Barriers between circulation and the central nervous system (CNS) play a key role in the development and modulation of CNS immune responses. Structural variations in the vasculature traversing different anatomical regions within the CNS strongly influence where and how CNS immune responses first develop. Here, we provide an overview of cerebrovascular anatomy, focusing on the blood-CNS interface and how anatomical variations influence steady-state immunology in the compartment. We then discuss how CNS vasculature is affected by and influences the development of different pathophysiological states, such as CNS autoimmune disease, cerebrovascular injury, cerebral ischemia, and infection.Arterial blood enters the cranial cavity, primarily through two sets of blood vessels: the internal carotid arteries, which give rise to anterior brain circulation, and the vertebral arteries, which give rise to posterior circulation. These are interconnected through the circle of Willis located in subarachnoid cisterns at the base of the brain (11). The circle of Willis allows any one of these four vessels to take over brain perfusion and provides a protective mechanism against ischemia. The internal carotid arteries supply the cerebrum, whereas the vertebral arteries join to form the basilar artery that supplies the brainstem and cerebellum. Second-order branches form vessels that traverse the subarachnoid space and pia mater, giving rise to smaller arterioles ( Fig. 1) that enter the brain parenchyma ( Fig. 1A) (12). These penetrating vessels are surrounded by perivascular spaces that can vary in size. For example, in the cortex, a packed barrier of endothelial cells, basement membrane, and glia limitans surrounds penetrating arteries, leaving little to no fluid-filled space, whereas the lenticulostriate branches in the basal ganglia are surrounded by a larger perivascular space (13). Pia mater covers all arteries in the subarachnoid space, whereas coverage of veins is incomplete. In addition, the fluid in perivascular spaces can move directly into the subarachnoid space through fenestrations in the pia mater ( Fig. 1A) (14). This allows direct communication between perivascular, subpial, and subarachnoid spaces. The communication of the perivascular compartment with the subarachnoid space plays an important role in antigen presentation, which will be described in more detail below. Venous drainage in the CNS occurs through an interconnected system of valveless veins and dural sinuses. Postcapillary venules in the CNS parenchyma drain capillaries and are surrounded by fluidfilled perivascular spaces (Figs. 1, A and B, and 2) (15). They connect into a deep and superficial venous system. Deep venous drainage occurs through the subependymal veins, internal cerebral veins, basal vein, and the great vein of Galen, which connect into the straight sinus beneath the brain. Superficial drainage occurs through cortical veins in the pia mater that drain into the dural sinuses. The venous system ultimately drains into the jugular veins or pt...

Gene therapy has emerged as an alternative for the treatment of diseases refractory to conventional therapeutics. Synthetic nanoparticle-based gene delivery systems offer highly tunable platforms for the delivery of therapeutic genes. However, the inability to achieve sustained, high-level transgene expression in vivo presents a significant hurdle. The respiratory system, although readily accessible, remains a challenging target, as effective gene therapy mandates colloidal stability in physiological fluids and the ability to overcome biological barriers found in the lung. We formulated highly stable DNA nanoparticles based on state-of-theart biodegradable polymers, poly(β-amino esters) (PBAEs), possessing a dense corona of polyethylene glycol. We found that these nanoparticles efficiently penetrated the nanoporous and highly adhesive human mucus gel layer that constitutes a primary barrier to reaching the underlying epithelium. We also discovered that these PBAE-based mucus-penetrating DNA nanoparticles (PBAE-MPPs) provided uniform and high-level transgene expression throughout the mouse lungs, superior to several gold standard gene delivery systems. PBAE-MPPs achieved robust transgene expression over at least 4 mo following a single administration, and their transfection efficiency was not attenuated by repeated administrations, underscoring their clinical relevance. Importantly, PBAE-MPPs demonstrated a favorable safety profile with no signs of toxicity following intratracheal administration.lung gene therapy | mucus-penetrating particles | nanotechnology | biodegradable polymer | nonviral gene delivery

Gene delivery to the central nervous system (CNS) has potential as a means for treating numerous debilitating neurological diseases. Non-viral gene vector platforms are tailorable and can overcome key limitations intrinsic to virus-mediated delivery; however, lack of clinical efficacy with non-viral systems to date may be attributed to limited gene vector dispersion and transfection in vivo. We show that the brain extracellular matrix strongly limits penetration of polymer-based gene vector nanoparticles through the brain parenchyma, even when they are very small (<60 nm) and coated with a polyethylene glycol (PEG) corona of typical density. Following convection enhanced delivery (CED), these “conventional gene vectors” were confined to the injection site, presumably by adhesive interactions with the brain extracellular matrix, and did not provide gene expression beyond the point of administration. In contrast, we found that incorporating highly PEGylated polymers allowed production of compacted (~43 nm) and colloidally stable DNA nanoparticles that avoided adhesive trapping within the brain parenchyma. When administered by CED into the rat striatum, highly PEGylated DNA nanoparticles distributed throughout and provided broad transgene expression without vector-induced toxicity. The use of these “brain-penetrating gene vectors”, in conjunction with CED, offers an avenue to improve gene therapy for CNS diseases.

The present study confirms the existence of a new association that we termed 3PAs. It is due mostly to germline SDHx defects, although sporadic cases of 3PAs without SDHx defects also exist. Using Sdhb(+/-) mice, we provide evidence that pituitary hyperplasia in SDHx-deficient cells may be the initial abnormality in the cascade of events leading to PA formation.

Therapies capable of decelerating, or perhaps even halting, neurodegeneration in Parkinson’s disease (PD) remain elusive. Clinical trials of PD gene therapy testing the delivery of neurotrophic factors, such as the glial cell-line derived neurotrophic factor (GDNF), have been largely ineffective due to poor vector distribution throughout the diseased regions in the brain. In addition, current delivery strategies involve invasive procedures that obviate the inclusion of early stage patients who are most likely to benefit from GDNF-based gene therapy. Here, we introduce a two-pronged treatment strategy, composed of MR image-guided focused ultrasound (FUS) and brain-penetrating nanoparticles (BPN), that provides widespread but targeted GDNF transgene expression in the brain following systemic administration. MR image-guided FUS allows circulating gene vectors to partition into the brain tissue by noninvasive and transient opening of the blood–brain barrier (BBB) within the areas where FUS is applied. Once beyond the BBB, BPN provide widespread and uniform GDNF expression throughout the targeted brain tissue. After only a single treatment, our strategy led to therapeutically relevant levels of GDNF protein content in the FUS-targeted regions in the striatum of the 6-OHDA-induced rat model of PD, which lasted at least up to 10 weeks. Importantly, our strategy restored both dopamine levels and dopaminergic neuron density and reversed behavioral indicators of PD-associated motor dysfunction with no evidence of local or systemic toxicity. Our combinatorial approach overcomes limitations of current delivery strategies, thereby potentially providing a novel means to treat PD.

Gene therapy holds promise for the treatment of many pathologies of the central nervous system (CNS), including brain tumors and neurodegenerative diseases. However, the delivery of systemically administered gene carriers to the CNS is hindered by both the blood-brain barrier (BBB) and the nanoporous and electrostatically charged brain extracelluar matrix (ECM), which acts as a steric and adhesive barrier. We have previously shown that these physiological barriers may be overcome by, respectively, opening the BBB with MR image-guided focused ultrasound (FUS) and microbubbles and using highly compact “brain penetrating” nanoparticles (BPN) coated with a dense polyethylene glycol corona that prevents adhesion to ECM components. Here, we tested whether this combined approach could be utilized to deliver systemically administered DNA-bearing BPN (DNA-BPN) across the BBB and mediate localized, robust, and sustained transgene expression in the rat brain. Systemically administered DNA-BPN delivered through the BBB with FUS led to dose-dependent transgene expression only in the FUS-treated region that was evident as early as 24 h post administration and lasted for at least 28 days. In the FUS-treated region ~42% of all cells, including neurons and astrocytes, were transfected, while less than 6% were transfected in the contralateral non-FUS treated hemisphere. Importantly, this was achieved without any sign of toxicity or astrocyte activation. We conclude that the image-guided delivery of DNA-BPN with FUS and microbubbles constitutes a safe and non-invasive strategy for targeted gene therapy to the brain.

Glioblastoma multiforme (GBM) is highly invasive and uniformly fatal, with median survival < 20 months after diagnosis even with the most aggressive treatment that includes surgery, radiation, and systemic chemotherapy. Cisplatin is a particularly potent chemotherapeutic agent, but its use to treat GBM is limited by severe systemic toxicity and inefficient penetration of brain tumor tissue even when it is placed directly in the brain within standard delivery systems. We describe the development of cisplatin-loaded nanoparticles that are small enough (70 nm in diameter) to move within the porous extracellular matrix between cells and that possess a dense polyethylene glycol (PEG) corona that prevents them from being trapped by adhesion as they move through the brain tumor parenchyma. As a result, these “brain penetrating nanoparticles” penetrate much deeper into brain tumor tissue compared to nanoparticles without a dense PEG corona following local administration by either manual injection or convection enhanced delivery. The nanoparticles also provide controlled release of cisplatin in effective concentrations to kill the tumor cells that they reach without causing toxicity-related deaths that were observed when cisplatin was infused into the brain without a delivery system. Median survival time of rats bearing orthotopic glioma was significantly enhanced when cisplatin was delivered in brain penetrating nano-particles (median survival not reached; 80% long-term survivors) compared to cisplatin in conventional un-PEGylated particles (median survival = 40 days), cisplatin alone (median survival = 12 days) or saline-treated controls (median survival = 28 days).

A major limitation in the treatment of glioblastoma (GBM), the most common and deadly primary brain cancer, is delivery of therapeutics to invading tumor cells outside of the area that is safe for surgical removal. A promising way to target invading GBM cells is via drug-loaded nanoparticles that bind to fibroblast growth factor-inducible 14 (Fn14), thereby potentially improving efficacy and reducing toxicity. However, achieving broad particle distribution and nanoparticle targeting within the brain remains a significant challenge due to the adhesive extracellular matrix (ECM) and clearance mechanisms in the brain. In this work, we developed Fn14 monoclonal antibody-decorated nanoparticles that can efficiently penetrate brain tissue. We show these Fn14-targeted brain tissue penetrating nanoparticles are able to (i) selectively bind to recombinant Fn14 but not brain ECM proteins, (ii) associate with and be internalized by Fn14-positive GBM cells, and (iii) diffuse within brain tissue in a manner similar to non-targeted brain penetrating nanoparticles. In addition, when administered intracranially, Fn14-targeted nanoparticles showed improved tumor cell co-localization in mice bearing human GBM xenografts compared to non-targeted nanoparticles. Minimizing non-specific binding of targeted nanoparticles in the brain may greatly improve the access of particulate delivery systems to remote brain tumor cells and other brain targets.