Plastic Surgery Research Council
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Presenter: Kate J Buretta, BS
Co-Authors: Brat GA; Christensen JM; Ibrahim Z; Grahammer J; Furtmueller G; Suami H; Cooney DS; Andrew Lee WP; Brandacher G; Sacks JM
Johns Hopkins University School of Medicine

Background: Vascularized composite allotransplantation (VCA) has become a prominent reconstructive option for patients suffering major tissue loss. Wider application is limited by the need for chronic immunosuppression. Recent data suggest that the cutaneous lymphatic system plays an important role in mediating allograft rejection. However, little is known about lymphatic reconstitution in VCA. The purpose of this study was to describe cutaneous lymphatic reconstitution in rat orthotopic hind-limb transplants using near-infrared (NIR) lymphography.

Methods: Syngeneic (Lewis-Lewis) and allogeneic (Brown Norway-Lewis) rat orthotopic hind limb transplants were performed with no immunosuppression. Animals were imaged pre- and post-operatively using indocyanine green (ICG) NIR lymphography. Images were collected for up to four weeks using the SPY Elite imaging device. Co-localization was achieved by injecting an acrylic paint/hydrogen peroxide mixture into the same locations as the ICG. Paint-stained lymphatic vessels were dissected out to confirm drainage through continuous vessels.

Results: Prior to transplantation, all donor limbs exhibited a fine, organized superficial lymphatic drainage system. In both syngeneic and allogeneic transplants, ICG first crossed graft suture lines via a single network of superficial vessels on post-operative (POD) 5. Clinical signs of rejection also appeared on POD 5 in allogeneic animals, with most allogeneic animals exhibiting Grade 3 rejection by POD 6. By POD 14, a dense meshwork of vessels developed at the suture line of syngeneic transplants. Injection of the acrylic paint/hydrogen peroxide mixture on POD 5 and POD 14 confirmed the existence of continuous lymphatic vessels crossing the suture line and draining into the inguinal node.

Conclusion: NIR lymphography can be used to identify reconstituted lymphatic vessels in orthotopic hind limb transplants. In both syngeneic and allogeneic transplants, cutaneous lymphatic reconstitution occurs during the acute inflammatory phase. Lymphatic reconstitution may play a role in the acute rejection of allogeneic VCAs."

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