Effects of nandrolone on recovery after neurotization of chronically denervated muscle in a rat model

Follistatin Protein Enhances Satellite Cell Counts in Reinnervated Muscle

Background Muscle recovery following peripheral nerve repair is sup-optimal. Follistatin (FST), a potent muscle stimulant, enhances muscle size and satellite cell counts following reinnervation when administered as recombinant FST DNA via viral vectors. Local administration of recombinant FST protein, if effective, would be more clinically translatable but has yet to be investigated following muscle reinnervation. Objective  The aim of this study is to assess the effect of direct delivery of recombinant FST protein on muscle recovery following muscle reinnervation. Materials and Methods  In total, 72 Sprague-Dawley rats underwent temporary (3 or 6 months) denervation or sham denervation. After reinnervation, rats received FST protein (isoform FS-288) or sham treatment via a subcutaneous osmotic pump delivery system. Outcome measures included muscle force, muscle histomorphology, and FST protein quantification. Results  Follistatin treatment resulted in smaller muscles after 3 months denervation ( p  = 0.019) and reduced force after 3 months sham denervation ( p  < 0.001). Conversely, after 6 months of denervation, FST treatment trended toward increased force output ( p  = 0.066). Follistatin increased satellite cell counts after denervation ( p  < 0.001) but reduced satellite cell counts after sham denervation ( p  = 0.037). Conclusion  Follistatin had mixed effects on muscle weight and force. Direct FST protein delivery enhanced satellite cell counts following reinnervation. The positive effect on the satellite cell population is intriguing and warrants further investigation.

Satellite cell proliferation and myofiber cross-section area increase after electrical stimulation following sciatic nerve crush injury in rats

BACKGROUND

Electrical stimulation has been recommended as an effective therapy to prevent muscle atrophy after nerve injury. However, the effect of electrical stimulation on the proliferation of satellite cells in denervated muscles has not yet been fully elucidated. This study was aimed to evaluate the changes in satellite cell proliferation after electrical stimulation in nerve injury and to determine whether these changes are related to the restoration of myofiber cross-section area (CSA).

METHODS

Sciatic nerve crush injury was performed in 48 male Sprague-Dawley rats. In half (24/48) of the rats, the gastrocnemius was electrically stimulated transcutaneously on a daily basis after injury, while the other half were not stimulated. Another group of 24 male Sprague-Dawley rats were used as sham operation controls without injury or stimulation. The rats were euthanized 2, 4, and 6 weeks later. After 5-bromo-2'-deoxyuridine (BrdU) labeling, the gastrocnemia were harvested for the detection of paired box protein 7 (Pax7), BrdU, myofiber CSA, and myonuclei number per fiber. All data were analyzed using two-way analysis of variance and Bonferroni post-hoc test.

RESULTS

The percentages of Pax7-positive nuclei (10.81 ± 0.56%) and BrdU-positive nuclei (34.29 ± 3.87%) in stimulated muscles were significantly higher compared to those in non-stimulated muscles (2.58 ± 0.33% and 1.30 ± 0.09%, respectively, Bonferroni t = 15.91 and 18.14, P < 0.05). The numbers of myonuclei per fiber (2.19 ± 0.24) and myofiber CSA (1906.86 ± 116.51 μm) were also increased in the stimulated muscles (Bonferroni t = 3.57 and 2.73, P < 0.05), and both were positively correlated with the Pax7-positive satellite cell content (R = 0.52 and 0.60, P < 0.01). There was no significant difference in the ratio of myofiber CSA/myonuclei number per fiber among the three groups.

CONCLUSIONS

Our results indicate that satellite cell proliferation is promoted by electrical stimulation after nerve injury, which may be correlated with an increase in myonuclei number and myofiber CSA.

Viral vector delivery of follistatin enhances recovery of reinnervated muscle

INTRODUCTION

Poor recovery following nerve repair is due to progressive temporal loss of muscle function. Follistatin (FS), a glycoprotein with anabolic properties, may enhance muscle recovery following reinnervation.

METHODS

Seventy-two male Sprague-Dawley rats underwent temporary (3 or 6 month) denervation or sham denervation. After reinnervation, rats were administered adeno-associated viral vectors expressing FS deoxyribonucleic acid (isoform FS-317) injected into the target muscle or sham treatment. Final assessment included muscle function testing, muscle histomorphology, nerve histomorphology, and FS protein quantification.

RESULTS

FS improved muscle mass and type IIB muscle fiber size, and increased G-ratios and mean axon diameter in the 6-month temporary denervation group (P < .05). Elevated FS protein levels were detected in treated muscle (P < .05). FS increased satellite cell counts following temporary denervation and repair (P < .05).

DISCUSSION

FS treatment had anabolic, neurotrophic, and satellite cell stimulatory effects when administered following prolonged (6-month) temporary denervation and repair.

Transcutaneous carbon dioxide application with hydrogel prevents muscle atrophy in a rat sciatic nerve crush model

The acceleration of nerve regeneration remains a clinical challenge. We previously demonstrated that transcutaneous CO₂ application using a novel hydrogel increases the oxygen concentration in local tissue via an "artificial Bohr effect" with the potential to prevent muscle atrophy. In this study, we investigated the effect of transcutaneous CO₂ administration on limb function after peripheral nerve injury in a rat sciatic nerve injury model. In total, 73 Sprague-Dawley rats were divided into a sham group, a control group (crush injury to sciatic nerve and no treatment) or a CO₂ group (crush injury with transcutaneous CO₂ application). CO₂ was administered percutaneously for 20 min five times per week. Scores for the sciatic function index and pinprick test were significantly higher in the CO₂ group than control group. The muscle wet weight ratios of the tibialis anterior and soleus muscles were higher in the CO₂ group than control group. Electrophysiological examination showed that the CO₂ group had higher compound motor action potential amplitudes and shorter distal motor latency than the control group. Histological examination of the soleus muscle sections at postoperative week 2 showed shorter fiber diameter in the control group than in the CO₂ group. The mRNA expression of Atrogin-1 and MuRF-1 was lower, mRNA expression of VEGF and myogenin and MyoD was higher in CO₂ group at postoperative week 2 compared to the control group.

CLINICAL SIGNIFICANCE

Transcutaneous CO₂ application has the therapeutic potential to accelerate the recovery of muscle atrophy in peripheral nerve injury. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1653-1658, 2018.

Acute effects of nandrolone decanoate on cardiodynamic parameters in isolated rat heart

Despite worldwide use of anabolic steroids in last decades, there is still contradictory information about their acute influence on myocardium. The aim of this study was to examine the acute effects of nandrolone decanoate (ND) on cardiodynamics and coronary flow in isolated rat heart. The hearts of male Wistar albino rats (n = 48, 12 per group, age 8 weeks, body mass 180-200 g) were excised and perfused according to the Langendorff technique at gradually increased coronary perfusion pressures (40-120 cmH₂O). After the control sets of experiments, the hearts in different groups were perfused with different doses of ND (1, 10, or 100 μmol/L separately). Using a sensor placed in the left ventricle, we registered maximum and minimum rate of pressure development in the left ventricle (dP/dt_max and dP/dt_min), systolic and diastolic left ventricular pressure (SLVP and DLVP), and heart rate (HR). Coronary flow (CF) was measured flowmetrically. The results clearly show the depression in cardiac function caused by higher doses of ND. The highest concentration of ND (100 μmol/L) induced the most deleterious impact on the myocardial function and perfusion of the heart (coronary circulation), which could be of clinical significance.

Implantation of muscle satellite cells overexpressing myogenin improves denervated muscle atrophy in rats

This study evaluated the effect of muscle satellite cells (MSCs) overexpressing myogenin (MyoG) on denervated muscle atrophy. Rat MSCs were isolated and transfected with the MyoG-EGFP plasmid vector GV143. MyoG-transfected MSCs (MTMs) were transplanted into rat gastrocnemius muscles at 1 week after surgical denervation. Controls included injections of untransfected MSCs or the vehicle only. Muscles were harvested and analyzed at 2, 4, and 24 weeks post-transplantation. Immunofluorescence confirmed MyoG overexpression in MTMs. The muscle wet weight ratio was significantly reduced at 2 weeks after MTM injection (67.17±6.79) compared with muscles injected with MSCs (58.83±5.31) or the vehicle (53.00±7.67; t=2.37, P=0.04 and t=3.39, P=0.007, respectively). The muscle fiber cross-sectional area was also larger at 2 weeks after MTM injection (2.63×10³±0.39×10³) compared with MSC injection (1.99×10³±0.58×10³) or the vehicle only (1.57×10³±0.47×10³; t=2.24, P=0.049 and t=4.22, P=0.002, respectively). At 4 and 24 weeks post-injection, the muscle mass and fiber cross-sectional area were similar across all three experimental groups. Immunohistochemistry showed that the MTM group had larger MyoG-positive fibers. The MTM group (3.18±1.13) also had higher expression of MyoG mRNA than other groups (1.41±0.65 and 1.03±0.19) at 2 weeks after injection (t=2.72, P=0.04). Transplanted MTMs delayed short-term atrophy of denervated muscles. This approach can be optimized as a novel stand-alone therapy or as a bridge to surgical re-innervation of damaged muscles.