Tissue Inhibitor of Matrix Metalloproteinases-1 Knockdown Suppresses the Proliferation of Human Adipose-Derived Stem Cells

IgE Immune Complexes Mitigate Eosinophilic Immune Responses through NLRC4 Inflammasome

Immune complexes (ICs) skew immune responses toward either a pro- or anti-inflammatory direction based on the type of stimulation. Immunoglobulin E (IgE) is associated with Th2 immune responses and known to activate innate immune cells. However, roles of antigen (Ag)-specific-IgE ICs in regulating human eosinophil responses remain elusive; therefore, this study builts upon the mechanism of which ovalbumin (Ova)-IgE ICs affects eosinophilic responses utilizing human EoL-1 cell line as a model. Eosinophils are granulocytes functioning through pattern recognition receptors (PRRs) and destructive granule contents in allergic inflammation and parasitic infections. One of the PRRs that eosinophils express is NLRC4, a member of the CARD domain containing nucleotide-binding oligomerization (NOD)-like receptor (NLR) family. Upon recognition of its specific ligand flagellin, NLRC4 inflammasome is formed and leads to the release of interleukin-1β (IL-1β). We exhibited that Ova-IgE ICs induced the NLRC4-inflammasome components, including NLRC4, caspase-1, intracellular IL-1β, and secretion of IL-1β, as well as the granule contents MMP9, TIMP1, and TIMP2 proteins via TLR2 signaling; these responses were suppressed, when NLRC4 inflammasome got actived in the presence of ICs. Furthermore, Ova-IgE ICs induced mRNA expressions of MMP9, TIMP2, and ECP and protein expressions of MMP9 and TIMP2 in EoL-1 through FcɛRII. Interestingly, TLR2 ligand and Ova-IgE ICs costimulation elevated the number of CD63+ cells, a degranulation marker, as compared to the native IgE. Collectively, our findings provide a mechanism for the impacts of Ova-IgE ICs on eosinophilic responses via NLRC4-inflammasome and may help understand eosinophil-associated diseases, including chronic eosinophilic pneumonia, eosinophilic esophagitis, eosinophilic granulomatosis, parasitic infections, allergy, and asthma.

SORLA is required for insulin-induced expansion of the adipocyte precursor pool in visceral fat

Visceral adipose tissue shows remarkable plasticity, constantly replacing mature adipocytes from an inherent pool of adipocyte precursors. The number of precursors is set in the juvenile organism and remains constant in adult life. Which signals drive precursor pool expansion in juveniles and why they operate in visceral but not in subcutaneous white adipose tissue (WAT) are unclear. Using mouse models, we identified the insulin-sensitizing receptor SORLA as a molecular factor explaining the distinct proliferative capacity of visceral WAT. High levels of SORLA activity in precursors of juvenile visceral WAT prime these cells for nutritional stimuli provided through insulin, promoting mitotic expansion of the visceral precursor cell pool in overfed juvenile mice. SORLA activity is low in subcutaneous precursors, blunting their response to insulin and preventing diet-induced proliferation of this cell type. Our findings provide a molecular explanation for the unique proliferative properties of juvenile visceral WAT, and for the genetic association of SORLA with visceral obesity in humans.

RAB37 Promotes Adipogenic Differentiation of hADSCs via the TIMP1/CD63/Integrin Signaling Pathway

The adipogenic differentiation ability of human adipose-derived mesenchymal stem cells (hADSCs) is critical for the construction of tissue engineering adipose, which shows promising applications in plastic surgery and regenerative medicine. RAB37 is a member of the small RabGTPase family and plays a critical role in vesicle trafficking. However, the role of RAB37 in adipogenic differentiation of hADSCs remains unclear. Here, we report that both the mRNA and protein levels of RAB37 fluctuated during adipogenic differentiation. Upregulation of RAB37 was observed at the early stage of adipogenic differentiation, which was accompanied by increased expression of transcription factors PPARγ2 and C/EBPα, and lipoprotein lipase (LPL). Overexpression of RAB37 promoted adipogenesis of hADSCs, as revealed by Oil Red O staining and increased expression of PPARγ2, C/EBPα, and LPL. Several upregulated cytokines related to RAB37-mediated adipogenic differentiation were identified using a cytokine array, including tissue inhibitor of matrix metalloproteinase 1 (TIMP1). ELISA confirmed that upregulation of RAB37 increased the secretion of TIMP1 by hADSCs. Proximity ligation assay showed that RAB37 interacts with TIMP1 directly. Knockdown of TIMP1 compromised RAB37-mediated adipogenic differentiation. In addition, TIMP1 binds membrane receptor CD63 and integrin β1. RAB37 promotes Tyr397 phosphorylation of FAK, an important protein kinase of the integrin β1 signaling. Moreover, both knockdown of CD63 and inhibitor of FAK impeded RAB37-mediated adipogenic differentiation. In conclusion, RAB37 positively regulates adipogenic differentiation of hADSCs via the TIMP1/CD63/integrin β1 signaling pathway.

Human adipose tissue-derived mesenchymal stem cells and their extracellular vesicles modulate lipopolysaccharide activated human microglia

Neurodegenerative diseases (NDs), such as Alzheimer's disease (AD), are driven by neuroinflammation triggered by activated microglial cells; hence, the phenotypic regulation of these cells is an appealing target for intervention. Human adipose tissue-derived mesenchymal stem cells (hAD-MSCs) may be a potential therapeutic candidate to treat NDs given their immunomodulatory properties. Evidence suggests that the mechanism of action of hAD-MSCs is through their secretome, which includes secreted factors such as cytokines, chemokines, or growth factors as well as extracellular vesicles (EVs). Recently, EVs have emerged as important mediators in cell communication given, they can transfer proteins, lipids, and RNA species (i.e., miRNA, mRNA, and tRNAs) to modulate recipient cells. However, the therapeutic potential of hAD-MSCs and their secreted EVs has not been fully elucidated with respect to human microglia. In this study, we determined the therapeutic potential of different hAD-MSCs doses (200,000, 100,000, and 50,000 cells) or their secreted EVs (50, 20, or 10 µg/ml), on human microglial cells (HMC3) that were activated by lipopolysaccharides (LPS). Upregulation of inducible nitric oxide synthase (iNOS), an activation marker of HMC3 cells, was prevented when they were cocultured with hAD-MSCs and EVs. Moreover, hAD-MSCs inhibited the secretion of proinflammatory factors, such as IL-6, IL-8, and MCP-1, while their secreted EVs promoted the expression of anti-inflammatory mediators such as IL-10 or TIMP-1 in activated microglia. The present data therefore support a role for hAD-MSCs and their secreted EVs, as potential therapeutic candidates for the treatment of NDs.

TIMP-1 downregulation modulates miR-125a-5p expression and triggers the apoptotic pathway

Matrix metalloproteinases and their natural inhibitors (TIMPs) are important elements in a wide range of oncology settings. Elevated levels of tissue inhibitor of metalloproteinase-1 (TIMP-1) have often been associated with increased tumorigenesis. This has been demonstrated in a number of clinical and experimental models which include breast, gastric, colorectal and non-small cell lung carcinoma (NSCLC). Our earlier studies have identified increased angiogenic activity and aggressive tumor kinetics in TIMP-1 overexpressing H2009 lung adenocarcinoma cells. TIMP-1 overexpression has also been implicated in antiapoptotic responses, inducing a significant upregulation of Bcl-2. These TIMP-1 functions have been shown to be MMP-independent and provide insight into its pleiotropic activities. The current study examines microRNA (miRNA) interactions with this molecule. We have sought to define the relationship between TIMP-1 and miRNA by knocking down TIMP-1 in high TIMP-1 expressing lung adenocarcinoma cell lines. TIMP-1 knockdown resulted in increased expression of miR-125a-5p with a concomitant increase in apoptosis and attenuation of the tumorigenic features of these cells. We have identified TIMP-1 as a bona fide target of miR-125a-5p, and their interaction resulted in an increase in p53 expression. We further corroborated our in vitro data with patient samples, which exhibited an inverse correlation between TIMP-1 and miR-125a-5p expression. Our study lends support to the notion that elevated TIMP-1 levels, which are frequently associated with poor prognosis, cause aberrant modulation of miRNAs.