IFN-γ orchestrates mesenchymal stem cell plasticity through the signal transducer and activator of transcription 1 and 3 and mammalian target of rapamycin pathways.
BACKGROUND
Mesenchymal stem cells (MSCs) display a therapeutic plasticity because of their ability to modulate immunity, foster tissue repair, and differentiate into mesodermal cells. IFN-γ has been described to differently affect human mesenchymal stem cell (hMSC) and mouse mesenchymal stem cell (mMSC) immunomodulation and differentiation, depending on the inflammatory milieu.


OBJECTIVE
We aimed at dissecting the relevant intracellular pathways through which IFN-γ affects MSC plasticity and the consequence of their manipulation on MSC functions.


METHODS
Modification of relevant IFN-γ-dependent pathways in mMSCs was carried out in vitro through gene silencing or chemical inhibition of key components. Functional outcomes were assessed by means of Western blotting, real-time PCR, differentiation, and proliferation assays on MSCs. The effect on T cells was addressed by T-cell proliferation assays; the effect of mammalian target of rapamycin (mTOR) manipulation in MSCs was studied in vivo in a mouse model of delayed-type hypersensitivity assay. To address whether similar mechanisms are involved also in hMSCs on IFN-γ stimulation, the effect of chemical inhibition on the same intracellular pathways was assessed by means of Western blotting, and the final outcome on immunomodulatory properties was evaluated based on real-time PCR and T-cell proliferation.


RESULTS
We revealed that in mMSCs IFN-γ-induced immunoregulation is mediated by early phosphorylation of signal transducer and activator of transcription (STAT) 1 and STAT3, which is significantly enhanced by an extracellular signal-regulated kinase 1/2-dependent mTOR inhibition, thereby promoting pSTAT1 nuclear translocation. Accordingly, after intracellular mTOR inhibition, MSCs augmented their ability to inhibit T-cell proliferation and control delayed-type hypersensitivity in vivo. Similarly, on mTOR blockade, hMSCs also enhanced their immunoregulatory features. A sustained exposure to IFN-γ led to inhibition of STAT3 activity, which in mMSCs resulted in an impaired proliferation and differentiation.


CONCLUSIONS
These results provide new insights about MSC intracellular pathways affected by IFN-γ, demonstrating that pharmacologic or genetic manipulation of MSCs can enhance their immunomodulatory functions, which could be translated into novel therapeutic approaches.
Dipartimento di Neuroscienze, Riabilitazione, Oftalmologia, Genetica e Scienze Materno-infantili, Facoltà di Medicina e Chirurgia, Università di Genova, Genoa, Italy; Center of Excellence for Biomedical Research (CEBR), Genoa, Italy.
Tiziana
T
Vigo
Laboratorio di Immunologia, Istituto di Endocrinologia e Oncologia Sperimentale, Consiglio Nazionale delle Ricerche (IEOS-CNR) c/o Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli "Federico II," Naples, Italy.
Claudio
C
Procaccini
Dipartimento di Neuroscienze, Riabilitazione, Oftalmologia, Genetica e Scienze Materno-infantili, Facoltà di Medicina e Chirurgia, Università di Genova, Genoa, Italy; Center of Excellence for Biomedical Research (CEBR), Genoa, Italy.
Giovanni
G
Ferrara
Department of Neurology, University of California, San Francisco, Calif.
Sergio
S
Baranzini
Department of Neurology, University of California, San Francisco, Calif.
Jorge R
JR
Oksenberg
Laboratorio di Immunologia, Istituto di Endocrinologia e Oncologia Sperimentale, Consiglio Nazionale delle Ricerche (IEOS-CNR) c/o Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli "Federico II," Naples, Italy; Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli "Federico II," Naples, Italy.
Giuseppe
G
Matarese
Nanophysics, Istituto Italiano di Tecnologia, Genoa, Italy.
Alberto
A
Diaspro
Dipartimento di Neuroscienze, Riabilitazione, Oftalmologia, Genetica e Scienze Materno-infantili, Facoltà di Medicina e Chirurgia, Università di Genova, Genoa, Italy; Center of Excellence for Biomedical Research (CEBR), Genoa, Italy.
Nicole
N
Kerlero de Rosbo
Dipartimento di Neuroscienze, Riabilitazione, Oftalmologia, Genetica e Scienze Materno-infantili, Facoltà di Medicina e Chirurgia, Università di Genova, Genoa, Italy; Center of Excellence for Biomedical Research (CEBR), Genoa, Italy; IRCCS AOU San Martino-IST, Genoa, Italy. Electronic address: auccelli@neurologia.unige.it.
Antonio
A
Uccelli
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D006801:Humans; D006968:Hypersensitivity, Delayed / Q000276:immunology; D007371:Interferon-gamma / Q000494:pharmacology*; D059630:Mesenchymal Stem Cells / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D050794:STAT1 Transcription Factor / Q000276:immunology*; D050796:STAT3 Transcription Factor / Q000276:immunology*; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000276:immunology*
D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D007371:Interferon-gamma; D058570:TOR Serine-Threonine Kinases
IFN-γ; T cells; immunomodulation; mammalian target of rapamycin; mesenchymal stem cells; signal transducer and activator of transcription 1; signal transducer and activator of transcription 3