355 Regeneration of the Entire Human Epidermis by Transgenic Epidermal Stem Cell Transplants and its Implications for the Treatment of Burns

Abstract

We recently performed the regeneration of almost an entire human epidermis by transplantation of genetically modified epidermal stem cells in a 7-year-old patient suffering from terminal Junctional Epidermolysis Bullosa (JEB). JEB is caused by mutations of genes encoding for basement membrane components, LAMB3 in this case, leading to severe skin lesions with often lethal outcome. These defects present in a similar fashion to deep partial-thickness burns with loss of epidermis but remaining dermal wound bed. Epidermal stem cells were procured via skin biopsy and transduced using a retroviral vector expressing the full-length LAMB3 cDNA. The transduced stem cells were then cultured using a modified culture protocol providing an optimal environment for the preservation of most potent epidermal stem cells, termed holoclones. We then transplanted 0,85m2 of autologous transgenic keratinocyte cultures after our patient had lost over 80% total body surface area of its epidermis. We performed a 2-year follow-up with clonal tracing and in-depth skin structure assessment using skin biopsies and optical coherence tomography. We also tested skin physiology parameters and mechanical stress resistance. We regenerated 80% of the child’s epidermis with autologous transgenic keratinocytes. Clonal tracing demonstrated, formally for the first time in humans, that the new epidermis was sustained by a finite number of holoclones. Two years after transplant, the patient demonstrated a high quality skin enabling a full range of motion, sebum production, and partial hair growth. Transepidermal water loss and skin elasticity were comparable to healthy skin. Sebum production was intact without the need for any more ointment application one year after transplant. In this study, we show that autologous transgenic keratinocyte cultures can regenerated an entire functional epidermis on a 7-year-old child after life-threatening loss of its original epidermis. We provide evidence for a high quality functional epidermis 2 years after transplantation that is sustained by a finite number of highly regenerative stem cells. Besides providing the first potential cure for JEB, this technology may enable a novel treatment of deep partial-thickness burns that is superior to split-thickness skin grafting or transplantation of regular cultured epidermal allografts.