In vitro investigation of the secondary palate development in two strains of mice

The pathogenesis of cleft lip and palate (CL/P) is studied in animal experiments. This study revealed significant differences in foetal secondary palate development in two strains of mice (NMRI, A/WySnJ) using a palatal organ model. Palatal shelves of 114 NMRI embryos, resistant to cleft occurrence, and 93 A/WySnJ embryos, a strain with a high spontaneous CL/P rate, were micro-dissected at 14.25 GD (gestational day), before palatal fusion takes place. After cultivation in serum-free medium, palatal development was investigated microscopically and scored in a six-step system. At death (14.25 GD) the palatal shelves of the NMRI embryos (mean 3.5) were significant more developed than those of A/WySnJ (mean 2.7; p=0.05). After incubation, 53% (60/114) NMRI and 14% (13/93) A/WySnJ cultures had over two-thirds fusion to stage V-VI, therefore in 17% NMRI (19/114) and 1% A/WySnJ cultures (1/93) fusion was macroscopically complete. 62% of the A/WySnJ cultures showed no significant development in vitro (mean 2.84; p=0.094). There is a significant palatal development difference between normally developed NMRI (mean 4.45, p=0.05) and CL/P appearance in A/WySnJ mice (mean 2.84). Palatal development of both strains was significantly delayed in organ culture (p=0.05). The A/WySnJ strain was more susceptible to manipulation and vulnerable.