Histochemical alterations of re-innervated rat extensor digitorum longus muscle after end-to-end or graft repair: a comparative histomorphological study

Immunohistochemical analysis of the quadriceps femoris muscle before and after total knee arthroplasty

BACKGROUND

The number of total knee arthroplasties (TKA) has increased steadily with the aging of the population. This surgical procedure is recognized for its success in pain relief and restoration of knee function. However, decreased quadriceps femoris (QF) muscle strength after TKA is frequently observed but with unknown etiology. Evidence suggests that the location of the operative incision (i.e., surgical access) can influence QF muscle structure and function. The present study aimed to assess the fiber type composition, structure and assembly of the QF's vastus medialis (VM) and vastus lateralis (VL) muscles before and after TKA.

METHODS

Muscle biopsies (VM and VL muscles) were collected from patients previously submitted to TKA via the medial parapatellar route and undergoing TKA revision (main group, n = 9) and patients with osteoarthrosis (OA) who were due to undergo TKA (control group: n = 18). The biopsied muscle tissue was prepared, stored, and then sectioned in a cryostat at -25 °C. The tissue sections were evaluated using routine staining techniques in pathological anatomy and histochemistry.

RESULTS

The normal mosaic pattern of the medial and lateral knee muscles was observed in the main and control groups, with no evidence of peripheral nerve damage. Notably, 88.9 % of the patients exhibited mild to severe VL atrophy, while only 11.1 % of patients in the control group presented this feature (P < 0.001).

CONCLUSIONS

The medial parapatellar incision for TKA surgical access does not generate definitive morphological changes in the VM and VL muscle fibers but may contribute to VL atrophy.

Properties of the tibialis anterior muscle after treatment with laser therapy and natural latex protein following sciatic nerve crush

INTRODUCTION

In this study we evaluated the characteristics of the tibialis anterior muscle after sciatic nerve crush and treatment with low-level laser therapy (LLLT) or the protein from natural latex (P1).

METHODS

We studied the following 6 groups of male Wistar rats: control (CG); exposed nerve (EG); injured nerve (IG); injured nerve with LLLT (LG); injured nerve with P1 (PG); and injured nerve with P1 and LLLT (LPG).

RESULTS

After 4 weeks, muscle morphology showed improvement in the treated groups; after 8 weeks, the treated groups resembled controls, especially the PG. Morphometry revealed muscle fiber atrophy after nerve injury, with time-dependent recovery. Histochemical analysis revealed increased intermediate fiber area. The PG was more similar to controls with NADH staining, whereas the LPG more closely resembled controls with SDH staining.

CONCLUSION

Treatment using only P1 proved most efficient, revealing a negative interaction between P1 and LLLT.

Characterizing activity and muscle atrophy changes in rats with neuropathic pain: a pilot study

The study of neuropathic pain has focused on changes within the nervous system, but little research has described systemic changes that may accompany neuropathic pain.

OBJECTIVE

As part of a larger project characterizing the metabolic, activity, and musculoskeletal changes associated with neuropathic pain, the objective of the current study was to characterize changes in spontaneous activity and skeletal muscle mass using an established animal model of neuropathic pain, the chronic constriction injury (CCI) model.

METHOD

Male Sprague-Dawley rats were used in this pre- and posttest quasi-experimental study. The experimental group (n = 13) received CCI surgery, while age- and weight-matched rats received sham surgery (SHAM; n = 5). Thermal testing verified the presence of neuropathic pain. Spontaneous cage activity was measured gravimetrically prior to and following CCI (n = 4). Animals were euthanized and skeletal muscle was dissected and weighed to determine muscle atrophy.

RESULTS

Shorter foot withdrawal latency of the ipsilateral hind limb confirmed the presence of thermal hyperalgesia in CCI rats, a sign of neuropathic pain. Weight increased in both CCI and SHAM rats. Spontaneous activity decreased following CCI ligation. Muscles of the ipsilateral hind limb weighed significantly less than contralateral hind limb muscles in CCI rats 2 and 6 weeks after surgery. In addition, CCI rats had smaller ipsilateral hind limb muscles than SHAM rats.

CONCLUSION

Neuropathic pain contributes to skeletal muscle atrophy and decreases in activity in rats.

Differences in sensitivity to rocuronium among orbicularis oris muscles innervated by normal or damaged facial nerves and gastrocnemius muscle innervated by somatic nerve in rats: combined morphological and functional analyses

OBJECTIVES/HYPOTHESIS

To evaluate mechanisms of discrepant responses to the nondepolarizing muscle relaxant rocuronium among normal and injured facial nerve-innervated orbicularis oris and tibial nerve-innervated gastrocnemius, and to provide information for the proper use of muscle relaxants to balance evoked electromyography (EEMG) monitoring and immobility in general anesthesia.

STUDY DESIGN

Randomized controlled study.

METHODS

Right-sided facial nerve injury was induced by crush axotomy in 18 Sprague-Dawley rats. At different rocuronium concentrations, muscular tension amplitude (MTA) was determined in vitro for normal and injured facial nerve-innervated orbicularis oris and gastrocnemius; the number of unsaturated acetylcholine receptors (AChRs) at end plates was determined by (125) I-α-bungarotoxin staining followed with gamma spectroscopy. The morphological composition of muscle fibers was determined by histological examination.

RESULTS

Following rocuronium incubation, the percentage of MTA inhibition (MTAI%) of gastrocnemius was significantly higher than the corresponding values of orbicularis oris (P < .05), and the degree of saturation of AChR in gastrocnemius was significantly greater than that in orbicularis oris (P < .05). The baseline MTA and AChR density of injured-side orbicularis oris was significantly smaller than those of the normal side, whereas no significant difference was found regarding MTAI% and the degree of AChR saturation between the normal and injured side.

CONCLUSIONS

The affinity of AChR at end plates and different number of AChR per unit fiber cross-sectional area may be the mechanisms for differential sensitivities to neuromuscular blockers between facial nerve-innervated muscles and somatic nerve-innervated muscles. The lower EEMG responses in the impaired facial nerve-innervated muscles may result from the lower AChR density at end plates compared with the normal facial nerve-innervated muscles.

Reinnervation-induced alterations in rat skeletal muscle

Denervation-induced myofiber atrophy can be reversed by reinnervation. Growing reinnervated myofibers upregulate numerous molecules, many of which determine the muscle fiber type. In the present study we aimed at identifying factors that might contribute specifically to myofiber growth after reinnervation. The common peroneal nerve of 15 male Wistar rats was cut and resutured without delay (9 animals) or with a delay of 4 weeks (6 animals). We studied the transcriptional repertoire of intact reinnervated tibialis anterior muscle by microarray gene analysis. We assessed SC activation by immunolabeling using anti-MyoD and -myogenin antibodies. The percentage of SC expressing MyoD reached up to 50% of M-cadherin+ cells whereas the percentage of SC expressing myogenin was normal (<10%) in all muscles examined. The values of ipsi- and contralateral muscles did not differ significantly from one another between right and left leg (p<0.05). Thirteen known genes were differentially regulated after reinnervation compared with contralateral muscles. Five of them determine the slow-twitch fiber type (four and a half LIM domains 3, cardiac beta-myosin heavy chain, calsequestrin 2, troponin C (slow), and heart myosin light chain), and three of them are neurally regulated (thrombospondin 4, transferrin receptor, cardiac ankyrin repeat protein). The results strengthen the notion that reinnervaton affects the molecular repertoire of the myofibers directly, leading to fiber type transformation and partial reversal of the denervation phenotype. By contrast, SC do not appear to be affected by reinnervation directly. They can be activated both in reinnervated and contralateral muscles, and they do not fully differentiate. This makes them unlikely to contribute to myofiber growth.

The cut intramuscular nerve affects the recovery in the lacerated skeletal muscle

The recovery of lacerated skeletal muscles are said to be slow and incomplete. Often the intramuscular (IM-) nerve is concomitantly cut, but never repaired. We questioned whether the IM-nerve should also be reanastamosed before repairing the skeletal muscle. Before answering this, it was necessary to know if the cut IM nerve would have an effect on the recovery of the segment of muscle distal to the level of the laceration. This study investigates the recovery of lacerated muscles after repair, and compares a complete muscle laceration where the main IM-nerve was concomitantly cut and an incomplete muscle laceration where the IM-nerve was preserved intact. The medial gastrocnemius (MG) of the adult male New Zealand White rabbit was used, with the contralateral muscle as a sham control. The laceration was at the proximal quarter of the muscle, distal to the entry point of the nerve branch from the tibial nerve into the muscle belly. Twenty-eight weeks post-repair, the lacerated MG with the IM-nerve intact showed improved muscle wet weight, near normal morphology and contractile properties, and return of muscle fiber type mix and size. The repaired lacerated MG with their IM-nerve concomitantly cut demonstrated loss of muscle wet weight, obvious fibrosis, mononuclear proliferation with fatty infiltration, increase in type-1 fibers and muscle fiber atrophy in the distal portion. We postulate that it might be important to repair the intramuscular nerve branch by microanastomosis when repairing a vital skeletal muscle that is lacerated.

Graft repair of the peroneal nerve restores histochemical profile after long-term reinnervation of the rat extensor digitorum longus muscle in contrast to end-to-end repair

Declining motor function is a prominent feature of ageing physiology. One reason for this is a reduction in plasticity that normally compensates for ongoing reorganization of motor units under physiological conditions. Previous work from our laboratory has shown that microsurgical repair of the transected peroneal nerve is followed by considerable changes in the histochemical profile of the reinnervated extensor digitorum longus (EDL) muscle and that these changes are dependent on both the time and the type of nerve repair. At 6 months postoperatively, a trend toward reversibility could be discerned. In the present work, we analysed the long-term reorganization of histochemical motor unit distribution patterns 15 months after performing either end-to-end repair or grafting of the peroneal nerve in 3-month-old rats. In addition, the EDL muscles of an age-matched control group (age 18 months) were analysed for age-dependent changes. We observed a loss of histochemical organization of motor units leading to an additional fibre type (SDH-INT) in the control group. Fifteen months after end-to-end repair, the histochemical profile showed a decrease in fibre type IIA and an increase in fibre type SDH-INT (P < 0.05), indicating a profound histochemical disorganization of motor units. In contrast, nerve grafting largely restored the histochemical profile of reinnervated EDL muscles. Fibre type grouping was present after both types of nerve repair. These findings show that reorganization of the histochemical profile in reinnervated muscles is dependent on the time and type of nerve repair and is long lasting. In this study, grafting provided superior results compared with end-to-end repair. These long-term results after peripheral nerve repair are influenced by age-dependent changes. Accordingly, nerve repair reduces the normal functional plasticity of motor unit organization. This reduction is enhanced by increasing age.