Mechanical and humoral factors in wound healing

Abstract

Summary As wound contraction can be prevented by full-thickness skin graft and enhanced by licking and since saliva contains growth-promoting macromolecules, we have studied the mechanical and humoral aspects of wound healing. Standardized burn and freeze-produced wounds were produced in rats. Contraction did not occur in wounds caused by freezing (n = 30), while burn wounds (n = 30) contracted to less than one-third of the original size in 3 weeks. If the centres of the freeze-produced wounds (n = 12) were excised, contraction would then occur and proceed at the same rate as open wounds (n = 12). The collagen contents of the burn wounds (n = 24) showed a greater initial loss followed by rapid replacement, while that of the freeze-produced wounds (n = 24) demonstrated a slower removal and more gradual replacement. Submandibular sialadenectomized mice (n = 34) and sham controls (n = 34) had excision of a standard sized patch of sacral skin. Through a separate abdominal incision polyvinyl sponges of known weight were introduced subcutaneously into all the animals. Mice without the submandibular salivary glands showed a slower rate of wound contraction than the sham controls (P<0.001). However, this delay in wound contraction was abolished if sialadenectomized mice were caged with mice having intact salivary glands. Collagen synthesis as determined by the hydroxyproline concentrations in the polyvinyl sponges were the same in both groups of animals irrespective of cage environment. Further standard sacral wounds in submandibular sialadenectomized mice (n = 120) were treated with different salivary components. Only high molecular weight nerve growth factor was able to accelerate wound contraction in these sialadenectomized animals to control values. In conclusion, the degree of wound contraction following injury is dependent on the integrity of the matrix, while the initiation of contraction is likely to be chemically induced.