Adipose tissue-associated Krt23+fibroblasts contribute to immune microenvironment disorders in mouse adipose tissue during the development of obesity.

Obesity alters the adipose tissue (AT) immune microenvironment (TIME) and induces inflammation. Nevertheless, the specific time when TIME dysfunction emerges in AT remains elusive. Obesity mouse models were constructed and categorized into Lean (Ctrl), moderately obese (Mid_Ob, with body weight exceeding Ctrl by > 10%), and Obese (Ob, with body weight exceeding Ctrl by > 20%) groups. Single-nucleus RNA sequencing (snRNA-seq) and immunofluorescence localization were employed to analyze changes in cell populations, cluster marker genes, and signaling pathways in mouse epididymal white adipose tissue (eWAT). A total of 23,068 cells obtained from three mouse eWAT samples (Ctrl, Mid_Ob, and Ob) underwent snRNA-seq. Eighteen distinct clusters were identified, and seven cell types were annotated with representative markers. In-depth analysis unveiled the functions of the adipose AT-associated Krt23+fibroblast (ATAKF) cell subtype and refined the crosstalk hypothesis concerning ATAKFs, macrophages, and neutrophils. We further demonstrated that ATAKFs were present in the Mid_Ob group. Additionally, from the Mid_Ob to Ob stage, AT inflammatory factors, macrophages, and neutrophils significantly increased while neurons markedly decreased; however, these factors did not change significantly from the Ctrl to Mid_Ob stage. Cell-cell communication analysis revealed the central role of ATAKFs and their regulation of macrophages and neutrophils. Only when obesity reaches the Mid_Ob stage AT fibroblasts specifically express Krt23+, recruit neutrophils, and secrete CCL2, CCL6, and CCL9 to attract macrophages, thereby altering the eWAT TIME. ATAKFs contribute to immune microenvironment disorders during the development of mouse AT obesity. This study offers valuable resources and a foundation for understanding the timing of TIME dysfunction.