Biology subjects

Fawcett, J. W.

Publications and source records attributed to Fawcett, J. W..

7 recordsLinked to original sources

bioRxiv2026

4-Methylumbelliferone Restores Age-Related Changes in Perineuronal Nets, Memory and Neuroinflammation

Aging leads to cognitive decline due to reduced neuronal plasticity and increased brain inflammation. Disruption of perineuronal nets (PNNs) is a recognized strategy to enhance neuroplasticity. Hyaluronan forms the backbone of PNNs, and 4-methylumbelliferone (4-MU), an inhibitor of hyaluronan synthesis, has been proposed to disrupt PNNs and enhance neuroplasticity in young rodents. In addition, 4-MU is also known as an immune response regulator, although its effects within the central nervous system (CNS) have been less characterized. In this study, we investigated the impact of long-term oral 4-MU administration in aged mice (20-22 months old), focusing on PNNs intensity, memory, and neuroinflammation. PNN intensity increased with age, and 4-MU treatment reduced it in 22-month-old mice to levels observed in 10-month-old animals; in the novel object recognition test, treated 22-month-old mice performed comparably to or better than 10-month-old controls. Moreover, markers of aging-associated neuroinflammation--including astrocytic and microglial activation as well as peripheral immune cell infiltration--were normalized to 10-month-old levels or further diminished following 4-MU treatment. Importantly, chronic 4-MU administration was well tolerated in aged mice, with no serious adverse effects observed. Together, these results suggest that 4-MU mitigates PNNs accumulation and neuroinflammaging while enhancing recognition memory, supporting its potential as a safe therapeutic approach for age-related cognitive decline.

neuroscience↗

bioRxiv2026

Chondroitin 4-sulphate depletion enhances synaptic plasticity and memory in aging

Perineuronal nets (PNNs), specialised extracellular matrix structures enriched in chondroitin sulphate proteoglycans (CSPGs), are key regulators of synaptic plasticity, learning, and memory. Aging is characterised by a shift in chondroitin sulphate composition toward increased chondroitin-4-sulfation (C4S) and reduced C6S, a pattern associated with declining cognitive flexibility. Here, we investigated how selective reduction of C4S affects PNN structure, PV-interneuron connectivity, and cognitive performance across the lifespan. Conditional deletion of the C4-sulfotransferase Chst11 markedly reduced C4S levels and diminished dendritic PNN complexity while preserving somatic PNN structure. This partial destabilisation of PNNs increased excitatory synaptic input onto PV interneurons in both young and aged mice, without major alterations in basal hippocampal transmission or long-term potentiation. Behaviourally, Chst11 knockout mice showed robust and persistent protection against age-related cognitive decline. Working memory performance remained stable across aging, short-term spatial memory was enhanced from early adulthood onward, and object recognition memory was significantly prolonged at all retention delays, even in old age. Sociability and social novelty preference were also preserved longer in aging knockouts compared with controls. These improvements occurred despite an overall preservation of PNN architecture, indicating that modifying sulphation rather than removing CSPGs is sufficient to enhance plasticity. Our findings demonstrate that reducing C4S through Chst11 deletion confers long-lasting enhancements in cognitive function and mitigates aging-related decline. Targeting CS-GAG sulphation patterns may therefore represent a promising strategy for maintaining cognitive resilience and restoring plasticity in aging or neurodegenerative conditions.

neuroscience↗

bioRxiv2023

Hyperactive PI3Kinase delta enables long distance regeneration of the rat corticospinal tract

Maturation of central nervous system neurons leads to loss of their intrinsic regeneration potential. In particular after injury of the adult spinal cord there is minimal regeneration of corticospinal axons, which control gait and fine movement. Previous work has shown that knockdown of PTEN to increase PIP3 levels can promote regeneration in young animals, but the effect is much less in adults probably due to low PIP3 production. Here, we have transduced sensorimotor cortex neurons with a hyperactive form of PI3K, PI3K{delta}, which increases PIP3 in mature neurons. This enables cortical neurons to regenerate corticospinal axons and improve behavioural outcomes. We used a C4 dorsal column lesion model in adult rats and injected the right motor cortex at 4 sites concurrently with a mixture AAV1-PIK3CD and AAV1-eGFP or titre matched AAV1-eGFP only. We allowed rats to survive for 6, 9, 12 or 16 weeks. Immunostaining showed 70 - 80% co-expression in cortical neurons which remained stable at both 12 and 16 weeks. We counted GFP labelled axons in 20 m spinal cord sections. In PI3KCD-treated animals many axons were seen to have regenerated around the margins of lesions, collecting into a knot of axons with the typical appearance of regeneration at the caudal end. Tracing down the cord, and excluding axons and neurites that could have come from unlesioned ventral CST, we found axons extending up to 1 cm below lesions, numbers decreasing with distance from the lesion. After 16 weeks there were circa 200 axons at the caudal end of lesions with a regeneration index of 0.2, with half this number at 12 weeks. Behavioural testing for 16 weeks revealed functional improvements in skilled paw reaching, grip strength and ladder rung walking in rats treated with PIK3CD compared to GFP only controls. In addition to behavioural testing, functional recovery of PIK3CD treated rats was confirmed with electrophysiological recordings during which we stimulated the right pyramid. Cord dorsum potentials (CDPs) above and below lesion and EMG forepaw distal flexor muscles showed greatly increased connectivity compared with GFP only controls, lesion only controls and uninjured shams. We conclude that forcing upregulation of PI3K{delta} in cortical neurons leads to robust regeneration after spinal cord injury that results in functional restoration.

neuroscience↗

bioRxiv2020

Immunochemical analysis of the integrin expression in retinal pigment epithelial cells

Retinal pigment epithelial (RPE) cells have been used in disease modelling and transplantation studies in retinal diseases. Several types of RPE cells have been trialed, ranging from primary cells and immortalized cell lines to stem cell-derived RPE cells. During aging and in disease, the extracellular environment of the RPE cells changes, interfering with RPE cell adhesion. We hypothesize that this could be a key problem in transplantation studies that have reported lack of adhesion and survival of the transplanted RPE cells. Integrins are essential for the proper function of the RPE, mediating adhesion to Bruchs membrane, and the binding and subsequent phagocytosis of photoreceptor outer segments. Variability that has been found in clinical trials might be due to the variability of cell types used and their expression profiles of surface molecules. Here, we set out to analyze integrin expression in primary rat RPE cells and in the human cell line ARPE-19 using immunochemistry. We found that both cell types express integrins to varying degrees. After long-term culturing, ARPE-19 cells resemble mature RPE cells, and increase integrin expression. We hence argue that it is important to test the properties of these cells prior to transplantation to avoid failure of adhesion and to facilitate correct function.

neuroscience↗

bioRxiv2020

Protrudin functions as a scaffold in the endoplasmic reticulum to support axon regeneration in the adult central nervous system

Adult mammalian central nervous system axons have intrinsically poor regenerative capacity, so axonal injury has permanent consequences. One approach to enhancing regeneration is to increase the axonal supply of growth molecules and organelles. We achieved this by expressing the adaptor molecule Protrudin which is normally found at low levels in non-regenerative neurons. Elevated Protrudin expression enabled robust central nervous system regeneration both in vitro in primary cortical neurons and in vivo in the injured adult optic nerve. Protrudin overexpression facilitated the accumulation of endoplasmic reticulum, integrins and Rab11 endosomes in the distal axon, whilst removing Protrudins endoplasmic reticulum localization, kinesin-binding or phosphoinositide-binding properties abrogated the regenerative effects. These results demonstrate that Protrudin promotes regeneration by functioning as a scaffold to link axonal organelles, motors and membranes, establishing important roles for these cellular components in mediating regeneration in the adult central nervous system.

neuroscience↗

bioRxiv2019

Mechanical matching of implant to host minimises foreign body reaction

Medical implants offer a unique and powerful therapeutic approach in many areas of medicine. However, their lifetime is often limited as they may cause a foreign body reaction (FBR) leading to their encapsulation by scar tissue1-4. Despite the importance of this process, how cells recognise implanted materials is still poorly understood5, 6. Here, we show how the mechanical mismatch between implants and host tissue leads to FBR. Fibroblasts and macrophages, which are both crucially involved in mediating FBR, became activated when cultured on materials just above the stiffness of healthy tissue. Coating stiff implants with a thin layer of hydrogel or silicone with a tissue-like elastic modulus ([~]20 kPa in subcutaneous and [~]2 kPa in peripheral nerve implants) or softer significantly reduced inflammation and fibrosis three months after implantation. Materials stiffer than the host tissue led to nuclear localisation of the mechanosensitive transcriptional regulator YAP in neighbouring cells in vivo, confirming mechanotransduction. The alleviation of FBR by soft coatings not exceeding the stiffness of the host tissue provides a strategy to achieve long-term implant stability without extensive modification of current implant manufacturing techniques, facilitating clinical translation.

bioengineering↗

bioRxiv2019

PI 3-kinase delta enhances axonal PIP3 to support axon regeneration in the adult CNS

Peripheral nervous system (PNS) neurons support axon regeneration into adulthood, whereas central nervous system (CNS) neurons lose regenerative ability after development. To better understand this decline whilst aiming to improve regeneration, we focused on phosphoinositide 3-kinase (PI3K) and its product phosphatidylinositol(3,4,5)-trisphosphate (PIP3). We found that neuronal PIP3 decreases with maturity in line with regenerative competence, firstly in the cell body and subsequently in the axon. We show that adult PNS neurons utilise two catalytic subunits of PI3K for efficient regeneration: p110 and p110{delta}. Overexpressing p110 in CNS neurons had no effect, however expression of p110{delta} restored axonal PIP3 and enhanced CNS regeneration in rat and human neurons and in transgenic mice, functioning in the same way as the hyperactivating H1047R mutation of p110. Furthermore, viral delivery of p110{delta} promoted robust regeneration after optic nerve injury. These findings demonstrate a deficit of axonal PIP3 as a reason for intrinsic regeneration failure and show that native p110{delta} facilitates axon regeneration by functioning in a hyperactive fashion.

neuroscience↗