AAHS ASPN ASRM - 2013 Annual Meeting - American Association ...

Hindlimb Osteomyocutaneous Flap can Create Mixed Chimerism and Donor-Specific Tolerance to Composite
Tissue Allotransplantation with the Nonmyeloablative Conditioning in Rats
Institution where the work was prepared: Department of Plastic and Reconstructive Surgery, Chang Gung Mem, Taipei, Taiwan
Wei-Chao Huang, MD; Jeng-Yee Lin; Chung-Rong Ho; Yu-Hsuan Hsieh; Nai-Jen Chang; Fu-Chan Wei; Chang Gung Memorial Hospital
Introduction:
Composite tissue allotransplantation (CTA) such as knee and hand transplants may be regarded as vascularized bone marrow transplantation (VBMT). It has
been proven that lymphohematopoietic reconstitution with VBMT was faster than bone marrow (BM) cell infusion. BM cells from the donor vascularized bone
graft (VBG) may induce chimerism. The majority of these chimeras undergo tolerance while a minority develops graft versus host disease (GVHD) in rats. We
report here the use of hindlimb osteomyocutaneous flap transplantation can induce donor-specific tolerance to CTA with the nonmyeloablative conditioning.
Methods:
Male (10- and 12- week old) Brown Norway rats (RTA1C) were donors and male (10 – to 12-week old) Lewis rats (RTA1l) were recipients. Experimental groups
were: Group I: syngeneic control without total body irradiation (TBI). Group II: allogeneic control without TBI. Group III: TBI with 600 cGy. Group IV: TBI with
400 cGy. Group V: TBI with 200 cGy. Group VI: without TBI. Recipients in group III, IV, V, and VI were treated with 5 mg anti-lymphocyte serum (ALS) intraperitoneally
(IP) and TBI on day-1, tacrolimus (1mg/kg) IP from days 0 to 10, and 5mg ALS IP on day 10. All of recipients were transplanted with hindlimb osteomyocutaneous
flap on day 0. Before transplantation, the BM cells in the bone cavity were flushed and curettaged. Chimerism level and multilineage cells were
assessed by flow cytometry after transplantation. In vitro T-cell responses were evaluated by mixed lymphocyte reactivity (MLR) assays.
Results:
Group I accepted the syngeneic grafts permanently. Allografts in Group II were rejected within 14 days. GVHD was observed in 20% group III. The acceptance
rates of allograft were 80% in group III, 60% in group IV, 20% in group V and 0% in group VI. (Fig 1) Chimerism levels after flap allotransplantation were
proportional to dose of TBI. The chimerism was durable in group III, but lost in group IV, V and VI with time. The donor multilineage cells could be detected
in the recipient blood with allograft acceptance. MLR confirmed tolerance in tolerant recipients.
Conclusion:
Hematopoietic stem cells (HSC) in the VBG can create chimerism and tolerance to CTA in the nonmyeloablative conditioning. VBG in CTA directly offers the
BM niches of HSCs. Although maro-chimerism could be lost with time, tolerance to allograft still existed in this experiment. We conclude that timing of macrochimerism
is critical for tolerance induction in the early phase of CTA with the nonmyeloablative conditioning.
Nerve Regeneration Through Nerve Autografts and Cold Preserved Allografts Using Tacrolimus (FK506) in a
Facial Paralysis Model: a Topographical and Neurophysiological Study in Monkeys
Institution where the work was prepared: Clínica Universitaria, Universidad de Navarra, Pamplona, Spain
Cristina Aubá, MD, PhD; Bernardo Hontanilla, MD, PhD; Juan Arcocha; Oscar Gorría; Clínica Universitaria, Universidad de Navarra
The regeneration through nerve allografts temporarily treated for two months with FK506 does not reach the results obtained with autografts, at least in terms
of brain stem neuron number and electrophysiological recordings. There was an almost 70% lower neuronal population in the allograft group and it mainly
corresponded to missing small motoneurons. This lower participation of neurons is somehow compensated by collateral axon sprouting, which maintains the
electrical activity of the target muscle and allows it to produce normal facial movement. The plasticity of the peripheral nervous system is so prepared to compensate
for deficits in any level of its circuit that, in order to detect impairment of clinical results, the structural damage to the neural system must reach at
least 70%, as also occurs in other organs like the liver, kidney or pancreas. Thus, autografts or allografts may present similar clinical results although there is
an important neuronal impairment in the brain stem that is related to the small neurons that maintain electrical activity to the slow twitch muscle fibers. Finally,
the cessation of immunosuppression after two months in 4 cm long nerves leads to a partial graft rejection, but this does not diminish the functional movement
of the mimic muscles of the monkeyxs face. More experimental research is necessary to demonstrate if nerve regeneration occurs through long nerve
allografts.
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