Biology subjects

Bar-Nur, O.

Publications and source records attributed to Bar-Nur, O..

9 recordsLinked to original sources

bioRxiv2026

Stimulatrix: An open-source automated platform for high-throughput functional characterization of engineered contractile tissues

Engineered cardiac and skeletal muscle tissues suspended between flexible posts support disease modeling and pharmacology, yet their stimulation, longitudinal imaging and quantitative analysis often remain fragmented and labor-intensive. Here we present Stimulatrix, an open-source platform integrating automated video acquisition within a cell culture incubator, synchronized electrical stimulation and deep learning for longitudinal assessment of contractile tissues in multiwell plates. The platform quantifies tissue compaction, force generation and contraction kinetics with optional cloud processing reducing dependence on local GPU hardware. We demonstrate the workflow in cardiac tissues comprising human induced pluripotent stem cell-derived cardiomyocytes and cardiac fibroblasts, and in primary human skeletal muscle constructs. Force and kinetic measurements were benchmarked against manual annotations. Longitudinal profiling resolved responses to matrix composition and pacing regimens and tracked doxorubicin-associated loss of cardiac contractile force. Stimulatrix provides an accessible workflow for automated functional phenotyping of engineered muscle tissues.

bioengineering↗

bioRxiv2025

Prolonged cell encapsulation and rapid filamented light biofabrication of muscle constructs in microgravity

The prospects of fabricating human tissue grafts or models using cell-laden bioresins in space has garnered significant interest in recent years. While there has been tremendous progress in extrusion or light-based bioprinting in microgravity conditions, printing of aligned tissues, such as those featuring anisotropic organization of cells and extracellular matrices (e.g., muscle, tendon, cardiac, etc.), remains a challenge. Furthermore, current photoresin formulations do not allow long-term cell encapsulation and are difficult to perform in microgravity. In this study, we demonstrate a new gravity-independent filamented light (G-FLight) biofabrication system with in-built refrigeration and heating units, which can create viable muscle constructs within seconds. We developed new photoresin formulations based on gelatin methacrylate (GelMA) for encapsulation of primary cells (murine myoblasts) and storage in printing cuvettes for at least a week at 4{degrees}C or -80{degrees}C. The tissues printed in microgravity based on the new formulations exhibited higher cell viability, number of proliferating cells and after maturation higher numbers of myotubes and fusion index compared to control formulations (i.e., GelMA dissolved in phosphate buffered saline). The microgravity-printed tissues also featured similar myotube density and fusion index to those printed using the same resins on-ground. The G-Flight printing concept, together with the new resins enabling refrigeration or cryopreservation with encapsulated cells, offers a promising solution for biofabrication in space.

bioengineering↗

bioRxiv2025

Filamented Light (FLight) Bioprinting of Mini-Muscles with Self-Renewal Potential

The plasticity and regenerative capacity of skeletal muscle arise from quiescent stem cells activated upon overload, injury, or inflammation. Developing in vitro muscle models to study these properties could advance muscle disease modeling and pre-clinical evaluation. Here, we leverage Filamented Light (FLight) bioprinting as a high-throughput approach for producing mini-muscle tissues. Using Pax7-nGFP myoblasts, we bioprinted mini-muscles from pristine collagen-fibrinogen. The FLight hydrogel consisted of aligned microstructures which guided the formation of aligned myotubes. Mini-muscles demonstrated in vivo-like tissue organization, including highly aligned myotubes and a Pax7+ cell pool embedded in newly deposited laminin. Both spontaneous and electrically stimulated contractions were observed. Collagen-fibrinogen matrix was promising for maintenance of the Pax7+ cell pool. Damage from cardiotoxin-induced injury of the mini-muscles led to a massive proliferation of Pax7+ cells and restoration of the contractile properties. Notably, small molecules such as Repsox could enhance regeneration. FLight printed mini-muscles have potential for applications in muscle biology, exercise/atrophy, disease models, and drug screening.

bioengineering↗

bioRxiv2025

Delivery of a chemically modified noncoding RNA domain improves dystrophic myotube function

Fast twitch, type II muscle fibers are particularly prone to degradation in skeletal muscle pathologies, such as sarcopenia and muscular dystrophies. We previously showed that endogenous activation of the exercise-induced long noncoding RNA CYTOR promotes fast-twitch myogenesis. In the present study, we identify an independent pro-myogenic element within human CYTOR and optimize its RNA delivery. In human primary myoblasts exogenous, vector-based CYTORexon 2 recapitulates the effect of full-length CYTOR by enhancing fast-twitch myogenic differentiation. Furthermore, chemically modified CYTORexon 2 RNA{Psi}U (N1-me-PseudoU, 7-methyl guanosine 5Cap, polyA tail) enhanced RNA stability and reduced the immunogenic response to CYTORexon 2 RNA. We demonstrate that viral- or chemically optimized RNA-mediated CYTORexon 2 administration enhances the commitment towards myogenic maturation in Duchenne muscular dystrophy-derived primary myoblasts, induced myogenic progenitor cells and mouse embryonic stem cells. Furthermore, chemically optimized CYTORexon 2 improves key disease characteristics in dystrophic myotubes, including calcium handling and mitochondrial bioenergetics. In summary, our findings identify CYTOR exon 2 as the pro-myogenic domain of CYTOR that can be delivered in a disease context using chemical modifications. This is of particular importance given the susceptibility of type II muscle fibers in different muscle pathologies such as aging and dystrophies, and the reported oncogenic effect of CYTOR exon 1. Our study, therefore, highlights the potential of identifying functional domains in noncoding RNAs. Delivery, or targeting of such RNA domains could constitute next-generation RNA therapeutics.

bioengineering↗

bioRxiv2023

GLUD1 dictates muscle stem cell differentiation by controlling mitochondrial glutamate levels

Muscle stem cells (MuSCs) enable muscle growth and regeneration after exercise or injury. Upon activation MuSCs metabolically rewire to meet the changing demands of proliferation. Here we describe that primary changes in metabolism itself can dictate MuSC fate decisions to control differentiation and fusion. We found that glutamine anaplerosis into the TCA cycle decreases during MuSC differentiation and coincides with decreased expression of the mitochondrial glutamate deaminase GLUD1. Genetic deletion of Glud1 in proliferating MuSCs resulted in precocious differentiation and imbalanced fusion combined with loss of self-renewal in vitro and in vivo. Mechanistically, deleting Glud1 caused mitochondrial glutamate accumulation in proliferating MuSCs and inhibited the malate-aspartate shuttle (MAS). Restoring MAS activity by supplementation of alanine normalized differentiation. In conclusion, high GLUD1 activity in proliferating MuSCs prevents deleterious mitochondrial glutamate accumulation and inactivation of the MAS. It thereby acts as a compartment specific metabolic brake on MuSC differentiation. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=194 SRC="FIGDIR/small/560525v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@e3585dorg.highwire.dtl.DTLVardef@1be4a54org.highwire.dtl.DTLVardef@1f077org.highwire.dtl.DTLVardef@15220f1_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIGlutamine is the major TCA cycle substrate in MuSCs with decreasing contribution upon differentiation. C_LIO_LILoss of Glud1 impairs MuSC self-renewal capacity and causes imbalanced fusion in vitro and in vivo. C_LIO_LIGlud1 deletion leads to mitochondrial glutamate trapping and malate-aspartate shuttle (MAS) dysfunction. C_LIO_LIRestoration of MAS activity in Glud1 deficient MuSCs reverses precocious differentiation and imbalanced fusion. C_LI

cell biology↗

bioRxiv2023

Interspecies generation of functional muscle stem cells

Satellite cells, the stem cells of skeletal muscle tissue, hold a prodigious regeneration capacity. However, low satellite cell yield from autologous or donor-derived muscles precludes adoption of satellite cell transplantation for the treatment of muscle diseases including Duchenne muscular dystrophy (DMD). To address this limitation, here we investigated whether sufficient quantity of satellite cells can be produced in allogeneic or xenogeneic animal hosts. First, we report on exclusive satellite cell production in intraspecies mouse chimeras by injection of CRISPR/Cas9-corrected DMD-induced pluripotent stem cells (iPSCs) into blastocysts carrying an ablation system of host Pax7+ satellite cells. Additionally, injection of genetically-corrected DMD-iPSCs into rat blastocysts produced interspecies rat-mouse chimeras harboring mouse muscle stem cells that efficiently restored dystrophin expression in DMD mice. This study thus provides a proof-of-principle for the generation of therapeutically-competent stem cells between divergent species, raising the possibility of procuring human stem cells in large animals for regenerative medicine purposes.

cell biology↗

bioRxiv2023

A self-renewing biomimetic skeletal muscle construct engineered using induced myogenic progenitor cells

Skeletal muscle is a highly organized and regenerative tissue that maintains its homeostasis primarily by activation and differentiation of muscle stem cells. Mimicking an in vitro skeletal muscle differentiation program that contains self-renewing adult muscle stem cells and aligned myotubes has been challenging. Here, we set out to engineer a biomimetic skeletal muscle construct that can self-regenerate and produce aligned myotubes using induced myogenic progenitor cells (iMPCs), a heterogeneous culture consisting of skeletal muscle stem, progenitor and differentiated cells. Utilizing electrospinning, we fabricated polycaprolactone (PCL) substrates that enabled iMPC-differentiation into aligned myotubes by controlling PCL fiber orientation. Newly-conceived constructs contained highly organized multinucleated myotubes in conjunction with self-renewing muscle stem cells, whose differentiation capacity was augmented by Matrigel supplementation. Additionally, we demonstrate using single cell RNA-sequencing (scRNA-seq) that iMPC-derived constructs faithfully recapitulate a step-wise myogenic differentiation program. Notably, when the constructs were subjected to a damaging myonecrotic agent, self-renewing muscle stem cells rapidly differentiated into aligned myotubes, akin to skeletal muscle repair in vivo. Taken together, we report on a novel in vitro system that mirrors myogenic regeneration and muscle fiber alignment, and can serve as a platform to study myogenesis, model muscular dystrophies or perform drug screens.

bioengineering↗

bioRxiv2021

Integrative molecular roadmap for direct conversion of fibroblasts into myocytes and myogenic progenitor cells

Transient MyoD overexpression in concert with small molecules treatment reprograms mouse fibroblasts into induced myogenic progenitor cells (iMPCs). However, the molecular landscape and mechanisms orchestrating this cellular conversion remain unknown. Here, we undertook an integrative multi-omics approach to delineate the process of iMPC reprogramming in comparison to myogenic transdifferentiation mediated solely by MyoD. Utilizing transcriptomics, proteomics and genome-wide chromatin accessibility assays, we unravel distinct molecular trajectories which govern the two processes. Notably, iMPC reprogramming is characterized by gradual upregulation of stem and progenitor cell markers, unique signaling pathways, chromatin remodelers and cell cycle regulators which manifest via rewiring of the chromatin in core myogenic promoters. Furthermore, we determine that only iMPC reprogramming is mediated by Notch pathway activation, which is indispensable for iMPC formation and self-renewal. Collectively, this study charts divergent molecular blueprints for myogenic transdifferentiation or reprogramming and underpins the heightened capacity of iMPCs in capturing myogenesis ex vivo.

cell biology↗

bioRxiv2020

Exercise promotes satellite cell contribution to myofibers in a load-dependent manner

Satellite cells (SCs) are required for muscle repair following injury and are involved in muscle remodeling upon muscular contractions. Exercise stimulates SC accumulation and myonuclear accretion. To what extent exercise training at different mechanical loads drive SC contribution to myonuclei however is unknown. By performing SC fate tracing experiments, we show that 8-weeks of voluntary wheel running increased SC contribution to myonuclei in mouse plantar flexor muscles in a load-dependent but fiber type-independent manner. Increased SC fusion however was not exclusively linked to muscle hypertrophy as wheel running without external load substantially increased SC fusion in the absence of fiber hypertrophy. Due to nuclear propagation, nuclear fluorescent fate tracing mouse models were inadequate to quantify SC contribution to myonuclei. Ultimately, by performing fate tracing at the DNA level, we show that SC contribution mirrors myonuclear accretion during exercise. Collectively, these findings provide direct evidence that mechanical load during exercise independently promotes SC contribution to existing myofibers.

cell biology↗