Inductive effect of SORT1 on odontoblastic differentiation of human dental pulp-derived stem cells.

This study investigated the expression of sortilin 1 (SORT1) in cultured human dental pulp-derived stem cells (hDPSCs) and its role in their odontoblastic differentiation. Permanent teeth were extracted from five patients, and the dental pulp was harvested for explant culture. Fluorescence-activated cell sorting was used to analyze the outgrowth of adherent cells and cells that had migrated from the tissue margin. SORT1 expression was detected in hDPSCs simultaneously expressing the mesenchymal stem cell markers CD44 and CD90. The odontoblastic differentiation potential of SORT1-positive hDPSCs was examined via staining for alkaline phosphatase (ALP), an early odontoblastic differentiation marker. ALP staining was more intense in SORT1-positive than in SORT1-negative hDPSCs. Consistently, the expression of mRNA encoding SORT1 and p75NTR, a binding partner of SORT1, increased in SORT1-positive hDPSCs during odontoblastic differentiation. In addition, pro-nerve growth factor (NGF), a ligand for SORT1-p75NTR co-receptor, promoted ALP expression in SORT1-positive hDPSCs, and the interaction between SORT1 and p75NTR was detected using a coimmunoprecipitation assay. The function of SORT1 in odontoblastic differentiation was examined via RNA interference using shRNA targeting SORT1. ALP staining intensity in SORT1/shRNA-transfected cells was markedly lower than in control/shRNA-transfected cells. SORT1 knockdown decreased JUN phosphorylation and recruitment of phosphorylated JUN to the ALP promoter. Collectively, these results indicate that SORT1 is involved in the odontoblastic differentiation of hDPSCs through the JUN N-terminal kinases (JNK)/JUN signaling pathway and that the binding of SORT1 and p75NTR plays an important role in this process.

An atypical inferior gluteal artery passing through the piriformis muscle.

PURPOSE: In this article, we report a case of an atypical inferior gluteal artery that passed through the piriformis muscle when it emerged from the pelvic cavity in an elderly Japanese female cadaver. We speculate that this atypical artery could be entrapped and compressed by the piriformis muscle and may therefore be associated with piriformis syndrome; however, the anatomical characteristics of such an atypical artery have not been previously reported. To assess this potential association, the atypical inferior gluteal artery was anatomically examined. METHODS: The cadaver examined in this report was a 97-year-old Japanese female who was donated to The Nippon Dental University for use in medical education and research. The atypical inferior gluteal artery and surrounding structures in half of the pelvis were examined macroscopically. RESULTS: The atypical inferior gluteal artery arose from the common arterial trunk, formed by itself and the superior gluteal artery, passed through the superior proximal part of the piriformis muscle, and left the pelvic cavity. It supplies branches to the lower half of the gluteus maximus and proximal part of the long head of the biceps femoris muscle. The piriformis muscle originates from the 2nd to 4th sacral vertebrae and attaches to the greater trochanter via a single short tendon. CONCLUSION: According to our findings, when the atypical inferior gluteal artery is entrapped and compressed, ischemic signs and symptoms may emerge in the lower buttocks and proximal posterior thigh. These results provide a new perspective for the diagnosis and treatment of piriformis syndrome.

The sublingual branch of the lingual nerve: Anatomical study and suggestion for a new terminology.

The lingual nerve carries somatosensory fibers from the anterior two-thirds of tongue. The parasympathetic preganglionic fibers arising from the chorda tympani also travel with the lingual nerve in the infratemporal fossa to synapse in the submandibular ganglion to innervate the sublingual gland. However, only a few studies have investigated the specific nerve that innervates the sublingual gland and surrounding tissue i.e., the so-called sublingual nerve. Therefore, this study aimed to clarify the anatomy and definition of the sublingual nerves. Thirty sides from formalin fixed cadaveric hemiheads underwent microsurgical dissection of the sublingual nerves. The sublingual nerves were found on all sides and categorized into three branches, i.e., branches to the sublingual gland, branches to the mucosa of the floor of the mouth, and gingival branches. Additionally, branches to the sublingual gland were subcategorized into types I and II based on the origin of the sublingual nerve. We suggest that the lingual nerve branches should be categorized into five branches, i.e., branches to the isthmus of the fauces, sublingual nerves, lingual branches, posterior branch to the submandibular ganglion, and branches to the sublingual ganglion.

Reactive oxygen species generation required for autophagy induction during butyrate- or propionate-induced release of damage-associated molecular patterns from dying gingival epithelial Ca9-22 cells.

PURPOSE: Bacterial cells in mature dental plaque produce a high concentration of short-chain fatty acids (SCFAs) such as butyrate and propionate. SCFA-treatment on human gingival epithelial Ca9-22 cells induced cell death. However, the exact mechanism underlying cell death remains unclear. In this study, the relationship between reactive oxygen species (ROS) and autophagy induction during SCFA-induced cell death was examined. METHODS: Human gingival epithelial Ca9-22 cells were treated with butyrate or propionate to induce cell death and the number of dead cells were measured using SYTOX-green dye. A siRNA for ATG5 and N-acetylcysteine (NAC) were used for autophagy reduction and ROS-scavenging, respectively. Release of damage-associated molecular patterns (DAMPs) such as Sin3A-associated protein 130 (SAP130) and high-mobility group box 1 (HMGB1) were detected using western blot. RESULTS: Reducing autophagy significantly suppressed SCFA-induced Ca9-22 cell death. ROS generation was observed upon SCFA treatment, and scavenging ROS with NAC decreased cell death. NAC also reduced the SCFA-induced increase in microtubule-associated protein 1 light chain 3B (LC3B)-I and LC3B-II, and mitigated the release of DAMPs. CONCLUSION: The findings suggest that ROS generation is necessary for autophagy, which is required for SCFA-induced cell death and accompanying DAMP release.

Study protocol for periodontal tissue regeneration with a mixture of autologous adipose-derived stem cells and platelet rich plasma: A multicenter, randomized, open-label clinical trial.

Introduction: Adipose-derived stem cells (ASCs) secrete various growth factors to promote wound healing and to regenerate various tissues, such as bone, cartilage, and fat tissue. Subcutaneous adipose tissue is a considerable cell source in clinical practice and can be collected relatively easily and safely under local anesthesia. Moreover, platelet-rich plasma (PRP), a plasma component containing many platelets purified by centrifuging the collected blood, also promotes wound healing. PRP can be easily gelled and is therefore attracting attention as a scaffolding material for transplanted cells. The usefulness of a mixture of ASCs and PRP for periodontal tissue regeneration has been in vitro demonstrated in our previous study. The aim of this study is to present the protocol of translation of tissue regeneration with ASCs and PRP into practical use, evaluating its efficacy. Methods: This study is a multicenter, randomized, open-label comparative clinical trial. Fifteen patients will be randomly assigned to the treatment with mixture of ASCs and PRP or enamel matrix derivate administration into periodontal tissue defects. Increase in height of new alveolar bone in the transplanted area will be evaluated. The evaluation will be performed using dental radiographs after 36 weeks of transplantation. Occurrence of adverse events will be evaluated as secondary outcome. Results: This clinical study was initiated after meeting the regulations to be complied with, including ethical review and regulatory notifications. Conclusions: If effective, this cell therapy using autologous mesenchymal stem cells can represent a useful medical technology for regeneration of periodontal defects.

Histological analysis of dental pulp response in immature or mature teeth after extra-oral subcutaneous transplantation into mice dorsum.

PURPOSE: The aim of this study was to assess the response of dental pulp associated with donor or host cells in the pulp chamber and root canal after extra-oral transplantation. METHODS: Wild type or green fluorescent protein (GFP) transgenic first molars from 3-week, 6-week, and 12-week mice were transplanted into the subcutaneous layer of GFP mice or wild type mice. The teeth were histologically and immunohistochemically examined at 5 weeks after transplantation. RESULTS: Blood vessels present in the original coronal pulp had anastomosed with those from the recipient tissue that had invaded the root canal. Two distinct eosin-stained extracellular matrices were observed in the pulp chamber and root canal. Acellular matrix composed of nestin-positive, odontoblast-like cells invaded from the outside and was seen in the root canal of 3-week teeth. Cellular matrix comprising alkaline phosphatase (ALP)-positive fibroblast-like cells appeared in the original coronal pulp. In the root canal of the 6-week and 12-week teeth, cellular extracellular matrix consisting of ALP-positive fibroblast-like cells had invaded the recipient tissue. CONCLUSION: Dental pulp from immature teeth might be able to regenerate dentin-like tissue. This model could be useful in the development of an optimized vitalization treatment.

Performance of Schwann cell transplantation into extracted socket after inferior alveolar nerve injury in a novel rat model.

An inferior alveolar nerve (IAN) injury is a common clinical problem that can affect a patients' quality of life. Cellular therapy has been proposed as a promising treatment for this injury. However, the current experimental models for IAN injury require surgery to create bone windows that expose the nerve, and these models do not accurately mimic human IAN injuries. Therefore, in this study, a novel experimental model for IAN injury has been established in rats. Using this model, the effects of Schwann cells and their role in the recovery from IAN injuries were investigated. Schwann cells were isolated from rat sciatic nerves and cultured. The first molar in the mandible was extracted and the IAN was immediately injured for 30 min by inserting an insect pin. Then, the Schwann cells or culture medium were transplanted into the extracted sockets of the cell and injury groups, respectively. After the surgery, the cell group displayed significantly increased sensory reflexes in response to mechanical stimulation, regenerated IAN width, and myelin basic protein-positive myelin sheaths when compared with the injury group. In conclusion, a novel animal experimental model for IAN injury has been developed that does not require the creation of a bone window to evaluate the impacts of cell transplantation and demonstrates that Schwann cell transplantation facilitates the regeneration of injured IANs.

Glucagon-Like Peptide-1 Receptor Agonist Liraglutide Ameliorates the Development of Periodontitis.

Periodontitis is one of the diabetic complications due to its high morbidity and severity in patients with diabetes. The prevention of periodontitis is especially important in diabetic patients because the relationship between diabetes and periodontitis is bidirectional. Here, we evaluated the impacts of glucagon-like peptide-1 (GLP-1) receptor agonist liraglutide on the amelioration of periodontitis. Five-wk-old Male Sprague-Dawley (SD) rats (n = 30) were divided into 3 groups: normal, periodontitis, and periodontitis with liraglutide treatment groups. Periodontitis was induced by ligature around the maxillary second molar in SD rats. Half of the rats were administered liraglutide for 2 weeks. Periodontitis was evaluated by histological staining, gene expressions of inflammatory cytokines in gingiva, and microcomputed tomography. Periodontitis increased inflammatory cell infiltration, macrophage accumulation, and gene expressions of tumor necrosis factor-α and inducible nitric oxide synthase in the gingiva, all of which were ameliorated by liraglutide. Liraglutide decreased M1 macrophages but did not affect M2 macrophages in periodontitis. Moreover, ligature-induced alveolar bone resorption was ameliorated by liraglutide. Liraglutide treatment also reduced osteoclasts on the alveolar bone surface. These results highlight the beyond glucose-lowering effects of liraglutide on the treatment of periodontitis.

Therapeutic potential for insulin on type 1 diabetes-associated periodontitis: Analysis of experimental periodontitis in streptozotocin-induced diabetic rats.

AIMS/INTRODUCTION: The association between diabetes and periodontal disease is considered to be bidirectional. However, there is still controversy surrounding the relationship between periodontal disease and type 1 diabetes. We investigated whether insulin improves periodontitis without any local treatments for periodontitis under type 1 diabetes conditions using the ligature-induced experimental periodontitis model. MATERIALS AND METHODS: Type 1 diabetic rats were induced by streptozotocin injection. Experimental periodontitis was induced by ligature in normal and diabetic rats. Half of the diabetic rats were treated with insulin. Two weeks after the ligature, periodontitis was evaluated. RESULTS: Insulin treatment significantly improved inflammatory cell infiltration and inflammatory cytokine gene expression, leading to suppression of alveolar bone loss, in the periodontitis of diabetic rats. Insulin also suppressed the periodontitis-increased nitric oxide synthase-positive cells in periodontal tissue of the diabetic rats. Even without induction of periodontitis, diabetic rats showed decreased gingival blood flow and an increased number of nitric oxide synthase-positive cells in the gingiva and alveolar bone loss compared with normal rats, all of which were ameliorated by insulin treatment. We further confirmed that insulin directly suppressed lipopolysaccharide-induced inflammatory cytokine expressions in THP-1 cells. CONCLUSIONS: There were abnormalities of periodontal tissue even without the induction of periodontitis in streptozotocin-induced diabetic rats. Insulin treatment significantly ameliorated periodontitis without local periodontitis treatment in diabetic rats. These data suggest the therapeutic impacts of insulin on periodontitis in type 1 diabetes.

Rat Palatine Fissure: A Suitable Experimental Model for Evaluating Bone Regeneration.

IMPACT STATEMENT: The rat palatine fissure is anatomically similar to human alveolar cleft. In this study, we examined potential bone repair by an autologous bone implant and beta-tricalcium phosphate (ß-TCP) using rat palatine fissure as a model. Autologous bone chips or ß-TCP granules were implanted into the rat palatine fissure. Our model demonstrated that higher bone volume and bone mineral density were achieved with autologous bone graft than with ß-TCP. We have provided the first demonstration of the suitability of the rat palatine fissure as the implant site to simulate the transplantation of bone graft materials into human alveolar cleft.

Bone marrow-derived mesenchymal stem cells enhance bone marrow regeneration in dental extraction sockets.

Bone marrow-derived mesenchymal stem cells (BMMSCs) remain the most widely used source of osteogenic cells in bone tissue engineering research. A cell-based treatment for alveolar ridge augmentation has received attention as an alternative to bone grafting. In the present study, BMMSC transplantation into tooth extraction sockets of C57BL/6J mice was evaluated for alveolar ridge regeneration. The first right maxillary molars were extracted, and then BMMSCs (PDGFRα+ Sca-1+ CD45- TER119- cells) isolated from femoral and tibial bone marrow were immediately transplanted into the extraction sockets. A control group underwent the same procedure except for BMMSC transplantation. Bone formation in the sockets was evaluated using micro-computed tomography and histological and immunohistochemical analyses. At 3 weeks, bone formation in the sockets was more advanced in the experimental group than in the control group. Histological analysis at 6 weeks after transplantation showed that the sockets in the experimental group also contained a greater quantity of bone marrow. Interestingly, socket bone mineral density was lower in the experimental group than in the control group at 6 weeks. These findings suggest that BMMSC transplantation accelerates bone healing and augments bone marrow formation in tooth extraction sockets.

Transplantation of dedifferentiated fat cells combined with a biodegradable type I collagen-recombinant peptide scaffold for critical-size bone defects in rats.

Tissue engineering is a promising approach to supplement existing treatment strategies for craniofacial bone regeneration. In this study, a type I collagen scaffold made from a recombinant peptide (RCP) with an Arg-Gly-Asp motif was developed, and its effect on regeneration in critical-size mandibular bone defects was evaluated. Additionally, the combined effect of the scaffold and lipid-free dedifferentiated fat (DFAT) cells was assessed. Briefly, DFAT cells were separated from mature adipocytes by using a ceiling culture technique based on buoyancy. A 3 cm × 4 cm critical-size bone defect was created in the rat mandible, and regeneration was evaluated by using RCP with DFAT cells. Then, cultured DFAT cells and adipose-derived stem cells (ASCs) were seeded onto RCP scaffolds (DFAT/RCP and ASC/RCP) and implanted into the bone defects. Micro-computed tomography imaging at 8 weeks after implantation showed significantly greater bone regeneration in the DFAT/RCP group than in the ASC/RCP and RCP-alone groups. Similarly, histological analysis showed significantly greater bone width in the DFAT/RCP group than in the ASC/RCP and RCP-alone groups. These findings suggest that DFAT/RCP is effective for bone formation in critical-size bone defects and that DFAT cells are a promising source for bone regeneration.

Transplantation effects of dental pulp-derived cells on peripheral nerve regeneration in crushed sciatic nerve injury.

The effects of transplanted human dental pulp-derived cells (DPCs) on peripheral nerve regeneration were studied in a rat model of sciatic nerve crush injury. In one group, DPCs were transplanted into the compression site (cell transplantation group); the control group underwent no transplantation (crushed group). Sciatic nerve regeneration was determined based on the recovery of motor function and histological and immunohistochemical analyses. The cell transplantation group showed improved motor function compared with the crushed group using the CatWalk XT system, which corresponded to a higher ratio of tibialis to anterior muscle weight 14 days after surgery. Histological analysis revealed a smaller interspace area and few vacuoles in the sciatic nerve after cell transplantation compared with the crushed group. The myelin sheath was visualized with Luxol Fast Blue (LFB) staining and anti-myelin basic protein (anti-MBP) antibody labeling; the percentages of LFB- and MBP-positive areas were higher in the cell transplantation group than in the crushed group. Human mitochondria-positive cells were also identified in the sciatic nerve at the transplantation site 14 days after surgery. Taken together, the observed correlation between morphological findings and functional outcomes following DPC transplantation indicates that DPCs promote peripheral nerve regeneration in rats.

Characterization of Coronal Pulp Cells and Radicular Pulp Cells in Human Teeth.

Dental pulp has garnered much attention as an easily accessible postnatal tissue source of high-quality mesenchymal stem cells (MSCs). Since the discovery of dental pulp stem cells (DPSCs) in permanent third molars, stem cells from human exfoliated deciduous teeth and from supernumerary teeth (mesiodentes) have been identified as a population distinct from DPSCs. Dental pulp is divided into 2 parts based on the developing stage: the coronal pulp and the radicular pulp. Root formation begins after the crown part is completed. We performed a sequential study to examine the differences between the characteristics of coronal pulp cells (CPCs) and radicular pulp cells (RPCs) from permanent teeth, mesiodentes, and deciduous teeth. Interestingly, although we have not obtained any data on the difference between CPCs and RPCs in permanent teeth, there are some differences between the characteristics of CPCs and RPCs from mesiodentes and deciduous teeth. The MSC characteristics differed between the RPCs and CPCs, and the reprogramming efficiency for the generation of induced pluripotent stem cells was greater in RPCs than in CPCs from deciduous teeth. The proportion of CD105+ cells in CPCs versus that in RPCs varied in mesiodentes but not in permanent teeth. The results indicate that the proportion of CD105+ cells is an effective means of characterizing dental pulp cells in mesiodentes. Taken together, the stem cells in deciduous and supernumerary teeth share many characteristics, such as a high proliferation rate and an immunophenotype similar to that of DPSCs. Thus, mesiodentes accidentally encountered on radiographs by the general dental practitioner might be useful for stem cell therapy.

Induction of neural crest cells from human dental pulp-derived induced pluripotent stem cells.

We previously generated induced pluripotent stem (iPS) cells from human dental pulp cells of deciduous teeth. Neural crest cells (NCCs) play a vital role in the development of the oral and maxillofacial region. Therefore, NCCs represent a cell source for bone, cartilage, and tooth-related tissue engineering. In this study, we examined whether iPS cells are capable of differentiating into NCCs through modification of the human embryonic stem cell protocol. First, iPS cells were dissociated into single cells and then reaggregated in low-cell-adhesion plates with neural induction medium for 8 days in suspension culture to form neurospheres. The neurospheres were transferred to fibronectin-coated dishes and formed rosette structures. The migrated cells from the rosettes abundantly expressed NCC markers, as evidenced by real-time polymerase chain reaction, immunofluorescence, and flow cytometric analysis. Furthermore, the migrated cells exhibited the ability to differentiate into neural crest lineage cells in vitro. They also exhibited tissue-forming potential in vivo, differentiating into bone and cartilage. Collectively, the migrated cells had similar characteristics to those of NCCs. These results suggest that human dental pulp cell-derived iPS cells are capable of differentiating into NCCs. Therefore, iPS cell-derived NCCs represent cell sources for bone and cartilage tissue engineering.

Effect of local bone marrow stromal cell administration on ligature-induced periodontitis in mice.

Bone marrow-derived multipotent stromal cells (BMSCs) have potent antiinflammatory effects. This study aimed to investigate the antiinflammatory potential of BMSCs using a mouse model of ligature-induced periodontitis. BMSCs were isolated from the femurs and tibiae of mice. Periodontitis was induced by placing a ligature around the right maxillary second molar. After 3 days, the mice were administered BMSC in the gingiva of the mesial interdental papilla around the ligatured molar. The ligatured and non-ligatured mice that were not administered BMSC served as controls. Differences in inflammatory infiltration and bone resorption around the roots of the second molar were assessed and were subsequently quantified using microcomputed tomography (micro-CT), histological analysis, and tartrate-resistant acid phosphatase (TRAP) staining. Micro-CT revealed that alveolar bone loss around the ligatured molars increased in a time-dependent manner; however, the effect was significantly less in BMSC-treated mice compared with ligatured control mice. Tissue histopathology revealed that BMSC administration mitigated inflammatory infiltration in ligatured BMSC mice. In addition, the number of TRAP-positive osteoclasts was markedly elevated in ligatured control mice compared with those in BMSC-treated mice. These findings indicate that local BMSC administration can mitigate inflammation and alveolar bone resorption, suggesting that administering BMSC leads to new therapeutics for periodontitis.

Transplantation of mature adipocyte-derived dedifferentiated fat cells into three-wall defects in the rat periodontium induces tissue regeneration.

The transplantation of dedifferentiated fat (DFAT) cells in combination with poly(d,l-lactic-co-glycolic acid) (PLGA) scaffolds has previously been proven as an effective approach in promoting periodontal tissue regeneration in a rat fenestration defect model. The aim of this study was to assess the regenerative potential of DFAT cells in a rat model of three-wall periodontal bone defect. Three-wall bone defects were created bilaterally on the mesial side of rat maxillary first molars and were either left untreated or treated by implantation of PLGA scaffolds with DFAT cells or PLGA alone. Four weeks after surgery, the tissues were processed for micro-computed tomography (micro-CT) and histomorphometric examination. Micro-CT revealed that the PLGA/DFAT group had significantly higher rates of bone regeneration than the other groups, while histomorphometric analysis showed that the PLGA/DFAT group had significantly higher densities of collagen fiber bundles in acellular and cellular cementum than the PLGA group. Moreover, the results indicate that the placement of the PLGA scaffold prevented the downgrowth of the junctional epithelium. These findings suggest that DFAT cells contribute to tissue regeneration in three-wall periodontal defects, while PLGA provides space necessary for periodontal tissue restoration.

Use of Rat Mature Adipocyte-Derived Dedifferentiated Fat Cells as a Cell Source for Periodontal Tissue Regeneration.

Lipid-free fibroblast-like cells, known as dedifferentiated fat (DFAT) cells, can be generated from mature adipocytes with a large single lipid droplet. DFAT cells can re-establish their active proliferation ability and can transdifferentiate into various cell types under appropriate culture conditions. The first objective of this study was to compare the multilineage differentiation potential of DFAT cells with that of adipose-derived stem cells (ASCs) on mesenchymal stem cells. We obtained DFAT cells and ASCs from inbred rats and found that rat DFAT cells possess higher osteogenic differentiation potential than rat ASCs. On the other hand, DFAT cells show similar adipogenic differentiation, and chondrogenic differentiation potential in comparison with ASCs. The second objective of this study was to assess the regenerative potential of DFAT cells combined with novel solid scaffolds composed of PLGA (Poly d, l-lactic-co-glycolic acid) on periodontal tissue, and to compare this with the regenerative potential of ASCs combined with PLGA scaffolds. Cultured DFAT cells and ASCs were seeded onto PLGA scaffolds (DFAT/PLGA and ASCs/PLGA) and transplanted into periodontal fenestration defects in rat mandible. Micro computed tomography analysis revealed a significantly higher amount of bone regeneration in the DFAT/PLGA group compared with that of ASCs/PLGA and PLGA-alone groups at 2, 3, and 5 weeks after transplantation. Similarly, histomorphometric analysis showed that DFAT/PLGA groups had significantly greater width of cementum, periodontal ligament and alveolar bone than ASCs/PLGA and PLGA-alone groups. In addition, transplanted fluorescent-labeled DFAT cells were observed in the periodontal ligament beside the newly formed bone and cementum. These findings suggest that DFAT cells have a greater potential for enhancing periodontal tissue regeneration than ASCs. Therefore, DFAT cells are a promising cell source for periodontium regeneration.

Characterization of mesenchymal progenitor cells in the crown and root pulp of primary teeth.

The existence of progenitor/mesenchymal stem cells (MSCs) was demonstrated previously in human primary/deciduous teeth. In this study, we examined dental pulp cells from root portion (root cells) of primary teeth without discernible root resorption and compared them with pulp cells from the crown portion (crown cells). Root cells and crown cells were characterized and compared to each other based on progenitor/MSC characteristics and on their generation efficiency of induced pluripotent stem (iPS) cells. Root cells and crown cells included cells manifesting typical progenitor/MSC properties such as osteogenic and adipogenic differentiation potential and clonogenicity. Interestingly, root cells showed a higher expression level of embryonic stem cell marker, KLF4, than crown cells. Moreover, the number of colony-forming unit-fibroblast and cell proliferation rate were higher for root cells than crown cells, and the efficiency of generating iPS cells from root cells was approximately four times higher than that from crown cells. Taken together, these results suggest that root cells from primary teeth show the MSC-like properties and thus could be a potent alternative source for iPS cell generation and the subsequent transplantation therapy.

Current status of drug therapies for osteoporosis and the search for stem cells adapted for bone regenerative medicine.

A number of factors can lead to bone disorders such as osteoporosis, in which the balance of bone resorption vs. bone formation is upset (i.e., more bone is resorbed than is formed). The result is a loss of bone mass, with a concomitant decrease in bone density. Drugs for osteoporosis can be broadly classified as "bone resorption inhibitors", which impede bone resorption by osteoclasts, and "bone formation accelerators", which augment bone formation by osteoblasts. Here, we describe representative drugs in each class, i.e., the bisphosphonates and the parathyroid hormone. In addition, we introduce two novel bone formation accelerators, SST-VEDI and SSH-BMI, which are currently under investigation by our research group. On the other hand, regenerative therapy, characterized by (ideally) the use of a patient's own cells to regenerate lost tissue, is now a matter of global interest. At present, candidate cell sources for regenerative therapy include embryonic stem cells (created from embryos based on the fertilization of oocytes), induced pluripotent stem cells (created artificially by using somatic cells as the starting material), and somatic stem cells (found in the tissues of the adult body). This review summarizes the identifying features and the therapeutic potential of each of these stem cell types for bone regenerative medicine. Although a number of different kinds of somatic stem cells have been reported, we turn our attention toward two that are of particular interest for prospective applications in bone repair: the dedifferentiated fat cell, and the deciduous dental pulp-derived stem cell.