Muscle reinnervation with nerve-muscle-endplate band grafting technique: correlation between force recovery and axonal regeneration

Abstract

Background This study was designed to determine the correlation between functional recovery and the extent of axonal regeneration after muscle reinnervation with our recently developed nerve-muscle-endplate band grafting (NMEG) technique in a rat model. Materials and methods The right experimentally paralyzed sternomastoid (SM) muscle by nerve transection was immediately reinnervated with a NMEG pedicle harvested from a neighboring sternohyoid (SH) muscle. The NMEG pedicle contained a muscle block (6x6x3 mm), a donor nerve branch with nerve terminals and a motor endplate band. Three months after surgery, the tetanic force of the SM muscle was measured and the regenerated axons in the muscle were detected using neurofilament immunohistochemistry. Results The results showed that the maximal tetanic force (a measure of muscle functional recovery) of the NMEG reinnervated SM muscle reached up to 66.0% of the normal control. The wet weight of the reinnervated SM muscle (a measure of muscle mass recovery) was 87.2% of the control. The area fraction of the regenerating axons visualized with neurofilament staining within the NMEG reinnervated SM muscle (a measure of muscle reinnervation) was 42.3%. A positive correlation was revealed between the extent of muscle reinnervation and maximal muscle force. Conclusions Our newly developed NMEG technique results in satisfactory functional outcomes and nerve regeneration. Further improvement in the functional recovery after NMEG reinnervation, could be achieved by refining the surgical procedure and creating an ideal environment that favors axon-endplate connections and accelerates axonal growth and sprouting.

Reinnervation of denervated muscle by implantation of nerve‐muscle‐endplate band graft to the native motor zone of the target muscle

“…However, entire muscle reinnervation and complete functional recovery was not achieved. We found that approximately one‐third of the distal myofibers in the target muscle were not reinnervated 3 months after surgery (Mu et al., ; Sobotka & Mu, ). These findings suggest that partial muscle reinnervation accounts for incomplete functional recovery.…”

“…A healthy endplate band with a nerve branch and terminals that innervates an expendable muscle can be transplanted to a more functionally important denervated muscle for restoring its motor function. Over the past years, we have studied the NMEG technique by determining innervation patterns (Mu et al., ; Zhang, Mu, Su, & Sobotka, ) and contractile properties of the rat recipient and donor muscles (Sobotka & Mu, ), and conducted surgical feasibility studies and a series of reinnervation experiments using the NMEG technique and conventional EEA in a rat model (Mu et al., ; Sobotka & Mu, , ,b, ). Several lines of evidence from a number of quantitative analyses demonstrated that the NMEG procedure results in encouraging functional recovery (67% of the control) (Mu et al., ).…”

Nerve growth factor and basic fibroblast growth factor promote reinnervation by nerve−muscle−endplate grafting

“…The stained sections were examined under a fluorescence microscope (Axioplan‐1; Carl Zeiss, Gottingen, Germany) and photographed with a USB 3.0 digital microscope camera (Infinity 3‐3URC; Lumenera Corp., Ottawa, Ontario, Canada). The extent of axonal regeneration and muscle reinnervation was evaluated by quantifying the neurofilament‐immunoreactive (NF‐ir) axons within the treated muscles as described in our previous publications . The intramuscular axonal density was assessed by computing the number of the NF‐ir axons and the area fraction of the axons within a section area (1.0 mm 2 ).…”

“…The degree of functional recovery of the treated muscles was assessed by measuring the maximal tetanic force, as described in our previous publications. 9,11,[45][46][47][48][49] Briefly, the right treated and the left control SM muscles in each animal were exposed and dissected free from the surrounding tissues. The rostral tendon of each muscle was then divided at its insertion, tied with a 2-0 suture, and attached to a servomotor lever arm (Model 305B Dual-Mode Lever Arm System; Aurora Scientific, Inc., Aurora, Ontario, Canada).…”

“…The extent of axonal regeneration and muscle reinnervation was evaluated by quantifying the neurofilamentimmunoreactive (NF-ir) axons within the treated muscles as described in our previous publications. 11,47,49 The intramuscular axonal density was assessed by computing the number of the NF-ir axons and the area fraction of the axons within a section area (1.0 mm 2 ). For a given muscle, 3 stained sections at different spatial levels through the muscle were selected to count NF-ir axons.…”