P.20.10 Human adipose mesenchymal stem-cells injections in golden retriever muscular dystrophy (GRMD) dogs: a four-year follow-up

Abstract

The possibility to treat Duchenne dystrophy (DMD) through cell therapy has been widely investigated but before starting clinical trials in humans many questions still need to be addressed in pre-clinical studies. In addition to clarifying the role of the exogenous cells in dystrophic muscle, one important concern is whether there is an increased risk of tumors or any other long-term side effects following stem-cells injections. Since murine models have a short life span, the best animal model to address these questions is the Golden Retriever Muscular Dystrophy (GRMD) dog, which reproduces the full spectrum of human DMD. They present clinical signs within the first weeks of life and most of them do not survive beyond age two. However, due to their phenotype variability each dog must be compared separately before and after any experiment. We have injected human adipose-derived mesenchymal stromal cells (hAMSCs), from two different donors, in three GRMD dogs, without immunosuppression. They were injected in the cephalic vein with 5 × 107 cells/kg within their first year of life: weekly in the first month of injections and then monthly. Dolar and Yuan were born in September of 2008 and Rum in July of 2011. In Dolar and Yuan, who received cells from donor 1, we observed that hAMSCs injected systemically were able to reach and express human dystrophin in the host GRMD dystrophic muscle up to 6 months after transplantation. When cells from donor 2 were injected in Rum, no human dystrophin was found in the host muscle. However, the three dogs showed clinical improvement following hAMSCS injections with an apparent stabilization afterwards, suggesting a beneficial effect from factors released by the injected cells. Most importantly, after almost four years of follow-up for Dolar and Yuan there was no tumor or other side effect suggesting that hAMSCS transplantation is a safe procedure, which may have important applications for future therapy in muscular dystrophy patients. The possibility to treat Duchenne dystrophy (DMD) through cell therapy has been widely investigated but before starting clinical trials in humans many questions still need to be addressed in pre-clinical studies. In addition to clarifying the role of the exogenous cells in dystrophic muscle, one important concern is whether there is an increased risk of tumors or any other long-term side effects following stem-cells injections. Since murine models have a short life span, the best animal model to address these questions is the Golden Retriever Muscular Dystrophy (GRMD) dog, which reproduces the full spectrum of human DMD. They present clinical signs within the first weeks of life and most of them do not survive beyond age two. However, due to their phenotype variability each dog must be compared separately before and after any experiment. We have injected human adipose-derived mesenchymal stromal cells (hAMSCs), from two different donors, in three GRMD dogs, without immunosuppression. They were injected in the cephalic vein with 5 × 107 cells/kg within their first year of life: weekly in the first month of injections and then monthly. Dolar and Yuan were born in September of 2008 and Rum in July of 2011. In Dolar and Yuan, who received cells from donor 1, we observed that hAMSCs injected systemically were able to reach and express human dystrophin in the host GRMD dystrophic muscle up to 6 months after transplantation. When cells from donor 2 were injected in Rum, no human dystrophin was found in the host muscle. However, the three dogs showed clinical improvement following hAMSCS injections with an apparent stabilization afterwards, suggesting a beneficial effect from factors released by the injected cells. Most importantly, after almost four years of follow-up for Dolar and Yuan there was no tumor or other side effect suggesting that hAMSCS transplantation is a safe procedure, which may have important applications for future therapy in muscular dystrophy patients.