Severe degeneration of rabbit vastus intermedius muscle immobilized in shortened position

Combination Therapy of Polydeoxyribonucleotide and Microcurrent in Muscle Regeneration on Cast-Induced Muscle Atrophy in Rabbit

Background. The aim of this study was to evaluate how polydeoxyribonucleotide (PDRN) and microcurrent therapy (MT) functioned synergistically in a cast-immobilized rabbit model with an atrophied calf muscle. Methods. At the age of 12 weeks, 32 male New Zealand rabbits were enrolled in four groups. After 2 weeks of cast-immobilization, 4 procedures were performed on atrophied calf muscle [weekly two injections normal saline 0.2 ml injection group 1 (G1-NS), weekly two injections 0.2 ml PDRN injection group 2 (G2-PDRN), MT group 3 (G3-MT), and 0.2 ml PDRN injection with MT group 4 (G4-PDRN+MT)]. For 2 weeks, MT was used for 60 minutes each day. The calf circumference (CC), the thickness of gastrocnemius muscle (TGCM), and the tibial nerve compound muscle action potential (CMAP) were evaluated using ultrasound before and after 2 weeks of treatment. Proliferating cell nuclear antigen (PCNA), vascular endothelial growth factor, and platelet endothelial cell adhesion molecule-1 (PECAM-1) of GCM fibers (type I, type II, and total) were measured. Statistical analyses were performed using ANOVA. Results. The mean atrophic alterations of right CC, CMAP, and TGCM (medial/lateral) were substantially lower in G4-PDRN+MT than in the G1-NS, G2-PDRN, and G3-MT, respectively ( $p<0.05$ ). Furthermore, mean CSAs (type I, type II, and total) of medial and lateral GCM muscle fibers in G4-PDRN+MT were significantly higher when compared to other three groups ( $p<0.05$ ). In terms of the PCNA-, VEGF-, and PECAM-1-positive cell ratio of medial and lateral GCM muscle fibers, G4-PDRN+MT was considerably higher than G1-NS, G2-PDRN, and G3-MT ( $p<0.05$ ). Conclusions. On the atrophied calf muscle of the rabbit model, PDRN injection combined with MT was more effective than PDRN injection alone, MT alone, and normal saline injection separately.

Low-intensity microcurrent therapy promotes regeneration of atrophied calf muscles in immobilized rabbits

The purpose of this study was to investigate the intensity-specific regenerative effects of microcurrent therapy on gastrocnemius muscle atrophy induced by cast-immobilization in rabbits. Fifteen rabbits were randomly allocated to 3 groups after cast removal: cast-immobilization and sham microcurrent therapy for 2 weeks (group 1); cast-immobilization and microcurrent therapy (25 μA) for 2 weeks (group 2); cast-immobilization and microcurrent therapy (5,000 μA) for 2 weeks (group 3). Clinical parameters [calf circumference, compound muscle action potential (CMAP) of the tibial nerve, thickness of gastrocnemius muscle], cross sectional area of gastrocnemius muscle fibres, and immunohistochemistry was evaluated. The clinical parameters representing mean atrophic changes in group 2 were significantly lower than those in group 3. The cross sectional area of the gastrocnemius muscle fibres and immunohistochemical parameters in group 2 were significantly greater than those in group 3. The results showed that low-intensity microcurrent therapy can more effectively promote regeneration in atrophied gastrocnemius muscle than high-intensity microcurrent therapy.

Therapeutic effect of microcurrent on calf muscle atrophy in immobilized rabbit

INTRODUCTION

Immobilization causes significant muscle loss. In this study we assessed the regenerative effect of microcurrent electrical stimulation (MES) on gastrocnemius muscle (GCM) atrophy induced by immobilization by cast (IC) in rabbits.

METHODS

Fifteen rabbits were divided into 3 groups: IC (group 1); IC and free re-ambulation for 2 weeks after cast removal (CR) (group 2); and IC and MES for 2 weeks after CR (group 3). We evaluated clinical parameters (calf circumference, compound muscle action potential of tibial nerve, and thickness of GCM by ultrasound), histomorphometric data (muscle composition and cross-sectional area), and immunohistochemistry.

RESULTS

Mean atrophic changes in clinical parameters in group 3 were significantly less than those in groups 1 and 2 (P < 0.05). Histomophometric and immunohistochemical parameters in group 3 were significantly greater than those in groups 1 and 2, respectively (P < 0.05).

DISCUSSION

MES prevents muscle atrophy and facilitates regeneration of muscle. Muscle Nerve 58: 270-276, 2018.

Recovery from immobilisation: responses of fast-twitch muscle fibres to spontaneous and intensive exercise in rat calf muscles

Four weeks of immobilisation with two types of re-mobilisation programmes (intensive concentric treadmill exercising during 6 days, and free exercising, and immobilisation without any re-mobilisation period were studied to clarify possible exercise-induced calf muscle damage especially in fast-twitch fibres used in running compared to non-immobilised rats housing freely in their cages. As markers of muscle injury, conventional histology, beta-glucuronidase (beta-GU) activity and fetal myosin heavy chain expression (MHC-d) were assessed on Days 0, 1, 3, 6 and 14 after the cast removal. Only minor focal hypercontraction, ruptures and necrosis of myofibrils, and weak inflammatory cell reactions were found in all samples examined, except in the controls. No MHC-d positive cells were found indicating absence of active regeneration after immobilisation or re-mobilisation. Minor increase in beta-GU activity was observed in all three muscles studied, but statistically significant increase was observed only in the samples of the free exercising group on Day 14 after the cast removal. To conclude, intensive concentric treadmill exercise for 6 days did not cause significantly more muscle damage than did free exercising re-mobilisation.

Evaluation of healthy and diseased muscle with magnetic resonance elastography

OBJECTIVE

To investigate whether a new tissue-imaging technique, magnetic resonance elastography (MRE), offers a viable, noninvasive way to study healthy and diseased muscle.

DESIGN

Convenience sample.

SETTING

A magnetic resonance imaging (MRI) laboratory.

PARTICIPANTS

Eight control subjects (4 men, 4 women), between the ages of 24 and 41 years, with normal neuromuscular examinations and histories, and 6 subjects (3 men, 3 women), ages 17 to 63 years, with lower-extremity neuromuscular dysfunction (1 with childhood poliomyelitis, 2 with flaccid, 3 with spastic paraplegia).

INTERVENTIONS

Subjects lay supine with their legs within the coils of a 1.5T MRI machine, with their feet strapped to a footplate positioned so that the axes of rotation of their ankles coincided with the apparatus. All subjects were tested in a no-load (0 torque) condition. Control subjects were also evaluated as they isometrically resisted ankle dorsi- (20.2Nm, 40.5Nm) and plantar- (8.2Nm, 16.4Nm) flexion moments. Subjects with neuromuscular dysfunction were evaluated in the same manner, except 1 individual with residual lower-extremity strength who could only be tested in the resting and passive ankle dorsiflexion modes. Shear waves were induced with a 150-Hz electromechanic transducer located over the belly tibialis anterior. MRE images were collected with a gradient-echo technique gated to the transducer's motion. Wave-phase propagation was visualized with 8 equally offset images across 1 vibration-cycle.

MAIN OUTCOME MEASURES

Changes in shear-wave wavelength (lambda) and muscle stiffness (as expressed by the shear modulus [G]) in the tibialis anterior and gastrocnemius muscles.

RESULTS

Wavelength and G differed between the groups in all the muscles studied, and increased as the load increased. Moreover, lambda and G in the neuromuscular disease group at rest (eg, 3.88+/-0.48cm; range, 2.87-4.91cm; 38.40+/-00.77kPa; range, 22.35-59.67kPa) and in the lateral gastrocnemius were, respectively, more than 1.5 and 2.4 times larger than they were in the same muscle in the control group (2.56+/-0.28cm, 16.16+/-00.19kPa; P=.0002) (1Pa=1N/m(2)).

CONCLUSIONS

Shear-wave wavelength and muscle stiffness increased with load in healthy muscle. In addition, at least for our sample, these quantities differed significantly between muscles with and without neuromuscular disease. In summary, MRE appears to provide in vivo physiologic information about the mechanical properties of muscle at rest and during contraction that is not otherwise available. The potential of this technique for monitoring the effects of treatment and exercise on both healthy and diseased muscle merits further research.

Heterotopic ossification in critical illness and cancer: a report of 2 cases

Heterotopic ossification is the abnormal development of bone tissue within periarticular soft tissue. We present 2 Turkish patients with malignant thoracic cancer who underwent extensive thoracic surgery and required prolonged postoperative chemical paralysis and cardiorespiratory support for respiratory complications. Both patients were found by the physiatrist to have multiple, extensive heterotopic ossifications. Clinical findings in both patients included joint swelling and severe limitation in range of motion (ROM) associated with pain. The diagnoses were confirmed radiographically. After an extended length of inpatient rehabilitation, both patients improved their cumulative FIM instrument motor scores by 23 and were discharged with a trained family member. Our findings suggested that heterotopic ossification should be suspected in patients presenting with decreased ROM, increased pain, and joint swelling after prolonged immobilization. Serum alkaline phosphatase might be used as an effective screening tool.

Muscle fiber diameter and muscle type distribution following free microvascular muscle transfers: a prospective study

The histology of free microvascular muscle flaps in 19 patients was studied prospectively. Biopsies were taken during operation, and after 2 and 6 weeks, as well as 3, 6, and 9 months, postoperatively, fixed and stained using the van Gieson method. Fiber diameters were analyzed morphometrically and fiber types defined immunohistochemically using myosin fast antibody. During the nine-month follow-up period, mean muscle fiber diameter decreased significantly (P < 0.01), type-1 fibers atrophied significantly (P < 0.05) compared to type-2 fibers, and the percentage of type-2 fibers increased from a mean of 56% intraoperatively to 73% at 9 months. Fatty change and fibrosis were already present 2 weeks after operation and increased with the duration of follow-up. The decrease in muscle fiber diameter 9 months after free flap transfer correlated with clinical factors such as the delay of reconstructive surgery, recipient site, postoperative infection, and postoperative immobilization. The present results confirm that type-specific atrophy related to denervation appears and indicates that clinical events other than denervation influence the muscle atrophy seen in human free muscle flaps. These findings focus attention on the role of muscle regeneration, reinnervation, and revascularization taking place after free flap transfer.

Abnormal mitochondria and sarcoplasmic changes in rabbit skeletal muscle induced by immobilization

Immobilization of the rabbit knee in extended position results in damage to the vastus intermedius profundus (VIP) muscle. To examine the mechanisms involved in initiation of the injury, we studied the light and electron microscopic morphology of the VIP muscle, as well as the activity and distribution of NADH tetrazolium reductase (NADH-TR) in the affected muscle, and determined serum total creatine kinase (CK) activity in immobilized rabbits. The VIP muscle of the immobilized right hindlimb was removed at various time points (10 h, 24 h, 36 h and 48-72 h, n=5 for each time point). The nonimmobilized left hindlimb and five nonimmobilized animals served as controls. No morphological changes were observed by light microscopy within 48-72 h in routine stainings. Transient ultrastructural abnormalities, including abnormal cristae, matrix lucencies and mild swelling of mitochondria, were observed between 10 h and 36 h of immobilization, subsiding by 48-72 h. On the other hand, progressive disorganization of myofibrils with breaking-up of Z-bands and an increase in the number and size of sarcoplasmic lipid vacuoles was seen with increasing duration of immobilization. NADH-TR activity at subsarcolemmal locations had decreased by 10 h and disappeared by 24 h of immobilization, while the intermyofibrillar mitochondria remained unaltered. Serum total CK activity began to increase by 2 h of immobilization and reached a peak by 24 h. The results indicate that already a few hours of immobilization of the rabbit knee in extension leads to signs of metabolic disturbance of the VIP muscle and sarcolemmal leakage. The simultaneous occurrence of transient mitochondrial abnormalities, transient CK efflux and progressive myofibrillar damage suggests the operation of multiple adverse mechanisms already at the onset of disuse muscle atrophy.

Recovery of skeletal muscle after immobilization of rabbit hindlimb. A light microscopic study

The histopathology of the deep portion of the vastus intermedius (VIP) muscle from 13 rabbit hindlimbs immobilized in shortened position for 2-2.5 (n = 4), 3 (n = 3), 14 (n = 3) and 28 (n = 3) days and VIP muscles from 13 rabbit hindlimbs immobilized for the same time periods and subsequently remobilized for 4 weeks were compared. After 3 days of immobilization the VIP muscles displayed a 15% (p < 0.004) decline in muscle fibre diameter. By 2 weeks of immobilization fatty change was prominent and muscle fibre diameters had decreased to 56% (p < 0.0001) of control values. By 4 weeks of immobilization severe fibrotic damage of myofibres was observed and fibre diameters had decreased to 47% (p < 0.0001) of control values. Three days of immobilization followed by 4 weeks of remobilization led to marked fatty change as well as an increase in connective tissue in the affected VIP muscles. The muscle fibre diameter in these muscles was 71% (p < 0.0001) compared to the VIP immobilized for 3 days and 61% (p < 0.0001) compared to the control muscles. By 2-4 weeks of immobilization the subsequent remobilization did not aggravate the initial damage. We conclude that the morphology of VIP muscle immobilized for 3 days suffers more during a subsequent remobilization period than those immobilized for 14-28 days. These findings focus attention on the mechanisms operating at the onset of disuse muscle atrophy.

Macrophages in trauma-induced myositis ossificans

The basic cellular mechanisms of different forms of myositis ossificans are poorly known. In the current experiment the nature of the early (24-168 h) inflammatory cell reaction preceding trauma-induced myositis ossificans was studied. New bone formation was induced in the vastus intermedius region of the rabbit quadriceps muscle by means of immobilization and daily passive mobilization. Before the start of treatment, a cell harvesting device (viscose cellulose sponge in a silastic tube) was implanted in the region of interest. The opposite intermedius muscle and a standardized surgical skin wound served as the control sites. The results showed a significantly prolonged invasion of macrophages into the ossifying intermedius muscle as compared with the control intermedius muscle. It is hypothesized that microinjury and subsequent muscle necrosis cause the invasion of macrophages, and these cells respond to the conditions of the traumatized muscle under passive mobilization by releasing osteogenic growth factors.