Biology subjects

Browne, S.

Publications and source records attributed to Browne, S..

5 recordsLinked to original sources

bioRxiv2025

Differentiating the Roles of Metabolic Similarity and Ionic Coupling in Determining the Beta Hub Cell Phenotype

Pancreatic beta cells regulate circulating glucose levels by releasing insulin. Beta cells transduce elevated blood glucose into electrical activity through an intrinsic cascade of metabolic and electrophysiologic responses. These responses are synchronized across the electrically connected network of beta cells, such that insulin release is also relatively synchronous. Despite their coordinated behavior, individual beta cells exhibit significant functional heterogeneity. This heterogeneity is thought to provide cells with specific functional phenotypes the ability to control the activity of the broader network. Hub cells, identified by their synchronized [Ca2+] activity, are one such functional subpopulation, and are believed to orchestrate the second, oscillatory phase of insulin release. However, it remains unclear whether the cell-autonomous characteristics of hub cells, such as their metabolic activity and electrophysiologic properties, are more important than their network characteristics (i.e. gap junctional coupling) for their ability to influence broader network activity. In this study, we investigate the roles of intrinsic metabolic and electrophysiologic properties and ionic coupling in determining the beta hub cell phenotype. Using a computational islet model of 1,000 beta cells, our analysis revealed that both intrinsic metabolic properties and structural coupling via gap junctions are crucial for determining the hub cell phenotype. After investigating the intrinsic coupling conductance of neighboring cells and the number of structural (direct electrical) links as independent contributors to the hub cells local electrical coupling, we find that the number of cells to which a beta cell is directly coupled may be a key determinant of its propensity to serve as a hub cell in the model. As predicted for this subpopulation, we also demonstrate that decoupling hub cells impairs the functional connectivity of the entire network. Our findings indicate the importance of both autonomous cellular dynamics and non-autonomous structural coupling for the hub cell phenotype. These insights help build a fundamental understanding of hub cells, which in turn may contribute to identifying potential approaches to preserve or improve beta cell function and thereby manage the progression of diabetes.

bioengineering↗

bioRxiv2025

Exploring the intrinsic and extrinsic determinants of heterogeneity in a β-cell network

Pancreatic islets are micro-organs composed of multiple endocrine cell types. {beta}-cells are the most common of these and are highly heterogeneous in both their intrinsic properties, such as ion channel conductances and metabolic activity, and extrinsic properties, including gap junction coupling and paracrine signaling. Capturing these diverse sources of heterogeneity is essential for computational models that aim to reproduce islet function. We evaluate two established multicellular models, the coupled Cha-Noma model of the mouse {beta}-cell network, and the Riz human model. Prior work with these two models suggest that the Cha-Noma model involves minimal intrinsic heterogeneity and therefore bursts with highly synchronized activity, whereas heterogeneity in the Riz model prescribed from in vitro patch-clamp results in highly unsynchronized behavior of the coupled network. We hypothesize that adjusting the number of bursting cells in both model formulations may invoke more physiologically realistic network coordination. We applied a categorical sensitivity analysis to establish which parameters are most important for determining bursting in single cells of the Riz model. We also introduced new heterogeneity (based on single-cell gene expression) in parameters that had previously been treated as invariant among {beta}-cells. We hypothesized that introducing heterogeneity in the small conductance Ca2+ K+ channel in particular could promote a higher proportion of bursting cells. Lastly, both models fail to incorporate the influences of non-{beta}-cells. We introduced paracrine signaling between and {beta}-cells into the coupled Cha-Noma model and showed it plays a role in accelerating the response time of {beta}-cells to acute glucose stimulation (i.e. promotes a 1st responder phenotype).

bioengineering↗

bioRxiv2025

Scaffold-mediated miRNA-155 inhibition promotes regenerative macrophage polarisation leading to anti-inflammatory, angiogenic, and neurogenic responses for wound healing

Chronic wounds represent a significant clinical challenge due to persistent inflammation and impaired nerve regeneration, both of which delay healing. Conventional treatments often yield limited success and inconsistent outcomes, especially in complex and recurring wounds. Combinatorial strategies that integrate biomaterial scaffolds with gene delivery offer a promising approach to promote tissue repair. MicroRNAs (miRNAs), particularly miRNA-155, have emerged as crucial regulators of wound healing. MiRNA-155 is highly expressed in inflammatory conditions and plays a key role in macrophage activation, polarisation, and nerve regeneration. In this context, this study introduces a miRNA-155 inhibitor-activated scaffold designed to modulate the chronic wound environment by inhibiting miRNA-155. MiRNA-155 inhibitor complexed GET nanoparticles were characterised and incorporated into collagen-glycosaminoglycan (CG) scaffolds. These supported dermal fibroblast and endothelial cell growth while enabling controlled inhibitor release. Scaffold-mediated miRNA-155 inhibition in both non-polarised (M0) and pro-inflammatory (M1) macrophages promoted anti-inflammatory (M2) polarisation. Macrophage secretome analysis showed reduced inflammatory cytokines and increased angiogenic growth factor secretion in both conditions. The regenerative potential of the miRNA-i-activated scaffold via macrophage polarisation was validated through inflammatory and angiogenic functional assays with endothelial cells. In parallel, scaffold-mediated miRNA-155 delivery to dorsal root ganglia (DRG) promoted neurogenic outcomes through enhanced axonal regrowth, essential for the synergistic repair of chronic wounds across the skin-nerve axis. In vivo implantation of miRNA-155 inhibitor-activated scaffolds in chicks demonstrated successful integration without disrupting vascular network formation. Collectively, these findings establish the miRNA-155 inhibitor-activated scaffold as a regenerative platform with anti-inflammatory, pro-angiogenic, and neurogenic outcomes, offering a multifaceted solution for chronic wound healing applications. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/682055v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@1c6a6b6org.highwire.dtl.DTLVardef@eb04f9org.highwire.dtl.DTLVardef@1937f15org.highwire.dtl.DTLVardef@7c70d3_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2025

Cerebral Organoids with Integrated Endothelial Networks Emulate the Neurovascular Unit and Mitigate Core Necrosis

Cerebral organoids (COs) are multicellular, self-organized, in vitro, 3D brain-like tissues used for developmental biology, disease modelling and drug screening. However, their lack of vascularity renders them less physiologically accurate. Vascularization of COs remains challenging due to the different requirements between COs and vascular cells, limited vascular network penetration within the organoid, and the absence of luminal perfusion. Here, we devised an encapsulation approach in which human brain microvascular endothelial cells (HBMVECs) were delivered to developing COs from progressively degrading extracellular matrix (ECM)-based hydrogel droplets. By tuning this hydrogel concentration and media composition, we observed enhanced vascular-like network formation that expanded within the organoid tissue. Using pathway inhibitors, we showed that a subset of the endothelial cells (ECs) originated from the CO itself, promoting network integration. Endothelial networks displayed blood-brain barrier (BBB) features, including astrocytic end-footlike interactions, pericyte wrapping, and collagen-laminin basal lamina. Vascularized COs exhibited greater media internalization and up to three-fold lower apoptosis than non-vascularized COs. This comprehensive 3D neurovascular model is a promising platform for cerebrovascular research and drug testing applications. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=132 SRC="FIGDIR/small/650161v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@175edb7org.highwire.dtl.DTLVardef@1499b91org.highwire.dtl.DTLVardef@184567borg.highwire.dtl.DTLVardef@149c8e4_HPS_FORMAT_FIGEXP M_FIG Graphical abstract C_FIG HighlightsO_LIAddition and angiogenic stimulation of human brain microvascular endothelial cells (HBMVECs) co-cultured with cerebral organoids (COs) generate multicellular vascular-like networks C_LIO_LIVascularization induces changes in organoid morphology but not on tissue stiffness C_LIO_LIEndothelial networks morphological features are correlated with the concentration of the supporting matrix C_LIO_LIA number of the endothelial cells (ECs) in the networks originate from the organoid itself C_LIO_LIEndothelial networks integrate within the organoid tissue interacting with astrocytes and pericyte-like cells, and are surrounded by basement membrane-like depositions C_LIO_LIVascularized COs exhibit higher media diffusion, and a reduced necrotic core compared to non-vascularized COs C_LI

bioengineering↗

bioRxiv2024

Selective enrichment of high-affinity clade II N2O-reducers in a mixed culture

Microorganisms encoding for the N2O reductase (NosZ) are the only known biological sink of the potent greenhouse gas N2O, and are central to global N2O mitigation efforts. Yet, the ecological constraints selecting for different N2O-reducers strains and controlling the assembly of N2O-respiring communities remain largely unknown. Of particular biotechnological interest are clade II NosZ populations, which usually feature high N2O affinities and often lack other denitrification genes. Two planktonic N2O-respiring mixed cultures were enriched under limiting and excess dissolved N2O availability to assess the impact of substrate affinity and N2O cytotoxicity, respectively. Genome-resolved metaproteomics was used to infer the metabolism of the enriched populations. We show that clade II N2O-reducers outcompete clade I affiliates for N2O at sufficiently low sludge dilution rates (0.006 h-1), a scenario previously only theorized based on pure-cultures. Under N2O limitation, all enriched N2O-reducers encoded and expressed only clade II NosZ, while also possessing other denitrification genes. Two Azonexus and Thauera genera affiliates dominated the culture. We explain their coexistence with the genome-inferred metabolic exchange of cobalamin intermediates. Conversely, under excess N2O, clade I and II populations coexisted. Notably, the single dominant N2O-reducer (genus Azonexus) expressed most cobalamin biosynthesis marker genes, likely to contrast the continuous cobalamin inactivation by dissolved cytotoxic N2O concentrations (400 {micro}M). Ultimately, we demonstrate that the solids dilution rate controls the selection among NosZ clades, albeit the conditions selecting for genomes possessing the sole nosZ remain elusive. Additionally, we suggest the significance of N2O-cobalamin interactions in shaping the composition of N2O-respiring microbiomes.

systems biology↗