Total Surface Area of a Through-and-Through Oromandibular Defect Is Associated With Thromboembolic Events for Reconstruction With a Single Fibula Free Flap.

BACKGROUND: Reconstruction of through-and-through composite oromandibular defects (COMDs) has been a challenge to plastic surgeons for decades. When using a free osteoseptocutaneous fibular flap, the skin paddle is restricted by the orientation of the peroneal vessels and the inset of bone segment(s). Although the combination of double flaps for extensive COMDs is viable and reliable, the decision of single- or double-flap reconstruction is still debated, and the risk factors leading to complications and flap failure of single-flap reconstruction are less discussed. AIM AND OBJECTIVES: The aim of this study was to determine objectively predictive factors for postoperative vascular complications in through-and-through COMDs reconstructed with a single fibula flap. METHODS: This was a retrospective cohort study in patients who underwent single free fibular flap reconstruction for through-and-through COMDs in a tertiary medical center from 2011 to 2020. The enrolled patients' characteristics, surgical methods, thromboembolic event, flap outcomes, intensive care unit care, and total hospital length of stay were analyzed. RESULTS: A total of 43 consecutive patients were included in this study. Patients were categorized into a group without thromboembolic events (n = 35) and a group with thromboembolic events (n = 8). The 8 subjects with thromboembolic events were failed to be salvaged. There was no significant difference in age, body mass index, smoking, hypertension, diabetes mellitus, and history of radiotherapy. The length of bony defect (6.70 ± 1.95 vs 9.04 ± 2.96, P = 0.004) and the total surface area (105.99 ± 60.33 vs 169.38 ± 41.21, P = 0.004) were the 2 factors that showed a significant difference between the groups. Total surface area was the only significant factor in univariate logistic regression for thromboembolic event (P = 0.020; odds ratio, 1.02; 95% confidence interval [CI], 1.003-1.033) and also in multivariate logistic regression analysis after adjusting confounding factors (P = 0.033; odds ratio, 1.026; 95% CI, 1.002-1.051).The cutoff level of total surface area in determining thromboembolic event development was 159 cm2 (P = 0.005; sensitivity of 75% and specificity of 82.9%; 95% CI, 0.684-0.952). CONCLUSIONS: Free fibula flap has its advantages and drawbacks on mandible restoration. Because there is a lack of indicators before, a large total surface area may be an objective reference for single-flap reconstruction of through-and-through COMDs due to an elevated risk of thromboembolic event.

Fabrication of quantum dot-conjugated collagen/hyaluronic acid porous scaffold.

A quantum dot (QD)-conjugated collagen-hyaluronic acid (HA) porous scaffold was combined with our previously reported animal model of mice inferior epigastric flaps and QD infusion to study scaffold angiogenesis. A CdSe/ZnS QD-labeled collagen/HA scaffold was fabricated and examined with a confocal microscope. The degradation rate of the scaffold was inversely related to 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide concentration used in cross-linking. There was no cytotoxicity of the QDs as determined by MTT colorimetric assay. Results of the animal implantation study revealed no difference in acute tissue inflammation between scaffolds with or without QD labeling. To study scaffold angiogenesis, we infused the implanted QD-conjugated collagen/HA scaffold with QD of different fluorescence, which can be simultaneously identified by confocal microscope. By these evaluations, we conclude that QD-conjugated collagen/HA porous scaffold is not different from that without conjugation and can be used in our animal model of scaffold angiogenesis without compromising results.

In vivo angiogenesis effect of porous collagen scaffold with hyaluronic acid oligosaccharides.

BACKGROUND: Tissue engineering is a promising solution for tissue defect repair. A key problem, however, is how to keep the engineered tissue alive after implantation. The ideal scaffold for tissue engineering would be biocompatible and biodegradable and, more importantly, would exhibit good interaction with endothelial cells to promote angiogenesis. MATERIALS AND METHODS: Three different scaffolds were synthesized: collagen/hyaluronic acid (HA) (MW 6.5K), collagen/HA (MW 220K), and collagen only. The synthesized collagen/HA scaffold was analyzed for water content, pore size, and HA content. An animal model for in vivo tissue construct angiogenesis was developed using the inferior epigastric skin flap of mice and perfusion of quantum dots; the average fluorescence intensity per unit area was calculated and correlated with vessel density from histologic examination. RESULTS: The pore size is not statistically different among the three groups and the HA content is not statistically different between the two collagen/HA groups. The fluorescence intensity of the collagen/HA (MW 6.5K) group is increased at day 14, 21, and 28, and is significantly higher than in the other groups. Similar results were also obtained from histologic immunohistochemistry studies. CD31-stained vessels were found co-localized with QD fluorescence and these newly formed vessels were identified at day 14 in the collagen/HA (MW 6.5K) group and increased significantly at day 21 and 28. CONCLUSION: This study showed that collagen scaffolds with short-chain HA (MW 6.5K) revascularize faster than those with long-chain HA (MW 220K) and collagen only. The results of the new animal model for studying scaffold angiogenesis are compatible with the conventional methods of immunostaining and histological examination.

Decellularized porcine coronary artery with adipose stem cells for vascular tissue engineering.

BACKGROUND: Decellularized xenogenic vascular tissue has potential applications in small-diameter tissue engineering vascular grafts. Decellularization removes most xenogenic antigen and leaves most of the extracellular matrix for cell adhesion, migration and proliferation. Recellularization is recognized as an important step to improve the endothelialization of decellularized vascular grafts in vivo and most studies used endothelial cells for recellularization. However, there have been no studies on applying undifferentiated adipose stem cells (ASCs) in recellularization. MATERIAL AND METHODS: In this study, we evaluated the feasibility of decellularized porcine coronary artery (DPCA) with ASC recellularization as tissue-engineered vascular grafts by in vitro cell biocompatibility and in vivo aorta repair tests. Porcine coronary artery was decellularized with the enzyme-detergent method and characterized by histology and biochemical methods. In vitro biocompatibility was tested by human and rat adipose stem cells (hASCs/rASCs). In vivo, potential for endothelialization of ASC-seeded DPCA scaffolds were evaluated by rat aorta patch repair model. RESULTS: In vitro, hASCs and rASCs could adhere and maintain cell viability on DPCA scaffold. In vivo, rat abdominal aorta repair model revealed that DPCA with rat ASC seeding had a 100% patency rate. Grossly, there was integration between host tissue and graft tissue, and no leakage or rupture was observed. Histologically, DPCA with rat ASC seeding displayed endothelialization on the luminal side. In addition, the layer structure was preserved with collagen deposition. However, intimal hyperplasia was noted. CONCLUSION: This preliminary study indicates that DPCA with undifferentiated ASC seeding exhibited cell biocompatibility in vitro and endothelialization in vivo. DPCA with ASC recellularization has potential for use in the development of small-diameter tissue engineering vascular grafts.

The use of "composite dressing" for covering split-thickness skin graft donor sites.

To evaluate the effect of a new dressing method for clean wound coverage, two kinds of dressing materials are combined together to cover nine wounds in nine patients. All the wounds are split-thickness skin graft donor sites located in the anterior thighs. The size of the wounds ranges from 6 cm x 4 cm to 10 cm x 8 cm (42 cm(2) on average). A central fenestration is created in the polyurethane film layer for draining the wound discharge, and a piece of 2.5 cm x 2.5 cm carboxymethyl cellulose dressing is fixed on top of the fenestration for protecting the underlying wound. Dry gauze is used to cover the composite dressing, which is replaced daily. The wound condition is checked and recorded everyday until the patient is discharged. Further management and follow-up for the wound is performed at the outpatient department or by telephone. All wounds healed smoothly on the postoperative 6th to 7th day. No wound infection was noted, including one patient who had diabetes mellitus. Five patients responded to follow-up for at least 5 months and no hypertrophy scar formation was noted. From clinical experiences, we know that this new method is practical and cost-effective for covering small-sized, split-thickness skin graft donor-site wounds.

Culturing adult human bone marrow stem cells on gelatin scaffold with pNIPAAm as transplanted grafts for skin regeneration.

Skin tissue engineering is a possible solution for the treatment of extensive skin defect. The ultimate goal of skin tissue engineering is to restore the complete functions of native skin, but until now the structures and functions of skins are only partially restored. By negative immunoselection (CD45 and glycophorin A), we isolated and cultivated adult human bone marrow stem cells (hBMSCs) that are of multilineage differentiation potential. In this study, we first demonstrated that by using gelatin/thermo-sensitive poly N-isopropylacrylamide (pNIPAAm) and the immunocompromised mice model, the hBMSCs possess the differentiation potential of epidermis and the capability of healing skin wounds. The in vitro observations and the results of the scanning electron microscope showed that the hBMSCs can attach and proliferate in the gelatin/thermo-sensitive pNIPAAm. To further monitor the in vivo growth effect of the hBMSCs in the skin-defected nude mice, the green fluorescence protein (GFP) gene was transduced into the hBMSCs by the murine stem cell viral vector. The results showed that the rates of cell growth and wound recovery in the hBMSC-treated group were significantly higher than those in the control group, which was only treated with the gelatin/pNIPAAm (p < 0.01). More importantly, the re-epithelialization markers of human pan-cytokeratin and E-cadherin were significantly increased on day 7, day 14, and day 21 after the hBMSC-scaffold with the pNIPAAM in the mice with skin defects (p < 0.05). Moreover, the stem cell markers of human CD13 and CD105 were gradually decreased during the period of wound healing. In sum, this novel method provides a transferring system for cell therapies and maintains its temperature-sensitive property of easy-peeling by lower-temperature treatment. In addition, the in vitro and in vivo GFP imaging systems provide a new imaging modality for understanding the differentiation process and the effective expression of stem cells in wound healing.