Optimization of an ex-vivo human skin/vein model for long-term wound healing studies. Ground preparatory activities for the ‘Suture in Space’ experiment on-board the International Space Station

This study is preliminary to an experiment to be performed on board the International Space Station (ISS) and on Earth to investigate how low gravity influences healing of sutured human skin and vein wounds. Its objective was to ascertain whether these tissue explants could be maintained viable ex vivo for long time, mimicking the experimental conditions onboard the ISS. We developed an automated tissue culture chamber reproducing and monitoring the physiolog-ical tensile forces upon time and a culture medium enriched with serelaxin (60 ng/ml) and [Zn(PipNONO)Cl] (28 ng/ml), known to extend viability of explanted organs for transplantation. The results show that the human skin and vein specimens remain viable for more than 4 weeks with no substantial signs of damage in the composing tissues and cells. As a further clue of cell viability, some typical events of wound repair were observed in the tissue areas close to the wound, namely remodeling of collagen fibers in the papillary dermis and of elastic fibers in the vein wall, proliferation of keratinocyte stem cells, and expression of the endothelial functional markers eNOS and FGF-2. These findings validate the suitability of this new ex vivo organ cul-ture system for wound healing studies, not only for the scheduled space experiment but also for applications on Earth, such as drug discovery purposes