Adipose tissue mitochondrial dysfunction in human obesity is linked to a specific DNA methylation signature in adipose-derived stem cells

Background: A functional population of adipocyte precursors, termed adipose-derived stromal/stem cells (ASCs), is crucial for proper adipose tissue (AT) expansion, lipid handling, and prevention of lipotoxicity in response to chronic positive energy balance. We previously showed that obese human subjects contain a dysfunctional pool of ASCs. Elucidation of the mechanisms underlying abnormal ASC function might lead to therapeutic interventions for prevention of lipotoxicity by improving the adipogenic capacity of ASCs. Methods: Using epigenome-wide association studies, we explored the impact of obesity on the methylation signature of human ASCs and their differentiated counterparts. Mitochondrial phenotyping of lean and obese ASCs was performed. TBX15 loss- and gain-of-function experiments were carried out and western blotting and electron microscopy studies of mitochondria were performed in white AT biopsies from lean and obese individuals. Results: We found that DNA methylation in adipocyte precursors is significantly modified by the obese environment, and adipogenesis, inflammation, and immunosuppression were the most affected pathways. Also, we identified TBX15 as one of the most differentially hypomethylated genes in obese ASCs, and genetic experiments revealed that TBX15 is a regulator of mitochondrial mass in obese adipocytes. Accordingly, morphological analysis of AT from obese subjects showed an alteration of the mitochondrial network, with changes in mitochondrial shape and number. Conclusions: We identified a DNA methylation signature in adipocyte precursors associated with obesity, which has a significant impact on the metabolic phenotype of mature adipocytes

In vitro mesenchymal trilineage differentiation and extracellular matrix production by adipose and bone marrow derived adult equine multipotent stromal cells on a collagen scaffold

Directed differentiation of adult multipotent stromal cells (MSC) is critical for effective treatment strategies. This study was designed to evaluate the capability of equine MSC from bone marrow (BMSC) and adipose tissue (ASC) on a type I collagen (COLI) scaffold to undergo chondrogenic, osteogenic and adipogenic differentiation and form extracellular matrix (ECM) in vitro. Following determination of surface antigen expression, MSC were loaded into scaffolds in a perfusion bioreactor and loading efficiency was quantified. Cell-scaffold constructs were assessed after loading and 7, 14 and 21 days of culture in stromal or induction medium. Cell number was determined with DNA content, cell viability and spatial uniformity with confocal laser microscopy and cell phenotype and matrix production with light and scanning electron microscopy and mRNA levels. The MSC were positive for CD29 (>90 %), CD44 (>99 %), and CD105 (>60 %). Loading efficiencies were >70 %. The ASC and BMSC cell numbers on scaffolds were affected by culture in induction medium differently. Viable cells remained uniformly distributed in scaffolds for up to 21 days and could be directed to differentiate or to maintain an MSC phenotype. Micro- and ultrastructure showed lineage-specific cell and ECM changes. Lineage-specific mRNA levels differed between ASC and BMSC with induction and changed with time. Based on these results, equine ASC and BMSC differentiate into chondrogenic, osteogenic and adipogenic lineages and form ECM similarly on COLI scaffolds. The collected data supports the potential for equine MSC-COLI constructs to support diverse equine tissue formation for controlled biological studies

Comparison of the Regenerative Potential for Lung Tissue of Mesenchymal Stromal Cells from Different Sources/Locations Within the Body

To date, bone marrow-derived mesenchymal stromal cells (MSCs) have been considered the golden standard among MSC cell-based therapies. However, the harvesting of bone marrow is a highly invasive procedure and the number of MSCs isolated is low, and it declines with increasing age. MSCs with immune-regulatory and regenerative properties can be isolated from many different tissues; however, bone marrow-derived MSCs are so far the most thoroughly characterized MSC population. Despite an increased interest in using MSCs for clinical approaches in severe lung disorders, the biological function of MSCs after administration is not completely known, in particular, of MSCs extracted from other tissues than bone marrow aspirates. MSCs do not engraft after infusion, and data demonstrate that the majority of MSCs tend to be cleared from the lungs within a few days, suggesting a fast, short acting, and paracrine effect. Following activation, MSCs produce and secrete mediators, the secretome, that influence the microenvironment and the surrounding resident cells in order to modulate and repair damaged tissue. Exploring the MSC secretome has attracted much attention, and today it is known to consist of an array of molecules that is important for their regenerative and protective abilities. However, recent data suggest that the secretome profiles differ significantly depending on the MSC source, donor site, and external stimulation. In addition, the microenvironment that the infused MSCs encounter most likely plays an important role in influencing the therapeutic effect of MSCs. The composition of the microenvironment is unique in every tissue type and varies by developmental age. Changes in both stiffness and composition drastically affect MSC fate and function. The aim of this chapter is to provide a comparison of the potential of MSCs obtained from different cellular sources, and how they can be used as therapeutic agents to treat lung disorders