Duchenne muscular dystrophy (DMD) is a genetic disorder associated with a progressive deficiency of dystrophin that leads to skeletal muscle degeneration. In this study, we tested the hypothesis that a co-transplantation of two stem/progenitor cell populations, namely bone marrow-derived mesenchymal stem cells (BM-MSCs) and skeletal muscle-derived stem/progenitor cells (SM-SPCs), directly into the dystrophic muscle can improve the skeletal muscle function of DMD patients. Three patients diagnosed with DMD, confirmed by the dystrophin gene mutation, were enrolled into a study approved by the local Bioethics Committee (no. 79/2015). Stem/progenitor cells collected from bone marrow and skeletal muscles of related healthy donors, based on HLA matched antigens, were expanded in a closed MC3 cell culture system. A simultaneous co‑transplantation of BM-MSCs and SM-SPCs was performed directly into the biceps brachii (two patients) and gastrocnemius (one patient). During a six‑month follow‑up, the patients were examined with electromyography (EMG) and monitored for blood kinase creatine level. Muscle biopsies were examined with histology and assessed for dystrophin at the mRNA and protein level. A panel of 27 cytokines was analysed with multiplex ELISA. We did not observe any adverse effects after the intramuscular administration of cells. The efficacy of BM‑MSC and SM‑SPC application was confirmed through an EMG assessment by an increase in motor unit parameters, especially in terms of duration, amplitude range, area, and size index. The beneficial effect of cellular therapy was confirmed by a decrease in creatine kinase levels and a normalised profile of pro-inflammatory cytokines. BM-MSCs may support the pro-regenerative potential of SM-SPCs thanks to their trophic, paracrine, and immunomodulatory activity. Both applied cell populations may fuse with degenerating skeletal muscle fibres in situ, facilitating skeletal muscle recovery. However, further studies are required to optimise the dose and timing of stem/progenitor cell delivery.
Keywords: Duchenne muscular dystrophy (DMD); cellular therapy of DMD; co-transplantation; mesenchymal stem cells (MSCs); skeletal muscle stem/progenitor cells (SM-SPCs).