Adipocytes mobilize in response to injury without plasticity

Kalgudde Gopal, Shruthi (2021): Adipocytes mobilize in response to injury without plasticity. Dissertation, LMU München: Medizinische Fakultät

Abstract

Cutaneous injury triggers cellular processes such as wound healing, tissue fibrosis, and scar development, which involve many different cell types. Successful regeneration after cutaneous injury requires timely coordinated actions of diverse cell types. Fibroblasts and adipocytes are two critical cell types in these processes and are thought to be displaying cellular plasticity. Cellular plasticity refers to the ability of a terminally differentiated cell type to take on the characteristics of another differentiated cell type. For example, an adipogenic fate gains plasticity towards a fibrogenic fate resulting in loss of cellular identity and normal function, with deleterious implications for regenerative healing. Current research in the field does not provide concrete evidence to show the two cell types’ inter-conversion capacity. Hence, it was crucial to make a head-on comparison of cellular and molecular signatures and features of these two cell types and show the fate of the two cell types upon injury. The results we obtained from this study enabled us to decipher the possible Fibro-adipogenic plasticity during wound healing and scar development. In the first part of the study, we developed an ex-vivo 3D disease model termed “SCAD (Scar-like tissue in a Dish)” that can recapitulate specific wound healing and scar development processes in a dish setting. We used the SCAD model to study certain cell-specific functions and processes involved in scar development. An extracellular matrix (ECM) is a significant scar tissue component, which is synthesized and deposited predominantly by the activated state of a fibroblast called a Myofibroblast. Hence, we used a transgenic mouse line that labels scar-forming fibroblasts to characterize scar development processes. Our results showed collective migration and upregulation of cell adhesion molecule N-cadherin in scarring fibroblasts upon injury. To functionally validate N-cadherin as a critical target gene enabling fibroblast collective migration, we combined the Adeno associated virus-based gene targeting and CRISPR-cas9 based gene manipulation technologies. Blocking N-cadherin inhibited fibroblast swarming and collective migration, leading to reduced scarring in ex-vivo SCADs and animal models. In the next part of the study, we uncovered the cellular plasticity features of fibroblast and adipocytes during scar development. We used transgenic mouse lines to label fibroblasts and adipocytes with a GFP reporter gene specifically. Evidence from transcriptomic signatures of both cell types by single-cell RNA sequencing showed that these cell types do not display cell plasticity but instead remain lineage-restricted. We further confirm lineage restriction with the ex-vivo scar model SCAD and time-lapse imaging and show that adipocytes reposition during injury, attain fibroblast-like morphology but do not transition into a fibrogenic fate. We also show that adipocytes migrate differently, deposit a meager amount of ECM, and do not transition into a myofibroblast. We conclude that adipocytes do not exhibit cellular plasticity in response to injury and remain as terminally differentiated types. We can utilize the knowledge of molecular and cellular mechanisms of adipocyte and fibroblast plasticity to develop cell-type targeted therapies in wound healing, tissue fibrosis, and scar development.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: Scar development, Skin Fibrosis, Adipocytes, Fibroblasts
• Themengebiete: 600 Technik, Medizin, angewandte Wissenschaften ; 600 Technik, Medizin, angewandte Wissenschaften > 610 Medizin und Gesundheit
• Fakultäten: Medizinische Fakultät
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 10. August 2021
• 1. Bericht­erstatter:in: Meiners, Silke