Julien Chlasta

bioMérieux (France)

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Gaël Runel

Université Claude Bernard Lyon 1

Ingrid Masse

Université Claude Bernard Lyon 1

Noémie Lopez-Ramirez

Université Claude Bernard Lyon 1

Pascale Milani

École Normale Supérieure de Lyon

Muriel Cario

Inserm

Sanja Kežić

University of Amsterdam

Jean-Luc Duteyrat

Inserm

Julie Caramel

Centre de Recherche en Cancérologie de Lyon

Marilyne Malbouyres

École Normale Supérieure de Lyon

Florence Ruggiero

Université Claude Bernard Lyon 1

Cooperative Institutions

Centre National de la Recherche Scientifique

Université Claude Bernard Lyon 1

Inserm

École Normale Supérieure de Lyon

Centre de Recherche en Cancérologie de Lyon

Centre Léon Bérard

Laboratoire de Biologie Moléculaire de la Cellule

Institut de Génomique Fonctionnelle de Lyon

Institut de Biologie et de Chimie des Protéines

Pierre Fabre (France)

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663 Medaka fish as a good model to study skin aging by Atomic Force Microscopy

Journal of Investigative Dermatology (2019)

Gaël Runel Muriel Cario Noémie Lopez-Ramirez Lorraine Bernard Julien Chlasta

Skin Aging

Oryzias

Human skin

Matrix (chemical analysis)

10.1016/j.jid.2019.07.668

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LB1531 Changes in nano-mechanical properties of human corneocytes depending on their proximity to the skin surface

Journal of Investigative Dermatology (2018)

Pascale Milani Julien Chlasta Rawad Abdayem Sanja Kežić Marek Haftek

Corneocyte

Human skin

Epidermis (zoology)

Envelope (radar)

10.1016/j.jid.2018.06.064

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Effect of a low‐mineralized thermal spring water on skin barrier mechanical properties using atomic force microscopy

Experimental Dermatology (2024)

Céline Mias Aline Stennevin G. Doat Anna Catte Julien Chlasta

The mineral content of thermal spring water (TSW) applied to the skin surface can directly influence the skin barrier. Indeed, our previous study showed that Avène TSW (ATSW), a low mineral content thermal spring water, protects the stratum corneum from dehydration compared to a mineral-rich TSW (MR-TSW) and maintains skin surface ultrastructure. While many TSWs have been recognized to have beneficial effects on skin, little is known about their localized and specific effects on skin barrier biomechanics at the nanometric scale. The aim of this study was to compare the effects of ATSW with a reference, MR-TSW, on the biomechanical barrier properties of the skin under homeostasis conditions using atomic force microscopy (AFM). AFM was used to obtain a precise nanomechanical mapping of the skin surface after three applications of both TSW. This provides specific information on the skin topographical profile and elasticity. The topographic profile of skin samples showed a specific compaction of the skin layers after application of MR-TSW, characterized by an increase of the total number of external skin layers, compared to non-treated samples. By contrast, ATSW did not modify the skin topographic profile. High-resolution force/volume acquisitions to capture the elastic modulus showed that it was directly correlated with skin rigidity. The elastic modulus strongly and significantly increased after MR-TSW application compared to non-treated skin. By contrast, applications of ATSW did not increase elastic modulus. These data demonstrate that applications of MR-TSW significantly modified skin barrier properties by increasing skin surface layer compaction and skin rigidity. By contrast, ATSW did not modify the topographical profile of skin explants nor induce mechanical stress at the level of the stratum corneum, indicating it does not disrupt the biophysical properties linked to skin surface integrity.

10.1111/exd.15113

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Cancer Cell Biomechanical Properties Accompany Tspan8-Dependent Cutaneous Melanoma Invasion

Cancers (2024)

Gaël Runel Noémie Lopez-Ramirez Laetitia Barbollat‐Boutrand Muriel Cario Simon Durand

The intrinsic biomechanical properties of cancer cells remain poorly understood. To decipher whether cell stiffness modulation could increase melanoma cells’ invasive capacity, we performed both in vitro and in vivo experiments exploring cell stiffness by atomic force microscopy (AFM). We correlated stiffness properties with cell morphology adaptation and the molecular mechanisms underlying epithelial-to-mesenchymal (EMT)-like phenotype switching. We found that melanoma cell stiffness reduction was systematically associated with the acquisition of invasive properties in cutaneous melanoma cell lines, human skin reconstructs, and Medaka fish developing spontaneous MAP-kinase-induced melanomas. We observed a systematic correlation of stiffness modulation with cell morphological changes towards mesenchymal characteristic gains. We accordingly found that inducing melanoma EMT switching by overexpressing the ZEB1 transcription factor, a major regulator of melanoma cell plasticity, was sufficient to decrease cell stiffness and transcriptionally induce tetraspanin-8-mediated dermal invasion. Moreover, ZEB1 expression correlated with Tspan8 expression in patient melanoma lesions. Our data suggest that intrinsic cell stiffness could be a highly relevant marker for human cutaneous melanoma development.

10.3390/cancers16040694

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EASYSTIFF^®, a portable and innovative device able to separately analyze each skin compartment for the evaluation of mechanical properties

bioRxiv (Cold Spring Harbor Laboratory) (2023)

Gaël Runel Jean-André Lapart Julien Chlasta

Abstract Human skin is submitted to various factors leading to either extrinsic or intrinsic aging. In addition to inducing molecular and morphological changes, skin aging is characterized by modifications in skin biomechanical properties modifications. These modifications can be used as biomarkers to both evaluate the degree of advancement in skin aging but also to detect potential pathologies. Hence, it is from critical interest to be able to evaluate skin biomechanical properties to fully detect and monitor these alterations. Here we introduce a portable and innovative ® device, EASYSTIFF ® , which is thought to in vivo measure stiffness properties of skin. Based on indentation principle, EASYSTIFF allows to identify both global stiffness of skin (all confounded cutaneous compartment) or compartmentalized stiffness, in which stiffness values of each compartment, i.e., the stratum corneum, the epidermis, the dermis and the hypodermis, are separately analyzed. Thus, EASYSTIFF is a complementary tool to 2D and 3D in/ex vivo model and an alternative to existing devices that measure skin mechanical properties, for assessing the effectiveness of cosmetic products, monitoring skin stiffness over time and to provide better understanding in the evolution of skin mechanical properties.

Compartment (ship)

Epidermis (zoology)

Skin Aging

Human skin

Indentation

Pig skin

Skin thickness

Skin equivalent

10.1101/2023.07.13.548841

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Transforming Growth Factor β/activin signalling induces epithelial cell flattening during Drosophila oogenesis

Biology Open (2015)

Isabelle Brigaud Jean-Luc Duteyrat Julien Chlasta Sandrine Le Bail Jean‐Louis Couderc

Although the regulation of epithelial morphogenesis is essential for the formation of tissues and organs in multicellular organisms, little is known about how signalling pathways control cell shape changes in space and time. In the Drosophila ovarian epithelium, the transition from a cuboidal to a squamous shape is accompanied by a wave of cell flattening and by the ordered remodelling of E-cadherin-based adherens junctions. We show that activation of the TGFβ pathway is crucial to determine the timing, the degree and the dynamic of cell flattening. Within these cells, TGFβ signalling controls cell-autonomously the formation of Actin filament and the localisation of activated Myosin II, indicating that internal forces are generated and used to remodel AJ and to promote cytoskeleton rearrangement. Our results also reveal that TGFβ signalling controls Notch activity and that its functions are partly executed through Notch. Thus, we demonstrate that the cells that undergo the cuboidal-to-squamous transition produce active cell-shaping mechanisms, rather than passively flattening in response to a global force generated by the growth of the underlying cells. Thus, our work on TGFβ signalling provides new insights into the mechanisms through which signal transduction cascades orchestrate cell shape changes to generate proper organ structure.

Adherens junction

10.1242/bio.201410785

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Rôle de la membrane basale lors de la morphogenèse épithéliale chez Drosophila melanogaster

Julien Chlasta

Les membranes basales (MB) jouent un role majeur au cours des processus morphogenetiques. Elles et sont principalement composees de Collagene de type IV, de Perlecan et de Laminine. Les recepteurs d'adhesions/signalisations (Integrines/Dystroglycans) localises au pole basal des cellules epitheliales, interagissent directement avec les MBs. De nombreuses etudes montrent l'importance de la composition des MBs dans le devenir cellulaire. Cependant, le role mecanique de la MB au cours du developpement d'un organe multicouche n'est pas connu. Comme modele de morphogenese epitheliale, nous avons choisi d'etudier l'epithelium du follicule ovarien chez Drosophila melanogaster. La MB entoure chaque follicule ovarien qui est compose d'une monocouche de cellules epitheliales cuboides entourant un groupe interne forme de 16 cellules de la lignee germinale (15 cellules nourricieres en posterieur et 1 ovocyte en anterieur). Au cours du developpement folliculaire, les cellules epitheliales s'aplatissent suivant une vague antero-posterieur. Cette transition cellulaire cuboide – aplatie depend du remodelage des jonctions d'adherence et du cytosquelette. Mes travaux de these ont porte sur l'etude du role mecanique et moleculaire de la MB au cours de la morphogenese epitheliale chez la Drosophile. J'ai ainsi pu montrer (i) que la rigidite de la MB augmente au fur et a mesure du developpement du follicule, (ii) que l'aplatissement depend de la structure de la MB et de la liaison a cette MB grâce aux integrines (iii) que la MB s'assouplie lors de la transition cuboide-squameux et que cette assouplissement depend de ce processus. Ces resultats demontrent un dynamisme mecanique et moleculaire de la MB au cours de l'ovogenese et de la morphogenese, revelant le role central de la MB lors de ces processus. Parallelement j'ai developpe une approche par segmentation cellulaire afin d'extraire les valeurs metriques (hauteur, anisotropie, surface basale, volume) des cellules epitheliales et de mesurer les variations de ces parametres au cours de la morphogenese epitheliale (MARS-ALT)

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Role of basement membrane during epithelial morphogenesis in Drosophila melanogaster

HAL (Le Centre pour la Communication Scientifique Directe) (2016)

Julien Chlasta

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Changes in nano‐mechanical properties of human epidermal cornified cells depending on their proximity to the skin surface

Journal of Molecular Recognition (2018)

Pascale Milani Julien Chlasta Rawad Abdayem Sanja Kežić Marek Haftek

Abstract During formation of the stratum corneum (SC) barrier, terminally differentiated keratinocytes continue their maturation process within the dead superficial epidermal layer. Morphological studies of isolated human corneocytes have revealed differences between cornified envelopes purified from the deep and superficial SC. We used atomic force microscopy to measure the mechanical properties of native human corneocytes harvested by tape‐stripping from different SC depths. Various conditions of data acquisition have been tested and optimized, in order to obtain exploitable and reproducible results. Probing at 200 nN allowed us to investigate the total stiffness of the cells (at 50 nm indentation) and that of the cornified envelopes (at 10 to15 nm), and lipid envelopes (at 5 to 10 nm). The obtained data indicated statistically significant differences between the superficial (more rigid) and deep (softer) corneocytes, thus confirming the existence of depth and maturation‐related morphological changes within the SC. The proposed approach can be potentially used for minimally invasive evaluation of various skin conditions such as aging, skin hydration, and pathologies linked to SC.

Corneocyte

Human skin

Epidermis (zoology)

10.1002/jmr.2722

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Anas barbariae 200K Modulates Cell Stiffness and Oxidative Stress in Microglial Cells In Vitro

International Journal of Molecular Sciences (2025)

Anne Paumier Justine Verre Gaël Runel Julien Chlasta Sandra Tribolo

Anas barbariae 200K, a homeopathic medicine, is traditionally used for influenza-like illnesses. We investigated the effects of Anas barbariae 200K on microglial cells, a subpopulation of macrophages specific to the central nervous system often used to study the inflammatory processes and oxidative stress generated during influenza-like episodes. The study demonstrates the effect of Anas barbariae 200K on cell stiffness and the reactive oxygen species production using atomic force microscopy and fluorescence microscopy techniques, respectively. Our results showed that Anas barbariae 200K rapidly increased cell stiffness in resting cells by 41% compared with the vehicle. In inflamed cells, cell stiffness was decreased by 21% when treated with Anas barbariae 200K compared with the vehicle. Finally, Anas barbariae 200K caused a reorganisation of filamentous actin, with marked relocation of actin at the cell extremities. Moreover, Anas barbariae 200K significantly decreased the reactive oxygen species (ROS) production in inflamed microglial cells by 40% (total intracellular ROS) and by 67% (mitochondrial ROS) compared with the vehicle. These results strongly suggest an effect of Anas barbariae 200K at a cellular level on cell stiffness and actin cytoskeleton. This sheds light on the biological mechanism of action of this homeopathic preparation.

10.3390/ijms26041451

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