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TRANSLATIONAL PHYSIOLOGY

Human mesenchymal stem cells stimulated by TNF-, LPS, or hypoxia produce growth factors by an NFB- but not JNK-dependent mechanism

Departments of ¹Surgery, ²Pulmonary and Critical Care Medicine, ³Cellular and Integrative Physiology, and the ⁴Center for Immunobiology, Indiana University School of Medicine, Indianapolis, Indiana

Submitted 21 September 2007 ; accepted in final form 24 January 2008

ABSTRACT

Understanding the mechanisms by which adult stem cells produce growth factors may represent an important way to optimize their beneficial paracrine and autocrine effects. Components of the wound milieu may stimulate growth factor production to promote stem cell-mediated repair. We hypothesized that tumor necrosis factor- (TNF-), endotoxin (LPS), or hypoxia may activate human mesenchymal stem cells (MSCs) to increase release of vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF2), insulin-like growth factor 1 (IGF-1), or hepatocyte growth factor (HGF) and that nuclear factor-B (NFB), c-Jun NH₂-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) mediates growth factor production from human MSCs. To study this, human MSCs were harvested, passaged, divided into four groups (100,000 cells, triplicates) and treated as follows: 1) with vehicle; 2) with stimulant alone [24 h LPS (200 ng/ml), 24 h TNF- (50 ng/ml), or 24 h hypoxia (1% O₂)]; 3) with inhibitor alone [NFB (PDTC, 1 mM), JNK (TI-JIP, 10 µM), or ERK (ERK Inhibitor II, 25 µM)]; and 4) with stimulant and the various inhibitors. After 24 h incubation, MSC activation was determined by measuring supernatants for VEGF, FGF2, IGF-1, or HGF (ELISA). TNF-, LPS, and hypoxia significantly increased human MSC VEGF, FGF2, HGF, and IGF-1 production versus controls. Stem cells exposed to injury demonstrated increased activation of NFB, ERK, and JNK. VEGF, FGF2, and HGF expression was significantly reduced by NFB inhibition (50% decrease) but not ERK or JNK inhibition. Moreover, ERK, JNK, and NFB inhibitor alone did not activate MSC VEGF expression over controls. Various stressors activate human MSCs to increase VEGF, FGF2, HGF, and IGF-1 expression, which depends on an NFkB mechanism.

vascular endothelial growth factor; fibroblast growth factor 2; hepatocyte growth factor; insulin-like growth factor 1; mitogen-activated protein kinase

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