Cleft lip and palate deformities are among the most common congenital anomalies. These present significant functional and aesthetic disorders. Although numerous efforts have been made to improve the clinical outcomes of cleft palate treatments, there is little agreement on the optimal treatment of cleft palate. The early closure of cleft palate provides better speech development but wound contraction resulting from surgical closure of soft tissues may impair the normal midfacial growth. A recent study indicates that promoting bone regeneration along with early closure of cleft palate may help normal midfacial growth and development. Recently, mesenchymal stem cells (MSCs) isolated from umbilical cord blood (UCB) exhibited the ability to differentiate into bone cells while treatment, and bone morphogenetic protein-2 (BMP-2) can promote bone regeneration in the palatal defects. Therefore, the objective of this study is to determine whether bone regeneration can be promoted by the implantation of human UCBMSCs and further enhanced by adding BMP-2 treatment in cleft palate repair using a rat model. The effects of cell implantation and BMP-2 treatment on maxillofacial growth will be examined. The hypotheses of this study are: (1) the implantation of human UCB-MSCs at the bone defect site can promote tissue regeneration and subsequently preserve normal midfacial growth; (2) BMP-2 can enhance bone regeneration by stimulating human UCB-MSCs activity. The specific aims of this study are: (1) we will examine new bone formation and midfacial growth after implanting human UCB-MSCs into rat palatal defects; (2) we will examine new bone formation and midfacial growth after combining BMP-2 with the implantation of human UCB-MSCs in into rat palatal defects. The outcome of this study will provide guidance for creating new and improved treatments to benefit babies born with cleft palate deformities by preserving normal midfacial growth and helping normal speech development.