Sunday, October 3, 2010
18253

Chemical Delay of Flaps through Endogenous Stem Cell Therapy

Alexandre Marchac, MD1, Parag Butala, MD1, Denis Knobel, MD1, Robert J. Allen, MD1, Caroline Szpalski, MD1, Meredith, T. Wetterau, MD1, James, L. Crawford, BS1, Edward, H. Davidson, MBBS1, Pierre B. Saadeh, MD2, and Stephen Warren, MD3. (1) Plastic Surgery, NYU Langone Medical Center, 560 First Ave., TCH-169, New York, NY 10016, (2) Institute of Reconstructive Plastic Surgery Laboratories, NYU, 560 First Avenue, TCH-169, New York, NY 10016, (3) New York University Medical Center, Institute of Reconstructive Plastic Su, 560 First Avenue, TH-169, New York, NY 10016-6497

Background: Blood supply is a limiting factor in flap surgery. Endothelial progenitor cells (EPCs) migrate from the bone marrow into sites of ischemic injury to contribute to neovascularization. By disrupting the CXCR4/SDF-1 axis, AMD3100, a clinically approved stem cell mobilizer, increases circulating (c)EPCs.[1][2] In previous studies, we have shown that AMD3100 accelerates reossification in a distraction osteogenesis model and improves diabetic wound healing. Furthermore, others have shown that AMD3100 accelerates revascularization in ischemic hind limbs.[3, 4] We hypothesize that pretreating a flap with a topical chemoattractant (e.g. PDGF) will promote trafficking of AMD3100 mobilized bone marrow stem cells to improve flap survival.

Methods: Using a previously described reproducible murine ischemic dorsal skin flap model, wild-type (WT) FVB mice were randomized into 4 groups (n=10/group): untreated WT, AMD3100-treated WT (A+), PDGF-treated WT (P+), and AMD3100/PDGF-treated WT (A+P+). Prior to surgery, P+ and A+P+ mice were treated for 3 days with PDGF-BB (2μg). A+ and A+P+ received AMD3100 (5mg/kg, SC) 1 hour prior to surgery, and daily postoperatively. Flap survival was assessed photometrically. Histology, immunohistochemistry, ELISA, quantitative RT-PCR and in vitro migration assays toward SDF-1 and PDGF where performed at sequential timepoints. Flap vascularity was assessed by tissue oximetry measurements (SatO2%), color laser Doppler analysis (flux ratio) and CD31 immunofluorescence (vessels/hpf). cEPC number was determined by FACS.

Results: AMD3100 treatment increased cEPC levels (3.7±1.0-fold at 1 hour, p<0.05; 5.5±1.1-fold at day 7, p<0.02; and 13.2±0.5- fold at day 14, p<0.02). A+P+ had the greatest improvements in flap survival and flap vascularity (431.8±19.3 vessels/hpf vs. 155.3±16.1 vessels/hpf, p<0.001) compared to untreated WT mice. In the presence of AMD3100, EPC migration to SDF-1 was decreased 25.1±2.8% (p<0.05), while EPC migration towards PDGF-BB was unaffected (8.4±3.4% fewer, p>0.05).

Conclusion: These are the first preclinical chemical delay data to support a novel endogenous stem cell therapy to significantly improve flap survival.

Reference: 1.De Clercq, E., The AMD3100 story: the path to the discovery of a stem cell mobilizer (Mozobil). Biochem Pharmacol, 2009. 77(11): p. 1655-64. 2.Devine, S.M., et al., Rapid mobilization of functional donor hematopoietic cells without G-CSF using AMD3100, an antagonist of the CXCR4/SDF-1 interaction. Blood, 2008. 112(4): p. 990-8. 3.Tan, Y., et al., A novel CXCR4 antagonist derived from human SDF-1beta enhances angiogenesis in ischaemic mice. Cardiovascular Research, 2009. 82(3): p. 513-21. 4.Jiao, C., S. Fricker, and G.C. Schatteman, The chemokine (C-X-C motif) receptor 4 inhibitor AMD3100 accelerates blood flow restoration in diabetic mice. Diabetologia, 2006. 49(11): p. 2786-9.

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