Fractional transepidermal delivery: a histological analysis

Background: In autologous cell therapy, e.g. in melanocyte transplantation for vitiligo, a minimally invasive mode of transepidermal delivery of the isolated cells is of crucial importance to reduce potential side effects such as infections and scarring as well as to minimize the duration of sick leave.

Objectives: To compare the characteristics of the microscopic treatment zones induced by ablative fractional CO(2) laser and by microneedle treatment in ex vivo human breast skin.

Results: Ablative fractional CO(2) laser treatment resulted in superficial, mainly epidermal defects reaching at most the upper papillary dermis (0.1-0.3 mm), covered by a thin eschar and coated by a small zone of collagen denaturation. Tissue injury characteristics depended on spot size as well as the energy delivered. Microneedle treatment led to thin vertical skin fissures, reaching the middermis (up to 0.5 mm) and injuring dermal blood vessels, but without surrounding tissue necrosis.

Conclusions: Both technologies are able to create small epidermal defects which allow to deliver isolated cells such as melanocytes to an epidermodermal site, with microneedle treatment having the advantage of lacking devitalized tissue and eventually enabling vascular access for the transplanted cells.