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Biology subjects

Stewart, C. L.

Publications and source records attributed to Stewart, C. L..

5 recordsLinked to original sources

Organ-specific fibroblast dynamics revealed via an integrated experimental-computational framework

Fibrosis is a progressive pathological process driven by dysregulated fibroblast activity and excessive extracellular matrix deposition, leading to scarring, functional decline and eventually organ failure. Although fibroblasts are key mediators of fibrotic remodelling, it remains unclear whether their behaviours are conserved across tissues or organ specific. Here, we combine experimental and computational approaches to dissect fibroblast dynamics underlying cardiac and pulmonary fibrosis. Using in vitro assays, we demonstrate that cardiac and lung fibroblasts differ in morphology, proliferation, and collagen matrix organisation, likely reflecting tissue-specific mechanical and biochemical demands. Lung fibroblasts display higher proliferative capacity and increased myofibroblast activation, forming condition-dependent collagen architectures, with fibres that are more aligned under proinflammatory and fibrotic conditions, but less so under anti-inflammatory conditions. In contrast, cardiac fibroblasts consistently generate diffuse, isotropic collagen matrices across all cytokine conditions. Integrating these data into a mechanistic computational model of fibroblast-collagen interactions, we show that fibroblast motility, rather than cell-cell interactions, dominates tissue dynamics, and that coupling between motility and local collagen density regulates matrix architecture. Simulations reveal that collagen-dependent motility and density-dependent collagen secretion prevent maladaptive matrix alignment, identifying potential mechanisms restraining fibrotic progression. Our findings uncover organ-specific fibroblast behaviours and highlight how integrating experimental and computational frameworks can illuminate the dynamic rules governing fibrosis and inform targeted antifibrotic strategies.

cell biology↗

Single-Cell Atlas of Dorsal Root Ganglion Remodeling After Neuroma-Forming Nerve Injury Reveals Intervention-Specific Glial and Immune Programs

Peripheral nerve injury, whether caused by a cut, crush, or excessive stretch, can cause disordered regeneration and formation of a painful neuroma at the injury site. Regrowing axons may end in a swelling, hypersensitive nerve stump, producing pain along the affected nerve distribution that may outweigh sensory or motor deficits. Although neuromas are common, treatment outcomes are inconsistent and the mechanisms that initiate and sustain neuroma-associated pain remain poorly defined. Many surgical and non-surgical approaches (excision with transposition, capping, sclerosis, cryoablation) are used, yet comparative studies have not identified a superior technique, highlighting biological heterogeneity and knowledge gaps. A proximal nerve crush (axonotmetic injury) performed upstream of a neuroma or transection is proposed to reshape axonal growth and interrupt retrograde injury signaling, potentially shifting the system toward a more regenerative, pain-resolving state. However, how proximal crush remodels long-term programs in the dorsal root ganglion (DRG), and how these changes relate to neuroma-like outcomes, are unclear. Here, we build a single-cell atlas of DRG remodeling after neuroma-forming injury and compare it with two interventions- proximal nerve crush and nerve resection, using scRNA-seq. By resolving transcriptional responses across sensory neurons, satellite glial cells, Schwann cells, and macrophages, we identify intervention-specific glial and immune programs that distinguish permissive regeneration from persistent, pain-associated states and nominate pathways for mechanism-guided neuroma therapies.

neuroscience↗

Partial or complete loss of norepinephrine differentially alters contextual fear and catecholamine release dynamics in hippocampal CA1

Contextual fear learning is heavily dependent on the hippocampus. Despite evidence that catecholamines contribute to contextual encoding and memory retrieval, the precise temporal dynamics of their release in the hippocampus during behavior is unknown. In addition, new animal models are required to probe the effects of altered catecholamine synthesis on release dynamics and contextual learning. Utilizing GRABNE and GRABDA sensors, in vivo fiber photometry, and two new mouse models of altered locus coeruleus norepinephrine (LC-NE) synthesis, we investigate norepinephrine (NE) and dopamine (DA) release dynamics in dorsal hippocampal CA1 during contextual fear conditioning. We report that aversive foot-shock increases both NE and DA release in dorsal CA1, while freezing behavior associated with recall of fear memory is accompanied by decreased release. Partial loss of LC-NE synthesis reveals that NE release dynamics are modulated by sex. Moreover, we find that recall of recent fear memory is sensitive to both partial and complete loss of LC-NE synthesis throughout prenatal and postnatal development, similar to prior observations of mice with global loss of NE synthesis beginning postnatally. In contrast, remote recall is compromised only by complete loss of LC-NE synthesis beginning prenatally. Overall, these findings provide novel insights into the role of NE in contextual fear and the precise temporal dynamics of both NE and DA during freezing behavior, and highlight a complex relationship between genotype, sex, and NE signaling.

neuroscience↗

Synergistic Combined-proteomics Guided Mapping strategy identifies mTOR mediated phosphorylation of LARP1 in nutrient responsiveness and dilated cardiomyopathy

Increased activity of the mammalian target of rapamycin (mTOR) signalling pathway, a crucial nutrient sensor, exacerbates ageing and ageing-related diseases, including cancer and heart failure. To further elucidate the physiological role of the serine/threonine kinase mTOR, we devised a novel tractable proteomics strategy that combines interaction proteomics, proximity-based proteomics and quantitative phosphoproteomics to identify interactors with and potential substrates of mTOR. We identified 58 candidate mTOR substrates, several of which were further validated. Interestingly, several of these candidate mTOR substrates are involved in various aspects of RNA biology, including regulating stability and processing. We characterized in-depth one of the validated mTOR substrates, LARP1, an RNA binding protein. mTOR-dependent phosphorylation of LARP1 is nutrient-sensitive and controls the RNA-binding ability of LARP1. We show that mTOR activity and LARP1 and LARP1 phosphorylation levels are increased in a congenital mouse model of dilated cardiomyopathy (DCM) caused by a mutation in the Lamin A gene. This implicates LARP1 in the development of DCM.

molecular biology↗

Human AKTIP interacts with ESCRT proteins and functions at the midbody in cytokinesis

To complete mitosis, the intercellular bridge that links daughter cells needs to be cleaved. This abscission step is carried out by the sequential recruitment of ESCRT proteins at the midbody. We report here that a new factor, named AKTIP, works in association with ESCRTs. We find that AKTIP binds to the ESCRT I subunit VPS28, and show by high resolution microscopy that AKTIP forms a ring in the dark zone of the intercellular bridge. This ring is positioned in between the circular structures formed by ESCRTs type III. Functionally, we observe that the reduction of AKTIP impinges on the recruitment of the ESCRT III member IST1 at the midbody and causes abscission defects. Taken together, these data indicate that AKTIP is a new factor that contributes to the formation of the ESCRT complex at the midbody and is implicated in the performance of the ESCRT machinery during cytokinetic abscission.

cell biology↗