Abstract The cross‐sectional Master Athletic Laboratory Study of Intramuscular Connective Tissue (MALICoT, DRKS00015764) examined effects of athletic exercise and age on endomysium content in human soleus muscle. Forty‐three clinically healthy male participants were grouped into young (20–35 years) nonphysically active controls ( n = 12), young power‐trained athletes ( n = 10), older (60–75 years) nonphysically active controls ( n = 11), and older power‐trained athletes ( n = 10). Biopsy specimens from the left soleus muscle of each participant were cryo‐sectioned for (i) routine histological staining for myopathological evaluation, (ii) deep learning‐based image analysis of H&E‐ and MHC‐stained sections, (iii) laminin‐γ‐1/collagen IV, collagen I, and collagen III immunofluorescence image analysis, and (iv) quantitative proteomics. Myopathological evaluation revealed normal skeletal muscle in 26 participants, while 11, 4, 1 and 1 biopsies showed unspecific myopathological changes, chronic neurogenic atrophy, type‐II fiber atrophy, and unspecific myositic changes, respectively. Analysis of H&E‐, MHC‐, laminin‐, and collagen‐stained sections revealed a 1.3‐fold higher level of “mean fiber area” in young power‐trained and aged unathletic participants. No significant effect was detected in the endomysium content. Proteomic analysis revealed no group‐specific differences except that plasma membrane calcium‐transporting ATPase 2 was less abundant in samples from aged power‐trained athletes. Overall, neither athletic exercise nor age had an effect on the content or composition of the endomysium in the soleus muscle of male humans.
Clemen et al. (Fri,) studied this question.