Initiation of muscle regeneration is delayed in tibialis anterior and gastrocnemius muscles in Akita mice.

<p>Regions of necrotic muscle tissue in (A) TA and (B) gastrocnemius (GAS) demonstrate attenuated response of Myh3-expressing myofibers in diabetic mice. An * denotes a significant difference detected by t-test (p<0.05). (C) Representative image of Myh3 immunofluorescent stained (red) TA and GAS necrotic regions. Co-staining of laminin (green) and nuclei with DAPI (blue) was performed. In the actively regenerating regions of the (D) TA and (E) GAS, the attenuation of Myh3 expression was not as severe, and at 10 days post-injury, was found to be significantly elevated in diabetic mice compared to wild type, indicative of delayed regeneration (significant interaction [P<0.05]). The * indicates significant differences detected by post-hoc testing (P<0.05). Conversely, (F) Akita soleus (SOL) demonstrates no impairment in establishing Myh3 expression following injury and does not continue to significantly overexpress Myh3 at 10 days post-injury. (G) Representative image of regenerating regions of muscles at 5 days post-injury stained for Myh3 (red) and laminin (green). Inset (derived from TA muscles) is provided without green channel to clearly demonstrate Myh3 stain morphology. Scale bar represents 50 um in panels C and G. (H) MMP-9 immunobloting on uninjured and regenerating (2 days post-injury) TA, GAS and SOL muscles from WT and Akita mice demonstrate the intrinisic differences between muscles in pro-MMP-9 expression (main effect of muscle group; P<0.05), but no differences between WT and Akita mice. MMP-9 content is relative to beta-actin loading controls and representative MMP-9 blots are included.