Biology subjects

Costello, P.

Publications and source records attributed to Costello, P..

4 recordsLinked to original sources

bioRxiv2026

The MRTFs are required for thymocyte trafficking and Treg-mediated immune tolerance

The MRTFs (myocardin-related transcription factors) are essential for effective cytoskeletal function during differentiation and development. To investigate the role played by the MRTFs in T cell development and function we inactivated Mrtfb in Mrtfa-null mice at the DN2 stage (MrtfabKOT animals). Positive selection, and development of MrtfabKOT regulatory (Treg), {gamma}{delta}, and NK T cells proceeded normally. Thymic egress was impaired, however, with mature T cells accumulating at the cortico-medullary junction, and in vitro MrtfabKOT thymocytes exhibited impaired cytoskeletal responses to S1P and migratory cytokines. MrtfabKOT mice were lymphopenic, with defective homeostatic proliferation and T cell homing to peripheral lymphoid organs. Although thymocyte negative selection was unaffected, MrtfabKOT animals develop autoimmune phenotypes in lacrimal gland and intestinal mucosa. Using the experimental colitis model, we show that these phenotypes reflect functional deficits in MrtfabKOT Treg cells. Our findings show that MRTF-SRF signalling plays an unanticipated role in thymocyte egress and immune tolerance, and reveal a role of the MRTFs in Treg function.

immunology↗

bioRxiv2026

Functional Assessment of Cardiac Beat Dynamics Under Dynamic Flow: Insights from the Mera Microphysiological System

Cardiac rhythm is a critical clinical indicator for cardiac arrhythmias and adverse events during drug toxicity studies. In vivo, cardiomyocyte responses to pharmacological agents occur within minutes and are strongly influenced by dynamic drug delivery through blood flow. However, conventional 2D and 3D static culture systems fail to replicate these fluid flow kinetics, limiting their physiological relevance for assessing beat rate responses. Here, we present Mera, an advanced microphysiological system (MPS) developed by Hooke Bio, designed for high-throughput, long-term culture and functional analysis of 3D cardiac spheroids composed of human induced pluripotent stem cell-derived cardiomyocytes and cardiac fibroblasts. Mera enables dynamic perfusion, allowing investigation of cardiomyocyte beat rates under physiologically relevant flow conditions. The platform supports up to 640 spheroids per run and integrates automated imaging, fluid handling, and user-friendly software, operating under controlled physiological conditions (37{degrees}C, 5% CO2). Flow rates are tunable between 0 and 12.5 mL/min to mimic in vivo environments. Pharmacological testing with verapamil, isoproterenol, calcium chloride, and propranolol demonstrated real-time, reversible modulation of beat rate under flow, including recovery following drug-induced suppression. System variability was comparable to a temperature-controlled reference platform, supporting robust statistical analysis. Dose-response studies yielded IC values consistent with literature, confirming physiological relevance. Collectively, these results demonstrate that Mera provides a reproducible, scalable, and human-relevant platform for cardiac drug testing. By enabling dynamic drug exposure and automated analysis, Mera represents a powerful new approach methodology (NAM) for improving the predictive assessment of cardiac safety and beat-rate modulation drug responses.

bioengineering↗

bioRxiv2023

Defective cytoskeletal dynamics underlies the essential role of MRTF-SRF in IL-2 delivery to CD8+ T cells during infectious challenge

Paracrine IL-2 signalling underpins late primary CD8+ T cell expansion and differentiation that allow protection against viral infections, yet the requirements for effective delivery of IL-2 to recipient cells remain poorly understood. We show that the SRF transcription factor, a master regulator of cytoskeletal dynamics, is essential for the response to L. monocytogenes infection. SRF acts cell-autonomously with its actin-regulated MRTF cofactors Mrtfa and Mrtfb to sustain CD8+ effector T cell expansion and persistence of memory cells. MRTF-SRF activity is not required for initial TCR-mediated CD8+ T cell proliferation, but is necessary for subsequent IL-2 dependent expansion. Following TCR activation in vitro, Mrtfab-null CD8+ T cells produce IL-2 normally, but exhibit defective paracrine IL-2 signalling. Cluster formation by activated Mrtfab-null CD8+ T cells is impaired: clusters are smaller and less dense, have substantially reduced F-actin content, retain less IL-2, and exhibit defective cytoskeletal gene expression. Activated Mrtfab-null CD8+ T cells also exhibit defective homotypic clustering in vivo. The requirement for MRTF-SRF signalling for CD8+ T cell proliferation during infection thus reflects its involvement in cytoskeletal dynamics.

immunology↗

bioRxiv2022

Mera: A scalable high throughput automated micro-physiological system

There is an urgent need for scalable Microphysiological Systems (MPSs)1 that can better predict drug efficacy and toxicity at the preclinical screening stage. Here we present Mera, an automated, modular and scalable system for culturing and assaying microtissues with interconnected fluidics, inbuilt environmental control and automated image capture. The system presented has multiple possible fluidics modes. Of these the primary mode is designed so that cells may be matured into a desired microtissue type and in the secondary mode the fluid flow can be re-orientated to create a recirculating circuit composed of inter-connected channels to allow drugging or staining. We present data demonstrating the prototype system Mera using an Acetaminophen/HepG2 liver microtissue toxicity assay with Calcein AM and Ethidium Homodimer (EtHD1) viability assays. We demonstrate the functionality of the automated image capture system. The prototype microtissue culture plate wells are laid out in a 3 x 3 or 4 x 10 grid format with viability and toxicity assays demonstrated in both formats. In this paper we set the groundwork for the Mera system as a viable option for scalable microtissue culture and assay development.

bioengineering↗