Astrocytes and pericytes attenuate severely injured patient plasma mediated expression of tight junction proteins in endothelial cells

Virus-Shaped Mesoporous Silica Nanostars to Improve the Transport of Drugs across the Blood-Brain Barrier

Conditions affecting the brain are the second leading cause of death globally. One of the main challenges for drugs targeting brain diseases is passing the blood-brain barrier (BBB). Here, the effectiveness of mesoporous silica nanostars (MSiNSs) with two different spike lengths to cross an in vitro BBB multicellular model was evaluated and compared to spherical nanoparticles (MSiNP). A modified sol-gel single-micelle epitaxial growth was used to produce MSiNS, which showed no cytotoxicity or immunogenicity at concentrations of up to 1 μg mL-1 in peripheral blood mononuclear and neuronal cells. The nanostar MSiNS effectively penetrated the BBB model after 24 h, and MSiNS-1 with a shorter spike length (9 ± 2 nm) crossed the in vitro BBB model more rapidly than the MSiNS-2 with longer spikes (18 ± 4 nm) or spherical MSiNP at 96 h, which accumulated in the apical and basolateral sides, respectively. Molecular dynamic simulations illustrated an increase in configurational flexibility of the lipid bilayer during contact with the MSiNS, resulting in wrapping, whereas the MSiNP suppressed membrane fluctuations. This work advances an effective brain drug delivery system based on virus-like shaped MSiNS for the treatment of different brain diseases and a mechanism for their interaction with lipid bilayers.

Involvement of Astrocytes in the Formation, Maintenance, and Function of the Blood-Brain Barrier

The blood-brain barrier (BBB) is a fundamental structure that protects the composition of the brain by determining which ions, metabolites, and nutrients are allowed to enter the brain from the blood or to leave it towards the circulation. The BBB is structurally composed of a layer of brain capillary endothelial cells (BCECs) bound to each other through tight junctions (TJs). However, its development as well as maintenance and properties are controlled by the other brain cells that contact the BCECs: pericytes, glial cells, and even neurons themselves. Astrocytes seem, in particular, to have a very important role in determining and controlling most properties of the BBB. Here, we will focus on these latter cells, since the comprehension of their roles in brain physiology has been continuously expanding, even including the ability to participate in neurotransmission and in complex functions such as learning and memory. Accordingly, pathological conditions that alter astrocytic functions can alter the BBB's integrity, thus compromising many brain activities. In this review, we will also refer to different kinds of in vitro BBB models used to study the BBB's properties, evidencing its modifications under pathological conditions.

B cell depletion modulates glial responses and enhances blood vessel integrity in a model of multiple sclerosis

Multiple sclerosis (MS) is characterized by a compromised blood-brain barrier (BBB) resulting in central nervous system (CNS) entry of peripheral lymphocytes, including T cells and B cells. While T cells have largely been considered the main contributors to neuroinflammation in MS, the success of B cell depletion therapies suggests an important role for B cells in MS pathology. Glial cells in the CNS are essential components in both disease progression and recovery, raising the possibility that they represent targets for B cell functions. Here, we examine astrocyte and microglia responses to B cell depleting treatments in an animal model of MS, experimental autoimmune encephalomyelitis (EAE). B cell depleted EAE animals had markedly reduced disease severity and myelin damage accompanied by reduced microglia and astrocyte reactivity 20 days after symptom onset. To identify potential initial mechanisms mediating functional changes following B cell depletion, astrocyte and microglia transcriptomes were analyzed 3 days following B cell depletion. In control EAE animals, transcriptomic analysis revealed astrocytic inflammatory pathways were activated and microglial influence on neuronal function were inhibited. Following B cell depletion, initial functional recovery was associated with an activation of astrocytic pathways linked with restoration of neurovascular integrity and of microglial pathways associated with neuronal function. These studies reveal an important role for B cell depletion in influencing glial function and CNS vasculature in an animal model of MS.