Advances in preparation of acellular human dermis for tissue banking and transplantation.

Non-healing wounds cost the National Health Service over £5.6 billion annually in wound management. Skin allografts are used to treat non-healing wounds, ulcers and burns, offering the best protection against infection. In order to allow host cells to repopulate and to avoid immunogenicity, cell components are removed through decellularisation. Decellularisation of human dermis has so far been performed in NHS Blood and Transplant using a combination of two enzymes (RNase T1 and the recombinant human DNase Pulmozyme)®. This study aims at validating a new method to remove DNA from donated dermis via the use of a single enzyme, Benzonase, known for its effectiveness of DNA digestion. Skin samples were decellularised by removing the epidermis, lysing of dermal cells, removal of cellular fragments by a detergent wash and removal of nucleic acids by a nuclease incubation with either Benzonase or Pulmozyme + RNase T1. DNA quantification with PicoGreen, as well as histology on wax-embedded biopsies, stained with DAPI and haemotoxylin and eosin, were performed. In vitro toxicity test on human osteosarcoma immortalised cells and skin fibroblasts, and biomechanical (tensile) testing, were also performed. The effectiveness of DNA digestion with the new methodology was comparable to previous procedure. Mean DNA removal percentage following decellularisation with Pulmozyme + RNase was 99.9% (3.83 ng/mg). Mean DNA removal percentage with Benzonase was 99.8% (9.97 ng/mg). Histology staining showed complete decellularisation following either method. Benzonase was proven to be non-toxic to both cell lines used, and a one-way Anova test showed no significant difference in neither stress nor strain between acellular dermal matrix decellularised with either Benzonase or Pulmozyme + RNase T1. Benzonase was able to effectively decellularise dermis after prior removal of epidermis. It performed just as well as the combination of Pulmozyme + RNase T1, but represents significant advantages in terms of cost effectiveness, procurement and storage; Benzonase has been successfully used in the decellularisation of other tissues, thus would be better for Tissue Banking use. Switching to this combined DNase/RNase can have far-reaching consequences in the production of acellular human dermal matrix by NHSBT and in the treatment of patients requiring it.