miR-34a Promotes Vascular Smooth Muscle Cell Calcification by Downregulating SIRT1 (Sirtuin 1) and Axl (AXL Receptor Tyrosine Kinase).

Objective- Vascular calcification (VC) is age dependent and a risk factor for cardiovascular and all-cause mortality. VC involves the senescence-induced transdifferentiation of vascular smooth muscle cells (SMCs) toward an osteochondrogenic lineage resulting in arterial wall mineralization. miR-34a increases with age in aortas and induces vascular SMC senescence through the modulation of its target SIRT1 (sirtuin 1). In this study, we aimed to investigate whether miR-34a regulates VC. Approach and Results- We found that miR-34a and Runx2 (Runt-related transcription factor 2) expression correlates in young and old mice. Mir34a+/+ and Mir34a-/- mice were treated with vitamin D, and calcium quantification revealed that Mir34a deficiency reduces soft tissue and aorta medial calcification and the upregulation of the VC Sox9 (SRY [sex-determining region Y]-box 9) and Runx2 and the senescence p16 and p21 markers. In this model, miR-34a upregulation was transient and preceded aorta mineralization. Mir34a-/- SMCs were less prone to undergo senescence and under osteogenic conditions deposited less calcium compared with Mir34a+/+ cells. Furthermore, unlike in Mir34a+/+ SMC, the known VC inhibitors SIRT1 and Axl (AXL receptor tyrosine kinase) were only partially downregulated in calcifying Mir34a-/- SMC. Strikingly, constitutive miR-34a overexpression to senescence-like levels in human aortic SMCs increased calcium deposition and enhanced Axl and SIRT1 decrease during calcification. Notably, we also showed that miR-34a directly decreased Axl expression in human aortic SMC, and restoration of its levels partially rescued miR-34a-dependent growth arrest. Conclusions- miR-34a promotes VC via vascular SMC mineralization by inhibiting cell proliferation and inducing senescence through direct Axl and SIRT1 downregulation, respectively. This miRNA could be a good therapeutic target for the treatment of VC.

Heart valve engineering: decellularized aortic homograft seeded with human cardiac stromal cells.

BACKGROUND AND AIM OF THE STUDY: The adult human heart contains a cardiac mesenchymal stromal cell (CStC) population with residual cardiovascular plasticity. The study aim was to investigate the ability of CStCs to populate decellularized aortic homograft leaflets, without mechanical stimulation. METHODS: The ability of CStCs to acquire valve endothelial and interstitial cell phenotypes was tested using in vitro assays. First, trypsin-decellularized aortic leaflets were seeded with CStCs under static conditions; tissue section analyses were then performed before and after decellularization, and at 10, 20, and 30 days after reseeding. RESULTS: Following in vitro treatment, the CStCs differentiated along the endothelial lineage, as shown by their capacity to uptake acetylated low-density lipoprotein and to secrete the pro-angiogenic factor, vascular endothelial growth factor. After seeding, CStCs were able to adhere to the leaflet surface, rescuing up to the 90% of the original cell density and expressing the mature endothelial marker, von Willebrandt factor. The CStC supernatants were also positive for matrix metalloprotease-2 (MMP-2), which confirmed the ability of these cells to penetrate within the leaflet structure; this also suggested that CStCs, once engrafted, would contribute to the extracellular matrix turnover. Accordingly, although at a lower efficiency, CStC repopulation was also evident in the inner portions of the leaflet. CONCLUSION: Seeded CStCs were able to reconstitute, without mechanical stimulation, an endothelial-like layer and to partially infiltrate decellularized homograft leaflets. Hence, CStCs appear to be a potentially useful cell type for engineered heart valves.

GMP-based CD133(+) cells isolation maintains progenitor angiogenic properties and enhances standardization in cardiovascular cell therapy.

The aim of the present study was to develop and validate a good manufacturing practice (GMP) compliant procedure for the preparation of bone marrow (BM) derived CD133(+) cells for cardiovascular repair. Starting from available laboratory protocols to purify CD133(+) cells from human cord blood, we implemented these procedures in a GMP facility and applied quality control conditions defining purity, microbiological safety and vitality of CD133(+) cells. Validation of CD133(+) cells isolation and release process were performed according to a two-step experimental program comprising release quality checking (step 1) as well as 'proofs of principle' of their phenotypic integrity and biological function (step 2). This testing program was accomplished using in vitro culture assays and in vivo testing in an immunosuppressed mouse model of hindlimb ischemia. These criteria and procedures were successfully applied to GMP production of CD133(+) cells from the BM for an ongoing clinical trial of autologous stem cells administration into patients with ischemic cardiomyopathy. Our results show that GMP implementation of currently available protocols for CD133(+) cells selection is feasible and reproducible, and enables the production of cells having a full biological potential according to the most recent quality requirements by European Regulatory Agencies.

MicroRNA-34a Induces Vascular Smooth Muscle Cells Senescence by SIRT1 Downregulation and Promotes the Expression of Age-Associated Pro-inflammatory Secretory Factors.

Arterial aging is a major risk factor for the occurrence of cardiovascular diseases. The aged artery is characterized by endothelial dysfunction and vascular smooth muscle cells altered physiology together with low-grade chronic inflammation. MicroRNA-34a (miR-34a) has been recently implicated in cardiac, endothelial, and endothelial progenitor cell senescence; however, its contribution to aging-associated vascular smooth muscle cells phenotype has not been explored so far. We found that miR-34a was highly expressed in aortas isolated from old mice. Moreover, its well-known target, the longevity-associated protein SIRT1, was significantly downregulated during aging in both endothelial cells and vascular smooth muscle cells. Increased miR-34a as well as decreased SIRT1 expression was also observed in replicative-senescent human aortic smooth muscle cells. miR-34a overexpression in proliferative human aortic smooth muscle cells caused cell cycle arrest along with enhanced p21 protein levels and evidence of cell senescence. Furthermore, miR-34a ectopic expression induced pro-inflammatory senescence-associated secretory phenotype molecules. Finally, SIRT1 protein significantly decreased upon miR-34a overexpression and restoration of its levels rescued miR-34a-dependent human aortic smooth muscle cells senescence, but not senescence-associated secretory phenotype factors upregulation. Taken together, our findings suggest that aging-associated increase of miR-34a expression levels, by promoting vascular smooth muscle cells senescence and inflammation through SIRT1 downregulation and senescence-associated secretory phenotype factors induction, respectively, may lead to arterial dysfunctions.

Endothelial and cardiac progenitors: boosting, conditioning and (re)programming for cardiovascular repair.

Preclinical studies performed in cell culture and animal systems have shown the outstanding ability of stem cells to repair ischemic heart and lower limbs by promoting the formation of new blood vessels and new myocytes. In contrast, clinical studies of stem cell administration in patients with myocardial ischemia have revealed only modest, although promising, results. Basic investigations have shown the feasibility of adult cells reprogramming into pluripotent cells by defined factors, thus opening the way to the devise of protocols to ex vivo derive virtually unexhausted cellular pools. In contrast, cellular and molecular studies have indicated that risk factors limit adult-derived stem cell survival, proliferation and engraftment in ischemic tissues. The use of fully reprogrammed cells raises safety concerns; therefore, adult cells remain a primary option for clinicians interested in therapeutic cardiovascular repair. Pharmacologic approaches have been devised to restore the cardiovascular repair ability of failing progenitors from patients at risk. In the present contribution, the most advanced pharmacologic approaches to (re)program, boost, and condition endothelial and cardiac progenitor cells to enhance cardiovascular regeneration are discussed.

Histone deacetylase inhibition enhances self renewal and cardioprotection by human cord blood-derived CD34 cells.

BACKGROUND: Use of peripheral blood- or bone marrow-derived progenitors for ischemic heart repair is a feasible option to induce neo-vascularization in ischemic tissues. These cells, named Endothelial Progenitors Cells (EPCs), have been extensively characterized phenotypically and functionally. The clinical efficacy of cardiac repair by EPCs cells remains, however, limited, due to cell autonomous defects as a consequence of risk factors. The devise of "enhancement" strategies has been therefore sought to improve repair ability of these cells and increase the clinical benefit. PRINCIPAL FINDINGS: Pharmacologic inhibition of histone deacetylases (HDACs) is known to enhance hematopoietic stem cells engraftment by improvement of self renewal and inhibition of differentiation in the presence of mitogenic stimuli in vitro. In the present study cord blood-derived CD34(+) were pre-conditioned with the HDAC inhibitor Valproic Acid. This treatment affected stem cell growth and gene expression, and improved ischemic myocardium protection in an immunodeficient mouse model of myocardial infarction. CONCLUSIONS: Our results show that HDAC blockade leads to phenotype changes in CD34(+) cells with enhanced self renewal and cardioprotection.

When cells become a drug. Endothelial progenitor cells for cardiovascular therapy: aims and reality.

The recently disclosed plasticity properties of adult-derived stem cells, their ability to be reprogrammed by defined factors into pluripotent stem cells and the comprehension of "epi"-genetic mechanisms underlying stem cells differentiation process has opened unexpected avenues to attempt regeneration of tissues affected by degenerative disorders and prompted the birth of the new "regenerative medicine" concept. Regeneration of the vascular and myocardial tissues is considered a primary endpoint to limit the consequences of acute and chronic ischemic heart disorders. Cellular therapy of the ischemic heart has been attempted in more than 1000 patients worldwide and the results of the first meta-analysis studies have been recently made available. In several cases, the results did not fulfill the expectations. In fact, they unpredictably indicated modest, yet significant, clinical benefits in patients compared to the outstanding results using stem cells in animal models of ischemic heart and peripheral disease. Several interpretations have been raised to explain these discrepancies. These include lifestyle and risk factor-associated modifications of the stem cell biological activity, but also procedural problems in the translation of cells from bench to bedside. The present review will cover light and shaded areas in the cardiovascular cellular therapy field, and will discuss about recent advances and related patents designed to enhance efficiency of stem cell therapy in patients with cardiovascular disease. These advancements will be discussed in the light of the most advanced issues that have been introduced worldwide by Regulatory Agencies.

Granulocyte colony-stimulating factor attenuates left ventricular remodelling after acute anterior STEMI: results of the single-blind, randomized, placebo-controlled multicentre STem cEll Mobilization in Acute Myocardial Infarction (STEM-AMI) Trial.

AIMS: The aim of this study was to assess the effect of granulocyte colony-stimulating factor (G-CSF) on left ventricular (LV) function and volumes in patients with anterior ST-elevation myocardial infarction (STEMI) and depressed LV ejection fraction (EF). METHODS AND RESULTS: Sixty consecutive patients with anterior STEMI, undergoing primary angioplasty percutaneous coronary intervention (PCI), with symptom-to-reperfusion time of 2-12 h and EF ≤45% after PCI, were randomized to G-CSF 5 µg/kg b.i.d. subcutaneously (n = 24) or placebo (n = 25) for 5 days, starting <12 h after PCI. The primary endpoint was an increase from baseline to 6 months of 5% in left ventricular ejection fraction (LVEF), as measured by magnetic resonance imaging (MRI). Co-primary endpoint was a ≥20 mL difference in end-diastolic volume (EDV). Infarct size and perfusion were evaluated with late gadolinium enhancement (LGE) and gated (99m)Technetium Sestamibi single-photon emission computed tomography (SPECT). Left ventricular EDV and end-systolic volume (ESV) increased from baseline to 6 months in the placebo group (81.7 ± 24.4 to 94.4 ± 26.0 mL/m(2), P < 0.00005 and 45.2 ± 20.0 to 53.2 ± 23.8 mL/m(2), P = 0.016) but were unchanged in the G-CSF group (82.2 ± 20.3 to 85.7 ± 23.7 mL/m(2), P = 0.40 and 46.0 ± 18.2 to 48.4 ± 20.8 mL/m(2), P = 0.338). There were no significant differences in EF or perfusion between groups. A significant reduction in transmural LGE segments was seen at 6 months in the G-CSF vs. placebo groups (4.38 ± 2.9 to 3.3 ± 2.6, P = 0.04 and 4.2 ± 2.6 to 3.6 ± 2.7, P = 0.301, respectively). Significantly more placebo patients had a change in left ventricular end-diastolic volume abovethe median (9.3 mL/m(2)) when reperfusion time exceeded 180 min (median time-to-reperfusion) (P = 0.0123). Severe adverse events were similar between groups. CONCLUSION: Early G-CSF administration attenuates ventricular remodelling in patients with anterior STEMI and EF ≤45% after successful PCI.