Donor Cell Repopulation of Whole-Limb Allografts in the Rat: Detection with Green Fluorescent Protein

Management of the 'tight orbit' and associated visual loss

PURPOSE OF REVIEW

To review the most recent literature on the management of the orbit under high pressure (the tight orbit) with threatened visual loss.

RECENT FINDINGS

Definitive management of traumatic optic neuropathy remains unclear, lacking randomized head-to-head treatment option trials. Instead, numerous case series and anecdotal reports show benefit in each of the four treatment modalities currently in use, but a multitude of variables confound cross-study comparison. In contrast, the management of orbital hemorrhage and orbital emphysema is well known. A number of immunomodulatory protocols have recently arisen for the medical suppression of Graves' ophthalmopathy, but when surgical decompression is required, most authors currently favor a combined transconjunctival and endoscopic endonasal approach.

SUMMARY

This article reviews the anatomy, pathophysiology, diagnosis, and intervention of the 'tight orbit' with associated visual loss. Guidelines for the intervention are given.

Immunomodulatory effects of pre-irradiated extremity allograft in the rodent model

Allogeneic human hand transplantation requires combination immunotherapy to maintain viability. Immunosuppression will be lifelong, with doses as high or higher than those required for solid organ allotransplantation. The risks associated with lifelong immunosuppression are unacceptable, particularly for younger transplant patients. It therefore becomes imperative to explore ways to reduce or eliminate the requirement for immunosuppression. Reconstructive surgery should consider, to a large extent, graft pre-treatment as a strategy for the transplantation of vascularised limb tissue allografts with reduced requirement for immunosuppression. In the clinical setting of composite tissue allograft (CTA), the graft is always procured from a cadaveric donor. Therefore, only a short time is available between harvesting the graft from the donor and transplanting into the recipient. This period provides the only opportunity to manipulate the CTA. Quite a few studies, however, have so far investigated donor pre-treatment and pre-transplant modification of the extremity allograft. Work from our group and others has demonstrated that removal of allogeneic bone marrow in the limb graft by irradiation and its rapid reconstitution with recipient marrow cells can significantly prolong the survival of limb allografts in the absence of immunosuppression. In the current work, we review these studies and discuss the immunomodulatory effects on the extremity allograft.

Prolonged survival of experimental extremity allografts: a new protocol with total body irradiation, granulocyte-colony stimulation factor, and FK506

The induction of a high-level of chimerism (macrochimerism) may be the most reliable strategy for achieving donor-specific tolerance. The purpose of this study was to evaluate the efficacy of a new protocol using total-body irradiation (TBI) and granulocyte-colony stimulation factor (G-CSF) to induce high-level chimerism following rat whole-limb allotransplantation. In this study, we investigated whether the timing of TBI influenced the period of graft survival. In total, 50 whole-limb allotransplants from LacZ transgenic rats to LEW rats were performed. TBI was performed at days 0 and 14, and G-CSF was given for 4 days after TBI. FK506 was given for 28 days after transplant. Nontreated limb allografts were rejected after 4.2 days. The survival time was prolonged to 64 days in the FK506 monotherapy group. In the group receiving TBI at day 14, limb allograft survival was significantly prolonged to 81 days. In the group receiving TBI at day 0, 26% of recipients died but in the surviving recipients the grafts survived for longer than 1 year without lethal graft-versus-host disease (GVHD). Polymerase chain reaction (PCR) analysis revealed a high level of intrabone marrow chimerism in the recipient, thus demonstrating successful induction of macrochimerism. A new protocol of pretransplant TBI followed by treatment with G-CSF and FK506 was found to induce a high level of chimerism and to significantly prolong the survival of limb allografts in recipients without lethal GVHD.

Intragraft chimerism following composite tissue allograft

Until now, more than 35 hand transplants have been performed in humans and have generated much public interest. Cell traffic from the recipient into the graft, so-called intragraft chimerism, appears to play a major role in graft acceptance and graft rejection. Little is known about cell migration following extremity allografts. In this review, recent experimental studies are presented for intragraft chimerism of the extremity allograft. Technical tools for detecting recipient cells in the graft were: (1) immunohistochemistry, (2) karyotyping, (3) fluorescent in situ hybridization, (4) polymerase chain reaction, and (5) transgenic animals. This study demonstrates that recipient-derived cells gradually repopulate into grafted skin, bone tissues, bone marrow, and endothelial cells, but muscle, periosteum, and cartilage tissues retain donor cell origin.