Biology subjects

Llewellyn, J.

Publications and source records attributed to Llewellyn, J..

14 recordsLinked to original sources

bioRxiv2026

Senescent tenocytes drive an age-associated loss of cell-extracellular matrix homeostasis, which can be partially restored using dihydroresveratrol

Tendons are commonly injured, not only in athletes, but also during normal everyday activities, particularly in older age. Tendons are rich in extracellular matrix proteins, many of which are turned over extremely slowly during an individuals lifetime. As a result, tight regulation of the extracellular matrix is essential for tendons to remain resilient to the mechanical load placed on them. However, tendons are prone to age-associated functional decline, characterised by chronic inflammation, accumulation of damaged collagen, and matrix remodelling. These degenerative changes often precede injury, wherein additional inflammation and fibrotic tissue deposition make treatment difficult and reinjury highly likely. Understanding and preventing the causes of tendon functional decline is therefore vital to improving quality of life in the ageing population. Using an equine model, here we show that tendon fibroblasts, or tenocytes, isolated from aged tendons exhibit markers of senescence when cultured in vitro. Further, we describe how senescence in tenocytes drives inflammation, hypercontractility, and dysregulation of tendon matrix components. By replicatively senescing tenocytes isolated from young tendons, we observed that senescent tenocytes instigated proinflammatory signalling, had impaired capacity in wound healing assays, increased contractility, and secreted factors that induced senescence in healthy tenocytes. Further, tenocyte senescence dysregulated matrix turnover both at the gene and protein level. Finally, we demonstrate how senotherapeutic treatment of senescent tenocytes can reduce expression of senescence markers and restore proliferative capacity. Our results uncover systemic links between tendon ageing and cellular senescence, and identify mechanisms and therapeutic strategies for age-associated tendon degeneration.

cell biology↗

bioRxiv2026

Quantifying the Environmental Impact of Cell Culture

Laboratory research generates substantial plastic waste and associated greenhouse gas emissions, yet researchers often lack practical tools for quantifying the environmental impact of routine protocols or identifying realistic opportunities for reduction. Here, we present an open-source calculator for estimating plastic use and carbon dioxide equivalent emissions from laboratory protocols, using item weight, plastic composition, and estimated cradle-to-grave carbon footprint factors. We apply the tool to a standard cell culture workflow to demonstrate how evidence-based protocol adjustments can reduce plastic consumption and emissions without affecting experimental design or efficiency. The calculator is designed to be transparent, adaptable, and extendable, allowing researchers to add new consumables and tailor analyses to their own laboratory practices. This work provides a quantitative framework for translating sustainability principles into measurable, protocol-level changes and supports more environmentally responsible decision-making in biomedical research.

cell biology↗

bioRxiv2024

Integrative single-cell analysis of neural stem/progenitor cells reveals epigenetically dysregulated interferon response in progressive multiple sclerosis

Progressive multiple sclerosis (PMS) is characterized by a primary smouldering pathological disease process associated with a superimposed inflammatory activity. Cellular and molecular processes sustaining the pathobiology of PMS remain to be identified. We previously discovered senescence signatures in neural stem/progenitor cells (NSCs) from people with PMS. Applying direct reprogramming to generate directly induced NSCs (iNSCs) from somatic fibroblasts, we retain epigenetic information and observe hypomethylation of genes associated with lipid metabolic processes and IFN signalling only in PMS lines. Single-cell/nucleus transcriptomic and epigenetic profiling reveal an inflammatory, senescent-like, IFN-responsive radial glia (RG)-like cell subcluster mainly in PMS iNSCs that is driven by IFN-associated transcription factors. Lastly, we identify a population of senescent, IFN-responsive, disease-associated RG-like cells (DARGs) in the PMS brain that share pseudotime trajectories with iNSCs in vitro. We describe the existence of a non-neurogenic, dysfunctional DARG population that has the potential to fuel smouldering inflammation in PMS.

neuroscience↗

bioRxiv2023

Human Vascularized Bile Duct-on-a Chip: A multi-cellular micro-physiological system for studying Primary Sclerosing Cholangitis

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease in which the bile ducts of the liver become inflamed and scarred. Scarred bile ducts eventually narrow and obstruct and can cause additional liver pathology including liver failure, repeated infections, and tumors. The pathogenesis of PSC remains largely unknown, partly due to difficulty in obtaining cholangiocytes and partly due to a paucity of in vitro models that capture the various factors contributing to disease progression. Here we report the development of a human vascularized bile duct-on-a-chip that models blood vessels and bile ducts structurally and functionally in three dimensions and includes cholangiocytes derived from control and PSC patient tissue and bile. The flow of blood and bile was modeled by perfusion of cell-lined channels, and cholangiocytes and endothelial cells displayed differential responses to perfusion. Normal and PSC cholangiocytes polarized normally, formed mature tight junctions and displayed similar permeability, comparable to ex vivo measurements. The model with PSC cholangiocytes, however, became more inflammatory than the normal under the stimulation of IL-17A, which induced PBMC and differentiated Th17 cells in the vascular channel to transmigrate more through the endothelial layer of the vascular compartment. In sum, this human vascularized bile duct-on-a-chip recapitulated the vascular-biliary interface structurally and functionally and represents a novel multicellular platform to study inflammatory and fibrotic cholangiopathies such as PSC.

bioengineering↗

bioRxiv2023

Biliatresone treatment of pregnant mice causes changes in bile metabolism and liver inflammation in their offspring

Background & AimsBiliary atresia is a neonatal disease characterized by bile duct and liver damage, fibrosis, inflammation and abnormal bile metabolism. It appears to result from a prenatal exposure that spares the mother and affects the fetus. Our aim was to define the phenotype in neonatal mice after maternal exposure to low-dose biliatresone, a plant toxin implicated in biliary atresia in livestock. MethodsPregnant mice were treated orally with low-doses of biliatresone. Histological changes, bile acid profiles and immune profiles were analyzed in postnatal day 5 and 21 pups born to treated mothers. ResultsThe pups of mothers treated with this dose of biliatresone had no evidence of significant liver or ductular injury or fibrosis at postnatal day 5 or 21 and they grew normally. However, serum levels of glycocholic acid were elevated at postnatal day 5, suggesting altered bile metabolism, and bile metabolism became increasingly abnormal through postnatal day 21, with enhanced glycine conjugation of bile acids. There was also immune cell activation observed in the liver at postnatal day 21. ConclusionPrenatal exposure to low doses of an environmental toxin can cause liver inflammation and aberrant bile metabolism even in the absence of histological changes. Lay summaryPrenatal exposure to low doses of an environmental toxin can cause changes in bile metabolism in neonatal mice.

pharmacology and toxicology↗

bioRxiv2022

Injury and a program of fetal wound healing in the fetal and neonatal extrahepatic bile duct

IntroductionBiliary atresia (BA) is an obstructive cholangiopathy that initially affects the extrahepatic bile ducts (EHBDs) of neonates. The etiology is uncertain, but evidence points to a prenatal cause; however, the response of the fetal EHBD to injury remains unknown. The objective of this study was to define the fetal response to EHBD injury and to determine whether it follows a fetal wound healing paradigm. MethodsMouse, rat, sheep, and human EHBD samples were studied at different developmental time points. Models included a fetal sheep model of prenatal hypoxia, human BA EHBD remnants and liver samples taken at the time of the Kasai procedure, EHBDs isolated from neonatal rats and mice, and spheroids and other models generated from primary neonatal mouse cholangiocytes. ResultsA wide layer of high molecular weight HA encircling the lumen was characteristic of the normal perinatal but not adult EHBD. This layer, which was surrounded by collagen, expanded in injured ducts in parallel with extensive peribiliary gland (PBG) hyperplasia, increased mucus production and elevated serum bilirubin levels. BA EHBD remnants similarly showed increased HA centered around ductular structures compared with age-appropriate controls. High molecular weight HA typical of the fetal/neonatal ducts caused increased cholangiocyte spheroid growth, whereas low molecular weight HA induced abnormal epithelial morphology; low molecular weight HA caused matrix swelling in a bile duct-on-a-chip device. ConclusionThe fetal/neonatal EHBD, including in human EHBD remnants from Kasai surgeries, demonstrated an injury response with high levels of HA typical of the regenerative, scarless program termed fetal wound healing. Although generally beneficial, the expanded peri-luminal HA layer may swell and lead to elevated bilirubin levels and obstruction of the EHBD.

physiology↗

bioRxiv2022

Loss of cytoskeletal proteostasis links dysregulation of cell size and mechanotransduction in mesenchymal stem cell senescence

Tissues are maintained by homeostatic feedback mechanisms where cells respond to, but also modify, the chemical and mechanical properties of the surrounding extracellular matrix. Mesenchymal stem cells (MSCs) resident in the marrow niche experience a diverse mechanical environment, but ageing can affect the composition and quality of bone and marrow tissues. Here we quantified the effect of replication-induced senescence on MSC morphology and their ability to correctly respond to different substrate stiffnesses. The matrix proteome was found to be sensitive to substrate stiffness, but pharmacological inhibition of cellular contractility perturbed this response, decreasing levels of tenascin-C, fibulins and fibronectin. Similar decreases in these mechanosensitive proteins were observed in senescent cells, suggested a decoupling of mechanotransduction pathways. Intracellular proteomic and transcriptomic analyses confirmed a decrease in components of the cytoskeletal chaperone complex CCT/TRiC in senescent MSCs. Finally, pharmacological inhibition of CCT/TRiC was able to partially recapitulate senescence-associated morphological changes in non-senescent MSCs. These results demonstrate a senescence-mediated perturbation to cytoskeletal homeostasis, pathways of mechanotransduction and the secretion of matrix proteins required for tissue maintenance.

cell biology↗

bioRxiv2022

Glisson's capsule structure and function is altered in cirrhotic patients irrespective of etiology

Background and AimsGlissons capsule is the interstitial connective tissue that surrounds the liver. As part of its normal physiology, it withstands significant daily changes in liver size. The pathophysiology of the capsule in disease is not well understood. The aim of this study was to characterize the changes in capsule matrix, cellular composition, and mechanical properties that occur in liver disease and to determine whether these correlate with disease severity or etiology. Methods10 control, 6 steatotic, 7 moderately fibrotic and 37 cirrhotic patient samples were collected from autopsies, intraoperative biopsies and liver explants. Matrix proteins and cell markers were assessed by staining and second harmonic generation imaging. Mechanical tensile testing was performed on a test frame. ResultsCapsule thickness was significantly increased in cirrhotic samples compared to normal controls irrespective of disease etiology (69.62 {+/-} 9.99 and 171.269 {+/-} 16.65 {micro}m respectively), whereas steatosis and moderate fibrosis had no effect on thickness (62.15 {+/-} 4.97 {micro}m). Changes in cirrhosis included an increase in cell number (fibroblasts, vascular cells, infiltrating immune cells and biliary epithelial cells). Key matrix components (collagens 1 and 3, hyaluronan, versican and elastin) were all deposited in the lower capsule although only the relative amounts per area of hyaluronan and versican were increased. Organizational features including crimping and alignment of collagen fibers were also altered in cirrhosis. Unexpectedly, capsules from cirrhotic livers had decreased resistance to loading in comparison to controls. ConclusionsThe liver capsule, like the parenchyma, is an active site of disease, demonstrating changes in matrix and cell composition as well as mechanical properties. Lay summaryWe assessed the changes in composition and response to stretching of the liver outer sheath, the capsule, in human liver disease. We find an increase in key structural components and numbers of cells as well as a change in matrix organization of the capsule in the later stages of disease. This allows the diseased capsule to stretch more under any given force, suggesting it is less stiff than healthy tissue. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=116 SRC="FIGDIR/small/505570v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@10a9b60org.highwire.dtl.DTLVardef@15eea52org.highwire.dtl.DTLVardef@69b874org.highwire.dtl.DTLVardef@cccd03_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIThe capsule is an active site of disease: thickness and cellularity increase markedly in cirrhosis C_LIO_LIExtracellular matrix composition and organization change in cirrhosis C_LIO_LIThe cirrhotic capsule stretches more and is less stiff C_LI

physiology↗

bioRxiv2022

Versican binds collagen via its G3 domain and regulates the organization and mechanics of collagenous matrices

Type I collagen is the most abundant structural protein in the body and, with other fibrillar collagens, forms the fibrous network of the extracellular matrix (ECM). Another group of ECM polymers, the glycosaminoglycans (GAGs) and GAG-modified proteoglycans, play important roles in regulating collagen behaviors and contribute to the compositional, structural and mechanical complexity of the ECM. While the binding between collagen and small leucine-rich proteoglycans (SLRPs) has been studied in detail, the interactions between collagen and the large bottlebrush proteoglycan versican are not well understood. Here, we report that versican binds collagen directly and regulates collagen structure and mechanics. Versican colocalizes with collagen fibers in vivo and binds to collagen via its C-terminal G3 domain (a non-GAG-modified domain present in all known versican isoforms) in vitro; it promotes the deposition of a highly-aligned collagen-rich matrix by fibroblasts. Versican also shows an unexpected effect on the rheology of collagen gels in vitro, causing decreased stiffness and attenuated shear strain stiffening, and the cleavage of versican in liver results in reduced tissue compression stiffening. Thus, versican is an important collagen binding partner, playing a role in modulating collagen organization and mechanics.

cell biology↗

bioRxiv2021

Efemp1 modulates elastic fiber formation and mechanics of the extrahepatic bile duct

EGF-Containing Fibulin Extracellular Matrix Protein 1 (EFEMP1, also called fibulin 3) is an extracellular matrix protein linked in a genome-wide association study to biliary atresia, a fibro-inflammatory disease of the neonatal extrahepatic bile duct. EFEMP1 is expressed in most tissues and Efemp1 null mice have decreased elastic fibers in visceral fascia; however, in contrast to other short fibulins (fibulins 4 and 5), EFEMP1 does not have a role in the development of large elastic fibers, and its overall function remains unclear. We demonstrated that EFEMP1 is expressed in the submucosa of both neonatal and adult mouse and human extrahepatic bile ducts and that, in adult Efemp1+/- mice, elastin organization into fibers is decreased. We used pressure myography, a technique developed to study the mechanics of the vasculature, to show that Efemp1+/- extrahepatic bile ducts are more compliant to luminal pressure, leading to increased circumferential stretch. We conclude that EFEMP1 has an important role in the formation of elastic fibers and mechanical properties of the extrahepatic bile duct. These data suggest that altered expression of EFEMP1 in the extrahepatic bile duct leads to an abnormal response to mechanical stress such as obstruction, potentially explaining the role of EFEMP1 in biliary atresia.

physiology↗

bioRxiv2021

Senescence inhibits the chaperone response to thermal stress

Cells respond to stress by synthesising chaperone proteins that correct protein misfolding to maintain function. However, protein homeostasis is lost in ageing, leading to aggregates characteristic of protein-folding diseases. Whilst much is known about how these diseases progress, discovering what causes protein-folding to deteriorate could be key to their prevention. Here, we examined primary human mesenchymal stem cells (hMSCs), cultured to a point of replicative senescence and subjected to heat shock, as an in vitro model of the ageing stress response. We found through proteomic analysis that the maintenance of homeostasis deteriorated in senescent cells. Time-resolved analysis of factors regulating heat shock protein 70 kDa (HSPA1A) revealed a lack of capacities for protein turnover and translation to be key factors in limiting the stress response during senescence. A kinetic model predicted a consequence of these reduced capacities to be the accumulation of misfolded protein, a hypothesis supported by evidence of systematic changes to protein fold state. These results thus further our understanding of the underlying mechanistic links between ageing and loss of protein homeostasis.

cell biology↗

bioRxiv2020

Interstitial spaces are continuous across tissue and organ boundaries in humans

Bodies have "reticular networks" comprising collagens, elastin, glycosaminoglycans, and other extracellular matrix components, that are continuous within and around all organs. Fibrous tissue coverings of nerves and blood vessels create structural continuity beyond organ boundaries. We recently described fluid flow through such human fibrous tissues. It remains unclear whether these interstitial spaces are continuous through the body or are discontinuous, confined within individual organs. We investigated IS continuity using two approaches. Non-biological particles (tattoo pigment, colloidal silver) were tracked within colon and skin interstitial spaces and into adjacent fascia. We also exploited hyaluronic acid, a macromolecular component of interstitial spaces. Both techniques demonstrate continuity of interstitial spaces within and across organ boundaries, including within perineurium and vascular adventitia traversing organs and the spaces between them. We suggest a body-wide network of fluid-filled interstitial spaces with significant implications for molecular signaling, cell trafficking, and the spread of malignant and infectious disease.

pathology↗

bioRxiv2019

A Bile Duct-on-a-Chip with Organ-Level Functions

Chronic cholestatic liver diseases such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are frequently associated with damage to the barrier function of the biliary epithelium, but barrier function is difficult to study in vivo and has not been recapitulated in vitro. Here we report the development of a bile duct-on-a-chip that phenocopies not only the tubular architecture of the bile duct in three dimensions, but also its barrier functions. We demonstrated that mouse cholangiocytes in the channel of the device became polarized and formed mature tight junctions, and that the permeability of the cholangiocyte monolayer was comparable to that measured ex vivo for the rat bile duct. Permeability decreased significantly when cells formed a compacted monolayer with cell densities comparable to that seen in vivo. This device enabled independent access to the apical and basolateral surfaces of the cholangiocyte channel, allowing proof-of-concept toxicity studies with the biliary toxin biliatresone and the bile acid glycochenodeoxycholic acid. The cholangiocyte basolateral side was more vulnerable than the apical side to treatment with either agent, suggesting a protective adaptation of the apical surface that is normally exposed to bile. Further studies revealed a protective role of the cholangiocyte apical glycocalyx, wherein disruption of the glycocalyx with neuraminidase increased the permeability of the cholangiocyte monolayer after treatment with glycochenodeoxycholic acid. Conclusion: This bile duct-on-a-chip captured essential features of a simplified bile duct in structure and organ-level functions and represents a novel in vitro platform to study the pathophysiology of the bile duct using cholangiocytes from a variety of sources.

bioengineering↗

bioRxiv2019

Coordinated development of the mouse extrahepatic bile duct: implications for neonatal susceptibility to biliary injury

Background & AimsThe extrahepatic bile duct is the primary tissue initially affected by the cholangiopathy biliary atresia. Biliary atresia affects neonates exclusively and current animal models suggest that the developing bile duct is uniquely susceptible to damage. In this study, we aimed to define the anatomical and functional differences between the neonatal and adult mouse extrahepatic bile ducts.\n\nMethodsWe studied mouse passaged cholangiocytes, mouse BALB/c neonatal and adult primary cholangiocytes and isolated extrahepatic bile ducts, and a collagen reporter mouse. Methods included transmission electron microscopy, lectin staining, immunostaining, rhodamine uptake assays, bile acid toxicity assays, and in vitro modeling of the matrix.\n\nResultsThe cholangiocyte monolayer of the neonatal extrahepatic bile duct was immature, lacking the uniform apical glycocalyx and mature cell-cell junctions typical of adult cholangiocytes. Functional studies showed that the glycocalyx protected against bile acid injury and that neonatal cholangiocyte monolayers were more permeable than adult monolayers. In adult ducts, the submucosal space was filled with collagen I, elastin, hyaluronic acid, and proteoglycans. In contrast, the neonatal submucosa had little collagen I and elastin, although both increased rapidly after birth. In vitro modeling suggested that the composition of the neonatal submucosa relative to the adult submucosa led to increased diffusion of bile. A Col-GFP reporter mouse showed that cells in the neonatal but not adult submucosa were actively producing collagen.\n\nConclusionWe identified four key differences between the neonatal and adult extrahepatic bile duct. We showed that these features may have functional implications, suggesting the neonatal extrahepatic bile ducts are particularly susceptible to injury and fibrosis.\n\nLay SummaryBiliary atresia is a disease that affects newborns and is characterized by extrahepatic bile duct injury and obstruction with resulting liver injury. We identify four key differences between the epithelial and submucosal layers of the neonatal and adult extrahepatic bile duct and show that these may render the neonatal duct particularly susceptible to injury.\n\nHighlightsO_LIThe apical glycocalyx is thin and patchy in neonatal compared to adult cholangiocytes\nC_LIO_LINeonatal cholangiocytes have immature cell-cell junctions and increased permeability\nC_LIO_LIThe neonatal submucosal space has minimal collagen I or elastin\nC_LIO_LIThe neonatal submucosal space contains many actively collagen-secreting cells\nC_LI\n\nGraphical abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=95 SRC=\"FIGDIR/small/576256_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (27K):\norg.highwire.dtl.DTLVardef@1685e52org.highwire.dtl.DTLVardef@1086478org.highwire.dtl.DTLVardef@1fc3f55org.highwire.dtl.DTLVardef@1a20a5f_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗