# Characterisation of Mesenchymal Stromal Cells (MSCs) from Human Adult Thymus as a Potential Cell Source for Regenerative Medicine

## TL;DR

This study explores mesenchymal stromal cells from the human thymus as a potential regenerative medicine cell source due to their strong immunomodulatory properties.

## Contribution

The novel contribution is the characterization of thymus-derived mesenchymal stromal cells (ThyAdMSCs) as a new potential cell source for regenerative medicine.

## Key findings

- ThyAdMSCs showed high proliferation and expressed MSC markers without hematopoietic markers.
- ThyAdMSCs inhibited immune cell activation and reduced pro-inflammatory cytokines like IFNγ and TNFα.
- ThyAdMSCs could differentiate into adipocytes, osteocytes, and chondrocytes.

## Abstract

Background: Mesenchymal stem cell-based therapy may be indicated in ischaemic heart disease. The use of autologous adipose-derived mesenchymal stromal cells (AdMSCs) offers regenerative potential due to their paracrine effects. The aim of this study was to expand and characterise adult human thymus-derived MSCs harvested during open heart surgery with respect to their stem cell and paracrine properties. Methods: Enzymatically and non-enzymatically isolated human thymic AdMSCs (ThyAdMSCs) were cultured in xeno-free media containing pooled human platelet lysate (pPL). MSC characterisation was performed. Ex vivo expanded ThyAdMSCs were differentiated into three lineages. Proliferative capacity and immunomodulatory properties were assessed by proliferation assays and mixed lymphocyte reaction, respectively. Gene expression analysis was performed by qPCR. Results: Both isolation methods yielded fibroblast-like cells with plastic adherence and high proliferation. Flow cytometry revealed distinct expression of MSC markers in the absence of haematopoietic cell surface markers. Ex vivo expanded ThyAdMSCs could be differentiated into adipocytes, osteocytes, and chondrocytes. Activated peripheral blood mononuclear cells were significantly reduced when co-cultured with ThyAdMSCs, indicating their ability to inhibit immune cells in vitro. Gene expression analysis showed significantly less IFNγ and TNFα, indicating an alteration of the activated and pro-inflammatory state in the presence of ThyAdMSCs. Conclusions: These results demonstrate an efficient method to generate AdMSCs from human thymus. These MSCs have a strong immunomodulatory capacity and are, therefore, a promising cell source for regenerative medicine. The culture conditions are crucial for cells to proliferate in culture. Further research could explore the use of ThyAdMSCs or their secretome in surgical procedures.