Tracking and increasing viability of topically injected fibroblasts suspended in hyaluronic acid filler

Anewinjectable tissue-engineered soft tissue consisting of amixtureof hyaluronic acid(HA)fillerand culturedhuman fibroblasts have been developed by the authors. To establish this method as a standard treatment, a further study was required to determine whether the injected fibroblasts could stay at the injected place ormove to other sites. In addition, effective strategies were needed to increase viability of the injected fibroblasts. The purpose of this study was to track the injected fibroblasts and todetermine the effect of adding prostaglandin E1 (PGE1) or vitamin C on the viability of fibroblasts. Human fibroblasts labeled with fluorescence dye were suspended in HA filler and injected into 4 sites on the back of nude mice. The injected bioimplants consisted of one of the 4 followings: HA filler without cells(HAgroup), fibroblasts suspendedinHAfiller(HAFB group), PGE1-supplemented fibroblasts in HA filler (HAFB PGE1 group), and vitamin C-supplemented fibroblasts in HA filler (HAFBVC group). At 4 weeks after injection, locations and intensities of the fluorescence signals were evaluated using a live imaging system. The fluorescence signals of the fibroblast-containing groups were visible only at the injected sites without dispersing to other sites. The HAFBPGE1 group showed a significantly higher fluorescence signal than the HAFB and the HAFBVC groups (P<0.05, each). There was no statistical difference between the HAFB and HAFBVC groups (P=0.69). The results of the current study collectively suggest that injected fibroblasts suspended in HA filler stay at the injected place without moving to other sites. In addition, PGE1 treatment may increase the remaining rhodamine B isothiocynanate dye at the injected site of the human dermal fibroblasts.