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Dr Rahul Ravindran has been awarded a highly competitive MRC Clinical Research Training Fellowship, following a successful research placement at the Kennedy Institute in 2019.
Learning and teaching biological data science in the Bioconductor community.
Modern biological research is increasingly data-intensive, leading to a growing demand for effective training in biological data science. In this article, we provide an overview of key resources and best practices available within the Bioconductor project-an open-source software community focused on omics data analysis. This guide serves as a valuable reference for both learners and educators in the field.
Systemic inflammation impairs myelopoiesis and interferon type I responses in humans.
Systemic inflammatory conditions are classically characterized by an acute hyperinflammatory phase, followed by a late immunosuppressive phase that elevates the susceptibility to secondary infections. Comprehensive mechanistic understanding of these phases is largely lacking. To address this gap, we leveraged a controlled, human in vivo model of lipopolysaccharide (LPS)-induced systemic inflammation encompassing both phases. Single-cell RNA sequencing during the acute hyperinflammatory phase identified an inflammatory CD163+SLC39A8+CALR+ monocyte-like subset (infMono) at 4 h post-LPS administration. The late immunosuppressive phase was characterized by diminished expression of type I interferon (IFN)-responsive genes in monocytes, impaired myelopoiesis and a pronounced attenuation of the immune response on a secondary LPS challenge 1 week after the first. The infMono gene program and impaired myelopoiesis were also detected in patient cohorts with bacterial sepsis and coronavirus disease. IFNβ treatment restored type-I IFN responses and proinflammatory cytokine production and induced monocyte maturation, suggesting a potential treatment option for immunosuppression.
Feasibility assessment of radiolabeled FAPI-04 for diagnostic and therapeutic use in rheumatoid arthritis.
OBJECTIVE: Fibroblast activation protein alpha (FAPα) plays a key role in cartilage degradation, inflammation, and bone erosion, particularly in rheumatoid arthritis (RA) where fibroblast-like synoviocytes in synovial tissue show elevated FAPα expression. This study explored radiolabeled FAP inhibitors for arthritis diagnosis and therapy. DESIGN: We used the radiotracer 68Ga-FAPI-04 for PET/CT imaging to predict collagen-induced arthritis (CIA) onset. Weekly scans quantified tracer uptake via SUV values, correlating results with disease scores and incidence. For therapeutic evaluation, 177Lu-FAPI-04 targeted FAPα-expressing cells, and arthritis scores of treated CIA mice were compared with untreated controls using one-way ANOVA. RESULTS: CIA mice with elevated SUV one week post-booster immunization had a 94.6 % arthritis incidence. SUV correlated with arthritis severity, reflecting increased FAPα expression. Treatment with 177Lu-FAPI-04 reduced arthritis scores by 64 % compared to controls (p
A Single-Domain VNAR Nanobody Binds with High-Affinity and Selectivity to the Heparin Pentasaccharide Fondaparinux
Glycosaminoglycans (GAGs) are key ligands for proteins involved in physiological and pathological processes. Specific GAG-binding patterns are rarely identified, with the heparin pentasaccharide as an Antithrombin-III ligand being the best characterized. Generating glycan-specific antibodies is difficult due to their size, pattern dispersion, and flexibility. Single-domain variable new antigen receptors (VNAR nanobodies) from nurse sharks are highly soluble, stable, and versatile. Their unique properties suggest advantages over conventional antibodies, particularly for challenging biotherapeutic targets. Here we have used VNAR semi-synthetic phage libraries to select high-affinity fondaparinux-binding VNARs that did not show cross-reactivity with other GAG species. Competition ELISA and surface plasmon resonance identified a single fondaparinux-selective VNAR clone. This VNAR exhibited an extraordinarily stable protein fold: the beta-strands are stabilized by a robust hydrophobic network, as revealed by heteronuclear NMR. Docking fondaparinux to the VNAR structure revealed a large contact surface area between the CDR3 loop of the antibody and the glycan. Fusing the VNAR with a human Fc domain resulted in a stable product with a high affinity for fondaparinux (Kd = 9.3 × 10−8 M) that could efficiently discriminate between fondaparinux and other glycosaminoglycans. This novel glycan-targeting screening technology represents a promising therapeutic strategy for addressing GAG-related diseases.
Autoimmunity in inflammatory bowel disease: a holobiont perspective
Adaptive immunity towards self-antigens (autoimmunity) and intestinal commensal microbiota is a key feature of inflammatory bowel disease (IBD). Considering mucosal adaptive immunity from a holobiont perspective, where the host and its microbiome form a single physiological unit, emphasises the challenge of avoiding damaging responses to self-antigen and symbiotic microbial communities in the gut while protecting against potential pathogens. Intestinal tolerance mechanisms prevent maladaptive T and B cell responses to microbial, environmental, and self-antigens, which drive inflammation. We discuss the spectrum of antimicrobial and autoantibody responses and highlight mechanisms by which common IBD-associated adaptive immune responses contribute to disease.
X-Linked Hypophosphatemia Management in Adults: An International Working Group Clinical Practice Guideline.
PURPOSE: An international working group (IWG) consisting of experts in X-linked hypophosphatemia (XLH) developed global guidelines providing a comprehensive, evidence-based approach to XLH diagnosis, management, and monitoring. METHODS: The IWG, consisting of 43 members as well as methodologists and a patient partner, conducted 2 systematic reviews (SRs) and narrative reviews to address key areas. The SRs addressed the impact of burosumab compared to conventional therapy (phosphate and active vitamin D) or no therapy on patient-important outcomes in adults. They also evaluated conventional therapy compared to no therapy. GRADE methodology was applied to evaluate the certainty of evidence. Non-GRADED recommendations were made in the presence of insufficient evidence to conduct SRs. These guidelines have been reviewed and endorsed by several medical and patient societies and organizations. RESULTS: The diagnosis of XLH is based on integrating clinical evaluation, laboratory findings confirming renal phosphate wasting (following exclusion of conditions mimicking XLH), and skeletal imaging. Fibroblast growth factor 23 measurement and DNA analysis are of value in the diagnosis, if available. Pathogenic or likely pathogenic variants in the PHEX gene are confirmatory but not necessary for the diagnosis. Management requires a multidisciplinary team knowledgeable and experienced in XLH. Effective medical therapy with burosumab can improve fracture and pseudofracture healing. MAIN CONCLUSION: In adults with XLH and fractures or pseudofractures, burosumab is recommended over no therapy (strong recommendation, GRADEd). Additionally, burosumab is suggested as the preferred treatment compared to conventional therapy (conditional recommendation, GRADEd) in the absence of fractures or pseudofractures. If burosumab is not available, symptomatic adults should be treated with conventional therapy (Non-GRADEd recommendation).
Exploring cellular changes in ruptured human quadriceps tendons at single-cell resolution.
Tendon ruptures in humans have often been studied during the chronic phase of injury, particularly in the context of rotator cuff disease. However, the early response to acute tendon ruptures remains less investigated. Quadriceps tendons, which require prompt surgical treatment, offer a model to investigate this early response. Therefore, this study aimed to explore the early cellular changes in ruptured compared to healthy human quadriceps tendons. Quadriceps tendon samples were collected from patients undergoing fracture repair (healthy) or tendon repair surgery (collected 7-8 days post-injury). Nuclei were isolated for single-nucleus RNA sequencing, and comprehensive transcriptomic analysis was conducted. The transcriptomes of 12,808 nuclei (7268 from healthy and 5540 from ruptured quadriceps tendons) were profiled, revealing 12 major cell types and several cell subtypes and states. Rupture samples showed increased expression of genes related to extracellular matrix organisation and cell cycle signalling, and a decrease in expression of genes in lipid metabolism pathways. These changes were predominantly driven by gene expression changes in the fibroblast, vascular endothelial cell (VEC), mural cell, and macrophage populations: fibroblasts shift to an activated phenotype upon rupture and there is an increase in the proportion of capillary and dividing VECs. A diverse immune environment was observed, with a shift from homeostatic to activated macrophages following rupture. Cell-cell interactions increased in number and diversity in rupture, and primarily involved fibroblast and VEC populations. Collectively, this transcriptomic analysis suggests that fibroblasts and endothelial cells are key orchestrators of the early injury response within ruptured quadriceps tendon. KEY POINTS: Tendon ruptures in humans have regularly been studied during the chronic phase of injury, but less is known about the early injury response after acute tendon ruptures. This study explored the early cellular changes in ruptured compared to healthy human quadriceps tendons at single-cell resolution. Fibroblasts and endothelial cells seem to be the key orchestrators of the early injury response within ruptured quadriceps tendon. Therefore, these cell types are obvious targets for interventions to enhance tendon healing. Overall, this study highlights that the development of more effective therapeutic options for tendon injury requires better understanding of the cellular, extracellular, and mechanical landscape of tendon tissue.
Different niches for stem cells carrying the same oncogenic driver affect pathogenesis and therapy response in myeloproliferative neoplasms.
Aging facilitates the expansion of hematopoietic stem cells (HSCs) carrying clonal hematopoiesis-related somatic mutations and the development of myeloid malignancies, such as myeloproliferative neoplasms (MPNs). While cooperating mutations can cause transformation, it is unclear whether distinct bone marrow (BM) HSC-niches can influence the growth and therapy response of HSCs carrying the same oncogenic driver. Here we found different BM niches for HSCs in MPN subtypes. JAK-STAT signaling differentially regulates CDC42-dependent HSC polarity, niche interaction and mutant cell expansion. Asymmetric HSC distribution causes differential BM niche remodeling: sinusoidal dilation in polycythemia vera and endosteal niche expansion in essential thrombocythemia. MPN development accelerates in a prematurely aged BM microenvironment, suggesting that the specialized niche can modulate mutant cell expansion. Finally, dissimilar HSC-niche interactions underpin variable clinical response to JAK inhibitor. Therefore, HSC-niche interactions influence the expansion rate and therapy response of cells carrying the same clonal hematopoiesis oncogenic driver.
Tumour heterogeneity promotes collective invasion and cancer metastatic dissemination.
Heterogeneity within tumour cell populations is commonly observed in most cancers. However, its impact on metastatic dissemination, one of the primary determinants of the disease prognosis, remains poorly understood. Working with a simplified numerical model of tumour spheroids, we investigated the impact of mechanical heterogeneity on the onset of tumour invasion into surrounding tissues. Our work establishes a positive link between tumour heterogeneity and metastatic dissemination, and recapitulates a number of invasion patterns identified in vivo, such as multicellular finger-like protrusions. Two complementary mechanisms are at play in heterogeneous tumours. A small proportion of stronger cells are able to initiate and lead the escape of cells, while collective effects in the bulk of the tumour provide the coordination required to sustain the invasive process through multicellular streaming. This suggests that the multicellular dynamics observed during metastasis is a generic feature of mechanically heterogeneous cell populations and might rely on a limited and generic set of attributes.
A biomechanical switch regulates the transition towards homeostasis in oesophageal epithelium.
Epithelial cells rapidly adapt their behaviour in response to increasing tissue demands. However, the processes that finely control these cell decisions remain largely unknown. The postnatal period covering the transition between early tissue expansion and the establishment of adult homeostasis provides a convenient model with which to explore this question. Here, we demonstrate that the onset of homeostasis in the epithelium of the mouse oesophagus is guided by the progressive build-up of mechanical strain at the organ level. Single-cell RNA sequencing and whole-organ stretching experiments revealed that the mechanical stress experienced by the growing oesophagus triggers the emergence of a bright Krüppel-like factor 4 (KLF4) committed basal population, which balances cell proliferation and marks the transition towards homeostasis in a yes-associated protein (YAP)-dependent manner. Our results point to a simple mechanism whereby mechanical changes experienced at the whole-tissue level are integrated with those sensed at the cellular level to control epithelial cell fate.
Theory of mechanochemical patterning in biphasic biological tissues.
The formation of self-organized patterns is key to the morphogenesis of multicellular organisms, although a comprehensive theory of biological pattern formation is still lacking. Here, we propose a minimal model combining tissue mechanics with morphogen turnover and transport to explore routes to patterning. Our active description couples morphogen reaction and diffusion, which impact cell differentiation and tissue mechanics, to a two-phase poroelastic rheology, where one tissue phase consists of a poroelastic cell network and the other one of a permeating extracellular fluid, which provides a feedback by actively transporting morphogens. While this model encompasses previous theories approximating tissues to inert monophasic media, such as Turing's reaction-diffusion model, it overcomes some of their key limitations permitting pattern formation via any two-species biochemical kinetics due to mechanically induced cross-diffusion flows. Moreover, we describe a qualitatively different advection-driven Keller-Segel instability which allows for the formation of patterns with a single morphogen and whose fundamental mode pattern robustly scales with tissue size. We discuss the potential relevance of these findings for tissue morphogenesis.
On growth and force: mechanical forces in development.
The EMBO/EMBL Symposium 'Mechanical Forces in Development' was held in Heidelberg, Germany, on 3-6 July 2019. This interdisciplinary symposium brought together an impressive and diverse line-up of speakers seeking to address the origin and role of mechanical forces in development. Emphasising the importance of integrative approaches and theoretical simulations to obtain comprehensive mechanistic insights into complex morphogenetic processes, the meeting provided an ideal platform to discuss the concepts and methods of developmental mechanobiology in an era of fast technical and conceptual progress. Here, we summarise the concepts and findings discussed during the meeting, as well as the agenda it sets for the future of developmental mechanobiology.
Deep learning for bioimage analysis in developmental biology.
Deep learning has transformed the way large and complex image datasets can be processed, reshaping what is possible in bioimage analysis. As the complexity and size of bioimage data continues to grow, this new analysis paradigm is becoming increasingly ubiquitous. In this Review, we begin by introducing the concepts needed for beginners to understand deep learning. We then review how deep learning has impacted bioimage analysis and explore the open-source resources available to integrate it into a research project. Finally, we discuss the future of deep learning applied to cell and developmental biology. We analyze how state-of-the-art methodologies have the potential to transform our understanding of biological systems through new image-based analysis and modelling that integrate multimodal inputs in space and time.
A magnetically actuated, optically sensed tensile testing method for mechanical characterization of soft biological tissues.
Mechanical properties of soft biological tissues play a critical role in physiology and disease, affecting cell behavior and fate decisions and contributing to tissue development, maintenance, and repair. Limitations of existing tools prevent a comprehensive characterization of soft tissue biomechanics, hindering our understanding of these fundamental processes. Here, we develop an instrument for high-fidelity uniaxial tensile testing of soft biological tissues in controlled environmental conditions, which is based on the closed-loop interaction between an electromagnetic actuator and an optical strain sensor. We first validate the instrument using synthetic elastomers characterized via conventional methods; then, we leverage the proposed device to investigate the mechanical properties of murine esophageal tissue and, individually, of each of its constitutive layers, namely, the epithelial, connective, and muscle tissues. The enhanced reliability of this instrument makes it an ideal platform for future wide-ranging studies of the mechanics of soft biological tissues.
Dynamic regulation of tissue fluidity controls skin repair during wound healing.
During wound healing, different pools of stem cells (SCs) contribute to skin repair. However, how SCs become activated and drive the tissue remodeling essential for skin repair is still poorly understood. Here, by developing a mouse model allowing lineage tracing and basal cell lineage ablation, we monitor SC fate and tissue dynamics during regeneration using confocal and intravital imaging. Analysis of basal cell rearrangements shows dynamic transitions from a solid-like homeostatic state to a fluid-like state allowing tissue remodeling during repair, as predicted by a minimal mathematical modeling of the spatiotemporal dynamics and fate behavior of basal cells. The basal cell layer progressively returns to a solid-like state with re-epithelialization. Bulk, single-cell RNA, and epigenetic profiling of SCs, together with functional experiments, uncover a common regenerative state regulated by the EGFR/AP1 axis activated during tissue fluidization that is essential for skin SC activation and tissue repair.