CNS fibroblasts form a fibrotic scar in response to immune cell infiltration.

Fibrosis is a common pathological response to inflammation in many peripheral tissues and can prevent tissue regeneration and repair. Here, we identified persistent fibrotic scarring in the CNS following immune cell infiltration in the experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis. Using lineage tracing and single-cell sequencing in EAE, we determined that the majority of the fibrotic scar is derived from proliferative CNS fibroblasts, not pericytes or infiltrating bone marrow-derived cells. Ablating proliferating fibrotic cells using cell-specific expression of herpes thymidine kinase led to an increase in oligodendrocyte lineage cells within the inflammatory lesions and a reduction in motor disability. We further identified that interferon-gamma pathway genes are enriched in CNS fibrotic cells, and the fibrotic cell-specific deletion of Ifngr1 resulted in reduced fibrotic scarring in EAE. These data delineate a framework for understanding the CNS fibrotic response.

Neuronal Activity Regulates Blood-Brain Barrier Efflux Transport through Endothelial Circadian Genes.

The blood vessels in the central nervous system (CNS) have a series of unique properties, termed the blood-brain barrier (BBB), which stringently regulate the entry of molecules into the brain, thus maintaining proper brain homeostasis. We sought to understand whether neuronal activity could regulate BBB properties. Using both chemogenetics and a volitional behavior paradigm, we identified a core set of brain endothelial genes whose expression is regulated by neuronal activity. In particular, neuronal activity regulates BBB efflux transporter expression and function, which is critical for excluding many small lipophilic molecules from the brain parenchyma. Furthermore, we found that neuronal activity regulates the expression of circadian clock genes within brain endothelial cells, which in turn mediate the activity-dependent control of BBB efflux transport. These results have important clinical implications for CNS drug delivery and clearance of CNS waste products, including Aß, and for understanding how neuronal activity can modulate diurnal processes.

Microcornea, Posterior Megalolenticonus, Persistent Fetal Vasculature, and Coloboma Syndrome Associated With a New Mutation in ZNF408.

The authors report a case of a 6-week-old girl with microphthalmia, posterior lenticonus, persistent fetal vasculature, and coloboma of the right eye, with morning glory disc anomaly and falciform retinal folds of the left eye. Genetic testing revealed a previously unreported mutation (c.1471A>G [p.T491A]) in the gene ZNF408, which has been associated with autosomal recessive retinitis pigmentosa and autosomal dominant familial exudative vitreoretinopathy. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:253-256.].

High-fidelity reproduction of spatiotemporal visual signals for retinal prosthesis.

Natural vision relies on spatiotemporal patterns of electrical activity in the retina. We investigated the feasibility of veridically reproducing such patterns with epiretinal prostheses. Multielectrode recordings and visual and electrical stimulation were performed on populations of identified ganglion cells in isolated peripheral primate retina. Electrical stimulation patterns were designed to reproduce recorded waves of activity elicited by a moving visual stimulus. Electrical responses in populations of ON parasol cells exhibited high spatial and temporal precision, matching or exceeding the precision of visual responses measured in the same cells. Computational readout of electrical and visual responses produced similar estimates of stimulus speed, confirming the fidelity of electrical stimulation for biologically relevant visual signals. These results suggest the possibility of producing rich spatiotemporal patterns of retinal activity with a prosthesis and that temporal multiplexing may aid in reproducing the neural code of the retina.

MicroRNAs are exported from malignant cells in customized particles.

MicroRNAs (miRNAs) are released from cells in association with proteins or microvesicles. We previously reported that malignant transformation changes the assortment of released miRNAs by affecting whether a particular miRNA species is released or retained by the cell. How this selectivity occurs is unclear. Here we report that selectively exported miRNAs, whose release is increased in malignant cells, are packaged in structures that are different from those that carry neutrally released miRNAs (n-miRNAs), whose release is not affected by malignancy. By separating breast cancer cell microvesicles, we find that selectively released miRNAs associate with exosomes and nucleosomes. However, n-miRNAs of breast cancer cells associate with unconventional exosomes, which are larger than conventional exosomes and enriched in CD44, a protein relevant to breast cancer metastasis. Based on their large size, we call these vesicles L-exosomes. Contrary to the distribution of miRNAs among different microvesicles of breast cancer cells, normal cells release all measured miRNAs in a single type of vesicle. Our results suggest that malignant transformation alters the pathways through which specific miRNAs are exported from cells. These changes in the particles and their miRNA cargo could be used to detect the presence of malignant cells in the body.