Loss of Acta2 in cardiac fibroblasts does not prevent the myofibroblast differentiation or affect the cardiac repair after myocardial infarction.

In response to myocardial infarction (MI), quiescent cardiac fibroblasts differentiate into myofibroblasts mediating tissue repair. One of the most widely accepted markers of myofibroblast differentiation is the expression of Acta2 which encodes smooth muscle alpha-actin (SMαA) that is assembled into stress fibers. However, the requirement of Acta2/SMαA in the myofibroblast differentiation of cardiac fibroblasts and its role in post-MI cardiac repair remained unknown. To answer these questions, we generated a tamoxifen-inducible cardiac fibroblast-specific Acta2 knockout mouse line. Surprisingly, mice that lacked Acta2 in cardiac fibroblasts had a normal post-MI survival rate. Moreover, Acta2 deletion did not affect the function or histology of infarcted hearts. No difference was detected in the proliferation, migration, or contractility between WT and Acta2-null cardiac myofibroblasts. Acta2-null cardiac myofibroblasts had a normal total filamentous actin level and total actin level. Acta2 deletion caused a significant compensatory increase in the transcription level of non-Acta2 actin isoforms, especially Actg2 and Acta1. Moreover, in myofibroblasts, the transcription levels of cytoplasmic actin isoforms were significantly higher than those of muscle actin isoforms. In addition, we found that myocardin-related transcription factor-A is critical for myofibroblast differentiation but is not required for the compensatory effects of non-Acta2 isoforms. In conclusion, the Acta2 deletion does not prevent the myofibroblast differentiation of cardiac fibroblasts or affect the post-MI cardiac repair, and the increased expression and stress fiber formation of non-SMαA actin isoforms and the functional redundancy between actin isoforms are able to compensate for the loss of Acta2 in cardiac myofibroblasts.

A modular surgical simulator for microlaryngoscopy using standard instruments and the carbon dioxide laser.

Objective: Build a microlaryngoscopy surgical simulator for endoscopic laryngeal surgery using standard microsurgical instruments and a CO2 laser. Study design: Anatomical modeling, CAD design and 3D printed manufacturing. Subjects and methods: We created a modular design for a microlaryngoscopy simulator in CAD software. Components include plastic and stainless-steel models of a standard operating laryngoscope and a cassette system for mounting porcine or synthetic models of the vocal folds. All simulator parts, including the metallic laryngoscope model, were manufactured using 3D printing technology. Tumors were simulated in porcine tissue models by injecting a soy protein-based tumor phantom. Residents and faculty in the Louisiana State University otolaryngology department evaluated the system. Each participant performed microlaryngoscopy with laser resection on a porcine larynx and cold instrument procedures on synthetic vocal folds. Participants scored the simulator using a 5-point Likert scale. Results: The microlaryngeal surgical simulator demonstrated in this project is realistic, economical, and easily assembled. We have included 3D printed parts files and detailed assembly instructions that will enable educators interested in surgical simulation to build the device.Participants in the simulator evaluation session felt that the simulator faithfully represented the procedure to resect vocal fold lesions using a CO2 laser. The synthetic model allows the trainee to develop hand-eye coordination while using standard laryngeal instruments. Conclusions: The simulator described herein will enable surgeons to acquire the surgical skills necessary to perform operative microlaryngoscopy prior to operating on live patients.

Attenuating Fibrotic Markers of Patient-Derived Dermal Fibroblasts by Thiolated Lignin Composites.

We report the use of phenolic functional groups of lignosulfonate to impart antioxidant properties and the cell binding domains of gelatin to enhance cell adhesion for poly(ethylene glycol) (PEG)-based scaffolds. Chemoselective thiol-ene chemistry was utilized to form composites with thiolated lignosulfonate (TLS) and methacrylated fish gelatin (fGelMA). Antioxidant properties of TLS were not altered after thiolation and the levels of antioxidation were comparable to those of L-ascorbic acid. PEG-fGelMA-TLS composites significantly reduced the difference in COL1A1, ACTA2, TGFB1, and HIF1A genes between high-scarring and low-scarring hdFBs, providing the potential utility of TLS to attenuate fibrotic responses.

Histone H4 LRS mutations can attenuate UV mutagenesis without affecting PCNA ubiquitination or sumoylation.

UV is a significant environmental agent that damages DNA. Translesion synthesis (TLS) is a DNA damage tolerance pathway that utilizes specialized DNA polymerases to replicate through the damaged DNA, often leading to mutagenesis. In eukaryotic cells, genomic DNA is organized into chromatin that is composed of nucleosomes. To date, if and/or how TLS is regulated by a specific nucleosome feature has been undocumented. We found that mutations of multiple histone H4 residues mostly or entirely embedded in the nucleosomal LRS (loss of ribosomal DNA-silencing) domain attenuate UV mutagenesis in Saccharomyces cerevisiae. The attenuation is not caused by an alteration of ubiquitination or sumoylation of PCNA (proliferating cell nuclear antigen), the modifications well-known to regulate TLS. Also, the attenuation is not caused by decreased chromatin accessibility, or by alterations of methylation of histone H3 K79, which is at the center of the LRS surface. The attenuation may result from compromised TLS by both DNA polymerases ζ and η, in which Rad6 and Rad5 are but Rad18 is not implicated. We propose that a feature of the LRS is recognized or accessed by the TLS machineries either during/after a nucleosome is disassembled in front of a lesion-stalled replication fork, or during/before a nucleosome is reassembled behind a lesion-stalled replication fork.