Effects of Lower- and Higher-Volume Resistance Exercise on Serum Total and Free Testosterone, Skeletal Muscle Testosterone and Dihydrotestosterone Content, and Skeletal Muscle Androgen Receptor mRNA Expression and Protein Content

Testosterone is the primary sex steroid hormone within males. Its effects are ubiquitous, and can be categorized as either anabolic or androgenic. Testosterone exerts its effects on a specific nuclear androgen receptor (AR). Upon binding testosterone, the AR translocates to the nucleus of the cell. Once in the nucleus of the cell, the active AR complex binds to the androgen response element on DNA resulting in an up-regulation of gene expression. Androgen receptors are found in skeletal muscle which is responsive to testosterone. The binding of testosterone to the AR results in DNA binding, and subsequently promotes protein synthesis (anabolism) and a decrease in the breakdown of muscle tissue (catabolism). Both AR mRNA and protein expression and testosterone levels affect muscle protein balance. It is known that high intensity resistance exercise increase endogenous serum testosterone levels. Therefore, the purpose of this study was to examine the ability of a resistance exercise-induced elevation in serum and free testosterone to increase skeletal muscle testosterone, 5α-dihydrotestosterone (DHT), AR mRNA expression and protein content. In a randomized cross-over design, venous blood was obtained in male participants immediately before, after, and 30min, 1 hr, 2 hr, 3 hr, and 24 hr after a single bout of exercise. Muscle samples were also obtained immediately before, after, and 3 hr, 24 hr after exercise. Exercise bouts were either lower volume (LV) and consisted of a lower body resistance exercise program (knee extensions) or higher volume (HV) consisting of an upper body/lower body resistance exercise program (bench press, seated rows, shoulder press, knee extensions). Exercise bouts were separated by one week. From each blood sample, the levels of serum and total testosterone were determined. From each muscle sample, the concentration of testosterone, and dihydrotestosterone (DHT) was determined, along with the mRNA expression and protein content of the androgen receptor. Statistical analysis was performed by utilizing separate 2x4 and 2x7 (Session x Test) factorial analyses of variance (ANOVA) with repeated measures for muscle and blood analyses, respectively. Further analysis of the main effects was performed by separate one-way ANOVAs. Significant between-group differences were then determined involving the Tukey’s Post Hoc Test

Delivery of Tissue-Targeted Scalpels: Opportunities and Challenges for In Vivo CRISPR/Cas-Based Genome Editing

Copyright © 2020 American Chemical Society. CRISPR/Cas9-based genome editing has quickly emerged as a powerful breakthrough technology for use in diverse settings across biomedical research and therapeutic development. Recent efforts toward understanding gene modification methods in vitro have led to substantial improvements in ex vivo genome editing efficiency. Because disease targets for genomic correction are often localized in specific organs, realization of the full potential of genomic medicines will require delivery of CRISPR/Cas9 systems targeting specific tissues and cells directly in vivo. In this Perspective, we focus on progress toward in vivo delivery of CRISPR/Cas components. Viral and nonviral delivery systems are both promising for gene editing in diverse tissues via local injection and systemic injection. We describe the various viral vectors and synthetic nonviral materials used for in vivo gene editing and applications to research and therapeutic models, and summarize opportunities and progress to date for both methods. We also discuss challenges for viral delivery, including overcoming limited packaging capacity, immunogenicity associated with multiple dosing, and the potential for off-target effects, and nonviral delivery, including efforts to increase efficacy and to expand utility of nonviral carriers for use in extrahepatic tissues and cancer. Looking ahead, additional advances in the safety and efficiency of viral and nonviral delivery systems for tissue- and cell-type-specific gene editing will be required to enable broad clinical translation. We provide a summary of current delivery systems used for in vivo genome editing, organized with respect to route of administration, and highlight immediate opportunities for biomedical research and applications. Furthermore, we discuss current challenges for in vivo delivery of CRISPR/Cas9 systems to guide the development of future therapies

Hydrophobic Optimization of Functional Poly(TPAE-co-suberoyl chloride) for Extrahepatic mRNA Delivery following Intravenous Administration

Messenger RNA (mRNA) has generated great attention due to its broad potential therapeutic applications, including vaccines, protein replacement therapy, and immunotherapy. Compared to other nucleic acids (e.g., siRNA and pDNA), there are more opportunities to improve the delivery efficacy of mRNA through systematic optimization. In this report, we studied a high-throughput library of 1200 functional polyesters for systemic mRNA delivery. We focused on the chemical investigation of hydrophobic optimization as a method to adjust mRNA polyplex stability, diameter, pKa, and efficacy. Focusing on a region of the library heatmap (PE4K-A17), we further explored the delivery of luciferase mRNA to IGROV1 ovarian cancer cells in vitro and to C57BL/6 mice in vivo following intravenous administration. PE4K-A17-0.2C8 was identified as an efficacious carrier for delivering mRNA to mouse lungs. The delivery selectivity between organs (lungs versus spleen) was found to be tunable through chemical modification of polyesters (both alkyl chain length and molar ratio in the formulation). Cre recombinase mRNA was delivered to the Lox-stop-lox tdTomato mouse model to study potential application in gene editing. Overall, we identified a series of polymer-mRNA polyplexes stabilized with Pluronic F-127 for safe and effective delivery to mouse lungs and spleens. Structure–activity relationships between alkyl side chains and in vivo delivery were elucidated, which may be informative for the continued development of polymer-based mRNA delivery