Transplantation of autologous keratinocyte suspension in fibrin matrix to chronic venous leg ulcers: Improved long-term healing after removal of the fibrin carrier

BACKGROUND The transplantation of keratinocytes suspended in fibrin carrier represents a candidate regimen for chronic ulcer treatment in an outpatient setting. We evaluated the integration and survival of autologous individualized keratinocytes applied within fibrin matrix onto chronic venous leg ulcers in vivo. Parallel in vitro culture was used to validate keratinocyte survival and apoptosis in fibrin compared to collagen matrix carrier. METHODS Seven patients with chronic venous leg ulcers were transplanted with autologous keratinocytes suspended in fibrin sealant after isolation and expansion from full-skin biopsy. The fibrin carrier was removed in three patients after 7 days, whereas four patients served as control with fibrin remaining. In parallel in vitro cultures, primary keratinocyte movement in fibrin as well as viability in three-dimensional (3D) fibrin versus collagen lattices was examined. RESULTS Complete ulcer healing was observed in four of seven ulcers after a mean duration of 14.5 weeks. If the fibrin layer was removed, complete wound healing occurred in three of three patients, compared to one of four in the control group. In vitro, keratinocytes formed a monolayer underneath but remained isolated and nonmobile within the fibrin matrix, suggesting reepithelialization along the lower fibrin interphase. Keratinocyte culture in 3D fibrin at clinically used concentration (90 mg/mL) caused high levels of apoptosis, similar to 3D collagen, which was prevented by diluting fibrin concentration to 3 mg/mL. CONCLUSIONS Transplantation of autologous keratinocytes suspended in fibrin is efficient in the treatment of chronic venous leg ulcers. Due to an antimigratory and survival-compromising effect, the presently used fibrin carrier should be removed after a few days of transplantation.