Ho Yun Chung

Different effects of PLGA and chitosan scaffolds on human cartilage tissue engineering.

Clinical application of the cartilage formed by tissue engineering is not practical due to the failure to maintain long-term tissue structural integrity. One of the important factors for maintaining integrity is the biomaterial for a scaffold. The purpose of the current study was to evaluate the difference between poly-lactic glycolic acid (PLGA) and chitosan as scaffolds. Human auricular chondrocytes were used. Chondrocyte-scaffold complexes were implanted in nude mice and analyzed at 4, 8, 12, 16, and 24 weeks after implantation. The volume of chondrocyte-PLGA complexes decreased rapidly. The volume of chondrocyte-chitosan complexes was well maintained with a slow decrease rate. In histological findings, mature cartilage was formed by 4 weeks in the PLGA group. However, cartilage structure was hardly found after 16 weeks. In the chitosan group, mature cartilage was detected at 8 weeks and cartilage formation became more marked with time. The expression of type II collagen protein and mRNA became weaker with time in the PLGA group. However, the expression in the chitosan group was strong for the whole period. These results suggest that chitosan is a superior scaffold for cartilage tissue engineering in terms of the maintenance of structural integrity. It is expected that after some modification for more rapid chondrogenesis, chitosan scaffolds may become one of the most useful scaffolds for cartilage tissue engineering.

The effects of botulinum toxin A on the survival of a random cutaneous flap

BACKGROUND Although interest in flap surgery has increased, a satisfactory research study on supportive drugs or methods for flap surgery has not been seen in the literature thus far. Despite several studies using botulinum toxin A for flap surgery being reported, their efforts to clarify the mechanisms are not sufficient. Therefore, the authors have studied the effect of botulinum toxin A on random cutaneous flap survival in a rat model under the hypothesis that it affects the microvascular system. METHOD Thirty 10-week-old Sprague-Dawley rats were divided into experimental (n=15) and control groups (n=15). The experimental group used 1.5 IU (International Units) of botulinum toxin A, and the control group used normal saline. A 2x8 cm random cutaneous flap was designed on the rats and then elevated. Normal saline (0.05 cc) and 1.5 IU of botulinum toxin A (0.05 cc) (Botox, Allergan, USA) were injected into the dermis layer of the central portion in the proximal one-third of the flap. Gross photographs were taken at days 1, 3, 5 and 7 after the operation. Laser-induced fluorescein fluoroscopy was performed on postoperative day 7 and tissues were retrieved for histological analysis. In addition, reverse transcriptase polymerase chain reaction (RT-PCR) was carried out for quantitative analysis. RESULTS Gross photos and laser-induced fluorescein fluoroscopy reveal the survival rate of the Botox group was 8.3% higher than the control. In the histologic study, the diameter of vessels is larger and the number of immature vessels is more in the Botox group. The result of RT-PCR shows increased expression of VEGF (vascular endothelial growth factor), CD 31 (PECAM1, platelet/endothelial cell adhesion molecule) and iNOS (inducible nitric oxide synthase), which are considered to be related to vasodilation and endothelial proliferation. CONCLUSION Our results suggest that botulinum toxin A increases the survival rate of random cutaneous flaps by means of selective suppression of sympathetic neurons of the cutaneous microcirculation system.

The bone regenerative effect of chitosan microsphere-encapsulated growth hormone on bony consolidation in mandibular distraction osteogenesis in a dog model.

The purpose of this project was to study the effect of chitosan microsphere-encapsulated human growth hormone, which causes sustained release of chitosan and human growth hormone after implantation on early bony consolidation in distraction osteogenesis of a canine model. Forty-eight dogs were used for this study. An external distraction device was applied to the mandibular body after a vertical osteotomy, and the mandibular distraction was started 5 days after the operation at a rate of 1 mm/d up to a 10-mm distraction. The experimental group was divided into a control group (I), hyaluronic acid group (II), chitosan microsphere group (III), and chitosan microsphere-encapsulated human growth hormone group (IV). Normal saline was injected in group I. In group II, a 1-ml volume of hyaluronic acid solution was injected into the distracted area. In the group III, powder of chitosan microspheres and hGH were mixed with a 1-ml volume of hyaluronic acid to make an injectable form, and it was implanted into the distracted area. In group IV, powder of chitosan microsphere-encapsulated hGH was mixed with a 1-ml volume of hyaluronic acid. A total of 1-ml volume of the solution mix was implanted into the distracted area. Five dogs in each group (total of 20 dogs) were killed 3 weeks after completion of distraction. Twenty-eight dogs were killed at 6 weeks. Bone mineral density was 13.1% of the contralateral normal mandible at 3 weeks and 29.6% at 6 weeks in group I, 16.4% at 3 weeks and 40.4% at 6 weeks in group II, 16.6% at 3 weeks and 45.95% at 6 weeks in group III, and 29.6% at 3 weeks and 66.7% at 6 weeks in group IV. The mean three-point failure load was 16.1% in the control group, 34.7% in group II, 41.5% in group III, and 52.1% in group IV compared with the intact contralateral mandible, with statistical significance. In the histological findings, new bone was generated in all groups. In group IV, the formation of active woven bone was observed throughout the distracted area at 6 weeks. The amount of new bone formation in the distracted zone was in the order of group IV, group III, group II, and the control group. In conclusion, these findings suggest that chitosan microsphere-encapsulated hGH seems to be quite effective in early bone consolidation in distraction osteogenesis.

Platelet-Rich Plasma: Quantitative Assessment of Growth Factor Levels and Comparative Analysis of Activated and Inactivated Groups

BACKGROUND Platelet-rich plasma (PRP) has more concentrated platelets than normal plasma (approximately 150-400×10(3) cell/dL). Platelets excrete several growth factors and cytokines that are associated with the healing and regeneration process. However, even though PRP is widely used, the mechanism or actual effect is presently unclear. Therefore, this study was performed to investigate the levels of growth factors and platelet concentration rate. METHODS Autologous blood for preparing PRP was obtained from healthy subjects aged 25 to 35 years. The samples were divided into 4 experimental groups (inactivated whole blood, inactivated PRP, activated whole blood with thrombin and calcium chloride, and activated PRP). The platelet counts in the blood were analyzed and the growth factors were quantitatively measured. A statistical analysis was performed by using Dunns multiple comparison test. RESULTS In the blood cell analysis, the platelet count of the PRP group was approximately 4.25 times higher than that of the whole blood group. In the quantitative analysis of growth factors, the platelet-derived growth factor (PDGF)-AB, PDGF-BB, and transforming growth factor-β of the inactivated and activated PRP groups were higher than those of the inactivated and activated whole blood groups (P<0.05). CONCLUSIONS In this study, the platelet count and the levels of PDGF-AB and PDGF-BB in the PRP were determined. Further, more research is required on the bioactivity level of the growth factors secreted during the process of PRP preparation and the potency of growth factors that can be exerted physiologically in vivo.

Current Concepts in the Mandibular Condyle Fracture Management Part II: Open Reduction Versus Closed Reduction

In the treatment of mandibular condyle fracture, conservative treatment using closed reduction or surgical treatment using open reduction can be used. Management of mandibular condylar fractures remains a source of ongoing controversy in oral and maxillofacial trauma. For each type of condylar fracture,the treatment method must be chosen taking into consideration the presence of teeth, fracture height, patientsadaptation, patients masticatory system, disturbance of occlusal function, and deviation of the mandible. In the past, closed reduction with concomitant active physical therapy conducted after intermaxillary fixation during the recovery period had been mainly used, but in recent years, open treatment of condylar fractures with rigid internal fixation has become more common. The objective of this review was to evaluate the main variables that determine the choice of an open or closed method for treatment of condylar fractures, identifying their indications, advantages, and disadvantages, and to appraise the current evidence regarding the effectiveness of interventions that are used in the management of fractures of the mandibular condyle.

The bone regenerative effect of growth hormone on consolidation in mandibular distraction osteogenesis of a dog model.

The purpose of this project was to study the effect of growth hormone on early bony consolidation in distraction osteogenesis of a dog model. Sixteen dogs were used for this study. The vertical osteotomy on the mandibular body was extended downward. An external distraction device was applied to the mandibular body and the mandibular distraction was started 5 days after the operation at a rate of 1 mm/d up to a 10-mm distraction. The experimental group was divided into a control group and growth hormone group. Dogs in the growth hormone group received a daily subcutaneous injection of 100 &mgr;g (1 IU) of recombinant human growth hormone per kilogram of body weight. The daily administration of growth hormone was performed from the day of the osteotomy through the whole distraction period to the sacrifice. Normal saline was injected in the control group. Eight dogs were allocated to each group. Two dogs in each group, a total of four dogs, were killed at 2 weeks after completion of distraction, four dogs were killed at 4 weeks, and the other eight dogs were killed at 6 weeks. The level of serum IGF-I in the growth hormone group was elevated and peaked between 8 days and 12 days after systemic administration of growth hormone. Bone mineral density was higher in the growth hormone group and lower in the control group for the whole period. Bone mechanical strength was 300% higher in the growth hormone group than in the control group. However, results were more suggestive than conclusive. On histological examination, the formation of a substantial amount of active woven bone was observed throughout the distracted zone at six weeks in the growth hormone group. In the control group, new bone was generated from the edge to the center of the distracted zone. In addition, most of the central area of the distracted zone was filled with fibrous tissue at six weeks. In conclusion, these findings suggest that growth hormone appears to be effective in early bony consolidation in distraction osteogenesis.

Usefulness of Oncoplastic Volume Replacement Techniques after Breast Conserving Surgery in Small to Moderate-sized Breasts

Background In Korean women, many of whom have small to moderate-sized breasts, it is difficult to cover a partial breast defect using oncoplastic volume displacement techniques after removal of an adequate volume of tissue during oncologic surgery. In such cases, oncoplastic volume replacement techniques are more useful. Methods From January 2007 to December 2011, 104 women underwent a total of 107 breast-conserving surgeries with various kinds of oncoplastic volume replacement techniques. We used latissimus dorsi (LD) myocutaneous flap for cases in which the resection mass was greater than 150 g. In case with a resection mass less than 150 g, we used regional flaps such as a lateral thoracodorsal flap, a thoracoepigastric flap, or perforator flaps such as an intercostal artery perforator (ICAP) flap or a thoracodorsal artery perforator (TDAP) flap. Results The mean age was 46.1 years, and the average follow-up interval was 10.3 months. The patients underwent oncoplastic volume replacement techniques with a lateral thoracodorsal flap (n=9), thoracoepigastric flap (n=7), ICAP flap (n=25), TDAP flap (n=12), and LD flap (n=54). There was one case of congestion in an LD flap, and two cases of fat necrosis in an ICAP flap. Most of the patients were satisfied with the cosmetic results. Conclusions Oncoplastic volume replacement techniques can be reliable and useful for the correction of breast deformity after breast-conserving surgery, especially in patients with small to moderate-sized breasts.

The usefulness of oncoplastic volume displacement techniques in the superiorly located breast cancers for Korean patients with small to moderate-sized breasts.

Because the average breast size of Korean women is not as large as that of western women, it is not so easy to apply the oncoplastic volume displacement technique. However, we have tried to use volume displacement techniques that work well with small-breasted women. In this study, we report the usefulness of displacement techniques in the superiorly located cancers with small- to moderate-sized breasts. Between September 2006 and August 2009, 58 women were treated for superiorly located cancers. All patients who were selected had small- to moderate-sized breasts and small to moderate breast defects. They were divided into 3 groups. The groups were spilt based on the distance from the nipple-areolar complex, which are as follows: near, intermediate, and far. Their mean age was 46 and the average follow-up interval was 21 months. Median weight of the specimen on the tumor side was 84 g (range, 29–140 g). The various surgical techniques used were the “round block” technique (n = 8) and “batwing mastopexy” (n = 4) for near lesions; “tennis racket” method (n = 32) and “rotational flap” (n = 8) for intermediate lesions; and “parallelogram mastopexy lumpectomy” (n = 6) for far lesions. There were 4 complications (nipple-areolar complex partial necrosis, radiation burn, and 2 wound dehiscence). No local recurrences have been observed and a majority of the patients were satisfied with cosmetic results. Oncoplastic volume displacement techniques in superiorly located breast cancers for Korean patients with small- to moderate-sized breast are reliable and should be considered in the case of breast conserving surgery (BCS).

Surgical treatment of ossified cephalhematoma.

Cephalhematoma is a collection of blood beneath the periosteum of the bones in the cranial vault. The treatment strategy of most cephalhematoma is conservative. However, in cases of ossified cephalhematoma causing deformities of skull, surgical management is indicated. From 1996 to 2002, the authors treated three cases of ossified cephalhematoma with the suggested pathogenesis of ossification, which cephalhematoma goes to ossification process, rather than calcification. Surgical treatment, which is bony shaving with a burr on the irregular margin site, was performed in one case in which the thickness of the skull in the bulging area was the same as in the normal area in preoperative computed tomography (CT) scan, and a depression did not exist in the operative field. In two cases in which there was any difference in bony density in the preoperative CT scan and depression after removal of cephalhematoma, the bony cap was remodeled into multiple pieces and the depressed region was reconstructed with a remodeled bone cap as an onlay bone graft. There was no evidence of complications and recurrence, and there was good reconstitution of the skull contour in all cases.

Effect of Amniotic Fluid Stem Cells and Amniotic Fluid Cells on the Wound Healing Process in a White Rat Model

Background Amniotic-fluid-derived stem cells and amniocytes have recently been determined to have wound healing effects, but their mechanism is not yet clearly understood. In this study, the effects of amniotic fluid stem cells and amniocytes on wound healing were investigated through animal experiments. Methods On the back of Sprague-Dawley rats, four circular full-thickness skin wounds 2 cm in diameter were created. The wounds were classified into the following four types: a control group using Tegaderm disc wound dressings and experimental groups using collagen discs, amniotic fluid stem cell discs, and amniocyte discs. The wounds were assessed through macroscopic histological examination and immunohistochemistry over a period of time. Results The amniotic fluid stem cell and amniocyte groups showed higher wound healing rates compared with the control group; histologically, the inflammatory cell invasion disappeared more quickly in these groups, and there was more significant angiogenesis. In particular, these groups had significant promotion of epithelial cell reproduction, collagen fiber formation, and angiogenesis during the initial 10 days of the wound healing process. The potency of transforming growth factor-β and fibronectin in the experimental group was much greater than that in the control group in the early stage of the wound healing process. In later stages, however, no significant difference was observed. Conclusions The amniotic fluid stem cells and amniocytes were confirmed to have accelerated the inflammatory stage to contribute to an enhanced cure rate and shortened wound healing period. Therefore, they hold promise as wound treatment agents.