Background
Duchenne Muscular Dystrophy (DMD), is a progressive lethal disease, caused by X-linked mutations affecting dystrophin production in the muscle cells. Allogeneic stem cell therapies are aiming to restore dystrophin in affected muscles, however, are challenged by rejection and limited engraftment. Chimeric Cells (CC), created via ex vivofusion of donor and recipient cells, represent a promising therapy option in the field of tissue regeneration and Vascularized Composite Allotransplant (VCA), as eliminate the need of life-long immunosuppression. The aim of this study was to test the feasibility of Chimeric Cell therapy of mesenchymal stem cell (MSC) and myoblast origin through in vitro characterization of human and murine CC and through in vivo assessment of survival, engraftment and efficacy of human and murine CC in DMD mdx/scid and mdx mice models.
Methods
Twelve ex vivo fusions of allogenic human myoblasts-myoblast and myoblast-MSC were performed, using polyethylene glycol technique. CC phenotype was evaluated by flow cytometry and confocal microscopy. CC were cultured for 30 d to test proliferation capacity and myogenic differentiation was induced in specific culture conditions. To test efficacy, mdx/scid mice (n = 4) received 0.5 × 106 human myoblast/MSC and myoblast/myoblast CC, while mdx mice received 0.5 × 106 healthy snj myoblast/mdx MSC and snj myoblast/mdx myoblast CC through local injections to gastrocnemius muscle. Therapeutic effect was monitored by muscle function tests (grip strength and wire hanging). Muscle characteristics (weight, inflammation, fibrosis, dystrophin expression as well as in situ contraction ability) were assessed at day 7, 30 and 90 after transplant.
Results
After successful fusion procedure, CC expressed antigens of both parent cells, maintained proliferative capacity in long-term cultures and differentiated toward mature skeletal myocytes. Human CC treated recipients showed CC engraftment in gastrocnemius muscle and locally increased dystrophin expression (12%), at 7 day after cell delivery. Both human and murine CC recipients showed increased motor function and dystrophin expression that was maintained through the 1 to 3-months follow-up period.
Conclusion
This study confirmed feasibility and efficacy of CC therapy, which may represent a novel, universal approach for treatment of muscular dystrophies and can be applicable to restore muscle components of VCA.