Myocardin-A enhances expression of promyogenic genes without depressing telomerase activity in adipose tissue-derived mesenchymal stem cells

Telomerase therapy reverses vascular senescence and extends lifespan in progeria mice

AIMS

Hutchinson-Gilford progeria syndrome (HGPS) is an accelerated ageing syndrome associated with premature vascular disease and death due to heart attack and stroke. In HGPS a mutation in lamin A (progerin) alters nuclear morphology and gene expression. Current therapy increases the lifespan of these children only modestly. Thus, greater understanding of the underlying mechanisms of HGPS is required to improve therapy. Endothelial cells (ECs) differentiated from induced pluripotent stem cells (iPSCs) derived from these patients exhibit hallmarks of senescence including replication arrest, increased expression of inflammatory markers, DNA damage, and telomere erosion. We hypothesized that correction of shortened telomeres may reverse these measures of vascular ageing.

METHODS AND RESULTS

We generated ECs from iPSCs belonging to children with HGPS and their unaffected parents. Telomerase mRNA (hTERT) was used to treat HGPS ECs. Endothelial morphology and functions were assessed, as well as proteomic and transcriptional profiles with attention to inflammatory markers, DNA damage, and EC identity genes. In a mouse model of HGPS, we assessed the effects of lentiviral transfection of mTERT on measures of senescence, focusing on the EC phenotype in various organs. hTERT treatment of human HGPS ECs improved replicative capacity; restored endothelial functions such as nitric oxide generation, acetylated low-density lipoprotein uptake and angiogenesis; and reduced the elaboration of inflammatory cytokines. In addition, hTERT treatment improved cellular and nuclear morphology, in association with a normalization of the transcriptional profile, effects that may be mediated in part by a reduction in progerin expression and an increase in sirtuin 1 (SIRT1). Progeria mice treated with mTERT lentivirus manifested similar improvements, with a reduction in inflammatory and DNA damage markers and increased SIRT1 in their vasculature and other organs. Furthermore, mTERT therapy increased the lifespan of HGPS mice.

CONCLUSION

Vascular rejuvenation using telomerase mRNA is a promising approach for progeria and other age-related diseases.

Proteomic analysis of the secretome of adipose tissue-derived murine mesenchymal cells overexpressing telomerase and myocardin

RATIONALE

Understanding mechanisms of the therapeutic effects of stem/progenitor cells, among which adipose tissue-derived mesenchymal stromal cells (AT-MSCs), has important implications for clinical use. Since the majority of such cells die within days or weeks after transplantation and do not persist in the transplanted organ or tissue, their effects appear to be largely mediated by paracrine signaling pathways, and are enhanced by overexpression of the antisenescent protein telomerase reverse transcriptase (TERT), and the anti-apoptotic transcription factor myocardin (MYOCD).

AIM

By a proteomic approach combining two-dimensional gel electrophoresis (2DE) with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF/TOF) mass spectrometry, we aimed at analyzing how soluble and vesicular secretomes of aged murine AT-MSCs and their angiogenic function are modulated by the overexpression of TERT and MYOCD.

METHODS

We cultured murine mock-transduced AT-MSCs and "rejuvenated" AT-MSCs overexpressing TERT and MYOCD (rTMAT-MSCs) harvested from 1-year-old male C57BL/6 mice. We established proteomes from 3 mock-transduced AT-MSCs and rTMAT-MSCs cultures in serum-free conditions, as well as their corresponding conditioned medium (CM) and exosome-enriched fractions (Exo+).

RESULTS AND CONCLUSIONS

Proteomic analysis revealed a 2-fold increase of matrix metalloproteinase-2 (MMP-2) and its inhibitor metalloproteinase inhibitor 2 (TIMP2) in the CM - but not in the Exo + - of rTMAT-MSCs as compared to mock-transduced AT-MSCs. At the functional level, rTMAT-MSCs-CM, and - to a lesser extent - its Exo + fraction, increased tube formation of human vein endothelial cells (HUVECs), which could be blocked by anti-MMP2 and enhanced by anti-TIMP2 antibodies, respectively. Altogether, our results identify MMP2 and its inhibitor TIMP2 as novel candidates by which rTMAT-MSCs can support angiogenesis. Our strategy also illustrates the usefulness of comparative targeted proteomic approach to decipher molecular pathways underlying rTMAT-MSCs properties.

The emerging role of Notch pathway in ageing: Focus on the related mechanisms in age-related diseases

Notch signaling is an evolutionarily conserved pathway, which is fundamental for the development of all tissues, organs and systems of human body. Recently, a considerable and still growing number of studies have highlighted the contribution of Notch signaling in various pathological processes of the adult life, such as age-related diseases. In particular, the Notch pathway has emerged as major player in the maintenance of tissue specific homeostasis, through the control of proliferation, migration, phenotypes and functions of tissue cells, as well as in the cross-talk between inflammatory cells and the innate immune system, and in onset of inflammatory age-related diseases. However, until now there is a confounding evidence about the related mechanisms. Here, we discuss mechanisms through which Notch signaling acts in a very complex network of pathways, where it seems to have the crucial role of hub. Thus, we stress the possibility to use Notch pathway, the related molecules and pathways constituting this network, both as innovative (predictive, diagnostic and prognostic) biomarkers and targets for personalised treatments for age-related diseases.

Smooth muscle differentiation identifies two classes of poorly differentiated pleomorphic sarcomas with distinct outcome

The clinical relevance of accurately diagnosing pleomorphic sarcomas has been shown, especially in cases of undifferentiated pleomorphic sarcomas with myogenic differentiation, which appear significantly more aggressive. To establish a new smooth muscle differentiation classification and to test its prognostic value, 412 sarcomas with complex genetics were examined by immunohistochemistry using four smooth muscle markers (calponin, h-caldesmon, transgelin and smooth muscle actin). Two tumor categories were first defined: tumors with positivity for all four markers and tumors with no or incomplete phenotypes. Multivariate analysis demonstrated that this classification method exhibited the strongest prognostic value compared with other prognostic factors, including histological classification. Secondly, incomplete or absent smooth muscle phenotype tumor group was then divided into subgroups by summing for each tumor the labeling intensities of all four markers for each tumors. A subgroup of tumors with an incomplete but strong smooth muscle differentiation phenotype presenting an intermediate metastatic risk was thus identified. Collectively, our results show that the smooth muscle differentiation classification method may be a useful diagnostic tool as well as a relevant prognostic tool for undifferentiated pleomorphic sarcomas.

Co-activation of nuclear factor-κB and myocardin/serum response factor conveys the hypertrophy signal of high insulin levels in cardiac myoblasts

Hyperinsulinemia contributes to cardiac hypertrophy and heart failure in patients with the metabolic syndrome and type 2 diabetes. Here, high circulating levels of tumor necrosis factor (TNF)-α may synergize with insulin in signaling inflammation and cardiac hypertrophy. We tested whether high insulin affects activation of TNF-α-induced NF-κB and myocardin/serum response factor (SRF) to convey hypertrophy signaling in cardiac myoblasts. In canine cardiac myoblasts, treatment with high insulin (10(-8) to 10(-7) m) for 0-24 h increased insulin receptor substrate (IRS)-1 phosphorylation at Ser-307, decreased protein levels of chaperone-associated ubiquitin (Ub) E3 ligase C terminus of heat shock protein 70-interacting protein (CHIP), increased SRF activity, as well as β-myosin heavy chain (MHC) and myocardin expressions. Here siRNAs to myocardin or NF-κB, as well as CHIP overexpression prevented (while siRNA-mediated CHIP disruption potentiated) high insulin-induced SR element (SRE) activation and β-MHC expression. Insulin markedly potentiated TNF-α-induced NF-κB activation. Compared with insulin alone, insulin+TNF-α increased SRF/SRE binding and β-MHC expression, which was reversed by the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC) and by NF-κB silencing. In the hearts of db/db diabetic mice, in which Akt phosphorylation was decreased, p38MAPK, Akt1, and IRS-1 phosphorylation at Ser-307 were increased, together with myocardin expression as well as SRE and NF-κB activities. In response to high insulin, cardiac myoblasts increase the expression or the promyogenic transcription factors myocardin/SRF in a CHIP-dependent manner. Insulin potentiates TNF-α in inducing NF-κB and SRF/SRE activities. In hyperinsulinemic states, myocardin may act as a nuclear effector of insulin, promoting cardiac hypertrophy.

Simvastatin-enhanced expression of promyogenic nuclear factors and cardiomyogenesis of murine embryonic stem cells

A combination of statin and stem cell therapies has been shown to benefit in experimental models of myocardial infarction. This study tests whether treatment with simvastatin has a direct impact on the cardiomyogenic development of murine embryonic stem cells (ESCs) in embryoid bodies. In a concentration-dependent manner, simvastatin treatment enhanced expression of several promyogenic nuclear transcription factors, including GATA4, Nkx2.5, DTEF-1 and myocardin A. The statin-treated cells also displayed higher levels of cardiac proteins, including myosin, α-actinin, Ryanodine receptor-2, and atrial natriuretic peptide, and they developed synchronized contraction. The statin's promyogenic effect was partially diminished by the addition of the two isoprenoids FPP and GGPP, which are intermediates of cholesterol synthesis. Thus, simvastatin treatment enhances ESC myogenesis during early development perhaps via a mechanism inhibiting the mevalonate-FPP/GGPP pathway.