The effects of extracts from the human dermis on the ability of the human fibroblasts to cause contraction in vitro
The starting point of this investigation was the clinical observation that raw areas of the body resurfaced by split-thickness skin grafts contract markedly, whereas those covered by thick grafts (e.g. Wolfe grafts) contract little or not at all. The reason for this behaviour is unknown. The present work was an attempt to investigate this behaviour using fibroblasts cultured in a hydrated collagen lattice (FHCL) as a laboratory model for wound contraction in vivo. Sequential extracts of normal human dermis were prepared in water, 0.15M sodium chloride, 1M sodium chloride, 0.15M citrate buffer (pH 3.5) and 6M urea, and their effects on FHCL contraction were examined. Only citrate buffer dermal extract had a marked inhibitory effect on FHCL contraction. The effect was reversible, concentration-dependent and lasted throughout the course of the 96 hours' experiments. There was no toxic effect on the cells although their proliferation within the lattices was also inhibited. Furthermore the extracts from the deeper parts of the dermis have more inhibitory effect on the FHCL contraction than those from the more superficial layers. Preliminary attempts to characterise the citrate buffer dermal extract biochemically showed the presence of protein and proteoglycans or glycosaminoglycans with a range of molecular weights showed by gel electrophoresis, and the presence of collagen was excluded by amino acid analysis. This study shows that there is a biochemical factor (factors) present in the dermis which inhibits the ability of fibroblasts to cause lattice contraction. This factor (s) can be extracted by citrate buffer. The inhibitory effect of the citrate buffer dermal extract on lattice contraction is due to inhibition of both fibroblasts proliferation and migration.