Zebrafish Assays for Identifying Potential Muscular Dystrophy Drug Candidates - Zebrafish: Methods for Assessing Drug Safety and Toxicity - page 230

than normal myotubes. Efficacy of deacetylase inhibitors, including trichostatin A
(TSA) and MS27 (a selective inhibitor of class I deacetylases), injected daily
intraperitoneally has been assessed in 3-month-old dystrophin-deficient ( mdx ) mice
(Minetti et al., 2006). These drugs increased skeletal muscle size and mitigated
morphological and pathological consequences of the primary genetic defects. A
beneficial effect on muscle repair has been reported after administering nitric oxide
(NO) using a NO-releasing derivative of flurbiprofen (HCT1026), a nonsteroidal anti-
inflammatory drug (Minetti et al., 2006). Proteasome inhibitors MG-132, Velcade
(bortezomib or PS-341), and MLN273 (PS-273) have been shown to restore both
dystrophin and dystrophin-associated protein expression (Bonuccelli et al., 2003,
2007; Assereto et al., 2006). Humans with myotonic dystrophy and mice expressing
the muscular dystrophy gene exhibited free radical overload and oxidative stress. In
mdx mice, epigallocatechin-3-gallate, an antioxidant component of green tea, has
been shown to delay MD onset (Nakae et al., 2008) and N -acetylcysteine, another
antioxidant, protects against dystrophic muscle damage (Whitehead et al., 2008),
increased b-dystroglycan and utrophin expression, and decreased expression of NF-
kB, the pro-inflammatory cytokine. Although effective therapies for muscular
dystrophies are still lacking, several novel strategies are under investigation, includ-
ing gene and cell therapies briefly described below.
18.1.5.1 Gene Therapy Intramuscular injection of g-sarcoglycan-expressing
adeno-associated viral (AAV) vectors is under investigation for limb-girdle muscular
dystrophy. For dystrophin, two strategies are currently undergoing testing inmammals:
exon skipping and dystrophin variant expression using AAV vectors. Despite minor
efficacy, in addition to viral vectors, nonviral delivery is also undergoing clinical
experimentation and direct intramuscular injection of plasmids expressing human
dystrophin resulted in protein expression at the site of injection (Romero et al., 2004).
18.1.5.2 Cell Therapy Strategies to replace affected cells (Cossu and
Sampaolesi, 2007), including pioneering experiments in mouse DMD models,
demonstrated that myoblasts transplanted into dystrophic muscle generated
dystrophin-expressing myofibers (Partridge et al., 1989; Skuk et al., 2004, 2006).
Several adult-derived stem cells have been isolated, including bone marrow-derived
stem cells, blood- and muscle-derived CD133 þ cells, muscle-derived stem cells
(MDSCs), side population (SP) cells, and mesoangioblasts (Gussoni et al., 1999;
Jiang et al., 2002; Minasi et al., 2002; Torrente et al., 2004; Dezawa et al., 2005;
Dellavalle et al., 2007).
18.2 MATERIALS AND METHODS
18.2.1 Compounds and Reagents
Unless specifically described, compounds and reagents were purchased from Sigma
(St. Louis, MO).