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Spermidine is an acetyltransferase inhibitor and a specific inducer of autophagy. Recently, spermidine is identified as a potential therapeutic agent for age-related muscle atrophy and inherited myopathies. However, the effect of spermidine on nonpathological skeletal muscle remains unclear. In this study, long-term spermidine administration in mice lowered the mean cross-sectional area of the gastrocnemius muscle and reduced the expression of myosin heavy chain isoforms in the muscle, which was associated with ubiquitination. Moreover, spermidine supplementation induced autophagy in satellite cells and enhanced satellite cell proliferation. ChIP assay revealed that spermidine repressed H3K56ac in the promoter of ACVR2B and lowered the binding affinity of Smad3 to the promoters of Myf5 and MyoD. Altogether, our results indicate that long-term administration of spermidine can activate satellite cells, as well as enhance autophagy, eventually resulting in muscle atrophy. In addition, H3K56ac and Smad3 emerged as key determinants of satellite cell activation.

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The formation of the gigaseal, a giga Omega-scale seal between the micropipette electrode and cell surface, is the keystone to measuring the extremely weak electric signals of cell ion channels in patch clamp technique. To determine a point on the cell surface facilitating gigaseal formation, 3D cell morphology information is required. However, the current 3D cell morphology measurement methods relying on special devices or easily causing clogging issues of the micropipette electrode due to contact on cells, are usually not applicable in the traditional patch clamp system. Addressing this, a noninvasive 3D cell morphology measurement method was developed in this paper for robotic patch clamp with a higher success rate of gigaseal formation. First, the measured bath impedance of the micropipette electrode was modeled and then utilized to measure the cell surface height noninvasively. Using the measured cell surface heights at key positions, the 3D cell morphology was fitted to determine a contact position on the cell surface to facilitate gigaseal formation. Finally, a robotic whole-patch clamp process was conducted at the determined contact position. Experimental results demonstrated that 100% and 90% success rates of noninvasive 3D cell morphology measurements were achieved on the cultured HEK-293 cells and pyramidal neurons in mouse brain slices, respectively, with an average measurement error of cell surface height less than 0.15 μm. At the determined contact position, significant improvements in success rates of gigaseal formation and whole-cell patch clamp operation were achieved in comparison to the results at the positions recommended in related work. Our research may spike inspiration to improve the success rates of gigaseal formation and patch clamp operation based on 3-D cell morphologies.

No abstract