Mesenchymal Stem Cell Migration and Proliferation Are Mediated by Hypoxia-Inducible Factor-1α Upstream of Notch and SUMO Pathways

Abstract

Mesenchymal stem cells (MSCs) are effective in treating several pathologies. We and others have demonstrated that hypoxia or hypoxia-inducible factor 1 alpha (HIF-1α) stabilization improves several MSC functions, including cell adhesion, migration, and proliferation, thereby increasing their therapeutic potential. To further explore the mechanisms induced by HIF-1α in MSCs, we studied its relationship with Notch signaling and observed that overexpression of HIF-1α in MSCs increased protein levels of the Notch ligands Jagged 1–2 and Delta-like (Dll)1, Dll3, and Dll4 and potentiated Notch signaling only when this pathway was activated. Crosstalk between HIF and Notch resulted in Notch-dependent migration and spreading of MSCs, which was abolished by γ-secretase inhibition. However, the HIF-1-induced increase in MSC proliferation was independent of Notch signaling. The ubiquitin family member, small ubiquitin-like modifier (SUMO), has important functions in many cellular processes and increased SUMO1 protein levels have been reported in hypoxia. To investigate the potential involvement of SUMOylation in HIF/Notch crosstalk, we measured general SUMOylation levels and observed increased SUMOylation in HIF-1-expressing MSCs. Moreover, proliferation and migration of MSCs were reduced in the presence of a SUMOylation inhibitor, and this effect was particularly robust in HIF-MSCs. Immunoprecipitation studies demonstrated SUMOylation of the intracellular domain of Notch1 (N1ICD) in HIF-1-expressing MSCs, which contributed to Notch pathway activation and resulted in increased levels of N1ICD nuclear translocation as assessed by subcellular fractionation. SUMOylation of N1ICD was also observed in HEK293T cells with stabilized HIF-1α expression, suggesting that this is a common mechanism in eukaryotic cells. In summary, we describe, for the first time, SUMOylation of N1ICD, which is potentiated by HIF signaling. These phenomena could be relevant for the therapeutic effects of MSCs in hypoxia or under conditions of HIF stabilization.

SUMOylation in brain ischemia: Patterns, targets, and translational implications

“…Indeed, recent data have shown that increased SUMOylation is associated with increased pathotropism and proliferation of mesenchymal stem cells. 89 In stroke, transplanted stem cells have been shown to exert beneficial effects via structural replacement of damaged tissue and a litany of other immunomodulatory and neurotrophic actions. [90][91][92] Unfortunately, the clinical translation of such promising therapies continues to remain elusive, in part due to the limited persistence/survivability of grafted cells within the hostile ischemic microenvironment.…”

Application of the allogenic mesenchymal stem cells in the therapy of the bladder tuberculosis

“…Numerous attempts to restore the structure and function of the UB using the injection of MSCs suspension, as well as transplantation of various scaffolds seeded with stem cells, clearly demonstrated therapeutic efficacy (Coutu, Mahfouz, Loutochin, Galipeau, & Corcos, 2014;Kanematsu et al, 2005;Kim 2016; Lee et al, 2012). The main mechanisms of MSCs in reconstitution of bladder dysfunction were attributed to the cells migration, differentiation, and paracrine effects (Ciria et al, 2017;DeCoppi et al, 2007;Kanno et al, 2014). Recently, Lee et al reported that transplantation of human MSCs labelled with nanoparticles containing superparamagnetic iron oxide into the bladder inhibited bladder fibrosis and increased blood flow and decreased tissue hypoxia, which contributed to improvement in histopathological and functional parameters.…”

Perfusion bioreactor culture of adipose-derived stromal cells on decellularized adipose tissue scaffolds enhancesin vivoregeneration

“…The ASCs cultured both statically and dynamically under 2% O2 were also shown to express HIF-1α, consistent with hypoxia in adipose tissue being < 5% O2 59,60 . HIF-1α activation is associated with MSC proliferation 61,62 , which may have contributed to the enhanced Ki-67 expression in the hypoxic dynamic group. A previous study by Choi et al demonstrated that culturing human ASCs under 2% O2 increased proliferation relative to culture under ~21% O2 through HIF-1α-mediated mechanisms 26 .…”