Biology subjects

Phelps, E. A.

Publications and source records attributed to Phelps, E. A..

13 recordsLinked to original sources

bioRxiv2026

Mitochondrial and protein homeostasis pathways are transcriptionally impaired in islets during type 1 diabetes pathogenesis

The decline in first-phase insulin response (FPIR) during the presymptomatic period of type 1 diabetes (T1D) is well established. In-situ functional studies with pancreas tissue slices showed that {beta}-cell loss of glucose-responsiveness was independent of T-cell infiltration into islets in recent-onset T1D cases. However, the mechanisms driving {beta}-cell dysfunction before the onset of T1D remain unclear. In pancreas tissue from donors across the natural history of T1D, we utilized an in-situ, whole-islet phenotypical and transcriptomic approach to unravel novel targets in the glucose-stimulus coupled secretion pathway that are similarly impaired in T-cell infiltrated and non-infiltrated islets. Specifically, we observed that islets from autoantibody positive (single(s) or multiple(m) AAb+) donors exhibited activation of post-transcriptional gene regulation along with reduced protein translation, processing in the endoplasmic reticulum (ER), and ER stress. Disrupted mitochondrial metabolism and bioenergetics were prominent in islets from multiple AAb+ and T1D donors with disease durations [≤]7 years. In addition, T1D islets presented reduced mitochondrial protein import, quality control, and dynamics, together with downregulated genes in insulin secretory pathways. During infiltration, these pathways remain dysregulated while immune/inflammatory transcripts were increased. These studies identified novel mechanisms of {beta}-cell dysregulation before symptomatic onset and independent of T-cell infiltration in T1D pathogenesis.

physiology↗

bioRxiv2026

Biosensor Cell Array Reveals Temporal GABA Secretion Dynamics from Pancreatic Islets

Pancreatic beta cells have the unique function of synthesizing and secreting high amounts of the inhibitory neurotransmitter {gamma}-aminobutyric acid (GABA). The mechanism of GABA secretion, whether vesicular or channel-mediated, is debated. Our study reveals surprising temporal complexity in the pattern of islet GABA secretion. We used insulin secretion modulators to demonstrate that GABA release is not directly correlated with insulin secretion. VGAT reporter mice also showed that beta cells do not express the requisite vesicular GABA transporter (VGAT) for vesicular GABA release. Instead, GABA is secreted from the cytosol in pulses by the LRRC8A/D isoform of the volume regulatory anion channel (VRAC). We further demonstrate the dynamic coordination of GABA release with calcium influx in beta cells and dependence on beta cell depolarization. These results suggest a model where GABA is released during the peaks of beta cell calcium oscillations to provide feedback which strengthens and reinforces the oscillation waveform.

physiology↗

bioRxiv2025

Anti-CD3 microporous annealed particle hydrogel protects stem cell derived beta cells from autoreactive T cells

Type 1 diabetes (T1D) results from autoimmune destruction of pancreatic beta cells, leaving patients dependent on exogenous insulin and at risk of severe hypoglycemic episodes. Stem cell-derived beta-like cells (sBCs) offer a promising approach for beta cell replacement therapy, but clinical translation is limited by immune-mediated rejection, recurrent autoimmunity, and inhospitable transplantation sites. Biomaterials have been investigated to provide localized immune-isolation and immunomodulation, but foreign body responses and rapid depletion of therapeutic agents remain as obstacles to clinical translation. Here, we present a microporous annealed particle (MAP) hydrogel functionalized with an anti-CD3 monoclonal antibody (CD3) to provide a localized immunomodulatory microenvironment for beta cell replacement therapy. MAP hydrogels consisting of guest-host interlinked polyethylene glycol-maleimide (PEG-MAL) microgels supported rapid vascularization, minimal foreign body response, and engraftment of syngeneic islets in mice. CD3 MAP hydrogel halted T cell migration in vitro and protected transplanted sBCs from immune-mediated destruction by HLA-matched diabetogenic T cells in vivo. Subcutaneous CD3 functionalized MAP hydrogel also protected the endogenous islets in the pancreas, demonstrating potential for systemic immune modulation. These findings establish CD3 MAP hydrogels as a promising strategy for localized immune modulation in cell replacement therapy.

bioengineering↗

bioRxiv2025

Inhibition of cell-mediated immunity in type 1 diabetes by beta cell-targeted PD-1 agonists in pancreas tissue slices

Tissue-targeted immunotherapies for type 1 diabetes (T1D) hold potential to protect pancreatic beta cells while minimizing systemic immunosuppression. We used a bispecific agonist called Immune Modulating Monoclonal-TCR Against Autoimmune Disease (ImmTAAI), consisting of a T cell receptor (TCR) targeting domain fused with a PD-1 agonist to specifically bind beta cells and suppress autoreactive T cells. We used live pancreas slices to demonstrate targeting of ImmTAAI molecules to pre-proinsulin peptide-HLA-A2 complexes on human beta cells. ImmTAAI protected beta cells from T cell killing by increasing T cell motility and inhibiting cytokine secretion. ImmTAAI treatment also increased the motility of islet-infiltrating T cells in slices from a donor with recent-onset T1D and preserved insulin secretion in slices co-cultured with T cell avatars transduced with diabetogenic TCRs. These data demonstrate that ImmTAAI molecules have the potential to limit T cell activity locally, making this an attractive platform to elicit targeted immunoregulation in T1D. One Sentence SummaryWe demonstrate inhibition of cellular immunity in human type 1 diabetes using a beta cell-targeting, affinity-enhanced TCR fused to a PD-1 agonist.

bioengineering↗

bioRxiv2025

3D Chemotaxis Chip for Investigating Natural Killer Cell Migration Mechanisms

IntroductionNatural killer (NK) cells are a promising tool for cancer immunotherapy, as they can rapidly recognize and kill cancer cells without prior knowledge of tumor-specific antigens while leaving healthy cells unharmed. However, a major challenge in NK cell-based therapies is their inadequate infiltration and function within solid tumors. Advancements in NK cell therapies for solid malignancies require a better understanding of the various factors that influence NK cell migration to and within the tumor microenvironment. MethodsThe objective of this study was to develop a chemotaxis chip with a tunable 3D hydrogel that enables the spatiotemporal analysis of NK cell migration. Results/DiscussionBy manipulating the 3D hydrogel or inhibiting key integrin and protease interactions, we found that NK cells heavily relied on protease-dependent migration but could leverage other mechanisms for faster migration. Additionally, when hyaluronic acid, an important extracellular matrix component in tumors, was incorporated into the hydrogel, NK cells migrated faster and farther in the chemotaxis chip. ConclusionThis study establishes a novel migration assay to observe NK cell behavior in real-time, providing a platform for investigating the mechanisms of NK cell migration and identifying strategies to improve NK cell trafficking within solid tumors.

bioengineering↗

bioRxiv2025

Item recognition is associated with gut microbiota composition in healthy humans

Murine studies show that the gut microbiota - the collection of the microbes residing in the large intestine - affects memory performance in the host. However, whether commensal gut bacteria are linked to human episodic memory remains unknown. Here, we investigated whether individual differences in episodic memory performance were associated with differences in the indigenous gut microbiota composition between individuals. We show that greater gut microbiota alpha diversity was associated with better item recognition and that gut microbiota dissimilarity index (beta diversity) between participants was associated with differences in their performance. Finally, our results suggest that Prevotella copri might play a role in the relationship between gut microbiota and human item recognition in healthy individuals. In a sample size larger than previous human studies and examining unmanipulated gut microbiota, we provide evidence that episodic memory in healthy humans is linked to their gut microbiota composition. SIGNIFICANCE STATEMENTUnderstanding the relationship between the gut microbiota - the collective of microbes in our gut - and human cognition represents a pivotal frontier in neuroscience. Our study dives into this quest by exploring the connection between the indigenous gut microbiota and episodic memory in healthy individuals. While prior research has illuminated this relationship in murine models, our study extends these findings to humans, providing compelling evidence that gut microbiota diversity and structural composition are associated with differences in episodic memory performance. By shifting the focus from probiotic-based interventions to the study of our commensal gut microbes, our findings shed light on how the gut microbiota, in its natural state, could be linked to interindividual differences in human cognition.

animal behavior and cognition↗

bioRxiv2025

Efficient transduction of pancreas tissue slices with genetically encoded calcium integrators

This study combines live pancreas tissue slices with viral transduction of the Calcium Modulated Photoactivatable Ratiometric Integrator 2 (CaMPARI2) biosensor for high-throughput analysis of islet calcium secretagogue responses. A key challenge of the pancreas slice model has been efficient transgene delivery throughout the slice volume while maintaining viability and function. Here, we demonstrate a robust adenoviral gene delivery approach to transduce slices with CaMPARI2 and apply photoconverting light to permanently mark glucose-induced calcium activity across all islets. This approach demonstrates glucose responsive CaMPARI2 labeling that correlates with insulin secretion. Using this novel high-throughput approach, we examine the relationship between islet size and calcium response. Larger isolated islets exhibit greater CaMPARI2 photoconversion in high glucose, whereas no size-function correlation is observed in islets resident in live slices. We also observe that slices capture a substantially higher proportion of small islets than isolated islets. Integrating CaMPARI2 with live pancreas slice studies enables multiplexed analyses, linking functional readouts to spatial features.

physiology↗

bioRxiv2024

Beta cell dysfunction occurs independently of insulitis in type 1 diabetes pathogenesis

The loss of insulin secretory function associated with type 1 diabetes (T1D) is attributed to the immune-mediated destruction of beta cells. Yet, at onset of T1D, patients often have a significant beta cell mass remaining while T cell infiltration of pancreatic islets is sporadic. Thus, we investigated the hypothesis that the remaining beta cells in T1D are largely dysfunctional using live human pancreas tissue slices prepared from organ donors with recently diagnosed T1D. Beta cells in slices from donors with T1D had significantly diminished Ca2+ mobilization and insulin secretion responses to glucose. Beta cell function was equally impaired in T cell-infiltrated and non-infiltrated islets. Fixed tissue staining and gene expression profiling of laser-capture microdissected islets revealed significant decreases of proteins and genes in the glucose stimulus secretion coupling pathway. From these data, we posit that functional defects occur in the remaining mass of beta cells during human T1D pathogenesis.

physiology↗

bioRxiv2024

Impaired islet function with normal exocrine enzyme secretion is consistent across the head, body, and tail pancreas regions in type 1 diabetes

Histopathological heterogeneity in human pancreas has been well documented; however, functional evidence at the tissue level is scarce. Herein we investigated in situ glucose-stimulated islet and carbachol-stimulated acinar cell secretion across the pancreas head (PH), body (PB), and tail (PT) regions in no diabetes (ND, n=15), single islet autoantibody-positive (1AAb+, n=7), and type 1 diabetes donors (T1D, <14 months duration, n=5). Insulin, glucagon, pancreatic amylase, lipase, and trypsinogen secretion along with 3D tissue morphometrical features were comparable across the regions in ND. In T1D, insulin secretion and beta-cell volume were significantly reduced within all regions, while glucagon and enzymes were unaltered. Beta-cell volume was lower despite normal insulin secretion in 1AAb+, resulting in increased volume-adjusted insulin secretion versus ND. Islet and acinar cell secretion in 1AAb+ were consistent across PH, PB and PT. This study supports low inter-regional variation in pancreas slice function and potentially, increased metabolic demand in 1AAb+.

pathology↗

bioRxiv2023

Serum from pregnant donors induces human beta cell proliferation and insulin secretion

Pancreatic beta cells are among the slowest replicating cells in the human body. Human beta cells usually do not increase in number with exceptions being during the neonatal period, in cases of obesity, and during pregnancy. This project explored maternal serum for stimulatory potential on human beta cell proliferation and insulin output. Gravid, full-term women who were scheduled to undergo cesarean delivery were recruited for this study. A human beta cell line was cultured in media supplemented with serum from pregnant and non-pregnant donors and assessed for differences in proliferation and insulin secretion. A subset of pregnant donor sera induced significant increases in beta cell proliferation and insulin secretion. Pooled serum from pregnant donors also increased proliferation in primary human beta cells but not primary human hepatocytes indicating a cell-type specific effect. This study suggests stimulatory factors in human serum during pregnancy could provide a novel approach for human beta cell expansion.

cell biology↗

bioRxiv2022

Immune engineered extracellular vesicles to modulate T cell activation in the context of type 1 diabetes

Extracellular vesicles (EVs) are small, biologically active, cell-secreted vesicles that can affect immune responses through antigen presentation and co-stimulation or co-inhibition. We generated designer EVs to modulate autoreactive T cells in the context of type 1 diabetes by engineering K562 cells to express HLA-A*02 (HLA-A2) alongside co-stimulatory CD80 and/or co-inhibitory PD-L1. EVs presenting HLA-A2 and CD80 activated CD8+ T cells in a dose, antigen, and HLA-specific manner. Adding PD-L1 to these EVs produced an immunoregulatory response, reducing CD8+ T cell activation and cytotoxicity in vitro. EVs alone could not stimulate T cells without antigen presenting cells (APCs), suggesting that EVs act by cross-dressing APCs. EVs lacking CD80 were ineffective at modulating CD8+ T cell activation, suggesting that both peptide-HLA complex and costimulatory molecules are required for EV-mediated immune modulation through APC cross-dressing. These results provide mechanistic insight into the rational design of EVs as a cell-free, yet precision medicine-based approach to immunotherapy that can be tailored to promote antigen-specific immune tolerance or pro-inflammatory responses.

bioengineering↗

bioRxiv2022

Human threat learning is associated with gut microbiota composition

Rodent studies have shown that the gut microbiota can influence threat and safety learning, which has been linked to anxiety phenotypes. In humans, it has been demonstrated that microbiota composition varies with anxiety disorders, but evidence showing an association with threat learning is lacking. Here, we tested whether individual variability in threat and safety learning was related to gut microbiota composition in healthy adults. We found that threat, but not safety learning varies with individuals microbiome composition. Our results provide evidence that the gut microbiota is associated with excitatory threat learning across species. Significance StatementLearning from threats and safety is a core mechanism of anxiety disorders, and studies in rodent models have shown that the gut microbiota can modulate such behaviors. Although previous literature on humans shows a relationship between emotional circuits and gut microbiota, the evidence linking learning and microbiota is lacking. In a Pavlovian threat conditioning paradigm, we show that patterns of gut microbiota composition in healthy humans relate to their patterns of threat learning, but not safety learning. Our findings suggest one mechanism by which the human gut microbiota is associated with anxiety-related behaviors.

animal behavior and cognition↗

bioRxiv2022

Neuronal growth regulator 1 (NEGR1) promotes synaptic targeting of glutamic acid decarboxylase 65 (GAD65)

Neuronal growth regulator 1 (NEGR1) is a glycosylphosphatidylinositol-anchored cell adhesion molecule encoded by an obesity susceptibility gene. We demonstrate that NEGR1 accumulates in GABAergic inhibitory synapses in hypothalamic neurons, a GABA-synthesizing enzyme GAD65 attaches to the plasma membrane, and NEGR1 promotes clustering of GAD65 at the synaptic plasma membrane. GAD65 is removed from the plasma membrane with newly formed vesicles. The association of GAD65 with vesicles results in increased GABA synthesis. In NEGR1 deficient mice, the synaptic targeting of GAD65 is decreased, the GABAergic synapse densities are reduced, and the reinforcing effects of food rewards are blunted. In mice fed a high fat diet, levels of NEGR1 are increased and GAD65 abnormally accumulates at the synaptic plasma membrane. Our results indicate that NEGR1 regulates a previously unknown step required for synaptic targeting and functioning of GAD65, which can be affected by bidirectional changes in NEGR1 levels causing disruptions in the GABAergic signaling controlling feeding behavior.

neuroscience↗