Papers by Georg Furtmuller
PLoS ONE, 2013
Reconstructive transplantation such as extremity and face transplantation is a viable treatment o... more Reconstructive transplantation such as extremity and face transplantation is a viable treatment option for select patients with devastating tissue loss. Sensorimotor recovery is a critical determinant of overall success of such transplants. Although motor function recovery has been extensively studied, mechanisms of sensory re-innervation are not well established. Recent clinical reports of face transplants confirm progressive sensory improvement even in cases where optimal repair of sensory nerves was not achieved. Two forms of sensory nerve regeneration are known. In regenerative sprouting, axonal outgrowth occurs from the transected nerve stump while in collateral sprouting, reinnervation of denervated tissue occurs through growth of uninjured axons into the denervated tissue. The latter mechanism may be more important in settings where transected sensory nerves cannot be re-apposed. In this study, denervated osteomyocutaneous alloflaps (hind-limb transplants) from Major Histocompatibility Complex (MHC)-defined MGH miniature swine were performed to specifically evaluate collateral axonal sprouting for cutaneous sensory re-innervation. The skin component of the flap was externalized and serial skin sections extending from native skin to the grafted flap were biopsied. In order to visualize regenerating axonal structures in the dermis and epidermis, 50um frozen sections were immunostained against axonal and Schwann cell markers. In all alloflaps, collateral axonal sprouts from adjacent recipient skin extended into the denervated skin component along the dermal-epidermal junction from the periphery towards the center. On day 100 post-transplant, regenerating sprouts reached 0.5 cm into the flap centripetally. Eight months following transplant, epidermal fibers were visualized 1.5 cm from the margin (rate of regeneration 0.06 mm per day). All animals had pinprick sensation in the periphery of the transplanted skin within 3 months post-transplant. Restoration of sensory input through collateral axonal sprouting can revive interaction with the environment; restore defense mechanisms and aid in cortical re-integration of vascularized composite allografts. Citation: Ibrahim Z, Ebenezer G, Christensen JM, Sarhane KA, Hauer P, et al. (2013) Cutaneous Collateral Axonal Sprouting Re-Innervates the Skin Component and Restores Sensation of Denervated Swine Osteomyocutaneous Alloflaps. PLoS ONE 8(10): e77646. (MP) ☯ These authors contributed equally to this work.
Vascularized Composite Allotransplantation, 2014
Transplant International, 2013
Wider application of vascularized composite allotransplantation (VCA) is limited by the need for ... more Wider application of vascularized composite allotransplantation (VCA) is limited by the need for chronic immunosuppression. Recent data suggest that the lymphatic system plays an important role in mediating rejection. This study used near-infrared (NIR) lymphography to describe lymphatic reconstitution in a rat VCA model. Syngeneic (Lewis-Lewis) and allogeneic (Brown Norway-Lewis) rat orthotopic hind limb transplants were performed without immunosuppression. Animals were imaged pre-and postoperatively using indocyanine green (ICG) lymphography. Images were collected using an NIR imaging system. Co-localization was achieved through use of an acrylic paint/hydrogen peroxide mixture. In all transplants, ICG first crossed graft suture lines on postoperative day (POD) 5. Clinical signs of rejection also appeared on POD 5 in allogeneic transplants, with most exhibiting Grade 3 rejection by POD 6. Injection of an acrylic paint/hydrogen peroxide mixture on POD 5 confirmed the existence of continuous lymphatic vessels crossing the suture line and draining into the inguinal lymph node. NIR lymphography is a minimally invasive imaging modality that can be used to study lymphatic vessels in a rat VCA model. In allogeneic transplants, lymphatic reconstitution correlated with clinical rejection. Lymphatic reconstitution may represent an early target for immunomodulation.
Journal of the American College of Surgeons, 2013
PLoS ONE, 2013
Reconstructive transplantation such as extremity and face transplantation is a viable treatment o... more Reconstructive transplantation such as extremity and face transplantation is a viable treatment option for select patients with devastating tissue loss. Sensorimotor recovery is a critical determinant of overall success of such transplants. Although motor function recovery has been extensively studied, mechanisms of sensory re-innervation are not well established. Recent clinical reports of face transplants confirm progressive sensory improvement even in cases where optimal repair of sensory nerves was not achieved. Two forms of sensory nerve regeneration are known. In regenerative sprouting, axonal outgrowth occurs from the transected nerve stump while in collateral sprouting, reinnervation of denervated tissue occurs through growth of uninjured axons into the denervated tissue. The latter mechanism may be more important in settings where transected sensory nerves cannot be re-apposed. In this study, denervated osteomyocutaneous alloflaps (hind-limb transplants) from Major Histocompatibility Complex (MHC)-defined MGH miniature swine were performed to specifically evaluate collateral axonal sprouting for cutaneous sensory re-innervation. The skin component of the flap was externalized and serial skin sections extending from native skin to the grafted flap were biopsied. In order to visualize regenerating axonal structures in the dermis and epidermis, 50um frozen sections were immunostained against axonal and Schwann cell markers. In all alloflaps, collateral axonal sprouts from adjacent recipient skin extended into the denervated skin component along the dermal-epidermal junction from the periphery towards the center. On day 100 post-transplant, regenerating sprouts reached 0.5 cm into the flap centripetally. Eight months following transplant, epidermal fibers were visualized 1.5 cm from the margin (rate of regeneration 0.06 mm per day). All animals had pinprick sensation in the periphery of the transplanted skin within 3 months post-transplant. Restoration of sensory input through collateral axonal sprouting can revive interaction with the environment; restore defense mechanisms and aid in cortical re-integration of vascularized composite allografts. Citation: Ibrahim Z, Ebenezer G, Christensen JM, Sarhane KA, Hauer P, et al. (2013) Cutaneous Collateral Axonal Sprouting Re-Innervates the Skin Component and Restores Sensation of Denervated Swine Osteomyocutaneous Alloflaps. PLoS ONE 8(10): e77646. (MP) ☯ These authors contributed equally to this work.
Vascularized Composite Allotransplantation, 2014
Transplant International, 2013
Wider application of vascularized composite allotransplantation (VCA) is limited by the need for ... more Wider application of vascularized composite allotransplantation (VCA) is limited by the need for chronic immunosuppression. Recent data suggest that the lymphatic system plays an important role in mediating rejection. This study used near-infrared (NIR) lymphography to describe lymphatic reconstitution in a rat VCA model. Syngeneic (Lewis-Lewis) and allogeneic (Brown Norway-Lewis) rat orthotopic hind limb transplants were performed without immunosuppression. Animals were imaged pre-and postoperatively using indocyanine green (ICG) lymphography. Images were collected using an NIR imaging system. Co-localization was achieved through use of an acrylic paint/hydrogen peroxide mixture. In all transplants, ICG first crossed graft suture lines on postoperative day (POD) 5. Clinical signs of rejection also appeared on POD 5 in allogeneic transplants, with most exhibiting Grade 3 rejection by POD 6. Injection of an acrylic paint/hydrogen peroxide mixture on POD 5 confirmed the existence of continuous lymphatic vessels crossing the suture line and draining into the inguinal lymph node. NIR lymphography is a minimally invasive imaging modality that can be used to study lymphatic vessels in a rat VCA model. In allogeneic transplants, lymphatic reconstitution correlated with clinical rejection. Lymphatic reconstitution may represent an early target for immunomodulation.
Http Dx Doi Org 10 4161 23723505 2014 970058, Dec 19, 2014
Journal of Visualized Experiments, 2016
Exploration of novel strategies in organ transplantation to prolong allograft survival and minimi... more Exploration of novel strategies in organ transplantation to prolong allograft survival and minimizing the need for long-term maintenance immunosuppression must be pursued. Employing vascularized bone marrow transplantation and co-transplantation of the thymus have shown promise in this regard in various animal models.(1-11) Vascularized bone marrow transplantation allows for the uninterrupted transfer of donor bone marrow cells within the preserved donor microenvironment, and the incorporation of thymus tissue with vascularized bone marrow transplantation has shown to increase T-cell chimerism ultimately playing a supportive role in the induction of immune regulation. The combination of solid organ and vascularized composite allotransplantation can uniquely combine these strategies in the form of a novel transplant model. Murine models serve as an excellent paradigm to explore the mechanisms of acute and chronic rejection, chimerism, and tolerance induction, thus providing the foundation to propagate superior allograft survival strategies for larger animal models and future clinical application. Herein, we developed a novel heterotopic en bloc chest wall, thymus, and heart transplant model in mice using a cervical non-suture cuff technique. The experience in syngeneic and allogeneic transplant settings is described for future broader immunological investigations via an instructional manuscript and video supplement.
Nature nanotechnology, Jan 2, 2015
Many surgeries are complicated by the need to anastomose, or reconnect, micrometre-scale vessels.... more Many surgeries are complicated by the need to anastomose, or reconnect, micrometre-scale vessels. Although suturing remains the gold standard for anastomosing vessels, it is difficult to place sutures correctly through collapsed lumen, making the procedure prone to failure. Here, we report a multiphase transitioning peptide hydrogel that can be injected into the lumen of vessels to facilitate suturing. The peptide, which contains a photocaged glutamic acid, forms a solid-like gel in a syringe and can be shear-thin delivered to the lumen of collapsed vessels (where it distends the vessel) and the space between two vessels (where it is used to approximate the vessel ends). Suturing is performed directly through the gel. Light is used to initiate the final gel-sol phase transition that disrupts the hydrogel network, allowing the gel to be removed and blood flow to resume. This gel adds a new tool to the armamentarium for micro- and supermicrosurgical procedures.
Cell Reports, 2015
Upon antigen recognition and co-stimulation, T lymphocytes upregulate the metabolic machinery nec... more Upon antigen recognition and co-stimulation, T lymphocytes upregulate the metabolic machinery necessary to proliferate and sustain effector function. This metabolic reprogramming in T cells regulates T cell activation and differentiation but is not just a consequence of antigen recognition. Although such metabolic reprogramming promotes the differentiation and function of T effector cells, the differentiation of regulatory T cells employs different metabolic reprogramming. Therefore, we hypothesized that inhibition of glycolysis and glutamine metabolism might prevent graft rejection by inhibiting effector generation and function and promoting regulatory T cell generation. We devised an anti-rejection regimen involving the glycolytic inhibitor 2-deoxyglucose (2-DG), the anti-type II diabetes drug metformin, and the inhibitor of glutamine metabolism 6-diazo-5-oxo-L-norleucine (DON). Using this triple-drug regimen, we were able to prevent or delay graft rejection in fully mismatched skin and heart allograft transplantation models.
Expert review of clinical immunology, Jan 18, 2015
Broader clinical application of reconstructive hand and face transplantation is hindered by the n... more Broader clinical application of reconstructive hand and face transplantation is hindered by the need for lifelong immunosuppression for allograft maintenance. In this review, we summarize various cell-based approaches to tolerance induction currently under investigation in both clinical and pre-clinical models to alleviate the need for chronic immunosuppression. These include strategies to induce mixed hematopoietic chimerism, therapy with T and B regulatory cells, regulatory macrophages, tolerogenic dendritic cells, and mesenchymal stem cells. The vascularized, intragraft bone components inherent to reconstructive transplants serve as a continuous source of donor-derived hematopoietic cells, and make hand and face transplants uniquely well suited for cell-based approaches to tolerance that may ultimately tilt the risk-benefit balance for these life-changing, but not life-saving, procedures.
PloS one, 2014
To demonstrate the feasibility of a miniature handheld optical coherence tomography (OCT) imager ... more To demonstrate the feasibility of a miniature handheld optical coherence tomography (OCT) imager for real time intraoperative vascular patency evaluation in the setting of super-microsurgical vessel anastomosis. A novel handheld imager Fourier domain Doppler optical coherence tomography based on a 1.3-µm central wavelength swept source for extravascular imaging was developed. The imager was minimized through the adoption of a 2.4-mm diameter microelectromechanical systems (MEMS) scanning mirror, additionally a 12.7-mm diameter lens system was designed and combined with the MEMS mirror to achieve a small form factor that optimize functionality as a handheld extravascular OCT imager. To evaluate in-vivo applicability, super-microsurgical vessel anastomosis was performed in a mouse femoral vessel cut and repair model employing conventional interrupted suture technique as well as a novel non-suture cuff technique. Vascular anastomosis patency after clinically successful repair was evalu...
Plastic and Reconstructive Surgery, 2013
ABSTRACT PURPOSE: Vascularized Composite Allografts (VCA), such as hand and upper extremity trans... more ABSTRACT PURPOSE: Vascularized Composite Allografts (VCA), such as hand and upper extremity transplants, contain vascularized bone marrow (BM) and a BM niche representing a constant source of donor-derived stem cells and hence can favor chimerism and tolerance induction (1). This study investigates the immunological effects of vascularized BM within VCA under co-stimulation blockade-based regimen and its impact on allograft survival and tolerance induction. METHODS AND MATERIALS: Fully MHC- and gender mismatched MGH miniature swine (n=20) underwent heterotopic hind-limb transplantation containing intact vascularized BM component (Figure 1). Recipient animals received a short course (30 days) of tacrolimus monotherapy with or without donor BM infusion (60x106 cells/kg), and CTLA4Ig. Short course tacrolimus only and untreated animals served as controls. Chimerism was assessed by SRY-1 qRT-PCR analysis. Sequential skin and muscle biopsies were performed for histology. Alloreactivity against donor antigens was assessed in vitro using CFSE-based mixed lymphocyte reaction assays. Challenge with secondary skin grafts was utilized to demonstrate robust immune tolerance in vivo. RESULTS: The co-stimulation blockade based immunomodulatory protocol resulted in indefinite graft survival (>150 days) in 3 out of 5 animals whereas control and tacrolimus only groups rejected allografts at days 7+/-1 and 29+/-2 respectively (Figure 2). Combined costimulation blockade with augmented donor BM infusion resulted in indefinite graft survival in 2 out of 3 animals (>150 days). Long-term survivors demonstrated only transient peripheral but stable micro-chimerism in various graft and recipient tissues including skin, lymph node, bone marrow, and spleen. CFSE-MLR data showed unresponsiveness to donor but not to third party allogeneic controls. Secondary skin grafting demonstrated advanced rejection of third party grafts on day 7 while donor-matched grafts were accepted indicating donor-specific immune tolerance. There was no evidence of donor specific antibody formation in long-term survivors. Donor unresponsiveness in MLR was lost 5 weeks post-graftectomy, which demonstrated that persistent antigenic stimulation was required for operational tolerance. CONCLUSION: Combined costimulation blockade and donor BM cell infusion can induce robust immune tolerance in a fully MHC mismatched hind limb transplant model. Such targeted immunomodulatory protocols might eliminate the need for long-term multi-drug immunosuppression after reconstructive transplantation. Figure 1: Schematic diagram: Osteomyocutaneous flap is transplanted to a subcutaneous pocket with externalized skin component. Figure 2: Kaplan-Meier survival curve demonstrating rejection free survival of skin component of VCA
Plastic and Reconstructive Surgery, 2014
Journal of the American College of Surgeons, 2013
Journal of Reconstructive Microsurgery, 2003
There are many potential advantages to using a mouse as a model for composite tissue transplantat... more There are many potential advantages to using a mouse as a model for composite tissue transplantation, particularly to examine the mechanisms behind various tolerance induction protocols. The purpose of this study was to evaluate the reliability of a new hindlimb transplant model in the mouse. Fifteen Swiss-Webster mice, 14 to 16 weeks old (35 to 50 g), had syngeneic hindlimb transplants performed. The donor limb was attached to the recipient limb stump first by bony fixation using an intramedullary rod (22-gauge needle, 2.5 mm in length). The venous anastomosis was performed across a stent fashioned from a 27-gauge nylon I.V. catheter tip cover and secured with two simple ties using 10-0 nylon. The arterial anastomosis was performed with interrupted 11-0 nylon stitches. Eleven of the fifteen transplanted limbs survived for the duration of the study (30 days). All four failures occurred within 4 hr postoperatively, (venous thrombosis, n = 2; arterial thrombosis, n = 2). Clamp time decreased throughout the study, averaging 56 min for the final four transplants and 88 min total operative time. Orthotopic hindlimb transplantation can be reliably achieved in a mouse. The mouse model should be useful to the future study of composite tissue allotransplantation.
Annals of Plastic Surgery, 2014
The pudendal nerve is located topographically in areas in which plastic surgeon reconstruct the p... more The pudendal nerve is located topographically in areas in which plastic surgeon reconstruct the penis, the vagina, the perineum, and the rectum. This nerve is at risk for either compression or direct injury with neuroma formation from obstetrical, urogynecologic, and rectal surgery as well as pelvic fracture and blunt trauma. The purpose of this study was to create a 3-dimensional representation based on magnetic resonance imaging of the pelvis supplemented with new anatomic dissections in men and women to delineate the location of the pudendal nerve and its branches, providing educational information both for surgical intervention and patient education. The results of this study demonstrated that most often there are at least 2, not 1, "pudendal nerves trunks" as they leave the pelvis to transverse the sacrotuberous ligament, and that there are most often 2, not 1, exit(s) from Alcock canal, one for the dorsal branch and one for the perineal branch of the pudendal nerve.
Vascularized Composite Allotransplantation, 2014
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Papers by Georg Furtmuller