Molecular Imaging to Target Transplanted Muscle Progenitor Cells

Abstract

Duchenne muscular dystrophy (DMD) is a severe genetic neuromuscular disorder that affects 1 in 3,500 boys, and is characterized by progressive muscle degeneration. In patients, the ability of resident muscle satellite cells (SCs) to regenerate damaged myofibers becomes increasingly inefficient. Therefore, transplantation of muscle progenitor cells (MPCs)/myoblasts from healthy subjects is a promising therapeutic approach to DMD. A major limitation to the use of stem cell therapy, however, is a lack of reliable imaging technologies for long-term monitoring of implanted cells, and for evaluating its effectiveness. Here, we describe a non-invasive, real-time approach to evaluate the success of myoblast transplantation. This method takes advantage of a unified fusion reporter gene composed of genes (firefly luciferase [fluc], monomeric red fluorescent protein [mrfp] and sr39 thymidine kinase [sr39tk]) whose expression can be imaged with different imaging modalities. A variety of imaging modalities, including positron emission tomography (PET), single-photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), optical imaging, and high frequency 3D-ultrasound are now available, each with unique advantages and limitations. Bioluminescence imaging (BLI) studies, for example, have the advantage of being relatively low cost and high-throughput. It is for this reason that, in this study, we make use of the firefly luciferase (fluc) reporter gene sequence contained within the fusion gene and bioluminescence imaging (BLI) for the short-term localization of viable C2C12 myoblasts following implantation into a mouse model of DMD (muscular dystrophy on the X chromosome [mdx] mouse). Importantly, BLI provides us with a means to examine the kinetics of labeled MPCs post-implantation, and will be useful to track cells repeatedly over time and following migration. Our reporter gene approach further allows us to merge multiple imaging modalities in a single living subject; given the tomographic nature, fine spatial resolution and ability to scale up to larger animals and humans, PET will form the basis of future work that we suggest may facilitate rapid translation of methods developed in cells to preclinical models and to clinical applications.

Imaging of tumor clones with differential liver colonization

“…An increasing number of studies have demonstrated the optical imaging as a modality for preclinical in vivo examination of tumor detection, growth, and response to different treatments 26 27 28 29 30 . Because of its efficiency, the clinical potential for the in vivo optical imaging is becoming apparent 31 32 .…”

A real-time monitoring platform of myogenesis regulators using double fluorescent labeling

“…These tools include assessment of physical properties and function such as contractility through displacement analysis [ 36 ], skeletal muscle thickness [ 45 , 46 ] and myoblast differentiation [ 46 ] through electrical impedance. Additionally, multiple imaging modalities have been applied to assess muscle biology, including bioluminescence imaging for luciferase tagged cell transplantation [ 47 ], second harmonic generation (SHG) imaging to quantify muscle striation patterns [ 48 , 49 ], MRI to assess oxidative phosphorylation in muscle [ 50 ], and multi-photon imaging for the assessment of myoblast oxidation level [ 51 ].…”

Treatment of Stress Urinary Incontinence with Muscle Stem Cells and Stem Cell Components: Chances, Challenges and Future Prospects

“…No evidence of phagocytosis of labelled cells by macrophages was documented after 1 year. Others have used unified fusion reporter genes, whose expression can be monitored with bioluminescence imaging, for the localization of viable MPCs following implantation into a mouse model [ 108 ]. An advantage of this approach is the possibility to merge multiple imaging modalities.…”