Pre-conditioning mesenchymal stromal cell spheroids for immunomodulatory paracrine factor secretion.
OBJECTIVE
Mesenchymal stromal cells (MSCs) exhibit the inherent potential to regulate multiple signaling pathways and cell types that contribute to the pathogenesis of inflammatory and immune diseases. However, more recent studies have suggested that the secretion of immunomodulatory factors by MSCs can be enhanced by three-dimensional aggregation or pro-inflammatory cytokine treatment.


METHODS
Human MSC spheroids were formed by forced aggregation into agarose micro-wells and subsequently cultured in either minimal essential medium alpha supplemented with fetal bovine serum or serum-free, defined MesenCult-XF medium (STEMCELL Technologies, Vancouver, Canada). A subset of the spheroids were treated with pro-inflammatory cytokines interferon (IFN)-γ or tumor necrosis factor (TNF)-α or both for 4 days. Immunomodulatory factor (prostaglandin E2, indoleamine 2,3-dioxygenase, transforming growth factor-β1 and interleukin-6) secretion was quantified after 4 days of culture, and the immunomodulatory activity of MSCs was assessed by quantifying activated macrophage expression of TNF-α after trans-well co-culture.


RESULTS
Culturing human MSCs as three-dimensional aggregates increased secretion of immunomodulatory paracrine factors, which was enhanced further by treatment with IFN-γ and TNF-α, demonstrating that these parameters can synergistically enhance endogenous human MSC immunomodulatory properties. However, immunomodulatory factor secretion was found to be highly dependent on the composition of cell culture medium. Human MSCs cultured in MesenCult-XF medium displayed significantly less expression of prostaglandin E2, indoleamine 2,3-dioxygenase, transforming growth factor-β1 and interleukin-6 compared with human MSCs cultured in medium supplemented with fetal bovine serum. Finally, pre-conditioning of human MSC spheroids with IFN-γ and TNF-α resulted in greater immunomodulatory activity in a macrophage co-culture assay.


CONCLUSIONS
Altogether, engineering the environment of human MSCs to develop pre-conditioning strategies for enhancing human MSC immunomodulation may be a simple approach for improving MSC-based therapies for the treatment of inflammatory and immune diseases.
The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, USA.
Joshua A
JA
Zimmermann
The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, USA; The Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA. Electronic address: todd.mcdevitt@bme.gatech.edu.
Todd C
TC
McDevitt
D002478:Cells, Cultured; D018920:Coculture Techniques; D003470:Culture Media / Q000737:chemistry; D015232:Dinoprostone / Q000378:metabolism; D006801:Humans; D056747:Immunomodulation; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000378:metabolism; D007371:Interferon-gamma / Q000276:immunology; D015850:Interleukin-6 / Q000378:metabolism; D008262:Macrophage Activation; D045164:Mesenchymal Stem Cell Transplantation; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D019899:Paracrine Communication; D018874:Spheroids, Cellular / Q000166:cytology*; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D019172:Transplantation Conditioning; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism*
D003470:Culture Media; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D015850:Interleukin-6; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D015232:Dinoprostone
immunomodulation; macrophage; mesenchymal stromal cells; paracrine factors; spheroid