Mirna biogenesis pathway is differentially regulated during adipose derived stromal/stem cell differentiation

Declined adipogenic potential of senescent MSCs due to shift in insulin signaling and altered exosome cargo

Multipotent mesenchymal stromal cells (MSCs) maintain cellular homeostasis and regulate tissue renewal and repair both by differentiating into mesodermal lineage, e.g., adipocytes, or managing the functions of differentiated cells. Insulin is a key physiological inducer of MSC differentiation into adipocytes, and disturbances in MSC insulin sensitivity could negatively affect adipose tissue renewal. During aging, regulation and renewal of adipose tissue cells may be disrupted due to the altered insulin signaling and differentiation potential of senescent MSCs, promoting the development of serious metabolic diseases, including metabolic syndrome and obesity. However, the potential mechanisms mediating the dysfunction of adipose-derived senescent MSC remains unclear. We explored whether aging could affect the adipogenic potential of human adipose tissue-derived MSCs regulated by insulin. Age-associated senescent MSCs (isolated from donors older than 65 years) and MSCs in replicative senescence (long-term culture) were treated by insulin to induce adipogenic differentiation, and the efficiency of the process was compared to MSCs from young donors. Insulin-dependent signaling pathways were explored in these cells. We also analyzed the involvement of extracellular vesicles secreted by MSCs (MSC-EVs) into the regulation of adipogenic differentiation and insulin signaling of control and senescent cells. Also the microRNA profiles of MSC-EVs from aged and young donors were compared using targeted PCR arrays. Both replicatively and chronologically senescent MSCs showed a noticeably decreased adipogenic potential. This was associated with insulin resistance of MSCs from aged donors caused by the increase in the basal level of activation of crucial insulin-dependent intracellular effectors ERK1/2 and Akt. To assess the impact of the paracrine cross-talk of MSCs, we analyzed microRNAs profile differences in MSC-EVs and revealed that senescent MSCs produced EVs with increased content of miRNAs targeting components of insulin-dependent signaling cascade PTEN, MAPK1, GAREM1 and some other targets. We also confirmed these data by differentiation of control MSCs in the presence of EVs from senescent cells and vice versa. Thus, aging attenuated the adipogenic potential of MSCs due to autocrine or paracrine-dependent induction of insulin resistance associated with the specific changes in MSC-EV cargo.

Lymphedema alters lipolytic, lipogenic, immune and angiogenic properties of adipose tissue: a hypothesis-generating study in breast cancer survivors

Later stages of secondary lymphedema are associated with the massive deposition of adipose tissue (AT). The factors driving lymphedema-associated AT (LAT) expansion in humans remain rather elusive. We hypothesized that LAT expansion could be based on alterations of metabolic, adipogenic, immune and/or angiogenic qualities of AT. AT samples were acquired from upper limbs of 11 women with unilateral breast cancer-related lymphedema and 11 healthy women without lymphedema. Additional control group of 11 female breast cancer survivors without lymphedema was used to assess systemic effects of lymphedema. AT was analysed for adipocyte size, lipolysis, angiogenesis, secretion of cytokines, immune and stem cell content and mRNA gene expression. Further, adipose precursors were isolated and tested for their proliferative and adipogenic capacity. The effect of undrained LAT- derived fluid on adipogenesis was also examined. Lymphedema did not have apparent systemic effect on metabolism and cytokine levels, but it was linked with higher lymphocyte numbers and altered levels of several miRNAs in blood. LAT showed higher basal lipolysis, (lymph)angiogenic capacity and secretion of inflammatory cytokines when compared to healthy AT. LAT contained more activated CD4+ T lymphocytes than healthy AT. mRNA levels of (lymph)angiogenic markers were deregulated in LAT and correlated with markers of lipolysis. In vitro, adipose cells derived from LAT did not differ in their proliferative, adipogenic, lipogenic and lipolytic potential from cells derived from healthy AT. Nevertheless, exposition of preadipocytes to LAT-derived fluid improved their adipogenic conversion when compared with the effect of serum. This study presents results of first complex analysis of LAT from upper limb of breast cancer survivors. Identified LAT alterations indicate a possible link between (lymph)angiogenesis and lipolysis. In addition, our in vitro results imply that AT expansion in lymphedema could be driven partially by exposition of adipose precursors to undrained LAT-derived fluid.

The importance of cellular and exosomal miRNAs in mesenchymal stem cell osteoblastic differentiation

The differentiation of osteoblasts is under complex regulation that includes autocrine and paracrine signaling from MSCs. Exosomes are important components of the MSC secretome and their cargo contains numerous miRNAs. In this study, the importance of MSC miRNAs in modulation of osteoblastic differentiation was examined by global reduction of miRNA biosynthesis in Dicer knock down hMSCs. We additionally impaired hMSC responses to miRNAs by knockdown of Argonaute 2 expression. Knockdown of Dicer and Argonaute 2 both reduced osteoblastic differentiation of hMSCs. This was observed at the levels of hMSC culture mineralization and osteoblastic gene expression. The treatment of Dicer deficient hMSCs with wild type hMSC exosomes effectively recovered the impaired osteoblastic differentiation. Dicer knockdown reduced the quantity and diversity of miRNAs present in hMSC exosomes. miRSeq data and KEGG analysis implicated the miRNA-dependent effects on multiple osteoinductive pathways in Dicer deficient cells, including the Hippo signaling and TGF-beta signaling pathways. Treatment of hMSCs with mimics of miRNAs significantly downregulated in Dicer knockdown cells recovered functions of exosome-mediated signaling in hMSCs. These results indicate that hMSC exosomes exert miRNA-dependent control that contributes to osteoblastic differentiation.

Altered Regulation of adipomiR Editing with Aging

Adipose dysfunction with aging increases risk to insulin resistance and other chronic metabolic diseases. We previously showed functional changes in microRNAs involved in pre-adipocyte differentiation with aging resulting in adipose dysfunction. However, the mechanisms leading to this dysfunction in microRNAs in adipose tissue (adipomiRs) during aging are not well understood. We determined the longitudinal changes in expression of adipomiRs and studied their regulatory mechanisms, such as miRNA biogenesis and editing, in an aging rodent model, with Fischer344 × Brown-Norway hybrid rats at ages ranging from 3 to 30 months (male/females, n > 8). Expression of adipomiRs and their edited forms were determined by small-RNA sequencing. RT-qPCR was used to measure the mRNA expression of biogenesis and editing enzymes. Sanger sequencing was used to validate editing with aging. Differential expression of adipomiRs involved in adipocyte differentiation and insulin signaling was altered with aging. Sex- and age-specific changes in edited adipomiRs were observed. An increase in miRNA biogenesis and editing enzymes (ADARs and their splice variants) were observed with increasing age, more so in female than male rats. The adipose dysfunction observed with age is attributed to differences in editing of adipomiRs, suggesting a novel regulatory pathway in aging.

MicroRNA-30a regulates chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells through targeting Sox9

Cartilage injury is difficult to repair since the cartilage tissue lacks self-restoration ability. Improved formation of chondrocytes differentiated from the mesenchymal stem cells (MSC) by genetic regulation is a potentially promising therapeutic option. SOX9 is a critical transcription factor for mesenchymal condensation prior to chondrogenesis. Previous studies demonstrated that several microRNAs (miRNAs or miRs) play a critical role in the chondrogenic differentiation of MSCs. However, the interactional relations between miR-30a and SOX9 during chondrogenic differentiation of MSCs need to be further elucidated. In the present study, human bone marrow-derived mesenchymal stem cells have been isolated and induced into chondrogenic differentiation to imitate the cartilage formation in vitro. Additionally, the expression levels of several miRNAs that were reported to interact with the SOX9 3'untranslated region (UTR) were examined by using reverse transcription-quantitative PCR. The interactional relations between candidate miRNAs and SOX9 were verified with the transfection of a miRNA mimic or inhibitor and a luciferase reporter gene assay. The results indicate that miR-30a and miR-195 were consistently increased during MSC chondrogenic differentiation. Additionally, the binding of miR-30a to the SOX9 3UTR was verified. Then, the authors upregulated the expression of miR-30a and found that MSC chondrogenic differentiation was inhibited. Taken together, the results of the present study demonstrate that miR-30a has a negative regulatory effect on MSC chondrogenic differentiation by targeting SOX9. Advances in epigenetic regulating methods will likely be the future of systemic treatment of cartilage injury.

RNAase III-Type Enzyme Dicer Regulates Mitochondrial Fatty Acid Oxidative Metabolism in Cardiac Mesenchymal Stem Cells

Cardiac mesenchymal stem cells (C-MSC) play a key role in maintaining normal cardiac function under physiological and pathological conditions. Glycolysis and mitochondrial oxidative phosphorylation predominately account for energy production in C-MSC. Dicer, a ribonuclease III endoribonuclease, plays a critical role in the control of microRNA maturation in C-MSC, but its role in regulating C-MSC energy metabolism is largely unknown. In this study, we found that Dicer knockout led to concurrent increase in both cell proliferation and apoptosis in C-MSC compared to Dicer floxed C-MSC. We analyzed mitochondrial oxidative phosphorylation by quantifying cellular oxygen consumption rate (OCR), and glycolysis by quantifying the extracellular acidification rate (ECAR), in C-MSC with/without Dicer gene deletion. Dicer gene deletion significantly reduced mitochondrial oxidative phosphorylation while increasing glycolysis in C-MSC. Additionally, Dicer gene deletion selectively reduced the expression of β-oxidation genes without affecting the expression of genes involved in the tricarboxylic acid (TCA) cycle or electron transport chain (ETC). Finally, Dicer gene deletion reduced the copy number of mitochondrially encoded 1,4-Dihydronicotinamide adenine dinucleotide (NADH): ubiquinone oxidoreductase core subunit 6 (MT-ND6), a mitochondrial-encoded gene, in C-MSC. In conclusion, Dicer gene deletion induced a metabolic shift from oxidative metabolism to aerobic glycolysis in C-MSC, suggesting that Dicer functions as a metabolic switch in C-MSC, which in turn may regulate proliferation and environmental adaptation.

The cross-talk between adipokines and miRNAs in health and obesity-mediated diseases

BACKGROUND

Multiple studies have revealed a direct correlation between obesity and the development of multiple comorbidities, including metabolic diseases, cardiovascular disorders, chronic inflammatory disease, and cancers. However, the molecular mechanism underlying the link between obesity and the progression of these diseases is not completely understood. Adipokines are factors that are secreted by adipocytes and play a key role in whole body homeostasis. Collaboratively, miRNAs are suggested to have key functions in the development of obesity and obesity-related disorders. Based on recently emerging evidence, obesity leads to the dysregulation of both adipokines and obesity-related miRNAs. In the present study, we described the correlations between obesity and its related diseases that are mediated by the mutual regulatory effects of adipokines and miRNAs.

METHODS

We reviewed current knowledge of the modulatory effects of adipokines on miRNAs activity and their relevant functions in pathological conditions and vice versa.

RESULTS

Our research reveals the ability of adipokines and miRNAs to control the expression and activity of the other class of molecules, and their effects on obesity-related diseases.

CONCLUSIONS

This study may help researchers develop a roadmap for future investigations and provide opportunities to develop new therapeutic and diagnostic methods for treating obesity-related diseases.