Fabricationand reorganjzation of dermal eqtivalents suitable for skin grafting after major cutaneousinjury PamelaJ.E. Ftowling John N. Keamtey+ * +, Michael J. Ramvorthy*, EdwardJ. Wood* and *Department of Biochemistry. University of Leeds, Leeds LS2 9JT; ‘Regional Tissue Bank Pinderfields General Hospital. Wakefield WFl 5DG, UK William J. Cunliffe Depaflment of Dermatology, Leeds General Infirmary, Leeds LS 1 3EX, UK (Received 13 October 1988; revised 31 January 1989; accepted 4 Febroaty 1989) zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCB The incorporation of fibroblasts into a hydrated collagen lattice results in lattice contraction and collagen reorganization to form a dermal equivalent. lattices fabricated with 7.7 mg collagen and seeded with 1 X lo5 cells were found to give the best results in terms of their mechanical properties and ability to maintain cell viability. Newly-cast lattices were found to be completely digested by 0.085 units/ml bacterial collagenase in 3 h, whereas after 30 d in culture, limited digestion took place over 24 h. Electrophoretic analysis showed that the proportion of cross-linked collagen in the 30 d lattice was increased by 2.5fold compared to the initial collagen preparation. These results indicate that a dermal equivalent better suited for grafting may be produced after 20-30 d in culture. Keywords: Collagen, fibroblast, dermal equivalent, bum therapy The use of cultured autogeneic or allogeneic keratinocyte sheets for replacement of burn-damaged epithelium is currently receiving close scrutiny’-3. However, since the optimistic early repor-ts4, some groups have reported a high rate of graft failure with this clinical procedure5 in which keratinocyte sheets are grafted directly on to muscle fascia or early granulation tissue. In recent work it has been shown that the presence of a dermis, introduced as a cadaveric dermal allograft6, or a xenograft7 may improve the ‘take’ of the cultured epidermal autograft and suppress scar tissue formation6. The problem of replacing large amounts of lost dermis has been approached in a number of other ways*-” but only the fibroblast-reorganized collagen lattice or dermal equivalent method of Bell et a/.g,‘2.13 involves the incor- poration of fibroblasts in the dermal graft. This technique may also be modified by incorporating factors known to promote wound healing. Although a number of studies on dermal equivalents to be used for grafting have been reportedg, there is little information on the relationship of dermal equivalent composition to clinical requirements. The dermal equivalent provides a three-dimensional culture Correspondence to Dr M.J. Raxworthy at 3M Health Care Ltd. 3M House. Merely Street, Loughborough. Leicestershlre LEl 1 1 EP, UK. 1990 Butterworth Et Co (Publishers) Ltd. 0142-9612/90/030181-05 system that serves as a model suitable for the study of fibroblast behaviour in vitro and several studies have employed this system for the investigation of extracellular matrix events. For the most part these studies have been of short duration. Guidry and Grinnell14 measured total protein content and lattice thickness as fibroblasts reorganized collagen lattices over 72 h. Collagen released during reorganization was monitored for 24 h. They studied the effect on lattice contraction of substances secreted by fibroblasts in vivo during wound healing15, measuring these effects for 24 h. Ehrlich and Wyler16 investigated the effect of soluble factors secreted by chronic inflammatory cells on lattice contraction over 4 d. Adams et a/.17 compared the behaviour of normal and Duchenne dystrophy fibroblasts within lattices. Studies monitoring cell growth and lattice contraction lasting up to 14 d have been performed by Schor” and by Coulomb et a/.“. We report here studies to determine which collagen concentration and fibroblast seeding to be used in dermal equivalent fabrication most closely provides the desired physical characteristics of a dermal graft. The changes that take place as the lattice is reorganized by fibroblasts have been monitored for up to 30 d in culture. Our aim was to investigate in vitro parameters likely to be of importance to skin graft performance in vivo. Biomaterials 1990. Vol 1 1 April 181