A Human Omentum-Specific Intermesothelial Fibroblast Population Inhibits Adipogenesis by Secreting IGFBP2

Background and Research Objective

With the growing prevalence of obesity and metabolic diseases, the plasticity and heterogeneity of adipose tissue have become research hotspots. Different regions of adipose tissue exhibit distinct metabolic characteristics; for example, subcutaneous fat (SC) is considered metabolically healthy, while visceral fat (including omental fat, OM) is regarded as metabolically unhealthy. Although previous studies have revealed the heterogeneity of stromal vascular fraction (SVF) cells in murine and human adipose tissues, the cellular and functional variability of adipose stem cells (ASC) and precursor cells (ASPC) in specific fat storage regions remains insufficiently understood.

To fill this knowledge gap, Radiana Ferrero’s team at the Swiss Federal Institute of Technology in Lausanne (EPFL) performed single-cell and bulk RNA sequencing on over 30 samples. This study comprehensively described the heterogeneity and functional characteristics of stromal cell populations from four different human fat storage regions, particularly identifying an omentum-specific fibroblast population that highly expresses IGFBP2 and elucidates its mechanism for inhibiting adipogenesis.

Authors and Publication Source

This paper was authored by Radiana Ferrero, Pernille Yde Rainer, Marie Rumpler, and others from the Swiss Federal Institute of Technology in Lausanne, the Swiss Institute of Bioinformatics, Lausanne University Hospital, and Concept Clinic in Geneva. The article was published in Cell Metabolism on July 2, 2024, by Elsevier. The corresponding author is Bart Deplancke (bart.deplancke@epfl.ch).

Detailed Steps of the Original Research

Experimental Process and Subjects

1. Sample Collection and Preliminary Processing

   • SVF component cells were isolated from subcutaneous fat (SC) from 20 donors, perirenal fat (PR) from 8 donors, omental fat (OM) from 19 donors, and mesenteric fat (MC) from 4 donors, generating over 30 samples for subsequent single-cell and bulk RNA sequencing analyses.
   • These samples underwent adipogenesis induction, with lipid droplet staining and quantification at 0 and 14 days to assess the adipogenic capacity of each fat storage region.

2. Single-Cell RNA Sequencing (scRNA-seq) and Data Analysis

   • Single-cell RNA sequencing was performed on SC, OM, MC, and PR fat tissue samples from 3, 3, 2, and 3 donors, respectively, analyzing a total of 34,126 cells.
   • Data from each sample were analyzed independently, revealing cellular heterogeneity within and between different fat storage regions. The data were verified and integrated through multiple steps, identifying at least two major HASPC subpopulations (HASCS and HPREAS).

3. Gene Expression Analysis and Sorting Strategy Development

   • Based on gene expression markers, a strategy was developed for sorting different HASPC subpopulations, including CD26-positive cells, double-negative cells, and VAP1-positive cells.
   • The proliferation and adipogenic potential of each sorted cell subpopulation were tested, revealing that CD26-positive cells had high proliferation capacity but low adipogenic potential, while VAP1-positive cells exhibited the opposite.

Data Results

1. Adipogenic Capacity of Fat Storage Regions

   • SVF cells from OM and MC fat tissue formed almost no lipid droplets under adipogenic induction, whereas SC and PR fat tissue generated significant lipid droplets, reflecting differences in adipogenic capacity across fat storage regions.
   • SVF cells from each fat storage region exhibited distinct gene expression patterns; for instance, gene expression patterns related to inflammatory responses were observed in OM samples.

2. Description of Cell Subpopulations

   • At least two major HASPC subpopulations, HASCS and HPREAS, were identified in all analyzed fat storage regions. Each subpopulation displayed specific gene expression and functional characteristics.
   • A fibroblast population specific to OM and highly expressing IGFBP2 was identified, which demonstrated the ability to inhibit adipogenesis both in vitro and in vivo.

Research Conclusions, Significance, and Highlights

This study provides new insights into the heterogeneity of human adipose tissue, revealing unique gene expression and functional characteristics of specific cell subpopulations in different fat storage regions. The main highlights are as follows:

1. OM-Specific Anti-Adipogenic Cell Population

   • An OM-specific fibroblast population highly expressing IGFBP2 was identified and functionally validated. These cells can inhibit the adipogenesis of adipose stem cells and precursor cells by secreting IGFBP2.
   • IGFBP2 plays a key anti-adipogenic role during adipocyte differentiation by signaling through integrin receptors.

2. Perception of Cellular Heterogeneity and Functional Diversity

   • The gene expression differences among cell populations specific to fat storage regions reflect their distinct functions under physiological and pathological conditions.
   • Single-cell RNA sequencing revealed the existence of at least two HASPC subpopulations and their different gene expression characteristics, further confirming the cellular heterogeneity of adipose tissue.

3. Potential Clinical Applications

   • The identification and functional validation of the OM-specific cell population provide important clues for understanding the role of visceral fat in metabolic diseases and may offer new targets for developing therapeutic strategies.

Summary

Through single-cell and bulk RNA sequencing analyses of human fat storage regions, this study reveals the adipogenic capacity and cellular heterogeneity of each region, particularly identifying an OM-specific fibroblast population highly expressing IGFBP2 and its anti-adipogenic mechanism. These findings provide new insights into the understanding of adipose tissue function and metabolic regulation and lay the foundation for future related clinical research and the development of therapeutic strategies.