Keisuke Sumi

Bone Regeneration in Artificial Jaw Cleft by Use of Carbonated Hydroxyapatite Particles and Mesenchymal Stem Cells Derived from Iliac Bone

Objectives of the Study. Cleft lip and palate (CLP) is a prevalent congenital anomaly in the orofacial region. Autogenous iliac bone grafting has been frequently employed for the closure of bone defects at the jaw cleft site. Since the related surgical procedures are quite invasive for patients, it is of great importance to develop a new less invasive technique. The aim of this study was to examine bone regeneration with mesenchyme stem cells (MSCs) for the treatment of bone defect in artificially created jaw cleft in dogs. Materials and Methods. A bone defect was prepared bilaterally in the upper incisor regions of beagle dogs. MSCs derived from iliac bone marrow were cultured and transplanted with carbonated hydroxyapatite (CAP) particles into the bone defect area. The bone regeneration was evaluated by standardized occlusal X-ray examination and histological observation. Results. Six months after the transplantation, perfect closure of the jaw cleft was achieved on the experimental side. The X-ray and histological examination revealed that the regenerated bone on the experimental side was almost equivalent to the original bone adjoining the jaw cleft. Conclusion. It was suggested that the application of MSCs with CAP particles can become a new treatment modality for bone regeneration for CLP patients.

Experimental Tooth Movement Into New Bone Area Regenerated by Use of Bone Marrow–Derived Mesenchymal Stem Cells

Objective The aim of this study was to examine experimental tooth movement into regenerated bone in alveolar cleft with mesenchymal stem cells and a granulated carbonated hydroxyapatite scaffold. Design An artificial bone defect was created bilaterally in upper incisor regions of beagle dogs to simulate alveolar clefts in patients with cleft palate. The mesenchymal stem cells derived from the iliac bone marrow were cultured and transplanted with carbonated hydroxyapatite into the bone defect area. Carbonated hydroxyapatite alone was transplanted on the control side. Six months after the transplantation, multi-bracket appliances were attached to the lateral incisors and canines on both sides of the maxilla to exert an orthodontic force of 100 × g using an elastic chain. The distance between lateral incisor and canine was measured, and standardized x-ray images were taken every month. The tissue after tooth movement was evaluated by histological observation. Results The experimental tooth movement, accompanied by resorption of regenerated bone and new bone formation, was achieved on the experimental and control sides. Although there was no difference in the amount of tooth movement obtained on the experimental and control sides during the 6-month experimental period, the rate of tooth movement varied on the control side; whereas, the rate was consistent on the experimental side. Root resorption of the tooth was observed on the control side in one dog. Conclusion It is suggested that mesenchymal/carbonated hydroxyapatite transplantation therapy has great potential as a new treatment modality for bone regeneration in patients with cleft palate.

The effect of mesenchymal stem cells on chemotaxis of osteoclast precursor cells

Regeneration of tissue, including bone, using mesenchymal stem cells (MSCs) has been progressing rapidly. Regeneration of bone requires the presence of an appropriate environment and efficient chemotaxis of cells to the target site. Differentiation of MSCs into mesenchymal cells has received considerable attention, but the effect of MSCs on chemotaxis is not well understood. In this study, we investigated the effect of MSCs on chemotaxis of RAW264 cells via C-C motif chemokine ligand 2 (CCL2). Balb/c mouse bone marrow-derived MSCs and RAW264 cells, which are osteoclast precursor cells, were co-cultured without cell contact. The gene expression of CCL2 in MSCs and CC-chemokine receptor 2 (CCR2) in RAW264 cells was determined using quantitative real-time PCR. Analysis of RAW264 cell chemotaxis was performed using the Boyden chamber assay. mRNAs for CCL2 and CCR2 were significantly upregulated upon co-culture in comparison to culture of either cell type alone, and the number of chemotactic RAW264 cells was significantly increased by co-culture. MSCs enhanced the chemotaxis of RAW264 cells, possibly via CCL2-CCR2 interaction, suggesting the potential utility of MSCs for tissue regeneration.

Effect of high-frequency near-infrared diode laser irradiation on periodontal tissues during experimental tooth movement in rats: HIGH FREQUENCY LASER ACCELERATES TOOTH MOVEMENT

Tooth movement during orthodontic treatment is associated with bone neoplasticity and bone resorption on the tension and pressure sides. Previous clinical studies have suggested that low‐power laser irradiation can accelerate tooth movement during orthodontic treatment, although the underlying mechanism remains unclear. In this study, we used a high‐frequency near‐infrared diode laser that generates less heat and examined the histologic changes in periodontal tissue during experimental tooth movement with laser irradiation.

Dynamic imaging of the effect of mesenchymal stem cells on osteoclast precursor cell chemotaxis for bone defects in the mouse skull

Background/purpose Mesenchymal stem cells (MSCs) transplantation has previously been used in the field of regenerative medicine. Although bone regeneration is known to occur through the interaction between osteoblasts and osteoclasts, the effect of MSCs on osteoclasts is unknown. Therefore, the purpose of this study was to investigate the effect of MSCs on the chemotaxis of osteoclast precursor cells (RAW264 macrophage cells). Materials and methods Bone defects were created in mice skulls, and MSCs and a scaffold of carbonated hydroxyapatite were transplanted into the bone defects. RAW264 cells were then transplanted into the mouse tail vein, and their dynamics were observed by an in vivo imaging system. Results The fluorescent intensity of the MSCs transplant group at the bone defect region was significantly higher on days 3, 5, and 7 compared with the MSCs non-transplant group. Conclusion Increased RAW264 chemotaxis to the bone defect region occurred following the simultaneous implantation of MSCs in the skull defect.

A comparison of proliferation of human mesenchymal stem cells derived from adipose tissue treated with human full-length amelogenin and C-terminal amelogenin peptide

Amelogenins are enamel matrix proteins that play crucial roles in enamel formation. Previous studies have indicated that amelogenin and amelogenin C-terminal peptides have cell-signaling functions. Recently, adipocyte-derived mesenchymal stem cells (ADSCs) have received attention as a potential source of stem cells for use in regeneration therapy. In this study, we examined the effects of human full-length amelogenin (rh174) and amelogenin C-terminal peptide (amgCP) on the proliferation of ADSCs. ADSCs were cultured in the presence of amgCP or rh174. Cell proliferation was analyzed using BrdU immunoassay and MTS assay. Cell migration was evaluated by ELISA. The MAPK-ERK pathway was examined by phospho-p44/42 MAPK (Thr202/Tyr204) sandwich ELISA and western blotting. A specific MAPK inhibitor, U0126, was used to block ERK activity. ADSC proliferation and migration were significantly (P < 0.05) increased in the presence of rh174 or amgCP compared to non-treated control cells. The increased proliferation of ADSCs induced by rh174 or amgCP was significantly (P < 0.05) inhibited in the presence of 2 µg/ml U0126. The pERK/tERK ratio was significantly (P < 0.05) increased upon treatment with rh174 or amgCP compared to non-treated ADSCs, while this increase was significantly (P < 0.05) suppressed by the addition of U0126. Similar results were found by western blot analysis. In conclusion, amgCP and rh174 increase ADSC proliferation via the MAPK-ERK signaling pathway, and ADSCs may be useful for tissue regeneration in the orofacial region.