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Composite transplants involve multiple tissues, usually including skin and soft tissues and sometimes musculoskeletal structures. Many of these procedures are now possible because of advances in immunosuppressive therapy. However, the procedures are ethically controversial because they typically do not extend life, are very expensive and resource-intensive, and can potentially cause morbidity and mortality due to infections. The first successful composite transplants were hand transplants. Since then, perhaps as many as 10 different structures have been replaced in about 150 patients, with varying functional success rates.
Immunosuppression usually consists of induction therapy (antithymocyte globulin [ATG] or IL-2 receptor blocker), followed by triple maintenance immunosuppression with a corticosteroid, an antiproliferative drug (eg, basiliximab, daclizumab), and a calcineurin inhibitor. Sometimes topical creams containing calcineurin inhibitors or corticosteroids are used.
The first hand transplantation was done in 1998. Since then, double hand and upper-extremity transplantations have been done. Recovery of the hand function varies widely; some recipients regain enough function and sensitivity to do daily activities.
The first face transplantation was done in 2005. As of 2011, 17 such procedures have been done. To date, no graft failure has been reported. Ethical questions about face transplantation are even more prominent than those about extremity transplantation because the surgical procedure is extremely demanding and the immunosuppression required puts the recipient at considerable risk of opportunistic infections.
Skin allografts are used for patients with extensive burns or other conditions causing massive skin loss. Allografts can be used to cover broad denuded areas and thus reduce fluid and protein losses and discourage invasive infection. The allografts are ultimately rejected, but the resulting denuded areas develop well-vascularized granulations onto which autografts from the patient’s healed sites take readily.
Skin cells may be grown in culture, then returned to a burned patient to help cover extensive burns; artificial skin, composed of cultured cells on a synthetic underlayer, may also be used. Split-thickness skin grafts are used to accelerate healing of small wounds. A small piece of skin just a few millimeters thick is harvested, and the donor skin is then laid onto the graft site.
Cartilage transplantation is used for children with congenital nasal or ear defects and adults with severe injuries or joint destruction (eg, severe osteoarthritis). Chondrocytes are more resistant to rejection, possibly because the sparse population of cells in hyaline cartilage is protected from cellular attack by the cartilaginous matrix around them.
Bone transplantation is used for reconstruction of large bony defects (eg, after massive resection of bone cancer). No viable donor bone cells survive in the recipient, but dead matrix from allografts can stimulate recipient osteoblasts to recolonize the matrix and lay down new bone. This matrix acts as scaffolding for bridging and stabilizing defects until new bone is formed.
Cadaveric allografts are preserved by freezing to decrease immunogenicity of the bone (which is dead at the time of implantation) and by glycerolization to maintain chondrocyte viability. No postimplantation immunosuppressive therapy is used. Although patients develop anti-HLA antibodies, early follow-up detects no evidence of cartilage degradation.
Corneal transplantation is Corneal Transplantation.
Adrenal autografting by stereotactically placing medullary tissue within the CNS has been reported to alleviate symptoms in patients with Parkinson disease. Allografts of adrenal tissue, especially from fetal donors, have also been proposed. Fetal ventral mesencephalic tissue stereotactically implanted in the putamen of patients with Parkinson disease has been reported to reduce rigidity and bradykinesia. However, with the ethical and political debates about the propriety of using human fetal tissue, a controlled trial large enough to adequately assess fetal neural transplantation appears unlikely. Xenografts of endocrinologically active cells from porcine donors are being tested.
Fetal thymus implants obtained from stillborn infants may restore immunologic responsiveness in children with thymic aplasia and resulting abnormal development of the lymphoid system. Because the recipient is immunologically unresponsive, immunosuppression is not required; however, severe graft-vs-host disease may occur.
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