Excision wounds in palatal epithelium in guinea pigs

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Abstract
Standardized excision wounds were made in the palatal mucosa of 112 adult, male guinea pigs in order to study the reaction to injury of orthokeratinized epithelium. The wound area was studied histologically 4, 6, 12, 24, 48, 72, 96 and 120 h postoperatively. Four and 6 h after wounding, a triangular eosinophilic «reactive zone» was found in the stratum granulosum and the upper half of stratum spinosum along the wound margins. This cellular reaction was interpreted as an «induced keratinization». After 12 h the reactive zone was delineated from the adjacent, normal epithelial cells by 2–4 rows of hyperchromatic, flattened cells – the demarcation zone. In the reactive zone a hypertrophic cell reaction was observed. The initial epithelial cell migration started from the lowest cell layers in the stratum spinosum and stratum basale 12 h postoperatively. The migrating epithelium moved out fan‐shaped into the fibrin network under accumulations of granulocytes. The migrating cells showed few intercellular bridges, few tonofibril bundles, but many cytoplasmic granules and vacuoles. Both migrating cells and stratum spinosum cells along the wound margins exhibited erythro‐phagocytosis. After 24 h and onwards the apices of the epithelial ridges along the wound margins turned away from the wound area indicating a sliding of the epithelial mass. Seventy‐two hours postoperatively distinct changes were found in the stratum corneum up to 800–1000 microns from the wound. To the same extent stratum granulosum was replaced by a 10–12 cell layer wide demarcation zone. Ninety‐six and 120 h postoperatively the migrating epithelial lips had fused. The epithelium in the wound area showed no differentiated stratification. The superficial cell layers consisted of remains of the reactive and demarcation zones which contained numerous granulocytes. No PAS‐positive basement membrane was re‐forrned within the period studied. From the basal cell layers downward multifocal cell migration was observed. At no stage of healing was glycogen demonstrated in the epithelium.