Blebs and hematomas in the lips of CL/Fr and A/J mice

Newborn-CL/Fr mice have +/- 20% frequency of cleft lip with or without cleft palate (CLP) depending on environment. However, examination of early fetal development from days 12 to 15 disclosed an increased number of hematomas or fluid-filled blebs in the regions of maxillary process fusion. The earliest stages do not appear to involve the blood supply directly but separate the epithelium from underlying mesenchyme by clear blebs. Similar defects were found in untreated A/J mice. These findings suggest that osmotic and hemodynamic abnormalities may be part of the mechanism of cleft lip formation in these related strains and that these defects may result from a biochemical defect of the connective tissue matrix in regions of process fusion.