Project description:Formation of oriented myofibrils is a key event in the development of a functional musculoskeletal system. However, the mechanisms that control orientation of myocytes, their fusion and the resulting directionality of adult muscles remain enigmatic. Here, we utilized in vivo and in vitro live imaging, CAS9/CRISPR-mediated mutagenesis in fish, genetic experiments in mice and single cell transcriptomics to demonstrate that individual myocyte polarization and subsequent orientation depend on cell stretch imposed by skeletal expansion. Our data revealed that upon migration, individual facial myocytes form unpolarized clusters corresponding to future muscle groups. These clusters undergo oriented stretch and alignment during embryonic growth. Experimental in vivo perturbations of cartilage shape, size and distribution caused disruptions in directionality and number of myofibrils. Controlled in vitro 2D and 3D experiments applying continuous tension via artificial attachment points demonstrated a sufficiency for mechanical forces to instruct coherent polarization of myocyte populations. Consistently, perturbations of cartilage extension revealed a role of the developing skeleton in the directional outgrowth of non-muscle soft tissues during limb and facial morphogenesis.
Project description:Formation of oriented myofibrils is a key event in the development of a functional musculoskeletal system. However, the mechanisms that control orientation of myocytes, their fusion and the resulting directionality of adult muscles remain enigmatic. Here, we utilized in vivo and in vitro live imaging, CAS9/CRISPR-mediated mutagenesis in fish, genetic experiments in mice and single cell transcriptomics to demonstrate that individual myocyte polarization and subsequent orientation depend on cell stretch imposed by skeletal expansion. Our data revealed that upon migration, individual facial myocytes form unpolarized clusters corresponding to future muscle groups. These clusters undergo oriented stretch and alignment during embryonic growth. Experimental in vivo perturbations of cartilage shape, size and distribution caused disruptions in directionality and number of myofibrils. Controlled in vitro 2D and 3D experiments applying continuous tension via artificial attachment points demonstrated a sufficiency for mechanical forces to instruct coherent polarization of myocyte populations. Consistently, perturbations of cartilage extension revealed a role of the developing skeleton in the directional outgrowth of non-muscle soft tissues during limb and facial morphogenesis.
Project description:During metastatic dissemination, circulating tumour cells (CTCs) enter capillary beds, where they experience mechanical constriction forces. A high-throughput microfluidic platform mimicking human capillaries to investigate the impact of mechanical constriction forces on malignant and normal breast cell lines was developed. Cells were collected after transiting the constrictions, followed by RNA extraction and sequencing. The non-malignant cell line experienced transcriptional changes, particularly downregulation of epithelial markers, while the metastatic cell lines showed minimal alterations.
Project description:Mechanical forces are essential for normal fetal lung development. However, the cellular and molecular mechanisms regulating this process remain largely unknown. In the present study, we used oligonucleotide microarray technology to investigate gene expression profile in cultured rat fetal lung type II epithelial cells exposed to a level of mechanical strain similar to that observed in utero. Significance Analysis of Microarrays (SAM) identified 92 genes differentially expressed by strain. Interestingly, several members of the solute carrier family of amino acid transporters, genes involved in amino acid synthesis and development, and amiloride-sensitive epithelial sodium channel gene were induced by strain. These results were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR). Thus, this study identifies genes induced by strain that may be important for amino acid signaling pathways, protein synthesis and development in fetal type II cells. In addition, these data suggest that mechanical forces may contribute to facilitate lung fluid reabsorption in preparation for birth. Taken together, the present investigation provides further insights into how mechanical forces may modulate fetal lung development.
Project description:Mechanical forces regulate cell behavior and tissue morphogenesis. In particular, cardiac tissues require mechanical stimuli generated by the heartbeat for differentiation and maturation, but the molecular mechanisms underlying these processes remain unclear. Here, we first show that mechanical forces acting via the mechanosensitive factor Vinculin (VCL) are essential for cardiomyocyte myofilament maturation and that cardiac contractility regulates the localization and activation of Vinculin. To further analyze the role of Vinculin in myofilament maturation, we examined its interactome in contracting cardiomyocytes and found many cytoskeletal factors including actinins. We also identified Slingshot protein phosphatase 1 (SSH1), which we show is recruited by Vinculin to regulate F-actin rearrangement and myofilament maturation through its association with the actin depolymerizing factor Cofilin (CFL). Together, our results reveal that mechanical forces generated by cardiac contractility regulate cardiomyocyte maturation through the VCL-SSH1-CFL axis, providing mechanistic insight into how mechanical forces are transmitted intracellularly to regulate myofilament maturation.
Project description:Mechanical forces are essential for normal fetal lung development. However, the cellular and molecular mechanisms regulating this process remain largely unknown. In the present study, we used oligonucleotide microarray technology to investigate gene expression profile in cultured E19 rat fetal lung type II epithelial cells exposed to a level of mechanical strain similar to that observed in utero. Significance Analysis of Microarrays (SAM) identified 92 genes differentially expressed by strain. Interestingly, several members of the solute carrier family of amino acid transporters, genes involved in amino acid synthesis and development, and amiloride-sensitive epithelial sodium channel gene were induced by strain. These results were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR). Thus, this study identifies genes induced by strain that may be important for amino acid signaling pathways, protein synthesis and development in fetal type II cells. In addition, these data suggest that mechanical forces may contribute to facilitate lung fluid reabsorption in preparation for birth. Taken together, the present investigation provides further insights into how mechanical forces may modulate fetal lung development. Keywords: lung development, fetal type II epithelial cells, strain response, microarray
Project description:Wolff’s law and the Utah Paradigm of skeletal physiology state that bone architecture adapts to mechanical loads. These models predict the existence of a mechanostat that links strain induced by mechanical forces to skeletal remodeling. However, how the mechanostat influences bone remodeling remains elusive. Here, we find that Piezo1 deficiency in osteoblastic cells leads to loss of bone mass and spontaneous fractures with increased bone resorption. Furthermore, Piezo1-deficient mice are resistant to further bone loss and bone resorption induced by hind limb unloading, demonstrating that PIEZO1 can affect osteoblast-osteoclast crosstalk in response to mechanical forces. At the mechanistic level, in response to mechanical loads, PIEZO1 in osteoblastic cells controls the YAP-dependent expression of type II and IX collagens. In turn, these collagen isoforms regulate osteoclast differentiation. Taken together, our data identify PIEZO1 as the major skeletal mechanosensor that tunes bone homeostasis.
Project description:In the vertebrate embryo, the eyes develop from optic vesicles that grow laterally outward from the brain tube and contact the overlying surface ectoderm. Within the region of contact, each optic vesicle and the surface ectoderm thicken to form placodes, which then invaginate to create the optic cup and lens pit, respectively. Eventually, the optic cup becomes the retina, while the lens pit closes to form the lens vesicle. Here, we review current hypotheses for the physical mechanisms that create these structures and present novel three-dimensional computer (finite-element) models to illustrate the plausibility and limitations of these hypotheses. Taken together, experimental and numerical results suggest that the driving forces for early eye morphogenesis are generated mainly by differential growth, actomyosin contraction, and regional apoptosis, with morphology mediated by physical constraints provided by adjacent tissues and extracellular matrix. While these studies offer new insight into the mechanics of eye development, future work is needed to better understand how these mechanisms are regulated to precisely control the shape of the eye.
Project description:Muscles’ function as an endocrine organ is still poorly understood, but an emerging body of literature has provided evidence that myokines may aid in the development of surrounding tissues. Another outcome of muscle contraction in vivo is the localized mechanical forces produced. Current experimental techniques are not equipped to isolate and study the two effects independently. We have developed a system to culture contractile 2D optogenetic muscle long-term to provide a source for myokine secretion. We supplement our neuron monoculture with myokine secreted media and saw a 3X increase in total neurite length magnitude and a 3.2X increase in the rate of growth. As for mechanical stimulation, we optimize our Magnetic Matrix Actuation (MagMA) to provide localized stressors on the growing neurites. The mechanical stimulation regime results in a ~2.7X increase in both magnitude and rate of total neurite length. We validate our morphological findings with bulk RNA-sequencing analysis, the results show a large number of differentially expressed genes between the biochemical stimulation group and control. On the other hand, there was minimal difference between the mechanical stimulation group and control. Our study mechanistically unravels how repeated muscle contraction, or exercise, regulates motor neuron growth and maturation.