Effect of mechanical stimulation on the differentiation of stem cells in periodontal bone tissue engineering / 口腔疾病防治

@#Currently, cell transplantation in combination with scaffold materials are one of the main strategies in periodontal bone tissue engineering. In periodontal bone tissues, the stiffness and spatial structure of tissues such as alveolar bone and cementum differ, and the difference in mechanical properties of scaffolds also has disparate effects on the proliferation and differentiation of stem cells. Accumulating evidence shows that mechanical stimulating factors such as matrix stiffness and scaffold topography modulate biological behaviors of various seeding cells, including adipose-derived stem cells and periodontal ligament stem cells. A hard matrix can promote cytoskeletal stretching of stem cells, leading to nuclear translocation of Yes-associated protein (YAP) and promoting osteogenic differentiation by upregulating alkaline phosphatase (ALP) and osteocalcin (OCN) via the Wnt/β-catenin pathway. The topologic structure of scaffolds can affect cell adhesion and cytoskeletal remodeling, increase the hardness of cells and promote the osteogenic differentiation of stem cells. In this paper, the effects of mechanical stimulation on the differentiation of stem cells in periodontal bone tissue engineering are reviewed.

Effects of continuous force application for extrusive tipping movement on periapical root resorption in the rat mandibular first molar / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to clarify the effects of continuous force application for extrusive tipping movement and occlusal interference on periapical root resorption in the rat mandibular first molar. METHODS: We constructed an appliance comprising a titanium screw implant with a cobalt-chromium post as the anchorage unit and a nickel-titanium closed coil spring (50 cN) as the active unit. Force was applied on the mandibular left first molar of rats for 8 (n = 10) and 15 days (n = 10; experimental groups), with the tooth in occlusion. Five rats were included as a non-treated control group to examine the body effect of the appliance. Active root resorption lacunae, identified using tartrate-resistant acid phosphatase, were evaluated in terms of the length, depth, and area. RESULTS: The rat mandibular first molars were mesially tipped and extruded in the occlusal direction. This mesio-occlusal tipping movement and occlusion resulted in the formation of a compression zone and active root resorption lacunae in the distoapical third of the distal roots. However, there was no significant difference in the amount of root resorption between the two experimental groups. The control group did not exhibit any active root resorption lacunae. CONCLUSIONS: Periapical root resorption was induced by continuous extrusive tipping force and occlusal interference in rat mandibular molars. These data suggest that we orthodontists had better take care not to induce occlusal interference during our orthodontic treatment.

The effect of mechanical stimuli on numerical simulation of bone remodeling / 医用生物力学

Objective To study the effect of three different kinds of mechanical stimuli (i.e. strain energy density, equivalent stress and equivalent strain) on numerical simulation of bone remodeling. Methods A two-dimensional finite element model of the proximal femur was constructed. Based on the mechanostat theory and finite element method, the inner structure of the proximal femur and its density distributions under the three different stimuli were predicted. Then the simulation results were compared quantitatively with calculation results obtained from CT images. ResultsThe predicted density distributions on the proximal femur under different stimuli were all well matched with the real structure of the proximal femur. By comparing the values and shapes of the calculated bone density curves, the predictions from the model using equivalent stress as mechanical stimuli were mostly consistent with the CT images. ConclusionsThe equivalent stress might play a leading role in mechano-regulation algorithms of bone remodeling. The accurate prediction of bone remodeling process will provide a theoretical basis for clinical practices such as orthopedic surgery, treatment of bone diseases and personalized design and optimization of prosthesis.

Study progress in biological functions of Periostin in bone mineralization / 国际生物医学工程杂志

Periostin is a matri-cellular protein which was originally identified in MC3T3-E 1 osteoblast-like cell line,expressing in multiple tissues like bones,teeth,skin and cardiac valves.Periostin is also found in a large variety of cancers and injured tissues,involving in cancer cell invasion and metastasis as well as wound repair.Recent studies have suggested the role of Periostin in osteoblast adhesion and differentiation,fibrillogenesis,mineralization and bone fracture healing,and its expression is regulated by mechanical stress,various transcription factors,hormones and growth factors.In this article,we will discuss the expression,localization and general characteristics of Periostin,and provide a review on the study of it in bone biology.

Alveolar bone changes around the natural teeth opposing the posterior implants in mandible / 대한치과보철학회지

STATEMENT OF PROBLEM: Alteration of tooth function is assumed to be changed by stress/strain on the adjacent alveolar bone, producing changes in morphology similar to those described for other load-bearing bones. When teeth are removed, opposing teeth will not be functioned. When edentulous area is restored by implant prostheses, opposing teeth will be received physiologic mechanical stimuli. PURPOSE: The aim of this study was to evaluate the bone changes around the teeth opposing implant restoration installed mandibular posterior area. MATERIAL AND METHOD: Eight patients who had mandibular posterior edentulous area were treated with implants. Radiographs of the opposing teeth were taken at implant prostheses delivery(baseline), 3 months, and 6 months later. Customized film holding device was fabricated to standardize the projection geometry for serial radiographs of opposing teeth. Direct digital image was obtained. Gray values of region of interest at each digital image were measured and compared according to time lapse. Repeated measured analysis of variance and post-hoc Scheffe's test were performed at the 95% significance level. RESULTS: Alveolar bone changes around the natural teeth opposing the posterior implant in mandible showed statistically significant difference compared to control group(P0.05). There were no statistically significant differences of alveolar bone changes among mesial-crestal group, mesial-middle group, distal-crestal group, distal-middle group, and control group(P>0.05). CONCLUSION: Alveolar bone around the natural teeth opposing the implant prosthesis showed gradual bony apposition.

Effects of Nanofiber Alignment and Strain Direction on Cellular Activities of Human ACL Fibroblasts / 대한정형외과연구학회지

PURPOSE: The effects of fiber alignment and direction of mechanical strain on the ECM generation of human ACL fibroblast were assessed. MATERIALS AND METHODS: The aligned nanofiber was fabricated using electrospinning with a rotating target. The amounts of collagen on aligned and randomly oriented structures were compared. To evaluate the effect of strain direction, 5% uniaxial strain (0.2 Hz) was applied to fibroblasts seeded on parallel aligned, vertically aligned to the strain direction, and randomly oriented nanofiber sheets. The amounts of collagen produced were measured 2 days after halting the strain application. RESULTS: The fibroblasts on the aligned nanofiber were spindle-shaped and oriented in the direction of the fibers. Significantly more collagen (22.5+/-2.7 ug/ngDNA) was synthesized on the aligned nanofiber than the randomly oriented (14.5+/-3.2 ug/ngDNA). And the amounts of collagen produced were increased by 150% and 50% approximately with the longitudinal and perpendicular cyclic strain, respectively. CONCLUSION: The aligned nanofiber scaffold used in this study constitutes a promising base material for tissue-engineered ligament in that it provides a more biomimetic structure, including the preferable mechanical environment.

The Effect of Nitric Oxide on Mechanical and Theraml Allodynia in Neuropathic Pain Model of Rat

BACKGROUND: Nitric oxide (NO) is known to play causative role in the development of neuropathic pain following peripheral nerve injury. However, it is yet to be investigated whether the role of NO differs in pain modalities, such as mechanical and thermal stimuli. Also, it has not been investigated whether NO has different roles in the stages of neuropathic pain - its development and maintenance. METHODS: Neuropathic pain was induced by a resection of the lumbar dorsal root 5, 6 (L 5, 6). After N-nitro-L-arginine methyl ester (L-NAME), an NO synthase inhibitor was injected intrathecally or locally around the dorsal root, we observed the behavioral response to the mechanical and thermal stimuli. RESULTS: Mechanical and thermal allodynia was inhibited by the application of L-NAME before the dorsal root injury. However, L-NAME did not affect the mechanical and thermal allodynia during the maintenance of neuropathic pain. CONCLUSIONS: We suggest that NO in the spinal cord or injured perineural site may play an important role in the induction of neuropathic pain, and may be associated with mechanical and thermal allodynia.

The Effect of Cyclic Compressive Strain on the Differentiation of Osteoblast-Like Cells (MC3T3-E1) in 3-D Scaffold / 대한정형외과연구학회지

We examined the effect of an applied cyclic compressive strain on the growth and differentiation of MC3T3-E1 cultured in a three-dimensional chitosan scaffold. The specially designed testing apparatus for mechanical stimulus was developed for uniaxial cyclic compressive strain. Cyclic compressive strain was applied over a period of 17 days with 150 cycles per day at a frequency of 0.5hz. Strain magnitude was 2.5% of the scaffold length. Control group and mechanically stimulated group were incubated and harvested at the indicated times. (day 3, 7, 10, 14, 17) The total amount of protein and alkaline phosphatase activity were examined. The total amount of protein of the control group was higher than that of the mechanically stimulated group. This was due to cell death for the nodule formation and calcium deposit of the mechanical stimuli group which resulted in cell differentiation. The alkaline phosphatase activity increased slightly in the control group. However, in the mechanical stimuli group, it increased significantly and reached its peak level on day 7 and subsequently its activity dropped to a level that was higher than the level at day 4(p < 0.05). Conclusively, it can be noted that the mechanical stimulus significantly accelerated the differentiation of MC3T3-E1 cells.