Browsing by Author "Cerda, Mauricio"

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    A computational framework for testing hypotheses of the minimal mechanical requirements for cell aggregation using early annual killifish embryogenesis as a model
    (FRONTIERS MEDIA SA, 2023) Montenegro-Rojas, Ignacio; Yanez, Guillermo; Skog, Emily; Guerrero-Calvo, Oscar; Andaur-Lobos, Martin; Dolfi, Luca; Cellerino, Alessandro; Cerda, Mauricio; Concha, Miguel L.; Bertocchi, Cristina; Rojas, Nicolas O.; Ravasio, Andrea; Rudge, Timothy J.
    Introduction: Deciphering the biological and physical requirements for the outset of multicellularity is limited to few experimental models. The early embryonic development of annual killifish represents an almost unique opportunity to investigate de novo cellular aggregation in a vertebrate model. As an adaptation to seasonal drought, annual killifish employs a unique developmental pattern in which embryogenesis occurs only after undifferentiated embryonic cells have completed epiboly and dispersed in low density on the egg surface. Therefore, the first stage of embryogenesis requires the congregation of embryonic cells at one pole of the egg to form a single aggregate that later gives rise to the embryo proper. This unique process presents an opportunity to dissect the self-organizing principles involved in early organization of embryonic stem cells. Indeed, the physical and biological processes required to form the aggregate of embryonic cells are currently unknown., Methods: Here, we developed an in silico, agent-based biophysical model that allows testing how cell-specific and environmental properties could determine the aggregation dynamics of early Killifish embryogenesis. In a forward engineering approach, we then proceeded to test two hypotheses for cell aggregation (cell-autonomous and a simple taxis model) as a proof of concept of modeling feasibility. In a first approach (cell autonomous system), we considered how intrinsic biophysical properties of the cells such as motility, polarity, density, and the interplay between cell adhesion and contact inhibition of locomotion drive cell aggregation into self-organized clusters. Second, we included guidance of cell migration through a simple taxis mechanism to resemble the activity of an organizing center found in several developmental models., Results: Our numerical simulations showed that random migration combined with low cell-cell adhesion is sufficient to maintain cells in dispersion and that aggregation can indeed arise spontaneously under a limited set of conditions, but, without environmental guidance, the dynamics and resulting structures do not recapitulate in vivo observations., Discussion: Thus, an environmental guidance cue seems to be required for correct execution of early aggregation in early killifish development. However, the nature of this cue (e.g., chemical or mechanical) can only be determined experimentally. Our model provides a predictive tool that could be used to better characterize the process and, importantly, to design informed experimental strategies.
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    AI-assisted imaging screening reveals mechano-molecular tissue organizers and network of signaling hubs
    (2024) Bertocchi, Cristina; Alegría, Juan José; Vásquez Sepúlveda, Sebastian Ignacio; Ibañez Prat, Rosario; Aishwarya, Srinivasan; Arraño Valenzuela, Ignacio Alberto; Castro Pereira, Barbara Helen; Soto Montandon, Catalina Andrea; Trujillo Espergel, Alejandra Isabel; Owen, Gareth Ivor; Kanchanawong, Pakorn; Cerda, Mauricio; Motta, Giovanni; Zaidel Bar, Ronen; Ravasio, Andrea
    Cadherin-mediated adhesions are crucial mechanical and signaling hubs that connect cells within a tissue and probe the mechanics of the surrounding environment. They constitute a physical link between the actin cytoskeleton of neighboring cells, providing the mechanical coordination needed for morphogenetic processes, tissue homeostasis, collective migration, and regeneration. Disruptions in adhesion mechanisms are closely linked to the breakdown of epithelial structure and the emergence of disease-related traits characteristic of cancer progression. The cadhesome network comprises over 170 structural and regulatory proteins involved in cadherin-mediated adhesion. While this network is essential for coordinating tissue responses to mechanical stress, its complexity has historically limited our understanding of how individual components contribute to force transmission and tissue homeostasis. Recent technological advances offer tools to investigate large molecular networks in cellular function and pathology (functional omics). Leveraging these advances, we developed an experimental and analytical platform combining high-throughput gene silencing, imaging, and artificial intelligence (AI) to systematically profile each role of each protein in tissue formation, mechanical stability, and response to induced tension. Using EpH4 cells as an epithelial tissue model, we performed systematic silencing in triplicate, capturing a range of tissue phenotypes under baseline and tension-inducing conditions. Machine learning methods were used to analyze complex imaging data, quantify tissue ruptures, characterize junctional organization, and measure tension states of the tissue. By incorporating machine learning algorithms, we automated image feature extraction, clustering, and classification, enabling an unprecedented quantitative evaluation of tissue mechanics at scale. Our machine learning models allowed us to identify significant patterns, including protein specific responses to tension and their roles in tissue-level mechanical integrity. Finally, we constructed a protein interaction network detailing the roles of each protein, their physical interactions, and known links to cancer. The network analysis revealed three prominent mechanotransductive and signaling subnetworks centered around E-cadherin, EGFR, and RAC1. Our study provides a foundational framework for investigating mechanosensing proteins and it offers a scalable blueprint for discovering potential therapeutic targets in diseases like cancer, where tissue mechanics play a crucial role.
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    Experimental transplants of the large kelp Lessonia nigrescens (Phaeophyceae) in high-energy wave exposed rocky intertidal habitats of northern Chile
    (2006) Correa, Juan A.; Lagos, Nelson A.; Medina, Matias H.; Castilla, Juan C.; Cerda, Mauricio; Ramirez, Marco; Martinez, Enrique; Faugeron, Sylvain; Andrade, Santiago; Pinto, Raquel; Contreras, Loretto
    Potential for addressing ecological and physiological issues becomes severely limited when the organisms required to experimentally test specific hypotheses are absent from the study areas. This report describes a simple and inexpensive device for re-planting kelps into the lower intertidal zone of wave-swept rocky habitats, using Lessonia nigrescens Bory as a model organism. The device allows a wide range of plant sizes to be anchored by the holdfast. Transplanted kelps regenerated, re-attached to the substratum and overgrew the transplanting device. These results confirm the feasibility of using this technique to tackle a variety of highly relevant questions involving ecological, physiological, conservation, restoration and management issues. (c) 2006 Elsevier B.V. All rights reserved.
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    Palmitic acid control of ciliogenesis modulates insulin signaling in hypothalamic neurons through an autophagy-dependent mechanism
    (SPRINGERNATURE, 2022) Avalos, Yenniffer; Paz Hernandez-Caceres, Maria; Lagos, Pablo; Pinto-Nunez, Daniela; Rivera, Patricia; Burgos, Paulina; Diaz-Castro, Francisco; Joy-Immediato, Michelle; Venegas-Zamora, Leslye; Lopez-Gallardo, Erik; Kretschmar, Catalina; Batista-Gonzalez, Ana; Cifuentes-Araneda, Flavia; Toledo-Valenzuela, Lilian; Rodriguez-Pena, Marcelo; Espinoza-Caicedo, Jasson; Perez-Leighton, Claudio; Bertocchi, Cristina; Cerda, Mauricio; Troncoso, Rodrigo; Parra, Valentina; Budini, Mauricio; Burgos, Patricia, V; Criollo, Alfredo; Morselli, Eugenia
    Palmitic acid (PA) is significantly increased in the hypothalamus of mice, when fed chronically with a high-fat diet (HFD). PA impairs insulin signaling in hypothalamic neurons, by a mechanism dependent on autophagy, a process of lysosomal-mediated degradation of cytoplasmic material. In addition, previous work shows a crosstalk between autophagy and the primary cilium (hereafter cilium), an antenna-like structure on the cell surface that acts as a signaling platform for the cell. Ciliopathies, human diseases characterized by cilia dysfunction, manifest, type 2 diabetes, among other features, suggesting a role of the cilium in insulin signaling. Cilium depletion in hypothalamic pro-opiomelanocortin (POMC) neurons triggers obesity and insulin resistance in mice, the same phenotype as mice deficient in autophagy in POMC neurons. Here we investigated the effect of chronic consumption of HFD on cilia; and our results indicate that chronic feeding with HFD reduces the percentage of cilia in hypothalamic POMC neurons. This effect may be due to an increased amount of PA, as treatment with this saturated fatty acid in vitro reduces the percentage of ciliated cells and cilia length in hypothalamic neurons. Importantly, the same effect of cilia depletion was obtained following chemical and genetic inhibition of autophagy, indicating autophagy is required for ciliogenesis. We further demonstrate a role for the cilium in insulin sensitivity, as cilium loss in hypothalamic neuronal cells disrupts insulin signaling and insulin-dependent glucose uptake, an effect that correlates with the ciliary localization of the insulin receptor (IR). Consistently, increased percentage of ciliated hypothalamic neuronal cells promotes insulin signaling, even when cells are exposed to PA. Altogether, our results indicate that, in hypothalamic neurons, impairment of autophagy, either by PA exposure, chemical or genetic manipulation, cause cilia loss that impairs insulin sensitivity.
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    Perioperative chemotherapy in locally advanced gastric cancer in Chile: from evidence to daily practice
    (2021) Muller, Bettina; Garcia, Carlos; Sola, Jose A.; Fernandez, Wanda; Werner, Patrick; Cerda, Mauricio; Slater, Jeannie; Benavides, Carlos; Arancibia, Jorge; Ascui, Rodrigo; Reyes, Felipe; Anne Stevens, Mary; Pablo Miranda, Juan; Buchholtz, Martin; Corvalan, Alejandro H.
    Gastric cancer (GC) is a leading cause of cancer death in Chile. Although recommended in international guidelines since 2006, perioperative chemotherapy was not available to patients in the public health system in Chile until 2016. We conducted an observational study to assess the feasibility of this strategy in public hospitals in Chile (Observational Study of Perioperative Chemotherapy in Locally Advanced Gastric Cancer - PRECISO). Patients with locally advanced, operable GC were offered to receive preoperative chemotherapy with Epirubicin + Cisplatin + Capecitabine (ECX) for three cycles followed by curative surgery. Staging included abdominal CT scan and laparoscopy if peritoneal carcinomatosis was suspected. Postoperative ECX for three cycles was recommended. Between August 2010 and March 2013, 110 patients were screened and 61 enrolled. Median age was 62 years (23-76 years) and most patients had good performance status at baseline (Eastern Cooperative Oncology Group performance status score (ECOG) 0: 42, ECOG 1: 19). Tumour site was proximal in 32 (52%) and medial and distal in 29 (48%) patients. All but four patients (n = 57, 93%) completed three cycles of preoperative chemotherapy. Fifty-six patients were operated and 54 (89%) had a curative resection. Thirty-three patients (54%) had pT0-2, and 18 (30%) had pN0 tumours, with two patients achieving a complete response. As of 20 December 2020, 39 patients died, 32 due to GC, one within 30 days of surgery, two due to intestinal obstruction at 5 and 3 months after surgery and four due to other causes. Five-year survival rate was 38%. We conclude that perioperative chemotherapy is feasible in public hospitals in Chile and should be offered to patients with locally advanced GC.
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    Socioeconomic, Clinical, and Molecular Features of Breast Cancer Influence Overall Survival of Latin American Women
    (2022) de Almeida, Liz Maria; Cortés Arancibia, Sandra; Vilensky, Marta; Valenzuela, Olivia; Cortes-Sanabria, Laura; de Souza, Mirian; Alonso Barbeito, Rafael; Abdelhay, Eliana; Artagaveytia, Nora; Daneri-Navarro, Adrian; Llera, Andrea S.; Muller, Bettina; Podhajcer, Osvaldo L.; Velazquez, Carlos; Alcoba, Elsa; Alonso, Isabel; Bravo, Alicia, I; Camejo, Natalia; Maria Carraro, Dirce; Castro, Monica; Cataldi, Sandra; Cayota, Alfonso; Cerda, Mauricio; Colombo, Alicia; Crocamo, Susanne; Del Toro-Arreola, Alicia; Delgadillo-Cristerna, Raul; Delgado, Lucia; Breitenbach, Marisa Dreyer; Fernandez, Elmer; Fernandez, Jorge; Fernandez, Wanda; Franco-Topete, Ramon A.; Gaete, Fancy; Gomez, Jorge; Gonzalez-Ramirez, Leivy P.; Guerrero, Marisol; Gutierrez-Rubio, Susan A.; Jalfin, Beatriz; Lopez-Vazquez, Alejandra; Loria, Dora; Miguez, Silvia; Moran-Mendoza, Andres de J.; Morgan-Villela, Gilberto; Mussetti, Carina; Nagai, Maria Aparecida; Oceguera-Villanueva, Antonio; Reis, Rui M.; Retamales, Javier; Rodriguez, Robinson; Rosales, Cristina; Salas-Gonzalez, Efrain; Segovia, Laura; Sendoya, Juan M.; Silva-Garcia, Aida A.; Vina, Stella; Zagame, Livia; Jones, Beth; Szklo, Moyses
    Molecular profile of breast cancer in Latin-American women was studied in five countries: Argentina, Brazil, Chile, Mexico, and Uruguay. Data about socioeconomic characteristics, risk factors, prognostic factors, and molecular subtypes were described, and the 60-month overall cumulative survival probabilities (OS) were estimated. From 2011 to 2013, 1,300 eligible Latin-American women 18 years or older, with a diagnosis of breast cancer in clinical stage II or III, and performance status not less than or equal to 1 were invited to participate in a prospective cohort study. Face-to-face interviews were conducted, and clinical and outcome data, including death, were extracted from medical records. Unadjusted associations were evaluated by Chi-squared and Fisher's exact tests and the OS by Kaplan-Meier method. Log-rank test was used to determine differences between cumulative probability curves. Multivariable adjustment was carried out by entering potential confounders in the Cox regression model. The OS at 60 months was 83.9%. Multivariable-adjusted death hazard differences were found for women living in Argentina (2.27), Chile (1.95), and Uruguay (2.42) compared with Mexican women, for older (>= 60 years) (1.84) compared with younger (<= 40 years) women, for basal-like subtype (5.8), luminal B (2.43), and HER2-enriched (2.52) compared with luminal A subtype, and for tumor clinical stages IIB (1.91), IIIA (3.54), and IIIB (3.94) compared with stage IIA women. OS was associated with country of residence, PAM50 intrinsic subtype, age, and tumor stage at diagnosis. While the latter is known to be influenced by access to care, including cancer screening, timely diagnosis and treatment, including access to more effective treatment protocols, it may also influence epigenetic changes that, potentially, impact molecular subtypes. Data derived from heretofore understudied populations with unique geographic ancestry and sociocultural experiences are critical to furthering our understanding of this complexity.
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    The limitations and challenges in the assessment of executive dysfunction associated with real-world functioning: The opportunity of serious games
    (2023) Martinez-Pernia, David; Olavarria, Loreto; Fernandez-Manjon, Baltasar; Cabello, Victoria; Henriquez, Fernando; Robert, Philippe; Alvarado, Luis; Barria, Silvia; Antivilo, Andres; Velasquez, Juan; Cerda, Mauricio; Farias, Gonzalo; Torralva, Teresa; Ibanez, Agustin; Parra, Mario A.; Gilbert, Sam; Slachevsky, Andrea
    Nowadays, there is a broad range of methods for detecting and evaluating executive dysfunction ranging from clinical interview to neuropsychological evaluation. Nevertheless, a critical issue of these assessments is the lack of correspondence of the neuropsychological test's results with real-world functioning. This paper proposes serious games as a new framework to improve the neuropsychological assessment of real-world functioning. We briefly discuss the contribution and limitations of current methods of evaluation of executive dysfunction (paper-and-pencil tests, naturalistic observation methods, and Information and Communications Technologies) to inform on daily life functioning. Then, we analyze what are the limitations of these methods to predict real-world performance: (1) A lack of appropriate instruments to investigate the complexity of real-world functioning, (2) the vast majority of neuropsychological tests assess well-structured tasks, and (3) measurement of behaviors are based on simplistic data collection and statistical analysis. This work shows how serious games offer an opportunity to develop more efficient tools to detect executive dysfunction in everyday life contexts. Serious games provide meaningful narrative stories and virtual or real environments that immerse the user in natural and social environments with social interactions. In those highly interactive game environments, the player needs to adapt his/her behavioral performance to novel and ill-structured tasks which are suited for collecting user interaction evidence. Serious games offer a novel opportunity to develop better tools to improve diagnosis of the executive dysfunction in everyday life contexts. However, more research is still needed to implement serious games in everyday clinical practice.
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    VolumePeeler: a novel FIJI plugin for geometric tissue peeling to improve visualization and quantification of 3D image stacks
    (BMC, 2023) Gatica, Marilyn; Navarro, Carlos F. F.; Lavado, Alejandro; Reig, German; Pulgar, Eduardo; Llanos, Paula; Haertel, Steffen; Ravasio, Andrea; Bertocchi, Cristina; Concha, Miguel L. L.; Cerda, Mauricio
    Motivation Quantitative descriptions of multi-cellular structures from optical microscopy imaging are prime to understand the variety of three-dimensional (3D) shapes in living organisms. Experimental models of vertebrates, invertebrates and plants, such as zebrafish, killifish, Drosophila or Marchantia, mainly comprise multilayer tissues, and even if microscopes can reach the needed depth, their geometry hinders the selection and subsequent analysis of the optical volumes of interest. Computational tools to "peel" tissues by removing specific layers and reducing 3D volume into planar images, can critically improve visualization and analysis.Results We developed VolumePeeler, a versatile FIJI plugin for virtual 3D "peeling" of image stacks. The plugin implements spherical and spline surface projections. We applied VolumePeeler to perform peeling in 3D images of spherical embryos, as well as non-spherical tissue layers. The produced images improve the 3D volume visualization and enable analysis and quantification of geometrically challenging microscopy datasets.