Rehabilitation intervention prior to cell transplantation therapy for Duchenne muscular dystrophy improves engraftment efficiency of transplanted cells

We aimed to improve the therapeutic effect by combining cell transplantation and exercise therapy to adapt the environment of the host muscle to that suitable for engraftment of the transplanted cells. Isometric muscle contraction training (Tr) with transcutaneous electrical stimulation was used as the exercise therapy.

The objectives of this study were twofold: 1) to optimize the Tr conditions to improve the engraftment efficiency of transplanted cells, and 2) to elucidate the molecular biological mechanism by which Tr improves the engraftment efficiency of transplanted cells.

1) The timing and amount of Tr loading was examined in 5-week-old DMD mice.

2) Proteome analysis was performed on 4 groups (5-week-old DMD mice and WT mice at steady state, and DMD mice and WT mice 24 h after Tr loading) (n=3 per group). Enrichment and network analyses were then performed to select candidate molecules that contribute to the improved cell engraftment rate induced by Tr. We also performed validation of the candidate molecules.

1) Tr-loading of DMD mice with 50 repetitions at 40% of maximal muscle contractility 24 hours prior to cell transplantation significantly increased the engraftment efficiency of transplanted cells and maximized the number of Dys-positive fibers.

2) The population involved in cell adhesion was identified as a group of proteins that were significantly more abundant in DMD than in WT by Tr loading alone. Network analysis of this population identified two molecules, Factor-X and Factor-Y, as highly centrally mediated molecules. Validation of Factor-X showed that increased expression of Factor-X prior to cell transplantation tended to increase the number of dystrophin-positive fibers. 

1) Optimization of Tr conditions prior to cell transplantation maximized the engraftment efficiency of transplanted cells.

2) Optimized Tr loading on DMD may have improved the cell engraftment rate of transplanted cells by mobilizing a group of proteins related to cell adhesion, mainly Factor-X.

Through this study, we will be able to establish a theoretical basis to explain the effect of Tr on improving the engraftment rate of transplanted cells at the molecular level. This will allow us to show that rehabilitation intervention prior to cell transplantation therapy for DMD can further improve the efficacy and safety of cell transplantation therapy.