Mimicking exercise in vitro: effects of myotube contractions and mechanical stretch on omics.

The number of studies using skeletal muscle (SkM) cell culture models to study exercise in vitro are rapidly expanding. Progressively, more comprehensive analysis methods, such as different omics approaches including transcriptomics, proteomics, and metabolomics have been used to examine the intra- and extracellular molecular responses to exercise mimicking stimuli in cultured myotubes. Among other techniques, exercise-like electrical pulse stimulation (EL-EPS) and mechanical stretch of SkM cells are the two most commonly used methods to mimic exercise in vitro. In this mini-review, we focus on these two approaches and their effects on the omics of myotubes and/or cell culture media. Furthermore, besides traditional two-dimensional (2-D) methods, the use of three-dimensional (3-D) SkM approaches are increasing in the field of in vitro exercise mimicry. Our aim with this mini-review is to provide the reader with an up-to-date overview of the 2-D and 3-D models and the use of omics approaches to study the molecular response to exercise in vitro.

Fluorescent probes as a tool for cell population tracking in spontaneously active neural networks derived from human pluripotent stem cells.

Applications such as 3D cultures and tissue modelling require cell tracking with non-invasive methods. In this work, the suitability of two fluorescent probes, CellTracker, CT, and long chain carbocyanine dye, DiD, was investigated for long-term culturing of labeled human pluripotent stem cell-derived neural cells. We found that these dyes did not affect the cell viability. However, proliferation was decreased in DiD labeled cell population. With both dyes the labeling was stable up to 4 weeks. CT and DiD labeled cells could be co-cultured and, importantly, these mixed populations had their normal ability to form spontaneous electrical network activity. In conclusion, human neural cells can be successfully labeled with these two fluorescent probes without significantly affecting the cell characteristics. These labeled cells could be utilized further in e.g. building controlled neuronal networks for neurotoxicity screening platforms, combining cells with biomaterials for 3D studies, and graft development.