Correlation of contractile function recovery with acetylcholine receptor changes in a rat muscle flap model

Abstract

The aim of this study was to investigate the correlation between contractile function recovery and changes of acetylcholine receptors (AChR) in a transferred muscle flap following reinnervation. Orthotopic transfer of the gracilis muscle flap with repair of its nerve was performed bilaterally in 48 rats. The rats were randomly divided into six experimental groups based on the time intervals for assessments (1, 4, 5, 10, 20, and 30 weeks). Sixteen gracilis muscle samples from eight rats without surgery were used as the controls. In each group, muscle contractile force and weight were measured (n = 16). The AChR numbers (n = 8) and subunits (epsilon and gamma) mRNA (n = 8) were examined using [(125)I]-alpha-bungarotoxin and fluorescent quantitative-PCR. The results showed the AChR numbers in the muscle flap increased from 4 to 20 weeks after reinnervation and correlated with recovery of the tetanic contraction force. However, correlation between the increase of AChR number with the specific tension (peak contractile force normalized to wet muscle weight) was only found from 4 to 10 weeks postoperatively. The expression of gamma-subunit mRNA increased at the early period after flap transfer and then decreased rapidly, whereas the epsilon-subunit mRNA recovered gradually since fourth week postoperatively. A small amount of gamma-subunit mRNA could still be detected at 30 weeks after surgery. In conclusion, following reinnervation of the transferred muscle flap, the contractile functional recovery is partially correlated to increase of the AChRepsilon. Our findings may provide evidence for further study of improving muscle function in functional reconstruction by targeting the AChR.

Failed reinnervation in aging skeletal muscle

“…We also noted a nearly 60 % decrease in AChR ε subunit in Sarco soleus muscle, which contrasts with the increase in AChR ε that was seen in VO rat muscle. In this respect, previous studies have shown that following denervation AChR ε expression undergoes a multiphasic response: (i) an initial decrease in the first 10 day post-denervation [29]; (ii) a sharp increase observed approximately 4 weeks following denervation; (iii) a decline over the next 4 weeks; and (iv) a gradual secondary increase when denervation persists beyond 2 months [30, 31]. Thus, the differences between the VO rat and Sarco mouse likely reflect differences in the duration of denervation, with the higher AChR ε in VO rat reflecting more prolonged denervation and the reduced AChR ε in Sarco mouse reflecting the acute denervation response.…”

Myogenic Differentiation of Mesenchymal Stem Cells in a Newly Developed Neurotised AV-Loop Model

“…A well-established tool to achieve this goal is the AV-loop model [31, 32]. However, to gain functional muscle tissue, besides axial vascularization, an innervation by a motor nerve seems indispensable [22]. In the past mainly myoblasts or satellite cells have been used for skeletal muscle TE, but they showed limited cell survival in vivo .…”

“…However, this single study only allowed the use of a sensoric nerve [20]. Agrawal and Zhang and coworkers study the dependence of motoric innervation in the context of muscle regeneration and motoric neurotization in transplanted muscle flaps [21, 22]. Neurotization can be a stimulus to activate mechanisms of muscle differentiation and contraction.…”

Microsurgical Transplantation of Pedicled Muscles in an Isolation Chamber—A Novel Approach to Engineering Muscle Constructs via Perfusion-Decellularization

“…The effect of nerve coaptation (tibial nerve to a branch of the obturator nerve as described in the EPI-loop model [ 30 ]) would be the next step to analyze. Zhang et al performed orthotopic transplantation of rat gracilis muscle with transection of the obturator nerve and subsequent neurorrhaphy of the nerve [ 31 ]. After 5–20 weeks after reinnervation, muscle function started to recover.…”