Model of Cremaster Muscle Isograft and Allograft Transplant

After transplantation, two patterns of tissue damage can occur during allograft rejection. One is caused by cellmediated or antibody-mediated damage. The second is due to the tissue ischemia and surgical trauma causing microvascular destruction [9]. Since these patterns are dependent on the interactions between the allograft endothelium as well as allograft and recipient immune systems, a quantitative assessment of the microvascular events occurring during allograft rejection is crucial. The cremaster muscle flap was introduced to transplantation studies to serve as a "window" for direct microcirculatory measurements of the hemody-namic events occurring due to ischemia/reperfusion injury and the acute phase of allograft rejection following muscle transplantation. The cremaster tube flap can be transplanted alone as a free flap, or it can be incorporated into the donor's limb as a part of a composite tissue graft. This allows a monitoring sequence and timing of cremaster muscle allograft transplant rejection at the microcirculatory level. Further, the advantages of this cremaster flap preparation include the possibility of comparing differences between hemodynamic and cellular responses among the transplant donor and transplant graft recipient and to investigate the changes occurring within the intra- and extravascular compartments.

1. Technique of the cremaster muscle free flap transplantation model. The cremaster muscle tube flap is designed based on the iliac and femoral vessels, which are transected above the cremaster vascular pedicle take-off. The dissected cremaster muscle free flap is next transplanted to the recipient animal, and the pedicle is anastomosed to the femoral vessels of the recipient. Next a tunnel is created in the medial border of the hind limb, into which the flap is inserted for long-term observations. The transplanted tube flap allograft is then removed from the limb, opened, and spread on the tissue bath for the microcircu-latory observation of allograft acceptance/rejection at the designated times.

2. Technique of the combined hind limb-cremaster muscle transplantation. This model allows study of microcircu-latory response to composite tissue allografts across the MHC barrier. The rat hind limb is dissected together with the cremaster muscle, which is incorporated as a tube flap into the medial border of the limb. Transplantation from donor to recipient involves the four-step procedure. First, the hind limb of the recipient animal is amputated [10], followed by preporation of the hind limb-cremaster graft of the donor animal and preparation of the cremaster muscle tube flap implantation for chronic observations, as outlined in Figure 4. Next, the iliac vessels are exposed, ligated, and transected. The hind limb is then amputated. The hind limb-cremaster composite tissue graft is transplanted into the designated recipient (iso- or allograft), and the cremaster muscle tube graft is dissected and prepared for microcirculatory measurements.

The cremaster flap has proven to be a reliable tool for monitoring microcirculatory hemodynamics during composite tissue graft rejection. At the microcirculatory level the rejection process after allotransplantation begins as early as 24 hours posttransplant. It is characterized by a decrease of capillary perfusion and marked increase in the activation of adherent and transmigrating leukocytes, proceeding clinical the signs of allograft rejection [9, 10]. These observations were significant and added to our understanding of composite tissue allograft rejection as well as allowing us to distinguish between events occurring as a result of the transplantation trauma and rejection phenomenon.

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Essentials of Human Physiology

Essentials of Human Physiology

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