SUMMARY
Background. Muscle fiber (MF) cross-sectional area (CSA) and muscle strength are reduced in disuse muscle atrophy (DMA). However, whether approximate shapes of MF cross-section (AS-MFCS) are altered in DMA remains unknown. This study aimed to determine the AS-MFCS of atrophic MFs.
Methods. Eleven-week-old male Wistar rats were divided into control (CON) and sciatic nerve transection (SNT) groups before analysis of the soleus muscle.
Results. The CSA of atrophic fibers in the SNT group decreased to approximately 50% of that of MFs in the CON group. AS-MFCS in the CON and SNT groups were characterized by 5.6 and 5.5 vertices, respectively. The proportion of MFs with five or six angles accounted for 77% of the total fibers. The correlation between CSA and AS-MFCS was weak in both groups. The number of small angular fibers in the SNT group was significantly higher; however, CSA did not differ between the two groups.
Conclusions. These results revealed that CSA decreased at an early stage in the SNT group without major changes in the percentages of AS-MFCS. Moreover, the number of small angular fibers increased in the SNT group; however, the results suggest that effects on the number of vertices were minor at this stage.
KEY WORDS
Approximated polygon; atrophic fibers; disuse muscle atrophy; sciatic nerve transection; small angular fibers.