ORCID Profile
0000-0002-3102-3614
Current Organisation
University of Tasmania
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Publisher: Elsevier BV
Date: 03-2023
Publisher: Wiley
Date: 11-06-2023
DOI: 10.1002/GLIA.24208
Publisher: Wiley
Date: 30-03-2023
DOI: 10.1002/GLIA.24371
Abstract: Cerebral blood flow (CBF) is important for the maintenance of brain function and its dysregulation has been implicated in Alzheimer's disease (AD). Microglia associations with capillaries suggest they may play a role in the regulation of CBF or the blood–brain‐barrier (BBB). We explored the relationship between microglia and pericytes, a vessel‐resident cell type that has a major role in the control of CBF and maintenance of the BBB, discovering a spatially distinct subset of microglia that closely associate with pericytes. We termed these pericyte‐associated microglia (PEM). PEM are present throughout the brain and spinal cord in NG2DsRed × CX 3 CR1 +/GFP mice, and in the human frontal cortex. Using in vivo two‐photon microscopy, we found microglia residing adjacent to pericytes at all levels of the capillary tree and found they can maintain their position for at least 28 days. PEM can associate with pericytes lacking astroglial endfeet coverage and capillary vessel width is increased beneath pericytes with or without an associated PEM, but capillary width decreases if a pericyte loses a PEM. Deletion of the microglia fractalkine receptor (CX 3 CR1) did not disrupt the association between pericytes and PEM. Finally, we found the proportion of microglia that are PEM declines in the superior frontal gyrus in AD. In summary, we identify microglia that specifically associate with pericytes and find these are reduced in number in AD, which may be a novel mechanism contributing to vascular dysfunction in neurodegenerative diseases.
Publisher: Cold Spring Harbor Laboratory
Date: 10-2023
Publisher: Cold Spring Harbor Laboratory
Date: 12-11-2021
DOI: 10.1101/2021.11.11.467877
Abstract: Neurons live for the lifespan of the in idual and underlie our ability for lifelong learning and memory. However, aging alters neuron morphology and function resulting in age-related cognitive decline. It is well established that epigenetic alterations are essential for learning and memory, yet few neuron-specific genome-wide epigenetic maps exist into old age. Comprehensive mapping of H3K4me3 and H3K27ac in mouse neurons across lifespan revealed plastic H3K4me3 marking that differentiates neuronal age linked to known characteristics of cellular and neuronal aging. We determined that neurons in old age recapitulate the H3K27ac enrichment at promoters, enhancers and super enhancers from young adult neurons, likely representing a re-activation of pathways to maintain neuronal output. Finally, this study identified new characteristics of neuronal aging, including altered rDNA regulation and epigenetic regulatory mechanisms. Collectively, these findings indicate a key role for epigenetic regulation in neurons, that is inextricably linked with aging.
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.TAAP.2022.116025
Abstract: Capillary pericytes have numerous functions important for tissue maintenance. Changes in pericyte function are implicated in diseases such as cancer, where pericyte-mediated angiogenesis contributes to the blood supply that tumors use to survive. Some anti-cancer agents, like imatinib, target platelet-derived growth factor receptor-beta (PDGFRβ). Healthy pericytes rely on PDGFRβ phosphorylation for their survival. Therefore, we hypothesised that pharmacological agents that block PDGFRβ phosphorylation could be used to kill pericytes. We treated human brain vascular pericytes, which express PDGFRβ, with three receptor tyrosine kinase inhibitors: imatinib, sunitinib and orantinib. Imatinib and sunitinib, but not orantinib, inhibited PDGFRβ phosphorylation in pericytes. Imatinib and sunitinib also reduced viability, prevented proliferation, and induced death, while orantinib only blocked pericyte proliferation. Overall, we found that receptor tyrosine kinase inhibitors that block PDGFRβ phosphorylation cause healthy pericytes to die in vitro. While useful in cancer to limit tumor growth, these agents could impair healthy brain pericyte survival and impact brain function.
Publisher: Cold Spring Harbor Laboratory
Date: 11-08-2022
DOI: 10.1101/2022.08.08.503250
Abstract: Cerebral blood flow is important for the maintenance of brain function and its dysregulation has been implicated in Alzheimer’s disease (AD). Subpopulations of microglia have well-characterised associations with the vasculature in the central nervous system but the precise relationship between microglia and cells which exist on the vasculature is not yet clear. In this study we explored the relationship between microglia and pericytes, a vessel-resident cell type that has a major role in the regulation of cerebral blood flow and maintenance of the blood brain barrier. Using fixed tissue sections and in vivo live imaging, we discovered a subset of microglia that closely associated with pericytes, termed PE ricyte-associated M icroglia (PEM). PEM are present throughout all regions of the brain and spinal cord in NG2DsRed x CX 3 CR1 +/GFP mice, and in the human frontal cortex. They reside adjacent to pericytes at all levels of the capillary tree and can maintain their position for at least 28 days. PEM associate with pericytes lacking astroglial endfeet coverage but are segregated from pericytes by capillary basement membranes and capillary vessel width is similarly increased beneath pericytes with or without an associated PEM. Deletion of the microglia fractalkine receptor (CX 3 CR1) did not disrupt the association between pericytes and PEM, suggesting the association is not reliant on fractalkine signalling. Finally, we found that the proportion of microglia that are capillary-associated and PEM declines in the superior frontal gyrus (SFG) in AD, which is exacerbated by the APOE ε3/ε4 genotype. In summary, we identify and characterise a subpopulation of microglia that specifically associate with pericytes and find this population is reduced in the SFG in AD. This reduction may be a novel mechanism contributing to vascular dysfunction in diseases such as AD.
No related grants have been discovered for Jake Cashion.