Objective: Although several in vitro studies have demonstrated active release of DNA by living cells, there is still doubt. There are no such in vivo studies (1). The following experiment is an in vivo study to determine whether DNA release and uptake by cells and tissues occur and can be related to normal growth and differentiation, abnormal growth and cancer.
Methods: Epidermal and full-thickness ear-skin grafts were separately autotransplanted into two groups of mice. In a second group, host mice were labelled with tritiated thymidine and autografted separately, with unlabelled epidermal and full-thickness ear skin grafts. Animals were sacrificed regularly in both cases.
Results: Full thickness grafts revealed cysts in 15 out of 16 grafts, with well-differentiated squamous epidermis, DNA labelling of dermal fibrolasts, and no DNA labelling of epidermal cells. Epidermal grafts revealed cysts in six out of 20 grafts, with epidermal cells variable in shape and arrangement; some appeared normal but others were two to four times larger, forming solid nests of cells. In some grafts, there were spindle-shaped pleomorphic cells loosely interconnected. DNA labelling was observed in occasional epidermal cell. Two lung adenocarcinomas were found.
Conclusion: These results suggest active release of DNA by host cells and DNA uptake by grafted cells. This phenomenon and the differential uptake of DNA labelling of epidermal and dermal cells in the epidermal and full-thickness grafts suggest an association with abnormal, even pleomorphic epidermal cell behaviour due to the interference of dermal/epidermal interacting factors.