStkgfp = C17.2-LITG) and determined the detection sensitivity of positron emission tomography (PET) and bioluminescence imaging (BLI) for these cells in culture and in vivo in subcutaneous and intracranial glioma models. In addition, PET and BLI were used to further investigate and follow the fate of implanted C17.2-LITG cells in an intracranial glioma model. We show that both imaging modalities are sensitive in detecting reporter gene expressing NPCs; however, PET, by the use of 9-[4-[(18)F]fluoro-3-hydroxymethyl)butyl]guanine ([(18)F]FHBG), detects NPCs only at sites of disrupted blood-brain barrier. Furthermore, both imaging modalities can be used to detect stem cell fate and migration and indicate excessive proliferation and aberrant migration. In conclusion, multimodal imaging can be used for longitudinal noninvasive monitoring of grafted NPCs in rodents.

Noninvasive assessment of E2F-1-mediated transcriptional regulation in vivo.

Targeted therapies directed against individual cancer-specific molecular alterations offer the development of disease-specific and individualized treatment strategies. Activation of the transcription factor E2F-1 via alteration of the p16-cyclinD-Rb pathway is one of the key molecular events in the development of gliomas. E2F-1 binds to and activates the E2F-1 promoter in an autoregulatory manner. The human E2F-1 promoter has been shown to be selectively activated in tumor cells with a defect in the pRb pathway. Paradoxically, E2F-1 also carries tumor suppressor function. Our investigations focused on analyzing the dynamics of the activity of the E2F-1 responsive element under basal conditions and certain stimuli such as chemotherapy using molecular imaging technology. We constructed a retrovirus bearing the Cis-E2F-TA-LITG reporter system to noninvasively assess E2F-1-dependent transcriptional regulation in culture and in vivo. We show that our reporter system is sensitive to monitor various changes in cellular E2F-1 levels and its transcriptional control of our reporter system to follow the state of the Rb/E2F pathway and the DNA damage-induced up-regulation of E2F-1 activity in vivo. Exposure to 1,3-bis(2-chloroethyl)-1-nitrosourea leads to increased E2F-1 expression levels in a dose- and time-dependent manner, which can be quantified by imaging in vivo, leading to an alteration of cell cycle progression and caspase 3/7 activity. In summary, noninvasive imaging of E2F-1 as a common downstream regulator of cell cycle progression using the Cis-E2F-TA-LUC-IRES-TKGFP reporter system is highly attractive for evaluating the kinetics of cell cycle regulation and the effects of novel cell cycle targeting anticancer agents in vivo.

Switching on the lights for gene therapy.

Strategies for non-invasive and quantitative imaging of gene expression in vivo have been developed over the past decade. Non-invasive assessment of the dynamics of gene regulation is of interest for the detection of endogenous disease-specific biological alterations (e.g., signal transduction) and for monitoring the induction and regulation of therapeutic genes (e.g., gene therapy). To demonstrate that non-invasive imaging of regulated expression of any type of gene after in vivo transduction by versatile vectors is feasible, we generated regulatable herpes simplex virus type 1 (HSV-1) amplicon vectors carrying hormone (mifepristone) or antibiotic (tetracycline) regulated promoters driving the proportional co-expression of two marker genes. Regulated gene expression was monitored by fluorescence microscopy in culture and by positron emission tomography (PET) or bioluminescence (BLI) in vivo. The induction levels evaluated in glioma models varied depending on the dose of inductor. With fluorescence microscopy and BLI being the tools for assessing gene expression in culture and animal models, and with PET being the technology for possible application in humans, the generated vectors may serve to non-invasively monitor the dynamics of any gene of interest which is proportionally co-expressed with the respective imaging marker gene in research applications aiming towards translation into clinical application.

Bystander killing of malignant glioma by bone marrow-derived tumor-infiltrating progenitor cells expressing a suicide gene.

Adult stem cells are promising cellular vehicles for therapy of malignant gliomas as they have the ability to migrate into these tumors and even track infiltrating tumor cells. However, their clinical use is limited by a low passaging capacity that impedes large-scale production. In the present study, a bone marrow-derived, highly proliferative subpopulation of mesenchymal stem cells (MSCs)-here termed bone marrow-derived tumor-infiltrating cells (BM-TICs)-was genetically modified for the treatment of malignant glioma. Upon injection into the tumor or the vicinity of the tumor, BM-TICs infiltrated solid parts as well as the border of rat 9L glioma. After intra-tumoral injection, BM-TICs expressing the thymidine kinase of herpes simplex virus (HSV-tk) and enhanced green fluorescent protein (BM-TIC-tk-GFP) were detected by non-invasive positron emission tomography (PET) using the tracer 9-[4-[(18)F]fluoro-3-hydroxymethyl)butyl]guanine ([(18)F]FHBG). A therapeutic effect was demonstrated in vitro and in vivo by BM-TICs expressing HSV-tk through bystander-mediated glioma cell killing. Therapeutic efficacy was monitored by PET as well as by magnetic resonance imaging (MRI) and strongly correlated with histological analysis. In conclusion, BM-TICs expressing a suicide gene were highly effective in the treatment of malignant glioma in a rat model and therefore hold great potential for the therapy of malignant brain tumors in humans.

Imaging-guided gene therapy of experimental gliomas.

To further develop gene therapy for patients with glioblastomas, an experimental gene therapy protocol was established comprising a series of imaging parameters for (i) noninvasive assessment of viable target tissue followed by (ii) targeted application of herpes simplex virus type 1 (HSV-1) amplicon vectors and (iii) quantification of treatment effects by imaging. We show that viable target tissue amenable for application of gene therapy vectors can be identified by multitracer positron emission tomography (PET) using 2-(18)F-fluoro-2-deoxy-D-glucose, methyl-(11)C-L-methionine, or 3'-deoxy-3'-(18)F-fluoro-L-thymidine ([(18)F]FLT). Targeted application of HSV-1 amplicon vectors containing two therapeutic genes with synergistic antitumor activity (Escherichia coli cytosine deaminase, cd, and mutated HSV-1 thymidine kinase, tk39, fused to green fluorescent protein gene, gfp) leads to an overall response rate of 68%, with 18% complete responses and 50% partial responses. Most importantly, we show that the "tissue dose" of HSV-1 amplicon vector-mediated gene expression can be noninvasively assessed by 9-[4-(18)F-fluoro-3-(hydroxymethyl)butyl]guanine ([(18)F]FHBG) PET. Therapeutic effects could be monitored by PET with significant differences in [(18)F]FLT accumulation in all positive control tumors and 72% in vivo transduced tumors (P = 0.01) as early as 4 days after prodrug therapy. For all stably and in vivo transduced tumors, cdIREStk39gfp gene expression as measured by [(18)F]FHBG-PET correlated with therapeutic efficiency as measured by [(18)F]FLT-PET. These data indicate that imaging-guided vector application with determination of tissue dose of vector-mediated gene expression and correlation to induced therapeutic effect using multimodal imaging is feasible. This strategy will help in the development of safe and efficient gene therapy protocols for clinical application.

Peri-infarct depolarizations reveal penumbra-like conditions in striatum.

Spreading depression-like peri-infarct depolarizations not only characterize but also worsen penumbra conditions in cortical border zones of experimental focal ischemia. We intended to investigate the relevance of ischemic depolarization in subcortical regions of ischemic territories. Calomel electrodes measured DC potentials simultaneously in the lateral and medial portions of the caudate nucleus (CN) of 11 anesthetized cats after permanent occlusion of the middle cerebral artery. Additionally, platinum electrodes measured cerebral blood flow (CBF) in the CN, and laser Doppler probes CBF in the cortex. Depolarizations (negative DC shifts >10 mV) were obtained in 10 of 11 cats. Further differentiation revealed that short-lasting spreading depression-like depolarizations (SDs; 5 of 10 cats: 5.24 +/- 1.22 min total duration; 23.3 +/- 4.2 mV amplitude) were predominantly found in medial and longer depolarizations (LDs; 4 of 10 cats: 64.7 +/- 47.5 min; 25.0 +/- 11.3 mV) in the lateral CN. Terminal depolarizations (TDs; 6 of 10 cats; without repolarization) occurred immediately after occlusion or at later stages, being then accompanied by elevations of intracranial pressure presumably inducing secondary CBF reduction. CBF tended to be lower in regions with TDs (33.3 +/- 29.9% of control) and LDs (37.3 +/- 22.8%) than in regions with SDs (51.5 +/- 48.0%). We conclude that in focal ischemia, transient peri-infarct depolarizations emerge not only in cortical but also in striatal gray matter, thereby demonstrating the existence of subcortical zones of ischemic penumbra. The generation of these ischemic depolarizations is a multifocal process possibly linked to brain swelling and intracranial pressure rise in the later course of focal ischemia, and therefore a relevant correlate of progressively worsening conditions.

Long-term follow-up after interbody fusion of the cervical spine.

The aim of this work was to add to the body of data on the frequency and severity of degenerative radiographic findings at adjacent levels after anterior cervical interbody fusion and on their clinical impact and to contribute to the insights about their pathogenesis. One hundred eighty patients who were treated by anterior cervical interbody fusion and who had a follow-up of >60 months were clinically and radiologically examined by independent investigators. For all patients, the long-term Odom score was compared with the score as obtained 6 weeks after surgery. For myelopathic cases, both the late Nurick and the Odom score were compared with the initial postoperative situation. For the adjacent disc levels, a radiologic "degeneration score" was defined and assessed both initially and at long-term follow-up. At late follow-up after anterior cervical interbody fusion, additional radiologic degeneration at the adjacent disc levels was found in 92% of the cases, often reflecting a clinical deterioration. The severity of this additional degeneration correlated with the time interval since surgery. The similarity of progression to degeneration between younger trauma patients and older nontrauma patients suggests that both the biomechanical impact of the interbody fusion and the natural progression of pre-existing degenerative disease act as triggering factors for adjacent level degeneration.

Early endovascular treatment of ruptured cerebral aneurysms in patients in very poor neurological condition.

OBJECTIVE: In patients in very poor neurological condition (World Federation of Neurosurgical Societies Grade V) with aneurysmal subarachnoid hemorrhage, early surgery to prevent rebleeding and to allow appropriate treatment of complications is often difficult. The aim of the present study was to evaluate whether early endovascular treatment followed by aggressive proactive treatment of complications (prophylactic hypervolemic hemodilution, hypertensive treatment in the event of systemic hypotension, and appropriate treatment of intracranial hypertension) is an acceptable management strategy for these patients. METHODS: We prospectively studied 11 consecutive patients who presented with acutely ruptured aneurysms and were in very poor neurological condition after resuscitation (World Federation of Neurosurgical Societies Grade V) but did not have a significant intracerebral hemorrhage. These patients received endovascular treatment with Guglielmi detachable coils (Boston Scientific/Target, Fremont, CA). Follow-up consisted of a clinical evaluation based on the Glasgow Outcome Scale. A control angiogram was obtained after 6 months in patients with favorable outcomes to evaluate the occlusion of the aneurysm. RESULTS: There were no deaths or complications directly related to the procedure. Two patients died as a consequence of increased intracranial pressure. The mean follow-up of the surviving patients was 12 months. Two patients had early rebleeding after the coiling and required further treatment. Four patients had good outcomes, two patients were moderately disabled, and three patients were severely disabled. CONCLUSION: This study demonstrates that early endovascular treatment of acutely ruptured cerebral aneurysms in patients evaluated as World Federation of Neurosurgical Societies Grade V allows for aggressive treatment of intracranial hypertension and vasospasm. More than half of the patients had favorable outcomes. Therefore, early endovascular treatment seems to be a valuable alternative to early surgery in patients who present with a very poor clinical grade after subarachnoid hemorrhage. The results of this study are promising but must be interpreted with caution, because a small number of patients were studied.