The regenerative potential of skeletal muscle declines with age, and this impairment is associated with an increase in tissue fibrosis. We show that muscle stem cells (satellite cells) from aged mice tend to convert from a myogenic to a fibrogenic lineage as they begin to proliferate and that this conversion is mediated by factors in the systemic environment of the old animals. We also show that this lineage conversion is associated with an activation of the canonical Wnt signaling pathway in aged myogenic progenitors and can be suppressed by Wnt inhibitors. Furthermore, components of serum from aged mice that bind to the Frizzled family of proteins, which are Wnt receptors, may account for the elevated Wnt signaling in aged cells. These results indicate that the Wnt signaling pathway may play a critical role in tissue-specific stem cell aging and an increase in tissue fibrosis with age.

Poly(ADP-ribose) polymerase-1 (PARP-1) has a modular domain architecture that couples DNA damage detection to poly(ADP-ribosyl)ation activity through a poorly understood mechanism. Here we report the crystal structure of a DNA double-strand break in complex with human PARP-1 domains essential for activation (Zn1, Zn3, WGR-CAT). PARP-1 engages DNA as a monomer, and the interaction with DNA damage organizes PARP-1 domains into a collapsed conformation that can explain the strong preference for automodification. The Zn1, Zn3, and WGR domains collectively bind to DNA, forming a network of interdomain contacts that links the DNA damage interface to the catalytic domain (CAT). The DNA damage-induced conformation of PARP-1 results in structural distortions that destabilize the CAT. Our results suggest that an increase in CAT protein dynamics underlies the DNA-dependent activation mechanism of PARP-1.

The ER-mitochondrial junction provides a local calcium signaling domain that is critical for both matching energy production with demand and the control of apoptosis. Here, we visualize ER-mitochondrial contact sites and monitor the localized [Ca2+] changes ([Ca2+]ER-mt) using drug-inducible fluorescent interorganelle linkers. We show that all mitochondria have contacts with the ER but plasma membrane-mitochondrial contacts are less frequent because of interleaving ER stacks in both RBL-2H3 and H9c2 cells. Single mitochondria display discrete patches of ER contacts and show heterogeneity in the ER-mitochondrial Ca2+ transfer. Pericam-tagged linkers revealed IP3-induced [Ca2+]ER-mt signals that exceeded 9μM and endured buffering bulk cytoplasmic [Ca2+] increases. Altering linker length to modify the space available for the Ca2+ transfer machinery had a biphasic effect on [Ca2+]ER-mt signals. These studies provide direct evidence for the existence of high Ca2+ microdomains between the ER and mitochondria, and suggest an optimal gap width for efficient Ca2+ transfer.

Poly(ADP-ribose) polymerase-1 (PARP-1) has two homologous zinc finger domains, Zn1 and Zn2, that bind to a variety of DNA structures to stimulate poly(ADP-ribose) synthesis activity and to mediate PARP-1 interaction with chromatin. The structural basis for interaction with DNA is unknown, which limits our understanding of PARP-1 regulation and involvement in DNA repair and transcription. Here, we have determined crystal structures for the individual Zn1 and Zn2 domains in complex with a DNA double strand break, providing the first views of PARP-1 zinc fingers bound to DNA. The Zn1-DNA and Zn2-DNA structures establish a novel, bipartite mode of sequence-independent DNA interaction that engages a continuous region of the phosphodiester backbone and the hydrophobic faces of exposed nucleotide bases. Biochemical and cell biological analysis indicate that the Zn1 and Zn2 domains perform distinct functions. The Zn2 domain exhibits high binding affinity to DNA compared with the Zn1 domain. However, the Zn1 domain is essential for DNA-dependent PARP-1 activity in vitro and in vivo, whereas the Zn2 domain is not strictly required. Structural differences between the Zn1-DNA and Zn2-DNA complexes, combined with mutational and structural analysis, indicate that a specialized region of the Zn1 domain is re-configured through the hydrophobic interaction with exposed nucleotide bases to initiate PARP-1 activation.

Over the last few decades, computer-aided drug design has emerged as a powerful technique playing a crucial role in the development of new drug molecules. Structure-based drug design and ligand-based drug design are two methods commonly used in computer-aided drug design. In this article, we discuss the theory behind both methods, as well as their successful applications and limitations. To accomplish this, we reviewed structure based and ligand based virtual screening processes. Molecular dynamics simulation, which has become one of the most influential tool for prediction of the conformation of small molecules and changes in their conformation within the biological target, has also been taken into account. Finally, we discuss the principles and concepts of molecular docking, pharmacophores and other methods used in computer-aided drug design.

The poly(ADP-ribose) polymerase enzyme Tankyrase-1 (TNKS) regulates multiple cellular processes and interacts with diverse proteins using five ankyrin repeat clusters (ARCs). There are limited structural insights into functional roles of the multiple ARCs of TNKS. Here we present the ARC1-3 crystal structure and employ small-angle X-ray scattering (SAXS) to investigate solution conformations of the complete ankyrin repeat domain. Mutagenesis and binding studies using the bivalent TNKS binding domain of Axin1 demonstrate that only certain ARC combinations function together. The physical basis for these restrictions is explained by both rigid and flexible ankyrin repeat elements determined in our structural analysis. SAXS analysis is consistent with a dynamic ensemble of TNKS ankyrin repeat conformations modulated by Axin1 interaction. TNKS ankyrin repeat domain is thus an adaptable binding platform with structural features that can explain selectivity toward diverse proteins, and has implications for TNKS positioning of bound targets for poly(ADP-ribose) modification.

We put forth our opinion regarding the enhanced plasticity and modulation of mechanical properties of polymeric films obtained through electrospinning process in this article. In majority of the pharmaceutical, biomedical, and packaging applications, it is desirable that polymer based matrices should be soft, flexible, and have a moderate toughness. In order to convert inflexible and brittle polymers, adjuvants in the form of plasticizers are added to improve the flexibility and smoothness of solvent casted polymer films. However, many of these plasticizers are under scrutiny for their toxic effects and environmental hazards. In addition, plasticizers also increase the cost of end products. This has motivated the scientific community to investigate alternate approaches. The changes imparted in membrane casted by electrospinning were tried to be proved by SEM, Mechanical property study, DSC and XRD studies. We have showed dramatic improvement in flexibility of poly(ε-caprolactone) based nanofiber matrix prepared by electrospinning method whereas solvent casting method without any plasticizer produced very brittle, inflexible film of PCL. Modulation capacity of mechanical properties is also recorded. We tried to support our opinion by citing several similar findings available in the open literature. The electrospinning method helps in plasticization and in tuning mechanical properties.

IMPORTANCE Hyaluronic acid filler can be safely used as a soft-tissue filler for correction of infraorbital hollowing. It has a high overall patient satisfaction profile among patients. OBJECTIVE To report safety and patient satisfaction outcomes of Juvéderm Voluma XC for correction of infraorbital hollows. DESIGN, SETTING, AND PATIENTSThis was a retrospective observational study performed at a private ambulatory facial plastic and reconstructive surgery practice. Participants were all patients 21 to 85 years old who presented to our practice and underwent Juvéderm Voluma XC treatment for correction of infraorbital hollows as a singular intervention from February 2016 to March 2017. INTERVENTIONS Injection of JuvédermVoluma XC to the tear trough, nasojugal fold, and/or palpebromalar groove. MAIN OUTCOMES AND MEASURESPrimary outcome measures include the number of recorded short-and long-term adverse events, need for additional treatment, and patient questionnaire FACE-Q scores.RESULTS A total of 202 eyes were treated in 101 patients with a mean follow-up of 12 months. Patients were principally female (90 [89%]) with an average age of 54 years (range, 21-85 years). Most patients (99) had Fitzpatrick grade 1 to 4 skin type (98%) and had an infraorbital hollows score of 2 to 4 (89 [88%]). The average initial treatment volume was 1 mL with 18 patients (18%) requiring additional treatment within 3 months. The average time until additional treatment was 35.7 days. Adverse effects include bruising (in 10 [10%], contour irregularities (2 [2%]), swelling (3 [3%]), and Tyndall effect (1 [1%]). Hyaluronidase was required in 3 patients (3%). Forty-one patients completed the FACE-Q Satisfaction With Eyes survey, and 42 patients completed the FACE-Q Satisfaction With Decision survey (41% and 42%). Overall mean (SD) patient satisfaction (based on FACE-Q scores) was 71.1% (27.3) and 65.6% (31.3), respectively.CONCLUSIONS AND RELEVANCE Juvéderm Voluma XC has a high patient satisfaction profile and an acceptable safety profile for the correction of infraorbital hollowing.LEVEL OF EVIDENCE 4.