It would be great if someone on this forum has access to the full text study below and could post it, I would love to see the details:
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Main Article
Myostatin DNA vaccine increases skeletal muscle mass and endurance in mice
Liang Tang, MD 1 2, Zhen Yan, MD 1, Yi Wan, MSc 1, Wei Han, MD 1, Yingqi Zhang, MD 1 *
1Biotechnology Center, Fourth Military Medical University, 17 Changle West Road, 710032 Xi'an, China
2Institute of Sports Biology, Shaanxi Normal University, Xi'an, China
email: Yingqi Zhang (
[email protected])
*Correspondence to Yingqi Zhang, Biotechnology Center, Fourth Military Medical University, 17 Changle West Road, 710032 Xi'an, China
Funded by:
Changjiang Scholars and Innovative Research Team in University (PCSIRT), China
Faculty of Pathology, Fourth Military Medical University, China
Keywords
autoimmunity • DNA vaccine • myostatin • T-helper epitope
Abstract
Myostatin is a transforming growth factor- family member that acts as a negative regulator of skeletal muscle growth. In mice, genetic disruption of the myostatin gene leads to a marked increase in body weight and muscle mass. Similarly, pharmacological interference with myostatin in vivo in mdx knockout mice results in a functional improvement of the dystrophic phenotype. Consequently, myostatin is an important therapeutic target for treatment of diseases associated with muscle wasting. To construct a therapeutic DNA vaccine against myostatin, we coupled the foreign, immunodominant T-helper epitope of tetanus toxin to the N terminus of myostatin, and BALB/c mice were immunized with the recombinant vector. Sera from vaccinated mice showed the presence of specific antibodies against the recombinant protein. In addition, body weight, muscle mass, and grip endurance of vaccinated mice were significantly increased. Our study provides a novel, pharmacological strategy for treatment of diseases associated with muscle wasting. Muscle Nerve, 2007
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Accepted: 28 March 2007
Digital Object Identifier (DOI)
10.1002/mus.20791 About DOI
Article Text
Myostatin, formerly known as growth and differentiation factor-8 (GDF-8), is a member of the transforming growth factor-beta family that plays an essential role in regulating skeletal muscle growth.[1][11][15] Myostatin is a negative regulator of skeletal muscle mass and its sequence has been highly conserved through evolution.[16] Mutations in the myostatin gene lead to dramatic increases in skeletal muscle mass and muscle strength in mice and to less fat accumulation than in wild- type littermates.[6][8][9][22] In humans, mutations in the myostatin gene are correlated with excess muscle mass, whereas expression of myostatin is increased in the setting of muscle loss, including chronic illnesses, infection with human immuodeficiency virus, and during aging.[5][7][20] Systematic administration of exogenous myostatin to adult mice is sufficient to induce severe muscle and fat loss, similar to human cachexia syndromes.[26] Conversely, myostatin antagonists, such as monoclonal antibodies specific to myostatin and follistatin, as well as activin type II receptor antagonists, can significantly increase skeletal muscle mass. Given the highly conserved role of myostatin among animals, improved methods for inhibiting myostatin activity could have important implications not only for human therapeutics, but also other areas such as agriculture.[10]
Although myostatin antagonists are obvious candidates for intervention, obtaining sufficient quantities of purified myostatin antagonist proteins can be costly and time-consuming. By contrast, DNA vaccines are stable, inexpensive, safe, and easy to produce in large quantities and have high levels of purity.[2][4][13][21] Moreover, DNA vaccines stimulate a full spectrum of immune responses, including cytotoxic T lymphocytes generally not induced by protein vaccines, and generate exceptionally long-lasting immune responses.[3][24]
We describe the development of a myostatin-specific DNA vaccine. The pVAC1-cms plasmid is a DNA vaccine vector specifically designed to stimulate a humoral immune response, using the rhesus monkey elongation factor 1-alpha gene promoter to achieve high levels of expression in skeletal muscle cells and antigen-presenting cells. Expression levels are further increased by the addition of the SV40 enhancer, which heightens the ability of the plasmid to be transported into the nucleus. DNA encoding a fusion protein between the T-helper epitope of tetanus toxin (TT) and the mature myostatin peptide was cloned into pVAC1-cms vector (pVAC-TTMs). The immunogenicity of the recombinant DNA vaccine was examined in BALB/c mice. Sera were analyzed from vaccinated mice containing specific antibodies to the recombinant protein. The muscle and function of the mice were evaluated as well.
MATERIALS AND METHODS
A DNA fragment encoding the TT epitope (QYIKANSKFIGITEL),[12] followed by the N terminus of mature myostatin (encoding amino acid residues 267-375, GenBank Accession No. 014793), was synthesized by Shenggong Biotechnology (Shanghai, China). This fragment was subcloned into the EcoRI and BamHI sites of pVAC1-cms (Invitrogen, Carlsbad, California). The recombinant plasmid (pVAC-TTMs) was confirmed by sequencing.
Plasmid pVAC1-cms and pVAC-TTMs were transformed into expression-competent Escherichia coli harboring the DH5 lysogen by heat shock. The transformation mixture (10 l) was added to Luria-Bertani (LB) medium (10 ml) containing 100 g/ml zeocin (Invitrogen) and incubated overnight at 37°C with vigorous shaking. This culture was used to inoculate 200 ml of prewarmed LB medium containing 100 g/ml zeocin for 24 h at 37°C. Cells were harvested by centrifugation at 5000 × g for 20 min and the plasmids were extracted and purified as described elsewhere.[20]
Male BALB/c mice (2-3 weeks old) were purchased from the National Rodent Laboratory Animal Resource (Shanghai, China) and housed in a room controlled for temperature (22 ± 2°C) and humidity (60 ± 5%) and regulated to provide alternating 12-h periods of light and darkness. Mice were allocated to two groups (n = 6 for each group) and injected intramuscularly (IM) with 50 g each of pVAC1-cms or pVAC-TTMs. Mice were vaccinated on days 0, 14, and 28, then boosted (IM) on day 42, and killed on day 67 for serum and tissue analysis. Serum total protein, albumin, globulin, urea nitrogen, glucose, cholesterol, triglycerides, creatine kinase, and antibody titer were analyzed. At the same time, the hindlimb was photographed. The abdominal fat pad, a portion of the quadriceps (rectus femoris), and the gastrocnemius were dissected and weighed.
Detection of Expression of Plasmid-Encoded TT-Ms in Mice by Western Blot.
Tissues kept at -80°C from quadriceps muscle of different groups were homogenized in 10-20 vol of a buffer containing 1% sodium dodecylsulfate, 100 mM Tris-HCl (pH 6.8), 1 mM phenylmethylsulfonylfluoride, and 0.1 mM -mercaptoethanol. The supernatant obtained after centrifugation of homogenized tissue at 15,000 × g for 25 min (4°C) was designated the homogenate, and the same amounts of supernatant quadriceps muscle (20 l) from the mice vaccinated with pVAC-TTMs and pVAC1-cms and purified B7H1 (control protein from our laboratory) were loaded for sodium dodecylsulfate-polyacrylamide gel electrophoresis (15% acrylamide). The proteins were then electrophoretically transferred (80 V, 2 h) onto nitrocellulose (NC) membranes (Bio-Rad Instruments, Hercules, California). The NC membranes were blocked using phosphate-buffered saline (PBS) containing 2% bovine serum albumin (BSA) and 0.05% Tween-20 (PBST) at 4°C overnight. The NC membranes were then incubated with either anti-TT antibody at 1:500 dilution (Abcam, Cambridge, Massachusetts) or anti-GDF-8 antibody at 1:250 dilution (Bethyl, Montgomery, Texas) for 2 h at room temperature. Membranes were washed three times for 10 min in PBST and incubated with alkaline phosphatase-conjugated goat anti-mouse IgG (Life Technologies, Carlsbad, California) at 1:1000 dilution and goat anti-rabbit IgG (Life Technologies) at 1:1000 dilution in 2% BSA-PBST for 2 h at room temperature. Finally, the membranes were washed as described previously, and developed by adding 10 ml of alkaline phosphatase developer (Life Technologies). The reaction was stopped by rinsing the NC membranes with de-ionized water.
Enzyme-Linked Immunosorbent Assay.
Enzyme-linked immunoassay (ELISA) plates were coated with 100 ng of purified myostatin protein and incubated overnight at 4°C. The plates were washed three times with PBS containing 5% Tween-20. Serially diluted mouse sera (100 l) were added to each well and assayed in duplicate after blocking as described earlier, and then incubated for 1 h at 37°C. After washing, horseradish peroxidase-conjugated goat anti-mouse IgG (diluted 1:1000) was added to each well (100 l per well) and incubated for 1 h at 37°C. The reactions were then visualized with o-phenylenediamine dihydrochloride and H2O2 and stopped by adding 100 l of 2 M H2SO4. The plates were read at OD450 using a Bio-Rad ELISA reader.
Competitive Inhibition Assay.
Ninety-six-well plates were coated with 100 ng of purified myostatin protein and incubated overnight at 4°C. Plates were then washed three times with PBS containing 5% Tween-20 and blocked with BSA for 30 min at 37°C. Anti-GDF-8 polyclonal antibody (100 ng/well) was preincubated with serially diluted sera from mice treated with pVAC-TTMs, pVAC1-cms (negative control), or B7H1 (control antiserum from our laboratory) protein for 30 min at 37°C before addition to myostatin-coated wells. After washing, bound GDF-8 antibody was detected by incubation with horseradish peroxidase-conjugated secondary antibody. The reactions were visualized as described earlier. Inhibition rate was defined as 1 - OD490 (pVAC-TTMs) / OD490 (pVAC1-cms) 100%.
Grip Test.
Grip tests were conducted as described by Peled-Kamar et al,[18] with some modifications. Mice were allowed to grip and hang from a 2-mm horizontal tight-rope, 80 cm above the ground, but the measurement of grip time was different from the method of Peled-Kamar et al. The tails of mice were immobilized when the forelimbs of the mice gripped the rope. The time that elapsed until the forelimbs loosened and the mice fell to the ground was measured. The mice were studied three times each on two different days, and measurements were averaged.
Morphometric Analysis.
The gastrocnemius muscles were dissected rapidly and freed of fat and connective tissue. Muscle tissues were weighed and fixed with 4% polyaldehyde for 24 h. Serial 8-10-m transverse sections, made with a cryostat, were mounted on silanized slides (Dako, Tokyo, Japan). Cross-sectional areas were measured at quadricep midportions following staining with hematoxylin-eosin.
Statistical Analysis.
Statistical analysis of the data was performed with the Student's unpaired t-test. Results are expressed as the mean ± SD. Differences were considered statistically significant at P < 0.05.