# Effects of Bariatric Surgery-Related Weight Loss on the Characteristics, Metabolism, and Immunomodulation of Adipose Stromal/Stem Cells in a Follow-Up Study

## TL;DR

Weight loss after bariatric surgery improves the metabolic and immunological properties of fat-derived stem cells, but not fully restoring their anti-inflammatory functions.

## Contribution

This study is the first to show how weight loss affects the immunomodulatory capacity of adipose stem cells in a longitudinal design.

## Key findings

- Weight loss reduced leptin and increased adiponectin, improved mitochondrial function, and decreased adipocyte size.
- Weight loss downregulated proinflammatory genes and cytokines in ASC monocultures but increased proinflammatory properties in macrophage cocultures.
- ASCs from weight-reduced donors showed improved immunosuppressive functions in macrophage cocultures, but not full recovery.

## Abstract

Background: The success of adipose stromal/stem cell (ASC)-based therapies may depend on donor characteristics such as body mass index (BMI). A high BMI may negatively impact the therapeutic potential of ASCs, but the effects of weight loss on ASC-mediated immunoregulation have not been extensively studied.

Methods: ASCs were obtained from donors with obesity (obASCs) undergoing bariatric surgery and from the same donors after weight loss (wlASCs). Plasma samples, adipose tissue histology, and ASC characteristics, such as mitochondrial respiration and inflammatory factors, were studied before and after weight loss. The immunomodulatory capacity of ob/wlASCs was evaluated in cocultures with prepolarized and preactivated proinflammatory (M1) and anti-inflammatory (M2) macrophages by determining macrophage surface markers, gene expression, and cytokine secretion.

Results: Weight loss significantly decreased plasma leptin levels and increased adiponectin levels. After weight loss, crown-like structures (CLSs) were undetectable, and the adipocyte size decreased. Weight loss significantly improved mitochondrial respiration in ASCs and resulted in a notable increase in their proliferative capacity. The proinflammatory marker genes tumor necrosis factor alpha (TNF-α), chemokine ligand 5 (CCL5), and cyclooxygenase-2 (COX2), as well as the proinflammatory cytokine interleukin 12p70 (IL-12p70), were significantly downregulated, while the anti-inflammatory gene tumor necrosis factor-inducible gene 6 (TSG6) was also significantly downregulated in ASC monocultures after weight loss. Following weight loss, ASCs exhibited increased proinflammatory properties when cocultured with macrophages, characterized by the downregulation of anti-inflammatory factors, along with the upregulation of several proinflammatory factors, compared with the effects of macrophage monocultures. Conversely, wlASCs demonstrated improved immunosuppressive functions in coculture with macrophages, as indicated by the upregulation of TSG6 gene expression and interleukin 4 (IL-4) secretion.

Conclusions: Weight loss improved donors' metabolic health and partially recovered ASCs' anti-inflammatory gene expression and cytokine secretion profiles in monocultures. However, it was inadequate to fully restore the immunosuppressive functions of ASCs in cocultures with macrophages. Therefore, not only donor BMI but also weight loss history, among other donor characteristics, might be considered for optimal ASC-based therapy.