MP12-19 NON-INVASIVE TRACKING OF MUSCLE PRECURSOR CELLS FOR SPHINCTER MUSCLE ENGINEERING

Abstract

INTRODUCTION AND OBJECTIVES: Regenerative medicine using autologous stem cells offers an alternative therapy for skeletal muscle diseases, including stress urinary incontinence. To better understand the engrafting of the injected cells novel imaging technologies are needed. In this study we investigated the possibility of using a mutated dopamine D2-receptor and PET Imaging for precise localization and long-term in vivo tracking of the implanted muscle precursor cells. METHODS: Human muscle precursor cells (hMPCs) were isolated from biopsies of the M. rectus abdominis and expanded in culture. We have genetically modified these cells to express a mutated dopamine-D2R, as tracers for D2R imaging are already used in clinics. The infected hMPCs were characterized via immunocytochemistry and FACS using muscle-specific markers (MyHC, Pax7, Desmin, a-actinin). The modified cells were visualized with Positron emission tomography (PET) in vitro. For the in vivo evaluation 30 million hMPCs expanded under growth conditions were infected with Ad-D2R, suspended in collagen type I (1mg/ml) and injected subcutaneously (8 weeks old, female nude mice). After 2 and 4 weeks the newly-formed muscle tissues were visualized by PET and harvested for autoradiography and histological analysis. Furthermore, histomorphometry of the isolated newly-formed muscle tissues was performed to access their functionality. RESULTS: The successful transduction of hMPCs allowed precise detection by PET Imaging in vitro. Further characterizations of their morphology after harvesting revealed no differences to non-transduced cells. These results confirm that using genetically modified hMPCs does not alter the muscle phenotype or contractility. The usage of PET imaging of our engineered muscle engrafts allows cell tracking after transplantation and non-invasively provides us with additional insights regarding their survival in vivo (via dopamine D2 receptor (DRD2) labeled hMPCs). Autoradiography also confirmed the presence of the transduced cells in the engineered tissue. CONCLUSIONS: The combination of a mutated D2-receptor and PET Imaging may offer a novel method for non-invasive visualization and detection of stem cells after injection for treatment of muscle diseases.