Single-nuclei Transcriptome of Human AT Reveals Metabolically Distinct Depot-Specific Adipose Progenitor Subpopulations

Abstract

Single-cell and single-nuclei RNA sequencing data (scRNAseq and snRNAseq, respectively) have revealed substantial heterogeneity in the AT (AT) cellular landscape in rodents and humans depending on depot and disease status. We used snRNAseq to characterize the cellular landscape of human visceral (VAT) and subcutaneous AT (SAT) samples from lean subjects and subjects with obesity. We identified multiple cell types in the AT cellular repertoire, including three major AT stromal cell (ASC) subpopulations, multiple types of adipocyte (ADIPO) populations that retain properties similar to ASC, endothelial cell (EC), T-cell, and macrophage (MAC) populations that are in concordance and expand upon other published datasets. ADIP and EC are more prominent in SAT compared to VAT which has a higher proportion of ASC. 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. Both populations retain their properties in in vitro culture and have adipogenic capacity with different metabolic features. Informatic and in situ studies support ADIP derived from IM- and FA-ASC are found in human VAT. We also identified a wide range of EC subtypes in human AT with features of lymphatic, venous, and arterial EC, with identification of a PRDM16 expression EC population with features of an EC progenitor. Immune cell populations match recent experimental validation of lipid activated macrophage (LAM) phenotypes, TIM4 macrophages, and a prominent population of MRC1/CD206+ resident AT macrophages with gene expression signatures related to glucocorticoid activation. Overall, our study demonstrates depot-specific cellular diversity in human VAT and SAT in which distinct ASC subpopulations may differently contribute to AT dysfunction in obesity. Also, our results highlight an unprecedented EC heterogeneity suggesting AT EC as highly specialized cells and potentially important regulators of depot-specific functions.

Single-nuclei analysis reveals depot-specific transcriptional heterogeneity and depot-specific cell types in adipose tissue of dairy cows

“…SAT-specific MAC3 was majorly characterized by Frontiers in Cell and Developmental Biology frontiersin.org ABL1, which's expression regulates macrophage podosome formation, SPTBN1, ZBTB16, and ADAMTSL3. In agreement with previous studies in human AT (Jaitin et al, 2019;Vijay et al, 2020;Strieder-Barboza et al, 2022), MAC4 had a lipid associated macrophage (LAM) profile with high expression of FABP4, LPL, CD36, FASN, CD9, among other lipid related genes (Figure 6D, Supplementary Table S10). Abundance of MAC4 nuclei was increased by approximately 2-fold in VAT compared to SAT (20.3% vs. 10.6%) and SAT MAC4 had increased expression of lipogenic genes (FASN, SCD, and ACLY) when compared to VAT MAC4 (Supplementary Table S12).…”

“…We have summarized the gene profile of each cell type and subtype in VAT and SAT of dairy cows revealed by our study in Graphical abstract. Part of the different cell types and depot-specificities characterized in the present study have been previously reported in mice and human models (e.g., Vijay et al, 2020;Emont et al, 2022;Strieder-Barboza et al, 2022). Compared with human AT single-cell databases, we observed that AT from dairy cows is as diverse as human SAT and VAT with similar cell types and subtypes, including numerous ASPCs, EC, and immune cells, and VATspecific ME.…”

“…This profile is typical of ASPCs that are "committed preadipocytes" (e.g., Sun et al, 2020;Emont et al, 2022), meaning these cells are poised to differentiate into mature adipocytes. This contrasts with recent snRNA-seq data in human subjects with obesity (Strieder-Barboza et al, 2022), and may reflect the limited hyperplastic capacity of obese AT, which is more likely to expand through adipocyte hypertrophy (Ghaben and Scherer, 2019). Increased SAT adipogenic capacity in dairy cows might be fundamental in offsetting negative metabolic consequences of excessive concentrations of circulating free fatty acids during early postpartum of high producing dairy cows (Yung and Tak Mao, 2007;Gupta and Gupta, 2015).…”

“…Frontiers in Cell and Developmental Biology frontiersin.org macrophages (Jaitin et al, 2019;Vijay et al, 2020;Strieder-Barboza et al, 2022). There was a significant upregulation of several complement and complement receptor genes in MAC1, such as C3, CFI, CFB, CD55, CFH, CR2, C1QC, C1QB, and C1QA among others, suggesting MAC1 cells involvement on complement activation during inflammation in AT.…”

“…Recent studies using single-cell and single-nuclei RNA sequencing analysis (scRNA-seq and snRNA-seq, respectively) of AT in humans and mice revealed significant cell heterogeneity and functionally distinct subpopulations of adipocyte progenitor cells, endothelial cells, mature adipocytes, and among other cell types (Vijay et al, 2020;Emont et al, 2022;Strieder-Barboza et al, 2022). Furthermore, AT presents depot-and disease-specific molecularly and functionally distinct subpopulations, with important implications in the development of metabolic diseases.…”