Correction of junctional epidermolysis bullosa by transplantation of genetically modified epidermal stem cells

Fulvio Mavilio¹, Graziella Pellegrini^1, 2, Stefano Ferrari², Francesca Di Nunzio¹, Enzo Di Iorio², Alessandra Recchia¹, Giulietta Maruggi¹, Giuliana Ferrari³, Elena Provasi⁴, Chiara Bonini⁴, Sergio Capurro⁵, Andrea Conti⁶, Cristina Magnoni⁶, Alberto Giannetti⁶ & Michele De Luca^1, 2

¹  Department of Biomedical Sciences, University of Modena and Reggio Emilia, Via Campi 287, 41100 Modena, Italy.

²  Epithelial Stem Cell Research Center, Veneto Eye Bank Foundation, H. SS Giovanni and Paolo, Castello 6777, 30100 Venice, Italy.

³  Istituto Scientifico H. San Raffaele-Telethon Institute for Gene Therapy (HSR-TIGET) and Vita-Salute University Istituto Scientifico H. San Raffaele, Via Olgettina 58, 20132 Milano, Italy.

⁴  Cancer Immunotherapy and Gene Therapy Program, Istituto Scientifico H. San Raffaele, Via Olgettina 58, 20132 Milano, Italy.

⁵  Division of Plastic Surgery, H. San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy.

⁶  Department of Internal Medicine, University of Modena and Reggio Emilia, Via del Pozzo 71, 41100 Modena, Italy.

The continuous renewal of human epidermis is sustained by stem cells contained in the epidermal basal layer and in hair follicles^{1, 2}. Cultured keratinocyte stem cells, known as holoclones^{3, 4, 5, 6}, generate sheets of epithelium used to restore severe skin, mucosal and corneal defects^{7, 8, 9}. Mutations in genes encoding the basement membrane component laminin 5 (LAM5) cause junctional epidermolysis bullosa (JEB), a devastating and often fatal skin adhesion disorder¹⁰. Epidermal stem cells from an adult patient affected by LAM5-3–deficient JEB were transduced with a retroviral vector expressing LAMB3 cDNA (encoding LAM5-3), and used to prepare genetically corrected cultured epidermal grafts. Nine grafts were transplanted onto surgically prepared regions of the patient's legs. Engraftment was complete after 8 d. Synthesis and proper assembly of normal levels of functional LAM5 were observed, together with the development of a firmly adherent epidermis that remained stable for the duration of the follow-up (1 year) in the absence of blisters, infections, inflammation or immune response. Retroviral integration site analysis indicated that the regenerated epidermis is maintained by a defined repertoire of transduced stem cells. These data show that ex vivo gene therapy of JEB is feasible and leads to full functional correction of the disease.

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