Institutes
Cell therapy for myopathies
Duchenne Muscular Dystrophy (DMD) is due to mutations that disrupt the reading frame of the large, X-linked dystrophin gene and result in the absence of the cytoskeletal protein that stabilizes muscle fiber membrane. In DMD, fibers undergo damage during contraction and are initially repaired by resident satellite cells, which however are soon exhausted so that muscle is progressively replaced by adipose and connective tissue. DMD currently lacks an efficacious therapy. We carried out 15 years of pre-clinical work in three mouse and one dog model (8,10-11), that showed safety and efficacy of this protocol. Thus we completed a first in man trial (5) based upon repeated intra-arterial administrations of HLA-matched donor mesoangioblasts in five DMD patients. Mesoangioblasts are perivascular myogenic progenitors (9) that, at variance with satellite cells, are able to cross the vessel wall and thus can be delivered systemically through the arterial tree to reach downstream muscles. The trial showed safety but minimal efficacy, though we detected donor derived dystrophin in the muscles of the youngest patient.
Research activity
1.We developed a new strategy of genetic correction that compensates the invariably low engraftment of donor cells in skeletal muscle (4), essentially cell-mediated exon skipping. DMD mesoangioblasts are transduced with a lentivector expressing a snRNA engineered to skip exon 51. Since the snRNA is produced by a donor nucleus enters all the neighboring nuclei, this mechanism amplifies 5/10 folds the production of dystrophin both in vitro and in vivo (Galli et al Under revision)
2. We are testing safety of genetically corrected (with the strategy described above) autologous mesoangioblasts by intramuscular injection in a foot muscle of 5 non-ambulant DMD patients.
3. Even if successful, this personalized approach would prove prohibitively expensive for healthcare systems (15). We succeeded in indefinitely expanding human mesoangioblasts , thus allowing gene editing in vitro. Cells are first genome edited to delete β2 microglobulin and Class II Common Trans-Activator, then transduced with a lenti vector expressing tolerogenic molecules, and finally tested for immune escape in vivo. This work will establish pre-clinical safety and efficacy for an off the shelf, affordable product, that may give rise to a universal donor mesoangioblast cell bank.
