Fiber type specific myonuclear and satellite cell content comparisons between the vastus lateralis and soleus muscles in humans

Abstract

Objectives: The purpose of this study was to compare fiber type specific myonuclear and satellite cell number of the vastus lateralis and soleus muscles in humans. Hypotheses: Myonuclear number (MNN), myonuclear domain (MND), and satellite cell number (SCN) would be similar within each fiber type between the vastus lateralis and soleus. Methods: Muscle biopsies from the vastus lateralis and soleus of 24 individuals (34±7y, 24-55y) were sectioned, immunofluorescently stained, and analyzed for MNN, MND, and SCN in slow (myosin heavy chain (MHC) I) and fast (MHC IIa) muscle fibers. SCN was determined only in MHC I fibers for the soleus. MNN and MND were compared for 24 individuals, while SCN was compared for 19 individuals. Results: MNN was similar in MHC I (3.32±0.81 vs. 3.66±0.65 myonuclei/fiber, P=0.067) and IIa (3.63±0.82 vs. 3.83±0.68 myonuclei/fiber, P>0.05) fibers of the vastus lateralis and soleus. Similarly, MND was not different in MHC I (1649±305 vs. 1673±340 μm2/myonuclei, P>0.05) and IIa (1705±313 vs. 1819±394 μm2/myonuclei, P>0.05) fibers of the vastus lateralis and soleus. However, SCN was 62% higher (p<0.05) in MHC I fibers of the soleus (0.127±0.039 satellite cells/fiber) compared with MHC I fibers of the vastus lateralis (0.083±0.024 satellite cells/fiber). Conclusions: The literature is void of comparisons of myonuclei and satellite numbers across different human muscles. These initial results suggest myonuclear number and the area “governed” by each myonuclei (i.e., the myonuclear domain) appears to be similar within the two main fiber types found in the vastus lateralis and soleus muscles. Interestingly, within the same slow fiber type (i.e., MHC I fibers) across these two muscles, it appears the soleus is programmed to have a substantially higher satellite cell content. The basis for this intrinsic difference in slow myofiber satellite profile may be related to the differences in daily myocellular activity between the vastus lateralis and soleus. This research was supported by the National Aeronautics and Space Administration, NNJ06HF59G; the Institute for Translational Sciences at the University of Texas Medical Branch, supported in part by a Clinical and Translational Science Award (UR1TR000071) from the National Center for Advancing Translational Sciences, National Institutes of Health; the NASA Flight Analogs Project; and the Human Bioenergetic Program at Ball State University. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.