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2008 Annual Meeting Abstracts


Increased progenitor cell mobilization with AMD3100 improves diabetic wound healing
Robert J. Allen, Jr., MD, Clarence D. Lin, MA, Phuong D. Nguyen, MD, Alexander Allori, MD, MPH, Alexander Sailon, BS, Jeffrey Schachar, BS, Evan Garfein, MD, Stephen M. Warren, MD.
New York University Medical Center, New York, NY, USA.

Background
Recent reports from our laboratory and others have found that progenitor cells released from the bone marrow play an integral role in the formation and repair of blood vessels throughout the body. Endothelial progenitor cells (EPCs) are released from the bone marrow (BM), migrate to areas of ischemia, and incorporate into the wound, where they contribute to as much as 35% of neovascularization. We have found this process to be impaired in diabetics. Specifically, diabetic mice have fewer circulating endothelial progenitor cells (EPCs) at baseline and following peripheral injury due to an impaired mobilization from the bone marrow. The purpose of this experiment was to study the effect of improved BM-EPC mobilization with the CXCR4 partial agonist, AMD3100, on diabetic wound healing.
Methods
Two 6-mm wounds were created on the dorsal skin of diabetic mice (type II model) using a sterile punch biopsy. The wounds were stented with a 12-mm silicone O-ring to prevent wound contracture and promote healing by secondary intention. AMD3100 or sterile saline (10mg/kg) was injected intraperitoneally (i.p.) into the treatment group (n=20) and control group (n=20), respectively, once daily from post-operative day 3 until time of wound closure. Photogrammetry was used to measure time to closure. Circulating EPC number (Lin-, Sca-1+, ckit+, Flk+) was quantified by flow cytometry at 1 hour and days 7, 14, and 21 post-wounding. Wound vascularity was assessed by CD31 staining.
Results
Diabetic mice treated intraperitoneally with AMD3100 showed a significantly improved closure rate compared to controls (p < 0.05). At post-wounding days 7, 14, and 21, mice treated with AMD3100 had wound closures of 32.7±5.0%, 72.9±6.4%, and 90±5.7%, respectively, compared to control wound closure of 11.9±3.0%, 36.5±7.0%, and 66.7±5.0%. Flow cytometry of peripheral blood demonstrated increased circulating EPCs (Lin-, Sca-1+ cells) in response to AMD3100 administration with a 3.7±1.0-fold increase at 1 hour, 11.9±1.7-fold increase at day 7, and 19.6±1.9-fold increase at day 14. Interestingly, there was a 23.6-fold decrease in circulating EPCs in treated animals at day 21. CD31 staining of the wounds found that animals treated with AMD3100 had an increased vascular density (vessels/megapixel) compared to controls at Day 21 (325.4±113.5 vs 155.3±48.2; p<0.03).
Conclusion
We conclude that AMD3100 improves diabetic wound healing in mice by improving BM-EPC mobilization and, subsequently, the neovascularization of ischemic tissues. Furthermore, the rate of closure is directly proportional to the percentage of peripherally circulating EPCs. Additional studies may find this treatment regimen useful for the prevention and/or curative therapy for non-healing diabetic ulcers.