Tissue engineering for cutaneous wounds: an overview of current standards and possibilities

Transfer of fibroblast sheets cultured on thermoresponsive dishes with membranes

In cell or tissue engineering, it is essential to develop a support for cell-to-cell adhesion, which leads to the generation of cell sheets connected by extracellular matrix. Such supports must be hydrophobic and should result in a detachable cell sheet. A thermoresponsive support that enables the cultured cell sheet to detach using only a change in temperature could be an interesting alternative in regenerative medicine. The aim of this study was to evaluate plates covered with thermoresponsive polymers as supports for the formation of fibroblast sheets and to develop a damage-free procedure for cell sheet transfer with the use of membranes as transfer tools. Human skin fibroblasts were seeded on supports coated with a thermoresponsive polymer: commercial UpCell™ dishes (NUNC™) coated with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and dishes coated with thermoresponsive poly(tri(ethylene glycol) monoethyl ether methacrylate) (P(TEGMA-EE)). Confluent fibroblast sheets were effectively cultured and harvested from both commercial PNIPAM-coated dishes and laboratory P(TEGMA-EE)-coated dishes. To transfer a detached cell sheet, two membranes, Immobilon-P(®) and SUPRATHEL(®), were examined. The use of SUPRATHEL for relocating the cell sheets opens a new possibility for the clinical treatment of wounds. This study established the background for implementing thermoresponsive supports for transplanting in vitro cultured fibroblasts.

Adult burn patients with more than 60% TBSA involved-Meek and other techniques to overcome restricted skin harvest availability--the Viennese Concept

Despite the fact that early excision and grafting has significantly improved outcome over the last decades, the management of severely burned adult patients with >/=60% total body surface area (% TBSA) burned still represents a challenging task for burn care specialists all over the world. In this article, we present our current treatment concept for this entity of severely burned patients and analyze its effect in a comparative cohort study. Surgical strategy comprised the use of split-thickness skin grafts (Meek, mesh) for permanent coverage, fluidized microsphere bead-beds for wound conditioning, temporary coverage (polyurethane sheets, Epigard; nanocrystalline silver dressings, Acticoat; synthetic copolymer sheets based on lactic acid, Suprathel; acellular bovine derived collagen matrices, Matriderm; allogeneic cultured keratinocyte sheets; and allogeneic split-thickness skin grafts), and negative-pressure wound therapy (vacuum-assisted closure). The autologous split-thickness skin graft expansion using the Meek technique for full-thickness burns and the delayed approach for treating dorsal burn wounds is discussed in detail. To demonstrate differences before and after the introduction of the Meek technique, we have compared patients of 2007 with >/=60% TBSA (n = 10) to those in a matched observation period (n = 7). In the first part of the comparative analysis, all patients of the two samples were analyzed with regard to age, abbreviated burn severity index, Baux, different entities of % TBSA, and survival. In the second step, only the survivors of both years were separated in two groups as follows: patients receiving skin grafts, using the Meek technique (n = 6), were compared with those without Meek grafting (n = 4). When comparing the severely burned patients of 2007 with a cohort of 2006, there were no differences for age (2007: 46.4 +/- 13.4 vs. 2006: 39.1 +/- 14.8 years), abbreviated burn severity index score (2007: 12.2 +/- 1.0 vs. 2006: 12.1 +/- 1.2) or % TBSA (2007: 72.1 +/- 11.7 vs. 2006: 69.3 +/- 8.7% TBSA). In these two rather small groups of severely burned patients with >/=60% TBSA, the overall survival rate of patients was 70.0% (7/10) in 2007 and 42.9% (3/7) in 2006, respectively. Almost all nonsurvivors in both years died within the first 5 days after admission. If assessing the different treatment modalities of the survivors, we found that although the Meek group patients were older (Meek 48.8 +/- 13.3 vs. non-Meek 26.8 +/- 11.5 years, P = .0381) and had consequently higher Baux scores (Meek 124.0 +/- 2.9 vs. non-Meek 93.8 +/- 8.5, P = .0095) than the non-Meek patients, this seemed to have no effect on length-of-stay (80.5 +/- 9.7 vs. non-Meek 79.8 +/- 33.0 days), hospital length-of-stay (85.7 +/- 14.8 vs. non-meek 84.3 +/- 26.1 days) or number of operations (6.5 +/- 1.0 vs. non-Meek 7.0 +/- 4.1 operations). The achieved results represent a combination of various treatment changes and, therefore, cannot be attributed to a single modality. The Meek technique is one of the technical options to choose from, to achieve permanent skin replacement; we think that it has its place if integrated in a whole treatment concept for management of severely burned patients.