Young CSF restores oligodendrogenesis and memory in aged mice via Fgf17.

Recent understanding of how the systemic environment shapes the brain throughout life has led to numerous intervention strategies to slow brain ageing1-3. Cerebrospinal fluid (CSF) makes up the immediate environment of brain cells, providing them with nourishing compounds4,5. We discovered that infusing young CSF directly into aged brains improves memory function. Unbiased transcriptome analysis of the hippocampus identified oligodendrocytes to be most responsive to this rejuvenated CSF environment. We further showed that young CSF boosts oligodendrocyte progenitor cell (OPC) proliferation and differentiation in the aged hippocampus and in primary OPC cultures. Using SLAMseq to metabolically label nascent mRNA, we identified serum response factor (SRF), a transcription factor that drives actin cytoskeleton rearrangement, as a mediator of OPC proliferation following exposure to young CSF. With age, SRF expression decreases in hippocampal OPCs, and the pathway is induced by acute injection with young CSF. We screened for potential SRF activators in CSF and found that fibroblast growth factor 17 (Fgf17) infusion is sufficient to induce OPC proliferation and long-term memory consolidation in aged mice while Fgf17 blockade impairs cognition in young mice. These findings demonstrate the rejuvenating power of young CSF and identify Fgf17 as a key target to restore oligodendrocyte function in the ageing brain.

Small molecule C381 targets the lysosome to reduce inflammation and ameliorate disease in models of neurodegeneration.

SignificanceNeurodegenerative diseases are poorly understood and difficult to treat. One common hallmark is lysosomal dysfunction leading to the accumulation of aggregates and other undegradable materials, which cause damage to brain resident cells. Lysosomes are acidic organelles responsible for breaking down biomolecules and recycling their constitutive parts. In this work, we find that the antiinflammatory and neuroprotective compound, discovered via a phenotypic screen, imparts its beneficial effects by targeting the lysosome and restoring its function. This is established using a genome-wide CRISPRi target identification screen and then confirmed using a variety of lysosome-targeted studies. The resulting small molecule from this study represents a potential treatment for neurodegenerative diseases as well as a research tool for the study of lysosomes in disease.

Exercise plasma boosts memory and dampens brain inflammation via clusterin.

Physical exercise is generally beneficial to all aspects of human and animal health, slowing cognitive ageing and neurodegeneration1. The cognitive benefits of physical exercise are tied to an increased plasticity and reduced inflammation within the hippocampus2-4, yet little is known about the factors and mechanisms that mediate these effects. Here we show that 'runner plasma', collected from voluntarily running mice and infused into sedentary mice, reduces baseline neuroinflammatory gene expression and experimentally induced brain inflammation. Plasma proteomic analysis revealed a concerted increase in complement cascade inhibitors including clusterin (CLU). Intravenously injected CLU binds to brain endothelial cells and reduces neuroinflammatory gene expression in a mouse model of acute brain inflammation and a mouse model of Alzheimer's disease. Patients with cognitive impairment who participated in structured exercise for 6 months had higher plasma levels of CLU. These findings demonstrate the existence of anti-inflammatory exercise factors that are transferrable, target the cerebrovasculature and benefit the brain, and are present in humans who engage in exercise.

Acute and late administration of colony stimulating factor 1 attenuates chronic cognitive impairment following mild traumatic brain injury in mice.

Traumatic brain injury (TBI) is a leading cause of long-term neurological disability. Currently there is no effective pharmacological treatment for patients suffering from the long-lasting symptoms of TBI. We recently discovered that colony stimulating factor 1 (CSF1), an essential regulator of macrophage homeostasis, is neuroprotective and reduces neuroinflammation in two models of neurological disease in mice. Here we used a mouse model of repetitive mild TBI (mTBI) to examine whether CSF1 would attenuate cognitive deficits and improve pathological outcomes in two paradigms. In the acute paradigm, a single bolus treatment of CSF1 administered 24 h after injury significantly reduces memory impairment and astrocyte reactivity assessed 3 months later. In the chronic paradigm, the mice were tested 3 months after mTBI when they showed cognitive deficits. The mice were then randomly assigned to receive CSF1 or PBS (as control) treatment. After one month of treatment, the PBS-treated mice remained cognitively impaired, but the CSF1-treated showed significant improvements in cognitive function. RNA-seq and Ingenuity Pathway Analysis reveals CSF1 treatment alters cognition- and memory-related transcriptomic changes and pathways. The results of this study show that acute as well as delayed CSF1 treatment attenuate chronically impaired cognitive functions and improve pathological outcomes long after mTBI. The wide therapeutic time window of CSF1, together with the fact that CSF1 is approved for human use in clinical trials, strongly supports the potential clinical usefulness of this treatment in patients with mTBI.