RESUMO
The adenovirus-mediated somatic transfer of the embryonic T-box transcription factor 18 (TBX18) gene can convert chamber cardiomyocytes into induced pacemaker cells. However, the translation of therapeutic TBX18-induced cardiac pacing faces safety challenges. Here we show that the myocardial expression of synthetic TBX18 mRNA in animals generates de novo pacing and limits innate and inflammatory immune responses. In rats, intramyocardially injected mRNA remained localized, whereas direct myocardial injection of an adenovirus carrying a reporter gene resulted in diffuse expression and in substantial spillover to the liver, spleen and lungs. Transient expression of TBX18 mRNA in rats led to de novo automaticity and pacemaker properties and, compared with the injection of adenovirus, to substantial reductions in the expression of inflammatory genes and in activated macrophage populations. In rodent and clinically relevant porcine models of complete heart block, intramyocardially injected TBX18 mRNA provided rate-adaptive cardiac pacing for one month that strongly correlated with the animal's sinus rhythm and physical activity. TBX18 mRNA may aid the development of biological pacemakers.
RESUMO
Type 2 diabetes mellitus, a metabolic disorder characterized by abnormally elevated blood sugar, poses a growing social, economic, and medical burden worldwide. The skeletal muscle is the largest metabolic organ responsible for glucose homeostasis in the body, and its inability to properly uptake sugar often precedes type 2 diabetes. Although exercise is known to have preventative and therapeutic effects on type 2 diabetes, the underlying mechanism of these beneficial effects is largely unknown. Animal studies have been conducted to better understand the pathophysiology of type 2 diabetes and the positive effects of exercise on type 2 diabetes. However, the complexity of in vivo systems and the inability of animal models to fully capture human type 2 diabetes genetics and pathophysiology are two major limitations in these animal studies. Fortunately, in vitro models capable of recapitulating human genetics and physiology provide promising avenues to overcome these obstacles. This review summarizes current in vitro type 2 diabetes models with focuses on the skeletal muscle, interorgan crosstalk, and exercise. We discuss diabetes, its pathophysiology, common in vitro type 2 diabetes skeletal muscle models, interorgan crosstalk type 2 diabetes models, exercise benefits on type 2 diabetes, and in vitro type 2 diabetes models with exercise.
RESUMO
Bioprinting has become an important tool for fabricating regenerative implants and in vitro cell culture platforms. However, until today, extrusion-based bioprinting processes are limited to resolutions of hundreds of micrometers, which hamper the reproduction of intrinsic functions and morphologies of living tissues. This study describes novel hydrogel-based bioinks for cell electrowriting (CEW) of well-organized cell-laden fiber structures with diameters ranging from 5 to 40 µm. Two novel photoresponsive hydrogel bioinks, that is, based on gelatin and silk fibroin, which display distinctly different gelation chemistries, are introduced. The rapid photomediated cross-linking mechanisms, electrical conductivity, and viscosity of these two engineered bioinks allow the fabrication of 3D ordered fiber constructs with small pores (down to 100 µm) with different geometries (e.g., squares, hexagons, and curved patterns) of relevant thicknesses (up to 200 µm). Importantly, the biocompatibility of the gelatin- and silk fibroin-based bioinks enables the fabrication of cell-laden constructs, while maintaining high cell viability post printing. Taken together, CEW and the two hydrogel bioinks open up fascinating opportunities to manufacture microstructured constructs for applications in regenerative medicine and in vitro models that can better resemble cellular microenvironments.