Tolerance and Future Directions for Composite Tissue Allograft Transplants: Part II

Bioengineering a Human Face Graft: The Matrix of Identity

OBJECTIVE

During the last decade, face allotransplantation has been shown to be a revolutionary reconstructive procedure for severe disfigurements. However, offer to patients remains limited due to lifelong immunosuppression. To move forward in the field, a new pathway in tissue engineering is proposed.

BACKGROUND

Our previously reported technique of matrix production of a porcine auricular subunit graft has been translated to a human face model.

METHODS

5 partial and 1 total face grafts were procured from human fresh cadavers. After arterial cannulation, the specimens were perfused using a combined detergent/polar solvent decellularization protocol. Preservation of vascular patency was assessed by imaging, cell and antigen removal by DNA quantification and histology. The main extracellular matrix proteins and associated cytokines were evaluated. Lip scaffolds were cultivated with dermal, muscle progenitor and endothelial cells, either on discs or in a bioreactor.

RESULTS

Decellularization was successful in all facial grafts within 12 days revealing acellular scaffolds with full preservation of innate morphology. Imaging demonstrated a preservation of the entire vascular tree patency. Removal of cells and antigens was confirmed by reduction of DNA and antigen markers negativation. Microscopic evaluation revealed preservation of tissue structures as well as of major proteins. Seeded cells were viable and well distributed within all scaffolds.

CONCLUSIONS

Complex acellular facial scaffolds were obtained, preserving simultaneously a cell-friendly extracellular matrix and a perfusable vascular tree. This step will enable further engineering of postmortem facial grafts, thereby offering new perspectives in composite tissue allotransplantation.

Experimental Design for Composite Face Transplantation

Face allotransplantation represents a novel frontier in complex human facial defect reconstruction. To develop more refined surgical techniques and yield fine results, it is first imperative to make a suitable animal model. The development of a composite facial allograft model in swine is more appealing: the facial anatomy, including facial nerve and vascular anatomy, is similar to that of humans. Two operative teams performed simultaneously, one assigned to harvest the donor and the other to prepare the recipient in efforts to shorten operative time. The flap was harvested with the common carotid artery and external jugular vein, and it was transferred to the recipient. After insetting the maxilla, mandible, muscles, and skins, the anastomosis of the external jugular vein, external carotid artery, and facial nerve were performed. The total mean time of transplantation was 7 hours, and most allografts survived without vascular problems. The authors documented that this model is well qualified to be used as a standard transplantation training model and future research work, in every aspect.

Experimental canine facial transplantation

OBJECTIVE

Facial allotransplantation represents a novel frontier in the reconstruction of complex human facial defects. To develop more refined surgical techniques and yield fine results, it is required to make a suitable animal model. The development of a model of composite facial and scalp allograft in canines is more appealing: In large animals, canine facial anatomy is the most similar to humans; its facial nerve anatomy also resembles humans'; and canines possess the most similar facial vascular anatomy to humans. These factors led to the development of a canine composite facial allograft model.

METHODS

Two operative teams performed simultaneously on both donor and recipient to harvest the hemifacial/scalp flap and to prepare the recipient to shorten operative time. The flap was harvested with the common carotid artery and external jugular vein and transferred to the recipient. After insetting of the cartilage, skin, and muscles, the anastomosis of the external jugular vein and anastomosis between the external carotid artery and lingual artery were performed.

RESULTS

The total mean time of transplantation was 5 hours ± 30 minutes. All of the transplanted animals were wreated with FK-506 [tacrolimus, 2 mg/kg] for 7 days after surgery. Clinical rejection response was also identified by close monitoring. Most allografts survived with perfect viability without vascular problems in the early postoperative period.

CONCLUSIONS

We documented that this model is well qualified in every aspect for use as a standard transplantation training model and future research work.

Vascularized bone marrow transplantation model in rats as an alternative to conventional cellular bone marrow transplantation: preliminary results

The aim of the study was to follow the development of microchimerism after allogeneic vascularized bone marrow transplantation (VBMT) versus conventional bone marrow transplantation (BMT). In one group, a VBMT model consisted of donor Brown Norway rat hind limb heterotopic transplanted on recipient Lewis rats. An intravenous infusion of donor bone marrow cells in suspension equivalent to that grafted in the vascularized femur limb was administered intravenously to recipient rats in the second group. Cellular microchimerism was investigated in recipients of VBMT versus BMT. Donor-derived cells could be detected in VBMT recipients at 30 and 60 days but not in recipients of intravenous suspension of BMC. VBMT provides a theoretical alternative to conventional cellular bone marrow transplantation by addressing crucial clinical problems such as failure of engraftment or graft-versus-host disease.

Immunodepletive anti-alpha/beta-TCR antibody in transplantation of composite tissue allografts: Cleveland Clinic research experience

The immunologic characteristics of composite tissue allografts (CTA), which contain skin, lymphoid elements and bone with bone marrow, raise new challenges for transplant immunologists. Owing to the heterogeneity of transplanted tissues in limb or face transplant models, researchers are focusing on the new tolerance-inducing strategies facilitating CTA acceptance. A number of immunosuppressive protocols have been designed to develop tolerance in experimental models; however, only a few protocols have been introduced to clinical transplantation. In this review, based on own experiences, we discuss the major strategies for tolerance induction in limb and face allograft models in experimental studies. This review is focused on tolerance induction strategies by establishment of donor-specific chimerism using different immunomodulatory protocols, including nonselective T-cell depletion with polyclonal antibody antilymphocyte serum and selective inhibition of alphabeta-T-cell receptors on the alloreactive T cells.

Cost analysis of conventional facial reconstruction procedures followed by face transplantation

For the first time, this study analyzes the cost of multiple conventional reconstructions and face transplantation in a single patient. This patient is a 46-year-old female victim of a shotgun blast resulting in loss of multiple functional and aesthetic subunits. For over 5 years, she underwent multiple conventional reconstructions with suboptimal results. In December 2008, she became the recipient of the first U.S. face transplant. This has provided the unique opportunity to present the cost of 23 separate conventional reconstructive procedures and the first face transplant in the United States. The combined cost of conventional reconstructive procedures and the first U.S. face transplant was calculated to be $353 480 and $349 959, respectively. The combined cost posttransplant totaled $115 463. The direct cost pretransplant was $206 646, $232 893 peritransplant and $74 236 posttransplant. The two largest areas of cost utilization were surgical ($79 625; 38.5%) and nursing ($55 860; 27%), followed by anesthesia ($24 808; 12%) and pharmacy ($16 581; 8%). This study demonstrates that the cost of the first U.S. face transplant is similar to multiple conventional reconstructions. Although the cost of facial transplantation is considerable, the alleviation of psychological and physiological suffering, exceptional functional recovery and fulfillment of long-lasting hope for social reintegration may be priceless.