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No description available.

The blood-brain barrier (BBB) is physiologically essential for brain homeostasis. While it protects the brain from noxious agents, it prevents almost all currently available drugs from crossing to the parenchyma. This greatly hinders drug delivery for the treatment of neurological diseases and disorders such as Parkinson’s, Alzheimer’s and Huntington’s, as well as the development of drugs for the treatment of such diseases. Current drug delivery techniques to the brain are either invasive and target specific, or non-invasive with low special specificity. Neither group of techniques are optimal for long term treatment of patients with neurological diseases or disorders. Focused ultrasound coupled with intravenous administration of microbubbles (FUS) has been proven as an effective technique to selectively and noninvasively open the BBB in multiple in vivo models including non-human primates (NHP). Although this technique has promising potential for clinical outpatient procedures, as well as a powerful tool in the lab, the safety and potential neurological effects of this technique need to be further investigated. This thesis focuses on validating the safety and efficacy of using the FUS technique to open the BBB in NHP as well as the ability of the technique to facility drug delivery. First, a longitudinal study of repeatedly applying the FUS technique targeting the basal ganglia region in four NHP was conducted to determine any potential long-term adverse side effects over a duration of 4-20 months. The safety of the technique was evaluated using both MRI as well as behavioral testing. Results demonstrated that repeated application of the FUS technique to the basal ganglia in NHP did not generate permanent side effects, nor did it induce a permanent opening of the BBB in the targeted region. The second study investigated the potential of the FUS technique as a method to deliver drugs, such as a low dose of haloperidol, to the basal ganglia in NHP and mice to elicit pharmacodynamical effects on responses to behavioral tasks. After opening the BBB in the basal ganglia of mice and NHP, a low dose of haloperidol was successfully delivered generating significant changes in their baseline motor responses to behavioral tasks. Domperidone was also successfully delivered to the caudate of NHP after opening the BBB and induced transient hemilateral neglect. In the final section of this thesis, the safety and efficacy of the FUS technique was evaluated in fully alert NHP. The FUS technique was successful in generating BBB opening volumes larger on average to that of the BBB opening volumes in anesthetized experiments. Safety results through MRI verification as well as behavioral testing during application of the technique demonstrated that the FUS technique did not generate adverse neurological effects. Conversely, the FUS technique was found to induce slight positive effects on the response of the NHP to the behavioral task. Collectively, the work presented in this thesis demonstrates the safety and effectiveness of the FUS technique to open the BBB and deliver neuroactive drugs in the NHP.

Childhood epileptic encephalopathies (EE) are severe neurodevelopmental diseases that manifest in early development. EE is characterized by abnormal electroencephalographic (EEG) activity, intractable seizures comprising of various seizure types, as well as cognitive, behavioral and neurological defects. Developmental and epileptic encephalopathies (DEEs) are a subclass of EEs where the progressive and permanent cognitive and neurophysiological deterioration is not caused by seizure activity alone, but is caused by the same underlying etiology. Recent advances in whole exome sequencing revealed an important role for synaptic dysregulation in DEE and identified multiple new causative variants in synaptic genes. Indeed, mutations in various genes associated with neuronal functions like synaptic transmission and recycling, including transporters, neurotransmitter receptors, and ion channels, have all been identified as causative of DEE. In total, pathogenic DEE-causing variants in over eighty-five genes have been identified and more are likely to follow as next-generation sequencing becomes widely available. DEEs comprise a large group of genetically and phenotypically heterogenous diseases that have been difficult to treat. While in many cases the etiology is unknown, de novo heterozygous missense mutations have often been identified as the underlying cause of DEE. Existing pharmacological interventions by way of antiepileptic drugs leave approximately seventy-percent of DEE patients with intractable seizures. Moreover, these pharmacological treatments do not address the cognitive impairments and associated comorbidities caused by the underlying pathophysiological mechanism. In fact, treatment with antiepileptic drugs may actually worsen cognitive comorbidities due to side effects. Additionally, there are no pharmacological treatments for these cognitive comorbidities other than mood stabilizers and antipsychotics. Therefore, alternative approaches to treatments that address the underlying genetic etiology are necessary. Indeed, the recent utilization of gene therapeutic approaches in other genetic disease models such as spinal muscular atrophy (SMA) has spurred the investigation of gene therapies to treat DEEs. Here, we executed a molecular, behavioral and functional characterization of three preclinical mouse models of DEE involved in synaptic function (Dnm1) and ion channel function (Kcnq3). The human orthologs of the Dnm1 and Kcnq3 genes cause some of the most severe DEE syndromes. Understanding the pathophysiological mechanisms by which mutations in these genes cause disease, is important in identifying and assessing future gene therapeutic interventions. Patients with heterozygous DNM1 pathogenic mutations present with early onset seizures, severe intellectual disability, developmental delay, lack of speech and ambulation, and hypotonia. For the DNM1 dominant-negative model of DEE, we first characterized the Dnm1Ftfl mouse which phenocopies the key disease-defining phenotypes and comorbidities observed in DNM1 patients. Further, we modelled a gene therapy approach in Dnm1Ftfl mice using an RNA interference-based, virally delivered treatment construct. Dnm1Ftfl homozygous mice showed early onset lethality, seizures, growth deficits, hypotonia, and severe ataxia. Molecular analysis of Dnm1Ftfl homozygous mice showed gliosis, cellular degeneration, increased neuronal activation and aberrant metabolic activity, all indicative of recurrent seizure activity. Importantly, our gene therapy treatment significantly rescued all the severe phenotypes associated with DEE, including seizures, early-onset lethality, growth deficits, and aberrant neuronal phenotypes. Thus, our gene therapy approach provided a proof-of-principle for the efficacy of gene silencing to treat DEEs caused by dominant-negative mutations. Second, a DNM1 human variant modelled in mice was generated and characterized. The Dnm1G359A mutation, unlike the Dnm1Ftfl mouse-specific mutation has been identified in patients suffering from DNM1 DEE. Thus, this model allows for a more clinically relevant assessment of the impact of a human DNM1 mutation in mice. In the long run, this model will help validate gene therapeutic approaches that may be clinically relevant to DNM1 DEE patients. The Dnm1G359A mutation, like the Dnm1Ftfl mutation, led to early onset seizures, growth deficits, and lethality, establishing the Dnm1G359A mouse model as a viable model to study DNM1 DEE. In the gain-of-function KCNQ3 model of DEE, Kcnq3R231H mice were characterized molecularly and behaviorally. Patients with KCNQ3 mutations show electrical status epilepticus during sleep (ESES), as well as cognitive and behavioral impairments. The Kcnq3R231H variant led to severe spike-wave discharge phenotype on EEG, decreased maximal seizure threshold, and anxiety-like behavior. Additionally, Kcnq3R231H led to increased localization of Kcnq3 protein at neuronal membranes, suggesting a role for membrane aggregation on disease phenotypes. Altogether, these findings show the viability of preclinical models of both dominant-negative and gain-of-function mutations in replicating key disease-defining phenotypes associated with severe DEEs. Additionally, the results presented here establish a proof-of-principle demonstration that gene silencing can rescue severe phenotypes caused by dominant-negative mutations in DEE. Future studies on both dominant-negative and gain-of-function models should enable an in-depth understanding of mechanistic implications for each mutation, and lead to gene therapeutic strategies to mitigate the debilitating phenotypes of these DEEs.

University of Macau / Institute of Chinese Medical Sciences

Treatment of brain diseases remains extremely challenging partly due to the fact that critical drug delivery is hindered by the blood-brain barrier (BBB), a specialized and highly selective barrier lining the brain vasculature. Focused ultrasound (FUS), combined with systematically administered microbubbles (MBs), has been established as a technique to noninvasively, locally, and transiently open the BBB. The primary mechanism for temporarily opening the BBB using FUS is microbubble cavitation, a phenomenon that occurs when the circulating microbubbles interact with the FUS beam in the brain vasculature. Over the past two decades, many preclinical and clinical applications of FUS-induced BBB opening have been developed, but certain challenges, such as drug delivery route, cavitation control, inflammation onset, and overall accessibility of the technology, have affected its efficient translation to the clinic. This dissertation focuses on optimizing three aspects of FUS-induced BBB opening for therapeutic applications. The first specific aim investigated FUS-induced BBB opening for drug delivery through the intranasal route. Optimal sonication parameters were determined and applied to FUS-enhanced intranasal delivery of neurotrophic factors in a Parkinson’s Disease mouse model. In the second specific aim, cavitation levels affecting the inflammatory response due to BBB opening with FUS were optimized. The relationship between cavitation during FUS-induced BBB opening and the local inflammation was examined, and a cavitation-based controller system was developed to modulate the inflammatory response. In the third specific aim, the devices used for FUS-induced BBB opening were streamlined. A conventional system for FUS-induced BBB opening includes two transducers: one for therapy and another for cavitation monitoring (single element) or imaging (multi-element). In this aim, a single linear array transducer capable of synchronous BBB opening and cavitation imaging was developed, creating a cost-effective and highly accessible “theranostic ultrasound” device. The feasibility of theranostic ultrasound (TUS) was demonstrated in vivo in both mice and non-human primates. In summary, the findings and methodologies in this dissertation optimized FUS-enhanced intranasal delivery across the BBB, developed a cavitation-controlled system to modulate inflammation in the brain, which has been advantageous in reducing pathology and designed a new system for theranostic ultrasound for drug delivery to the brain. Taken altogether, this thesis contributes to the efficient advancement and optimization of FUS-induced BBB opening technology, thus enhancing its clinical adoption in the fight to treat many challenging brain diseases.