Tissue engineered skeletal muscle model of rheumatoid arthritis using human primary skeletal muscle cells.

Rheumatoid arthritis (RA) is a chronic inflammatory disease primarily targeting the joints. Autoreactive immune cells involved in RA affect other tissues, including skeletal muscle. Patients with RA experience diminished physical function, limited mobility, reduced muscle function, chronic pain, and increased mortality. To explore the impact of RA on skeletal muscle, we engineered electrically responsive, contractile human skeletal muscle constructs (myobundles) using primary skeletal muscle cells isolated from the vastus lateralis muscle of 11 RA patients (aged 57-74) and 10 aged healthy donors (aged 55-76), as well as from the hamstring muscle of six young healthy donors (less than 18 years of age) as a benchmark. Since all patients were receiving treatment for the disease, RA disease activity was mild. In 2D culture, RA myoblast purity, growth rate, and senescence were not statistically different than aged controls; however, RA myoblast purity showed greater variance compared to controls. Surprisingly, in 3D culture, contractile force production by RA myobundles was greater compared to aged controls. In support of this finding, assessment of RA myofiber maturation showed increased area of sarcomeric α-actinin (SAA) expression over time compared to aged controls. Furthermore, a linear regression test indicated a positive correlation between SAA protein levels and tetanus force production in RA and controls. Our findings suggest that medications prescribed to RA patients may maintain-or even enhance-muscle function, and this effect is retained and observed in in vitro culture. Future studies regarding the effects of RA therapeutics on RA skeletal muscle, in vivo and in vitro, are warranted.

Modeling the Effect of TNF-α upon Drug-Induced Toxicity in Human, Tissue-Engineered Myobundles.

A number of significant muscle diseases, such as cachexia, sarcopenia, systemic chronic inflammation, along with inflammatory myopathies share TNF-α-dominated inflammation in their pathogenesis. In addition, inflammatory episodes may increase susceptibility to drug toxicity. To assess the effect of TNF-α-induced inflammation on drug responses, we engineered 3D, human skeletal myobundles, chronically exposed them to TNF-α during maturation, and measured the combined response of TNF-α and the chemotherapeutic doxorubicin on muscle function. First, the myobundle inflammatory environment was characterized by assessing the effects of TNF-α on 2D human skeletal muscle cultures and 3D human myobundles. High doses of TNF-α inhibited maturation in human 2D cultures and maturation and function in 3D myobundles. Then, a tetanus force dose-response curve was constructed to characterize doxorubicin's effects on function alone. The combination of TNF-α and 10 nM doxorubicin exhibited a synergistic effect on both twitch and tetanus force production. Overall, the results demonstrated that inflammation of a 3D, human skeletal muscle inflammatory system alters the response to doxorubicin.

Accelerated generation of free radicals by iron oxide nanoparticles in the presence of an alternating magnetic field.

The surfaces of iron oxide nanoparticles are capable of catalytically generating reactive oxygen species (ROS) through the Fenton and Haber-Weiss reactions. Fenton chemistry has been shown to be temperature dependent with an increase in activity up to 40 °C and then a decrease above this temperature as the hydrogen peroxide degrades into oxygen and water which limits the reaction. When exposed to an alternating magnetic field (AMF), iron oxide nanoparticles absorb the energy from the magnetic field and convert it into heat. In this study, we observed an increase in the degradation of methylene blue when a suspension of magnetite nanoparticles (Fe3O4) was exposed to an AMF indicating there was an increase in the ROS generation in response to the AMF. The increase in ROS generation compared to the Arrhenius prediction was both time and concentration dependent; in which we observed a decrease in ROS enhancement with increased time of exposure and concentration. We postulate that the decrease is due to agglomeration in the presence of the field. As the nanoparticles agglomerate, there is a decrease in surface area per mass limiting the reaction rate.