Local renin angiotensin expression regulates human mesenchymal stem cell differentiation to adipocytes

Clinical and experimental evidence suggest that the renin-angiotensin system (RAS) plays a role in metabolic syndrome. Adipogenesis is suggested to modulate obesity and obesity-related consequences, such as metabolic syndrome. Although mesenchymal stem cells (MSCs) are a major source of adipocyte generation, the influence of RAS on MSC differentiation to adipocyte is unknown. We evaluated the expression of endogenous RAS in human MSCs during its differentiation to adipocytes and studied the effects of angiotensin II (Ang II), Ang II type 1 receptor blocker Valsartan, and type 2 (AT(2)) receptor blocker PD123319. Our data showed that differentiation was associated with an increase in cellular renin and AT(2) receptor expression and a concomitant decrease in angiotensinogen and angiotensin-converting enzyme expression. The net effect is an increase in endogenous cellular angiotensin II production. Incubation with Ang II (exogenous) inhibited adipogenesis. Combined treatment of exogenous Ang II and Valsartan further inhibited adipogenesis, whereas combined treatment of Ang II and PD123319 completely abolished the inhibition of adipogenesis, suggesting an important role for the AT(2) receptor. Blockade of endogenous angiotensin II effect by incubation with Valsartan alone inhibited adipogenesis, whereas PD123319 alone promoted adipogenesis, confirming the data using exogenous Ang II. The combination of Valsartan and PD123319 had no net effect. Our data demonstrate an important role of the expression of the local RAS in the regulation of human MSC differentiation to adipocytes. Elucidation of the molecular mechanism should provide important insight into the pathophysiology of the metabolic syndrome and the development of future therapeutics.     

A novel role for the cyclin-dependent kinase inhibitor p27Kip1 in angiotensin II–stimulated vascular smooth muscle cell hypertrophy

Angiotensin II (Ang II) has been shown to stimulate either hypertrophy or hyperplasia. We postulated that the differential response of vascular smooth muscle cells (VSMCs) to Ang II is mediated by the cyclin-dependent kinase (Cdk) inhibitor p27(Kip1), which is abundant in quiescent cells and drops after serum stimulation. Ang II treatment (100 nM) of quiescent VSMCs led to upregulation of the cell-cycle regulatory proteins cyclin D1, Cdk2, proliferating cell nuclear antigen, and Cdk1. p27(Kip1) levels, however, remained high, and the activation of the G1-phase Cdk2 was inhibited as the cells underwent hypertrophy. Overexpression of p27(Kip1) cDNA inhibited serum-stimulated [(3)H]thymidine incorporation compared with control-transfected cells. This cell-cycle inhibition was associated with cellular hypertrophy, as reflected by an increase in the [(3)H]leucine/[(3)H]thymidine incorporation ratio and by an increase in forward-angle light scatter during flow cytometry at 48 hours after transfection. The role of p27(Kip1) in modulating the hypertrophic response of VSMCs to Ang II was further tested by antisense oligodeoxynucleotide (ODN) inhibition of p27(Kip1) expression. Ang II stimulated an increase in [(3)H]thymidine incorporation and the percentage of S-phase cells in antisense ODN-transfected cells but not in control ODN-transfected cells. We conclude that p27(Kip1) plays a role in mediating VSMC hypertrophy. Ang II stimulation of quiescent cells in which p27(Kip1) levels are high results in hypertrophy but promotes hyperplasia when levels of p27(Kip1) are low, as in the presence of other growth factors.     

Antisense oligodeoxynucleotides prevent acute cardiac allograft rejection via a novel, nontoxic, highly efficient transfection method.

BACKGROUND: We hypothesized that ex vivo donor allograft transfection with antisense oligodeoxynucleotide (AS ODN) would inhibit the expression of intercellular adhesion molecule (ICAM)-1, an important mediator of T-cell adhesion and costimulation, and therefore suppress acute cardiac rejection. METHODS: Hearts were transfected ex vivo with AS, reverse AS ODN, or saline by applying 3 atm pressure for 45 min at 4 degrees C. Grafts were then transplanted into allogenic recipients +/- treatment with leukocyte function-associated antigen (LFA)-1 monoclonal antibody (mAb) (1.5 mg/kg intravenously), cyclosporine (2.5 mg/ kg/day p.o.), or rapamycin (0.025 mg/kg/day intraperitoneally). Reperfusion injury was assessed in grafts harvested at early time points using the myeloperoxidase, %wet weight, and %contraction band necrosis assays; transfection efficiency was assessed using fluorescent microscopy; and efficacy of ICAM-1 blockade was assessed using immunohistochemistry. Other grafts were followed until rejection with donor/third-party skin grafting, adoptive transfer, and interleukin 2 infusion studies in selected recipients. RESULTS: Transfection was highly efficient (fluorescein isothiocyanate-ODN in 48+/-5% of total myocardial nuclei), nontoxic, and reduced the ICAM-1-positive area to 53+/-14% versus having no effect on MHC class I expression (n=4). The incidence of survival >60 days after AS ODN + LFA-1 monoclonal antibody was 75%, significantly higher than other regimens. CONCLUSION: AS ODN hyperbaric transfection proved highly efficient, effective at ICAM-1 blockade, and induced cardiac allograft tolerance when combined with LFA-1 monoclonal antibody. This highly targeted alteration of allograft immunogenicity may have an important role in future immunosuppressive strategies.     

Short-Ti inversion-recovery pulse sequence: analysis and initial experience in cancer imaging

Inversion recovery (IR), commonly considered a pulse sequence capable of producing T1-weighted images with excellent display of normal anatomy, is versatile: The null point and peak time provide a useful, succinct summary of the properties of IR and its capacity for producing both T1- and T2-weighted images. Shortening of the inversion time (TI) and creation of a short-TI inversion-recovery (STIR) pulse sequence increases sensitivity to malignancy and other abnormalities by making the effects of prolonged T1 and T2 on signal intensity additive and by nulling the signal from fat. The authors examined over 300 patients with various malignancies and compared STIR images with T1- and T2-weighted images obtained at 0.5 T. In 43 cases, signal-difference-to-noise ratios (SD/Ns) were calculated between tumor, fat, and muscle. In general, STIR images demonstrated tumor as a conspicuously high-intensity area in a background of muted, discernible anatomic detail. The good contrast achieved with STIR sequences between tumor and fat (SD/N = 18.1) and tumor and muscle (SD/N = 12.9) consolidated into a single image the information contained separately on T1- and T2-weighted images, which facilitates efficient detection and localization of malignancy.     

Toremifene in the treatment of breast cancer

Although more widespread screening and routine adjuvant therapy has improved the outcome for breast cancer patients in recent years, there remains considerable scope for improving the efficacy, safety and tolerability of adjuvant therapy in the early stage disease and the treatment of advanced disease. Toremifene is a selective estrogen receptor modifier (SERM) that has been widely used for decades in hormone receptor positive breast cancer both in early and late stage disease. Its efficacy has been well established in nine prospective randomized phase III trials compared to tamoxifen involving more than 5500 patients, as well as in several large uncontrolled and non-randomized studies. Although most studies show therapeutic equivalence between the two SERMs, some show an advantage for toremifene. Several meta-analyses have also confirmed that the efficacy of toremifene is at least as good as that of tamoxifen. In terms of safety and tolerability toremifene is broadly similar to tamoxifen although there is some evidence that toremifene is less likely to cause uterine neoplasms, serious vascular events and it has a more positive effect on serum lipids than does tamoxifen. Toremifene is therefore effective and safe in the treatment of breast cancer. It provides not only a useful therapeutic alternative to tamoxifen, but may bring specific benefits.     

Paracrine mechanisms of stem cell reparative and regenerative actions in the heart

Stem cells play an important role in restoring cardiac function in the damaged heart. In order to mediate repair, stem cells need to replace injured tissue by differentiating into specialized cardiac cell lineages and/or manipulating the cell and molecular mechanisms governing repair. Despite early reports describing engraftment and successful regeneration of cardiac tissue in animal models of heart failure, these events appear to be infrequent and yield too few new cardiomyocytes to account for the degree of improved cardiac function observed. Instead, mounting evidence suggests that stem cell mediated repair takes place via the release of paracrine factors into the surrounding tissue that subsequently direct a number of restorative processes including myocardial protection, neovascularization, cardiac remodeling, and differentiation. The potential for diverse stem cell populations to moderate many of the same processes as well as key paracrine factors and molecular pathways involved in stem cell‐mediated cardiac repair will be discussed in this review. This article is part of a special issue entitled, "Cardiovascular Stem Cells Revisited".