In vivo evaluation of wound bed reaction and graft performance after cold skin graft storage: new targets for skin tissue engineering.

Surplus harvested skin grafts are routinely stored at 4 to 6°C in saline for several days in plastic surgery. The purpose of this study was to evaluate the influence of storage on human skin graft performance in an in vivo intravital microscopic setting after transplantation. Freshly harvested human full-thickness skin grafts and split-thickness skin grafts (STSGs) after storage of 0, 3, or 7 days in moist saline at 4 to 6°C were transplanted into the modified dorsal skinfold chamber, and intravital microscopy was performed to evaluate vessel morphology and angiogenic change of the wound bed. The chamber tissue was harvested 10 days after transplantation for evaluation of tissue integrity and inflammation (hematoxylin and eosin) as well as for immunohistochemistry (human CD31, murine CD31, Ki67, Tdt-mediated dUTP-biotin nick-end labelling). Intravital microscopy results showed no differences in the host angiogenic response between fresh and preserved grafts. However, STSGs and full-thickness skin grafts exhibited a trend toward different timing and strength in capillary widening and capillary bud formation. Preservation had no influence on graft quality before transplantation, but fresh STSGs showed better quality 10 days after transplantation than 7-day preserved grafts. Proliferation and apoptosis as well as host capillary in-growth and graft capillary degeneration were equal in all groups. These results indicate that cells may activate protective mechanisms under cold conditions, allowing them to maintain function and morphology. However, rewarming may disclose underlying tissue damage. These findings could be translated to a new approach for the design of full-thickness skin substitutes.

Practice of split-thickness skin graft storage and histological assessment of tissue quality.

Storage of split-thickness skin grafts (STSGs) represents a standard procedure in burn surgery. The purpose of this study was to evaluate clinical routine of STSG preservation. Further, we aimed at investigating the effect of storage on tissue integrity and cell viability, proliferation, apoptosis and vascularization. A survey was performed among plastic surgery centres in Europe. STSGs were harvested from healthy patients and analysed by histology (HE, Verhoeff's, Masson's Trichrome, Sirius Red) and immunohistochemistry (Ki67, TUNEL, CD31). Cell viability was determined by MTT assay. The survey revealed that storage of STSGs up to 10 days is common practice. STSGs mostly were stored at 4 °C in saline-moisturized gauze. Histology showed no disintegration of the tissue or a decrease of collagen and elastic fibres. Proliferation increased to 22.5% of total cells after 3 days. On day 7 of STSG storage apoptotic cells amounted for 25% of total cells. Cell viability decreased by 50% after day 3 of storage. Even though reportedly superior methods for skin grafts storage exist, most study participants applied the simplest method of storage. Our data underscore this practice. However, a reduced cell viability after 3 days of storage may have an influence on graft healing.