Histological characteristics of induced acute peptic injury in equine gastric squamous epithelium
Authors: MURRAY M. J. , EICHORN E. S. , JEFFREY S. C. 
Published: April 2007

The objective of the study reported here was to characterise the microscopic appearance of peptic‐injured equine gastric squamous epithelium in relation to the duration of peptic injury. Erosions and ulcers were induced in equine gastric squamous epithelium using a feed deprivation protocol that results in prolonged increased gastric acidity. Specimens of normal gastric mucosa and mucosa with lesions created after 48 and 96 h of feed deprivation were compared for characteristics associated with angiogenesis and mucosal proliferation. Fifteen mature horses, 9 geldings and 6 mares, age 3–20 years, were divided into 3 groups.Group 1(n = 5) had normal‐appearing gastric squamous mucosal epithelium and had been killed due to problems unrelated to the gastrointestinal tract.Groups 2(n = 5) and3(n = 5) had lesions induced in the gastric squamous epithelium by alternating 24 h periods of feed deprivation andad libitumaccess to hay, for totals of 48 and 96 h feed deprivation, respectively. Following lethal injection of barbiturate, stomachs were removed and fixed by filling with 4–6 l 10% buffered formalin. Sections were made from lesions in the gastric squamous epithelium adjacent to themargo plicatusalong the right side of the stomach/greatercurvature and the lesser curvature. Measurements of total epithelial thickness, keratinised epithelium, nonkeratinised epithelium, epithelial projections, capillary extension into the epithelium andlamina propriathickness were made. The cross‐sectional areas of arterial and venous vascularstructures in thelamina propriaat the lesions and theirmargins were measured using image analysis software.

All horses, except one, inGroup 2developed erosions or ulcers in the gastric squamous epithelium after feed deprivation. There were several changes in the epithelium adjacent to erosions and ulcers, compared to normal epithelium, from horses inGroups 2and3: total epithelial thickness was significantly (P<0.05) greater, including both keratinised and nonkeratinised layers in most specimens; the length of epithelial projections and extent to which capillaries from thelamina propriaextended toward the luminal surface, and the cross‐sectional area of vascular structures (arterioles, capillaries, venules) in thelamina propriawere significantly greater. Epithelial thickness of erosion beds was not significantly less than normal epithelium, although a greater proportion of the epithelium in erosions consisted of epithelial projections (Group 1, 23%;Group 2, 76%;Group 3, 72%). The cross‐sectional area of vascular structures in thelamina propriabeneath erosions was significantly greater than in normal mucosa only inGroup 2tissues, whereas in thelamina propriaof ulcers it was significantly greater than in normal mucosa only inGroup 3tissues.

The epithelial proliferation and increased vascularcross‐sectional area in thelamina propriaassociated with peptic‐induced gastric lesions are consistent with processes associated with the initiation of ulcer healing, and these changes temporally coincided with the initiation of peptic insult to the gastric squamous epithelium. These findings demonstrate that processes that promote ulcer healing begin soon after peptic injury and that they progress even with repeated peptic injury. Furthermore, our findings support observations that gastric ulcers often heal without medical intervention, and the theory that medications that reduce gastric acidity do not initiate healing, but rather facilitate ulcer healing by providing a microenvironment that is optimal for healing to proceed.