Sequential Treatment with SDF-1 and BMP-2 Potentiates Bone Formation in Calvarial Defects.

Stromal cell-derived factor-1 (SDF-1) protein and its receptor, CXCR-4, play an important role in tissue repair and regeneration in various organs, including the bone. SDF-1 is indispensable for bone morphogenetic protein-2 (BMP-2)-induced osteogenic differentiation. However, SDF-1 is not needed after the osteogenic induction has been activated. Since the precise condition for the additive effects of combined DF-1 and BMP-2 in bone healing had not been fully investigated, we aimed to determine the optimal conditions for SDF-1- and BMP-2-mediated bone regeneration. We examined the in vitro osteoblastic differentiation and cell migration after sequential treatments with SDF-1 and BMP-2. Based on the in vitro additive effects of SDF-1 and BMP-2, the critical size defects of mice calvaria were treated with these cytokines in various sequences. Phosphate buffered saline (PBS)-, SDF-1-, or BMP-2-soaked collagen scaffolds were implanted into the calvarial defects (n=36). Periodic percutaneous injections of PBS or the cytokine SDF-1 and BMP-2 into the implanted scaffolds were performed on days 3 and 6, postoperatively. Six experimental groups were used according to the types and sequences of the cytokine treatments. After 28 days, the mice were euthanized and bone formation was evaluated with microcomputed tomography and histology. The molecular mechanism of the additive effect of SDF-1 and BMP-2 was evaluated by analyzing intracellular signal transduction through Smad and Erk phosphorylation. The in vitro experiments revealed that, among all the treatments, the treatment with BMP-2 after SDF-1 showed the strongest osteoblastic differentiation and enhanced cell migration. Similarly, in the animal model, the treatment with SDF-1 followed by BMP-2 treatment showed the highest degree of new bone regeneration than any other groups, including the one with continuous BMP-2 treatment. This new bone formation can be partially explained by the activation of Smad and Erk pathways and enhanced cell migration. These results suggest that sequential treatment with the cytokines, SDF-1 and BMP-2, may be a promising strategy for accelerating bone regeneration in critical size defects.

Angiographic embolization for hemorrhage control after dental implantation.

Dental implantation in the mandibular anterior region is considered a safe and reliable surgical procedure. On the other hand, several articles have reported that inadvertent hemorrhage of the sublingual artery can result in life-threatening airway obstruction. Surgical ligation under intubation or tracheostomy is the most widely used approach for controlling mouth floor bleeding in this highly vascular region. Nonetheless, surgically exploring the bleeding focus is difficult because of anatomical distortion followed by widespread edema and swelling. Since swelling of the mouth floor advances quickly, timely management is essential for favorable postoperative outcome. This paper reports a case of immediate hemorrhage control with angiographic embolization to perform rapid hemostasis before the ongoing swelling causes airway obstruction. Less invasive, angiographic embolization can prevent neurovascular damage during a surgical exploration of injured vascular structures on the mouth floor.