Massimo S. Fiandaca

Plasma phospholipids identify antecedent memory impairment in older adults

Alzheimers disease causes a progressive dementia that currently affects over 35 million individuals worldwide and is expected to affect 115 million by 2050 (ref. 1). There are no cures or disease-modifying therapies, and this may be due to our inability to detect the disease before it has progressed to produce evident memory loss and functional decline. Biomarkers of preclinical disease will be critical to the development of disease-modifying or even preventative therapies. Unfortunately, current biomarkers for early disease, including cerebrospinal fluid tau and amyloid-β levels, structural and functional magnetic resonance imaging and the recent use of brain amyloid imaging or inflammaging, are limited because they are either invasive, time-consuming or expensive. Blood-based biomarkers may be a more attractive option, but none can currently detect preclinical Alzheimers disease with the required sensitivity and specificity. Herein, we describe our lipidomic approach to detecting preclinical Alzheimers disease in a group of cognitively normal older adults. We discovered and validated a set of ten lipids from peripheral blood that predicted phenoconversion to either amnestic mild cognitive impairment or Alzheimers disease within a 2–3 year timeframe with over 90% accuracy. This biomarker panel, reflecting cell membrane integrity, may be sensitive to early neurodegeneration of preclinical Alzheimers disease.

Identification of preclinical Alzheimer's disease by a profile of pathogenic proteins in neurally derived blood exosomes: A case-control study

Proteins pathogenic in Alzheimers disease (AD) were extracted from neurally derived blood exosomes and quantified to develop biomarkers for the staging of sporadic AD.

Image-Guided Convection-Enhanced Delivery Platform in the Treatment of Neurological Diseases

SummaryConvection-enhanced delivery (CED) of substances within the human brain is becoming a more frequent experimental treatment option in the management of brain tumors, and more recently in phase 1 trials for gene therapy in Parkinson’s disease (PD). Benefits of this intracranial drug-transfer technology include a more efficient delivery of large volumes of therapeutic agent to the target region when compared with more standard delivery approaches (i.e., biopolymers, local infusion). In this article, we describe specific technical modifications we have made to the CED process to make it more effective. For example, we developed a reflux-resistant infusion cannula that allows increased infusion rates to be used. We also describe our efforts to visualize the CED process in vivo, using liposomal nanotechnology and real-time intraoperative MRI. In addition to carrying the MRI contrast agent, nanoliposomes also provide a standardized delivery vehicle for the convection of drugs to a specific brain-tissue volume. This technology provides an added level of assurance via visual confirmation of CED, allowing intraoperative alterations to the infusion if there is reflux or aberrant delivery. We propose that these specific modifications to the CED technology will improve efficacy by documenting and standardizing the treatment-volume delivery. Furthermore, we believe that this image-guided CED platform can be used in other translational neuroscience efforts, with eventual clinical application beyond neuro-oncology and PD.

Real-time MR imaging of adeno-associated viral vector delivery to the primate brain.

We are developing a method for real-time magnetic resonance imaging (MRI) visualization of convection-enhanced delivery (CED) of adeno-associated viral vectors (AAV) to the primate brain. By including gadolinium-loaded liposomes (GDL) with AAV, we can track the convective movement of viral particles by continuous monitoring of distribution of surrogate GDL. In order to validate this approach, we infused two AAV (AAV1-GFP and AAV2-hAADC) into three different regions of non-human primate brain (corona radiata, putamen, and thalamus). The procedure was tolerated well by all three animals in the study. The distribution of GFP determined by immunohistochemistry in both brain regions correlated closely with distribution of GDL determined by MRI. Co-distribution was weaker with AAV2-hAADC, although in vivo PET scanning with FMT for AADC activity correlated well with immunohistochemistry of AADC. Although this is a relatively small study, it appears that AAV1 correlates better with MRI-monitored delivery than does AAV2. It seems likely that the difference in distribution may be due to differences in tissue specificity of the two serotypes.

Interventional MRI-guided putaminal delivery of AAV2-GDNF for a planned clinical trial in Parkinson's disease.

Clinical trials involving direct infusion of neurotrophic therapies for Parkinsons disease (PD) have suffered from poor coverage of the putamen. The planned use of a novel interventional-magnetic resonance imaging (iMRI) targeting system for achieving precise, real-time convection-enhanced delivery in a planned clinical trial of adeno-associated virus serotype 2 (AAV2)-glial-derived neurotrophic factor (GDNF) in PD patients was modeled in nonhuman primates (NHP). NHP received bilateral coinfusions of gadoteridol (Gd)/AAV2-GDNF into two sites in each putamen, and three NHP received larger infusion volumes in the thalamus. The average targeting error for cannula tip placement in the putamen was <1 mm, and adjacent putamenal infusions were distributed in a uniform manner. GDNF expression patterns in the putamen were highly correlated with areas of Gd distribution seen on MRI. The distribution volume to infusion volume ratio in the putamen was similar to that in the thalamus, where larger infusions were achieved. Modeling the placement of adjacent 150 and 300 µl thalamic infusions into the three-dimensional space of the human putamen demonstrated coverage of the postcommissural putamen, containment within the striatum and expected anterograde transport to globus pallidus and substantia nigra pars reticulata. The results elucidate the necessary parameters for achieving widespread GDNF expression in the putamenal motor area and afferent substantia nigra of PD patients.

Diagnosis of Parkinson's disease on the basis of clinical and genetic classification: a population-based modelling study

BACKGROUND Accurate diagnosis and early detection of complex diseases, such as Parkinsons disease, has the potential to be of great benefit for researchers and clinical practice. We aimed to create a non-invasive, accurate classification model for the diagnosis of Parkinsons disease, which could serve as a basis for future disease prediction studies in longitudinal cohorts. METHODS We developed a model for disease classification using data from the Parkinsons Progression Marker Initiative (PPMI) study for 367 patients with Parkinsons disease and phenotypically typical imaging data and 165 controls without neurological disease. Olfactory function, genetic risk, family history of Parkinsons disease, age, and gender were algorithmically selected by stepwise logistic regression as significant contributors to our classifying model. We then tested the model with data from 825 patients with Parkinsons disease and 261 controls from five independent cohorts with varying recruitment strategies and designs: the Parkinsons Disease Biomarkers Program (PDBP), the Parkinsons Associated Risk Study (PARS), 23andMe, the Longitudinal and Biomarker Study in PD (LABS-PD), and the Morris K Udall Parkinsons Disease Research Center of Excellence cohort (Penn-Udall). Additionally, we used our model to investigate patients who had imaging scans without evidence of dopaminergic deficit (SWEDD). FINDINGS In the population from PPMI, our initial model correctly distinguished patients with Parkinsons disease from controls at an area under the curve (AUC) of 0·923 (95% CI 0·900-0·946) with high sensitivity (0·834, 95% CI 0·711-0·883) and specificity (0·903, 95% CI 0·824-0·946) at its optimum AUC threshold (0·655). All Hosmer-Lemeshow simulations suggested that when parsed into random subgroups, the subgroup data matched that of the overall cohort. External validation showed good classification of Parkinsons disease, with AUCs of 0·894 (95% CI 0·867-0·921) in the PDBP cohort, 0·998 (0·992-1·000) in PARS, 0·955 (no 95% CI available) in 23andMe, 0·929 (0·896-0·962) in LABS-PD, and 0·939 (0·891-0·986) in the Penn-Udall cohort. Four of 17 SWEDD participants who our model classified as having Parkinsons disease converted to Parkinsons disease within 1 year, whereas only one of 38 SWEDD participants who were not classified as having Parkinsons disease underwent conversion (test of proportions, p=0·003). INTERPRETATION Our model provides a potential new approach to distinguish participants with Parkinsons disease from controls. If the model can also identify individuals with prodromal or preclinical Parkinsons disease in prospective cohorts, it could facilitate identification of biomarkers and interventions. FUNDING National Institute on Aging, National Institute of Neurological Disorders and Stroke, and the Michael J Fox Foundation.

Detection of infusate leakage in the brain using real-time imaging of convection-enhanced delivery: Laboratory investigation

OBJECT The authors have shown that convection-enhanced delivery (CED) of gadoteridol-loaded liposomes (GDLs) into different regions of normal monkey brain results in predictable, widespread distribution of this tracking agent as detected by real-time MR imaging. They also have found that this tracking technique allows monitoring of the distribution of similar nanosized agents such as therapeutic liposomes and viral vectors. A limitation of this procedure is the unexpected leakage of liposomes out of targeted parenchyma or malignancies into sulci and ventricles. The aim of the present study was to evaluate the efficacy of CED after the onset of these types of leakage. METHODS The authors documented this phenomenon in a study of 5 nonhuman primates and 7 canines, comprising 54 CED infusion sessions. Approximately 20% of these infusions resulted in leakage into cerebral ventricles or sulci. All of the infusions and leakage events were monitored with real-time MR imaging. The authors created volume-distributed versus volume-infused graphs for each infusion session. These graphs revealed the rate of distribution of GDL over the course of each infusion and allowed the authors to evaluate the progress of CED before and after leakage. RESULTS The distribution of therapeutics within the target structure ceased to increase or resulted in significant attenuation after the onset of leakage. CONCLUSIONS An analysis of the cases in this study revealed that leakage undermines the efficacy of CED. These findings reiterate the importance of real-time MR imaging visualization during CED to ensure an accurate, robust distribution of therapeutic agents.

Striatal Volume Differences Between Non-human and Human Primates

Convection-enhanced delivery (CED) has recently entered the clinic and represents a promising new delivery option for targeted gene therapy in Parkinsons disease (PD). The prime stereotactic target for the majority of recent gene therapy clinical trials has been the human putamen. The stereotactic delivery of therapeutic agents into putamen (or other subcortical structures) via CED remains problematic due to the difficulty in knowing what volume of therapeutic agent to deliver. Preclinical studies in non-human primates (NHP) offer a way to model treatment strategies prior to clinical trials. Understanding more accurately the volumetric differences in striatum, especially putamen, between NHP and humans is essential in predicting convective volume parameters in human clinical trials. In this study, magnetic resonance images (MRI) were obtained for volumetric measurements of striatum (putamen and caudate nucleus) and whole brain from 11 PD patients, 13 aged healthy human subjects, as well as 8 parkinsonian and 30 normal NHP. The human brain is 13-18 times larger than the monkey brain. However, this ratio is significantly smaller for striatum (5.7-6.5), caudate nucleus (4.6-6.6) and putamen (4.4-6.6). Size and species of the monkeys used for this comparative study are responsible for differences in ratios for each structure between monkeys and humans. This volumetric ratio may have important implications in the design of clinical therapies for PD and Huntingtons disease and should be considered when local therapies such as gene transfer, local protein administration or cellular replacement are translated based on NHP research.

Current status of gene therapy trials for Parkinson's disease.

The incidence of Parkinsons disease (PD) increases greatly with age, and the baby-boomer population can expect to generate a large number of individuals with the disease, all of whom will have significantly increased medical care needs over periods of 20 years or more. This emerging healthcare burden to our society calls for accelerated efforts to understand this disease better and treat it more effectively. The growing interest in gene therapy grew out of a recognition that new medicines may be needed to combat the relentless progression of the disease in the face of conventional pharmaco-therapies and surgical interventions that have so far failed to offer more than palliative relief. The potential of gene therapy to alter dramatically the course of the disease lies very much with the challenge of converting a research tool into a medical option, a process that clearly requires a unique combination of rigor and flexibility. In this review, we examine the unique aspects of gene therapy that make its use in PD attractive, but also analyze the difficulties of employing a medicine that acts for the rest of the patients life.

The critical need for defining preclinical biomarkers in Alzheimer's disease

The increasing number of afflicted individuals with late‐onset Alzheimers disease (AD) poses significant emotional and financial burden on the worlds population. Therapeutics designed to treat symptoms or alter the disease course have failed to make an impact, despite substantial investments by governments, pharmaceutical industry, and private donors. These failures in treatment efficacy have led many to believe that symptomatic disease, including both mild cognitive impairment (MCI) and AD, may be refractory to therapeutic intervention. The recent focus on biomarkers for defining the preclinical state of MCI/AD is in the hope of defining a therapeutic window in which the neural substrate remains responsive to treatment. The ability of biomarkers to adequately define the at‐risk state may ultimately allow novel or repurposed therapeutic agents to finally achieve the disease‐modifying status for AD. In this review, we examine current preclinical AD biomarkers and suggest how to generalize their use going forward.