Bmi1 Is a Key Epigenetic Barrier to Direct Cardiac Reprogramming

Direct reprogramming of induced cardiomyocytes (iCMs) suffers from low efficiency and requires extensive epigenetic repatterning, although the underlying mechanisms are largely unknown. To address these issues, we screened for epigenetic regulators of iCM reprogramming and found that reducing levels of the polycomb complex gene Bmi1 significantly enhanced induction of beating iCMs from neonatal and adult mouse fibroblasts. The inhibitory role of Bmi1 in iCM reprogramming is mediated through direct interactions with regulatory regions of cardiogenic genes, rather than regulation of cell proliferation. Reduced Bmi1 expression corresponded with increased levels of the active histone mark H3K4me3 and reduced levels of repressive H2AK119ub at cardiogenic loci, and de-repression of cardiogenic gene expression during iCM conversion. Furthermore, Bmi1 deletion could substitute for Gata4 during iCM reprogramming. Thus, Bmi1 acts as a critical epigenetic barrier to iCM production. Bypassing this barrier simplifies iCM generation and increases yield, potentially streamlining iCM production for therapeutic purposes

The survival condition and immunoregulatory function of adipose stromal vascular fraction (SVF) in the early stage of nonvascularized adipose transplantation.

INTRODUCTION: Adipose tissue transplantation is one of the standard procedures for soft-tissue augmentation, reconstruction, and rejuvenation. However, it is unknown as to how the graft survives after transplantation. We thus seek out to investigate the roles of different cellular components in the survival of graft. MATERIALS & METHODS: The ratios of stromal vascular fraction (SVF) cellular components from human adipose tissue were evaluated using flow cytometry. Human liposuction aspirates that were either mixed with marked SVF cells or PBS were transplanted into nude mice. The graft was harvested and stained on days 1,4,7 and 14. The inflammation level of both SVF group and Fat-only group were also evaluated. RESULTS: Flow cytometric analysis showed SVF cells mainly contained blood-derived cells, adipose-derived stromal cells (ASCs), and endothelial cells. Our study revealed that most cells are susceptible to death after transplantation, although CD34+ ASCs can remain viable for 14 days. Notably, we found that ASCs migrated to the peripheral edge of the graft. Moreover, the RT-PCR and the immuno-fluorescence examination revealed that although the SVF did not reduce the number of infiltrating immune cells (macrophages) in the transplant, it does have an immunoregulatory function of up-regulating the expression of CD163 and CD206 and down-regulating that of IL-1β, IL-6. CONCLUSIONS: Our study suggests that the survival of adipose tissue after nonvascularized adipose transplantation may be due to the ASCs in SVF cells. Additionally, the immunoregulatory function of SVF cells may be indirectly contributing to the remolding of adipose transplant, which may lead to SVF-enriched adipose transplantation

An unfitted hybridizable discontinuous Galerkin method for the Poisson interface problem and its error analysis

In this article, we present and analyse an unfitted mesh method for the Poisson interface problem. By constructing a novel ansatz function in the vicinity of the interface, we are able to derive an extended Poisson problem whose interface fits a given quasi-uniform triangular mesh. Then we adopt a hybridizable discontinuous Galerkin method to solve the extended problem with an appropriate choice of flux for treating the jump conditions. In contrast with existing approaches, the ansatz function is designed through a delicate piecewise quadratic Hermite polynomial interpolation with a post-processing via a standard Lagrange polynomial interpolation. Such an explicit function offers a third-order approximation to the singular part of the underlying solution for interfaces of any shape. It is also essential for both stability and convergence of the proposed method. Moreover, we provide rigorous error analysis to show that the scheme can achieve a second-order convergence rate for the approximation of the solution and its gradient. Ample numerical examples with complex interfaces demonstrate the expected convergence order and robustness of the method.MOE (Min. of Education, S’pore

Numerical investigation of the purge flow mechanisms and heat-transfer characteristics of turbine rim seals

In gas turbine and aeroengine, the rim seal is set between the turbine stator and rotor to prevent ingestion of the high-temperature mainstream into the rotating cavity. This study examined the sealing efficiency, flow mechanisms, and heat-transfer characteristics of three types of radial rim seal structures, which seriously affect the turbine aerodynamic efficiency and thermal safety. The flows and thermal fields were simulated using steady and unsteady numerical simulations, and dynamic modal decomposition was carried out to extract the unsteady characteristics. The results show that the seal cavity shape affects the seal efficiency. It was found that dolphin-nose with a hook and large cavity results in a higher sealing efficiency. The nose configuration of the cavity upper part also affects the outflow form of the purge flow. The purge flow from a shark-nose seal will inhibit the strength of the mainstream passage vortex, while that from a dolphin-nose seal will result in Kelvin-Helmholtz instability under certain flow rates and induce unsteady vortices. The purge flow will increase the thermal load of the blade and the hub at low flow rates. In particular, the overall thermal load with a dolphin-nose seal is 50% higher than that with a shark-nose structure. It is necessary to balance the sealing efficiency, flow instability characteristics, and heat-transfer characteristics to select an appropriate rim seal configuration

Anti-Aging Effect of Adipose-Derived Stem Cells in a Mouse Model of Skin Aging Induced by D-Galactose

<div><p>Introduction</p><p>Glycation products accumulate during aging of slowly renewing tissue, including skin, and are suggested as an important mechanism underlying the skin aging process. Adipose-derived cells are widely used in the clinic to treat ischemic diseases and enhance wound healing. Interestingly, adipose-derived stem cells (ASCs) are also effective in anti-aging therapy, although the mechanism underlying their effects remains unknown. The purpose of the present study was to examine the anti-aging effect of ASCs in a D-galactose-induced aging animal model and to clarify the underlying mechanism.</p><p>Materials and Methods</p><p>Six-week-old nude mice were subcutaneously injected with D-gal daily for 8 weeks. Two weeks after completion of treatment, mice were randomized to receive subcutaneous injections of 10⁶ green fluorescent protein (GFP)-expressing ASCs, aminoguanidine (AG) or phosphate-buffered saline (PBS). Control mice received no treatment. We examined tissue histology and determined the activity of senescence-associated molecular markers such as superoxide dismutase (SOD) and malondialdehyde (MDA).</p><p>Results</p><p>Transplanted ASCs were detectable for 14 days and their GFP signal disappeared at day 28 after injection. ASCs inhibited advanced glycation end product (AGE) levels in our animal model as well as increased the SOD level and decreased the MDA level, all of which act to reverse the aging phenotype in a similar way to AG, an inhibitor of AGE formation. Furthermore, ASCs released angiogenic factors <i>in vivo</i> such as vascular endothelial growth factor, suggesting a skin trophic effect.</p><p>Conclusions</p><p>These results demonstrate that ASCs may contribute to the regeneration of skin during aging. In addition, the data shows that ASCs provide a functional benefit by glycation suppression, antioxidation, and trophic effects in a mouse model of aging.</p></div

A Review of Sensitivity Enhancement in Interferometer-Based Fiber Sensors

Optical fiber sensors based on an interferometer structure play a significant role in monitoring physical, chemical, and biological parameters in natural environments. However, sensors with high-sensitivity measurement still present their own challenges. This paper deduces and summarizes the methods of sensitivity enhancement in interferometer based fiber optical sensors, including the derivation of the sensing principles, key characteristics, and recently-reported applications.The modal coupling interferometer is taken as an example to derive the five terms related to the sensitivity: (1) the wavelength-dependent difference of phase between two modes/arms ∂ϕd/∂λ, (2) the sensor length Lw,A, (3) refractive index difference between two modes/arms Δneff,A, (4) sensing parameter dependent length change α, and (5) sensing parameter dependent refractive index change γ. The research papers in the literature that modulate these terms to enhance the sensing sensitivity are reviewed in the paper

The changes in angiogenesis in skin tissue.

<p><b>A</b>. Immunohistochemical detection of CD31-positive microvessels (arrows) and vascular endothelial growth factor (VEGF) expression in skin tissue in control, D-gal-treated, D-gal plus adipose-derived stem cells (ASCs)-treated, and D-gal plus aminoguanidine (AG)-treated animals. CD31: Scale bar  = 200 µm, VEGF: Scale bar  = 100 µm. <b>B</b>. The changes in vascular density/mm² in control, D-gal-treated, D-gal plus ASCs-treated, and D-gal plus AG-treated groups determined by counting the number of CD31-positive vessels within visual fields (n = 8). *P<0.05. <b>C</b>. The D-gal plus ASCs-treated showed the highest expression of VEGF among the four groups.</p

In vivo dedifferentiation of adult adipose cells.

Adipocytes can dedifferentiate into fibroblast-like cells in vitro and thereby acquire proliferation and multipotent capacities to participate in the repair of various organs and tissues. Whether dedifferentiation occurs under physiological or pathological conditions in vivo is unknown.A tissue expander was placed under the inguinal fat pads of rats and gradually expanded by injection of water. Samples were collected at various time points, and morphological, histological, cytological, ultrastructural, and gene expression analyses were conducted. In a separate experiment, purified green fluorescent protein+ adipocytes were transplanted into C57 mice and collected at various time points. The transplanted adipocytes were assessed by bioluminescence imaging and whole-mount staining.The expanded fat pad was obviously thinner than the untreated fat pad on the opposite side. It was also tougher in texture and with more blood vessels attached. Hematoxylin and eosin staining and transmission electron microscopy indicated there were fewer monolocular adipocytes in the expanded fat pad and the morphology of these cells was altered, most notably their lipid content was discarded. Immunohistochemistry showed that the expanded fat pad contained an increased number of proliferative cells, which may have been derived from adipocytes. Following removal of the tissue expander, many small adipocytes were observed. Bioluminescence imaging suggested that some adipocytes survived when transplanted into an ischemic-hypoxic environment. Whole-mount staining revealed that surviving adipocytes underwent a process similar to adipocyte dedifferentiation in vitro. Monolocular adipocytes became multilocular adipocytes and then fibroblast-like cells.Mature adipocytes may be able to dedifferentiate in vivo, and this may be an adipose tissue self-repair mechanism. The capacity of adipocytes to dedifferentiate into stem cell-like cells may also have a more general role in the regeneration of many tissues, notably in fat grafting

Immunohistology of ECs in the graft.

<p>A: Lectin and Hoechst double positive cells were regarded as marked ECs (white arrowheads), otherwise (Lectin-positive only) as which were from the graft (yellow arrowheads), and Hoechst-positive only cells were identified as marked non-endothelial cells (red arrowheads). Scale bars = 50μm. B: A few marked ECs (white arrowheads), un-marked ECs (yellow arrowheads) (left) and those non-endothelial SVF cells (red arrowheads) could form cell cords (middle) on day 4. Scale bars = 20μm. Moreover, ECs from marked SVF cells formed blood vessel structure (right). Scale bars = 10μm. C: Quantification of surviving (Hoechst/Lectin-double positive) marked ECs (n = 7). The retention ratios for ECs fell off sharply from day 1 to day 4, which decreased further at day 14 (*p< 0.05).</p