Biology subjects

Zimmermann, W.

Publications and source records attributed to Zimmermann, W..

7 recordsLinked to original sources

bioRxiv2026

Force generation of cardiomyocytes in engineered environments

Cardiomyocyte contraction is essential for the pumping action of the heart and deteriorates after myocardial damage, either as a consequence of irreversible cardiomyocyte injury or stiffening of the extracellular matrix, a process described as fibrosis. Cell geometry and substrate stiffness not only influence sarcomere architecture and contractility, they also determine how much work the cardiomyocytes can transfer to their environment. Human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes provide a model system to examine these effects in a controlled manner, enabling us to mimic key features of the cardiac environment in vitro. Here we show that geometric confinement and substrate stiffness influence different aspects of cardiomyocyte force generation. By combining traction force microscopy and live-cell imaging of hiPSC-derived cardiomyocytes on soft and patterned substrates, we find that geometric confinement leads to longer resting sarcomeres and more pronounced sarcomere shortening on substrates with both physiological (10 kPa) and fibrotic (30 kPa) stiffness. Interestingly, the substrate stiffness itself has little effect on resting sarcomere length, but influences the peak contractile stress. On 10 kPa substrates, confined cells generate higher peak contractile stresses than unconfined cells, whereas this difference is not observed at 30 kPa. Confinement also results in faster mechanical relaxation at 10 kPa, with no detectable difference at 30 kPa. The combination of defined cell geometry and physiological stiffness leads to longer resting sarcomere lengths, more pronounced sarcomere shortening, higher peak contractile stress, and faster relaxation, features associated with a more mature cardiomyocyte phenotype. These findings show that the mechanical consequences of cell geometry depend on substrate stiffness and, therefore, both aspects have to be considered when employing hiPSC-derived cardiomyocytes as a model system in mechanobiology research, disease modeling and drug testing.

biophysics↗

bioRxiv2025

Peroxisome protein import deficiency causes heart failure in mouse and human

Peroxisomes are ubiquitous cellular organelles with potentially vital roles in lipid and reactive oxygen metabolism. The metabolic demands of the heart are substantial; however, the contribution of peroxisomes to cardiac development, health, and their role in heart failure (HF) remain largely unexplored. We developed and examined a mouse and an engineered human myocardium (EHM) model with a deficiency in cardiac peroxisome biogenesis to investigate the role of peroxisomes in cardiac function and pathology. In the EHM, loss of peroxisome protein import and subsequent peroxisomal metabolic impairment trigger mitochondrial damage and compromise cellular respiration and energy production. Peroxisome dysfunction results in incoherent electrical conduction, defective Ca2+-handling, and ultimately presentation of a HF phenotype with pathological force generation. These phenotypes are mirrored in an orthogonal murine model system with defective cardiac peroxisome biogenesis. Preload-dependent deficits in force generation due to insufficient energy supply are eventually fatal. Thus, peroxisomes play an important role in sustaining normal heart operations. Vice versa, peroxisome maintenance is compromised in pressure overload-induced HF, establishing peroxisomes as potential modulators of pathology and targets of therapy.

cell biology↗

bioRxiv2024

Degradation of PET plastic with engineered environmental bacteria

Polyethylene terephthalate (PET) is one of the most widely used plastic materials in the food and textile industry. Consequently, post-consumer PET waste is a common environmental pollutant that leaks into the environment in the form of macro and microplastics with concerning health impacts. There is a pressing need to identify novel and sustainable solutions to process the abundance of PET waste contributing to this pollution. While there is extensive research into enzymes able to hydrolyse PET in vitro, a similar solution for discarded or difficult-to-collect PET based on whole-cell microbial catalysts is missing. In this work we report the engineering of environmental bacteria to use PET as a growth substrate. This was achieved by isolating a strain of Pseudomonas umsongensis able to use the PET monomer terephthalate as carbon source, engineering the strain to effectively secrete the high-activity PET hydrolase PHL7 through the addition of a recombinant TAT secretion leader sequence, and enhancing the bioavailability of PET by transforming it into an amorphous and macroporous structure by pre-treatment with an organic solvent. Our findings demonstrate the direct microbial consumption of PET, which could lead to improved and more sustainable upcycling strategies for this plastic.

synthetic biology↗

bioRxiv2024

Stochastic tug-of-war among sarcomeres mediates cardiomyocyte response to environmental stiffness

Cardiac contraction is driven by the collective action of cardiomyocytes, that contain parallel bundles of myofibrils consisting of linear chains of sarcomeres, the basic force-generating units. The dynamics of individual sarcomeres within intact cardiomyocytes remain incompletely understood. While most models assume uniform, synchronized contractions, recent studies hint at unexpected heterogeneity whose origins and significance are not yet clear. By combining the culture of fluorescent sarcomere-reporter hiPSC-derived cardiomyocytes on micropatterned soft gels of different stiffness (5 - 85 kPa) with AI-based tracking of sarcomere motion, we found that increasingly stiff substrates inhibited overall cardiomyocyte contraction, but, surprisingly, did not diminish individual sarcomere dynamics. Instead, sarcomeres competed in a tug-of-war causing increasing heterogeneity, including rapid length oscillations and overextensions (popping). Statistical analysis showed that the heterogeneous dynamics were not caused by static structural differences but were largely stochastic. Stochastic heterogeneity is thus an intrinsic property of cardiac sarcomeres and likely mediates the adaptation of cardiomyocyte contractility to mechanical constraints. A mesoscopic model of coupled sarcomeres shows that these phenomena can be explained by a non-monotonic force-velocity relationship and stochastic fluctuations, where dynamic instability at a critical yielding force creates heterogeneity. Stochastic heterogeneity compensates for structural disorder by randomizing yield events beat-to-beat, preventing damage to specific sarcomeres. Our findings recast cardiac sarcomeres as active, dynamically unstable, and stochastic units engaged in a stochastic tug-of-war, where transient, velocity-dependent forces dominate. We propose that pathological disorder in cardiomyopathy drives a transition from protective stochastic fluctuations to more deterministic, persistently overloaded sarcomeres.

biophysics↗

bioRxiv2023

Two waves of evolution in the rodent pregnancy-specific glycoprotein (PSG) gene family lead to structurally diverse PSGs

The evolution of pregnancy-specific glycoproteins (PSGs) within the CEA gene family of primates correlates with the evolution of hemochorial placentation about 45 Myr ago. Thus, we hypothesized that hemochorial placentation with intimate contact between fetal cells and maternal immune cells favors the evolution and expansion of PSGs. With only a few exceptions, all rodents have hemochorial placentas thus the question arises whether PSGs evolved in most rodent genera. Analyzing genomic data of 94 rodent species we could identify PSGs only in three families of the suborder Myomorpha (characteristic species in brackets) namely in the Muridae (mouse), Cricetidae (hamster) and Nesomyidae (giant pouched rat) families. No PSGs were detected in the suborders Anomaluromorpha (springhare), Castorimorpha (beaver), Hystricognatha (guinea pig) and Sciuromorpha (squirrel). Thus, PSGs evolved only recently in Myomorpha shortly upon their most recent common ancestor (MRCA) has coopted the retroviral genes syncytin-A and syncytin-B which enabled the evolution of the three-layered trophoblast. This may suggest that the evolution of Psgs in rodents may have been favored by the challenge of the newly invented architecture of the maternal-fetal interface. In addition, a second hallmark of rodent PSG evolution seems to be the translocation of genes from the CEA gene family locus into a unique genomic region. Rodents without PSGs do not have any CEA-related genes in this locus. In contrast, rodent species in which PSGs evolved have lost ITAM-encoding CEACAM genes indicating that such a gene was translocated and thereby destroyed to form the new rodent PSG locus. This locus contains at least one Psg and Ceacam9 indicating that one of them was the founder gene of rodent Psgs. These genes are composed of various numbers of IgV-like domains (N domains) and one carboxy-terminal IgC-like domain of the A2-type. In a second wave of gene amplification in the PSG locus a gene encoding a protein composed of two N domain gave rise to four genes in mice (Ceacam11-14). In light of the divergent structure of PSGs in various mammalian species, we hypothesized that the Ceacam11-14 encode also functional PSGs and indeed we found that they are preferentially expressed by spongiotrophoblast cells, like Psg genes.

evolutionary biology↗

bioRxiv2021

Human engineered skeletal muscle of hypaxial origin from pluripotent stem cells with advanced function and regenerative capacity

Human pluripotent stem cell derived muscle models show great potential for translational research. Here, we describe developmentally inspired methods for derivation of skeletal muscle cells and their utility in three-dimensional skeletal muscle organoid formation as well as skeletal muscle tissue engineering. Key steps include the directed differentiation of human pluripotent stem cells to embryonic muscle progenitors of hypaxial origin followed by primary and secondary fetal myogenesis into hypaxial muscle with development of a satellite cell pool and evidence for innervation in vitro. Skeletal muscle organoids faithfully recapitulate all steps of embryonic myogenesis in 3D Tissue engineered muscle exhibits organotypic maturation and function, advanced by thyroid hormone. Regenerative competence was demonstrated in a cardiotoxin injury model with evidence of satellite cell activation as underlying mechanism. Collectively, we introduce a hypaxial muscle model with canonical properties of bona fide skeletal muscle in vivo to study muscle development, maturation, disease, and repair.

cell biology↗

bioRxiv2020

Bio-upcycling of polyethylene terephthalate

Over 359 million tons of plastics were produced worldwide in 2018, with significant growth expected in the near future, resulting in the global challenge of end-of-life management. The recent identification of enzymes that degrade plastics previously considered non-biodegradable opens up opportunities to steer the plastic recycling industry into the realm of biotechnology. Here, we present the sequential conversion of polyethylene terephthalate (PET) into two types of bioplastics: a medium chain-length polyhydroxyalkanoate (PHA) and a novel bio-based poly(amide urethane) (bio-PU). PET films were hydrolyzed by a thermostable polyester hydrolase yielding 100% terephthalate and ethylene glycol. A terephthalate-degrading Pseudomonas was evolved to also metabolize ethylene glycol and subsequently produced PHA. The strain was further modified to secrete hydroxyalkanoyloxy-alkanoates (HAAs), which were used as monomers for the chemo-catalytic synthesis of bio-PU. In short, we present a novel value-chain for PET upcycling, adding technological flexibility to the global challenge of end-of-life management of plastics. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=130 SRC="FIGDIR/small/993592v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1433e0dorg.highwire.dtl.DTLVardef@19efc71org.highwire.dtl.DTLVardef@cf97f7org.highwire.dtl.DTLVardef@101f123_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗