Biology subjects

Mitsui, T.

Publications and source records attributed to Mitsui, T..

5 recordsLinked to original sources

bioRxiv2025

Influence of Substrate Elastic Modulus on Cell Shape and Displacement During the Motility Cycle

Cardiac fibroblasts play a pivotal role in heart tissue dynamics, responding to mechanical cues from their environment. This study examines how substrate elasticity influences the motility and shape of chicken embryonic cardiac fibroblasts on polydimethylsiloxane (PDMS) substrates of different stiffness (10 kPa and 400 kPa). Using time-lapse phase-contrast microscopy, we identified distinct motility cycles characterized by elongation, contraction, and retraction phases. On soft substrates, cells exhibited slower retraction speeds and longer motility cycles compared to those on hard substrates. Notably, cells on soft substrates left trailing edges upon retraction, leading to pronounced morphological oscillations, whereas cells on hard substrates adopted near-circular shapes with less coordinated motility. Quantitative analyses revealed that the duration of the static phase was significantly shorter on hard substrates, correlating with differences in cell shape parameters, including length, circularity, and area. These findings suggest that substrate elasticity modulates the balance between cell-substrate adhesion and contractile forces, influencing cell polarity and motility. Our work advances the understanding of how mechanical environments shape fibroblast dynamics, offering insights relevant to tissue engineering and fibrosis research. SIGNIFICANCEMechanical cues from the cellular microenvironment are known to regulate cell behavior, yet how substrate stiffness shapes the dynamic motility cycle of fibroblasts remains incompletely understood. Here, we use high-resolution time-lapse imaging to reveal that cardiac fibroblasts on soft (10 kPa) PDMS undergo polarized, oscillatory migration with prolonged static phases, while those on stiff (400 kPa) substrates exhibit rapid retraction and random-like displacement with reduced polarity. These findings highlight how substrate elasticity modulates the interplay between traction forces and adhesion stability, governing directionality and morphology. This work provides mechanobiological insights into fibroblast behavior with implications for designing biomaterials to guide tissue remodeling and fibrosis progression.

biophysics↗

bioRxiv2025

Extracellular stiffness regulates cell fate determination and drives the emergence of evolutionary novelty in teleost heart

The diversification of life is driven by the acquisition of new phenotypic traits, known as evolutionary novelties. While some genetic mechanisms underlying such traits have been identified, the role of physical properties of cellular and extracellular components remains largely unexplored. Here, we show that the evolution and development of the bulbus arteriosus (BA)-a teleost-specific, smooth muscle-rich heart outflow tract-is regulated by the mechanical properties of its extracellular environment. Specifically, we demonstrate that the teleost-specific extracellular matrix gene elastin b confers the uniquely low stiffness of the BA. In contrast to the BA, the homologous organ in non-teleost actinopterygians, the conus arteriosus (CA), and the ventricle are predominantly composed of cardiomyocytes, and exhibit higher extracellular stiffness. Loss of elastin b function by knockdown or knockout leads to ectopic cardiomyocyte formation in the BA, accompanied by increased extracellular stiffness comparable to that of the ventricle. Furthermore, artificial stiffening of the BA extracellular environment is sufficient to induce ectopic cardiomyocyte differentiation. Taken together, these findings demonstrate that extracellular stiffness governs cell fate determination and highlight its role in the emergence of evolutionary novelties in the teleost heart. Significant StatementThe acquisition of new phenotypic traits is a key driver for a diversification of life. While genetic underpinnings of such traits have been well studied, the contribution of physical properties remains elusive. Here, we show that extracellular stiffness plays a key role in the evolution and development of the bulbus arteriosus (BA), a smooth muscle-based cardiac outflow tract unique to teleost hearts. We demonstrate that elastin b, a teleost-specific gene, confers characteristically low stiffness to the BA, which is required for proper cell fate determination. Notably, such low stiffness is absent in non-teleost fishes and in teleosts with impaired elastin b function, and artificial stiffening alters cell fate. Our findings highlight the importance of physical properties in driving evolutionary novelties.

developmental biology↗

bioRxiv2024

hoxb genes determine the timing of cell ingression by regulating cell surface fluctuations during zebrafish gastrulation

During embryonic development, cell behaviors need to be tightly regulated in time and space. Yet, how the temporal and spatial regulations of cell behaviors are interconnected during embryonic development remains elusive. To address this, we turned to zebrafish gastrulation, the process where dynamic cell behaviors generate the three principal germ layers of the early embryo. Here, we show that hoxb cluster genes are expressed in a temporally collinear manner at the blastoderm margin of the embryo to regulate the timing of mesoderm and endoderm (mesendoderm) cell ingression. Under- or over-expression of hoxb genes perturb the timing of mesendoderm cell ingression and, consequently, the positioning of these cells along the forming anterior-posterior body axis. Finally, we found that hoxb genes control the timing of mesendoderm ingression by regulating cell surface fluctuations. Thus, hoxb genes interconnect the temporal and spatial pattern of cell behavior in the early embryo by controlling cell surface fluctuations. HighlightsO_LIhoxb gene expression shows temporal collinearity at the blastoderm margin during zebrafish gastrulation. C_LIO_LITemporal collinear expression of hoxb genes at the blastoderm margin regulates the timing of cell ingression and delineates spatial collinearity after gastrulation. C_LIO_LIhoxb genes regulate cell surface fluctuations and bleb formation at the blastoderm margin during cell ingression C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=149 SRC="FIGDIR/small/579056v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@3a8517org.highwire.dtl.DTLVardef@1f7bda3org.highwire.dtl.DTLVardef@1c325a6org.highwire.dtl.DTLVardef@dce24d_HPS_FORMAT_FIGEXP M_FIG C_FIG hoxb genes are expressed at the blastoderm margin in a temporally collinear manner and determine the timing of mesendoderm ingression by triggering dynamic cell surface fluctuations and cell blebbing. This results in a spatial collinearity of mesendoderm cell positioning along the anterior-posterior extent of the forming body axis with early ingressing cells being positioned more anteriorly than late ingressing cells.

developmental biology↗

bioRxiv2018

The sustained release of basic fibroblast growth factor accelerates angiogenesis and the survival of the inactivated dermis by high hydrostatic pressure

We developed a novel skin regeneration therapy combining nevus tissue inactivated by high hydrostatic pressure (HHP) in the reconstruction of the dermis with a cultured epidermal autograft (CEA). The issue with this treatment is the unstable survival of CEA on the inactivated dermis. In this study, we applied collagen/gelatin sponge (CGS), which can sustain the release of basic fibroblast growth factor (bFGF), to the inactivated skin in order to accelerate angiogenesis. Murine skin grafts from C57BL6J/Jcl mice (8 mm in diameter) were prepared, inactivated by HHP and cryopreserved. One month later, the grafts were transplanted subcutaneously onto the back of other mice and covered by CGS impregnated with saline or bFGF. Grafts were taken after one, two and eight weeks, at which point the survival was evaluated through the histology and angiogenesis-related gene expressions were determined by real-time polymerase chain reaction. Histological sections showed that the dermal cellular density and newly formed capillaries in the bFGF group were significantly higher than in the control group. The relative expression of FGF-2, PDGF-A and VEGF-A genes in the bFGF group was significantly higher than in the control group at Week 1. This study suggested that the angiogenesis into grafts was accelerated, which might improve the survival in combination with the sustained release of bFGF by CGSs.

bioengineering↗

bioRxiv2018

N1 component of event-related potential evoked by simple composite figures in the lateral occipital cortex

Since Sugawara and Morotomi (1991) first reported that illusory contour (IC) figures, or Kanizsa square inducers (KSI), evoked a significant N1 component, the first visually evoked negative component of event-related potentials (ERPs), in the lateral occipital cortex (LO), many ERP studies have confirmed their finding, and these studies showed that Kanizsa-type inducers alone evoked a relatively large N1 in the LO, even when the inducers are oriented to not form an IC (see Murray and Herrmann, 2013). In the present study, we used non-IC simple composite figures composed of several elementary shapes (e.g., triplet squares or quadruplet circles) as visual stimuli, and found that the composite figures evoked a significant N1 comparable to that evoked by KSI in the anterior LO, whereas solitary elementary shapes did not. Thus, it appears that the LO is activated by not only an IC but also the compositeness of figures, which implies that the LO might analyze the geometrical relationships among multiple 2D shapes that compose a single composite figure.

neuroscience↗