Differences in extracellular matrix components and cell density during normal and dexamethasone-treated secondary palate development in two strains of mice with different susceptibility to glucocorticoid induced-clefting.

An histological and histochemical study analyzing cell density and distribution of extracellular matrix (ECM) components in two stages of developing secondary palate and in two strains of mice with different H-2 backgrounds was undertaken to investigate differences between a strain that is susceptible to glucocorticoid-induced cleft palate (A/Sn) and one that is resistant (C57/BL). In addition, the influence of dexamethasone treatment on ECM components was evaluated. A/Sn strain had significantly higher mesenchymal cell density compared to C57/BL at 13 days of gestation when the palatine processes are in vertical position. This difference in cell density was not significant at 14 days when palatal processes have been elevated. Dexamethasone did not alter cell density in both strains. A computer-assisted method utilizing image registration was used to compare the distribution of ECM components as judged by the stain intensity. Hyaluronate and collagen were higher in mesenchymal tissue of the palatine processes at 13 days of gestation in the C57/BL than in the A/ Sn strain. No differences in either hyaluronate or collagen were found in either strain and 14 days of development and dexamethasone treatment decreased these compounds in both strains. No differences were observed in laminin and type IV collagen of the basal lamina between strains in any of the stages studied. The results suggest that hyaluronic acid and collagen may be involved in different susceptibility to cortisone-induced cleft palate in the mouse.