Compromising alterations in villus-crypt structure are common in pigs postweaning. Possible contributions of local inflammatory reactions to villus-crypt alterations during the weaning transition have not been described. This study evaluated local inflammatory responses and their relationship with morphological changes in the intestine in 21-d-old pigs (n = 112) killed either at weaning (Day 0) or 0.5, 1, 2, 4 or 7 d after weaning to either milk- or soy-based pelleted diets. Cumulative intake averaged <100 g during the first 2 d postweaning, regardless of diet. During this period of weaning anorexia, inflammatory T-cell numbers and local expression of the matrix metalloproteinase stromelysin increased while jejunal villus height, crypt depth and major histocompatibility complex (MHC) class I RNA expression decreased. Upon resumption of feed intake by the fourth d postweaning, villus height and crypt depth, CD8(+) T cell numbers, MHC class I RNA expression and local expression of stromelysin returned to Day 0 values. Together the results indicate that inadequate feed intake during the immediate postweaning period may contribute to intestinal inflammation and thereby compromise villus-crypt structure and function.

Stromelysin 3 (ST3) is a member of the metalloproteinase family, which is expressed in the skin during wound healing and in the stroma of basal cell carcinoma. A high level of expression of ST3 has been observed in carcinomas of poor prognosis. In benign tumors, though, ST3 is not expressed or is at a low level. We have immunohistochemically studied the expression of ST3 in 89 randomly selected cases of squamous cell carcinomas (SCCs), 104 of keratoacanthomas (KA), and 23 cases of metastatic SCC. Stromelysin 3 was expressed only by fibroblasts surrounding the tumors and not by epithelial cells. The proportion of tumors positively stained was 22% of KA, 47% of randomly selected SCC, and 70% of metastatic SCC. In areas of poorly demarcated neoplastic cells, a reinforcement of the staining was observed in the stroma. The intensity and dispersion of staining were used to determine the level of expression. There were significantly more SCC in the groups of high expression levels, and both parameters were significantly higher in SCC than in KA. Expression of ST3 in benign tumors is unusual. Its expression in the the stroma of keratoacanthomas can be related to the high tissue remodeling activity observed in these tumors. It also could be interpreted as in favor of the neoplastic nature of KA. Nevertheless, the level of expression was higher in SCC than in KA and seemed to be related to the prognosis of these tumors. These results correlate well with those obtained in breast cancers and in noncutaneous SCC.