This project used a multi-omics approach to study the adipose tissue transcriptome in humans with and without obesity. Our human cohort included males and females between the ages of 18-80 who underwent elective abdominal surgery at the University of Michigan and the Ann Arbor Veterans Affairs Healthcare System.Patients with advanced cancer or immuncompromised status were excluded. Visceral adipose tissue (VAT/omental) and subcutaneous adipose tissue (SAT/abdominal wall) were collected from subjects with obesity (BMI>=35) at the beginning of elective surgical procedures, placed on ice, and transported back to the laboratory for immediate processing. For adipose tissue stromal cells (ASC) isolation, adipose tissue was digested with Type II collagenase (2 mg/mL in PBS/2% BSA) at 37oC, 60min, centrifuged at 250 rcf, and the stromal-vascular cell pellet was retrieved, plated overnight, and the adherent cells passaged three times to enrich for ASC, which were then frozen in DMEM/F12, 15% fetal calf serum, and 10% DMSO in liquid nitrogen until use. Single nuclear sequencing was performed on preparations from intact adipose tissue. Bulk RNA sequencing and single cell sequencing were performed on ASC isolated from intact adipose tissue and cultured in 2D and 3D culture systems. We currently apply bulk, single cell, and single nuclear sequencing analyses to these tissues. One component of this project studies single nuclear sequencing in nuclei isolated from intact adipose tissues from human subjects with obesity, focusing on depot comparisons (VAT vs. SAT). This cohort also permits comparisons of adipose tissue transcriptomes between male and female subjects, controlling for age and BMI. Primary findings to date include identification of multiple ASC, adipocyte, and endothelial cell (EC) subpopulations, T-cell, and macrophage (MAC) populations that are in concordance with and expand upon other published datasets. Of two dominant ASC subpopulations, one (inflammatory-mesothelial, IM- ASC) is present in VAT, but absent in SAT, while the other (fibroadipogenic, FA-ASC) is present in both VAT and SAT. We identified multiple EC subtypes with features of lymphatic, venous, and arterial EC, and a <a href="https://www.ncbi.nlm.nih.gov/gene/63976">PRDM16</a> expressing population with features of an EC progenitor. Immune cell populations match recent experimental validation of lipid-activated macrophage (LAM) phenotypes, <a href="https://www.ncbi.nlm.nih.gov/gene/91937">TIM4</a> macrophages, and a prominent population of <a href="https://www.ncbi.nlm.nih.gov/gene/4360">MRC1/CD206</a>+ resident AT macrophages with expression signatures related to glucocorticoid activation. These data support depot-specific differences in ASC subpopulations and previously unrecognized EC heterogeneity within human AT, with the potential to shed light on functional differences in AT depot and disease state. Planned future studies include ATAC-Seq and other omics analyses. Another component of this project studies transcriptional responses of ASC in vitro to various stimuli, including different matrix environments. Current data includes bulk RNA Sequencing of human ASC from VAT and SAT differentiated into mature adipocytes in hydrogels of differing stiffness (3%, 5%, 10%) to define transcriptional responses to matrix environments of different stiffness. Primary findings to date include enrichment of adipogenesis and lipid and oxidative metabolic gene pathways in adipocytes in 5% relative to 3% hydrogels, while fibrotic gene pathways have been enriched in 3% hydrogels. These data demonstrate that intermediate density matrix promotes a more adipogenic, less fibrotic adipocyte phenotype geared towards increased lipid and aerobic metabolism. Planned future studies include expansion of intact tissues from our cohort studied with single nuclear sequencing, as well as further study of ASC responses in vitro to different biologic stimuli, including different matrix environments.

Adipose Tissue Omics In Obesity

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