Andac Aykan

Biomechanical analysis of the effect of mesenchymal stem cells on mandibular distraction osteogenesis.

BackgroundThe purpose of this study was to investigate the effects of bone marrow–derived stem cells on consolidation period by using a new biomechanical testing method on sheep mandible model. MethodsEight sheep underwent bilateral mandibular osteotomies. After latency period, bone distraction was activated. Mesenchymal stem cells were transplanted into the gap of the left mandibular distracted callus on the first day of consolidation period. The sheep were then randomly divided into 2 groups (group A = 4, group B = 4). Group A and group B animals were killed on the third and sixth weeks of consolidation, respectively. Fracture pattern and localization, bone regeneration ratio and density, and stress distribution of 16 distracted hemimandibles were evaluated by computed tomography and biomechanical analysis. ResultsTwo different fracture patterns were observed in the 2 groups. The left halves of mandibles exhibited horizontal fracture out of the distraction zone, and the cross-sectional area was compact bone [H (−) C], whereas the fracture patterns of control sides were oblique, which passed through the distraction zone with a propensity of trabecular bone [O (+) T]. Stress distribution at the critical cross-section of distraction region was not different in halves of mandibles. However, bone regeneration ratios and regenerated bone densities were significantly higher in left sides (P < 0.05). ConclusionsTransplantation of mesenchymal stem cells promotes maturity of the distracted callus. The new experimental model, which allowed to test the mandible as a system by simulating in vivo loading conditions, revealed differences in the mechanical behavior of the halves of mandible.

Native extracellular matrix/fibroin hydrogels for adipose tissue engineering with enhanced vascularization

Adipose tissue engineering is a promising field for regeneration of soft tissue defects. However, vascularization is needed since nutrients and oxygen cannot reach cells in thick implants by diffusion. Obtaining a biocompatible scaffold with good mechanical properties is another problem. In this study, we aimed to develop thick and vascularized adipose tissue constructs supporting cell viability and adipose tissue regeneration. Hydrogels were prepared by mixing rat decellularized adipose tissue (DAT) and silk fibroin (Fib) at different v/v ratios (3:1, 1:1 and 1:3) and vortexing. Gelation times decreased with increasing fibroin ratio Among hydrogel groups 1:3-DAT:Fib ratio group showed similar mechanical properties with adipose tissue. Both pre-adipocytes and pre-endothelial cells, pre-differentiated from adipose derived stem cells (ASCs), were encapsulated in hydrogels at a 1: 3 ratio. In vitro analyses showed that hydrogels with 1:3 (v/v) DAT:Fib ratio supported better cell viability. Pre-adipocytes had lipid vesicles, and pre-endothelial cells formed tubular structures inside hydrogels only after 3 days in vitro. When endothelial and adipogenic pre-differentiated ASCs (for 7 days before encapsulation) were encapsulated together into 1:3-DAT:Fib hydrogels both cell types continued to differentiate into the committed cell lineage. Vascularization process in the hydrogels implanted with adipogenic and endothelial pre-differentiated ASCs took place between the first and second week after implantation which was faster than observed in the empty hydrogels. ASCs pre-differentiated towards adipogenic lineage inside hydrogels had begun to accumulate lipid vesicles after 1 week of subcutaneous implantation Based on these results, we suggest that 1:3-DAT:Fib hydrogels with enhanced vascularization hold promise for adipose tissue engineering.

Our experiences on the reconstruction of lateral scalp burn alopecia with tissue expanders

INTRODUCTION Cicatricial alopecia is a form of hair loss that causes both cosmetic and psychological concerns. Although tissue expanders are the common approach to reconstruction, no algorithm exists in the literature for this process. In this study, it was aimed to create an algorithm for the reconstruction of lateral scalp alopecias with the goal to achieve better and standardized results. MATERIALS AND METHODS Lateral scalp alopecias were divided into three groups: total lateral alopecia (type I), temporal and sideburn alopecia (type II), and sideburn alopecia (type III). Tissue expanders were placed at the parieto-occipital area in type I defects, parietal area in type II defects, and the temporal region in type III defects. Tissue expanders were used to create flaps that were advanced with 60° rotation, 90° rotation, and no rotation for type I, II, and III defects, respectively. RESULTS Fifteen patients were treated with this algorithm. Using this simple approach, we achieved natural, standardized aesthetic results for each patient, all of whom were satisfied with the final results. CONCLUSION Although the number of case were limited, the ideal and standardized cosmetic results could be obtained by this approach.

Total lower eyelid reconstruction with superficial temporal fascia flap and porous polyethylene implant: A case report

Total reconstruction of the eyelid after serious periorbital injury is a challenging procedure for plastic and reconstructive surgery. Although several methods have been used for reconstructing the eyelids, such as advancement flap with fascia lata sling, island mucochrondrocutaneous flap, prefabricated temporal island flap, porous polyethylene and superficial temporal fascia flap, creating a supportive eyelid for housing an artificial eye without complication is still an ongoing problem. In the case presented, superficial temporal fascia flap with porous polyethylene was used for the reconstruction of total lower eyelid.

The Effects of Hydrogen Sulfide on Adipocyte Viability in Human Adipocyte and Adipocyte-Derived Mesenchymal Stem Cell Cultures Under Ischemic Conditions.

BackgroundThis study evaluated the in vitro effects of hydrogen sulfide on adipocyte survival under ischemic conditions and explored possible mechanisms of its apoptotic process. MethodsThe mesenchymal stem cell culture was prepared from a human subcutaneous adipose tissue sample. Adipose-derived mesenchymal stem cells were differentiated into the adipogenic direction, and a mature adipocyte culture was obtained. The adipose-derived mesenchymal stem cell and mature adipocyte cultures were both divided into 6 groups. Sodium hydrogen sulfide was used as a hydrogen sulfide donor. After treating the groups with sodium hydrogen sulfide (0, 0.1, 1, 10, 100, and 1000 &mgr;M), the cell cultures were incubated in 1% oxygen at 37°C for 24 hours. After the ischemia period, the cell culture groups were evaluated with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test for the proliferation/cytotoxicity rates, flow cytometry for apoptosis and necrosis rates, and reverse transcriptase polymerase chain reaction for apoptotic (Bax, Caspase-3) and antiapoptotic (Bcl-2) gene expression levels. ResultsStatistically significant increases in proliferation rates were found in mesenchymal stem cell groups treated with low dose (0, 1, and 1 &mgr;M) sodium hydrogen sulfide (P < 0.05). For each dose, a statistically significant decrease was found in late apoptosis levels on the mature adipocyte cultures (P < 0.05). In both cell culture groups, Bcl-2 gene expression was increased and Caspase-3 gene expression was decreased. ConclusionsUnder ischemic conditions, hydrogen sulfide has a protective effect on mesenchymal stem cells and mature adipocytes, and this effect is mediated by the elevation of antiapoptotic gene expression.

Nevus sebaceus with basal cell carcinoma, poroma, and verruca vulgaris

Nevus sebaceus (NS) is a congenital, benign, hamartomatous lesion and it is possible to see several benign or malignant tumors accompanying it. One of these is the poroma, which is very rare, and has only been reported twice before, in the English literature. In this paper, we presented two new cases of NS. One of them was a 40-year-old male who presented with a congenital skin lesion on his temporoparietal region. This lesion was composed of four different lesions, including NS, poroma, basal cell carcinoma (BCC), and verruca vulgaris. The second patient was a 41-year-old male presenting with a yellow-brown patch on the scalp. This lesion was comprised of NS and BCC. In addition to these presentations, we discussed the differential diagnosis between BCC and trichoblastoma, both of which are likely to be seen with NS. For this purpose, we recommended an immunohistological panel, which may be useful for differentiating these two morphologically similar lesions.

Mandibular distraction osteogenesis with newly designed electromechanical distractor.

Background The purposes of this study were to design a fully automatic electromechanical distractor for continuous mandibular distraction osteogenesis and to investigate the efficacy of this newly developed distractor on sheep mandible model. Methods Five sheep underwent unilateral mandibular osteotomy, and the mechanical component of electromechanical distractor was fixed on both sides of the osteotomy site using pins. After a 5-day latency period, the electromechanical distractor was activated at a rate of 0.30 mm per 8 hours using an electronic control unit. The bone was lengthened for 20 days without any intervention to the electromechanical distractor. The animals were killed on the sixth week of the consolidation period, and 5 distracted mandibles were examined through macroscopic observation and computed tomography. Distracted bone length was measured through computed tomography on sagittal slices. Results The device was tolerated by the distraction process without complications in all animals. New callus formation was observed on the distraction gap. Radiologic evaluation showed new callus formation in the distraction gap. New callus length was found to be, in average, 18.28 mm. Conclusions In this preliminary study, a newly designed electromechanical distractor was successfully used for mandible distraction, which mainly provided a continuous lengthening during activation period spontaneously without any intervention. We think that the clinical application of this electromechanic distractor may provide patient comfort during distraction. Moreover, electromechanical distractor has the potential for high-resolution movement capacity when compared with annual distraction. The promising results from this prototype are encouraging to further investigations for human applications.

Hemangioma of the Zygomatic Bone.

Benign masses arising from facial bones have been reported several times in the literature. Hemangiomas are one of the uncommon benign tumors. In this study, the authors aimed to present a rare patient of zygomatic intraosseos hemangioma and their management. A 40-year-old woman with a mass in her left lateral cantus admitted to our clinic. Preoperative computed tomography and magnetic resonance imaging revealed an osseos mass in her left zygoma. The authors conclude that it should be kept in mind that although they are very rare benign tumors, intraosseos hemangiomas can cause facial masses. Meticulous radiologic examination can give important clues for differential diagnosis before the surgery.

Reconstruction of the one-digit foot with an osteocutaneous fibula flap: a case report.

The decision to amputate or reconstruct after high-energy foot injuries is controversial. A 25-year-old male patient was admitted to our clinic with a complex injury to his left foot sustained during a mine explosion, and the second to fifth digits and metatarsals of the left foot had been traumatically amputated before admission to our facility. The complex left foot defect was reconstructed with an osteocutaneous fibula flap during a single session. An osteotomy was performed on the bone segment of the flap, and both lateral longitudinal and transverse arches were repaired. Both aesthetic and functional outcomes were very satisfactory, including independent ambulation, light jogging, and full performance of activities of daily living without limitation. Many factors, including comorbidities, should be considered during the decision-making process of amputating or reconstructing complex foot injuries.

Free fibular flap vascular pedicle calcification.

Osseous free flaps are major reconstruction choices of the segmental mandibular defects. However, etiology of defects in mandible is variable; tumor-related surgery, trauma, radiation, or congenital anomalies are the most common causes. The advent of microvascular surgery has achieved the reconstruction of complex mandibular defects. The options for bony free-tissue transfer for mandibular reconstruction primarily depend on the fibula, iliac, scapula, and radius bone. The free fibular flap continues to be first choice in the reconstruction of mandibular defects because of its advantages. In this report, rare complication of vascular pedicle calcification after mandibular reconstruction with free fibular flap is presented.