The Effects of Substrates and Hydrostatic Pressure on Differentiation of Mesenchymal Stem Cell / 대한정형외과연구학회지

PURPOSE: This study investigated the potential of dual differentiation of stem cells into osteo- and chodrogenesis depending on scaffold type even in the same environment. MATERIALS AND METHODS: For the part of the cartilage tissue section, MSCs were suspended in alginate solution and bead droplets were made using 23G syringe. For the bone tissue section, PCL/HA scaffolds were made using the bio-plotting system followed by seeding mesenchymal stem cells (MSCs) onto the scaffolds. Scaffolds with MSCs were cultured in cocktail media containing osteogenic and chondrogenic growth factors for up to 21 days. To provide mechanical environments which articular cartilage experiences in-vivo, intermittent hydrostatic pressure (IHP) was engaged. Various cellular responses were assessed: the quantitative analysis of DNA contents, GAG contents, ALP activities and immunofluorescence. RESULTS: We found that IHP promoted MSCs differentiation into the targeted cell types. That is, MSCs in alginate scaffolds were able to be differentiated into chondrocytes, while those onto PCL/HA scaffolds were able to be differentiated into osteoblasts. CONCLUSION: Depending on the scaffold characteristics MSCs can be differentiated into bone cells or chondrocytes. This technique can provide a cue for the treatment of osteochondral defects utilizing tissue engineering.

The Effects of Substrates and Hydrostatic Pressure on Differentiation of Mesenchymal Stem Cell / 대한정형외과연구학회지

PURPOSE: This study investigated the potential of dual differentiation of stem cells into osteo- and chodrogenesis depending on scaffold type even in the same environment. MATERIALS AND METHODS: For the part of the cartilage tissue section, MSCs were suspended in alginate solution and bead droplets were made using 23G syringe. For the bone tissue section, PCL/HA scaffolds were made using the bio-plotting system followed by seeding mesenchymal stem cells (MSCs) onto the scaffolds. Scaffolds with MSCs were cultured in cocktail media containing osteogenic and chondrogenic growth factors for up to 21 days. To provide mechanical environments which articular cartilage experiences in-vivo, intermittent hydrostatic pressure (IHP) was engaged. Various cellular responses were assessed: the quantitative analysis of DNA contents, GAG contents, ALP activities and immunofluorescence. RESULTS: We found that IHP promoted MSCs differentiation into the targeted cell types. That is, MSCs in alginate scaffolds were able to be differentiated into chondrocytes, while those onto PCL/HA scaffolds were able to be differentiated into osteoblasts. CONCLUSION: Depending on the scaffold characteristics MSCs can be differentiated into bone cells or chondrocytes. This technique can provide a cue for the treatment of osteochondral defects utilizing tissue engineering.

Fabrication of a Scaffold for Bone Regeneration and Differentiation of Mesenchymal Stem Cells / 대한정형외과연구학회지

PURPOSE: This in-vitro study aimed to confirm the clinical potential of a newly suggested bone substitute fabricated by a bio-plotting system. MATERIALS AND METHODS: A 3-dimensional, PCL (polycaprolactone)-based bone substitute was fabricated by a bio-plotting system, which enables us to control the shape and porosity. Mesenchymal stem cells(MSCs) from a New Zealand white rabbits were seeded to the bone substitute. Through 2-week experiment, morphological and various biological responses were assessed depending on the use of osteogenic media and/or mechanical stimuli. RESULTS: The viability of cells was confirmed. Other findings in relation to proliferation and differentiation were also confirmed to be biocompatible. Specifically, the activity of ALP was increased in the groups using osteogenic media along the time. And the expressions collagen type I was more affected by intermittent hydrostatic pressure rather than by osteogenic media. But those of Cbfa-1 was affected by osteogenic media and mechanical stimuli, as well. CONCLUSION: The potential of a newly fabricated and suggested material was confirmed. However, further long term and animal study are recommanded for the clinical application.

Precision Validation of Electromagnetic Physics in Geant4 Simulation for Proton Therapy / 의학물리

Geant4 (GEometry ANd Tracking) provides various packages specialized in modeling electromagnetic interactions. The validation of Geant4 physics models is a significant issue for the applications of Geant4 based simulation in medical physics. The purpose of this study is to evaluate accuracy of Geant4 electromagnetic physics for proton therapy. The validation was performed both the Continuous slowing down approximation (CSDA) range and the stopping power. In each test, the reliability of the electromagnetic models in a selected group of materials was evaluated such as water, bone, adipose tissue and various atomic elements. Results of Geant4 simulation were compared with the National Institute of Standards and Technology (NIST) reference data. As results of comparison about water, bone and adipose tissue, average percent difference of CSDA range were presented 1.0%, 1.4% and 1.4%, respectively. Average percent difference of stopping power were presented 0.7%, 1.0% and 1.3%, respectively. The data were analyzed through the kolmogorov-smirnov Goodness-of-Fit statistical analysis test. All the results from electromagnetic models showed a good agreement with the reference data, where all the corresponding p-values are higher than the confidence level alpha=0.05 set.

Effect of Tightening Torque on Abutment-Fixture Joint Stability using 3-Dimensional Finite Element Analysis / 대한치과보철학회지

STATEMENT OF PROBLEM: Loosening or fracture of the abutment screw is one of the common problems related to the dental implant. Generally, in order to make the screw joint stable, the preload generated by tightening torque needs to be increased within the elastic limit of the screw. However, additional tensile forces can produce the plastic deformation of abutment screw when functional loads are superimposed on preload stresses, and they can elicit loosening or fracture of the abutment screw. Therefore, it is necessary to find the optimum tightening torque that maximizes a fatigue life and simultaneously offer a reasonable degree of protection against loosening. PURPOSE: The purpose of this study was to present the influence of tightening torque on the implant-abutment screw joint stability with the 3 dimensional finite element analysis. MATERIAL AND METHODS: In this study, the finite element model of the implant system with external butt joint connection was designed and verified by comparison with additional theoretical and experimental results. Four different amount of tightening torques (10, 20, 30 and 40 Ncm) and the external loading (250 N, 30degrees C) were applied to the model, and the equivalent stress distributions and the gap distances were calculated according to each tightening torque and the result was analyzed. RESULTS: Within the limitation of this study, the following results were drawn; 1) There was the proportional relation between the tightening torque and the preload. 2) In case of applying only the tightening torque, the maximum stress was found at the screw neck. 3) The maximum stress was also shown at the screw neck under the external loading condition. However in case of applying 10 Ncm tightening torque, it was found at the undersurface of the screw head. 4) The joint opening was observed under the external loading in case of applying 10 Ncm and 20 Ncm of tightening torque. 5) When the tightening torque was applied at 40 Ncm, under the external loading the maximum stress exceeded the allowable stress value of the titanium alloy. CONCLUSION: Implant abutment screw must have a proper tightening torque that will be able to maintain joint stability of fixture and abutment.

An Unusual Case of Kinking Common Carotid Artery / 대한이비인후과학회지

An abnormal course of carotid artery may surprise surgeons during surgery and result in an transient ischemic attack or other ischemic symptoms. We report an unusual case of kinking in the common carotid artery located below the right thyroid lobe, which was found during a total thyroidectomy in a 74-years old patient. We emphasize in this case how important it is to palpate the neck before surgeries such as tracheostomy, thyroid surgery and so on.

The Study of the Regeneration of Nucleus Pulposususing Nanofiber-based Scaffold : In Vitro and Animal Study / 대한정형외과학회잡지

PURPOSE: To investigate the potential of nucleus pulposus (NP) regeneration with a nanofiber-based scaffold inserted in the degenerative disc. MATERIALS AND METHODS: A nanofiber scaffold was fabricated using an electrospinning technique. In the in-vitro study, a total 18 discs with endplates on both sides were obtained from six New Zealand White (NZW) rabbits. A small volume of NP was removed through the hole from the endplate. The specimens were classified into three groups, intact (normal), inserting nanofiber scaffold (nanofiber), and defect (defect) group. The discs were analyzed by MRI scan and histological analysis. Six NZW rabbits were used in the in-vivo study. An annulotomy was performed through the dorsal approach L2-3 and L3-4 disc. A nanofibrous sheet type scaffold was inserted at L3-4. X-ray, MRI and histology analysis were carried out at 4, 8, 12 weeks after surgery. RESULTS: In the in-vitro study, the Nanofiber groups showed higher signal intensity and cell proliferation than the defect groups. In the in-vivo study, the Nanofiber and defect groups showed significant degeneration but there was no significant difference between these groups. CONCLUSION: Nanofiber scaffold might provide a favorable environment for regenerating disc cells. However, a defect in the annulus fibrosus (AF) might delay the regeneration of the disc cell at the nanofiber group. Therefore, NP regeneration using any scaffold should be examined along with AF regeneration for effective clinical applications.

A Case of Reversible Posterior Leukoencephalopathy Syndrome during Methylprednisolone Pulse and Cyclophosphamide Therapy in a Child with Nephrotic Syndrome

The syndrome of reversible posterior leukoencephalopathy syndrome(RPLS) is characterized clinically by acute neurologic signs such as headache, vomiting, confusion, seizures, and visual abnormalities. Radiologically, abnormalities consistent with reversible white matter edema in the occipital and parietal lobes are characteristic. RPLS has often been associated with various systemic disorders, such as hypertensive encephalopathy, eclampsia, and the use of intravenous or intrathecal immunosuppressive drugs. We report a case of RPLS that occurred after intravenous steroid pulse therapy and treatment with oral cyclophosphamide in a child with nephrotic syndrome, and we emphasize the importance of early recognition of RPLS in the treatment of nephrotic syndrome and appropriate management to prevent permanent neurologic disability.

The Treatment of Liver Hemangioma Associated with Kasabach-Merritt Syndrome in Neonates

Hemangioma is the most frequent liver tumor in infancy. The treatment of hepatic hemangioma includes medical, surgical, and non-operative interventional therapy. There are no standard medical regimens currently considered consistently effective. MDMP (megadose methylprednisolone) and alpha-interferon can be used for medical treatment. Interventional occlusion of feeding arteries in symptomatic hepatic hemangioma is considered a safe and effective alternative to early open surgery. Untreated symptomatic patients with heart failure have a high mortality rate. For this reason symptomatic patients with heart failure may require non-operative treatment such as interventional embolization, because hepatic resection is burdened with high risk. We report our experiences of two patients with neonatal liver hemangiomas whose clinical courses were complicated by cardiac failure to whom medical treatment and/or interventional vascular occlusion were done. Both patients had Kasabach-Merritt syndrome complicated with cardiac failure. Initially, the masses were considered unresectable. In one case, we performed interventional therapy in addition to medical treatment. In another case, we tried medical therapy with megadose steroid and alpha-interferon. Unfortunately, in spite of the treatments, the patients died of severe hemorrhage.

Atopy and House Dust Mite Sensitization as Risk Factors for Asthma in Children

Asthma is commonly described as an atopic disease in childhood, but some cases of this disorder do not fit this description. The aim of this study was to evaluate the frequency of atopy, asthma, and sensitization to house dust mites in children with allergic symptoms. This study was performed at the Severance Hospital of Yonsei University with patients who visited the allergy clinic for evaluation of nonspecific upper respiratory symptoms, typical symptoms of asthma, or a general health workup. The patients were divided into three age groups: 0-3 years (group 1), 4-7 years (group 2), and 8-12 years (group 3). Of the 1, 244 children examined, 844 (67.8%) were atopic and 400 (32.2%) were non-atopic. The frequency of atopy and asthma increased with age. Asthma was diagnosed in the same proportion (64%) of atopic and non-atopic children. As risk factors for asthma symptoms, the positive values of house dust mite (HDM) sensitivity were significantly increased in groups 1, 2, and 3 to 53.5%, 68.9%, and 80.2%, respectively. A significant difference between the percentage of asthmatics sensitized to HDM and that of asthmatics not sensitized to HDM was found only in group 3. In conclusion, asthma is related to atopy with increasing age, and house dust mite sensitization seems to be an important determinant of asthma in older children in Korea.