Biology subjects

Hinton, A. O.

Publications and source records attributed to Hinton, A. O..

3 recordsLinked to original sources

bioRxiv2025

Artificial intelligence-enabled automated analysis of transmission electron micrographs to evaluate chemotherapy impact on mitochondrial morphology in triple negative breast cancer

Advancements in transmission electron microscopy (TEM) have enabled in-depth studies of biological specimens, offering new avenues to large-scale imaging experiments with subcellular resolution. Mitochondrial structure is of growing interest in cancer biology due to its crucial role in regulating the multi-faceted functions of mitochondria. We and others have established the crucial role of mitochondria in triple-negative breast cancer (TNBC), an aggressive subtype of breast cancer with limited therapeutic options. Building upon our previous work demonstrating the functional role of mitochondrial structure dynamics in the metabolic adaptations and survival of chemotherapy-refractory TNBC cells, we sought to extend those findings to a large-scale analysis of transmission electron micrographs. Here we present a novel U-Net artificial intelligence (AI) model for automatic annotation and assessment of mitochondrial morphology and feature quantification. Our model is trained on 11,039 manually annotated mitochondria across 125 micrographs derived from a variety of orthotopic patient-derived xenograft (PDX) mouse model tumors and adherent cell cultures. The model achieves an F1 score of 0.85 on test micrographs at the pixel level. To validate the ability of our model to detect expected mitochondrial structural changes, we utilized micrographs from mouse primary skeletal muscle cells genetically modified to lack Dynamin-related protein 1 (Drp1). We subjected in vitro and in vivo TNBC models to conventional chemotherapy treatments commonly used for clinical management of TNBC, including doxorubicin, carboplatin, paclitaxel, and docetaxel (DTX). We found substantial within-sample heterogeneity of mitochondrial structure in both in vitro and in vivo TNBC models. In four of five PDX models, in vivo treatment with DTX elicited significant alteration in mitochondrial elongation and/or area. We went on to compare mammary tumors and matched lung metastases in a highly metastatic PDX model of TNBC, uncovering significant increase in mitochondrial elongation in metastatic lesions compared to their matched primary mammary tumor. The successful application of our AI model to capture mitochondrial structure marks a step forward in high-throughput analysis of mitochondrial structures, enhancing our understanding of how morphological changes may relate to chemotherapy efficacy and mechanism of action. Our large, manually curated electron micrograph dataset - now publicly available - serves as a unique resource for developing, benchmarking, and applying computational models, while further advancing investigations into mitochondrial morphology and its impact on breast cancer biology. This study provides proof of concept that mitochondrial structural remodeling is an additional layer of cellular reprogramming accompanying therapeutic resistance TNBC that merits further investigation.

cancer biology↗

bioRxiv2024

Changes in Myofibril Size, Shape, and Network Connectivity in Aging Muscle

Across normal aging, striated muscles undergo structural remodeling associated with loss of force production. However, it is unknown how the organization of contractile myofibrillar networks, linked to their efficiency, is modified during aging. Using serial block-face scanning electron microscopy (SBF-SEM), we assess myofibril size, shape, and connectivity across different muscle types in young and geriatric mice and humans. Regardless of skeletal muscle fiber type in mice, age was associated with increased myofibrillar connectivity, with 24 months of age, as compared to 3 months, displaying more sarcomere branches. Distinctive age-related trends in myofibril size and shape were observed among each muscle type. Notably, there was a decrease in myofibril circularity from 3 months of age to 24 months of age in the gastrocnemius muscles of mice, contrasting with an increase in circularity in the soleus muscles during the same time frame. Additionally, while the soleus myofibrils in an aged cohort had a higher cross-sectional area, a reduction was observed in the gastrocnemius muscles. Cardiac muscles displayed no changes in sarcomere connectivity from 3 months to 24 months, although myofibril circularity and cross-sectional area were increased during this time. In human vastus lateralis muscles, sarcomere branching was positively correlated with advanced age. However, there were no consistent changes in myofibril size or shape across a wide age range from 16 to 68 years old. Overall, these data suggest that aging is associated with increased connectivity of the contractile networks within mammalian skeletal muscle. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=119 SRC="FIGDIR/small/615981v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@1b06d92org.highwire.dtl.DTLVardef@1e99c7eorg.highwire.dtl.DTLVardef@2151b3org.highwire.dtl.DTLVardef@17ac3f7_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2022

Nitroimidazopyrazinones with oral activity against tuberculosis and Chagas disease in mouse models of infection

Tuberculosis remains one of the leading causes of death from a single infectious agent, surpassing both AIDS and malaria. In recent years, two bicyclic nitroimidazole drugs, delamanid and pretomanid have been approved to treat this airborne infection. This has spurred a renewed interest in developing new and improved nitroimidazole analogs. We have previously identified a new bicyclic heteroaromatic subclass, the nitroimidazopyrazinones, with substituted analogs showing promising activity against Mycobacterium tuberculosis under both aerobic and hypoxic environments. A second generation of nitroimidazopyrazinones with extended biaryl side chain also possessed good antiparasitic activity against Trypanosoma brucei brucei and Trypanosoma cruzi, suggesting the utility of this new scaffold for development into potential candidates against both tuberculosis and the kinetoplastid parasites which cause neglected tropical diseases. In this study, we further evaluated the properties of nitroimidazopyrazinone derivatives by assessing their selectivity against different mycobacterial species, measuring their reduction potential, and determining the kinetic parameters as substrates of the deazaflavin-dependent nitroreductase (Ddn), which is the activating enzyme of delamanid and pretomanid in M. tuberculosis. We also conducted an in vivo evaluation of a lead compound, MCC8967 that demonstrated a favorable pharmacokinetic profile, with good oral bioavailability and efficacy in an acute M. tuberculosis infection model. Two other promising compounds MCC9481 and MCC9482, with good in vitro activity (IC50 = 0.016 and 0.10 {micro}M, respectively) against T. cruzi, the causative agent for Chagas diseases, were similarly tested for in vivo activity. These compounds also exhibited good oral bioavailability, and transiently reduced the acute-stage parasite burden by >98-99% at doses of 50 mg/kg once or twice daily, similar to benznidazole at 100 mg/kg once daily. Overall, we have demonstrated that active nitroimidazopyrazinones have potential to be developed as clinical candidates against both tuberculosis and Chagas disease. Author SummaryTuberculosis and parasitic infections continue to impose a significant threat to public health and economic growth worldwide. Most of the efforts to control these diseases still rely on drug treatments with limited effectiveness and significant side effects. There is now an urgent need to develop new treatments to combat these infections. Here, we report the in vitro and in vivo profile of a new bicyclic nitroimidazole subclass, namely nitroimidazopyrazinones, against mycobacteria and Trypanosoma cruzi. We found that derivatives with monocyclic side chains are selective against Mycobacterium tuberculosis, the causative agent of tuberculosis, but not active against other nontuberculosis mycobacteria. In an acute mouse model, they were able to reduce the bacterial load in lungs via oral administration. From a biochemistry perspective, we demonstrated that deazaflavin-dependent nitroreductase (Ddn) could act effectively on nitroimidazopyrazinones, indicating the potential of Ddn as an activating enzyme for these new compounds in M. tuberculosis. We also showed that derivatives with extended biaryl side chain were effective in suppressing infection in an acute T. cruzi infected murine model, with satisfactory oral bioavailability. These findings improve the understanding of the biological profile of nitroimidazopyrazinones for further development as potential antitubercular and antiparasitic agents.

pharmacology and toxicology↗