Alendronate induces postnatal maxillary bone growth by stimulating intramembranous ossification and preventing premature cartilage mineralization in the midpalatal suture of newborn rats

Cleft palate is a common malformation of craniofacial development, and postnatal deficiencies in palate formation may occur. The aim of this study was to determine whether alendronate treatment could induce maxillary mineralization and thus reduce the need for surgical procedures. The effects of alendronate on maxillary bone development, the midpalatal suture, and the levels of transforming growth factor beta-1 (TGF-beta 1), bone morphogenetic protein 2 (BMP-2), collagen I and II, and V-ATPase were evaluated in newborn rats. Thirty newborn rats were placed in a control group and 30 in a group that received intraperitoneal alendronate (2.5 mg/kg/day). The animals were euthanized on day 7 or 12, and the heads were subjected to histological and immunohistochemical analyses. Specimens from rats that received alendronate presented larger bone matrix deposition in areas of intramembranous ossification of the maxillary bone when compared to controls. Furthermore, higher levels of TGF-beta 1, BMP-2, and collagen I were observed, whereas osteoclasts showed no V-ATPase. The alendronate group also showed higher levels of TGF-beta 1 and collagen II in the midpalatal suture, whereas BMP-2 levels were lower than in controls. These results coincided with an expansion of the chondroid. In conclusion, alendronate increased the intramembranous ossification in the maxillary bone in association with increased expression of TGF-beta 1, BMP-2, and collagen I and decreased V-ATPase. The drug induced an expansion of chondrocytes and a decrease in mineral bone deposition despite the high levels of TGF-beta 1 in this area. Alendronate may therefore be useful in the treatment of diseases affecting bone growth.