Preclinical assessment of the collagen-based paste Permacol(tm) for the role of a dermal substitution in full-thickness wounds

Insufficient skin for autologous grafts makes treatment of full-thickness extensive burns difficult. Poor long-term results from application of cultured keratinocyte sheets or suspensions to such wounds are thought to be due to the absence of a dermis. The porcine collagen-based biomaterial Permacol tm in sheet form is useful as a stable implant in reconstructive surgery, but its use as a dermal substitute has been hindered by slow cell penetration and vascularisation. Here, a paste formulation was evaluated as a dermal substitute in full-thickness wounds to encourage cellular infiltration. Full-thickness biopsy and wound-chamber models were done in the large white pig under local ethics committee approval and government license. Biopsy model allowed 24 samples of 8mm diameter and the chamber-model allowed 6 samples of 4cm diameter per pig. Permacol was applied as a paste to the wound bed and covered with a split-thickness skin graft or non-adherent dressing, with suitable control wounds in parallel. Biopsies taken at specific time points were assessed for biointegration and neovascularisation using histological and immunofluorescent analysis. Permacol paste accepted host dermal mesenchymal and epidermal cells. It was well penetrated by cells on day 2 and integrated into the host without causing excessive inflammation, indicating successful biointegration. host cellular infiltration of Permacol paste was much superior to Permacol sheet and very similar to Integra. Paste was visible within the tissue samples and intact up to day 27, indicating presence of a stable biomaterial. Early neovascularisation was noted at day 4, and functional microvessels with circulating blood cells were discovered at day 7 and confirmed by immunostaining for vascular endothelium. This was comparable to Integra, currently the gold standard dermal substitute. This piolt study indicates that a paste formulation of Permacol successfully biointegrated into full-thickness wounds and may act as an alternative to current dermal substitutes.