Cree, T. | bioRxiv Science

bioRxiv2026

High-throughput screening in hiPSC-cardiac models reveals cardiomyocyte-specific cell cycle regulatory mechanisms

Introductory ParagraphMultiple regulatory mechanisms govern cardiomyocyte proliferation including epigenetic modifications, metabolism and mechanical load. However, it is unclear whether such mechanisms can be pharmacologically targeted to induce cardiomyocyte proliferation without affecting other cell types. Here, we develop a dual-reporter (TNNT2eGFP; PCNAmScarlet-I) and a high-throughput image-based pipeline in human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes, with counter screening in non-myocytes, to identify compounds that selectively promote cardiomyocyte proliferation without affecting other cell types. We identify the PIM kinase inhibitor GDC-0339 as a cardiomyocyte-selective pro-proliferative compound. GDC-0339 induced proliferation of hiPSC-derived cardiomyocytes without activity in non-myocytes, non-cardiac fibroblasts or epithelial cells. Phosphoproteomic profiling of GDC-0339 in cardiomyocytes and non-cardiac fibroblasts revealed a cardiomyocyte-specific mechanism of action involving sarcomere disassembly via remodelling of the F-actin cytoskeleton and metabolic reprogramming to anaerobic metabolism via Pyruvate Dehydrogenase Kinases (PDKs). Thus, we uncover cardiomyocyte-specific mechanisms governing the cell cycle that are potentially druggable.

cell biology↗

bioRxiv2026

Ageing blunts the phospho-proteomic response to resistance exercise in humans

Ageing blunts the adaptive growth response in human skeletal muscle. To define the molecular processes underlying this impairment, we performed unbiased analysis of the phosphoproteome and total proteome in healthy young and old human skeletal muscle following acute resistance exercise (ResEX) and essential amino acid (EAA) ingestion. Ageing led to global suppression of the growth-induced global phosphoproteome, despite intact mTORC1 activation in old muscle. Our results identify widespread effects of ageing on skeletal muscle growth and highlight novel pathways for therapeutic development in aged skeletal muscle.

physiology↗

bioRxiv2025

Mitochondrial uncoupler BAM15 improves skeletal muscle function and mitochondrial respiration in Sarcopenia

BackgroundAgeing is accompanied by progressive declines in skeletal muscle mass and strength, culminating in sarcopenia, a condition that contributes to frailty, multimorbidity, and mortality. Age-related changes to mitochondria lead to oxidative damage and dysfunction and are proposed to occur early in the trajectory of sarcopenia, supporting the candidacy of mitochondrial-protective therapies. Here, we test the efficacy of mitochondrial uncoupler BAM15 in age-dependent sarcopenic mouse models. MethodsMale and female MitoQC mice aged 24 months received either standard chow or chow supplemented with BAM15 (0.033% mg/g) ad libitum for eight weeks (n=13-14/group). Young (3-month-old) mice served as reference controls (n=8/group). Muscle mitochondrial respiration was assessed in permeabilized fib res, and contractile function was measured in isolated extensor digitorum longus and soleus muscles. Mitophagy was quantified by immunofluorescence confocal microscopy. Data were analyzed using one-or two-way ANOVA followed by Dunnetts or Bonferronis multiple comparison tests. ResultsAged male and female mice exhibited reduced gastrocnemius muscle mass relative to body mass compared with young controls (p<0.05; [~]18% and [~]32% loss, respectively). BAM15 did not alter muscle size but reversed the age-related loss of contractile function in EDL muscles, to that of the young reference controls in both sexes (p<0.05; [~]33% in males, [~]16% in females). In male mice, BAM15 improved mitochondrial efficiency, evidenced by restoration of Complex I-linked respiration and decreased proton leak ([~]52% improvement; p<0.05), and normalized protein levels of oxidative stress marker 4 -HNE, without changes in mitophagy or mitochondrial content. In females, BAM15 did not improve mitochondrial parameters, which may be, in part, due to aged female muscle exhibiting unchanged Complex I leak and 4-HNE protein abundance, alongside lower complex I subunit (NDUFB8) protein abundance. ConclusionsBAM15 improved skeletal muscle mitochondrial efficiency and contractile function in aged male mice, supporting the potential of mitochondrial uncoupling as a therapeutic strategy for sarcopenia.

physiology↗