442 Plastic and Reconstructive Surgery • August 2015 LOP24: Comparison of Treatments with Local Mesenchymal Stem Cells and Mesenchymal Stem Cells with Increased Vascular Endothelial Growth Factor Expression on Irradiation Injury of Expanded Skin *S. Öksüz 1 , S. Alagoz 2 , H. Karagoz 1 , Z. Kucukodaci 3 , E. Karaoz 4 , G. Duruksu 4 , G. Aksu 5 , M. Urhan 6 1 Gulhane Military Medical Academy Haydarpasa Training Hospital, Plastic and Reconstructive Surgery, Istanbul, Turkey 2 Kocaeli University Medical Faculty, Plastic and Reconstructive Surgery, Kocaeli, Turkey 3 Gulhane Military Medical Academy Haydarpasa Training Hospital, Pathology, Istanbul, Turkey 4 Kocaeli University, Institute of Health Sciences Center for Stem Cell and Gene Therapies, Kocaeli, Turkey 5 Kocaeli University, Radiation Oncology, Kocaeli, Turkey 6 Gulhane Military Medical Academy Haydarpasa Training Hospital, Nuclear Medicine, Istanbul, Turkey Background: Radiation injury results in chronically ischemic tissue or radionecrosis. Mesenchymal stem cells (MSCs) have therapeutic effect on ischemic lesions. In here, effects of bone- marrow derived MSC and vascular endothelial growth factor (VEGF) gene-transfected MSC (VEGF-MSC) treatment on expanded skin with irradiation injury is investigated. Material and Methods: Tissue expander (50cc) was placed and expanded up to 60cc in 24 Sprague Dawley rats. Single fraction (30Gy) radiotherapy was applied to the 2x2cm area of the expanded skin. Dulbecco’s Modified Eagle Medium, MSCs, and VEGF-MSCs were injected subcutaneously at the irradiation expansion sites. Skin samples were evaluated by histomorphometry and immunohistochemistry. Perfusion rate was assessed by scintigraphy. Results: Epidermal thickness of irradiated expanded skin increased after MSC and VEGF-MSC treatment whereas dermal and capsule thicknesses did not change. MSC and VEGF-MSC treatments were effective in preserving CD31 and VEGF expressions at a similar level as expanded skin after irradiation injury. VEGF-MSC treatment significantly elevated CD31 levels in the irradiated tissue. Skin perfusion results were consistent with the CD31 and VEGF expressions. MSC and VEGF-MSC treatments were effective in increasing PCNA expression in irradiation zone. VEGF-MSC treatment was efficient in reducing both expansion and irradiation related apoptosis. Conclusion: Vascular impairment and dermal insufficiency due to tissue expansion and irradiation injury can easily result in a wound hard to repair. MSCs and VEGF-MSCs promote neovascularization, reverse the effect of irradiation, and provide more durable soft tissue for expansion/implant reconstruction. LOP25: Phenotypic Analysis of Stromal Vascular Fraction After Mechanical Shear: Stress-induced Progenitor Transdifferentiation? *D. A. Banyard 1 , A. D. Widgerow 1 , G. A. Wirth 1 , K. Z. Paydar 1 , G. R. D. Evans 1 1 University of California, Irvine, Plastic Surgery, Orange, United States Introduction: Optimization of fat grafting continues to be hotly pursued in the field of regenerative medicine. One form, “nanofat grafting,” implements mechanical emulsification of standard lipoaspirate (LA) prior to reinjection (1). Beyond the observation that nanofat is devoid of adipocytes, its constituents are not well characterized. Material and Methods: LA (100 ml) was obtained from 6 patients undergoing elective procedures. 50 mls was subjected to nanofat processing then the two samples from each patient were subjected to collagenase digestion, red blood cell lysis and the resulting stromal vascular fraction (SVF) pellets stained with a multicolor fluorescence antibody panel (CD13-APC-Vio770, CD31-FITC, CD34-PerCP-Vio700, CD45-VioBlue, CD73-PE and CD146-APC) for flow cytometry analysis. Results: Compared to standard LA, the nanofat-processed SVF yielded greater CD34+ progenitor cells (5.09% vs 14.3%, p=0.003) as well as mesenchymal markers CD13 (2.58% vs 8.81%, p=0.002), CD73 (4.14% vs 10.0%, p=0.043) and CD146 (5.33% vs 10.5%, p=0.04). Moreover, MSC subpopulation analysis revealed a tendency towards adipose-derived stem (15.5% ± 10.2 vs 24.4% ± 8.2) and endothelial progenitor cell phenotypes (1.30% vs 6.42%, p=0.003) in the fat that was mechanically processed. Conclusion: Mechanical processing of standard lipoaspirate appears to induce progenitor and mesenchymal stem transdifferentiation. Our data provides a possible explanation for the regenerative benefits realized through fat grafting with nanofat. LOP26: Investigating the matrix chemistry of human adipose- derived stem cells: the first step toward creating a scaffold for optimal adipose tissue engineering with a biomimetic approach *M. Frimpong 1 , C. de Bari 1 , A. Curnier 1 1 Aberdeen University, Institute of Medical Sciences, Aberdeen, United Kingdom Introduction: The extracellular matrix (ECM) is a complex three- dimensional network of macromolecules including cell adhesion molecules such as fibronectin and collagen. These molecules have been shown to play a role in the regulation of human adipose- derived stem cell (hASC) growth and differentiation. As such, investigating the matrix chemistry of hASC culture has implications for improving the authenticity and functionality of biomimetic scaffolds for adipose tissue engineering in the future. Also, exploring the expression profiles of ECM molecule receptors on hASC’s can identify the most suitable subpopulations for use in tissue engineering. Materials and Methods: Human ASC’s were isolated from abdominal lipoaspirates of 5 patients with a mean age of 40 years. Human ASC’s at passages 2-3 were analysed by flow cytometry using an extensive (10+ fluorochromes) multicolour panel. Results: The highest expression levels and median fluorescence intensities were obtained for H-CAM, integrin-alpha 2 and integrin-alpha 5. Post-sort assays are ongoing to confirm differentiation capabilities. Conclusion: Matrix metalloproteinases, laminin and fibronectin are recommended as the ligands of choice for the highest level of incorporation into biomimetic scaffolds for future adipose tissue engineering. LOP27: Repetitive systemic delivery of mesenchymal stem cells after peripheral nerve injury - Chance for a better treatment? *C.- T. Peck 1 , S. Michael 1 , D. Schröder 1 , V. Bucan 1 , K. Reimers 1 , P. M. Vogt 1 , C. Radtke 1 1 Hannover Medical School, Plastic, Hand and Reconstructive Surgery, Hannover, Germany Introduction: Peripheral nerve injuries often lead to the loss of sensory and motor function of the respective limb. Peripheral nerve regeneration, however, is limited, and functional recovery, even after immediate surgical intervention, is often disappointing. Material and Methods: Due to their differentiation capability and secretion of neurotrophic factors, transplantation of mesenchymal stem cells (MSCs) from bone marrow or fat tissue is a very promising therapy strategy for nerve repair. When we compared the local injection of adipose-derived stem cells (ASCs) with their single and repetitive systemic administration by intravenous injection (iv) in a rat model of peripheral crushed nerve, we found the cell application method is very important for the clinical outcome. Results: Preliminary results show similar axonal regeneration in both, the local and single iv injected groups. However, myelination was significantly increased in case of direct cell administration into the crushed nerve compared to systemically administered ASCs and sham controls. Also, systemic iv injection of ASCs resulted in significantly higher myelination compared to sham controls. Nonetheless, repetitive cell injection seems to stimulate nerve regeneration more regularly. Conclusion: Regarding clinical translation, intravenous cell transplantation could offer a promising technique to optimize peripheral nerve regeneration. 442 Plastic and Reconstructive Surgery • August 2015