Corticosteroid-induced cleft lip in mice: a teratologic, topographic, and histologic investigation.

Unlike cleft palate, relatively few teratogens have been found to induce cleft lip in mice. The present study was designed to assess the teratologic, topographic (SEM), and histologic effects on lip morphogenesis following the administration of triamcinolone hexacetonide on the eighth day of gestation. The frequency of cleft lip in treated A/J mice was found to be more than three times greater than the spontaneous frequency in untreated controls. Comparable studies with other murine strains suggest no association between the cleft lip response and either a maternal effect or the H-2 complex. Affected A/J embryos showed a severe reduction in the size of the lateral nasal processes; affected embryos also demonstrated localized cell type-specific alterations, particularly in the epithelia and at the interface between epithelium and mesenchyme.